Exelon (EXC) 10-K 13 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2016USD ($)shares
Entity Registrant Name	EXELON CORP
Entity Central Index Key	1,109,357
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Amendment Flag	false
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock Shares Outstanding	926,589,614
Entity Public Float | $	$ 33,527,039,724
Exelon Generation Co L L C [Member]
Entity Registrant Name	EXELON GENERATION CO LLC
Entity Central Index Key	1,168,165
Entity Filer Category	Non-accelerated Filer
Commonwealth Edison Co [Member]
Entity Registrant Name	COMMONWEALTH EDISON CO
Entity Central Index Key	22,606
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	127,017,157
PECO Energy Co [Member]
Entity Registrant Name	PECO ENERGY CO
Entity Central Index Key	78,100
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	170,478,507
Baltimore Gas and Electric Company [Member]
Entity Registrant Name	BALTIMORE GAS AND ELECTRIC
Entity Central Index Key	9,466
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	1,000
Pepco Holdings LLC [Member]
Entity Registrant Name	PEPCO HOLDINGS LLC
Entity Central Index Key	1,135,971
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	252,815,448
Potomac Electric Power Company [Member]
Entity Registrant Name	POTOMAC ELECTRIC POWER CO
Entity Central Index Key	79,732
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	100
Delmarva Power and Light Company [Member]
Entity Registrant Name	DELMARVA POWER & LIGHT CO /DE/
Entity Central Index Key	27,879
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	1,000
Atlantic City Electric Company [Member]
Entity Registrant Name	ATLANTIC CITY ELECTRIC CO
Entity Central Index Key	8,192
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	8,546,017

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Operating revenues [Abstract]
Operating revenues			$ 16,324	$ 18,395		$ 16,637
Rate-regulated utility revenues			15,036	11,052		10,792
Electric operating revenues			13,869	9,876		9,467
Natural gas operating revenues			1,166	1,176		1,325
Operating revenues from affiliates			10	9		23
Total operating revenues			31,360	29,447		27,429
Operating expenses
Competitive businesses purchased power and fuel			8,817	10,007		9,369
Purchased power and fuel			3,823	3,077		3,103
Related Party Transaction, Purchases from Related Party			0	0		531
Purchased power			0	0		531
Operating and maintenance			10,048	8,322		8,568
Depreciation and amortization			3,936	2,450		2,314
Taxes other than income			1,576	1,200		1,154
Total operating expenses			28,200	25,056		25,039
Equity in losses of unconsolidated affiliates			(24)	(7)		0
Gain (Loss) on Disposition of Other Assets			(48)	18		437
Gain on consolidation and acquisition of businesses			0	0		289
Operating Income (Loss)			3,112	4,409		3,096
Other income and (deductions)
Interest Expense			(1,495)	(992)		(1,024)
Interest expense to affiliates			(41)	(41)		(41)
Other, net			413	(46)		455
Total other income and (deductions)			(1,123)	(1,079)		(610)
Income before income taxes			1,989	3,330		2,486
Income before income taxes			1,989	3,330		2,486
Income taxes			761	1,073		666
Net Income (Loss) Attributable to Noncontrolling Interest			70	(19)		197
Net Income			1,204	2,250		1,820
Net income attributable to common shareholders			1,134	2,269		1,623
Pension and non-pension postretirement benefit plans:
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions			0	0		(20)
Prior service benefit reclassified to periodic benefit cost, net of tax			(48)	(46)		(30)
Actuarial loss reclassified to periodic cost, net of tax			184	220		147
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax			181	99		497
Unrealized gain (loss) on cash flow hedges, net of taxes	$ 0		(2)	(9)		148
Unrealized gain (loss) on marketable securities, net of taxes			(4)	(3)		8
Unrealized gain (loss) on foreign currency translation, net of taxes			10	(21)		(9)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax			1	0		1
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease			0	0		(116)
Other comprehensive income (loss)			(36)	60	[1]	(644)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest			1,168	2,310		1,176
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest			70	(19)		197
Comprehensive income			$ 1,098	$ 2,329		$ 979
Average shares of common stock outstanding:
Basic			924	890		860
Diluted			927	893		864
Earnings per average common share:
Basic (in usd per share)			$ 1.23	$ 2.55		$ 1.89
Diluted (in usd per share)			1.22	2.54		1.88
Dividends per common share (in usd per share)			$ 1.264	$ 1.24		$ 1.24
Predecessor [Member]
Operating expenses
Gain (Loss) on Disposition of Other Assets	0					$ 0
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating revenues			$ 16,312	$ 18,386		16,614
Operating revenues from affiliates			1,439	749		779
Total operating revenues			17,751	19,135		17,393
Operating expenses
Purchased power and fuel			8,818	10,007		9,368
Related Party Transaction, Purchases from Related Party			12	14		557
Purchased power			12	14		557
Operating and maintenance			4,978	4,688		4,943
Operating and maintenance from affiliates			663	620		623
Depreciation and amortization			1,879	1,054		967
Taxes other than income			506	489		465
Total operating expenses			16,856	16,872		16,923
Equity in losses of unconsolidated affiliates			0	0		(20)
Gain (Loss) on Disposition of Other Assets			(59)	12		437
Gain on consolidation and acquisition of businesses			0	0		289
Operating Income (Loss)			836	2,275		1,176
Other income and (deductions)
Interest Expense			(325)	(322)		(303)
Interest expense to affiliates			(39)	(43)		(53)
Other, net			401	(60)		406
Total other income and (deductions)			37	(425)		50
Income (Loss) Attributable to Noncontrolling Interest			62	(32)		184
Income before income taxes			873	1,850		1,226
Income taxes			290	502		207
Net Income			558	1,340		1,019
Net income attributable to membership interest			496	1,372		835
Pension and non-pension postretirement benefit plans:
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions			(25)	(8)		0
Unrealized gain (loss) on cash flow hedges, net of taxes			(2)	3		132
Unrealized gain (loss) on marketable securities, net of taxes			(4)	(3)		8
Unrealized gain (loss) on foreign currency translation, net of taxes			10	(21)		(9)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax			1	0		(1)
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease			0	0
Other comprehensive income (loss)			9	(27)	[1]	(250)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest			567	1,313		769
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest			62	(32)		184
Comprehensive income			505	1,345		585
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Electric operating revenues			5,239	4,901		4,560
Operating revenues from affiliates			15	4		4
Total operating revenues			5,254	4,905		4,564
Operating expenses
Related Party Transaction, Purchases from Related Party			47	18		176
Purchased power			1,411	1,301		1,001
Operating and maintenance			1,303	1,372		1,263
Operating and maintenance from affiliates			227	195		166
Depreciation and amortization			775	707		687
Taxes other than income			293	296		293
Total operating expenses			4,056	3,889		3,586
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			7	1		2
Operating Income (Loss)			1,205	1,017		980
Other income and (deductions)
Interest Expense			(448)	(319)		(308)
Interest expense to affiliates			(13)	(13)		(13)
Other, net			(65)	21		17
Total other income and (deductions)			(526)	(311)		(304)
Income before income taxes			679	706		676
Income taxes			301	280		268
Net Income			378	426		408
Pension and non-pension postretirement benefit plans:
Comprehensive income			378	426		408
PECO Energy Co [Member]
Operating revenues [Abstract]
Electric operating revenues			2,524	2,485		2,446
Natural gas operating revenues			462	545		646
Operating revenues from affiliates			8	2		2
Total operating revenues			2,994	3,032		3,094
Operating expenses
Related Party Transaction, Purchases from Related Party			287	220		194
Purchased power			598	735		740
Purchased fuel			162	235		327
Operating and maintenance			665	684		767
Operating and maintenance from affiliates			146	110		99
Depreciation and amortization			270	260		236
Taxes other than income			164	160		159
Total operating expenses			2,292	2,404		2,522
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			0	2		0
Operating Income (Loss)			702	630		572
Other income and (deductions)
Interest Expense			(111)	(102)		(101)
Interest expense to affiliates			(12)	(12)		(12)
Other, net			8	5		7
Total other income and (deductions)			(115)	(109)		(106)
Income before income taxes			587	521		466
Income taxes			149	143		114
Net Income			438	378		352
Net income attributable to common shareholders			438	378		352
Pension and non-pension postretirement benefit plans:
Comprehensive income			438	378		352
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues			2,603	2,490		2,460
Natural gas operating revenues			609	631		680
Operating revenues from affiliates			21	14		25
Total operating revenues			3,233	3,135		3,165
Operating expenses
Related Party Transaction, Purchases from Related Party			604	498		382
Purchased power			528	602		733
Purchased fuel			162	205		302
Operating and maintenance			605	565		614
Operating and maintenance from affiliates			132	118		103
Depreciation and amortization			423	366		371
Taxes other than income			229	224		221
Total operating expenses			2,683	2,578		2,726
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			0	1		0
Operating Income (Loss)			550	558		439
Other income and (deductions)
Interest Expense			(87)	(83)		(90)
Interest expense to affiliates			(16)	(16)		(16)
Other, net			21	18		18
Total other income and (deductions)			(82)	(81)		(88)
Income before income taxes			468	477		351
Income taxes			174	189		140
Net Income			294	288		211
Dividends, Preferred Stock			8	13		13
Net income attributable to common shareholders			286	275		198
Pension and non-pension postretirement benefit plans:
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest			294	288		211
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest			8	13		13
Comprehensive income			286	275		198
Pepco Holdings LLC [Member]
Operating expenses
Related Party Transaction, Purchases from Related Party	0			0		0
Pepco Holdings LLC [Member] | Predecessor [Member]
Operating revenues [Abstract]
Electric operating revenues	1,096			4,770		4,614
Natural gas operating revenues	57			165		194
Operating revenues from affiliates	0			0		0
Total operating revenues	1,153			4,935		4,808
Operating expenses
Purchased power	471			1,986		1,940
Purchased fuel	26			87		117
Operating and maintenance	294			1,156		1,183
Operating and maintenance from affiliates	0			0		0
Depreciation and amortization	152			624		526
Taxes other than income	105			455		437
Total operating expenses	1,048			4,308		4,203
Equity in losses of unconsolidated affiliates	0			0
Gain (Loss) on Disposition of Other Assets				46
Operating Income (Loss)	105			673		605
Other income and (deductions)
Interest Expense	(65)			(280)		(269)
Other, net	(4)			88		44
Total other income and (deductions)	(69)			(192)		(225)
Income before income taxes	36			481		380
Income taxes	17			163		138
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest	0			9		0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	19			318		242
Net Income	19			327		242
Net income attributable to membership interest	19			327		242
Pension and non-pension postretirement benefit plans:
Actuarial loss reclassified to periodic cost, net of tax	1			9		(12)
Unrealized gain (loss) on cash flow hedges, net of taxes				(1)		0
Other comprehensive income (loss)	1			10	[1]	(12)
Comprehensive income	20			337		230
Pepco Holdings LLC [Member] | Successor [Member]
Operating revenues [Abstract]
Electric operating revenues		$ 3,506
Natural gas operating revenues		92
Operating revenues from affiliates		45
Total operating revenues		3,643
Operating expenses
Related Party Transaction, Purchases from Related Party		486
Purchased power		925
Purchased fuel		36
Operating and maintenance		1,144
Operating and maintenance from affiliates		89
Depreciation and amortization		515
Taxes other than income		354
Total operating expenses		3,549
Equity in losses of unconsolidated affiliates		0
Gain (Loss) on Disposition of Other Assets		(1)
Operating Income (Loss)		93
Other income and (deductions)
Interest Expense		(195)
Other, net		44
Total other income and (deductions)		(151)
Income before income taxes		(58)
Income taxes		3
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Noncontrolling Interest	$ 0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest		(61)
Net Income (Loss) Attributable to Noncontrolling Interest		(61)
Net Income		(61)
Net income attributable to membership interest		(61)
Pension and non-pension postretirement benefit plans:
Actuarial loss reclassified to periodic cost, net of tax		0
Unrealized gain (loss) on cash flow hedges, net of taxes		0
Other comprehensive income (loss)		0
Comprehensive income		$ (61)
Delmarva Power and Light Company [Member]
Operating revenues [Abstract]
Electric operating revenues			1,122	1,132		1,081
Natural gas operating revenues			148	164		194
Operating revenues from affiliates			7	6		7
Total operating revenues			1,277	1,302		1,282
Operating expenses
Related Party Transaction, Purchases from Related Party			154	0		0
Purchased power			369	555		536
Purchased fuel			60	79		104
Operating and maintenance			422	303		266
Operating and maintenance from affiliates			19	1		1
Depreciation and amortization			157	148		122
Taxes other than income			55	51		46
Total operating expenses			1,236	1,137		1,075
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			9	0		0
Operating Income (Loss)			50	165		207
Other income and (deductions)
Interest Expense			(50)	(50)		(48)
Other, net			13	10		10
Total other income and (deductions)			(37)	(40)		(38)
Income before income taxes			13	125		169
Income taxes			22	49		65
Net Income			(9)	76		104
Net income attributable to common shareholders			(9)	76		104
Pension and non-pension postretirement benefit plans:
Comprehensive income			(9)	76		104
Potomac Electric Power Company [Member]
Operating revenues [Abstract]
Electric operating revenues			2,181	2,124		2,050
Operating revenues from affiliates			5	5		5
Total operating revenues			2,186	2,129		2,055
Operating expenses
Related Party Transaction, Purchases from Related Party			295	0		0
Purchased power			411	719		735
Operating and maintenance			607	435		386
Operating and maintenance from affiliates			35	4		4
Depreciation and amortization			295	256		212
Taxes other than income			377	376		369
Total operating expenses			2,020	1,790		1,706
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			8	46		0
Operating Income (Loss)			174	385		349
Other income and (deductions)
Interest Expense			(127)	(124)		(115)
Other, net			36	28		30
Total other income and (deductions)			(91)	(96)		(85)
Income before income taxes			83	289		264
Income taxes			41	102		93
Net Income			42	187		171
Net income attributable to common shareholders			42	187		171
Pension and non-pension postretirement benefit plans:
Comprehensive income			42	187		171
Atlantic City Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues			1,254	1,291		1,206
Operating revenues from affiliates			3	4		4
Total operating revenues			1,257	1,295		1,210
Operating expenses
Purchased power			614	708		664
Cost Of Goods And Services Energy Commodities And Services From Affiliate			37	0		0
Operating and maintenance			410	268		247
Operating and maintenance from affiliates			18	3		3
Depreciation and amortization			165	175		155
Taxes other than income			7	7		4
Total operating expenses			1,251	1,161		1,073
Equity in losses of unconsolidated affiliates			0	0
Gain (Loss) on Disposition of Other Assets			1	0		0
Operating Income (Loss)			7	134		137
Other income and (deductions)
Interest Expense			(62)	(64)		(64)
Other, net			9	3		3
Total other income and (deductions)			(53)	(61)		(61)
Income before income taxes			(46)	73		76
Income taxes			(4)	33		30
Net Income			(42)	40		46
Net income attributable to common shareholders			(42)	40		46
Pension and non-pension postretirement benefit plans:
Comprehensive income			$ (42)	$ 40		$ 46
[1]	All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net income	$ 1,204	$ 2,250	$ 1,820
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	5,576	3,987	3,868
Impairments of long-lived assets	306	36	687
Gain on consolidation and acquisition of businesses	0	0	(296)
(Gain) Loss on sales of assets	48	(18)	(437)
Deferred income taxes and amortization of investment tax credits	664	752	502
Net fair value changes related to derivatives	24	(367)	716
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(229)	131	(210)
Other non-cash operating activities	1,333	1,109	1,054
Changes in assets and liabilities:
Accounts receivable	(432)	240	(318)
Inventories	7	4	(380)
Accounts payable and accrued expenses	771	(121)	49
Increase (Decrease) in Premiums Receivable	66	(58)	(38)
Increase (Decrease) Cash Collateral from Counterparties	931	347	(1,719)
Income taxes	576	97	(143)
Pension and non-pension postretirement benefit contributions	(397)	(502)	(617)
Increase (Decrease) in Prepaid Taxes	(1,250)	0	0
Other assets and liabilities	(621)	(387)	(157)
Net cash flows provided by operating activities	8,445	7,616	4,457
Cash flows from investing activities
Capital expenditures	(8,553)	(7,624)	(6,077)
Proceeds from Sale and Collection of Lease Receivables	360	0	335
Proceeds from nuclear decommissioning trust fund sales	9,496	6,895	7,396
Investment in nuclear decommissioning trust funds	(9,738)	(7,147)	(7,551)
Acquisitions of businesses, net	(6,934)	(40)	(386)
Proceeds from sales of long-lived assets	61	147	1,719
Proceeds from sales of investments	0	0	7
Cash and restricted cash acquired from consolidations and acquisitions	0	0	140
Purchases of investments	0	0	(3)
Change in restricted cash	(42)	66	(104)
Distribution from CENG	0	0	13
Other investing activities	(153)	(119)	(88)
Net cash flows used in investing activities	(15,503)	(7,822)	(4,599)
Cash flows from financing activities
Repayments of Debt, Maturing in More than Three Months	(462)	0	0
Issuance of long-term debt	4,716	6,709	3,463
Retirement of long-term debt	(1,936)	(2,687)	(1,545)
Redemption of preference stock	(190)	0	0
Distribution to noncontrolling interest of consolidated VIE	0	0	(421)
Dividends paid on common stock	(1,166)	(1,105)	(1,065)
Proceeds from employee stock plans	(55)	(32)	(35)
Other financing activities	(85)	(99)	(178)
Proceeds from Noncontrolling Interests	372	32	0
Proceeds from (Repayments of) Short-term Debt	(353)	80	122
Proceeds from Issuance of Common Stock	0	1,868	0
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	240	0	0
Net cash flows provided by financing activities	1,191	4,830	411
(Decrease) Increase in cash and cash equivalents	(5,867)	4,624	269
Cash and cash equivalents at beginning of period	6,502	1,878	1,609
Cash and cash equivalents at end of period	635	6,502	1,878
Predecessor [Member]
Adjustments to reconcile net income to net cash flows provided by operating activities:
Impairments of long-lived assets		0
(Gain) Loss on sales of assets			0
Parent Company [Member]
Cash flows from operating activities
Net income	1,134	2,269	1,623
Adjustments to reconcile net income to net cash flows provided by operating activities:
Increase (Decrease) Due from Affiliates	1,390	(1,217)	(83)
Changes in assets and liabilities:
Net cash flows provided by operating activities	1,029	3,071	806
Cash flows from investing activities
Capital expenditures	0	0	1
Payments to Acquire Businesses, Net of Cash Acquired	6,962
Proceeds from Sale and Collection of Lease Receivables	0	0	335
Other investing activities	5	(55)	(126)
Net cash flows used in investing activities	(7,324)	(934)	57
Cash flows from financing activities
Issuance of long-term debt	1,800	4,200	1,150
Retirement of long-term debt	(46)	(2,263)	(23)
Dividends paid on common stock	(1,166)	(1,105)	(1,065)
Proceeds from employee stock plans	(55)	(32)	(35)
Other financing activities	(20)	(58)	(84)
Contribution from member	1,912	3,209	1,370
Proceeds from Issuance of Common Stock	0	1,868	0
Net cash flows provided by financing activities	623	2,674	13
(Decrease) Increase in cash and cash equivalents	(5,672)	4,811	876
Cash and cash equivalents at beginning of period	5,690	879	3
Cash and cash equivalents at end of period	18	5,690	879
Increase (Decrease) Due from Affiliates	1,390	(1,217)	(83)
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	558	1,340	1,019
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	3,519	2,589	2,519
Impairments of long-lived assets	243	12	663
Gain on consolidation and acquisition of businesses	0	0	(296)
(Gain) Loss on sales of assets	59	(12)	(437)
Deferred income taxes and amortization of investment tax credits	(269)	49	(198)
Net fair value changes related to derivatives	40	(249)	635
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(229)	131	(210)
Other non-cash operating activities	15	268	346
Increase (Decrease) Due from Affiliates	0	0	44
Changes in assets and liabilities:
Accounts receivable	(152)	194	(215)
Receivables from and payables to affiliates, net	(21)	15	15
Inventories	(4)	16	(359)
Accounts payable and accrued expenses	29	(149)	29
Increase (Decrease) in Premiums Receivable	66	(58)	(38)
Increase (Decrease) Cash Collateral from Counterparties	923	407	(1,748)
Income taxes	182	(18)	265
Pension and non-pension postretirement benefit contributions	(152)	(245)	(297)
Other assets and liabilities	(231)	(207)	57
Net cash flows provided by operating activities	4,444	4,199	1,826
Cash flows from investing activities
Capital expenditures	(3,078)	(3,841)	(3,012)
Proceeds from nuclear decommissioning trust fund sales	9,496	6,895	7,396
Investment in nuclear decommissioning trust funds	(9,738)	(7,147)	(7,551)
Acquisitions of businesses, net	(293)	(40)	(386)
Proceeds from sales of long-lived assets	37	147	1,719
Cash and restricted cash acquired from consolidations and acquisitions	0	0	140
Change in restricted cash	(35)	35	(87)
Distribution from CENG	0	0	13
Other investing activities	(240)	(118)	(43)
Net cash flows used in investing activities	(3,851)	(4,069)	(1,767)
Cash flows from financing activities
Repayments of Debt, Maturing in More than Three Months	(162)	0	0
Issuance of long-term debt	388	1,309	1,112
Retirement of long-term debt	(202)	(89)	(586)
Repayments of Related Party Debt	0	(550)	0
Increase (Decrease) in Due to Affiliates	(1,191)	1,252	0
Distribution to noncontrolling interest of consolidated VIE	0	0	(421)
Other financing activities	(19)	(6)	(67)
Distribution to member	(922)	(2,474)	(645)
Contribution from member	142	47	53
Proceeds from Noncontrolling Interests	372	32	0
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	620	0	17
Proceeds from Debt, Maturing in More than Three Months	240	0	0
Net cash flows provided by financing activities	(734)	(479)	(537)
(Decrease) Increase in cash and cash equivalents	(141)	(349)	(478)
Cash and cash equivalents at beginning of period	431	780	1,258
Cash and cash equivalents at end of period	290	431	780
Increase (Decrease) Due from Affiliates	0	0	44
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	378	426	408
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	775	707	687
Deferred income taxes and amortization of investment tax credits	439	353	433
Other non-cash operating activities	215	416	255
Changes in assets and liabilities:
Accounts receivable	(25)	(93)	(121)
Receivables from and payables to affiliates, net	3	(19)	(11)
Inventories	1	(40)	(16)
Accounts payable and accrued expenses	339	68	95
Increase (Decrease) Cash Collateral from Counterparties	7	(33)	2
Income taxes	306	192	(159)
Pension and non-pension postretirement benefit contributions	(38)	(150)	(248)
Other assets and liabilities	105	69	1
Net cash flows provided by operating activities	2,505	1,896	1,326
Cash flows from investing activities
Capital expenditures	(2,734)	(2,398)	(1,689)
Proceeds from sales of investments	0	0	7
Purchases of investments	0	0	(3)
Change in restricted cash	0	2	(2)
Other investing activities	49	34	32
Net cash flows used in investing activities	(2,685)	(2,362)	(1,655)
Cash flows from financing activities
Issuance of long-term debt	1,200	850	900
Retirement of long-term debt	(665)	(260)	(617)
Dividends paid on common stock	(369)	(299)	(307)
Other financing activities	(18)	(16)	(10)
Contributions from parent	315	202	273
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	(294)	(10)	120
Net cash flows provided by financing activities	169	467	359
(Decrease) Increase in cash and cash equivalents	(11)	1	30
Cash and cash equivalents at beginning of period	67	66	36
Cash and cash equivalents at end of period	56	67	66
PECO Energy Co [Member]
Cash flows from operating activities
Net income	438	378	352
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	270	260	236
Deferred income taxes and amortization of investment tax credits	78	90	88
Other non-cash operating activities	65	70	92
Increase (Decrease) Due from Affiliates	(131)	0	0
Changes in assets and liabilities:
Accounts receivable	(71)	37	(16)
Receivables from and payables to affiliates, net	6	3	(6)
Inventories	6	10	2
Accounts payable and accrued expenses	67	(25)	58
Income taxes	8	(9)	(57)
Pension and non-pension postretirement benefit contributions	(30)	(40)	(16)
Other assets and liabilities	(8)	(4)	(21)
Net cash flows provided by operating activities	829	770	712
Cash flows from investing activities
Capital expenditures	(686)	(601)	(661)
Change in restricted cash	(1)	(1)	0
Other investing activities	20	14	12
Net cash flows used in investing activities	(798)	(588)	(649)
Cash flows from financing activities
Issuance of long-term debt	300	350	300
Retirement of long-term debt	(300)	0	(250)
Dividends paid on common stock	(277)	(279)	(320)
Other financing activities	(4)	(4)	(4)
Contributions from parent	18	16	24
Net cash flows provided by financing activities	(263)	83	(250)
(Decrease) Increase in cash and cash equivalents	(232)	265	(187)
Cash and cash equivalents at beginning of period	295	30	217
Cash and cash equivalents at end of period	63	295	30
Increase (Decrease) Due from Affiliates	(131)	0	0
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	294	288	211
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	423	366	371
Impairments of long-lived assets	52	0	0
Deferred income taxes and amortization of investment tax credits	118	165	116
Other non-cash operating activities	88	137	180
Changes in assets and liabilities:
Accounts receivable	(98)	84	46
Receivables from and payables to affiliates, net	3	(2)	(1)
Inventories	1	18	(6)
Accounts payable and accrued expenses	138	(3)	(75)
Increase (Decrease) Cash Collateral from Counterparties	0	(27)	27
Income taxes	18	(54)	45
Pension and non-pension postretirement benefit contributions	(49)	(17)	(16)
Other assets and liabilities	(43)	(173)	(158)
Net cash flows provided by operating activities	945	782	740
Cash flows from investing activities
Capital expenditures	(934)	(719)	(620)
Change in restricted cash	0	26	(22)
Other investing activities	24	18	20
Net cash flows used in investing activities	(910)	(675)	(622)
Cash flows from financing activities
Issuance of long-term debt	850	0	0
Retirement of long-term debt	(379)	(75)	(70)
Redemption of preference stock	(190)	0	0
Preferred Stock, Redemption Amount	190
Dividends paid on common stock	(179)	(158)	0
Other financing activities	(11)	(13)	13
Contributions from parent	61	7	0
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	(165)	90	(15)
Dividends paid on preferred securities	(8)	(13)	(13)
Net cash flows provided by financing activities	(21)	(162)	(85)
(Decrease) Increase in cash and cash equivalents	14	(55)	33
Cash and cash equivalents at beginning of period	9	64	31
Cash and cash equivalents at end of period	23	9	64
Pepco Holdings LLC [Member] | Predecessor [Member]
Cash flows from operating activities
Net income		327	242
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest		(9)	0
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization		624	526
Impairments of long-lived assets			81
(Gain) Loss on sales of assets		(46)
Deferred income taxes and amortization of investment tax credits		134	303
Net fair value changes related to derivatives		0	0
Other non-cash operating activities		167	127
Changes in assets and liabilities:
Accounts receivable		(105)	(2)
Receivables from and payables to affiliates, net		0	0
Inventories		0	8
Accounts payable and accrued expenses		(41)	(31)
Increase (Decrease) Cash Collateral from Counterparties		0	1
Income taxes		8	(197)
Pension and non-pension postretirement benefit contributions		(21)	(18)
Other assets and liabilities		(99)	(186)
Net cash flows provided by operating activities		939	854
Cash flows from investing activities
Capital expenditures		(1,230)	(1,223)
Proceeds from sales of long-lived assets		54	0
Purchases of investments		0	0
Change in restricted cash		6	(12)
Other investing activities		9	9
Net cash flows used in investing activities		(1,161)	(1,226)
Cash flows from financing activities
Repayments of Debt, Maturing in More than Three Months		0	0
Issuance of long-term debt		558	766
Retirement of long-term debt		(430)	(462)
Increase (Decrease) in Due to Affiliates		0	0
Dividends paid on common stock		(275)	(272)
Proceeds from employee stock plans		(18)	(33)
Other financing activities		(26)	(11)
Distribution to member		0	0
Proceeds from (Repayments of) Short-term Debt		34	183
Proceeds from Issuance of Preferred Stock and Preference Stock		54	126
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less		300	0
Net cash flows provided by financing activities		233	363
(Decrease) Increase in cash and cash equivalents		11	(9)
Cash and cash equivalents at beginning of period	26	15	24
Cash and cash equivalents at end of period		26	15
Proceeds from Issuance of Preferred Stock and Preference Stock		54	126
Pepco Holdings LLC [Member] | Successor [Member]
Cash flows from financing activities
Cash and cash equivalents at end of period	170
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income	42	187	171
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	295	256	212
(Gain) Loss on sales of assets	(8)	(46)	0
Deferred income taxes and amortization of investment tax credits	153	150	175
Other non-cash operating activities	183	54	37
Changes in assets and liabilities:
Accounts receivable	(41)	(43)	7
Receivables from and payables to affiliates, net	44	0	(2)
Inventories	1	(5)	5
Accounts payable and accrued expenses	32	(21)	(37)
Income taxes	110	(46)	(14)
Pension and non-pension postretirement benefit contributions	(32)	(14)	(11)
Other assets and liabilities	(128)	(99)	(157)
Net cash flows provided by operating activities	651	373	386
Cash flows from investing activities
Capital expenditures	(586)	(544)	(567)
Acquisitions of businesses, net	(33)
Proceeds from sales of long-lived assets	12	54	9
Purchases of investments	(30)	0	0
Change in restricted cash	(31)	3	(3)
Other investing activities	(12)	10	1
Net cash flows used in investing activities	(647)	(477)	(560)
Cash flows from financing activities
Issuance of long-term debt	4	208	412
Retirement of long-term debt	(11)	(22)	(184)
Dividends paid on common stock	(136)	(146)	(86)
Other financing activities	(3)	(9)	(4)
Contributions from parent	187	112	80
Proceeds from (Repayments of) Short-term Debt	(41)	(40)	(47)
Net cash flows provided by financing activities	0	103	171
(Decrease) Increase in cash and cash equivalents	4	(1)	(3)
Cash and cash equivalents at beginning of period	5	6	9
Cash and cash equivalents at end of period	9	5	6
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	(9)	76	104
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	157	148	122
Deferred income taxes and amortization of investment tax credits	109	73	110
Other non-cash operating activities	114	33	22
Changes in assets and liabilities:
Accounts receivable	(5)	(24)	1
Receivables from and payables to affiliates, net	13	3	(6)
Inventories	0	6	(2)
Accounts payable and accrued expenses	(4)	(8)	0
Increase (Decrease) Cash Collateral from Counterparties	1	(1)	0
Income taxes	28	(26)	(1)
Pension and non-pension postretirement benefit contributions	(22)	0	0
Other assets and liabilities	(72)	(14)	(82)
Net cash flows provided by operating activities	310	266	268
Cash flows from investing activities
Capital expenditures	(349)	(352)	(352)
Proceeds from sales of long-lived assets	9	0	0
Change in restricted cash	0	5	(5)
Other investing activities	4	2	(1)
Net cash flows used in investing activities	(336)	(345)	(358)
Cash flows from financing activities
Issuance of long-term debt	175	200	204
Retirement of long-term debt	(100)	(100)	(100)
Dividends paid on common stock	(54)	(92)	(100)
Other financing activities	(1)	(2)	(1)
Contributions from parent	152	75	130
Proceeds from (Repayments of) Short-term Debt	(105)	(1)	(41)
Net cash flows provided by financing activities	67	80	92
(Decrease) Increase in cash and cash equivalents	41	1	2
Cash and cash equivalents at beginning of period	5	4	2
Cash and cash equivalents at end of period	46	5	4
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	(42)	40	46
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	165	175	155
Deferred income taxes and amortization of investment tax credits	22	31	38
Other non-cash operating activities	155	37	26
Changes in assets and liabilities:
Accounts receivable	(8)	(67)	6
Receivables from and payables to affiliates, net	13	1	0
Inventories	(1)	(1)	4
Accounts payable and accrued expenses	9	9	(17)
Income taxes	174	(34)	(20)
Pension and non-pension postretirement benefit contributions	(17)	(2)	(3)
Other assets and liabilities	(85)	67	24
Net cash flows provided by operating activities	385	256	259
Cash flows from investing activities
Capital expenditures	(311)	(300)	(225)
Proceeds from sales of long-lived assets	2	0	0
Change in restricted cash	(2)	(6)	0
Other investing activities	2	0	1
Net cash flows used in investing activities	(309)	(306)	(224)
Cash flows from financing activities
Repayments of Debt, Maturing in More than Three Months			(100)
Issuance of long-term debt	0	150	150
Retirement of long-term debt	(48)	(58)	(66)
Dividends paid on common stock	(63)	(12)	(26)
Other financing activities	(1)	(2)	(1)
Contributions from parent	139	95	0
Proceeds from (Repayments of) Short-term Debt	(5)	(122)	7
Net cash flows provided by financing activities	22	51	(36)
(Decrease) Increase in cash and cash equivalents	98	1	(1)
Cash and cash equivalents at beginning of period	3	2	3
Cash and cash equivalents at end of period	$ 101	$ 3	$ 2

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Dec. 31, 2016	Mar. 24, 2016		Dec. 31, 2015
Current assets
Cash and cash equivalents		$ 635			$ 6,502
Restricted cash and cash equivalents		253			205
Accounts receivable, net
Customer		4,158			3,187
Other		1,201			912
Mark-to-market derivative assets		917			1,365
Energy Marketing Contracts Assets, Current		88			86
Inventories, net
Fossil fuel		364			462
Materials and supplies		1,274			1,104
Prepaid utility taxes		1,250			0
Regulatory assets		1,342			759
Other		930			752
Total current assets		12,412			15,334
Property, plant and equipment, net		71,555			57,439
Deferred debits and other assets
Regulatory assets		10,046			6,065
Nuclear decommissioning trust funds		11,061			10,342
Investments		629			639
Goodwill		6,677			2,672
Mark-to-market derivative assets		492			758
Unamortized energy contract assets		447			484
Pledged assets for Zion Station decommissioning		113			206
Other		1,472			1,445
Deferred Costs and Other Assets		30,937			22,611
Total assets (a)	[1]	114,904			95,384
Current liabilities
Short-term borrowings		1,267			533
Long-term debt due within one year		2,430			1,500
Accounts payable		3,441			2,883
Accrued expenses		3,460			2,376
Payables to affiliates		706			0
Accounts Payable, Related Parties, Current		8			8
Mark-to-market derivative liabilities		282			205
Unamortized energy contract liabilities		407			100
Energy Marketing Accounts Payable		428			302
Payables to Customers		151			0
Regulatory liabilities		602			369
Other		981			842
Total current liabilities		13,457			9,118
Long-term debt		31,575			23,645
Long-term debt to financing trusts		641			641
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		18,138			13,776
Asset retirement obligations		9,111			8,585
Pension obligations		4,248			3,385
Non-pension postretirement benefit obligations		1,848			1,618
Spent nuclear fuel obligation		1,024			1,021
Regulatory liabilities		4,187			4,201
Mark-to-market derivative liabilities		392			374
Unamortized energy contract liabilities		830			117
Payable for Zion Station decommissioning		14			90
Other		1,827			1,491
Total deferred credits and other liabilities		41,619			34,658
Total liabilities	[1]	87,292			68,062
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount		0			28
Preferred stock(b)		0			193
Shareholders’ equity
Common stock		18,794			18,676
Treasury stock, at cost (35 shares at December 31, 2016 and 2015, respectively)		(2,327)			(2,327)
Accumulated other comprehensive loss, net		(2,660)			(2,624)
Total shareholders’ equity		25,837			25,793
BGE preference stock not subject to mandatory redemption		0			193
Noncontrolling interests		1,775			1,308
Total equity		27,612			27,294
Member’s equity
Retained earnings		12,030			12,068
Accumulated other comprehensive loss, net		(2,660)			(2,624)
Liabilities and Equity		114,904			95,384
Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets (a)		8,893			8,268
Deferred credits and other liabilities
Total liabilities		3,356			3,264
Delmarva Power and Light Company [Member]
Current assets
Cash and cash equivalents		46			5
Accounts receivable, net
Customer		136			154
Other		63			96
Inventories, net
Fossil fuel		7			8
Materials and supplies		32			32
Regulatory assets		59			72
Other		24			21
Receivables from affiliates		3			0
Total current assets		370			388
Property, plant and equipment, net		3,273			3,070
Deferred debits and other assets
Regulatory assets		289			299
Investments		0			0
Goodwill		8			8
Prepaid pension asset		206			202
Other		7			2
Deferred Costs and Other Assets		510			511
Total assets (a)		4,153			3,969
Current liabilities
Short-term borrowings		0			105
Long-term debt due within one year		119			204
Accounts payable		88			109
Accrued expenses		36			31
Accounts Payable, Related Parties, Current		38			20
Customer deposits		36			31
Payables to Customers		13			0
Regulatory liabilities		43			49
Other		8			15
Total current liabilities		381			564
Long-term debt		1,221			1,061
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		1,056			945
Non-pension postretirement benefit obligations		19			19
Regulatory liabilities		97			111
Other		53			32
Total deferred credits and other liabilities		1,225			1,107
Total liabilities		2,827			2,732
Shareholders’ equity
Common stock		764			612
Total shareholders’ equity		1,326			1,237
Liabilities And Stockholders Equity Including Portion Attributable To Noncontrolling Interest		4,153			3,969
Member’s equity
Retained earnings		562			625
Commonwealth Edison Co [Member]
Current assets
Cash and cash equivalents		56			67
Restricted cash and cash equivalents		2			2
Accounts receivable, net
Customer		528			533
Other		218			272
Inventories, net
Inventories, net		159			164
Regulatory assets		190			218
Other		45			63
Receivables from affiliates		356			199
Total current assets		1,554			1,518
Property, plant and equipment, net		19,335			17,502
Deferred debits and other assets
Regulatory assets		977			895
Investments		6			6
Goodwill		2,625			2,625
Receivable from affiliates		2,170			2,172
Prepaid pension asset		1,343			1,490
Other		325			324
Deferred Costs and Other Assets		7,446			7,512
Total assets (a)		28,335			26,532
Current liabilities
Short-term borrowings		0			294
Long-term debt due within one year		425			665
Accounts payable		645			660
Accrued expenses		1,250			706
Accounts Payable, Related Parties, Current		65			62
Mark-to-market derivative liabilities		19			23
Customer deposits		121			131
Regulatory liabilities		329			155
Other		84			70
Total current liabilities		2,938			2,766
Long-term debt		6,608			5,844
Long-term debt to financing trusts		205			205
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		5,364			4,914
Asset retirement obligations		119			111
Non-pension postretirement benefit obligations		239			259
Regulatory liabilities		3,369			3,459
Mark-to-market derivative liabilities		(239)			224
Other		529			507
Total deferred credits and other liabilities		9,859			9,474
Total liabilities		19,610			18,289
Shareholders’ equity
Common stock		1,588			1,588
Other paid-in capital		6,150			5,677
Total shareholders’ equity		8,725			8,243
Member’s equity
Liabilities and Equity		28,335			26,532
Retained Earnings, Unappropriated		(1,639)			(1,639)
Retained Earnings, Appropriated		2,626			2,617
Exelon Generation Co L L C [Member]
Current assets
Cash and cash equivalents		290			431
Restricted cash and cash equivalents		158			123
Accounts receivable, net
Customer		2,433			2,095
Other		558			360
Mark-to-market derivative assets		917			1,365
Energy Marketing Contracts Assets, Current		88			86
Inventories, net
Fossil fuel		292			384
Materials and supplies		935			880
Other		701			535
Receivables from affiliates		156			83
Total current assets		6,528			6,342
Property, plant and equipment, net		25,585			25,843
Deferred debits and other assets
Nuclear decommissioning trust funds		11,061			10,342
Investments		418			210
Goodwill		47			47
Mark-to-market derivative assets		476			733
Prepaid pension asset		1,595			1,689
Unamortized energy contract assets		447			484
Deferred income taxes		16			6
Pledged assets for Zion Station decommissioning		113			206
Other		688			627
Deferred Costs and Other Assets		14,861			14,344
Total assets (a)	[2]	46,974			46,529
Current liabilities
Short-term borrowings		699			29
Long-term debt due within one year		1,117			90
Accounts payable		1,610			1,583
Accrued expenses		989			935
Accounts Payable, Related Parties, Current		137			104
Mark-to-market derivative liabilities		263			182
Unamortized energy contract liabilities		72			100
Energy Marketing Accounts Payable		428			302
Other		313			356
Notes Payable, Related Parties, Current		55			1,252
Total current liabilities		5,683			4,933
Long-term debt		7,202			7,936
Long-term debt to financing trusts		922			933
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		5,585			5,845
Asset retirement obligations		8,922			8,431
Non-pension postretirement benefit obligations		930			924
Spent nuclear fuel obligation		1,024			1,021
Mark-to-market derivative liabilities		153			150
Unamortized energy contract liabilities		80			117
Payable for Zion Station decommissioning		14			90
Other		595			602
Due to Affiliate, Noncurrent		2,608			2,577
Total deferred credits and other liabilities		19,911			19,757
Total liabilities	[2]	33,718			33,559
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount		0			28
Shareholders’ equity
Accumulated other comprehensive loss, net		(54)			(63)
Member’s equity
Membership interest/Common stock(c)		9,261			8,997
Retained earnings		2,275			2,701
Accumulated other comprehensive loss, net		(54)			(63)
Total member’s equity		11,482			11,635
Noncontrolling interests		1,774			1,307
Total equity		13,256			12,942
Liabilities and Equity		46,974			46,529
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets (a)		8,817			8,235
Deferred credits and other liabilities
Total liabilities		3,170			3,135
PECO Energy Co [Member]
Current assets
Cash and cash equivalents		63			295
Restricted cash and cash equivalents		4			3
Accounts receivable, net
Customer		306			258
Other		131			146
Inventories, net
Fossil fuel		35			43
Materials and supplies		27			26
Prepaid utility taxes		9			11
Regulatory assets		29			34
Other		18			24
Due from Affiliates		131			0
Receivables from affiliates		4			2
Total current assets		757			842
Property, plant and equipment, net		7,565			7,141
Deferred debits and other assets
Regulatory assets		1,681			1,583
Investments		25			28
Receivable from affiliates		438			405
Prepaid pension asset		345			347
Other		20			21
Deferred Costs and Other Assets		2,509			2,384
Total assets (a)		10,831			10,367
Current liabilities
Long-term debt due within one year		0			300
Accounts payable		342			281
Accrued expenses		104			109
Accounts Payable, Related Parties, Current		63			55
Customer deposits		61			58
Regulatory liabilities		127			112
Other		30			29
Total current liabilities		727			944
Long-term debt		2,580			2,280
Long-term debt to financing trusts		184			184
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		3,006			2,792
Asset retirement obligations		28			27
Non-pension postretirement benefit obligations		289			287
Regulatory liabilities		517			527
Other		85			90
Total deferred credits and other liabilities		3,925			3,723
Total liabilities		7,416			7,131
Shareholders’ equity
Common stock		2,473			2,455
Accumulated other comprehensive loss, net		1			1
Total shareholders’ equity		3,415			3,236
Member’s equity
Retained earnings		941			780
Accumulated other comprehensive loss, net		1			1
Liabilities and Equity		10,831			10,367
Baltimore Gas and Electric Company [Member]
Current assets
Cash and cash equivalents		23			9
Restricted cash and cash equivalents		24			24
Accounts receivable, net
Customer		395			300
Other		102			112
Inventories, net
Fossil fuel		30			36
Materials and supplies		38			33
Prepaid utility taxes		15			61
Regulatory assets		208			267
Other		7			3
Total current assets		842			845
Property, plant and equipment, net		7,040			6,597
Deferred debits and other assets
Regulatory assets		504			514
Investments		12			12
Prepaid pension asset		297			319
Other		9			8
Deferred Costs and Other Assets		822			853
Total assets (a)	[3]	8,704			8,295
Current liabilities
Short-term borrowings		45			210
Long-term debt due within one year		41			378
Accounts payable		205			209
Accrued expenses		175			110
Accounts Payable, Related Parties, Current		55			52
Customer deposits		110			102
Regulatory liabilities		50			38
Other		26			35
Total current liabilities		707			1,134
Long-term debt		2,281			1,480
Long-term debt to financing trusts		252			252
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		2,219			2,081
Asset retirement obligations		21			17
Non-pension postretirement benefit obligations		205			209
Regulatory liabilities		110			184
Other		61			61
Total deferred credits and other liabilities		2,616			2,552
Preferred Stock, Value, Outstanding		0			190
Total liabilities	[3]	$ 5,856			$ 5,418
Preferred Stock, Shares Outstanding		0			1,900,000
Preferred stock(b)		$ 0			$ 190
Shareholders’ equity
Common stock		1,421			1,367
Total shareholders’ equity		2,848			2,687
BGE preference stock not subject to mandatory redemption		0			190
Total equity		2,848			2,877
Member’s equity
Retained earnings		1,427			1,320
Liabilities and Equity		8,704			8,295
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets (a)		26			26
Deferred credits and other liabilities
Total liabilities		42			122
Pepco Holdings LLC [Member] | Predecessor [Member]
Current assets
Cash and cash equivalents					26
Restricted cash and cash equivalents					14
Accounts receivable, net
Customer					581
Other					319
Mark-to-market derivative assets					18
Inventories, net
Fossil fuel					9
Materials and supplies					122
Regulatory assets					305
Other					80
Total current assets					1,474
Property, plant and equipment, net					10,864
Deferred debits and other assets
Regulatory assets					2,277
Investments					80
Goodwill					1,406
Mark-to-market derivative assets					0
Prepaid pension asset					0
Deferred income taxes					14
Notes, Loans and Financing Receivable, Gross, Noncurrent					4
Other					69
Deferred Costs and Other Assets					3,850
Total assets (a)	[4]				16,188
Current liabilities
Short-term borrowings					958
Long-term debt due within one year					456
Accounts payable					404
Accrued expenses					266
Accounts Payable, Related Parties, Current					0
Mark-to-market derivative liabilities					0
Unamortized energy contract liabilities					0
Customer deposits					107
Payables to Customers					0
Regulatory liabilities					66
Other					70
Total current liabilities					2,327
Long-term debt					4,823
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent					3,406
Asset retirement obligations					8
Pension obligations					466
Non-pension postretirement benefit obligations					215
Regulatory liabilities					147
Mark-to-market derivative liabilities					0
Unamortized energy contract liabilities					0
Other					200
Total deferred credits and other liabilities					4,442
Total liabilities	[4]				$ 11,592
Preferred Stock, Shares Outstanding					18,000
Preferred stock(b)	[5]				$ 183
Shareholders’ equity
Common stock					15
Accumulated other comprehensive loss, net					(36)
Total shareholders’ equity					4,413
BGE preference stock not subject to mandatory redemption	[5]				183
Member’s equity
Membership interest/Common stock(c)	[6]				3,832
Retained earnings					617
Accumulated other comprehensive loss, net					(36)
Total member’s equity					4,413
Liabilities and Equity					16,188
Pepco Holdings LLC [Member] | Predecessor [Member] | Additional Paid-in Capital [Member]
Shareholders’ equity
Common stock					3
Other paid-in capital					3,829
Pepco Holdings LLC [Member] | Successor [Member]
Current assets
Cash and cash equivalents		170
Restricted cash and cash equivalents		43
Accounts receivable, net
Customer		496
Other		283
Mark-to-market derivative assets		0
Inventories, net
Fossil fuel		6
Materials and supplies		116
Regulatory assets		653
Other		71
Total current assets		1,838
Property, plant and equipment, net		11,598
Deferred debits and other assets
Regulatory assets		2,851
Investments		133
Goodwill		4,005
Prepaid pension asset		509
Deferred income taxes		6
Notes, Loans and Financing Receivable, Gross, Noncurrent		4
Other		81
Deferred Costs and Other Assets		7,589
Total assets (a)	[4]	21,025
Current liabilities
Short-term borrowings		522
Long-term debt due within one year		253
Accounts payable		458
Accrued expenses		272
Accounts Payable, Related Parties, Current		94
Unamortized energy contract liabilities		335
Customer deposits		123
Payables to Customers		101
Regulatory liabilities		79
Other		47
Total current liabilities		2,284
Long-term debt		5,645
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		3,775
Asset retirement obligations		14
Pension obligations		0
Non-pension postretirement benefit obligations		134
Regulatory liabilities		158
Unamortized energy contract liabilities		750
Other		249
Total deferred credits and other liabilities		5,080
Total liabilities	[4]	13,009
Preferred stock(b)		0
Shareholders’ equity
Common stock			$ 165
Accumulated other comprehensive loss, net		0
BGE preference stock not subject to mandatory redemption		0
Member’s equity
Membership interest/Common stock(c)		8,077	7,200
Retained earnings		(61)
Accumulated other comprehensive loss, net		0
Total member’s equity		8,016	$ 7,200	[7]
Liabilities and Equity		21,025
Potomac Electric Power Company [Member]
Current assets
Cash and cash equivalents		9			5
Restricted cash and cash equivalents		33			2
Accounts receivable, net
Customer		235			230
Other		150			261
Inventories, net
Inventories, net		63			67
Regulatory assets		162			140
Other		32			21
Total current assets		684			726
Property, plant and equipment, net		5,571			5,162
Deferred debits and other assets
Regulatory assets		690			661
Investments		102			68
Prepaid pension asset		282			287
Other		6			4
Deferred Costs and Other Assets		1,080			1,020
Total assets (a)		7,335			6,908
Current liabilities
Short-term borrowings		23			64
Long-term debt due within one year		16			11
Accounts payable		209			145
Accrued expenses		113			119
Accounts Payable, Related Parties, Current		74			30
Customer deposits		53			46
Payables to Customers		68			0
Regulatory liabilities		11			15
Other		29			25
Total current liabilities		596			455
Long-term debt		2,333			2,340
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		1,910			1,723
Non-pension postretirement benefit obligations		43			49
Regulatory liabilities		20			29
Other		133			72
Total deferred credits and other liabilities		2,106			1,873
Total liabilities		5,035			4,668
Shareholders’ equity
Common stock		1,309			1,122
Total shareholders’ equity		2,300			2,240
Liabilities And Stockholders Equity Including Portion Attributable To Noncontrolling Interest		7,335			6,908
Member’s equity
Retained earnings		991			1,118
Atlantic City Electric Company [Member]
Current assets
Cash and cash equivalents		101			3
Restricted cash and cash equivalents		9			12
Accounts receivable, net
Customer		125			156
Other		44			242
Inventories, net
Inventories, net		22			23
Regulatory assets		96			98
Other		2			12
Total current assets		399			546
Property, plant and equipment, net		2,521			2,322
Deferred debits and other assets
Regulatory assets		405			414
Investments		0			0
Prepaid pension asset		84			82
Notes, Loans and Financing Receivable, Gross, Noncurrent		4			4
Other		44			19
Deferred Costs and Other Assets		537			519
Total assets (a)	[8]	3,457			3,387
Current liabilities
Short-term borrowings		0			5
Long-term debt due within one year		35			48
Accounts payable		132			96
Accrued expenses		38			70
Accounts Payable, Related Parties, Current		29			16
Customer deposits		33			30
Payables to Customers		20			0
Regulatory liabilities		25			18
Other		8			14
Total current liabilities		320			297
Long-term debt		1,120			1,153
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		917			885
Non-pension postretirement benefit obligations		34			33
Regulatory liabilities		0			7
Other		32			12
Total deferred credits and other liabilities		983			937
Total liabilities	[8]	2,423			2,387
Shareholders’ equity
Common stock		912			773
Total shareholders’ equity		1,034			1,000
Liabilities And Stockholders Equity Including Portion Attributable To Noncontrolling Interest		3,457			3,387
Member’s equity
Retained earnings		$ 122			$ 227
[1]	Exelon’s consolidated assets include $8,893 million and $8,268 million at December 31, 2016 and December 31, 2015, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,356 million and $3,264 million at December 31, 2016 and December 31, 2015, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2–Variable Interest Entities.
[2]	Generation’s consolidated assets include $8,817 million and $8,235 million at December 31, 2016 and 2015, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,170 million and $3,135 million at December 31, 2016 and 2015, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 2–Variable Interest Entities.
[3]	BGE’s consolidated assets include $26 million and $26 million at December 31, 2016 and December 31, 2015, respectively, of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $42 million and $122 million at December 31, 2016 and December 31, 2015, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 2 - Variable Interest Entities.
[4]	PHI’s consolidated total assets include $49 million and $30 million at December 31, 2016 and 2015, respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $143 million and $172 million at December 31, 2016 and 2015, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 2 - Variable Interest Entities.
[5]	At December 31, 2015, PHI had 18,000 shares of Series A preferred stock authorized and outstanding, par value $0.01 per share.
[6]	At December 31, 2015, PHI's (predecessor) shareholders' equity included $3,829 million of other paid-in capital and $3 million of common stock. At December 31, 2015, PHI had 400,000,000 shares of common stock authorized and 254,289,261 shares of common stock outstanding, par value $0.01 per share.
[7]	The March 24, 2016, beginning balance differs from the PHI Merger total purchase price by $59 million related to an acquisition accounting adjustment recorded at Exelon Corporate to reflect unitary state income tax consequences of the merger.
[8]	ACE’s consolidated assets include $32 million and $30 million at December 31, 2016 and 2015, respectively, of ACE’s consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated liabilities include $126 million and $172 million at December 31, 2016 and 2015, respectively, of ACE’s consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 2 - Variable Interest Entities.

Consolidated Balance Sheets (U5

Consolidated Balance Sheets (Unaudited) (Parenthetical)	Dec. 31, 2015$ / sharesshares
Common stock, par value | $ / shares	$ 0
Common stock, shares authorized	2,000,000,000
Common Stock, Shares, Outstanding	919,924,742
Treasury Stock, Shares held	35,000,000
Commonwealth Edison Co [Member]
Common Stock, Shares, Outstanding	127,016,973
PECO Energy Co [Member]
Common Stock, Shares, Outstanding	170,478,507
Baltimore Gas and Electric Company [Member]
Common Stock, Shares, Outstanding	1,000
Pepco Holdings LLC [Member] | Predecessor [Member]
Common stock, shares authorized	400,000,000
Common Stock, Shares, Outstanding	254,289,261
Preferred Stock, Par or Stated Value Per Share | $ / shares	$ 0.01
Common Stock, Par or Stated Value Per Share | $ / shares	$ 0.01
Potomac Electric Power Company [Member]
Common Stock, Shares, Outstanding	100
Delmarva Power and Light Company [Member]
Common Stock, Shares, Outstanding	1,000
Atlantic City Electric Company [Member]
Common Stock, Shares, Outstanding	8,546,017

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders Equity (Unaudited) - USD ($) shares in Thousands		Total		Pepco Holdings LLC [Member]		Common Stock Including Additional Paid in Capital [Member]Pepco Holdings LLC [Member]	[3]	Common Stock [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Membership Interest [Member]	Undistributed Earnings [Member]	Preference Stock Not Subject To Mandatory Redemption [Member]	PECO Energy Co [Member]	PECO Energy Co [Member]Common Stock [Member]	PECO Energy Co [Member]Retained Earnings [Member]	PECO Energy Co [Member]Accumulated Other Comprehensive Income (Loss) [Member]	Exelon Generation Co L L C [Member]		Exelon Generation Co L L C [Member]Accumulated Other Comprehensive Income (Loss) [Member]	Exelon Generation Co L L C [Member]Noncontrolling Interest [Member]	Exelon Generation Co L L C [Member]Membership Interest [Member]	Exelon Generation Co L L C [Member]Undistributed Earnings [Member]	Commonwealth Edison Co [Member]	Commonwealth Edison Co [Member]Common Stock [Member]	Commonwealth Edison Co [Member]Other Paid-In Capital [Member]	Commonwealth Edison Co [Member]Retained Deficit Unappropriated [Member]	Commonwealth Edison Co [Member]Retained Earnings Appropriated [Member]	Baltimore Gas and Electric Company [Member]	Baltimore Gas and Electric Company [Member]Common Stock [Member]	Baltimore Gas and Electric Company [Member]Retained Earnings [Member]	Baltimore Gas and Electric Company [Member]Membership Interest [Member]	Baltimore Gas and Electric Company [Member]Preference Stock Not Subject To Mandatory Redemption [Member]	Pepco Holdings LLC [Member]		Pepco Holdings LLC [Member]Pepco Holdings LLC [Member]	Pepco Holdings LLC [Member]Common Stock Including Additional Paid in Capital [Member]		Pepco Holdings LLC [Member]Retained Earnings [Member]	Pepco Holdings LLC [Member]Accumulated Other Comprehensive Income (Loss) [Member]	Pepco Holdings LLC [Member]Additional Paid-in Capital [Member]	Potomac Electric Power Company [Member]	Potomac Electric Power Company [Member]Common Stock [Member]	Potomac Electric Power Company [Member]Retained Earnings [Member]	Delmarva Power and Light Company [Member]	Delmarva Power and Light Company [Member]Common Stock [Member]	Delmarva Power and Light Company [Member]Retained Earnings [Member]	Atlantic City Electric Company [Member]	Atlantic City Electric Company [Member]Common Stock [Member]	Atlantic City Electric Company [Member]Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustments to Additional Paid in Capital, Other											$ 0	$ 0	$ 170,000,000							$ 170,000,000					$ 0	$ 273,000,000		$ 273,000,000																$ 80,000,000	$ 80,000,000		$ 130,000,000	$ 130,000,000
Income Tax Effects Allocated Directly to Equity, Other																$ 24,000,000	$ 24,000,000		$ 0	53,000,000				$ 53,000,000
Beginning Balance (in shares) at Dec. 31, 2013		892,034
Beginning Balance (Predecessor [Member]) at Dec. 31, 2013																																				$ 4,315,000,000			$ 3,754,000,000		$ 595,000,000	$ (34,000,000)
Beginning Balance at Dec. 31, 2013																3,065,000,000	2,415,000,000	$ 649,000,000	1,000,000							7,528,000,000	$ 1,588,000,000	5,190,000,000	$ (1,639,000,000)	$ 2,389,000,000														1,922,000,000	930,000,000	$ 992,000,000	1,044,000,000	407,000,000	$ 637,000,000	$ 857,000,000	$ 678,000,000	$ 179,000,000
Beginning Balance at Dec. 31, 2013																				12,742,000,000		$ 214,000,000	$ 17,000,000	8,898,000,000	3,613,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Predecessor [Member]																																				242,000,000					242,000,000
Net income		$ 1,820,000,000								$ 1,623,000,000		184,000,000			$ 13,000,000	352,000,000		352,000,000		1,019,000,000			184,000,000		835,000,000	408,000,000			408,000,000		$ 211,000,000		$ 211,000,000	$ 211,000,000										171,000,000		171,000,000	104,000,000		104,000,000	46,000,000		46,000,000
Dividends																										307,000,000				307,000,000
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease		$ (116,000,000)									116,000,000											116,000,000
Stock Issued During Period, Shares, Share-based Compensation, Gross		1,574
Stock Issued During Period, Value, Share-based Compensation, Gross		$ 72,000,000						$ 72,000,000
Employee stock purchase plan issuances | Predecessor [Member]																																				7,000,000
Employee stock purchase plan issuances		$ 35,000,000						35,000,000
Employee stock purchase plan issuances, shares		960
Common stock issuance Constellation merger, shares		0
Consolidated VIE dividend to noncontrolling interests		$ (421,000,000)						0				(421,000,000)
Noncontrolling Interest, Increase from Subsidiary Equity Issuance																				1,548,000,000			1,548,000,000	0
Preferred and preference stock dividends		(13,000,000)													(13,000,000)																(13,000,000)		(13,000,000)	(13,000,000)
Other comprehensive loss, net of income taxes | Predecessor [Member]																																				(12,000,000)						(12,000,000)
Other comprehensive loss, net of income taxes		(644,000,000)																		(250,000,000)		(134,000,000)
Acquisition of noncontrolling interests		(4,000,000)						2,000,000				(6,000,000)								(645,000,000)			0
Tax benefit on stock compensation | Predecessor [Member]																																				7,000,000
Tax benefit on stock compensation		47,000,000						(8,000,000)
Changes in equity of noncontrolling interest																								0
Fair value of financing contract payments		131,000,000						131,000,000
Transfer of CENG pension and non-pension postretirement benefit obligations		(2,000,000)						(2,000,000)
Reversal of CENG equity method AOCI, net of income taxes																				116,000,000
Distribution to member																									0
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared																									645,000,000
Noncontrolling Interest, Change in Redemption Value																				421,000,000
Noncontrolling interest acquired		1,548,000,000										1,548,000,000								5,000,000			5,000,000
Ending Balance at Dec. 31, 2014		$ 24,133,000,000						16,709,000,000	$ (2,327,000,000)	10,910,000,000	(2,684,000,000)	1,332,000,000			193,000,000																2,753,000,000	$ 1,360,000,000	1,203,000,000	2,563,000,000	$ 190,000,000
Ending Balance (in shares) at Dec. 31, 2014		894,568
Ending Balance (Predecessor [Member]) at Dec. 31, 2014																																				4,322,000,000			3,803,000,000		565,000,000	(46,000,000)
Ending Balance at Dec. 31, 2014																3,121,000,000	2,439,000,000	681,000,000	1,000,000							7,907,000,000	1,588,000,000	5,468,000,000	(1,639,000,000)	2,490,000,000														2,087,000,000	1,010,000,000	1,077,000,000	1,178,000,000	537,000,000	641,000,000	877,000,000	678,000,000	199,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options		$ 8,000,000
Payments to Acquire Businesses, Gross		386,000,000																		386,000,000
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared																									645,000,000
Payments to Acquire Businesses, Gross		386,000,000																		386,000,000
Stock Issued During Period, Value, Dividend Reinvestment Plan | Predecessor [Member]																																				28,000,000
Allocated Share-based Compensation Expense, Net of Tax | Predecessor [Member]																																				11,000,000
Allocated Share-based Compensation Expense, Net of Tax		80,000,000
Adjustments to Additional Paid in Capital, Other											0	0	170,000,000							170,000,000					0	273,000,000		273,000,000																80,000,000	80,000,000		130,000,000	130,000,000
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease		(116,000,000)									116,000,000											116,000,000
Temporary Equity, Other Changes		(528,000,000)									(528,000,000)									(4,000,000)
Dividends, Common Stock, Cash | Predecessor [Member]																																				272,000,000					272,000,000
Dividends, Common Stock, Cash		(1,071,000,000)								(1,071,000,000)						(320,000,000)		(320,000,000)																										(86,000,000)		(86,000,000)	(100,000,000)		(100,000,000)	(26,000,000)		(26,000,000)
Noncontrolling Interest, Increase from Business Combination								0
Other Additional Capital																										5,000,000		5,000,000
Retained Earnings, Appropriated																													(408,000,000)	408,000,000
Common stock | Predecessor [Member]																																				14,000,000
Common stock | Predecessor [Member]																																				14,000,000
Adjustments to Additional Paid in Capital, Other		0																								202,000,000		202,000,000			7,000,000	7,000,000		7,000,000	0									112,000,000	112,000,000		75,000,000	75,000,000		95,000,000	95,000,000
Income Tax Effects Allocated Directly to Equity, Other		0									0	0	$ 47,000,000			16,000,000	16,000,000			(47,000,000)					0
Beginning Balance at Dec. 31, 2014																				14,051,000,000		(36,000,000)	1,333,000,000	8,951,000,000	3,803,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Predecessor [Member]																																				327,000,000					327,000,000
Net income		2,250,000,000								2,269,000,000		(32,000,000)			13,000,000	378,000,000		378,000,000		1,340,000,000			(32,000,000)		1,372,000,000	426,000,000			426,000,000		288,000,000		288,000,000	288,000,000										187,000,000		187,000,000	76,000,000		76,000,000	40,000,000		40,000,000
Dividends																										299,000,000				299,000,000
Noncontrolling Interest, Period Increase (Decrease)		4,000,000						0				4,000,000
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease		$ 0																		0
Stock Issued During Period, Shares, Share-based Compensation, Gross		1,430
Stock Issued During Period, Value, Share-based Compensation, Gross		$ 70,000,000						70,000,000
Employee stock purchase plan issuances | Predecessor [Member]																																				3,000,000
Employee stock purchase plan issuances		$ 32,000,000						32,000,000
Employee stock purchase plan issuances, shares		1,170
Consolidated VIE dividend to noncontrolling interests																							0
Preferred and preference stock dividends																															(13,000,000)		(13,000,000)	(13,000,000)
Other comprehensive loss, net of income taxes | Predecessor [Member]																																				10,000,000	[1]					10,000,000
Other comprehensive loss, net of income taxes		$ 60,000,000	[1]								60,000,000									(27,000,000)	[1]	(27,000,000)
Common stock dividends		(1,111,000,000)								(1,111,000,000)		0
Preference stock dividends		13,000,000													13,000,000
Tax benefit on stock compensation | Predecessor [Member]																																				5,000,000
Tax benefit on stock compensation		46,000,000
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared		0																		(2,474,000,000)			0		2,474,000,000
Noncontrolling Interest, Change in Redemption Value											0	4,000,000								4,000,000				0
Noncontrolling interest acquired																				1,000,000				(1,000,000)
Ending Balance at Dec. 31, 2015		$ 27,294,000,000						18,676,000,000	(2,327,000,000)	12,068,000,000	(2,624,000,000)	1,308,000,000			193,000,000																2,877,000,000	1,367,000,000	1,320,000,000	2,687,000,000	190,000,000
Ending Balance (in shares) at Dec. 31, 2015		954,668
Ending Balance (Predecessor [Member]) at Dec. 31, 2015																																				4,413,000,000			3,832,000,000	[2]	617,000,000	(36,000,000)
Ending Balance at Dec. 31, 2015		$ 25,793,000,000														3,236,000,000	2,455,000,000	780,000,000	1,000,000							8,243,000,000	1,588,000,000	5,677,000,000	(1,639,000,000)	2,617,000,000	2,687,000,000													2,240,000,000	1,122,000,000	1,118,000,000	1,237,000,000	612,000,000	625,000,000	1,000,000,000	773,000,000	227,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Shares, New Issues		57,500
Stock Issued During Period, Value, New Issues		$ 1,868,000,000						1,868,000,000
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options		(3,000,000)						3,000,000
Payments to Acquire Businesses, Gross		40,000,000																		40,000,000
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared		0																		(2,474,000,000)			0		2,474,000,000
Payments to Acquire Businesses, Gross		40,000,000																		40,000,000
Stock Issued During Period, Value, Dividend Reinvestment Plan | Predecessor [Member]																																				11,000,000
Allocated Share-based Compensation Expense, Net of Tax | Predecessor [Member]																																				8,000,000
Allocated Share-based Compensation Expense, Net of Tax		73,000,000
Adjustments to Additional Paid in Capital, Other		0																								202,000,000		202,000,000			7,000,000	7,000,000		7,000,000	0									112,000,000	112,000,000		75,000,000	75,000,000		95,000,000	95,000,000
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease		0																		0
Temporary Equity, Other Changes		4,000,000										(4,000,000)
Dividends, Common Stock, Cash | Predecessor [Member]																																				275,000,000					275,000,000
Dividends, Common Stock, Cash										0						(279,000,000)		(279,000,000)													(158,000,000)		(158,000,000)	(158,000,000)										(146,000,000)		(146,000,000)	(92,000,000)		(92,000,000)	(12,000,000)		(12,000,000)
Other Additional Capital																										7,000,000		7,000,000
Members' Equity | Predecessor [Member]																																				4,413,000,000
Members' Equity																				11,635,000,000
Retained Earnings, Appropriated																										2,617,000,000			(426,000,000)	426,000,000
Common stock | Predecessor [Member]																																				15,000,000							$ 3,000,000
Common stock		18,676,000,000														2,455,000,000										1,588,000,000					1,367,000,000													1,122,000,000			612,000,000			773,000,000
Additional Paid in Capital | Predecessor [Member]																																											3,829,000,000
Additional Paid in Capital																										5,677,000,000
Common stock | Predecessor [Member]																																				15,000,000							3,000,000
Common stock		18,676,000,000														2,455,000,000										1,588,000,000					1,367,000,000													1,122,000,000			612,000,000			773,000,000
Additional Paid in Capital | Predecessor [Member]																																											3,829,000,000
Additional Paid in Capital																										5,677,000,000
Beginning Balance at Dec. 31, 2015																				12,942,000,000		(63,000,000)	1,307,000,000	8,997,000,000	2,701,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Predecessor [Member]																																				19,000,000					19,000,000
Employee stock purchase plan issuances | Predecessor [Member]																																				3,000,000
Other comprehensive loss, net of income taxes | Predecessor [Member]																																				1,000,000						1,000,000
Tax benefit on stock compensation | Predecessor [Member]																																				1,000,000
Ending Balance (Predecessor [Member]) at Mar. 23, 2016																																				4,439,000,000			3,838,000,000	[2]	636,000,000	(35,000,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Allocated Share-based Compensation Expense, Net of Tax | Predecessor [Member]																																				2,000,000
Adjustments to Additional Paid in Capital, Other																										315,000,000		315,000,000			61,000,000	61,000,000	0	61,000,000	0									187,000,000	187,000,000		152,000,000	152,000,000		139,000,000	139,000,000	0
Income Tax Effects Allocated Directly to Equity, Other		$ 0														18,000,000	18,000,000			98,000,000				98,000,000
Beginning Balance (in shares) at Dec. 31, 2015		954,668
Beginning Balance (Predecessor [Member]) at Dec. 31, 2015																																				4,413,000,000			3,832,000,000	[2]	617,000,000	(36,000,000)
Beginning Balance at Dec. 31, 2015		$ 25,793,000,000														3,236,000,000	2,455,000,000	780,000,000	1,000,000							8,243,000,000	1,588,000,000	5,677,000,000	(1,639,000,000)	2,617,000,000	2,687,000,000													2,240,000,000	1,122,000,000	1,118,000,000	1,237,000,000	612,000,000	625,000,000	1,000,000,000	773,000,000	227,000,000
Beginning Balance at Dec. 31, 2015																				12,942,000,000		(63,000,000)	1,307,000,000	8,997,000,000	2,701,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		1,204,000,000		$ (66,000,000)						1,134,000,000		62,000,000			8,000,000	438,000,000		438,000,000		558,000,000			62,000,000		496,000,000	378,000,000			378,000,000		294,000,000		294,000,000	294,000,000										42,000,000		42,000,000	(9,000,000)		(9,000,000)	(42,000,000)		(42,000,000)
Dividends																										369,000,000				369,000,000
Noncontrolling Interest, Period Increase (Decrease)		(5,000,000)						0				(5,000,000)
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease		$ 0																		0
Stock Issued During Period, Shares, Share-based Compensation, Gross		2,868
Stock Issued During Period, Value, Share-based Compensation, Gross		$ 85,000,000						85,000,000
Employee stock purchase plan issuances		$ 55,000,000						55,000,000
Employee stock purchase plan issuances, shares		1,242
Preferred and preference stock dividends		$ (8,000,000)													8,000,000																(8,000,000)		(8,000,000)	(8,000,000)
Other comprehensive loss, net of income taxes		(36,000,000)									(36,000,000)	0								9,000,000		9,000,000
Preference stock dividends		(193,000,000)													193,000,000
Tax benefit on stock compensation		68,000,000
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared												0		$ 922,000,000						922,000,000		0									(7,000,000)	(7,000,000)		(7,000,000)
Noncontrolling Interest, Change in Redemption Value		0																		5,000,000			5,000,000
Noncontrolling interest acquired		396,000,000							0	0	0				0					396,000,000		0	$ 400,000,000	$ (4,000,000)	$ 0
Ending Balance at Dec. 31, 2016		$ 27,612,000,000						18,794,000,000	(2,327,000,000)	12,030,000,000	(2,660,000,000)	1,775,000,000			0																2,848,000,000	1,421,000,000	1,427,000,000	2,848,000,000	0
Ending Balance (in shares) at Dec. 31, 2016		958,778
Ending Balance at Dec. 31, 2016		$ 25,837,000,000														3,415,000,000	2,473,000,000	941,000,000	1,000,000							8,725,000,000	1,588,000,000	6,150,000,000	(1,639,000,000)	2,626,000,000	2,848,000,000													2,300,000,000	1,309,000,000	991,000,000	1,326,000,000	764,000,000	562,000,000	1,034,000,000	912,000,000	122,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options		(18,000,000)
Payments to Acquire Businesses, Gross		6,934,000,000																		293,000,000																								33,000,000
Preferred Stock, Redemption Amount																															(190,000,000)				(190,000,000)
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared												0		$ 922,000,000						922,000,000		$ 0									(7,000,000)	(7,000,000)		(7,000,000)
Payments to Acquire Businesses, Gross		6,934,000,000																		293,000,000																								33,000,000
Allocated Share-based Compensation Expense, Net of Tax		107,000,000
Adjustments to Additional Paid in Capital, Other																										315,000,000		315,000,000			61,000,000	61,000,000	0	61,000,000	0									187,000,000	187,000,000		152,000,000	152,000,000		139,000,000	139,000,000	0
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease		0																		0
Temporary Equity, Other Changes																				(157,000,000)
Dividends, Common Stock, Cash		(1,172,000,000)								1,172,000,000						(277,000,000)		(277,000,000)													(179,000,000)		(179,000,000)	(179,000,000)										(169,000,000)		(169,000,000)	(54,000,000)		(54,000,000)	(63,000,000)		(63,000,000)
Common stock | Predecessor [Member]																																				3,000,000
Common stock | Successor [Member]																																											3,000,000
Additional Paid in Capital | Successor [Member]																																											3,835,000,000
Common stock | Predecessor [Member]																																				3,000,000
Common stock | Successor [Member]																																											3,000,000
Additional Paid in Capital | Successor [Member]																																											$ 3,835,000,000
Beginning Balance (Predecessor [Member]) at Mar. 23, 2016																																				4,439,000,000			3,838,000,000	[2]	636,000,000	(35,000,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Predecessor [Member]																																									(61,000,000)
Net income | Successor [Member]																																				(61,000,000)
Other comprehensive loss, net of income taxes | Successor [Member]																																				0
Ending Balance at Dec. 31, 2016		$ 27,612,000,000						$ 18,794,000,000	$ (2,327,000,000)	$ 12,030,000,000	$ (2,660,000,000)	$ 1,775,000,000			$ 0																2,848,000,000	$ 1,421,000,000	$ 1,427,000,000	$ 2,848,000,000	$ 0
Ending Balance (in shares) at Dec. 31, 2016		958,778
Ending Balance at Dec. 31, 2016		$ 25,837,000,000														3,415,000,000	$ 2,473,000,000	$ 941,000,000	$ 1,000,000							8,725,000,000	$ 1,588,000,000	6,150,000,000	(1,639,000,000)	2,626,000,000	2,848,000,000													2,300,000,000	$ 1,309,000,000	$ 991,000,000	1,326,000,000	$ 764,000,000	$ 562,000,000	1,034,000,000	$ 912,000,000	$ 122,000,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Members Equity Including Portion Attributable To Noncontrolling Interest Acquisitions | Successor [Member]																																				1,251,000,000			1,251,000,000
Payments to Acquire Businesses, Gross | Successor [Member]				62,000,000	[3]	$ 62,000,000																																$ 33,000,000
Payments to Acquire Businesses, Gross | Successor [Member]				$ 62,000,000	[3]	$ 62,000,000																																$ 33,000,000
Other Additional Capital																										158,000,000		$ 158,000,000
Members' Equity | Successor [Member]																																				8,016,000,000			8,077,000,000		$ (61,000,000)	$ 0
Members' Equity																				$ 11,482,000,000
Retained Earnings, Appropriated																										2,626,000,000			$ (378,000,000)	$ 378,000,000
Business Combination, Contingent Consideration, Asset | Successor [Member]	[4]																																			400,000,000			400,000,000
Common stock		18,794,000,000														2,473,000,000										1,588,000,000					1,421,000,000													1,309,000,000			764,000,000			912,000,000
Additional Paid in Capital																										6,150,000,000
Fresh-Start Adjustment, Increase (Decrease), Deferred Income Tax Liabilities, Noncurrent | Successor [Member]																																				35,000,000			35,000,000
Common stock		$ 18,794,000,000														$ 2,473,000,000										1,588,000,000					$ 1,421,000,000													$ 1,309,000,000			$ 764,000,000			$ 912,000,000
Fresh-Start Adjustment, Increase (Decrease), Deferred Income Tax Liabilities, Noncurrent | Successor [Member]																																				$ 35,000,000			$ 35,000,000
Additional Paid in Capital																										$ 6,150,000,000
[1]	All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.
[2]	At March 23, 2016 and December 31, 2015, PHI's (predecessor) shareholders' equity included $3,835 million and $3,829 million of other paid-in capital, and $3 million and $3 million of common stock, respectively.
[3]	he liabilities assumed include $29 million for PHI stock-based compensation awards and $33 million for a merger related obligation, each assumed by PHI from Exelon. See Note 4 — Mergers, Acquisitions, and Dispositions.
[4]	Distribution to member includes $235 million of net assets associated with PHI's unregulated business interests and $165 million of cash, each of which were distributed by PHI to Exelon.

Consolidated Statement of Chan7

Consolidated Statement of Changes in Shareholders Equity (Unaudited) (Parenthetical) $ in Millions	12 Months Ended
	Dec. 31, 2014USD ($)
Other comprehensive income, income taxes	$ 412
Exelon Generation Co L L C [Member]
Other comprehensive income, income taxes	157
PECO Energy Co [Member]
Other comprehensive income, income taxes	$ 0

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Significant Accounting Policies (All Registrants)	Significant Accounting Policies (All Registrants) Description of Business (All Registrants) Exelon is a utility services holding company engaged through its principal subsidiaries in the energy generation and energy distribution and transmission businesses. Prior to March 23, 2016 , Exelon's principal, wholly owned subsidiaries included Generation, ComEd, PECO and BGE. On March 23, 2016 , in conjunction with the Amended and Restated Agreement and Plan of Merger (the PHI Merger Agreement), Purple Acquisition Corp, a wholly owned subsidiary of Exelon, merged with and into PHI, with PHI continuing as the surviving entity as a wholly owned subsidiary of Exelon. PHI is a utility services holding company engaged through its principal wholly owned subsidiaries, Pepco, DPL and ACE, in the energy distribution and transmission businesses. Refer to Note 4 - Mergers, Acquisitions, and Dispositions for further information regarding the merger transaction. The energy generation business includes: • Generation : Generation, physical delivery and marketing of power across multiple geographical regions through its customer-facing business, Constellation. Generation also sells renewable energy and other energy-related products and services. Generation has six reportable segments consisting of the Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. The energy delivery businesses include: • ComEd : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in northern Illinois, including the City of Chicago. • PECO : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in southeastern Pennsylvania, including the City of Philadelphia, and the purchase and regulated retail sale of natural gas and the provision of natural gas distribution services in the Pennsylvania counties surrounding the City of Philadelphia. • BGE : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in central Maryland, including the City of Baltimore, and the purchase and regulated retail sale of natural gas and the provision of natural gas distribution services in central Maryland, including the City of Baltimore. • Pepco : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in the District of Columbia and major portions of Prince George's County and Montgomery County in Maryland. • DPL : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in portions of Maryland and Delaware, and the purchase and regulated retail sale of natural gas and the provision of natural gas distribution services in northern Delaware. • ACE : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in southern New Jersey. Basis of Presentation (All Registrants) This is a combined annual report of all registrants. The Notes to the Consolidated Financial Statements apply to the registrants as indicated above in the Index to Combined Notes to Consolidated Financial Statements and parenthetically next to each corresponding disclosure. When appropriate, the registrants are named specifically for their related activities and disclosures. Each of the Registrant’s Consolidated Financial Statements includes the accounts of its subsidiaries. All intercompany transactions have been eliminated. All Equity in earnings (losses) from unconsolidated affiliates have been presented below Income taxes in the Registrants' Consolidated Statements of Operations and Comprehensive Income starting in the first quarter of 2015. Pursuant to the acquisition of PHI, Exelon’s financial reporting reflects PHI’s consolidated financial results subsequent to the March 23, 2016 , acquisition date. Exelon has accounted for the merger transaction applying the acquisition method of accounting, which requires the assets acquired and liabilities assumed by Exelon to be reported in Exelon’s financial statements at fair value, with any excess of the purchase price over the fair value of net assets acquired reported as goodwill. Exelon has pushed-down the application of the acquisition method of accounting to the consolidated financial statements of PHI such that the assets and liabilities of PHI are similarly recorded at their respective fair values, and goodwill has been established as of the acquisition date. Accordingly, the consolidated financial statements of PHI for periods before and after the March 23, 2016 , acquisition date reflect different bases of accounting, and the financial positions and the results of operations of the predecessor and successor periods are not comparable. The acquisition method of accounting has not been pushed down to PHI’s wholly-owned subsidiary utility registrants, Pepco, DPL and ACE. For financial statement purposes, beginning on March 24, 2016 , disclosures that had solely related to PHI, Pepco, DPL or ACE activities now also apply to Exelon, unless otherwise noted. Through its business services subsidiary, BSC, Exelon provides its subsidiaries with a variety of support services at cost, including legal, human resources, financial, information technology and supply management services. The costs of BSC, including support services, are directly charged or allocated to the applicable subsidiaries using a cost-causative allocation method. Corporate governance-type costs that cannot be directly assigned are allocated based on a Modified Massachusetts Formula, which is a method that utilizes a combination of gross revenues, total assets and direct labor costs for the allocation base. The results of Exelon’s corporate operations are presented as “Other” within the consolidated financial statements and include intercompany eliminations unless otherwise disclosed. PHISCO, a wholly owned subsidiary of PHI, provides a variety of support services at cost, including legal, accounting, engineering, distribution and transmission planning, asset management, system operations, and power procurement, to PHI and its operating subsidiaries. These services are directly charged or allocated pursuant to service agreements among PHI Service Company and the participating operating subsidiaries. Exelon owns 100% of all of its significant consolidated subsidiaries, including PHI, either directly or indirectly, except for ComEd, of which Exelon owns more than 99% . As of December 31, 2016, Exelon owned none of BGE's preferred securities, which BGE redeemed in 2016. Exelon has reflected the third-party interests in ComEd, which totaled less than $1 million at December 31, 2016 and December 31, 2015 , as equity, and BGE’s preference stock as BGE preference stock not subject to mandatory redemption in its consolidated financial statements. BGE is subject to some ring-fencing measures established by order of the MDPSC. As part of this arrangement, BGE common stock is held directly by RF Holdco LLC, which is an indirect subsidiary of Exelon. GSS Holdings (BGE Utility), an unrelated party, holds a nominal non-economic interest in RF Holdco LLC with limited voting rights on specified matters. PHI is subject to some ring-fencing measures established by orders of the DCPSC, DPSC, MDPSC and NJBPU, pursuant to which all of the membership interest in PHI is held directly by PH Holdco LLC, which is an indirect subsidiary of Exelon. GSS Holdings (PH Utility), Inc., an unrelated party, holds a nominal non-economic interest in PH Holdco LLC with limited voting rights on specified matters. PHI owns 100% of its subsidiaries including Pepco, DPL and ACE. Generation owns 100% of all of its significant consolidated subsidiaries, either directly or indirectly, except for certain variable interest entities, including CENG, of which Generation holds a 50.01% interest. The remaining interests are included in noncontrolling interests on Exelon’s and Generation’s Consolidated Balance Sheets. See Note 2 — Variable Interest Entities for further discussion of Exelon’s and Generation’s consolidated VIEs. The Registrants consolidate the accounts of entities in which a Registrant has a controlling financial interest, after the elimination of intercompany transactions. A controlling financial interest is evidenced by either a voting interest greater than 50% in which the Registrant can exercise control over the operations and policies of the investee, or the results of a model that identifies the Registrant or one of its subsidiaries as the primary beneficiary of a VIE. Where the Registrants do not have a controlling financial interest in an entity, proportionate consolidation, equity method accounting or cost method accounting is applied. The Registrants apply proportionate consolidation when they have an undivided interest in an asset and are proportionately liable for their share of each liability associated with the asset. The Registrants proportionately consolidate their undivided ownership interests in jointly owned electric plants and transmission facilities. Under proportionate consolidation, the Registrants separately record their proportionate share of the assets, liabilities, revenues and expenses related to the undivided interest in the asset. The Registrants apply equity method accounting when they have significant influence over an investee through an ownership in common stock, which generally approximates a 20% to 50% voting interest. The Registrants apply equity method accounting to certain investments and joint ventures, including certain financing trusts of ComEd, PECO and BGE. Under the equity method, the Registrants report their interest in the entity as an investment and the Registrants’ percentage share of the earnings from the entity as single line items in their financial statements. The Registrants use the cost method if they lack significant influence, which generally results when they hold less than 20% of the common stock of an entity. Under the cost method, the Registrants report their investments at cost and recognize income only to the extent dividends or distributions are received. The accompanying consolidated financial statements have been prepared in accordance with GAAP for annual financial statements and in accordance with the instructions to Form 10-K and Regulation S-X promulgated by the SEC. Use of Estimates (All Registrants) The preparation of financial statements of each of the Registrants in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Areas in which significant estimates have been made include, but are not limited to, the accounting for nuclear decommissioning costs and other AROs, pension and other postretirement benefits, the application of purchase accounting, inventory reserves, allowance for uncollectible accounts, goodwill and asset impairments, derivative instruments, unamortized energy contracts, fixed asset depreciation, environmental costs and other loss contingencies, taxes and unbilled energy revenues. Actual results could differ from those estimates. Reclassifications (All Registrants) Certain prior year amounts in the Registrants' Consolidated Statements of Operations and Comprehensive Income, Consolidated Balance Sheets and Consolidated Statements of Cash Flows have been reclassified between line items for comparative purposes. The reclassifications did not affect any of the Registrants’ net income, financial positions, or cash flows from operating activities. Certain prior year amounts in the Consolidated Statements of Operations and Comprehensive Income, Consolidated Balance Sheets and Consolidated Statements of Cash Flows of PHI, Pepco, DPL and ACE have been reclassified to conform the presentation of these amounts to the current period presentation in Exelon’s financial statements. Most significantly for PHI, Pepco, DPL and ACE, current regulatory assets and liabilities have been presented separately from the non-current portions in each respective Consolidated Balance Sheet where recovery or refund is expected within the next 12 months. Additionally, for PHI, Pepco, DPL and ACE, the removal cost within Accumulated depreciation was reclassified to the Regulatory liability or Regulatory asset account to align with Exelon’s presentation. The reclassifications were not considered errors in the prior financial statements. Accounting for the Effects of Regulation (Exelon, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE) The Registrants apply the authoritative guidance for accounting for certain types of regulation, which requires them to record in their consolidated financial statements the effects of cost-based rate regulation for entities with regulated operations that meet the following criteria: 1) rates are established or approved by a third-party regulator; (2) rates are designed to recover the entities’ cost of providing services or products; and (3) there is a reasonable expectation that rates are set at levels that will recover the entities’ costs from customers. Exelon and the Utility Registrants account for their regulated operations in accordance with regulatory and legislative guidance from the regulatory authorities having jurisdiction, principally the ICC, the PAPUC, the MDPSC, the DCPSC, the DPSC and the NJBPU, under state public utility laws and the FERC under various Federal laws. Regulatory assets and liabilities are amortized and the related expense or revenue is recognized in the Consolidated Statements of Operations consistent with the recovery or refund included in customer rates. Exelon believes that it is probable that its currently recorded regulatory assets and liabilities will be recovered and settled, respectively, in future rates. Exelon and the Utility Registrants continue to evaluate their respective abilities to continue to apply the authoritative guidance for accounting for certain types of regulation, including consideration of current events in their respective regulatory and political environments. If a separable portion of the Registrants' business was no longer able to meet the criteria discussed above, the affected entities would be required to eliminate from their consolidated financial statements the effects of regulation for that portion, which could have a material impact on their results of operations and financial positions. See Note 3 — Regulatory Matters for additional information. ACE has a recovery mechanism for purchased power costs associated with BGS. ACE records a deferred energy supply costs regulatory asset or regulatory liability for under or over-recovered costs that are expected to be recovered from or refunded to ACE customers, respectively. In the first quarter of 2016, ACE changed its method of accounting for determining under or over-recovered costs in this recovery mechanism to include unbilled revenues in the determination of under or over-recovered costs. ACE believes this change is preferable as it better reflects the economic impacts of dollar-for-dollar cost recovery mechanisms. ACE applied the change retrospectively. The impact of the change was a $12 million reduction to ACE’s opening Retained earnings as of January 1, 2014 with a corresponding reduction to Regulatory assets. The impact of the change on Net income attributable to common shareholder was an increase of $2 million and $1 million for the years ended December 31, 2015 and December 31, 2014 , respectively. The Registrants treat the impacts of a final rate order received after the balance sheet date but prior to the issuance of the financial statements as a non-recognized subsequent event, as the receipt of a final rate order is a separate and distinct event that has future impacts on the parties affected by the order. Revenues (All Registrants) Operating Revenues. Operating revenues are recorded as service is rendered or energy is delivered to customers. At the end of each month, the Registrants accrue an estimate for the unbilled amount of energy delivered or services provided to customers. ComEd records its best estimates of the distribution and transmission revenue impacts resulting from changes in rates that ComEd believes are probable of approval by the ICC and FERC in accordance with its formula rate mechanisms. BGE, Pepco, DPL and ACE record their best estimate of the transmission revenue impacts resulting from changes in rates that they each believe are probable of approval by FERC in accordance with their formula rate mechanisms. See Note 3 — Regulatory Matters and Note 6 — Accounts Receivable for further information. RTOs and ISOs. In RTO and ISO markets that facilitate the dispatch of energy and energy-related products, the Registrants generally report sales and purchases conducted on a net hourly basis in either revenues or purchased power on their Consolidated Statements of Operations and Comprehensive Income, the classification of which depends on the net hourly activity. In addition, capacity revenue and expense classification is based on the net sale or purchase position of the Company in the different RTOs and ISOs. Option Contracts, Swaps and Commodity Derivatives. Certain option contracts and swap arrangements that meet the definition of derivative instruments are recorded at fair value with subsequent changes in fair value recognized as revenue or expense. The classification of revenue or expense is based on the intent of the transaction. For example, gas transactions may be used to hedge the sale of power. This will result in the change in fair value recorded through revenue. To the extent a Utility Registrant receives full cost recovery for energy procurement and related costs from retail customers, it records the fair value of its energy swap contracts with unaffiliated suppliers as well as an offsetting regulatory asset or liability on its Consolidated Balance Sheets. Refer to Note 3 — Regulatory Matters and Note 13 — Derivative Financial Instruments for further information. Proprietary Trading Activities. Exelon and Generation account for Generation’s trading activities under the provisions of the authoritative guidance for accounting for contracts involved in energy trading and risk management activities, which require energy revenues and costs related to energy trading contracts to be presented on a net basis in the Consolidated Statements of Operations and Comprehensive Income. Commodity derivatives used for trading purposes are accounted for using the mark-to-market method with unrealized gains and losses recognized in operating revenues. Refer to Note 13 — Derivative Financial Instruments for further information. Income Taxes (All Registrants) Deferred Federal and state income taxes are provided on all significant temporary differences between the book basis and the tax basis of assets and liabilities and for tax benefits carried forward. Investment tax credits have been deferred on the Registrants’ Consolidated Balance Sheets and are recognized in book income over the life of the related property. In accordance with applicable authoritative guidance, the Registrants account for uncertain income tax positions using a benefit recognition model with a two-step approach; a more-likely-than-not recognition criterion; and a measurement approach that measures the position as the largest amount of tax benefit that is greater than 50% likely of being realized upon ultimate settlement. If it is not more-likely-than-not that the benefit of the tax position will be sustained on its technical merits, no benefit is recorded. Uncertain tax positions that relate only to timing of when an item is included on a tax return are considered to have met the recognition threshold. The Registrants recognize accrued interest related to unrecognized tax benefits in Interest expense or Other income and deductions (interest income) and recognize penalties related to unrecognized tax benefits in Other, net on their Consolidated Statements of Operations and Comprehensive Income. In the first quarter of 2016, PHI, Pepco, DPL and ACE changed their accounting for classification of interest on uncertain tax positions. PHI, Pepco, DPL and ACE have reclassified interest on uncertain tax positions as Interest expense from Income tax expense in the Consolidated Statements of Operations and Comprehensive Income. GAAP does not address the preferability of one acceptable method of accounting over the other for the classification of interest on uncertain tax positions. However, PHI, Pepco, DPL and ACE believe this change is preferable for comparability of their financial statements with the financial statements of the other Registrants in the combined filing, for consistency with FERC classification and for a more appropriate representation of the effective tax rate as they manage the settlement of uncertain tax positions and interest expense separately. PHI, Pepco, DPL and ACE applied the change retrospectively. The reclassification in the Consolidated Statements of Operations and Comprehensive Income for the year ended December 31, 2015 is $34 million and $4 million for PHI and Pepco, respectively, and for the year ended December 31, 2014 is $1 million for both Pepco and ACE. The impact on all other PHI Registrants for years ended December 31, 2015 and December 31, 2014 is less than $1 million . Pursuant to the IRC and relevant state taxing authorities, Exelon and its subsidiaries file consolidated or combined income tax returns for Federal and certain state jurisdictions where allowed or required. See Note 15 — Income Taxes for further information. Taxes Directly Imposed on Revenue-Producing Transactions (All Registrants) The Registrants collect certain taxes from customers such as sales and gross receipts taxes, along with other taxes, surcharges and fees that are levied by state or local governments on the sale or distribution of gas and electricity. Some of these taxes are imposed on the customer, but paid by the Registrants, while others are imposed on the Registrants. Where these taxes are imposed on the customer, such as sales taxes, they are reported on a net basis with no impact to the Consolidated Statements of Operations and Comprehensive Income. However, where these taxes are imposed on the Registrants, such as gross receipts taxes or other surcharges or fees, they are reported on a gross basis. Accordingly, revenues are recognized for the taxes collected from customers along with an offsetting expense. See Note 25 — Supplemental Financial Information for Generation’s, ComEd’s, PECO’s, BGE’s, Pepco's, DPL's and ACE's utility taxes that are presented on a gross basis. Cash and Cash Equivalents (All Registrants) The Registrants consider investments purchased with an original maturity of three months or less to be cash equivalents. Restricted Cash and Cash Equivalents (All Registrants) Restricted cash and cash equivalents represent funds that are restricted to satisfy designated current liabilities. As of December 31, 2016 and 2015 , Exelon Corporate’s restricted cash and cash equivalents primarily represented restricted funds for payment of medical, dental, vision and long-term disability benefits. Generation’s restricted cash and cash equivalents primarily included cash at various project-specific non-recourse financing structures for debt service and financing of operations of the underlying entities, see Note 14 - Debt and Credit Agreements for additional information on Generation’s project- specific financing structures. ComEd’s restricted cash primarily represented cash collateral held from suppliers associated with ComEd’s energy and REC procurement contracts. PECO’s restricted cash primarily represented funds from the sales of assets that were subject to PECO’s mortgage indenture. BGE’s restricted cash primarily represented funds restricted at its consolidated variable interest entity for repayment of rate stabilization bonds and cash collateral held from suppliers. PHI Corporate's restricted cash and cash equivalents primarily represented funds restricted for the payment of merger commitments and cash collateral held from its utility suppliers. Pepco's restricted cash and cash equivalents primarily represented funds restricted for the payment of merger commitments and collateral held from its utility suppliers. DPL's restricted cash and cash equivalents primarily represented cash collateral held from suppliers associated with procurement contracts. ACE's restricted cash and cash equivalents primarily represented funds restricted at its consolidated variable interest entity for repayment of transition bonds and cash collateral held from suppliers. Restricted cash and cash equivalents not available to satisfy current liabilities are classified as noncurrent assets. As of December 31, 2016 and 2015 , Exelon’s and Generation’s NDT funds, which are designated to satisfy future decommissioning obligations, were classified as noncurrent assets. As of December 31, 2016 , Exelon, Generation, ComEd, PECO, BGE, PHI and Pepco had investments in Rabbi trusts classified as noncurrent assets. Allowance for Uncollectible Accounts (All Registrants) The allowance for uncollectible accounts reflects the Registrants’ best estimates of losses on the accounts receivable balances. For Generation, the allowance is based on accounts receivable aging historical experience and other currently available information. ComEd, PECO and BGE estimate the allowance for uncollectible accounts on customer receivables by applying loss rates developed specifically for each company to the outstanding receivable balance by customer risk segment. At December 31, 2015, Pepco, DPL and ACE estimated the allowance for uncollectible accounts based on specific identification of material amounts at risk by customer and maintained a reserve based on their historical collection experience. At December 31, 2016, Pepco, DPL and ACE aligned the estimation of their allowance for uncollectible accounts to be consistent with ComEd, PECO and BGE, as described above. Risk segments represent a group of customers with similar credit quality indicators that are comprised based on various attributes, including delinquency of their balances and payment history. Loss rates applied to the accounts receivable balances are based on historical average charge-offs as a percentage of accounts receivable in each risk segment. Utility Registrants customers’ accounts are generally considered delinquent if the amount billed is not received by the time the next bill is issued, which normally occurs on a monthly basis. Utility Registrants' customer accounts are written off consistent with approved regulatory requirements. Utility Registrants' allowances for uncollectible accounts will continue to be affected by changes in volume, prices and economic conditions as well as changes in ICC, PAPUC, MDPSC, DCPSC, DPSC and NJBPU regulations. See Note 3 — Regulatory Matters for additional information regarding the regulatory recovery of uncollectible accounts receivable at ComEd. Variable Interest Entities (All Registrants) Exelon accounts for its investments in and arrangements with VIEs based on the authoritative guidance which includes the following specific requirements: • requires an entity to qualitatively assess whether it should consolidate a VIE based on whether the entity has a controlling financial interest, meaning (1) has the power to direct matters that most significantly impact the activities of the VIE, and (2) has the obligation to absorb losses or the right to receive benefits of the VIE that could potentially be significant to the VIE, • requires an ongoing reconsideration of this assessment instead of only upon certain triggering events, and • requires the entity that consolidates a VIE (the primary beneficiary) to disclose (1) the assets of the consolidated VIE, if they can be used to only settle specific obligations of the consolidated VIE, and (2) the liabilities of a consolidated VIE for which creditors do not have recourse to the general credit of the primary beneficiary. See Note 2 — Variable Interest Entities for additional information. Inventories (All Registrants) Inventory is recorded at the lower of weighted average cost or net realizable value. Provisions are recorded for excess and obsolete inventory. Fossil Fuel. Fossil fuel inventory includes natural gas held in storage, propane and oil. The costs of natural gas, propane and oil are generally included in inventory when purchased and charged to purchased power and fuel expense at weighted average cost when used or sold. Materials and Supplies. Materials and supplies inventory generally includes transmission, distribution and generating plant materials. Materials are generally charged to inventory when purchased and expensed or capitalized to property, plant and equipment, as appropriate, at weighted average cost when installed or used. Emission Allowances. Emission allowances are included in inventory (for emission allowances exercisable in the current year) and other deferred debits (for emission allowances that are exercisable beyond one year) and charged to purchased power and fuel expense at weighted average cost as they are used in operations. Marketable Securities (All Registrants) All marketable securities are reported at fair value. Marketable securities held in the NDT funds are classified as trading securities, and all other securities are classified as available-for-sale securities. Realized and unrealized gains and losses, net of tax, on Generation’s NDT funds associated with the Regulatory Agreement Units are included in regulatory liabilities at Exelon, ComEd and PECO and in Noncurrent payables to affiliates at Generation and in Noncurrent receivables from affiliates at ComEd and PECO. Realized and unrealized gains and losses, net of tax, on Generation’s NDT funds associated with the Non-Regulatory Agreement Units are included in earnings at Exelon and Generation. Unrealized gains and losses, net of tax, for Exelon's available-for-sale securities are reported in OCI. Any decline in the fair value of Exelon's available-for-sale securities below the cost basis is reviewed to determine if such decline is other-than-temporary. If the decline is determined to be other-than-temporary, the cost basis of the available-for-sale securities is written down to fair value as a new cost basis and the amount of the write-down is included in earnings. See Note 3 — Regulatory Matters for additional information regarding ComEd’s and PECO’s regulatory assets and liabilities and Note 12 — Fair Value of Financial Assets and Liabilities and Note 16 — Asset Retirement Obligations for information regarding marketable securities held by NDT funds. Property, Plant and Equipment (All Registrants) Property, plant and equipment is recorded at original cost. Original cost includes construction-related direct labor and material costs. The Utility Registrants also include indirect construction costs including labor and related costs of departments associated with supporting construction activities. When appropriate, original cost also includes capitalized interest for Generation and Exelon Corporate and AFUDC for regulated property at ComEd, PECO, BGE, Pepco, DPL and ACE. The cost of repairs and maintenance, including planned major maintenance activities and minor replacements of property, is charged to maintenance expense as incurred. Third parties reimburse the Utility Registrants for all or a portion of expenditures for certain capital projects. Such contributions in aid of construction costs (CIAC) are recorded as a reduction to Property, plant and equipment. DOE SGIG funds reimbursed to PECO, BGE, Pepco and ACE have been accounted for as CIAC. For Generation, upon retirement, the cost of property is generally charged to accumulated depreciation in accordance with the composite method of depreciation. Upon replacement of an asset, the costs to remove the asset, net of salvage, are capitalized to gross plant when incurred as part of the cost of the newly-installed asset and recorded to depreciation expense over the life of the new asset. Removal costs, net of salvage, incurred for property that will not be replaced is charged to Operating and maintenance expense as incurred. For the Utility Registrants, upon retirement, the cost of property, net of salvage, is charged to accumulated depreciation in accordance with the composite method of depreciation. The Utility Registra

Variable Interest Entities (All

Variable Interest Entities (All Registrants)	12 Months Ended
	Dec. 31, 2016
Variable Interest Entity [Abstract]
Variable Interest Entity Disclosure [Text Block]	Variable Interest Entities (All Registrants) A VIE is a legal entity that possesses any of the following characteristics: an insufficient amount of equity at risk to finance its activities, equity owners who do not have the power to direct the significant activities of the entity (or have voting rights that are disproportionate to their ownership interest), or equity owners who do not have the obligation to absorb expected losses or the right to receive the expected residual returns of the entity. Companies are required to consolidate a VIE if they are its primary beneficiary, which is the enterprise that has the power to direct the activities that most significantly affect the entity’s economic performance. At December 31, 2016 , Exelon, Generation, BGE, PHI, and ACE collectively consolidated nine VIEs or VIE groups, for which the applicable Registrant was the primary beneficiary. At December 31, 2015 , Exelon, Generation and BGE collectively had seven consolidated VIEs or VIE groups and PHI and ACE had one consolidated VIE ( see Consolidated Variable Interest Entities below) . As of December 31, 2016 and December 31, 2015 , Exelon and Generation collectively had significant interests in eight other VIEs for which the applicable Registrant does not have the power to direct the entities’ activities and, accordingly, was not the primary beneficiary ( see Unconsolidated Variable Interest Entities below) . Consolidated Variable Interest Entities The carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in the Registrants' consolidated financial statements at December 31, 2016 and December 31, 2015 are as follows: December 31, 2016 December 31, 2015 Successor Predecessor Exelon (a)(b) Generation BGE PHI (b) ACE Exelon (a) Generation BGE PHI ACE Current assets $ 954 $ 916 $ 23 $ 14 9 $ 909 $ 881 $ 23 $ 12 $ 12 Noncurrent assets 8,563 8,525 3 35 23 8,009 8,004 3 18 18 Total assets $ 9,517 $ 9,441 $ 26 $ 49 $ 32 $ 8,918 $ 8,885 $ 26 $ 30 $ 30 Current liabilities $ 885 $ 802 $ 42 $ 42 37 $ 473 $ 387 $ 81 $ 48 $ 48 Noncurrent liabilities 2,713 2,612 — 101 89 2,927 2,884 41 124 124 Total liabilities $ 3,598 $ 3,414 $ 42 $ 143 $ 126 $ 3,400 $ 3,271 $ 122 $ 172 $ 172 _______________________ (a) Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity. (b) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. Except as specifically noted below, the assets in the table above are restricted for settlement of the VIE obligations and the liabilities in the table can only be settled using VIE resources. Exelon's, Generation's, BGE's, PHI's and ACE's consolidated VIEs consist of: RSB BondCo LLC. In 2007, BGE formed RSB BondCo LLC (BondCo), a special purpose bankruptcy remote limited liability company, to acquire and hold rate stabilization property and to issue and service bonds secured by the rate stabilization property. In June 2007, BondCo purchased rate stabilization property from BGE, including the right to assess, collect, and receive non-bypassable rate stabilization charges payable by all residential electric customers of BGE. These charges are being assessed in order to recover previously incurred power purchase costs that BGE deferred pursuant to Senate Bill 1. BGE has determined that BondCo is a VIE for which it is the primary beneficiary. As a result, BGE consolidates BondCo. BondCo’s assets are restricted and can only be used to settle the obligations of BondCo. Further, BGE is required to remit all payments it receives from customers for rate stabilization charges to BondCo. During 2016 , 2015 and 2014 , BGE remitted $86 million , $86 million and $85 million , respectively, to BondCo. BGE did not provide any additional financial support to BondCo during 2016 . Further, BGE does not have any contractual commitments or obligations to provide additional financial support to BondCo unless additional rate stabilization bonds are issued. The BondCo creditors do not have any recourse to the general credit of BGE in the event the rate stabilization charges are not sufficient to cover the bond principal and interest payments of BondCo. ACE Transition Funding . A special purpose entity formed by ACE for the purpose of securitizing authorized portions of ACE’s recoverable stranded costs through the issuance and sale of transition bonds. Proceeds from the sale of each series of transition bonds by ATF were transferred to ACE in exchange for the transfer by ACE to ATF of the right to collect a non-bypassable Transition Bond Charge from ACE customers pursuant to bondable stranded costs rate orders issued by the NJBPU in an amount sufficient to fund the principal and interest payments on transition bonds and related taxes, expenses and fees. During the three years ended December 31, 2016 , 2015 and 2014 , ACE transferred $60 million , $61 million and $55 million to ATF, respectively. Retail Gas Group. During 2009, Constellation formed two new entities, which now are part of Generation, and combined them with its existing retail gas activities into a retail gas entity group for the purpose of entering into a collateralized gas supply agreement with a third-party gas supplier. While Generation owns 100% of these entities, it has been determined that the retail gas entity group is a VIE because there is not sufficient equity to fund the group’s activities without the additional credit support that is provided in the form of a parental guarantee. Generation is the primary beneficiary of the retail gas entity group; accordingly, Generation consolidates the retail gas entity group as a VIE. The third-party gas supply arrangement is collateralized as follows: • the assets of the retail gas entity group must be used to settle obligations under the third-party gas supply agreement before it can make any distributions to Generation, • the third-party gas supplier has a collateral interest in all of the assets and equity of the retail gas entity group, and • Generation provides a $75 million parental guarantee to the third-party gas supplier and provides limited recourse to other third-party suppliers and customers in support of the retail gas group. Other than credit support provided by the parental guarantee, Exelon or Generation do not have any contractual or other obligations to provide additional financial support under the collateralized third-party gas supply agreement. The third-party gas supply creditors do not have any recourse to Exelon’s or Generation’s general credit other than the parental guarantee. Solar Project Entity Group. In 2011, Generation acquired all of the equity interests in Antelope Valley Solar Ranch One (Antelope Valley) from First Solar, Inc., a 242 -MW solar PV project in northern Los Angeles County, California. In addition, Generation owns a number of limited liability companies that build, own, and operate solar power facilities. While Generation owns 100% of these entities, it has been determined that certain of the individual solar project entities are VIEs because the entities require additional subordinated financial support in the form of a parental guarantee of debt, loans from the customers in order to obtain the necessary funds for construction of the solar facilities, or the customers absorb price variability from the entities through the fixed price power and/or REC purchase agreements. Generation is the primary beneficiary of the solar project entities that qualify as VIEs because Generation controls the design, construction, and operation of the solar power facilities. Generation provides operating and capital funding to the solar entities for ongoing construction, operations and maintenance of the solar power facilities and there is limited recourse related to Generation related to certain solar entities. In addition, these solar VIE entities have an aggregate amount of outstanding debt with third parties of $568 million , as of December 31, 2016 , for which the creditors have no recourse to Generation. For additional information on these project-specific financing arrangements refer to Note 14 — Debt and Credit Agreements . Retail Power and Gas Companies. In March 2014, Generation began consolidating retail power and gas VIEs for which Generation is the primary beneficiary as a result of energy supply contracts that give Generation the power to direct the activities that most significantly affect the economic performance of the entities. Generation does not have an equity ownership interest in these entities, but provides approximately $21 million in credit support for the retail power and gas companies for which Generation is the sole supplier of energy. These entities are included in Generation’s consolidated financial statements, and the consolidation of the VIEs do not have a material impact on Generation’s financial results or financial condition. Wind Project Entity Group . Generation owns and operates a number of wind project limited liability entities, the majority of which were acquired during 2010 with the acquisition of all of the equity interests of John Deere Renewables, LLC (now known as Exelon Wind). Generation has evaluated the significant agreements and ownership structures and the risks of each of its wind projects and underlying entities, and determined that certain of the entities are VIEs because either the projects have noncontrolling equity interest holders that absorb variability from the wind projects, or the customers absorb price variability from the entities through the fixed price power and/or REC purchase agreements. Generation is the primary beneficiary of the wind project entities that qualify as VIEs because Generation controls the design, construction, and operation of the wind generation facilities. In December 2016, Generation sold approximately 71% of its equity interest in one of its wind projects that was previously consolidated under the voting interest model to a tax equity investor. The wind project was evaluated and it was determined to be a VIE because the company has a similar structure to a limited partnership and the limited partners do not have kick-out rights with respect to the general partner. While Generation is the minority interest holder, Generation is the primary beneficiary, because Generation manages the day-to-day activities of the entity. Therefore, the entity continues to be consolidated by Generation. While Generation owns 100% of the majority of the wind project entities, six of the projects have noncontrolling equity interests of 1% held by third parties and one of the projects has noncontrolling equity interests of approximately 71%. Regarding the projects with noncontrolling equity interests of 1% held by third parties, Generation’s current economic interests in five of these projects is significantly greater than its stated contractual governance rights and all of these projects have reversionary interest provisions that provide the noncontrolling interest holder with a purchase option, certain of which are considered bargain purchase prices, which, if exercised, transfers ownership of the projects to the noncontrolling interest holder upon either the passage of time or the achievement of targeted financial returns. The ownership agreements with the noncontrolling interests state that Generation is to provide financial support to the projects in proportion to its current 99% economic interests in the projects. Generation provides operating and capital funding to the wind project entities for ongoing construction, operations and maintenance of the wind power and there is limited recourse to Generation related to certain wind project entities. However, no additional support to these projects beyond what was contractually required has been provided during 2016. As of December 31, 2016 , the carrying amount of the assets and liabilities that are consolidated as a result of Generation being the primary beneficiary of the wind VIE entities primarily relates to the wind generating assets, PPA intangible assets and working capital amounts. Other Generating Facilities. During the second quarter of 2015, Generation formed a limited liability company to build, own, and operate a backup generator. While Generation owns 100% of the backup generator company, it was determined that the entity is a VIE because the customer absorbs price variability from the entity through the fixed price backup generator agreement. Generation provides operating and capital funding to the backup generator company. Generation also owns 90% of a biomass fueled, combined heat and power company. In the second quarter of 2015, the entity was deemed to be a VIE because the entity requires additional subordinated financial support in the form of a parental guarantee provided by Generation for up to $ 275 million in support of the payment obligations related to the Engineering, Procurement and Construction contract for the facility in support of one of its other generating facilities (see Note 14 - Debt and Credit Agreements for additional details on Albany Green Energy, LLC). In addition to the parental guarantee, Generation provides operating and capital funding to the biomass fueled, combined heat and power company. Generation is the primary beneficiary of both entities since Generation has the power to direct the activities that most significantly affect the economic performance of the entities. CENG. Through March 31, 2014, CENG was operated as a joint venture with EDF and was governed by a board of ten directors, five of which were appointed by Generation and five by EDF. CENG was designed to operate under joint and equal control of Generation and EDF through the Board of Directors, subject to the Chairman of the Board’s final decision making authority on certain special matters; therefore, CENG was not subject to VIE guidance. Accordingly, Generation’s 50.01% interest in CENG was accounted for as an equity method investment. On April 1, 2014, Generation, CENG, and subsidiaries of CENG executed the Nuclear Operating Services Agreement (NOSA) pursuant to which Generation now conducts all activities associated with the operations of the CENG fleet and provides corporate and administrative services to CENG and the CENG fleet for the remaining life of the CENG nuclear plants as if they were a part of the Generation nuclear fleet, subject to the CENG member rights of EDF. As a result of executing the NOSA, CENG now qualifies as a VIE due to the disproportionate relationship between Generation’s 50.01% equity ownership interest and its role in conducting the operational activities of CENG and the CENG fleet conveyed through the NOSA. Further, since Generation is conducting the operational activities of CENG and the CENG fleet, Generation qualifies as the primary beneficiary of CENG and, therefore, is required to consolidate the financial position and results of operations of CENG. On April 1, 2014, Exelon and Generation derecognized Generation’s equity method investment in CENG and reflected all assets, liabilities, and the EDF noncontrolling interests in CENG at fair value on the consolidated balance sheets of Exelon and Generation, resulting in the recognition of a $261 million gain in their respective Consolidated Statements of Operations and Comprehensive Income for the year ended December 31, 2014. Generation and Exelon, where indicated, provide the following support to CENG (see Note 5 — Investment in Constellation Energy Nuclear Group, LLC and Note 27 — Related Party Transactions for additional information regarding Generation's and Exelon’s transactions with CENG): • under the NOSA, Generation conducts all activities related to the operation of the CENG nuclear generation fleet owned by CENG subsidiaries (the CENG fleet) and provides corporate and administrative services for the remaining life and decommissioning of the CENG nuclear plants as if they were a part of the Generation nuclear fleet, subject to the CENG member rights of EDF, • under the Power Services Agency Agreement (PSAA), Generation provides scheduling, asset management, and billing services to the CENG fleet for the remaining operating life of the CENG nuclear plants, • under power purchase agreements with CENG, Generation purchased or will purchase 50.01% of the available output generated by the CENG nuclear plants not subject to other contractual agreements from January 2015 through the end of the operating life of each respective plant. However, pursuant to amendments dated March 31, 2015, the energy obligations under the Ginna Nuclear Power Plant (Ginna) PPAs have been suspended during the term of the Reliability Support Services Agreement (RSSA) (see Note 3 — Regulatory Matters for additional details), • Generation provided a $400 million loan to CENG. As of December 31, 2016 , the remaining obligation is $316 million , including accrued interest, which reflects the principal payment made in January 2015, • Generation executed an Indemnity Agreement pursuant to which Generation agreed to indemnify EDF against third-party claims that may arise from any future nuclear incident (as defined in the Price-Anderson Act) in connection with the CENG nuclear plants or their operations. Exelon guarantees Generation’s obligations under this Indemnity Agreement. (See Note 24 — Commitments and Contingencies for more details), • in connection with CENG’s severance obligations, Generation reimbursed CENG for a total of approximately $6 million of the severance benefits paid from 2014 through 2016. The final reimbursement was made in 2016, and there was no remaining obligation as of December 31, 2016 . • Generation and EDF share in the $637 million of contingent payment obligations for the payment of contingent retrospective premium adjustments for the nuclear liability insurance, • Generation provides a guarantee of approximately $7 million associated with hazardous waste management facilities and underground storage tanks. In addition, EDF executed a reimbursement agreement that provides reimbursement to Exelon for 49.99% of any amounts paid by Generation under this guarantee, • Generation and EDF are the members-insured with Nuclear Electric Insurance Limited and have assigned the loss benefits under the insurance and the NEIL premium costs to CENG and guarantee the obligations of CENG under these insurance programs in proportion to their respective member interests (See Note 24 — Commitments and Contingencies for more details), and • Exelon has executed an agreement to provide up to $245 million to support the operations of CENG as well as a $165 million guarantee of CENG’s cash pooling agreement with its subsidiaries. 2015 ESA Investco, LLC. In June 2015, 2015 ESA Investco, LLC, then a wholly owned subsidiary of Generation, entered into an arrangement to purchase a 90% equity interest and 99% of the tax attributes of another distributed energy company. In November 2015, Generation sold 69% of its equity interest in 2015 ESA Investco, LLC to a tax equity investor. Generation and the tax equity investor will contribute up to a total of $250 million of equity incrementally from inception through the first quarter of 2017 in proportion to their ownership interests, which is up to $172 million for the tax equity investor and up to $78 million for Generation (see Note 24 — Commitments and Contingencies for more details). The investment in the distributed energy company was evaluated, and it was determined to be a VIE for which Generation is not the primary beneficiary (see additional details in the Unconsolidated Variable Interest Entities section below). As of December 31, 2015, Generation consolidated 2015 ESA Investco, LLC under the voting interest model. Pursuant to the new consolidation guidance effective January 1, 2016, 2015 ESA Investco, LLC meets the definition of a VIE because the company has a similar structure to a limited partnership and the limited partners do not have kick-out rights with respect to the general partner. Under VIE guidance, Generation is the primary beneficiary; therefore, the entity continues to be consolidated. For each of the consolidated VIEs, except as otherwise noted: • the assets of the VIEs are restricted and can only be used to settle obligations of the respective VIE; • Exelon, Generation, BGE, PHI and ACE did not provide any additional material financial support to the VIEs; • Exelon, Generation, BGE, PHI and ACE did not have any material contractual commitments or obligations to provide financial support to the VIEs; and • the creditors of the VIEs did not have recourse to Exelon’s, Generation’s, BGE’s, PHI's or ACE's general credit. As of December 31, 2016 and December 31, 2015 , ComEd, PECO, Pepco and DPL do not have any material consolidated VIEs. Assets and Liabilities of Consolidated VIEs Included within the balances above are assets and liabilities of certain consolidated VIEs for which the assets can only be used to settle obligations of those VIEs, and liabilities that creditors, or beneficiaries, do not have recourse to the general credit of the Registrants. As of December 31, 2016 and December 31, 2015 , these assets and liabilities primarily consisted of the following: December 31, 2016 December 31, 2015 Successor Predecessor Exelon (a)(b) Generation BGE PHI (b) ACE Exelon (a) Generation BGE PHI ACE Cash and cash equivalents $ 150 $ 150 $ — $ — $ — $ 164 $ 164 $ — $ — $ — Restricted cash 59 27 23 9 9 100 77 23 12 12 Accounts receivable, net Customer 371 371 — — — 219 219 — — — Other 48 48 — — — 43 43 — — — Mark-to-market derivatives assets 31 31 — — — 140 140 — — — Inventory Materials and supplies 199 199 — — — 181 181 — — — Other current assets 50 44 — 5 — 35 30 — — — Total current assets 908 870 23 14 9 882 854 23 12 12 Property, plant and equipment, net 5,415 5,415 — — — 5,160 5,160 — — — Nuclear decommissioning trust funds 2,185 2,185 — — — 2,036 2,036 — — — Goodwill 47 47 — — — 47 47 — — — Mark-to-market derivatives assets 23 23 — — — 53 53 — — — Other noncurrent assets 315 277 3 35 23 90 85 3 18 18 Total noncurrent assets 7,985 7,947 3 35 23 7,386 7,381 3 18 18 Total assets $ 8,893 $ 8,817 $ 26 $ 49 $ 32 $ 8,268 $ 8,235 $ 26 $ 30 $ 30 Long-term debt due within one year $ 181 $ 99 $ 41 $ 40 $ 35 $ 111 $ 27 $ 79 $ 46 $ 46 Accounts payable 269 269 — — — 216 216 — — — Accrued expenses 119 116 1 2 2 115 113 2 2 2 Mark-to-market derivative liabilities 60 60 — — — 5 5 — — — Unamortized energy contract liabilities 15 15 — — — 12 12 — — — Other current liabilities 30 30 — — — 13 13 — — — Total current liabilities 674 589 42 42 37 472 386 81 48 48 Long-term debt 641 540 — 101 89 666 623 41 124 124 Asset retirement obligations 1,904 1,904 — — — 1,999 1,999 — — — Pension obligation (c) 9 9 — — — 9 9 — — — Unamortized energy contract liabilities 22 22 — — — 39 39 — — — Other noncurrent liabilities 106 106 — — — 79 79 — — — Noncurrent liabilities 2,682 2,581 — 101 89 2,792 2,749 41 124 124 Total liabilities $ 3,356 $ 3,170 $ 42 $ 143 $ 126 $ 3,264 $ 3,135 $ 122 $ 172 $ 172 ___________ (a) Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity. (b) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. (c) Includes the CNEG retail gas pension obligation, which is presented as a net asset balance within the Prepaid pension asset line item on Generation’s balance sheet. See Note 17 - Retirement Benefits for additional details. Unconsolidated Variable Interest Entities Exelon’s and Generation’s variable interests in unconsolidated VIEs generally include equity investments and energy purchase and sale contracts. For the equity investments, the carrying amount of the investments is reflected on Exelon’s and Generation’s Consolidated Balance Sheets in Investments. For the energy purchase and sale contracts (commercial agreements), the carrying amount of assets and liabilities in Exelon’s and Generation’s Consolidated Balance Sheets that relate to their involvement with the VIEs are predominately related to working capital accounts and generally represent the amounts owed by, or owed to, Exelon and Generation for the deliveries associated with the current billing cycles under the commercial agreements. Further, Exelon and Generation have not provided material debt or equity support, liquidity arrangements or performance guarantees associated with these commercial agreements. As of December 31, 2016 and 2015 , Exelon and Generation had significant unconsolidated variable interests in eight VIEs for which Exelon or Generation, as applicable, was not the primary beneficiary; including certain equity method investments and certain commercial agreements. Exelon and Generation only include unconsolidated VIEs that are individually material in the tables below. However, Generation has several individually immaterial VIEs that in aggregate represent a total investment of $18 million . These immaterial VIEs are equity and debt securities in energy development companies. The maximum exposure to loss related to these securities is limited to the $ 18 million included in Investments on Exelon’s and Generation’s Consolidated Balance Sheets . The following tables present summary information about Exelon and Generation’s significant unconsolidated VIE entities: December 31, 2016 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 638 $ 567 $ 1,205 Total liabilities (a) 215 287 502 Exelon's ownership interest in VIE (a) — 248 248 Other ownership interests in VIE (a) 423 32 455 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 264 264 Contract intangible asset 9 — 9 Debt and payment guarantees — 3 3 Net assets pledged for Zion Station decommissioning (b) 9 — 9 December 31, 2015 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 263 $ 164 $ 427 Total liabilities (a) 22 125 147 Exelon's ownership interest in VIE (a) — 11 11 Other ownership interests in VIE (a) 241 28 269 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 21 21 Contract intangible asset 9 — 9 Debt and payment guarantees — 3 3 Net assets pledged for Zion Station decommissioning (b) 17 — 17 ___________________ (a) These items represent amounts on the unconsolidated VIE balance sheets, not on Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs. (b) These items represent amounts on Exelon’s and Generation’s Consolidated Balance Sheets related to the asset sale agreement with ZionSolutions, LLC. The net assets pledged for Zion Station decommissioning includes gross pledged assets of $113 million and $206 million as of December 31, 2016 and December 31, 2015 , respectively; offset by payables to ZionSolutions LLC of $104 million and $189 million as of December 31, 2016 and December 31, 2015 , respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE. For each unconsolidated VIE, Exelon and Generation assessed the risk of a loss equal to their maximum exposure to be remote and, accordingly Exelon and Generation have not recognized a liability associated with any portion of the maximum exposure to loss. In addition, there are no agreements with, or commitments by, third parties that would materially affect the fair value or risk of their variable interests in these variable interest entities. The Registrants' unconsolidated VIEs consist of: Energy Purchase and Sale Agreements. Generation has several energy purchase and sale agreements with generating facilities. Generation has evaluated the significant agreements, ownership structures and risks of each entity, and determined that certain of the entities are VIEs because the entity absorbs risk through the sale of fixed price power and renewable energy credits. Generation has reviewed the entities and has determined that Generation is not the primary beneficiary of the VIEs because Generation does not have the power to direct the activities that most significantly impact the VIEs economic performance. ZionSolutions . Generation has an asset sale agreement with EnergySolutions, Inc. and certain of its subsidiaries, including ZionSolutions, LLC (ZionSolutions), which is further discussed in Note 16 — Asset Retirement Obligations . Under this agreement, ZionSolutions can put the assets and liabilities back to Generation when decommissioning activities under the asset sale agreement are complete. Generation has evaluated this agreement and determined that, through the put option, it has a variable interest in ZionSolutions but is not the primary beneficiary. As a result, Generation has concluded that consolidation is not required. Other than the asset sale agreement, Exelon and Generation do not have any contractual or other obligations to provide additional financial support and ZionSolutions’ creditors do not have any recourse to Exelon’s or Generation’s general credit. Investment in Energy Development Projects, Distributed Energy Companies, and Energy Generating Facilities. Generation has several equity investments in energy development projects and energy generating facilities. Generation has evaluated the significant agreements, ownership structures and risks of each of its equity investments, and determined that certain of the entities are VIEs because the entity has an insufficient amount of equity at risk to finance its activities, Generation guarantees the debt of the entity, provides equity support, or provides operating services to the entity. Generation has reviewed the entities and has determined that Generation is not the primary beneficiary of the entities that qualify as VIEs because Generation does not have the power to direct the activities that most significantly impact the VIEs economic performance. In July 2014, Generation entered into an arrangement to purchase a 90% equity interest and 90% of the tax attributes of a distributed energy company. Generation’s total equity commitment in this arrangement was $ 85 million and was paid incrementally over an approximate two year period (see Note 24 - Commitments and Contingencies for additional details). This arrangement did not meet the definition of a VIE and was recorded as an equity method investment. However, pursuant to the new consolidation guidance effective as of January 1, 2016 for the Registrants, the distributed energy company meets the definition of a VIE because the company has a similar structure to a limited partnership and the limited partners do not have kick-out rights of the general partner. (For additional details related to the new consolidation guidance, see Note 1 - Significant Accounting Policies .) Generation is not the primary beneficiary; therefore, the investment continues to be recorded using the equity method. In June 2015, 2015 ESA Investco, LLC, then a wholly owned subsidiary of Generation, entered into an arrangement to purchase a 90% equity interest and 99% of the tax attributes of another distributed energy company. Separate from the equity investment, Generation provided $ 27 million in cash to the other (10%) equity holder in the distributed energy company in exchange for a convertible promissory note. In November 2015, Generation sold 69% of its equity interest in 2015 ESA Investco, LLC to a tax equity investor. Generation and the tax equity investor will contribute up to a total of $ 250 million of equity incrementally through the first quarter of 2017 in proportion to their ownership interests, which is up to $ 172 million for the tax equity investor and up to $ 78 million for Generation (see Note 24 - Commitments and Contingencies for additional details). Generation and the tax equity investor provide a parental guarantee of up to $ 275 million in proportion to their ownership interests in support of 2015 ESA Investco, LLC's obligation to make equity contributions to the distributed energy company. The investment in the distributed energy company was evaluated and it was determined to be a VIE for which Generation is not the primary beneficiary. See additional details in the Consolidated Variable Interest Entities section above. Both distributed energy companies from the 2015 and 2014 arrangements are considered related parties. ComEd, PECO and BGE The financing trust of ComEd, ComEd Financing III, the financing trusts of PECO, PECO Trust III and PECO Trust IV, and the financing trust of BGE, BGE Capital Trust II, ar

Regulatory Matters (All Registr

Regulatory Matters (All Registrants)	12 Months Ended
	Dec. 31, 2016
Regulated Operations [Abstract]
Regulatory Matters (All Registrants)	3 . Regulatory Matters (All Registrants) The following matters below discuss the current status of material regulatory and legislative proceedings of the Registrants. Illinois Regulatory Matters Energy Infrastructure Modernization Act (Exelon and ComEd). Background Since 2011, ComEd’s electric distribution rates are established through a performance-based formula rate, pursuant to EIMA. EIMA also provides a structure for substantial capital investment by utilities to modernize Illinois’ electric utility infrastructure. Participating utilities are required to file an annual update to the performance-based formula rate on or before May 1, with resulting rates effective in January of the following year. This annual electric distribution formula rate update is based on prior year actual costs and current year projected capital additions (initial revenue requirement). The update also reconciles any differences between the revenue requirement in effect for the prior year and actual costs incurred for that year (annual reconciliation). See Annual Electric Distribution Filings below for further details. Throughout each year, ComEd records regulatory assets or regulatory liabilities and corresponding increases or decreases to Operating revenues for any differences between the revenue requirement in effect and ComEd’s best estimate of the revenue requirement expected to be approved by the ICC for that year’s reconciliation. As of December 31, 2016 , and December 31, 2015 , ComEd had a regulatory asset associated with the electric distribution formula rate of $188 million and $189 million , respectively. The regulatory asset associated with electric distribution formula rate is amortized to Operating revenues in ComEd's Consolidated Statement of Operations and Comprehensive Income as the associated amounts are recovered through rates. Participating utilities are also required to file an annual update on their AMI implementation progress. On April 1, 2016, ComEd filed an annual progress report on its AMI Implementation Plan with the ICC, which allows for the installation of more than four million smart meters throughout ComEd's service territory through 2018. To date, approximately three million smart meters have been installed in the Chicago area. Pursuant to EIMA, ComEd annually contributes $ 4 million for customer education for as long as the AMI Deployment Plan remains in effect. Additionally, ComEd contributed $ 10 million annually through 2016 to fund customer assistance programs for low-income customers, which are not recoverable through rates. Annual Electric Distribution Filings For each of the following years, the ICC approved the following total increases/(decreases) in ComEd's electric distributions formula rate filings: Annual Electric Distribution Filings 2016 2015 2014 ComEd's requested total revenue requirement increase (decrease) $ 138 $ (50 ) $ 269 Final ICC Order Initial revenue requirement increase $ 134 $ 85 $ 160 Annual reconciliation (decrease) increase (7 ) (152 ) 72 Total revenue requirement increase (decrease) $ 127 (a) $ (67 ) $ 232 Allowed Return on Rate Base: Initial revenue requirement 6.71 % 7.05 % 7.06 % Annual reconciliation 6.69 % 7.02 % 7.04 % Allowed ROE: Initial revenue requirement 8.64 % 9.14 % 9.25 % Annual reconciliation 8.59 % (b) 9.09 % (b) 9.20 % (b) Effective date of rates January 2017 January 2016 January 2015 __________________ (a) On December 20, 2016, the ICC granted ComEd's and other parties' joint application for rehearing on the impact that changing ComEd’s OSHA recordable rate for 2014 and 2015 has on the revenue requirement approved in this order. ComEd has proposed that the 2016 total electric distribution revenue requirement be reduced by $18 million which would be refunded to customers in 2017. (b) Includes a reduction of 5 basis points for a reliability performance metric penalty. Illinois Future Energy Jobs Act (Exelon, Generation, and ComEd). Background On December 7, 2016, FEJA was signed into law by the Governor of Illinois. FEJA is effective June 1, 2017, and includes, among other provisions, (1) a ZES providing compensation for certain nuclear-powered generating facilities, (2) an extension of and certain adjustments to ComEd’s electric distribution formula rate, (3) new cumulative persisting annual energy efficiency MWh savings goals for ComEd, (4) revisions to the Illinois RPS requirements, (5) provisions for adjustments to or termination of FEJA programs if the average impact on ComEd’s customer rates exceeds specified limits, (6) revisions to the existing net metering statute to (i) mandate net metering for community generation projects, and establish billing procedures for subscribers to those projects, (ii) provide immediately for netting at the energy-only rate for nonresidential customers, and (iii) transition from netting at the full retail rate to the energy-only rate for certain residential net metering customers once the net meter customer load equals 5% of total peak demand supplied in the previous year and (7) support for low income rooftop and community solar programs . Zero Emission Standard FEJA includes a ZES that provides compensation through the procurement of ZECs targeted at preserving the environmental attributes of zero-emissions nuclear-powered generating facilities that meet specific eligibility criteria. ZES will have a 10-year duration extending through May 31, 2027. Eligible generators may participate in a procurement event overseen by the Illinois Power Agency and selected generators will directly contract with Illinois utilities for the procurement of the ZECs based upon the number of MWh produced by the eligible facilities, subject to specified annual caps. The ZEC price will be based upon the current social cost of carbon as determined by the federal government and is initially established at $16.50 per MWh of production, subject to future adjustments based on specified escalation and pricing adjustment mechanisms designed to lower the ZEC price based on increases in underlying energy and capacity prices. I llinois utilities, including ComEd, will be required to purchase from eligible nuclear facilities an amount of ZECs equivalent to 16% of the actual amount of electricity delivered in 2014. ComEd will recover all costs associated with purchasing ZECs through a new rate rider, which will provide for an annual reconciliation and true-up to actual costs incurred by ComEd to purchase ZECs, with any difference to be credited to or collected from ComEd’s retail customers in subsequent periods. See Note 9 - Early Nuclear Plant Retirements for the impacts of the provisions above on Generation’s Consolidated Balance Sheets and Consolidated Statements of Operations and Comprehensive Income. The provisions do not impact ComEd’s Consolidated Balance Sheets, Consolidated Statements of Operations and Comprehensive Income or Consolidated Statements of Cash Flows until 2017. ComEd Electric Distribution Rates FEJA extends the sunset date for ComEd’s performance-based electric distribution formula rate from 2019 to the end of 2022, allows ComEd to revise the electric distribution formula rate to eliminate the ROE collar, and allows ComEd to implement a decoupling tariff if the electric distribution formula rate is terminated at any time. ComEd will revise its electric distribution formula rate to eliminate the ROE collar, which will eliminate any unfavorable or favorable impacts of weather or load from ComEd’s electric distribution formula rate revenues beginning with the reconciliation filed in 2018 for the 2017 calendar year. ComEd will begin reflecting the impacts of this change in its electric distribution services costs regulatory asset or liability beginning in 2017. FEJA requires ComEd to make non-recoverable contributions to low income energy assistance programs of $10 million per year for 5 years as long as the electric distribution formula rate remains in effect. With the exception of these contributions, ComEd will recover from customers, subject to certain caps explained below, the costs it incurs pursuant to FEJA either through its electric distribution formula rate or other recovery mechanisms. Energy Efficiency Existing Illinois law requires ComEd to implement cost-effective energy efficiency measures and, for a 10-year period ending May 31, 2018, cost-effective demand response measures to reduce peak demand by 0.1% over the prior year for eligible retail customers. Beginning January 1, 2018, FEJA provides for new cumulative annual energy efficiency MWh savings goals for ComEd, which are designed to achieve 21.5% of cumulative persisting annual MWh savings by 2030, as compared to the deemed baseline of 88 million MWhs of electric power and energy sales. FEJA, deems the cumulative persisting annual MWh savings to be 6.6% from 2012 through the end of 2017. ComEd expects to spend approximately $250 million to $400 million annually from 2017 through 2030 to achieve these energy efficiency MWh savings goals. In addition, FEJA extends the peak demand reduction requirement from 2018 to 2026. Because the new requirements apply beginning in 2018, FEJA extends the existing energy efficiency plans, which were due to end on May 31, 2017, through December 31, 2017. FEJA also exempts customers with demands over 10 MW from energy efficiency plans and requirements beginning June 1, 2017. FEJA allows ComEd to cancel its existing energy efficiency rate rider and replace it with an energy efficiency formula rate, and to defer energy efficiency costs (except for any voltage optimization costs which will be recovered through the electric distribution formula rate) as a separate regulatory asset that will be recovered through the energy efficiency formula rate over the weighted average useful life, as approved by the ICC, of the related energy efficiency measures. ComEd will earn a return on the energy efficiency regulatory asset at a rate equal to its weighted average cost of capital, which is based on a year-end capital structure and calculated using the same methodology applicable to ComEd’s electric distribution formula rate. Through December 31, 2030, the return on equity that ComEd earns on its energy efficiency regulatory asset is subject to a maximum downward or upward adjustment of 200 basis points if ComEd’s cumulative persisting annual MWh savings falls short of or exceeds specified percentage benchmarks of its annual incremental savings goal. ComEd will be required to file an update to its energy efficiency formula rate on or before June 1 each year, with resulting rates effective in January of the following year. The annual update will be based on projected current year energy efficiency costs and the related projected year-end regulatory asset balance less any related deferred taxes. The update will also include a reconciliation of any differences between the revenue requirement in effect for the prior year and the revenue requirement based on actual prior year costs and year-end energy efficiency regulatory asset balances less any related deferred taxes. ComEd expects to cancel its existing energy efficiency rider, at which time it must perform a reconciliation of revenues and costs incurred through the cancellation date and issue a one-time credit on retail customers' bills for any over-recoveries. As of December 31, 2016, ComEd’s over-recoveries associated with its existing energy efficiency rider of $141 million were reflected in Current regulatory liabilities on Exelon’s and ComEd’s Consolidated Balance Sheets. As a result, ComEd expects to provide credits to customers in 2017 to address this over-recovery. Renewable Portfolio Standard Existing Illinois law requires ComEd to purchase each year an increasing percentage of renewable energy resources for the customers for which it supplies electricity. This obligation is satisfied through the procurement of renewable energy credits (RECs). FEJA revises the Illinois RPS to require ComEd to procure RECs for all retail customers by June 2019, regardless of the customers’ electricity supplier, and provides support for low-income rooftop and community solar programs, which will be funded by the existing Renewable Energy Resources Fund and ongoing RPS collections. ComEd will recover all costs associated with purchasing RECs through rate riders, which will provide for a reconciliation and true-up to actual costs, with any difference between revenues and expenses to be credited to or collected from ComEd’s retail customers in subsequent periods. The first reconciliation and true-up for RECs will cover revenues and costs for the four year period beginning June 1, 2017 through May 31, 2021. Subsequently, the RPS rate rider will provide for an annual reconciliation and true-up. Customer Rate Increase Limitations FEJA includes provisions intended to limit the average impact on ComEd customer rates for recovery of costs incurred under FEJA as follows: (1) for a typical ComEd residential customer, the average impact must be less than $0.25 cents per month, (2) for nonresidential customers with a peak demand less than 10 MW, the average annual impact must be less than 1.3% of the average amount paid per kWh for electric service by Illinois commercial retail customers during 2015, and (3) for nonresidential customers with a peak demand greater than 10 MW, the average annual impact must be less than 1.3% of the average amount paid per kWh for electric service by Illinois industrial retail customers during 2015. By June 30, 2017, ComEd must submit a 10-year projection to the ICC of customer rate impacts for residential customers and nonresidential customers with a peak demand less than 10 MW . Thereafter, beginning in 2018, ComEd must submit a report to the ICC for residential customers and nonresidential customers with a peak demand less than 10 MW by February 15th and June 30th of each year, respectively. For nonresidential customers with a peak demand greater than 10 MW, ComEd must submit a report to the ICC by May 1 of each year if a rate reduction will be necessary in the following year. For residential customers, the reports will include the actual costs incurred under FEJA during the preceding year and a rolling 10-year customer rate impact projection. The reports for nonresidential customers with a peak demand less than 10 MW will also include the actual costs incurred under FEJA during the preceding year, as well as the average annual rate increase from January 1, 2017 through the end of the preceding year and the average annual rate increase projected for the remainder of the 10-year period. If the projected residential customer or nonresidential customer with a peak demand less than 10 MW rate increase exceeds the limitations during the first four years, ComEd is required to decrease costs associated with FEJA investments, including reductions to ZEC contract quantities. If the projected residential customer or nonresidential customer with a peak demand less than 10 MW rate increase exceeds the limitations during the last six years, ComEd is required to demonstrate how it will reduce FEJA investments to ensure compliance. If the actual residential customer or nonresidential customer with a peak demand less than 10 MW rate increase exceeds the limitations for any one year, ComEd is required to submit a corrective action plan to decrease future year costs to reduce customer rates to ensure future compliance. If the actual residential customer or nonresidential customer rate exceeds the limitations for two consecutive years, ComEd can offer to credit customers for amounts billed in excess of the limitations or ComEd can terminate FEJA investments. If ComEd chooses to terminate FEJA investments, the ICC shall order termination of ZEC contracts and further initiate proceedings to reduce energy efficiency savings goals and terminate support for low-income rooftop and community solar programs . ComEd is allowed to fully recover all costs incurred as of and up to the date of the programs’ termination. For the energy efficiency formula, ComEd will record a regulatory asset or liability and corresponding increase or decrease to Operating revenues for any differences between the revenue requirement in effect and ComEd’s best estimate of the revenue requirement expected to be approved by the ICC for that year’s reconciliation. For the other rate riders to be established under FEJA, ComEd will record a regulatory asset or liability for any differences between revenues and incurred expenses. FEJA did not have any impacts on ComEd’s Consolidated Statements of Operations and Comprehensive Income or Consolidated Statements of Cash Flows in 2016. Illinois Procurement Proceedings (Exelon, Generation and ComEd). ComEd is permitted to recover its electricity procurement costs from retail customers without mark-up. Since June 2009, the IPA designs, and the ICC approves, an electricity supply portfolio for ComEd and the IPA administers a competitive process under which ComEd procures its electricity supply from various suppliers, including Generation. As of December 31, 2016, ComEd has completed all required ICC-approved procurements as called for by the IPA Procurement Plan’s timeline. Energy Efficiency and Renewable Energy Resources (Exelon and ComEd). In accordance with legislation in effect on December 31, 2016, the IPA's Procurement Plans include the procurement of cost-effective renewable energy resources in amounts that equal or exceed a minimum target percentage of the total electricity that each electric utility supplies to its eligible retail customers. The June 1, 2016 target renewable energy resources obligation for the utilities was at least 11.5% . This obligation increases by at least 1.5% each year thereafter to an ultimate target of at least 25% by June 1, 2025. All goals are subject to rate impact criteria set forth by Illinois legislation. As of December 31, 2016 , ComEd had purchased renewable energy resources or equivalents, such as RECs, in accordance with the IPA Procurement Plan. ComEd currently retires all RECs upon transfer and acceptance. ComEd is permitted to recover procurement costs of RECs from retail customers without mark-up through rates. In accordance with FEJA that takes effect on June 1, 2017, beginning with the plan or plans to be implemented in the 2017 delivery year, the IPA shall develop a long term renewable resources procurement plan (LT Plan). The RPS target percentages for the overall service territory have not changed through June 1, 2025 although FEJA extended the 25% RPS target to delivery years after 2025. Currently, each RES and each utility is responsible for the renewable resource obligation of the customers it supplies power for. Over time, this will change and the utility will procure renewable resources based on the retail load of substantially all customers in its service territory. For the delivery year beginning June 1, 2017, the LT Plan shall include cost effective renewable energy resources procured by the utility for the retail load the utility supplies and for 50% of the retail customer load supplied by Retail Electric Suppliers in the utility service territory on February 28, 2017. Utility procurement for RES supplied retail customer load will increase to 75% June 1, 2018 and to 100% beginning June 1, 2019. Grand Prairie Gateway Transmission Line (Exelon and ComEd). On December 2, 2013, ComEd filed a request to obtain the ICC’s approval to construct a 60-mile overhead 345kV transmission line that traverses Ogle, DeKalb, Kane and DuPage Counties in Northern Illinois. On October 22, 2014, the ICC issued an Order approving ComEd’s request. The City of Elgin and certain other parties each filed an appeal of the ICC Order in the Illinois Appellate Court for the Second District. ComEd then reached a settlement of the appeal filed by all parties except Elgin. On March 31, 2016, the Illinois Appellate Court issued its opinion affirming the ICC’s grant of a certificate to ComEd to construct and operate the line. Elgin did not seek further review of the Illinois Appellate Court decision. On May 28, 2014, in a separate proceeding, FERC issued an order granting ComEd’s request to include 100% of the capital costs recorded to construction work in progress during construction of the line in ComEd’s transmission rate base. If the project is cancelled or abandoned for reasons beyond ComEd’s control, FERC approved the ability for ComEd to recover 100% of its prudent costs incurred after May 21, 2014 and 50% of its costs incurred prior to May 21, 2014 in ComEd’s transmission rate base. The costs incurred for the project prior to May 21, 2014 were immaterial. ComEd has acquired the necessary land rights across the project route through voluntary transactions. ComEd began construction of the line during 2015 with an expected in-service date of June 2017. FutureGen Industrial Alliance, Inc (Exelon and ComEd). During 2013, the ICC approved, and directed ComEd and Ameren (the Utilities) to enter into 20-year sourcing agreements with FutureGen Industrial Alliance, Inc (FutureGen), under which FutureGen will retrofit and repower an existing plant in Morgan County, Illinois to a 166 MW near zero emissions coal-fueled generation plant, with an assumed commercial operation date in 2017. ComEd executed the sourcing agreement with FutureGen in accordance with the ICC’s order. The order also directed ComEd and Ameren to recover these costs from their electric distribution customers through the use of a tariff, regardless of whether they purchase electricity from ComEd or Ameren, or from competitive electric generation suppliers. In February 2015, the DOE suspended funding for the cost development of FutureGen. On January 13, 2016, FutureGen informed the Illinois Supreme Court that it had ceased all development efforts on the FutureGen project. In February 2016, FutureGen terminated its sourcing agreement with ComEd. On May 19, 2016, the Illinois Supreme Court dismissed the matter as moot. As a result, ComEd is under no further obligation under this agreement. Pennsylvania Regulatory Matters 2015 Pennsylvania Electric Distribution Rate Case (Exelon and PECO). On March 27, 2015, PECO filed a petition with the PAPUC requesting an increase of $190 million to its annual service revenues for electric delivery, which requested an ROE of 10.95% . On September 10, 2015, PECO and interested parties filed with the PAPUC a petition for joint settlement for an increase of $127 million in annual distribution service revenue. No overall ROE was specified in the settlement. On December 17, 2015, the PAPUC approved the settlement of PECO’s electric distribution rate case, which included the approval of the In-Program Arrearage Forgiveness ("IPAF") Program. The approved electric delivery rates became effective on January 1, 2016. The IPAF Program provides for forgiveness of a portion of the eligible arrearage balance of its low-income Customer Assistance Program (CAP) accounts receivable at program inception. The forgiveness will be granted to the extent CAP customers remain current over the duration of the five-year payment agreement term. The Settlement guarantees PECO’s recovery of two-thirds of the arrearage balance through a combination of customer payments and rate recovery, including through future rates cases if necessary. The remaining one-third of the arrearage balance has been absorbed by PECO through bad debt expense on its Consolidated Statements of Operations. In October 2016, the IPAF was fully implemented. A regulatory asset of $11 million representing previously incurred bad debt expense associated with the eligible accounts receivable balances was recorded as of December 31, 2016. Pennsylvania Procurement Proceedings (Exelon and PECO). Through PECO’s first two PAPUC approved DSP Programs, PECO procured electric supply for its default electric customers through PAPUC approved competitive procurements. DSP I and DSP II expired on May 31, 2013 and May 31, 2015, respectively. The second DSP Program included a number of retail market enhancements recommended by the PAPUC in its previously issued Retail Markets Intermediate Work Plan Order. PECO was also directed to submit a plan to allow its low-income CAP customers to purchase their generation supply from EGSs beginning in April 2014. In May 2013, PECO filed its CAP Shopping Plan with the PAPUC. By an Order entered on January 24, 2014, the PAPUC approved PECO’s plan, with modifications, to make CAP shopping available beginning April 15, 2014. On March 20, 2014, the Office of Consumer Advocate (OCA) and low-income advocacy groups filed an appeal and emergency request for a stay with the Pennsylvania Commonwealth Court, claiming that the PAPUC-ordered CAP Shopping plan does not contain sufficient protections for low-income customers. On July 14, 2015, the Court issued opinions on the OCA and low-income advocacy group appeal. Specifically, the Court remanded the issue to the PAPUC with instructions that it approve a rule revision to the PECO CAP Shopping Plan that would prohibit CAP customers from entering into contracts with an EGS that would impose early cancellation/termination fees. The PAPUC, as well as the low-income advocates and the Office of Consumer Advocate, appealed the Court's decision. On April 5, 2016, the Pennsylvania Supreme Court declined to accept the appeals. On May 11, 2016, the PAPUC issued a Secretarial Letter requiring PECO to propose a rule revision to the PECO CAP Shopping Plan consistent with the Court’s decision. On July 19, 2016, PECO filed a letter stating its intent to revise its Plan by September 1, 2016 to incorporate the rule revision. On September 1, 2016, PECO filed its proposed rule revision that is consistent with the Court’s opinion with a proposed effective date of April 14, 2017. On December 4, 2014, the PAPUC approved PECO's third DSP Program. The program has a 24 -month term from June 1, 2015 through May 31, 2017, and complies with electric generation procurement guidelines set forth in Act 129. Under the program, PECO procured electric supply through four competitive procurements for fixed price full requirements contracts of two years or less for the residential classes and small and medium commercial classes and spot market price full requirement contracts for the large commercial and industrial class load. Beginning in June 2016, the medium commercial class (101-500 kW) moved to spot market pricing. In September 2016, PECO entered into contracts with PAPUC-approved bidders, including Generation, resulting from the final of its four scheduled procurements. Charges incurred for electric supply procured through contracts with Generation are included in purchased power from affiliates on PECO's Consolidated Statement of Operations and Comprehensive Income. On March 12, 2015, PECO settled the CAP Design with the Office of Consumer Advocates (OCA) and Low Income Advocates, and filed the proposed plan with the PAPUC on March 20, 2015. The program design changes the rate structure of PECO's CAP to make the bills more affordable to customers enrolled in the assistance program. The CAP discounts continue to be recovered through PECO's universal service fund cost. On July 8, 2015, the CAP Design was approved by the PAPUC, and subsequently implemented in October 2016 as planned. On March 17, 2016, PECO filed its fourth DSP Program with the PAPUC proposing a 24-month term from June 1, 2017 through May 31, 2019, in compliance with electric generation procurement guidelines set forth in Act 129. On October 4, 2016, the Administrative Law Judge recommended that PECO’s previously filed partial settlement be approved without modification. The settlement would extend the program period through May 2021 and consolidate the Medium Commercial and Large Commercial classes of default service customers into a Consolidated Large Commercial Class proposed by the Company. The issue of PECO’s implementation of CAP Shopping was reserved for briefing, and the Administrative Law Judge determined that issue was not a part of the DSP IV case. On December 8, 2016, the PAPUC approved the fourth DSP Program for a 48-month term and deferred CAP Shopping to another proceeding. OCA and Low Income Advocates subsequently filed a Petition for Reconsideration and Clarification, which is pending before the PAPUC. Smart Meter and Smart Grid Investments (Exelon and PECO). In April 2010, pursuant to Act 129 and the follow-on Implementation Order of 2009, the PAPUC approved PECO’s Smart Meter Procurement and Installation Plan (SMPIP), under which PECO will install more than 1.6 million electric smart meters and an AMI communication network by 2020. As approved by the PAPUC, PECO accelerated its installation and deployed substantially all smart meters by December 31, 2015, for a total of 1.7 million smart meters. PECO spent $ 578 million and $ 155 million on smart meter and smart grid infrastructure, respectively, of which $ 200 million has been funded by SGIG. Recovery of smart meter costs are reflected in base rates effective January 1, 2016. Energy Efficiency Programs (Exelon and PECO). The PAPUC issued its Phase II EE&C implementation order on August 2, 2012, that provided energy consumption reduction requirements for the second phase of Act 129’s EE&C program, which went into effect on June 1, 2013. Pursuant to the Phase II implementation order, PECO filed its three-year EE&C Phase II Plan with the PAPUC on November 1, 2012. The plan set forth how PECO would reduce electric consumption by at least 1,125,852 MWh in its service territory for the period June 1, 2013 through May 31, 2016, adjusted for weather and extraordinary loads. The implementation order permitted PECO to apply any excess savings achieved during Phase I against its Phase II consumption reduction targets, with no reduction to its Phase II budget. In accordance with the Act 129 Phase II implementation order, at least 10% and 4.5% of the total consumption reductions had to be through programs directed toward PECO’s public and low income sectors, respectively. Act 129 mandates that the total cost of the plan may not exceed 2% of the electric company’s total annual revenue as of December 31, 2006. On March 15, 2013 and February 28, 2014, PECO filed Petitions for Approval to amend its EE&C Phase II Plan to continue its DLC demand reduction program for mass market customers through May 31, 2014 and May 31, 2016, respectively. PECO proposed to fund the estimated $ 10 million annual costs of the plan by modifying incentive levels for other Phase II programs. The costs of the DLC program were recovered through PECO’s Energy Efficiency Plan surcharge along with other Phase II Plan costs. The PAPUC granted PECO’s Petitions on May 5, 2013 and April 23, 2014, respectively. On November 15 2016, PECO reported to the PAPUC that as of the conclusion of the EE&C Phase II Plan, all plan requirements have been met. A final Phase II compliance determination is expected to be issued in the first half of 2017. On June 19, 2015, the PAPUC issued its Phase III EE&C implementation order that provides energy consumption reduction requirements for the third phase of Act 129’s EE&C program with a five-year term from June 1, 2016 through May 31, 2021. Pursuant to the Phase III implementation order, PECO filed its five-year EE&C Phase III Plan with the PAPUC on November 30, 2015. The Plan sets forth how PECO will reduce electric consumption by at least 1,962,659 MWh, with a goal of 2,100,875 MWh in its service territory for the period June 1, 2016 through May 31, 2021. The PAPUC approved PECO’s EE&C Phase III Plan, with requested clarifications, on May 19, 2016. Alternative Energy Portfolio Standards (Exelon and PECO). In November 2004, Pennsylvania adopted the AEPS Act. The AEPS Act mandated that beginning in 2011, following the expiration of PECO’s rate cap transition period, certain percentages of electric energy sold to Pennsylvania retail electric customers shall be generated from certain alternative energy resources as measured in AECs. The requirement for electric energy that must come from Tier I alternative energy resources ranges from approximately 3.5% to 8% , and the requirement for Tier II alternative energy resources ranges from 6.2% to 10% . The required compliance percentages incrementally increase each annual compliance period, which is from June 1 through May 31, until May 31, 2021. These Tier I and Tier II alternative energy resources include acceptable energy sources as set forth in Act 129 and the AEP

Mergers, Acquisitions and Dispo

Mergers, Acquisitions and Dispositions (All Registrants)	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Mergers, Acquisitions and Dispositions	Merger with Pepco Holdings, Inc. (Exelon) Description of Transaction On March 23, 2016 , Exelon completed the merger contemplated by the Merger Agreement among Exelon, Purple Acquisition Corp., a wholly owned subsidiary of Exelon (Merger Sub) and Pepco Holdings, Inc. (PHI). As a result of that merger, Merger Sub was merged into PHI (the PHI Merger) with PHI surviving as a wholly owned subsidiary of Exelon and Exelon Energy Delivery Company, LLC (EEDC), a wholly owned subsidiary of Exelon which also owns Exelon's interests in ComEd, PECO and BGE (through a special purpose subsidiary in the case of BGE). Following the completion of the PHI Merger, Exelon and PHI completed a series of internal corporate organization restructuring transactions resulting in the transfer of PHI’s unregulated business interests to Exelon and Generation and the transfer of PHI, Pepco, DPL and ACE to a special purpose subsidiary of EEDC. Regulatory Matters Approval of the merger in Delaware, New Jersey, Maryland and the District of Columbia was conditioned upon Exelon and PHI agreeing to certain commitments including where applicable: customer rate credits, funding for energy efficiency and delivery system modernization programs, a green sustainability fund, workforce development initiatives, charitable contributions, renewable generation and other required commitments. In addition, the orders approving the merger in Delaware, New Jersey, and Maryland include a “most favored nation” provision which, generally speaking, requires allocation of merger benefits proportionally across all the jurisdictions. During the third and fourth quarters of 2016, Exelon and PHI filed proposals in Delaware, New Jersey and Maryland for amounts and allocations reflecting the application of the most favored nation provision, resulting in a total nominal cost of commitments of $513 million excluding renewable generation commitments (approximately $444 million on a net present value basis, excluding renewable generation commitments and charitable contributions). These filings, which reflect agreements reached with certain parties to the merger proceedings in the jurisdictions, were subject to regulatory review and approval in each jurisdiction. The DPSC and NJBPU approved the amounts and allocations during the third and fourth quarters of 2016. An order from the MDPSC is expected in the first quarter of 2017. No changes in commitment cost levels are required in the District of Columbia. During the fourth quarter of 2016, the MDPSC approved a change in the application of $9 million in funding for energy-efficiency program support in the DPL MD service territory. This resulted in an adjustment to the merger commitment costs recorded at Exelon Corporate and DPL. Exelon Corporate recorded a decrease and DPL recorded an increase of $9 million in Operating and maintenance expense. The following amounts were recognized as total commitment costs in Operating and maintenance expense in Exelon's, PHI's, Pepco's, DPL's and ACE's Consolidated Statements of Operations and Comprehensive Income for the year ended December 31, 2016 and PHI's successor period: Expected Payment Period Successor Description Pepco (a) DPL (a) ACE (a) PHI (a) Exelon (a) Rate credits 2016 - 2017 $ 91 $ 67 $ 101 $ 259 $ 259 Energy efficiency 2016 - 2021 — — — — 111 Charitable contributions 2016 - 2026 28 12 10 50 50 Delivery system modernization Q2 2016 — — — — 22 Green sustainability fund Q2 2016 — — — — 14 Workforce development 2016 - 2020 — — — — 24 Other 7 7 — 14 33 Total $ 126 $ 86 $ 111 $ 323 $ 513 _______ (a) Included within the individual line items is the most favored nation provision estimate of $6 million , $5 million $38 million , $49 million and $134 million at Pepco, DPL, ACE, PHI and Exelon, respectively. Pursuant to the orders approving the merger, Exelon made $73 million , $46 million and $49 million of equity contributions to Pepco, DPL and ACE, respectively, in the second quarter of 2016 to fund the after-tax amounts of the customer bill credit and the customer base rate credit commitments. In addition, Exelon is committed to develop or to assist in the commercial development of 37 MWs of new generation in Maryland, District of Columbia, and Delaware, 27 MWs of which are to be completed by 2018. These investments are expected to total approximately $137 million , are expected to be primarily capital in nature, and will generate future earnings at Exelon and Generation. Investment costs will be recognized as incurred and recorded on Exelon's and Generation's financial statements. Exelon has also committed to purchase 100 MWs of wind energy in PJM, to procure 120 MWs of wind RECs for the purpose of meeting Delaware's renewable portfolio standards, and to maintain and promote energy efficiency and demand response programs in the PHI jurisdictions. Pursuant to the various jurisdictions' merger approval conditions, over specified periods Pepco, DPL and ACE are not permitted to reduce employment levels due to involuntary attrition associated with the merger integration process and have made other commitments regarding hiring and relocation of positions. Exelon was previously named in suits filed in the Delaware Chancery Court alleging that individual directors of PHI breached their fiduciary duties by entering into the merger transaction and that Exelon aided and abetted the individual directors’ breaches. The suits sought rescission of the merger and unspecified damages and costs. On June 1, 2016, the parties executed a settlement to resolve all claims, subject to the approval of the Delaware Court. A hearing had been scheduled for September 8, 2016 in the Delaware Court to consider whether to approve the settlement. However, on August 19, 2016, the plaintiffs advised Exelon that they had determined to dismiss the case in its entirety and with prejudice. On August 24, 2016, the Delaware Court issued an order approving the dismissal. In July 2015, the OPC, Public Citizen, Inc., the Sierra Club and the Chesapeake Climate Action Network (CCAN) filed motions to stay the MDPSC order approving the merger and in July and August, Exelon, PHI, the MDPSC, Prince George’s County and Montgomery County filed responses opposing the motions to stay. The judge issued an order denying the motions for stay on August 12, 2015. On January 8, 2016, the Circuit Court judge affirmed the MDPSC’s order approving the merger and denied the petitions for judicial review filed by the OPC, the Sierra Club, CCAN and Public Citizen, Inc. On January 19, 2016, the OPC filed a notice of appeal to the Maryland Court of Special Appeals, and on January 21, 2016, the Sierra Club and CCAN filed a notice of appeal. On January 27, 2017, the Maryland Court of Special Appeals affirmed the Circuit Court's judgment. The OPC and Sierra Club have until the later of (i) 30 days from the date of the Court's order or (ii) 15 days from the date the Court enters its mandate, to file their petition for further review in the Court of Appeals. Exelon cannot predict if the petition will be filed. Between March 25, 2016 and April 22, 2016, various parties filed motions with the DCPSC to reconsider its March 23, 2016 order approving the merger. On June 17, 2016, the DCPSC denied all motions. In August 2016, the District of Columbia Office of People’s Counsel, the District of Columbia Government, and Public Citizen jointly with DC Sun each filed petitions for judicial review of the DCPSC’s March 23, 2016 order with the District of Columbia Court of Appeals. On September 9, 2016, the Court consolidated the appeals. The Court has issued a scheduling order, and a decision is expected in the second or third quarter of 2017. Exelon believes the matters are without merit. Accounting for the Merger Transaction The total purchase price consideration of approximately $7.1 billion for the PHI Merger consisted of cash paid to PHI shareholders, cash paid for PHI preferred securities and cash paid for PHI stock-based compensation equity awards as follows: (In millions of dollars, except per share data) Total Consideration Cash paid to PHI shareholders at $27.25 per share (254 million shares outstanding at March 23, 2016) $ 6,933 Cash paid for PHI preferred stock (a) 180 Cash paid for PHI stock-based compensation equity awards (b) 29 Total purchase price $ 7,142 _____________ (a) As of December 31, 2015 , the preferred stock was included in Other non-current assets on Exelon's Consolidated Balance Sheets. (b) PHI’s unvested time-based restricted stock units and performance-based restricted stock units issued prior to April 29, 2014 were immediately vested and paid in cash upon the close of the merger. PHI’s remaining unvested time-based restricted stock units as of the close of the merger were cancelled. There were no remaining unvested performance-based restricted stock units as of the close of the merger. PHI shareholders received $27.25 of cash in exchange for each share of PHI common stock outstanding as of the effective date of the merger. In connection with the Merger Agreement, Exelon entered into a Subscription Agreement under which it purchased $180 million of a new class of nonvoting, nonconvertible and nontransferable preferred securities of PHI prior to December 31, 2015. On March 23, 2016 , the preferred securities were cancelled for no consideration to Exelon, and accordingly, the $180 million cash consideration previously paid to acquire the preferred securities was treated as purchase price consideration. The valuations performed in the first quarter of 2016 to assess the fair value of certain assets acquired and liabilities assumed were considered preliminary as a result of the short time period between the closing of the merger and the end of the first quarter of 2016. Accounting guidance provides that the allocation of the purchase price may be modified up to one year from the date of the merger as more information is obtained about the fair value of assets acquired and liabilities assumed. Exelon expects to finalize these amounts in the first quarter of 2017. During the second, third and fourth quarters of 2016, certain modifications were made to preliminary valuation amounts for acquired property, plant and equipment, unamortized energy contracts, current liabilities, long-term debt, deferred income taxes and pension and OPEB liabilities resulting in an $11 million net decrease to goodwill. The preliminary amounts recognized are subject to further revision to the extent that additional information is obtained about the facts and circumstances that existed as of the acquisition date. Any changes to the fair value assessments may affect the purchase price allocation and could potentially impact goodwill. Exelon applied push-down accounting to PHI, and accordingly, the PHI assets acquired and liabilities assumed were recorded at their estimated fair values on Exelon’s and PHI's Consolidated Balance Sheets as of March 23, 2016 , as follows: Preliminary Purchase Price Allocation Current assets $ 1,441 Property, plant and equipment 11,088 Regulatory assets 5,015 Other assets 248 Goodwill 4,005 Total assets $ 21,797 Current liabilities $ 2,752 Unamortized energy contracts 1,515 Regulatory liabilities 297 Long-term debt, including current maturities 5,636 Deferred income taxes 3,447 Pension and OPEB liabilities 821 Other liabilities 187 Total liabilities $ 14,655 Total purchase price $ 7,142 On its successor financial statements, PHI has recorded, beginning March 24, 2016, Membership interest equity of $7.2 billion , which is greater than the total $7.1 billion purchase price, reflecting the impact of a $59 million deferred tax liability recorded only at Exelon Corporate to reflect unitary state income tax consequences of the merger. The excess of the purchase price over the estimated fair value of the assets acquired and the liabilities assumed totaled $4.0 billion , which was recognized as goodwill by PHI and Exelon at the acquisition date, reflecting the value associated with enhancing Exelon's regulated utility portfolio of businesses, including the ability to leverage experience and best practices across the utilities and the opportunities for synergies. For purposes of future required impairment assessments, the goodwill has been preliminarily assigned to PHI's reportable units Pepco, DPL and ACE in the amounts of $1.7 billion , $1.1 billion and $1.2 billion , respectively. None of this goodwill is tax deductible. Immediately following closing of the merger, $235 million of net assets included in the table above associated with PHI's unregulated business interests were distributed by PHI to Exelon. Exelon contributed $163 million of such net assets to Generation. The fair values of PHI's assets and liabilities were determined based on significant estimates and assumptions that are judgmental in nature, including projected future cash flows (including timing), discount rates reflecting risk inherent in the future cash flows, future market prices and impacts of utility rate regulation. There were also judgments made to determine the expected useful lives assigned to each class of assets acquired. Through its wholly-owned rate regulated utility subsidiaries, most of PHI’s assets and liabilities are subject to cost-of-service rate regulation. Under such regulation, rates charged to customers are established by a regulator to provide for recovery of costs and a fair return on invested capital, or rate base, generally measured at historical cost. In applying the acquisition method of accounting, for regulated assets and liabilities included in rate base or otherwise earning a return (primarily property, plant and equipment and regulatory assets earning a return), no fair value adjustments were recorded as historical cost is viewed as a reasonable proxy for fair value. Fair value adjustments were applied to the historical cost bases of other assets and liabilities subject to rate regulation but not earning a return (including debt instruments and pension and OPEB obligations). In these instances, a corresponding offsetting regulatory asset or liability was also established, as the underlying utility asset and liability amounts are recoverable from or refundable to customers at historical cost (and not at fair value) through the rate setting process. Similar treatment was applied for fair value adjustments to record intangible assets and liabilities, such as for electricity and gas energy supply contracts as further described below. Regulatory assets and liabilities established to offset fair value adjustments are amortized in amounts and over time frames consistent with the realization or settlement of the fair value adjustments, with no impact on reported net income. See Note 3 - Regulatory Matters for additional information regarding the fair value of regulatory assets and liabilities established by Exelon and PHI. Fair value adjustments were recorded at Exelon and PHI for the difference between the contract price and the market price of electricity and gas energy supply contracts of PHI’s wholly-owned rate regulated utility subsidiaries. These adjustments are intangible assets and liabilities classified as unamortized energy contracts on Exelon’s and PHI’s Consolidated Balance Sheets as of December 31, 2016 . The difference between the contract price and the market price at the acquisition date of the Merger was recognized for each contract as either an intangible asset or liability. In total, Exelon and PHI recorded a net $1.5 billion liability reflecting out-of-the-money contracts. The valuation of the acquired intangible assets and liabilities was estimated by applying either the market approach or the income approach depending on the nature of the underlying contract. The market approach was utilized when prices and other relevant information generated by market transactions involving comparable transactions were available. Otherwise the income approach, which is based upon discounted projected future cash flows associated with the underlying contracts, was utilized. In certain instances, the valuations were based upon certain unobservable inputs, which are considered Level 3 inputs, pursuant to applicable accounting guidance. Key estimates and inputs include forecasted power prices and the discount rate. The unamortized energy contract fair value adjustment amounts and the corresponding offsetting regulatory asset and liability amounts are amortized through Purchase power and fuel expense or Operating revenues, as applicable, over the life of the applicable contract in relation to the present value of the underlying cash flows as of the merger date. As mentioned, under cost-of-service rate regulation, rates charged to customers are established by a regulator to provide for recovery of costs and a fair return on invested capital, or rate base, generally measured at historical cost. Historical cost information therefore is the most relevant presentation for the financial statements of PHI’s rate regulated utility subsidiary registrants, Pepco, DPL and ACE. As such, Exelon and PHI did not push-down the application of acquisition accounting to PHI's utility registrants, and therefore the financial statements of Pepco, DPL and ACE do not reflect the revaluation of any assets and liabilities. The current impact of PHI, including its unregulated businesses, on Exelon's Consolidated Statements of Operations and Comprehensive Income includes Operating revenues of $3,785 million and Net loss of $(66) million during the year ended December 31, 2016 . For the periods ended December 31, 2016 and 2015 , Exelon and PHI have recognized expense to achieve the PHI acquisition as follows: For the Year Ended December 31, Acquisition, Integration and Financing Costs (a) 2016 2015 Exelon (b) $ 143 $ 87 Generation 37 24 ComEd (c) (6 ) 9 PECO 5 4 BGE (c) (1 ) 5 Pepco (c) 28 3 DPL (c) 20 2 ACE 19 1 Successor Predecessor Acquisition, Integration and Financing Costs (a) March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 PHI (c) $ 69 $ 29 $ 19 ______________ (a) The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statements of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. Costs do not include merger commitments discussed above. (b) Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps. (c) For the year ended December 31, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million , $6 million , $11 million , $4 million , and $16 million incurred at ComEd, BGE, Pepco, DPL and PHI, respectively, that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 3 - Regulatory Matters for more information. Pro-forma Impact of the Merger The following unaudited pro forma financial information reflects the consolidated results of operations of Exelon as if the merger with PHI had taken place on January 1, 2015 . The unaudited pro forma information was calculated after applying Exelon’s accounting policies and adjusting PHI’s results to reflect purchase accounting adjustments. The unaudited pro forma financial information has been presented for illustrative purposes only and is not necessarily indicative of results of operations that would have been achieved had the merger events taken place on the dates indicated, or the future consolidated results of operations of the combined company. Year Ended December 31, 2016 (a) 2015 (b) Total operating revenues $ 32,342 $ 33,823 Net income attributable to common shareholders 1,562 2,618 Basic earnings per share $ 1.69 $ 2.85 Diluted earnings per share 1.69 2.84 ______________ (a) The amounts above exclude non-recurring costs directly related to the merger of $680 million and intercompany revenue of $171 million for year ended December 31, 2016 . (b) The amounts above exclude non-recurring costs directly related to the merger of $92 million and intercompany revenue of $559 million for the year ended December 31, 2015 . Acquisition of ConEdison Solutions (Exelon and Generation) On September 1, 2016, Generation acquired the competitive retail electricity and natural gas business of Consolidated Edison Solutions, Inc. (ConEdison Solutions), a subsidiary of Consolidated Edison, Inc. for a purchase price of $257 million including net working capital of $204 million . The renewable energy, sustainable services and energy efficiency businesses of ConEdison Solutions are excluded from the transaction. As of December 31, 2016 , Generation had remitted $235 million to ConEdison Solutions and the remaining balance of $22 million , which is included in Other current liabilities on Exelon's and Generation's Consolidated Balance Sheets, will be paid during the first quarter of 2017. The following table summarizes the acquisition-date fair value of the consideration transferred and the assets and liabilities assumed for the ConEdison Solutions acquisition by Generation as of September 1, 2016: Total consideration transferred $ 257 Identifiable assets acquired and liabilities assumed Working capital assets $ 204 Property, plant and equipment 2 Mark-to-market derivative assets 6 Unamortized energy contract assets 100 Customer relationships 9 Other assets 1 Total assets $ 322 Mark-to-market derivative liabilities $ (65 ) Total liabilities $ (65 ) Total net identifiable assets, at fair value $ 257 The purchase price equaled the estimated fair value of the net assets acquired and the liabilities assumed and, therefore, no goodwill or bargain purchase was recorded as of December 31, 2016 . The purchase accounting is preliminary, and, although not expected, may be further adjusted from what is shown above. Accounting guidance provides that the allocation of the purchase price may be modified up to one year from the date of the acquisition as more information is obtained about the fair value of assets acquired and liabilities assumed; however, Generation expects to finalize these amounts by the first quarter of 2017. The fair values of ConEdison Solutions' assets and liabilities were determined based on significant estimates and assumptions that are judgmental in nature, including projected future cash flows (including timing), discount rates reflecting risk inherent in the future cash flows and future power and fuel market prices. Proposed Acquisition of James A. FitzPatrick Nuclear Generating Station (Exelon and Generation) On August 8, 2016, Generation executed a series of agreements with Entergy Nuclear FitzPatrick LLC (Entergy) to acquire the 838 MW single-unit James A. FitzPatrick (FitzPatrick) nuclear generating station located in Scriba, New York for a cash purchase price of $110 million . As part of the transaction, Generation would receive the FitzPatrick NDT fund assets and assume the obligation to decommission FitzPatrick. The NRC license for FitzPatrick expires in 2034. In November 2015, Entergy had announced plans to early retire FitzPatrick at the end of the current fuel cycle in January 2017. Under the terms of the agreements, Generation will reimburse Entergy for approximately $200 million to $250 million of incremental costs to prepare for and conduct the plant refueling outage as well as to operate and maintain the plant after the refueling outage, scheduled to end in February 2017, through the closing date. These are costs which otherwise would have been avoided by FitzPatrick’s planned permanent shutdown in January 2017. Generation will be entitled to all revenues from FitzPatrick’s electricity and capacity sales for the period commencing upon completion of the refueling outage through the acquisition closing date. The agreements provide for certain termination rights, including the right of either party to terminate if the transaction has not been consummated within 12 months due to failure to obtain the required regulatory approvals. Closing of the transaction is currently anticipated to occur in the first half of 2017 and requires regulatory approval by FERC, NRC, and the New York Public Service Commission (NYPSC). The transaction is also subject to the notification and reporting requirements of the HSR Act (which had been completed) and other customary closing conditions. On November 17, 2016 the NYPSC issued an order approving the transaction. On October 11, 2016, Public Citizen, Inc. filed a protest with FERC challenging Generation and Entergy’s application to FERC for the transfer of ownership of FitzPatrick. No other party to the FERC proceeding filed any protests or comments. On December 7, 2016 FERC approved Generation's acquisition of the FitzPatrick facility and dismissed the Public Citizen protest. Public Citizen filed a request for rehearing on January 6, 2017. NRC is the final regulatory approval required to close the transaction and is anticipated during the first half of 2017. The transaction is expected to be accounted for as a business combination. For accounting and financial reporting purposes, the costs for which Generation reimburses Entergy as well as the revenue received from FitzPatrick prior to the closing of the transaction will be treated as part of the purchase price consideration. Generation will record the fair value of the assets acquired and liabilities assumed as of the acquisition date. To the extent the purchase price is greater than the fair value of the net assets acquired, goodwill will be recorded. To the extent the fair value of the net assets acquired is greater than the purchase price, a bargain purchase gain will be recorded. As of December 31, 2016 , Generation has recorded $127 million of purchase price consideration in Other noncurrent assets on Exelon’s and Generation’s Consolidated Balance Sheets. The cash outflows associated with these amounts are reflected within Acquisition of businesses on Exelon’s and Generation’s Consolidated Statements of Cash Flows. In the event the acquisition does not close, these amounts would be subject to potential write-off to Operating and maintenance expense in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. For the year ended December 31, 2016 , Exelon and Generation incurred $19 million of merger and integration related costs which are included within Operating and maintenance expense in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. Acquisition of Integrys Energy Services, Inc. (Exelon and Generation) On November 1, 2014, Generation acquired the competitive retail electric and natural gas business activities of Integrys Energy Group, Inc. through the purchase of all of the stock of its wholly owned subsidiary, Integrys Energy Services, Inc. (IES) for a purchase price of $332 million including net working capital. Generation has elected to account for the transaction as an asset acquisition for federal income tax purposes. The generation and solar asset businesses of Integrys are excluded from the transaction. The Purchase Agreement also includes various representations, warranties, covenants, indemnification and other provisions customary for a transaction of this nature. Consistent with the applicable accounting guidance, the fair value of the assets acquired and liabilities assumed was determined as of the acquisition date through the use of significant estimates and assumptions that are judgmental in nature. Some of the more significant estimates and assumptions used include: projected future cash flows (including the amount and timing); discount rates reflecting the risk inherent in the future cash flows; and future power and fuel market prices. The following table summarizes the acquisition-date fair value of the consideration transferred and the assets and liabilities assumed for the Integrys acquisition by Generation: Total consideration transferred $ 332 Identifiable assets acquired and liabilities assumed Working capital assets $ 390 Mark-to-market derivative assets 184 Unamortized energy contract assets 115 Customer relationships 50 Working capital liabilities (196 ) Mark-to-market derivative liabilities (57 ) Unamortized energy contract liabilities (110 ) Deferred tax liability (16 ) Total net identifiable assets, at fair value $ 360 Bargain purchase gain (after-tax) $ 28 The after-tax bargain purchase gain of $28 million is primarily the result of IES executing additional contract volumes between the date the acquisition agreement was signed and the closing of the transaction resulting in an increase in the fair value of the net assets acquired as of the acquisition date. The after-tax gain is included within Gain on consolidation and acquisition of businesses in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. IES's operating revenues and net loss included in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income for the period from November 1, 2014 to December 31, 2014 were $386 million and $(42) million , respectively. The net loss for the period from November 1, 2014 to December 31, 2014 includes pre-tax unrealized losses on derivative contracts of $108 million and the bargain purchase gain of $28 million . It is impracticable to determine the overall financial statement impact of IES for 2015 and 2016 due to the integration of the business into ongoing operations. For the years ended December 31, 2015 , and 2014, Exelon and Generation incurred $5 million and $7 million , respectively, of merger and integration related costs which are included within Operating and maintenance expense in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. Asset Divestitures (Exelon, Generation, PHI, Pepco and DPL) On November 10, 2015, Pepco completed the sale of a 3.5 acre parcel of unimproved land (held as non-utility property) in the Buzzard Point area of southeast Washington, D.C., resulting in a pre-tax gain of $37 million . On December 31, 2015, Pepco completed the sale of a 3.8 acre parcel of unimproved land (held as non-utility property) in the NoMa area of northeast Washington, D.C., resulting in a pre-tax gain of $9 million . The purchase and sale agreement also provided the third party with a 90-day option to purchase the remaining 1.8 acre land parcel. On April 21, 2016, Generation completed the sale of the retired New Boston generating site, located in Boston, Massachusetts, resulting in a pre-tax gain of approximately $32 million . On May 2, 2016, Pepco completed the sale of the remaining 1.8 acre land parcel noted above, located in the NoMa area of northeast Washington, D.C., resulting in a pre-tax gain of approximately $8 million at Pepco. Due to the fair value adjustments recorded at Exelon and PHI as part of purchase accounting, no gain was recorded in Exelon's and PHI's Consolidated Statements of Operations and Comprehensive Income. On June 16, 2016, Generation initiated the sales process of its Upstream business by executing a forbearance agreement with the lenders of the nonrecourse debt. See Note 14 - Debt and Credit Agreements for more information. In December 2016, Generation sold substantially all of the Upstream assets for $37 million which resulted in a pre-tax loss on sale of $10 million which is included in Gain (loss) on sales of assets on Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income for the year ended December 31, 2016. In July 2016, DPL completed the sale of a 9 acre land parcel located on South Madison Street in Wilmington, DE, resulting in a pre-tax gain of approximately $4 million . In December 2016, DPL completed the sale of a 48 acre land parcel located in Middletown, DE, resulting in a pre-tax gain of approximately $5 million . Due to the fair value adjustments recorded at Exelon and PHI as part of purchase accounting, no gain was recorded in Exelon's and PHI's Consolidated Statements of Operations and Comprehensive Income. During the fourth quarter, as part of its continual assessment of growth and development opportunities, Generation has reevaluated and in certain instances terminated or renegotiated certain projects and contracts. As a result a pre-tax loss of $69 million was recorded within Loss on sale of assets and pre-tax impairment charges of $23 million were recorded within Operating and maintenance expense in Exel

Investment in Constellation Ene

Investment in Constellation Energy Nuclear Group, LLC (Exelon and Generation)	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Investment in Constellation Energy Nuclear Group LLC (Exelon and Generation)	(Exelon and Generation) Generation owns a 50.01% interest in CENG, a nuclear generation business. Generation has historically had various agreements with CENG to purchase power and to provide certain services. For further information regarding these agreements, see Note 27 — Related Party Transactions . On April 1, 2014, Generation and subsidiaries of Generation and CENG entered into a Nuclear Operating Services Agreement (NOSA) pursuant to which Generation will operate the CENG nuclear generation fleet owned by CENG subsidiaries and provide corporate and administrative services for the remaining life of the CENG nuclear plants as if they were a part of the Generation nuclear fleet, subject to EDF’s rights as a member of CENG (the Integration Transaction). CENG will reimburse Generation for its direct and allocated costs for such services. As part of the arrangement, Nine Mile Point Nuclear Station, LLC, a subsidiary of CENG, also assigned to Generation its obligations as Operator of Nine Mile Point Unit 2 under an operating agreement with Long Island Power Authority, the Unit 2 co-owner. In addition, on April 1, 2014, the Power Services Agency Agreement (PSAA) was amended and extended until the permanent cessation of power generation by the CENG generation plants. In addition, on April 1, 2014, Generation made a $ 400 million loan to CENG, bearing interest at 5.25% per annum and payable out of specified available cash flows of CENG or payable upon the maturity date of April 1, 2034. Immediately following receipt of the proceeds of such loan, CENG made a $ 400 million special distribution to EDF. Unpaid principal and accrued interest on the loan was $316 million as of December 31, 2016 . Exelon, Generation, and subsidiaries of Generation, EDF and CENG also executed a Fourth Amended and Restated Operating Agreement for CENG on April 1, 2014, pursuant to which, among other things, CENG committed to make preferred distributions to Generation (after repayment of the $ 400 million loan and associated interest) quarterly out of specified available cash flows until Generation has received aggregate distributions of $ 400 million plus a return of 8.5% per annum from April 1, 2014 (Preferred Distribution Rights). Generation and EDF also entered into a Put Option Agreement on April 1, 2014, pursuant to which EDF has the option, exercisable beginning on January 1, 2016 and thereafter until June 30, 2022, to sell its 49.99% interest in CENG to Generation for a fair market value price determined by agreement of the parties, or absent agreement, a third-party arbitration process. The appraisers determining fair market value of EDF’s 49.99% interest in CENG under the Put Option Agreement are instructed to take into account all rights and obligations under the CENG Operating Agreement, including Generation’s rights with respect to any unpaid aggregate preferred distributions and the related return, and the value of Generation’s rights to other distributions. Under limited circumstances, the period for exercise of the put option may be extended for 18 months. In order to exercise its option, EDF must give 60 days advance written notice to Generation stating that it is exercising its option. As of the date these financial statements were issued, EDF has not given notice to Generation that it is exercising its option. On April 1, 2014, Generation also executed an Indemnity Agreement pursuant to which Generation indemnified EDF against third-party claims that may arise from any future nuclear incident (as defined in the Price Anderson Act) in connection with the CENG nuclear plants or their operations. Exelon guarantees Generation’s obligations under this indemnity. In addition, on April 1, 2014, Generation, EDF, CENG and Nine Mile Point Nuclear Station, LLC entered into an Employee Matters Agreement (EMA) that provides for the transfer of CENG employees to Exelon or one of its affiliates and Exelon's assumption of the sponsorship of the employee benefit plans (including certain incentive, health and welfare, and postemployment benefit plans, among others) and their related trusts by Exelon as the plan sponsor as of July 14, 2014. The EMA also generally requires CENG to fund the obligation related to pre-transfer service of employees, including the underfunded balance of the pension and other postretirement welfare benefit plans measured as of July 14, 2014 by making periodic payments to Generation. These payments will be made on an agreed payment schedule or upon the occurrence of certain specified events, such as EDF’s disposition of a majority of its interest in CENG. However, in the event that EDF exercises its rights under the Put Option, all payments not made as of the put closing date shall accelerate to be paid immediately prior to such closing date. As a condition to obtaining regulatory approval for the NOSA and related transactions from the NRC, Exelon executed a support agreement pursuant to which Exelon may be required under specified circumstances to provide up to $ 245 million of financial support to CENG (Exelon Support Agreement). The Exelon Support Agreement supersedes a previous support agreement under which Generation had agreed to provide up to $ 205 million of financial support for CENG. In addition, Exelon executed a Guarantee pursuant to which Exelon may be required under specified circumstances to provide up to $ 165 million in additional financial support for CENG. A previous support agreement executed by an affiliate of EDF remains in effect under which the EDF affiliate may be required to provide up to approximately $ 145 million of financial support for CENG under specified circumstances. The agreements were executed on April 1, 2014 when the NRC licenses were transferred to Generation. No liability has been recognized by Exelon for the guarantees. Prior to April 1, 2014, Exelon and Generation accounted for their investment in CENG under the equity method of accounting. From January 1, 2014, through March 31, 2014, Generation recorded $ 19 million of equity in losses of unconsolidated affiliates related to its investment in CENG and recorded $ 17 million of revenues from CENG. The book value of Generation’s investment in CENG prior to the consolidation was $ 1.9 billion , and the book value of the AOCI related to CENG prior to consolidation was $ 116 million , net of taxes of $ 77 million . As a result of the consolidation of CENG on April 1, 2014, there are several additional transactions included in Exelon’s and Generation’s Consolidated Financial Statements between CENG and Exelon's affiliates that are considered related party transactions to Generation. As further described in Note 27 — Related Party Transactions , EDF and Generation had a PPA with CENG under which they purchased 15% and 85% , respectively, of the nuclear output owned by CENG that was not sold to third parties under pre-existing PPAs through December 31, 2014. Beginning January 1, 2015 and continuing through the life of the respective plants, EDF and Generation purchase 49.99% and 50.01% , respectively, of the nuclear output owned by CENG not subject to other contractual agreements. Beginning April 1, 2014, CENG's sales to Generation have been eliminated in consolidation. For the years ended December 31, 2016 , 2015 , and 2014 Generation had sales to EDF of $376 million , $488 million , and $137 million respectively. See discussion above and Note 2 — Variable Interest Entities for additional information regarding other transactions between CENG and EDF included within Exelon and Generation’s consolidated financial statements and for additional information about the Registrants VIE's. Accounting for the Consolidation of CENG The transfer of the nuclear operating licenses and the execution of the NOSA on April 1, 2014, resulted in the derecognition of the equity method investment in CENG and the recording of all assets, liabilities and EDF’s noncontrolling interests in CENG at fair value on Exelon’s and Generation’s Consolidated Balance Sheets. As a result of the consolidation, Exelon and Generation recorded a net gain of $261 million within their respective Consolidated Statements of Operations and Comprehensive Income. This gain consists of approximately $136 million related to the step up to fair value basis of Generation's ownership interest in CENG, and approximately $132 million related to the settlement of pre-existing transactions between CENG and Generation. The net gain on the consolidation of CENG of $261 million is net of a $7 million payment to EDF. The fair value of CENG’s assets and liabilities recorded in consolidation was determined based on significant estimates and assumptions that are judgmental in nature, including projected future cash flows (including timing); discount rates reflecting risk inherent in the future cash flows; and future market prices. There were also judgments made to determine the expected useful lives assigned to each class of assets acquired and duration of liabilities assumed. The valuations necessary to assess the fair values of certain assets and liabilities were considered preliminary as a result of the short time period between the execution of the NOSA and the end of the second quarter of 2014. The estimates of the fair value of assets and liabilities could be modified for up to one year from April 1, 2014, as more information was obtained about the fair value of assets and liabilities. The principal items that have been revised include the asset retirement obligation liabilities and related asset retirement costs. These items have been updated with inputs from a third party engineering firm with corresponding adjustments recorded in 2014 and the first quarter of 2015. See Note 16 — Asset Retirement Obligations for discussion of the impacts of adjustments recorded during 2014 and 2015 related to updated estimates of the CENG asset retirement obligation liabilities. In the period of such revisions, these and any other material changes to the fair value assessments have resulted in adjustments to the amounts recorded upon consolidation. In addition, the asset or liability adjustments impacting depreciation and/or accretion expense recorded after the consolidation date have impacted Generation’s post-consolidation results of operations. Generation recorded the assets and liabilities of CENG at fair value as of April 1, 2014. The following assets and liabilities of CENG were recorded within Generation’s Consolidated Balance Sheets as of the date of integration, adjusted for the modifications discussed above: Fair Values Exelon and Generation Current assets $ 499 Nuclear decommissioning trust fund 1,955 Property, plant and equipment 3,073 Nuclear fuel 482 Other assets 10 Total assets 6,019 Current liabilities 237 Asset retirement obligation 1,816 Pension and other employee benefit obligations 281 Unamortized energy contract liabilities 171 Other liabilities 114 Total liabilities 2,619 Total net assets $ 3,400 Generation also recorded the fair value of the noncontrolling interests on its Consolidated Balance Sheets of approximately $ 1.5 billion , net of the fair value of $ 152 million for certain specified additional distribution rights under the Operating Agreement. In addition, the noncontrolling interests was further reduced by the $ 400 million special cash distribution to EDF. Due to the Preferred Distribution Rights that Generation has on CENG’s available cash, the earnings attributable to the noncontrolling interests on the Statements of Operations and Comprehensive Income as well as the corresponding adjustment to Noncontrolling interests on the Consolidated Balance Sheets will not be in proportion to Generation’s and EDF’s equity ownership interests. Rather, the attribution will consider Generation’s Preferred Distribution Rights and allocate net income based on each owner’s rights to CENG’s net assets. For the years ended December 31, 2016 and 2015 , Generation reduced by $20 million and $18 million , respectively, the amount of Net income attributable to noncontrolling interests on Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. As a result of the consolidation, Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income includes CENG’s incremental operating revenues of $548 million and $509 million and CENG’s net income (loss), prior to any intercompany eliminations and any adjustments for noncontrolling interests, of $201 million and $(11) million during the years ended December 31, 2016 and 2015 , respectively. Exelon and Generation incurred no merger integration-related costs in 2016. However, in 2015 Exelon and Generation incurred $2 million of merger related integration costs. The costs incurred are classified primarily within Operating and maintenance expense in Exelon’s and Generation’s respective Consolidated Statements of Operations and Comprehensive Income.

Accounts Receivable (All Regist

Accounts Receivable (All Registrants)	12 Months Ended
	Dec. 31, 2016
Receivables [Abstract]
Accounts Receivable (All Registrants)	Accounts Receivable (All Registrants) Accounts receivable at December 31, 2016 and 2015 included estimated unbilled revenues, representing an estimate for the unbilled amount of energy or services provided to customers, and is net of an allowance for uncollectible accounts as follows: Successor 2016 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Unbilled customer revenues $ 1,673 $ 910 (a) $ 219 $ 140 $ 182 $ 222 $ 123 $ 58 $ 41 Allowance for uncollectible accounts (b) (334 ) (91 ) (70 ) (61 ) (c) (32 ) (80 ) (d) (29 ) (d) (24 ) (d) (27 ) (d) Predecessor 2015 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Unbilled customer revenues $ 1,203 $ 732 (a) $ 218 $ 105 $ 148 $ 177 $ 93 $ 45 $ 39 Allowance for uncollectible (b) (284 ) (77 ) (75 ) (83 ) (c) (49 ) (56 ) (17 ) (17 ) (17 ) _________________________ (a) Represents unbilled portion of retail receivables estimated under Exelon’s unbilled critical accounting policy. (b) Includes the allowance for uncollectible accounts on customer and other accounts receivable. (c) Excludes the non-current allowance for uncollectible accounts of $23 million and $8 million at December 31, 2016 and 2015 , respectively, related to PECO’s current installment plan receivables described below. (d) At December 31, 2016 , as explained in Note 1 — Significant Accounting Policies , PHI, Pepco, DPL and ACE estimated the allowance for uncollectible accounts on customer receivables by applying loss rates to the outstanding receivable balance by risk segment. The change in estimate resulted in an overall increase of $30 million , $14 million , $8 million , and $8 million in the allowance for uncollectible accounts with $20 million , $8 million , $4 million , and $8 million deferred as a regulatory asset on PHI's, Pepco's, DPL's and ACE's Consolidated Balance Sheets at December 31, 2016, respectively. This also resulted in a $10 million , $6 million , and $4 million pre-tax charge to provision for uncollectible accounts expense for the year ended December 31, 2016 , which is included in Operating and maintenance expense on PHI's, Pepco's, and DPL's Consolidated Statements of Operations and Comprehensive Income, respectively. PECO Installment Plan Receivables (Exelon and PECO). PECO enters into payment agreements with certain delinquent customers, primarily residential, seeking to restore their service, as required by the PAPUC. Customers with past due balances that meet certain income criteria are provided the option to enter into an installment payment plan, some of which have terms greater than one year, to repay past due balances in addition to paying for their ongoing service on a current basis. The receivable balance for these payment agreement receivables is recorded in accounts receivable for the current portion and other deferred debits and other assets for the noncurrent portion. The net receivable balance for installment plans with terms greater than one year was $9 million and $15 million at December 31, 2016 and 2015 , respectively. The allowance for uncollectible accounts reserve methodology and assessment of the credit quality of the installment plan receivables are consistent with the customer accounts receivable methodology discussed in Note 1 — Significant Accounting Policies . The allowance for uncollectible accounts balance associated with these receivables at December 31, 2016 of $13 million consists of $1 million , $3 million and $9 million for low risk, medium risk and high risk segments, respectively. The allowance for uncollectible accounts balance associated with these receivables at December 31, 2015 of $15 million consists of $1 million , $3 million and $11 million for low risk, medium risk and high risk segments, respectively. The balance of the payment agreement is billed to the customer in equal monthly installments over the term of the agreement. Installment receivables outstanding as of December 31, 2016 and 2015 include balances not yet presented on the customer bill, accounts currently billed and an immaterial amount of past due receivables. When a customer defaults on its payment agreement, the terms of which are defined by plan type, the entire balance of the agreement becomes due and the balance is reclassified to current customer accounts receivable and reserved for in accordance with the methodology discussed in Note 1 — Significant Accounting Policies .

Property, Plant and Equipment (

Property, Plant and Equipment (All Registrants)	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment (All Registrants)	Property, Plant and Equipment (All Registrants) Exelon The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-90 $ 45,698 $ 32,546 Electric—generation 3-56 27,193 25,615 Gas—transportation and distribution 5-90 4,642 3,864 Common—electric and gas 4-50 1,312 1,149 Nuclear fuel (a) 1-8 6,546 6,384 Construction work in progress N/A 4,306 3,075 Other property, plant and equipment (b) 3-50 1,027 1,181 Total property, plant and equipment 90,724 73,814 Less: accumulated depreciation (c) 19,169 16,375 Property, plant and equipment, net $ 71,555 $ 57,439 _________________________ (a) Includes nuclear fuel that is in the fabrication and installation phase of $1,326 million and $1,266 million at December 31, 2016 and 2015 , respectively. (b) Includes Generation’s buildings under capital lease with a net carrying value of $10 million and $13 million at December 31, 2016 and 2015 , respectively. The original cost basis of the buildings was $52 million , and total accumulated amortization was $42 million and $39 million , as of December 31, 2016 and 2015 , respectively. Also includes ComEd’s buildings under capital lease with a net carrying value at both December 31, 2016 and 2015 , of $7 million . The original cost basis of the buildings was $8 million and total accumulated amortization was $1 million as of both December 31, 2016 and 2015 . Includes land held for future use and non utility property at ComEd, PECO, BGE, Pepco, DPL, and ACE of $60 million , $21 million , $32 million , $66 million , $16 million , and $27 million , respectively, at December 31, 2016 . At December 31, 2015 these balances also include capitalized acquisition, development and exploration costs of $266 million related to oil and gas production activities at Generation, see Note 4 — Mergers, Acquisitions, and Dispositions for additional information regarding the sale of upstream assets. Includes the original cost and progress payments associated with Generation’s turbine equipment held for future use with a carrying value of $17 million and $146 million at December 31, 2016 and 2015 , respectively. See Note 8 — Impairment of Long-Lived Assets for additional information on the impairment of Generations turbine equipment. (c) Includes accumulated amortization of nuclear fuel in the reactor core at Generation of $3,186 million and $2,861 million as of December 31, 2016 and 2015 , respectively. The following table presents the annual depreciation provisions as a percentage of average service life for each asset category. Average Service Life Percentage by Asset Category 2016 2015 2014 Electric—transmission and distribution 2.73 % 2.83 % 2.93 % Electric—generation 5.94 % (a) 3.47 % 3.50 % Gas 2.17 % 2.17 % 2.13 % Common—electric and gas 7.41 % 7.79 % 7.32 % _________________________ (a) See Note 9 — Early Nuclear Plant Retirements for additional information on the accelerated net depreciation and amortization of Clinton and Quad Cities. Generation The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—generation 3-56 $ 27,193 $ 25,615 Nuclear fuel (a) 1-8 6,546 6,384 Construction work in progress N/A 2,332 2,017 Other property, plant and equipment (b) 4 76 466 Total property, plant and equipment 36,147 34,482 Less: accumulated depreciation (c) 10,562 8,639 Property, plant and equipment, net $ 25,585 $ 25,843 _________________________ (a) Includes nuclear fuel that is in the fabrication and installation phase of $1,326 million and $1,266 million at December 31, 2016 and 2015 , respectively. (b) Includes buildings under capital lease with a net carrying value of $10 million and $13 million at December 31, 2016 and 2015 , respectively. The original cost basis of the buildings was $52 million , and total accumulated amortization was $42 million and $39 million , as of December 31, 2016 and 2015 , respectively. At December 31, 2015 these balances also include capitalized acquisition, development and exploration costs of $266 million related to oil and gas production activities at Generation, see Note 4 — Mergers, Acquisitions, and Dispositions for additional information regarding the sale of upstream assets. Includes the original cost and progress payments associated with Generation’s turbine equipment held for future use with a carrying value of $17 million and $146 million at December 31, 2016 and 2015 , respectively. See Note 8 — Impairment of Long-Lived Assets for additional information on the impairment of Generations turbine equipment. (c) Includes accumulated amortization of nuclear fuel in the reactor core of $3,186 million and $2,861 million as of December 31, 2016 and 2015 , respectively. The annual depreciation provisions as a percentage of average service life for electric generation assets were 5.94% , 3.47% and 3.50% for the years ended December 31, 2016 , 2015 and 2014 , respectively. See Note 9 — Early Nuclear Plant Retirements for additional information on the accelerated net depreciation and amortization of Clinton and Quad Cities. License Renewals. Generation’s depreciation provisions are based on the estimated useful lives of its generating stations, which assume the renewal of the licenses for all nuclear generating stations (except for Oyster Creek and Clinton) and the hydroelectric generating stations. As a result, the receipt of license renewals has no material impact on the Consolidated Statements of Operations and Comprehensive Income. Oyster Creek depreciation provisions are based on the 2019 expected shutdown date. Clinton depreciation provisions are based on 2027 which is the last year of the Illinois ZECs. See Note 3 - Regulatory Matters for additional information regarding license renewals and the Illinois ZECs. See Note 9 - Early Nuclear Plant Retirements for additional information on the impacts of expected and potential early plant retirement. ComEd The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-80 $ 22,636 $ 20,576 Construction work in progress N/A 569 572 Other property, plant and equipment (a), (b) 37-50 67 64 Total property, plant and equipment 23,272 21,212 Less: accumulated depreciation 3,937 3,710 Property, plant and equipment, net $ 19,335 $ 17,502 _________________________ (a) Includes buildings under capital lease with a net carrying value at both December 31, 2016 and 2015 of $7 million . The original cost basis of the buildings was $8 million and total accumulated amortization was $1 million as of both December 31, 2016 and 2015 . (b) Includes land held for future use and non-utility property. The annual depreciation provisions as a percentage of average service life for electric transmission and distribution assets were 3.03% , 3.03% and 3.05% for the years ended December 31, 2016 , 2015 and 2014 , respectively. PECO The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-65 $ 7,591 $ 7,230 Gas—transportation and distribution 5-70 2,348 2,206 Common—electric and gas 5-50 670 631 Construction work in progress N/A 188 154 Other property, plant and equipment (a) 50 21 21 Total property, plant and equipment 10,818 10,242 Less: accumulated depreciation 3,253 3,101 Property, plant and equipment, net $ 7,565 $ 7,141 _________________________ (a) Represents land held for future use and non-utility property. The following table presents the annual depreciation provisions as a percentage of average service life for each asset category. Average Service Life Percentage by Asset Category 2016 2015 2014 Electric—transmission and distribution 2.32 % 2.39 % 2.55 % Gas 1.82 % 1.87 % 1.84 % Common—electric and gas 5.11 % 5.16 % 5.16 % BGE The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-90 $ 7,067 $ 6,663 Gas—distribution 5-90 2,170 1,951 Common—electric and gas 5-40 707 655 Construction work in progress N/A 318 312 Other property, plant and equipment (a) 20 32 32 Total property, plant and equipment 10,294 9,613 Less: accumulated depreciation 3,254 3,016 Property, plant and equipment, net $ 7,040 $ 6,597 _______________________ (a) Represents land held for future use and non-utility property. The following table presents the annual depreciation provisions as a percentage of average service life for each asset category. Average Service Life Percentage by Asset Category 2016 2015 2014 Electric—transmission and distribution 2.56 % 2.62 % 2.96 % Gas 2.45 % 2.50 % 2.47 % Common—electric and gas 9.45 % 10.35 % 9.49 % PHI The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Successor Predecessor Average 2016 2015 Asset Category Electric—transmission and distribution 5-86 $ 10,315 $ 14,563 Gas—distribution 5-75 414 547 Common—electric and gas 4-40 65 164 Construction work in progress N/A 892 591 Other property, plant and equipment (a) 3-43 107 339 Total property, plant and equipment 11,793 16,204 Less: accumulated depreciation 195 — 5,340 Property, plant and equipment, net $ 11,598 $ 10,864 _______________________ (a) Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien. The following table presents the annual depreciation provisions as a percentage of average service life for each asset category. Average Service Life Percentage by Asset Category 2016 2015 2014 Electric—transmission and distribution 2.52 % 2.48 % 2.42 % Gas 2.57 % 2.55 % 2.48 % Common—electric and gas 8.12 % 5.19 % 4.55 % Pepco The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-86 $ 8,018 $ 7,682 Construction work in progress N/A 537 318 Other property, plant and equipment (a) 10-33 66 91 Total property, plant and equipment 8,621 8,091 Less: accumulated depreciation 3,050 — 2,929 Property, plant and equipment, net $ 5,571 $ 5,162 _______________________ (a) Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien. The annual depreciation provisions as a percentage of average service life for electric transmission and distribution assets were 2.17% , 2.13% and 2.10% for the years ended December 31, 2016 , 2015 and 2014 , respectively. DPL The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service life 2016 2015 Asset Category Electric—transmission and distribution 5-68 $ 3,574 $ 3,431 Gas—distribution 5-75 580 547 Common—electric and gas 4-40 115 108 Construction work in progress N/A 163 107 Other property, plant and equipment (a) 10-43 16 16 Total property, plant and equipment 4,448 4,209 Less: accumulated depreciation 1,175 — 1,139 Property, plant and equipment, net $ 3,273 $ 3,070 _______________________ (a) Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien. The following table presents the annual depreciation provisions as a percentage of average service life for each asset category. Average Service Life Percentage by Asset Category 2016 2015 2014 Electric—transmission and distribution 2.49 % 2.44 % 2.41 % Gas 2.57 % 2.55 % 2.48 % Common—electric and gas 4.99 % 4.24 % 4.08 % ACE The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-55 $ 3,341 $ 3,105 Construction work in progress N/A 169 158 Other property, plant and equipment (a) 13-15 27 28 Total property, plant and equipment 3,537 3,291 Less: accumulated depreciation 1,016 — 969 Property, plant and equipment, net $ 2,521 $ 2,322 _______________________ (a) Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien. The annual depreciation provisions as a percentage of average service life for electric transmission and distribution assets were 2.45% , 2.46% and 2.48% for the years ended December 31, 2016 , 2015 and 2014 , respectively. See Note 1 — Significant Accounting Policies for further information regarding property, plant and equipment policies and accounting for capitalized software costs for the Registrants. See Note 14 — Debt and Credit Agreements for further information regarding Exelon’s, ComEd’s, and PECO’s property, plant and equipment subject to mortgage liens.

Impairment of Long-lived Assets

Impairment of Long-lived Assets (Exelon and Generation)	12 Months Ended
	Dec. 31, 2016
Impairment or Disposal of Tangible Assets Disclosure [Abstract]
Impairment Of Long-Lived Assets (Exelon and Generation)	(Exelon and Generation) Long-Lived Assets (Exelon and Generation) Generation evaluates long-lived assets or asset groups for recoverability whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. In the second quarter of 2016, updates to the Company's long-term view of energy and capacity prices suggested that the carrying value of a group of merchant wind assets, located in West Texas, may be impaired. Upon review, the estimated undiscounted future cash flows and fair value of the group were less than their carrying value. The fair value analysis was based on the income approach using significant unobservable inputs (Level 3) including revenue and generation forecasts, projected capital and maintenance expenditures and discount rates. As a result of the fair value analysis, long-lived merchant wind assets held and used with a carrying amount of approximately $60 million were written down to their fair value of $24 million and a pre-tax impairment charge of $36 million was recorded during the second quarter of 2016 in Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. Also in the second quarter of 2016, updates to the Company's long-term view, as described above, in conjunction with the retirement announcements of the Quad Cities and Clinton nuclear plants in Illinois suggested that the carrying value of our Midwest asset group may be impaired. Generation completed a comprehensive review of the estimated undiscounted future cash flows of the Midwest asset group and no impairment charge was required. In 2015, the year over year change in fundamentals did not indicate any impairments. In 2014, the year over year change in fundamentals suggested that the carrying value of certain merchant wind assets may be impaired. Generation concluded that the estimated undiscounted future cash flows and fair value of twelve wind projects, primarily located in West Texas, were less than their respective carrying values at May 31, 2014. As a result, long-lived assets held and used with a carrying amount of approximately $ 151 million were written down to their fair value of $ 65 million and a pre-tax impairment charge of $ 86 million was recorded within Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. During the first quarter of 2016, significant changes in Generation’s intended use of the Upstream oil and gas assets, developments with nonrecourse debt held by its upstream subsidiary CEU Holdings, LLC (as described in Note 14 - Debt and Credit Agreements ) and continued declines in both production volumes and commodity prices suggested that the carrying value may be impaired. Generation concluded that the estimated undiscounted future cash flows and fair value of its Upstream properties were less than their carrying values. As a result, a pre-tax impairment charge of $119 million was recorded in March 2016 within Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. On June 16, 2016, Generation initiated the sales process of its Upstream natural gas and oil exploration and production business by executing a forbearance agreement with the lenders of the nonrecourse debt, see Note 14 — Debt and Credit Agreements for additional information. An additional pre-tax impairment charge of $15 million was recorded in September 2016 within Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income due to further declines in fair value. In December 2016, Generation sold substantially all of the Upstream Assets. See Note 4 — Mergers, Acquisitions, and Dispositions for additional information. During 2015 and 2014, significant declines in oil and gas prices suggested that the carrying value of certain Upstream assets may be impaired. Generation concluded that the estimated undiscounted future cash flows and fair value of various Upstream properties, primarily located in Oklahoma and Texas, were less than their respective carrying values at December 31, 2015 and 2014. As a result, pre-tax impairment charges of $5 million and $124 million were recorded for the years ended December 31, 2015 and 2014, respectively, within Operating and maintenance expense within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. The fair value analysis used in the above impairments was primarily based on the income approach using significant unobservable inputs (Level 3) including revenue, generation and production forecasts, projected capital and maintenance expenditures and discount rates. Changes in the assumptions described above could potentially result in future impairments of Exelon’s long-lived assets, which could be material. In 2014, certain non-nuclear generating assets were identified as assets held for sale on Exelon's and Generation's Consolidated Balance Sheets. When long-lived assets are held for sale, an impairment loss is recognized to the extent that the asset's carrying value exceeds its estimated fair value less costs to sell. Long-lived assets with a carrying amount of approximately $1 billion were written down to their fair value of $556 million and a pre-tax impairment charge of $450 million was recorded within Operating and maintenance expense and is included in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income for the year ended December 31, 2014. See Note 4 — Mergers, Acquisitions, and Dispositions for further informati on on asset sales. Like-Kind Exchange Transaction (Exelon) In June 2000, UII, LLC (formerly Unicom Investments, Inc.) (UII), a wholly owned subsidiary of Exelon Corporation, entered into transactions pursuant to which UII invested in coal-fired generating station leases (Headleases) with the Municipal Electric Authority of Georgia (MEAG). The generating stations were leased back to MEAG as part of the transactions (Leases). Pursuant to the applicable accounting guidance, Exelon is required to review the estimated residual values of its direct financing lease investments at least annually and record an impairment charge if the review indicates an other than temporary decline in the fair value of the residual values below their carrying values. Exelon estimates the fair value of the residual values of its direct financing lease investments under the income approach, which uses a discounted cash flow analysis, which takes into consideration significant unobservable inputs (Level 3) including the expected revenues to be generated and costs to be incurred to operate the plants over their remaining useful lives subsequent to the lease end dates. Significant assumptions used in estimating the fair value include fundamental energy and capacity prices, fixed and variable costs, capital expenditure requirements, discount rates, tax rates, and the estimated remaining useful lives of the plants. The estimated fair values also reflect the cash flows associated with the service contract option discussed above given that a market participant would take into consideration all of the terms and conditions contained in the lease agreements. Based on the annual reviews performed in the second quarters of 2015 and 2014 , the estimated residual value of Exelon’s direct financing leases for the Georgia generating stations experienced other than temporary declines given increases in estimated long-term operating and maintenance costs in the 2015 annual review and reduced long-term energy and capacity price expectations in the 2014 annual review. As a result, Exelon recorded $24 million pre-tax impairment charges in both 2015 and 2014 for these stations. These impairment charges were recorded within Investments and Operating and maintenance expense in Exelon’s Consolidated Balance Sheets and the Consolidated Statements of Operations and Comprehensive Income, respectively. All the Headleases were terminated by the second quarter of 2016 , and no events occurred prior to the termination that required Exelon to review the estimated residual values of the direct financing lease investments in 2016 . On February 26, 2014, UII and the City Public Service Board of San Antonio, Texas (CPS) finalized an agreement to terminate the leases on the generating station located in Texas, as described above, prior to its expiration dates. As a result of the lease termination, UII received a net early termination amount of $ 335 million from CPS and wrote down the net investment in the CPS long-term lease of $ 336 million in Investments in Exelon's Consolidated Balance Sheets in 2014; resulting in a pre-tax loss of $ 1 million being reflected in Operating and maintenance expense in the Consolidated Statements of Operations and Comprehensive Income in 2014. On March 31, 2016, UII and MEAG finalized an agreement to terminate the MEAG Headleases, the MEAG Leases, and other related agreements prior to their expiration dates. As a result of the lease termination, UII received an early termination payment of $360 million from MEAG and wrote-off the $356 million net investment in the MEAG Headleases and the Leases. The transaction resulted in a pre-tax gain of $4 million which is reflected in Operating and maintenance expense in Exelon's Consolidated Statements of Operations and Comprehensive Income. See Note 15 — Income Taxes for additional information. As of December 31, 2016 , all the long-term leases had been terminated and no residual and net investment value was outstanding. At December 31, 2015 , the components of the net investment in the long-term leases consisted of estimated residual value of $639 million , unearned income of $287 million and a resulting net investment of $352 million .

Early Nuclear Plant Retirements

Early Nuclear Plant Retirements Early Nuclear Plant Retirements (Exelon, Generation)	12 Months Ended
	Dec. 31, 2016
Implications of Potential Early Plant Retirements [Abstract]
Implications Of Potential Early Retirement Disclosure [Text Block]	9 . Early Nuclear Plant Retirements (Exelon and Generation) Exelon and Generation continue to evaluate the current and expected economic value of each of Generation’s nuclear plants. Factors that will continue to affect the economic value of Generation’s nuclear plants include, but are not limited to: market power prices, results of capacity auctions, potential legislative and regulatory solutions to ensure nuclear plants are fairly compensated for their carbon-free emissions, and the impact of final rules from the EPA requiring reduction of carbon and other emissions and the efforts of states to implement those final rules. In 2015, Generation identified the Quad Cities, Clinton and Ginna nuclear plants as having the greatest risk of early retirement based on economic valuation and other factors. At that time, Exelon and Generation deferred retirement decisions on Clinton and Quad Cities until 2016 in order to participate in the 2016-2017 MISO primary reliability auction and the 2019-2020 PJM capacity auctions held in April and May 2016, respectively, as well as to provide Illinois policy makers with additional time to consider needed reforms and for MISO to consider market design changes to ensure long-term power system reliability in southern Illinois. In April 2016, Clinton cleared the MISO primary reliability auction as a price taker for the 2016-2017 planning year. The resulting capacity price was insufficient to cover cash operating costs and a risk-adjusted rate of return to shareholders. In May 2016, Quad Cities did not clear in the PJM capacity auction for the 2019-2020 planning year and will not receive capacity revenue for that period. Based on these capacity auction results, and given the lack of progress on Illinois energy legislation and MISO market reforms, on June 2, 2016 Generation announced it would move forward to shut down the Clinton and Quad Cities nuclear plants on June 1, 2017 and June 1, 2018, respectively. The current Nuclear Regulatory Commission (NRC) licenses for Clinton and Quad Cities expire in 2026 and 2032, respectively. In June 2016, as a result of the retirement decision for Clinton and Quad Cities, Exelon and Generation recognized one-time charges in Operating and maintenance expense of $146 million related to materials and supplies inventory reserve adjustments, employee-related costs and construction work-in-progress (CWIP) impairments, among other items. In addition to these one-time charges, Exelon and Generation began recognizing incremental non-cash charges to earnings stemming from shortening the expected economic useful life of Clinton and Quad Cities, including accelerated depreciation of plant assets (along with any asset retirement costs (ARC)), accelerated amortization of nuclear fuel, and additional asset retirement obligation (ARO) accretion expense associated with the changes in decommissioning timing and cost assumptions. On December 7, 2016, Illinois FEJA was signed into law by the Governor of Illinois and included a ZES that provides compensation through the procurement of ZECs targeted at preserving the environmental attributes of zero-emissions nuclear-powered generating facilities that meet specific eligibility criteria, much like the solution implemented with the New York CES. The Illinois ZES will have a 10-year duration extending from June 1, 2017 through May 31, 2027. See Note 3 - Regulatory Matters for additional discussion on the Illinois FEJA and the ZES. With the passage of the Illinois ZES, and subject to prevailing over any related potential administrative or legal challenges , in December 2016 Generation reversed its June 2016 decision to permanently cease generation operations at the Clinton and Quad Cities nuclear generating plants. Accordingly, in December 2016 Exelon and Generation reversed approximately $120 million of the one-time charges initially recorded in June 2016 associated with the early retirements primarily for employee-related costs and a materials and supplies inventory reserve adjustment. In addition, Generation updated the expected economic useful life for both facilities, to 2027 for Clinton, commensurate with the end of the Illinois ZES, and to 2032 for Quad Cities, the end of its current operating license. Depreciation was therefore adjusted beginning December 7, 2016, to reflect these extended useful life estimates. See Note 16 - Asset Retirement Obligations for additional detail on changes to the Nuclear decommissioning ARO balances resulting from the initial decision and subsequent reversal of the decision to early retire Clinton and Quad Cities. Through December 31, 2016, Exelon's and Generation's results include a net incremental $688 million of pre-tax expense associated with the initial early retirement decision for Clinton and Quad Cities, as summarized in the table below. Income statement expense (pre-tax) 2016 Depreciation and Amortization Accelerated depreciation (a) $ 712 Accelerated nuclear fuel amortization 60 Operating and Maintenance Increase ARO accretion, net of contractual offset (b) 2 Contractual offset for ARC depreciation (b) (86 ) Total $ 688 _________ (a) Reflects incremental accelerated depreciation of plant assets, including any ARC, for the period June 2, 2016, through December 6, 2016. (b) For Quad Cities based on the regulatory agreement with the Illinois Commerce Commission, decommissioning-related activities are offset within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. The offset results in an equal adjustment to the noncurrent payables to ComEd at Generation and an adjustment to the regulatory liabilities at ComEd. Likewise, ComEd has recorded an equal noncurrent affiliate receivable from Generation and corresponding regulatory liability. In New York, the Ginna and Nine Mile Point nuclear plants continue to face significant economic challenges and risk of retirement before the end of each unit’s respective operating license period (2029 for Ginna and Nine Mile Point Unit 1, and 2046 for Nine Mile Point Unit 2). On August 1, 2016, the NYPSC issued an order adopting the CES, which would provide payments to Ginna and Nine Mile Point for the environmental attributes of their production. On November 18, 2016 Ginna and Nine Mile Point executed the necessary contracts with NYSERDA, as required under the CES. Subject to prevailing over any administrative or legal challenges, the CES will allow Ginna and Nine Mile Point to continue to operate at least through the life of the program (March 31, 2029). The assumed useful life for depreciation purposes is through the end of their current operating licenses. The approved RSSA currently requires Ginna to continue operating through the RSSA term expiring on March 31, 2017 and required notification to the NYPSC if Ginna did not plan to retire shortly after the expiration of the RSSA. On September 30, 2016, Ginna filed the required notice with the NYPSC of its intent to continue operating beyond the expiry of the RSSA. Refer to Note 3 - Regulatory Matters for additional discussion on the Ginna RSSA and the New York CES. Assuming the successful implementation of the Illinois ZES and the New York CES and the continued effectiveness of these programs, Generation and CENG, through its ownership of Ginna and Nine Mile Point, no longer consider Clinton, Quad Cities, Ginna or Nine Mile Point to be at heightened risk for early retirement. However, to the extent either the Illinois ZES or the New York CES programs do not operate as expected over their full terms, each of these plants could again be at heightened risk for early retirement, which could have a material impact on Exelon’s and Generation’s future results of operations, cash flows and financial position. The Three Mile Island (TMI) nuclear plant also did not clear in the May 2016 PJM capacity auction for the 2019-2020 planning year and will not receive capacity revenue for that period. This is the second consecutive year that TMI failed to clear the capacity auction. Although the plant is committed to operate through May 2019, the plant faces continued economic challenges and Exelon and Generation are exploring all options to return it to profitability. While a portion of the Byron nuclear plant’s capacity did not clear the PJM 2019-2020 planning year capacity auction, the plant is committed to run through May 2020. The Company’s other nuclear plants in PJM cleared in the auction, except Oyster Creek, which did not participate in the auction given Exelon's and Generation’s previous commitment to cease operation of the Oyster Creek nuclear plant by the end of 2019. The following table provides the balance sheet amounts as of December 31, 2016 for significant assets and liabilities associated with TMI currently considered by management to be at the greatest risk of early retirement due to current economic valuations and other factors. (in millions) TMI Asset Balances Materials and supplies inventory $ 39 Nuclear fuel inventory, net 83 Completed plant, net 1,015 Construction work in progress 37 Liability Balances Asset retirement obligation (565 ) NRC License Renewal Term 2034 The precise timing of an early retirement date for any nuclear plant, and the resulting financial statement impacts, may be affected by a number of factors, including the status of potential regulatory or legislative solutions, results of any transmission system reliability study assessments, the nature of any co-owner requirements and stipulations, and decommissioning trust fund requirements, among other factors. However, the earliest retirement date for any plant would usually be the first year in which the unit does not have capacity or other obligations, where applicable, and just prior to its next scheduled nuclear refueling outage.

Jointly Owned Electric Utility

Jointly Owned Electric Utility Plant (Exelon, Generation, PECO, BGE, PHI, Pepco, DPL and ACE)	12 Months Ended
	Dec. 31, 2016
Public Utilities, Property, Plant and Equipment [Abstract]
Jointly Owned Electric Utility Plant (Exelon, Generation, PECO, BGE, PHI, Pepco, DPL and ACE)	Jointly Owned Electric Utility Plant (Exelon, Generation, PECO, BGE, PHI, Pepco, DPL and ACE) Exelon's, Generation's, PECO's, BGE's, PHI's and ACE's undivided ownership interests in jointly owned electric plants and transmission facilities at December 31, 2016 and 2015 were as follows: Nuclear Generation Fossil Fuel Generation Transmission Other Quad Cities Peach Bottom Salem (a) Nine Mile Point Unit 2 Wyman PA (b) NJ/ DE (c) Other (d) Operator Generation Generation PSEG Nuclear Generation FP&L First Energy PSEG/ DPL various Ownership interest 75.00 % 50.00 % 42.59 % 82.00 % 5.89 % various various various Exelon’s share at December 31, 2016: Plant (e) $ 1,054 $ 1,384 $ 596 $ 830 $ 3 $ 27 $ 97 $ 15 Accumulated depreciation (e) 515 407 186 68 3 15 52 13 Construction work in progress — 16 41 37 — — — — Exelon’s share at December 31, 2015: Plant (e) $ 1,035 $ 1,345 $ 566 $ 756 $ 3 $ 27 $ 93 $ 15 Accumulated depreciation (e) 309 368 167 42 3 15 52 13 Construction work in progress 11 18 40 56 — — — — ________________________ (a) Generation also owns a proportionate share in the fossil fuel combustion turbine at Salem, which is fully depreciated. The gross book value was $3 million at December 31, 2016 and 2015 . (b) PECO, BGE, Pepco, DPL and ACE own a 22% , 7% , 27% , 9% and 8% share, respectively, in 127 miles of 500 kV lines located in Pennsylvania as well as a 20.72% , 10.56% , 9.72% , 3.72% and 3.83% share, respectively, of a 500 kV substation immediately outside of the Conemaugh fossil generating station which supplies power to the 500 kV lines including, but not limited to, the lines noted above. (c) PECO, DPL and ACE own a 42.55% , 1% and 13.9% share, respectively in 151.3 miles of 500 kV lines located in New Jersey and Delaware Station. PECO, DPL and ACE also own a 42.55% , 7.45% and 7.45% share, respectively, in 2.5 miles of 500 kV line located over the Delaware River. ACE also has a 21.78% share in a 500 kV New Freedom Switching (d) Generation, DPL and ACE own a 44.24% , 4.83% and 11.91% share, respectively in assets located at Merrill Creek Reservoir located in New Jersey. Pepco, DPL and ACE own a 11.9% , 7.4% and 6.6% share, respectively, in Valley Forge Corporate Center. (e) Excludes asset retirement costs. Exelon’s, Generation’s, PECO’s, BGE’s, Pepco's, DPL's and ACE's undivided ownership interests are financed with their funds and all operations are accounted for as if such participating interests were wholly-owned facilities. Exelon’s, Generation’s, PECO’s, BGE’s, Pepco's, DPL's and ACE's share of direct expenses of the jointly owned plants are included in Purchased power and fuel and Operating and maintenance expenses on Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income and in Operating and maintenance expenses on PECO’s, BGE’s, Pepco, DPL's and ACE's Consolidated Statements of Operations and Comprehensive Income.

Intangible Assets (All Registra

Intangible Assets (All Registrants)	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets (All Registrants)	Intangible Assets (Exelon, Generation, ComEd, PECO, PHI, Pepco, DPL and ACE) Goodwill Exelon’s, Generation's, ComEd’s, PHI's, and DPL's gross amount of goodwill, accumulated impairment losses and carrying amount of goodwill for the years ended December 31, 2016 and 2015 were as follows: Balance at January 1, 2015 Impairment losses Balance at December 31, 2015 Goodwill from business combination Impairment losses Measurement period adjustments (b) Balance at December 31, 2016 Exelon Gross amount $ 4,655 $ — $ 4,655 $ 4,016 $ — $ (11 ) $ 8,660 Accumulated impairment loss 1,983 — 1,983 — — — 1,983 Carrying amount 2,672 — 2,672 4,016 — (11 ) 6,677 Generation Gross amount 47 — 47 — — — 47 Carrying amount 47 — 47 — — — 47 ComEd (a) Gross amount 4,608 — 4,608 — — — 4,608 Accumulated impairment loss 1,983 — 1,983 — — — 1,983 Carrying amount 2,625 — 2,625 — — — 2,625 DPL Gross amount 8 — 8 — — — 8 Carrying amount 8 — 8 — — — 8 March 24, 2016 to December 31, 2016 Beginning Balance Goodwill from business combination Impairment losses Measurement period adjustments (b) Ending Balance PHI - Successor Gross amount $ — $ 4,016 $ — $ (11 ) $ 4,005 Accumulated impairment loss — — — — — Carrying amount — 4,016 — (11 ) 4,005 January 1, 2016 to March 23, 2016 PHI - Predecessor Gross amount 1,418 — — — 1,418 Accumulated impairment loss 12 — — — 12 Carrying amount 1,406 — — — 1,406 For the Year Ended December 31, 2015 PHI - Predecessor Gross amount 1,425 — (7 ) — 1,418 Accumulated impairment loss 18 — (6 ) — 12 Carrying amount 1,407 — (1 ) — 1,406 ______________________ (a) Reflects goodwill recorded in 2000 from the PECO/Unicom (predecessor parent company of ComEd) merger net of amortization, resolution of tax matters and other non-impairment-related changes as allowed under previous authoritative guidance. (b) Represents various measurement period adjustments to the valuation of the fair value of the PHI assets acquired and liabilities assumed as a result of the merger. Goodwill is not amortized, but is subject to an assessment for impairment at least annually, or more frequently if events occur or circumstances change that would more likely than not reduce the fair value of the Exelon, Generation, ComEd, PHI and DPL reporting unit below its carrying amount. Under the authoritative guidance for goodwill, a reporting unit is an operating segment or one level below an operating segment (known as a component) and is the level at which goodwill is tested for impairment. A component of an operating segment is a reporting unit if the component constitutes a business for which discrete financial information is available and its operating results are regularly reviewed by segment management. Generation's operating segments are Mid-Atlantic, Midwest, New England, New York, ERCOT and all other power regions referred to collectively as “Other Power Regions”, PHI's operating segments are Pepco, DPL and ACE, and ComEd and DPL have a single operating segment. See Note 26 — Segment Information for additional information. There is no level below these operating segments for which operating results are regularly reviewed by segment management. Therefore, the ComEd, Pepco, DPL and ACE operating segments are also considered reporting units for goodwill impairment testing purposes. Exelon's and ComEd's $2.6 billion of goodwill has been assigned entirely to the ComEd reporting unit, while Exelon's and PHI's $4 billion of goodwill has been assigned to the Pepco, DPL and ACE reporting units in the amounts of $1.7 billion , $1.1 billion and $1.2 billion , respectively. DPL's $8 million of goodwill is assigned entirely to the DPL reporting unit. Entities assessing goodwill for impairment have the option of first performing a qualitative assessment to determine whether a quantitative assessment is necessary. In performing a qualitative assessment, entities should assess, among other things, macroeconomic conditions, industry and market considerations, overall financial performance, cost factors and entity-specific events. If an entity determines, on the basis of qualitative factors, that the fair value of the reporting unit is more likely than not greater than the carrying amount, no further testing is required. If an entity bypasses the qualitative assessment or performs the qualitative assessment, but determines that it is more likely than not that its fair value is less than its carrying amount, a quantitative two-step, fair value-based test is performed. Exelon's, Generation's, ComEd's, PHI's and DPL's accounting policy is to perform a quantitative test of goodwill at least once every three years. The first step in the quantitative test compares the fair value of the reporting unit to its carrying amount, including goodwill. If the carrying amount of the reporting unit exceeds its fair value, the second step is performed. The second step requires an allocation of fair value to the individual assets and liabilities using purchase price allocation accounting guidance in order to determine the implied fair value of goodwill. If the implied fair value of goodwill is less than the carrying amount, an impairment loss is recorded as a reduction to goodwill and a charge to operating expense. Application of the goodwill impairment test requires management judgment, including the identification of reporting units and determining the fair value of the reporting unit, which management estimates using a weighted combination of a discounted cash flow analysis and a market multiples analysis. Significant assumptions used in these fair value analyses include discount and growth rates, utility sector market performance and transactions, projected operating and capital cash flows for Generation's, ComEd's, Pepco's, DPL's and ACE's businesses and the fair value of debt. In applying the second step (if needed), management must estimate the fair value of specific assets and liabilities of the reporting unit. 2016 and 2015 Goodwill Impairment Assessment. Generation performed a qualitative test as of November 1, 2016, for its 2016 annual goodwill impairment assessment. Generation previously completed its last quantitative assessment in the first quarter of 2015, and updated its qualitative assessment as of November 1, 2015. Based on the qualitative factors above, Generation concluded that the fair value of the reporting unit is more likely than not greater than the carrying amount, and no further testing was required. Exelon, ComEd, PHI, and DPL performed quantitative tests as of November 1, 2016, for their 2016 annual goodwill impairment assessments. The first step of the tests comparing the estimated fair values of the ComEd, Pepco, DPL, and ACE reporting units to their carrying values, including goodwill, indicated no impairments of goodwill; therefore, no second steps were required. While the annual assessments indicated no impairments, certain assumptions used to estimate reporting unit fair values are highly sensitive to changes. Adverse regulatory actions or changes in significant assumptions could potentially result in future impairments of Exelon’s, ComEd's, PHI’s or DPL’s goodwill, which could be material. Based on the results of the annual goodwill test performed as of November 1, 2016, the estimated fair values of the ComEd, Pepco, DPL and ACE reporting units would have needed to decrease by more than 30% , 10% , 10% and 10% , respectively, for Exelon, ComEd and PHI to fail the first step of their respective impairment tests. The $8 million of goodwill recorded at DPL is related to DPL’s 1995 acquisition of the Conowingo Power Company and the fair value of the DPL reporting unit would have needed to decrease by more than 50% for DPL to fail the first step of the impairment test. As of November 1, 2015, Exelon, ComEd, and PHI qualitatively determined that the fair value of their reporting units was not more likely than not less than their carrying value and, therefore, did not perform quantitative assessments. As part of their qualitative assessments, Exelon, ComEd and PHI evaluated, among other things, management’s best estimate of projected operating and capital cash flows for their respective business, as well as, changes in certain market conditions, including the discount rate and regulated utility peer company EBITDA multiples, while also considering, the passing margin from their last quantitative assessments. Other Intangible Assets and Liabilities Exelon’s, Generation’s, ComEd’s and PHI's other intangible assets and liabilities, included in Unamortized energy contract assets and liabilities and Other deferred debits and other assets in their Consolidated Balance Sheets, consisted of the following as of December 31, 2016 : Weighted Average Amortization Years (l) Estimated amortization expense Gross Accumulated Amortization Net 2017 2018 2019 2020 2021 Exelon Software License Agreement (a) 10.0 $ 95 $ (15 ) $ 80 $ 10 $ 10 $ 10 $ 10 $ 10 Generation Unamortized Energy Contracts (b) Exelon Wind (c) 18.0 224 (83 ) 141 14 14 14 10 10 Antelope Valley (d) 25 190 (28 ) 162 8 8 8 8 8 Constellation (e) 1.5 1,499 (1,440 ) 59 (21 ) 11 8 10 10 CENG (f) 1.7 (97 ) 59 (38 ) (15 ) (18 ) (15 ) (8 ) (4 ) Integrys (g) 2.4 5 (3 ) 2 1 1 — — — ConEdison (h) 1.5 100 (53 ) 47 37 7 2 1 — Service Contract Backlog PES (h) 1.0 9 (7 ) 2 2 — — — — Customer Relationships (i) Constellation (e) 12.4 214 (94 ) 120 18 18 17 17 17 Integrys (g) 10.0 50 (11 ) 39 5 5 5 5 5 PES (h) 15.0 12 (1 ) 11 1 1 1 1 1 ConEdison (h) 10.0 9 — 9 1 1 1 1 1 Trade Names Constellation (e) 10.0 243 (125 ) 118 23 23 23 23 23 ComEd Chicago settlement—1999 agreement (j) 21.8 100 (86 ) 14 3 3 3 3 — Chicago settlement—2003 agreement (k) 17.9 62 (47 ) 15 4 4 4 4 — PHI Unamortized Energy Contracts (h) 6.8 (1,515 ) 430 (1,085 ) (335 ) (189 ) (119 ) (115 ) (92 ) Pepco DC Sponsorship Agreement (m) 0 25 — 25 — — — — — Total $ 1,225 $ (1,504 ) $ (279 ) $ (244 ) $ (101 ) $ (38 ) $ (30 ) $ (11 ) _________________________ (a) On May 31, 2015, Exelon entered into a long-term software license agreement. Exelon is required to make payments starting August 2015 through May 2024. The intangible asset recognized as a result of these payments is being amortized on a straight-line basis over the contract term. (b) Includes unamortized energy contract assets and liabilities on Exelon's and Generation's Consolidated Balance Sheets. Excludes $10 million of other miscellaneous unamortized energy contracts that have been acquired at various points in time. The estimated amortization for these miscellaneous unamortized energy contracts is $(9) million , $(7) million , $(6) million , $(2) million and $4 million for 2017 , 2018 , 2019 , 2020 and 2021 , respectively. (c) In December 2010, Generation acquired all of the equity interests of John Deere Renewables, LLC (later named Exelon Wind), adding 735 MWs of installed, operating wind capacity located in eight states. (d) In September 2011, Generation acquired all of the interest in Antelope Valley Solar Ranch One, a 242 MW solar project in northern Los Angeles County, CA from First Solar, Inc. (e) On March 12, 2012, Constellation merged into Exelon with Exelon continuing as the surviving corporation pursuant to the transactions contemplated by the Agreement and Plan of Merger. Since the merger transaction, Generation includes the former Constellation generation and customer supply operations. (f) See Note 5 — Investment in Constellation Energy Nuclear Group, LLC for additional information. (g) On November 1, 2014, Generation acquired the competitive retail electric and natural gas business activities of Integrys Energy Group, Inc. (h) See Note 4 — Mergers, Acquisitions, and Dispositions for additional information. (i) Excludes $11 million of other miscellaneous customer relationships that have been acquired. The estimated amortization for these miscellaneous customer relationships is $1 million in each of the years from 2017 to 2021 . (j) In March 1999, ComEd entered into a settlement agreement with the City of Chicago associated with ComEd’s franchise agreement. Under the terms of the settlement, ComEd agreed to make payments to the City of Chicago each year from 1999 to 2002. The intangible asset recognized as a result of these payments is being amortized ratably over the remaining term of the franchise agreement, which ends in 2020. (k) In February 2003, ComEd entered into separate agreements with the City of Chicago and with Midwest Generation, LLC (Midwest Generation). Under the terms of the settlement agreement with the City of Chicago, ComEd agreed to pay the City of Chicago a total of $60 million over a ten -year period, beginning in 2003. The intangible asset recognized as a result of the settlement agreement is being amortized ratably over the remaining term of the City of Chicago franchise agreement, which ends in 2020. As required by the settlement, ComEd also made a payment of $2 million to a third-party on the City of Chicago’s behalf. Under the terms of the agreement with Midwest Generation, ComEd received payments of $32 million from Midwest Generation to relieve Midwest Generation’s obligation under the 1999 fossil sale agreement with ComEd to build the generation facility in the City of Chicago. The payments received by ComEd, which have been recorded in Other deferred credits and other liabilities, and other long-term liabilities on Exelon's and ComEd's Consolidated Balance Sheets are being recognized ratably (approximately $2 million annually) as an offset to amortization expense over the remaining term of the franchise agreement. (l) Weighted-average amortization period was calculated at the date of a) acquisition for acquired assets or b) settlement agreement. (m) In the third quarter of 2015, Pepco entered into a sponsorship agreement with the District of Columbia for future naming rights associated with public property within the District of Columbia to be determined over time through future negotiations. Amortization of the intangible asset will begin once the terms of the naming rights are defined. The following table summarizes the amortization expense related to intangible assets and liabilities for each of the years ended December 31, 2016 , 2015 and 2014 : For the Year Ended December 31, Exelon (a) Generation (a) ComEd 2016 $ 87 $ 79 $ 7 2015 76 69 7 2014 179 179 7 ________________________ (a) At Exelon, amortization of unamortized energy contracts totaling $35 million , $22 million and $135 million for the years ended December 31, 2016 , 2015 and 2014 , respectively, was recorded in Operating revenues or Purchase power and fuel expense within Exelon’s Consolidated Statements of Operations and Comprehensive Income. At Generation, amortization of unamortized energy contracts totaling $35 million , $22 million and $135 million for the years ended December 31, 2016 , 2015 and 2014 , respectively, was recorded in Operating revenues or Purchase power and fuel expense within Generation’s Consolidated Statements of Operations and Comprehensive Income Acquired Intangible Assets and Liabilities Accounting guidance for business combinations requires the acquirer to separately recognize identifiable intangible assets in the application of purchase accounting. Unamortized Energy Contracts. Unamortized energy contract assets and liabilities represent the remaining unamortized fair value of non-derivative energy contracts that Exelon and Generation have acquired. The valuation of unamortized energy contracts was estimated by applying either the market approach or the income approach depending on the nature of the underlying contract. The market approach was utilized when prices and other relevant information generated by market transactions involving comparable transactions were available. Otherwise, the income approach, which is based upon discounted projected future cash flows associated with the underlying contracts, was utilized. The fair value is based upon certain unobservable inputs, which are considered Level 3 inputs, pursuant to applicable accounting guidance. Key estimates and inputs include forecasted power and fuel prices and the discount rate. The Exelon Wind unamortized energy contracts are amortized on a straight line basis over the period in which the associated contract revenues are recognized as a decrease in Operating revenues within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. In the case of Antelope Valley, Constellation, CENG, Integrys and ConEdison, the fair value amounts are amortized over the life of the contract in relation to the present value of the underlying cash flows as of the acquisition dates through either Operating revenues or Purchase power and fuel expense within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. At PHI, offsetting regulatory assets or liabilities were also recorded. The unamortized energy contract assets and liabilities and any corresponding regulatory assets or liabilities, respectively, are amortized over the life of the contract in relation to the expected realization of the underlying cash flows. Customer Relationships. The customer relationship intangibles were determined based on a “multi-period excess method” of the income approach. Under this method, the intangible asset’s fair value is determined to be the estimated future cash flows that will be earned on the current customer base, taking into account expected contract renewals based on customer attrition rates and costs to retain those customers. The fair value is based upon certain unobservable inputs, which are considered Level 3 inputs, pursuant to applicable accounting guidance. Key assumptions include the customer attrition rate and the discount rate. The accounting guidance requires that customer-based intangibles be amortized over the period expected to be benefited using the pattern of economic benefit. The amortization of the customer relationships recorded in Depreciation and amortization expense within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. Service Contract Backlog. The service contract backlog intangibles were determined based on a “multi-period excess method” of the income approach. Under this method, the intangible asset’s fair value is determined to be the estimated future cash flows that will be earned on the contracts. The fair value is based upon certain unobservable inputs, which are considered Level 3 inputs, pursuant to applicable accounting guidance. Key assumptions include estimated revenues and expenses to complete the contracts as well as the discount rate. The accounting guidance requires that customer-based intangibles be amortized over the period expected to be benefited using the pattern of economic benefit. The amortization of the service contract backlog is recorded in Depreciation and amortization expense within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. Trade Name. The Constellation trade name intangible was determined based on the relief from royalty method of income approach whereby fair value is determined to be the present value of the license fees avoided by owning the assets. The fair value is based upon certain unobservable inputs, which are considered Level 3 inputs, pursuant to applicable accounting guidance. Key assumptions include the hypothetical royalty rate and the discount rate. The Constellation trade name intangible is amortized on a straight-line basis over a period of 10 years . The amortization of the trade name is recorded in Depreciation and amortization expense within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. Renewable Energy Credits and Alternative Energy Credits (Exelon, Generation, ComEd, PECO, DPL and ACE) Exelon’s, Generation’s, ComEd’s, PECO's, DPL's and ACE's other intangible assets, included in Other current assets and Other deferred debits and other assets on the Consolidated Balance Sheets, include RECs (Exelon, Generation, ComEd, DPL and ACE) and AECs (Exelon and PECO). Purchased RECs are recorded at cost on the date they are purchased. The cost of RECs purchased on a stand-alone basis is based on the transaction price, while the cost of RECs acquired through PPAs represents the difference between the total contract price and the market price of energy at contract inception. Generally, revenue for RECs that are part of a bundled power sale is recognized when the power is produced and delivered to the customer, otherwise, the revenue is recognized upon physical transfer of the REC. As of December 31, 2016 , and 2015 , PECO had current AECs of $1 million and $2 million , respectively. PECO had no noncurrent AECs as of December 31, 2016 and 2015 . As of December 31, 2016 , and 2015 , Generation had current RECs of $317 million and $251 million , respectively, and $29 million and $56 million of noncurrent REC's, respectively. ComEd had no current RECs as of December 31, 2016 and $5 million as of December 31, 2015 . ComEd had no noncurrent RECs as of December 31, 2016 and 2015 . As of December 31, 2016 and 2015 , DPL had current RECs of $11 million and $9 million , respectively. DPL had no noncurrent RECs as of December 31, 2016 and 2015 . As of December 31, 2016 and 2015 , ACE had current RECs of $1 million . ACE had no noncurrent RECs as of December 31, 2016 and 2015 . See Note 3 — Regulatory Matters and Note 24 — Commitments and Contingencies for additional information on RECs and AECs.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities (All Registrants)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities (All Registrants)	12 . Fair Value of Financial Assets and Liabilities (All Registrants) Fair Value of Financial Liabilities Recorded at the Carrying Amount The following tables present the carrying amounts and fair values of the Registrants’ short-term liabilities, long-term debt, SNF obligation, and trust preferred securities (long-term debt to financing trusts or junior subordinated debentures) as of December 31, 2016 and 2015 : Exelon December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 1,267 $ — $ 1,267 $ — $ 1,267 Long-term debt (including amounts due within one year) (a) 34,005 1,113 31,741 1,959 34,813 Long-term debt to financing trusts (b) 641 — — 667 667 SNF obligation 1,024 — 732 — 732 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 536 $ 3 $ 533 $ — $ 536 Long-term debt (including amounts due within one year) (a) 25,145 931 23,644 1,349 25,924 Long-term debt to financing trusts (b) 641 — — 673 673 SNF obligation 1,021 — 818 — 818 Generation December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 699 $ — $ 699 $ — $ 699 Long-term debt (including amounts due within one year) (a) 9,241 — 7,482 1,670 9,152 SNF obligation 1,024 — 732 — 732 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 29 $ — $ 29 $ — $ 29 Long-term debt (including amounts due within one year) (a) 8,959 — 7,767 1,349 9,116 SNF obligation 1,021 — 818 — 818 ComEd December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 7,033 $ — $ 7,585 $ — $ 7,585 Long-term debt to financing trusts (b) 205 — — 215 215 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 294 $ — $ 294 $ — $ 294 Long-term debt (including amounts due within one year) (a) 6,509 — 7,069 — 7,069 Long-term debt to financing trusts (b) 205 — — 213 213 PECO December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,580 $ — $ 2,794 $ — $ 2,794 Long-term debt to financing trusts 184 — — 192 192 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,580 $ — $ 2,786 $ — $ 2,786 Long-term debt to financing trusts 184 — — 195 195 BGE December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 45 $ — $ 45 $ — $ 45 Long-term debt (including amounts due within one year) (a) 2,322 — 2,467 — 2,467 Long-term debt to financing trusts (b) 252 — — 260 260 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 213 $ 3 $ 210 $ — $ 213 Long-term debt (including amounts due within one year) (a) 1,858 — 2,044 — 2,044 Long-term debt to financing trusts (b) 252 — — 264 264 PHI December 31, 2016 Carrying Amount Fair Value Successor Level 1 Level 2 Level 3 Total Short-term liabilities $ 522 $ — $ 522 $ — $ 522 Long-term debt (including amounts due within one year) (a) 5,898 — 5,520 289 5,809 December 31, 2015 Carrying Amount Fair Value Predecessor Level 1 Level 2 Level 3 Total Short-term liabilities $ 958 $ — $ 958 $ — $ 958 Long-term debt (including amounts due within one year) (a) 5,279 — 5,231 586 5,817 Preferred stock 183 — — 183 183 Pepco December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 23 $ — $ 23 $ — $ 23 Long-term debt (including amounts due within one year) (a) 2,349 — 2,788 8 2,796 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 64 $ — $ 64 $ — $ 64 Long-term debt (including amounts due within one year) (a) 2,351 — 2,673 — 2,673 DPL December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 1,340 $ — $ 1,383 $ — $ 1,383 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 105 $ — $ 105 $ — $ 105 Long-term debt (including amounts due within one year) (a) 1,265 — 1,185 103 1,288 ACE December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 1,155 $ — $ 1,007 $ 280 $ 1,287 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 5 $ — $ 5 $ — $ 5 Long-term debt (including amounts due within one year) (a) 1,201 — 1,044 280 1,324 ________ (a) Includes unamortized debt issuance costs, which are not fair valued, of $200 million , $64 million , $46 million , $15 million , $15 million , $2 million , $30 million , $11 million , and $6 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE respectively, as of December 31, 2016 . Includes unamortized debt issuance costs, which are not fair valued, of $180 million , $70 million , $38 million , $15 million , $9 million , $49 million , $31 million , $10 million , and $6 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE respectively, as of December 31, 2015 . (b) Includes unamortized debt issuance costs which are not fair valued of $7 million , $1 million and $6 million for Exelon, ComEd and BGE, respectively, as of December 31, 2016 and December 31, 2015 . Short-Term Liabilities. The short-term liabilities included in the tables above are comprised of dividends payable (included in other current liabilities) (Level 1) and short-term borrowings (Level 2). The Registrants’ carrying amounts of the short-term liabilities are representative of fair value because of the short-term nature of these instruments. Long-Term Debt. The fair value amounts of Exelon’s taxable debt securities (Level 2) and private placement taxable debt securities (Level 3) are determined by a valuation model that is based on a conventional discounted cash flow methodology and utilizes assumptions of current market pricing curves. In order to incorporate the credit risk of the Registrants into the discount rates, Exelon obtains pricing (i.e., U.S. Treasury rate plus credit spread) based on trades of existing Exelon debt securities as well as debt securities of other issuers in the utility sector with similar credit ratings in both the primary and secondary market, across the Registrants’ debt maturity spectrum. The credit spreads of various tenors obtained from this information are added to the appropriate benchmark U.S. Treasury rates in order to determine the current market yields for the various tenors. The yields are then converted into discount rates of various tenors that are used for discounting the respective cash flows of the same tenor for each bond or note. Due to low trading volume of private placement debt, qualitative factors such as market conditions, low volume of investors and investor demand, this debt is classified as Level 3. The fair value of Exelon's equity units (Level 1) are valued based on publicly traded securities issued by Exelon. The fair value of Generation’s, Pepco's and PHI's non-government-backed fixed rate nonrecourse debt (Level 3) is based on market and quoted prices for its own and other nonrecourse debt with similar risk profiles. Given the low trading volume in the nonrecourse debt market, the price quotes used to determine fair value will reflect certain qualitative factors, such as market conditions, investor demand, new developments that might significantly impact the project cash flows or off-taker credit, and other circumstances related to the project (e.g., political and regulatory environment). The fair value of Generation’s government-backed fixed rate project financing debt (Level 3) is largely based on a discounted cash flow methodology that is similar to the taxable debt securities methodology described above. Due to the lack of market trading data on similar debt, the discount rates are derived based on the original loan interest rate spread to the applicable Treasury rate as well as a current market curve derived from government-backed securities. Variable rate project financing debt resets on a monthly or quarterly basis and the carrying value approximates fair value (Level 2). When trading data is available on variable rate project financing debt, the fair value is based on market and quoted prices for its own and other nonrecourse debt with similar risk profiles (Level 2). Generation, Pepco, DPL and ACE also have tax-exempt debt (Level 2). Due to low trading volume in this market, qualitative factors, such as market conditions, investor demand, and circumstances related to the issuer (e.g., conduit issuer political and regulatory environment), may be incorporated into the credit spreads that are used to obtain the fair value as described above. Variable rate tax-exempt debt (Level 2) resets on a regular basis and the carrying value approximates fair value. SNF Obligation . The carrying amount of Generation’s SNF obligation (Level 2) is derived from a contract with the DOE to provide for disposal of SNF from Generation’s nuclear generating stations. When determining the fair value of the obligation, the future carrying amount of the SNF obligation is calculated by compounding the current book value of the SNF obligation at the 13-week Treasury rate. The compounded obligation amount is discounted back to present value using Generation’s discount rate, which is calculated using the same methodology as described above for the taxable debt securities, and an estimated maturity date of 2030 and 2025 as of December 31, 2016 and 2015 , respectively. See Note 24 - Commitments and Contingencies for additional information regarding the change in estimated settlement date. Long-Term Debt to Financing Trusts . Exelon’s long-term debt to financing trusts is valued based on publicly traded securities issued by the financing trusts. Due to low trading volume of these securities, qualitative factors, such as market conditions, investor demand, and circumstances related to each issue, this debt is classified as Level 3. Preferred Stock . The fair value of these securities is determined based on the carrying value of the shares per the Subscription Agreement between PHI and Exelon. See Note 19 - Mezzanine Equity for further details. Recurring Fair Value Measurements Exelon records the fair value of assets and liabilities in accordance with the hierarchy established by the authoritative guidance for fair value measurements. The hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels as follows: • Level 1 — quoted prices (unadjusted) in active markets for identical assets or liabilities that the Registrants have the ability to liquidate as of the reporting date. • Level 2 — inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. • Level 3 — unobservable inputs, such as internally developed pricing models or third-party valuations for the asset or liability due to little or no market activity for the asset or liability. Transfers in and out of levels are recognized as of the end of the reporting period when the transfer occurred. Given derivatives categorized within Level 1 are valued using exchange-based quoted prices within observable periods, transfers between Level 2 and Level 1 were not material. Additionally, there were no significant transfers between Level 1 and Level 2 during the year ended December 31, 2016 for cash equivalents, nuclear decommissioning trust fund investments, pledged assets for Zion Station decommissioning, Rabbi trust investments, and deferred compensation obligations. For derivative contracts, transfers into Level 2 from Level 3 generally occur when the contract tenor becomes more observable and due to changes in market liquidity or assumptions for certain commodity contracts. Generation and Exelon In accordance with the applicable guidance on fair value measurement, certain investments that are measured at fair value using the NAV per share as a practical expedient are no longer classified within the fair value hierarchy and are included under "Not subject to leveling" in the table below. See Note 1 - Significant Accounting Policies for additional information. The following tables present assets and liabilities measured and recorded at fair value on Exelon's and Generation’s Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and 2015 : Generation Exelon As of December 31, 2016 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 39 $ — $ — $ — $ 39 $ 373 $ — $ — $ — $ 373 NDT fund investments Cash equivalents (b) 110 19 — — 129 110 19 — — 129 Equities 3,551 452 — 2,011 6,014 3,551 452 — 2,011 6,014 Fixed income Corporate debt — 1,554 250 — 1,804 — 1,554 250 — 1,804 U.S. Treasury and agencies 1,291 29 — — 1,320 1,291 29 — — 1,320 Foreign governments — 37 — — 37 — 37 — — 37 State and municipal debt — 264 — — 264 — 264 — — 264 Other (c) — 59 — 493 552 — 59 — 493 — 552 Fixed income subtotal 1,291 1,943 250 493 3,977 1,291 1,943 250 493 3,977 Middle market lending — — 427 71 498 — — 427 71 498 Private equity — — — 148 148 — — — 148 148 Real estate — — — 326 326 — — — 326 326 NDT fund investments subtotal (d) 4,952 2,414 677 3,049 11,092 4,952 2,414 677 3,049 11,092 Pledged assets for Zion Station decommissioning Cash equivalents 11 — — — 11 11 — — — 11 Equities — 2 — — 2 — 2 — — 2 Fixed Income - U.S. Treasury and agencies 16 1 — — 17 16 1 — — 17 Middle market lending — — 19 64 83 — — 19 64 83 Pledged assets for Zion Station decommissioning subtotal (e) 27 3 19 64 113 27 3 19 64 113 Rabbi trust investments Cash equivalents 2 — — — 2 74 — — — 74 Mutual funds 19 — — — 19 50 — — — 50 Generation Exelon As of December 31, 2016 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Fixed income — — — — — — 16 — — 16 Life insurance contracts — 18 — — 18 — 64 20 — 84 Rabbi trust investments subtotal 21 18 — — 39 124 80 20 — 224 Commodity derivative assets Economic hedges 1,356 2,505 1,229 — 5,090 1,358 2,505 1,229 — 5,092 Proprietary trading 3 50 23 — 76 3 50 23 — 76 Effect of netting and allocation of collateral (f) (1,162 ) (2,142 ) (481 ) — (3,785 ) (1,164 ) (2,142 ) (481 ) — (3,787 ) Commodity derivative assets subtotal 197 413 771 — 1,381 197 413 771 — 1,381 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 16 — — 16 Economic hedges — 28 — — 28 — 28 — — 28 Proprietary trading 3 2 — — 5 3 2 — — 5 Effect of netting and allocation of collateral (2 ) (19 ) — — (21 ) (2 ) (19 ) — — (21 ) Interest rate and foreign currency derivative assets subtotal 1 11 — — 12 1 27 — — 28 Other investments — — 42 — 42 — — 42 — 42 Total assets 5,237 2,859 1,509 3,113 12,718 5,674 2,937 1,529 3,113 13,253 Liabilities Commodity derivative liabilities Economic hedges (1,267 ) (2,378 ) (794 ) — (4,439 ) (1,267 ) (2,378 ) (1,052 ) — (4,697 ) Proprietary trading (3 ) (50 ) (26 ) — (79 ) (3 ) (50 ) (26 ) — (79 ) Effect of netting and allocation of collateral (f) 1,233 2,339 542 — 4,114 1,233 2,339 542 — 4,114 Commodity derivative liabilities subtotal (37 ) (89 ) (278 ) — (404 ) (37 ) (89 ) (536 ) — (662 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (10 ) — — (10 ) — (10 ) — — (10 ) Economic hedges — (21 ) — — (21 ) — (21 ) — — (21 ) Proprietary trading (4 ) — — — (4 ) (4 ) — — — (4 ) Effect of netting and allocation of collateral 4 19 — — 23 4 19 — — 23 Interest rate and foreign currency derivative liabilities subtotal — (12 ) — — (12 ) — (12 ) — — (12 ) Deferred compensation obligation — (34 ) — — (34 ) — (136 ) — (136 ) Total liabilities (37 ) (135 ) (278 ) — (450 ) (37 ) (237 ) (536 ) — (810 ) Total net assets $ 5,200 $ 2,724 $ 1,231 $ 3,113 $ 12,268 $ 5,637 $ 2,700 $ 993 $ 3,113 $ 12,443 Generation Exelon As of December 31, 2015 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 104 $ — $ — $ — $ 104 $ 5,766 $ — $ — $ — $ 5,766 NDT fund investments Cash equivalents (b) 219 92 — — 311 219 92 — — 311 Equities 3,008 — — 1,894 4,902 3,008 — — 1,894 4,902 Generation Exelon As of December 31, 2015 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Fixed income Corporate debt — 1,824 242 — 2,066 — 1,824 242 — 2,066 U.S. Treasury and agencies 1,323 15 — — 1,338 1,323 15 — — 1,338 Foreign governments — 61 — — 61 — 61 — — 61 State and municipal debt — 326 — — 326 — 326 — — 326 Other (c) — 147 — 390 537 — 147 — 390 537 Fixed income subtotal 1,323 2,373 242 390 4,328 1,323 2,373 242 390 4,328 Middle market lending — — 428 — 428 — — 428 — 428 Private equity — — — 125 125 — — — 125 125 Real estate — — — 35 35 — — — 35 35 Other — — — 216 216 — — — 216 216 Nuclear decommissioning trust fund investments subtotal (d) 4,550 2,465 670 2,660 10,345 4,550 2,465 670 2,660 10,345 Pledged assets for Zion Station decommissioning Cash equivalents — 17 — — 17 — 17 — — 17 Equities 1 5 — — 6 1 5 — — 6 Fixed income U.S. Treasury and agencies 6 2 — — 8 6 2 — — 8 Corporate debt — 46 — — 46 — 46 — — 46 Other — 1 — — 1 — 1 — — 1 Fixed income subtotal 6 49 — — 55 6 49 — — 55 Middle market lending — — 22 105 127 — — 22 105 127 Pledged assets for Zion Station decommissioning subtotal (e) 7 71 22 105 205 7 71 22 105 205 Rabbi trust investments Mutual funds 17 — — — 17 48 — — — 48 Life insurance contracts — 13 — — 13 — 36 — — 36 Rabbi trust investments subtotal 17 13 — — 30 48 36 — — 84 Commodity derivative assets Economic hedges 1,922 3,467 1,707 — 7,096 1,922 3,467 1,707 — 7,096 Proprietary trading 36 64 30 — 130 36 64 30 — 130 Effect of netting and allocation of collateral (f) (1,964 ) (2,629 ) (564 ) — (5,157 ) (1,964 ) (2,629 ) (564 ) — (5,157 ) Commodity derivative assets subtotal (6 ) 902 1,173 — 2,069 (6 ) 902 1,173 — 2,069 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 25 — — 25 Economic hedges — 20 — — 20 — 20 — — 20 Proprietary trading 10 5 — — 15 10 5 — — 15 Effect of netting and allocation of collateral (3 ) (3 ) — — (6 ) (3 ) (3 ) — — (6 ) Interest rate and foreign currency derivative assets subtotal 7 22 — — 29 7 47 — — 54 Other investments — — 33 — 33 — — 33 — 33 Total assets 4,679 3,473 1,898 2,765 12,815 10,372 3,521 1,898 2,765 18,556 Liabilities Commodity derivative liabilities Generation Exelon As of December 31, 2015 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Economic hedges (2,382 ) (3,348 ) (850 ) — (6,580 ) (2,382 ) (3,348 ) (1,097 ) — (6,827 ) Proprietary trading (33 ) (57 ) (37 ) — (127 ) (33 ) (57 ) (37 ) — (127 ) Effect of netting and allocation of collateral (f) 2,440 3,186 765 — 6,391 2,440 3,186 765 — 6,391 Commodity derivative liabilities subtotal 25 (219 ) (122 ) — (316 ) 25 (219 ) (369 ) — (563 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (16 ) — — (16 ) — (16 ) — — (16 ) Economic hedges — (3 ) — — (3 ) — (3 ) — — (3 ) Proprietary trading (12 ) — — — (12 ) (12 ) — — — (12 ) Effect of netting and allocation of collateral 12 3 — — 15 12 3 — — 15 Interest rate and foreign currency derivative liabilities subtotal — (16 ) — — (16 ) — (16 ) — — (16 ) Deferred compensation obligation — (30 ) — — (30 ) — (99 ) — — (99 ) Total liabilities 25 (265 ) (122 ) — (362 ) 25 (334 ) (369 ) — (678 ) Total net assets $ 4,704 $ 3,208 $ 1,776 $ 2,765 $ 12,453 $ 10,397 $ 3,187 $ 1,529 $ 2,765 $ 17,878 _________________________ (a) Generation excludes cash of $252 million and $329 million at December 31, 2016 and 2015 and restricted cash of $157 million and $121 million at December 31, 2016 and 2015 . Exelon excludes cash of $360 million and $763 million at December 31, 2016 and 2015 and restricted cash of $180 million and $178 million at December 31, 2016 and 2015 and includes long term restricted cash of $25 million at December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) Includes $29 million and $52 million of cash received from outstanding repurchase agreements at December 31, 2016 and 2015 , respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (d) below. (c) Includes derivative instruments of $(2) million and $(8) million , which have a total notional amount of $933 million and $1,236 million at December 31, 2016 and 2015 , respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the fiscal years ended and do not represent the amount of the company's exposure to credit or market loss. (d) Excludes net liabilities of $(31) million and $(3) million at December 31, 2016 and 2015 , respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, repurchase agreement obligations, and payables related to pending securities purchases. The repurchase agreements are generally short-term in nature with durations generally of 30 days or less. (e) Excludes net assets of less than $1 million and $1 million at December 31, 2016 and 2015 , respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (f) Collateral posted to/(received from) counterparties totaled $71 million , $197 million and $61 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2016 . Collateral posted to/(received from) counterparties totaled $476 million , $557 million and $201 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2015 . ComEd, PECO and BGE The following tables present assets and liabilities measured and recorded at fair value on ComEd's, PECO's and BGE's Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and 2015 : ComEd PECO BGE As of December 31, 2016 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 20 $ — $ — $ 20 $ 45 $ — $ — $ 45 $ 36 $ — $ — $ 36 Rabbi trust investments Mutual funds — — — — 7 — — 7 4 — — 4 Life insurance contracts — — — — — 10 — 10 — — — — Rabbi trust investments subtotal — — — — 7 10 — 17 4 — — 4 Total assets 20 — — 20 52 10 — 62 40 — — 40 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (11 ) — (11 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (258 ) (258 ) — — — — — — — — Total liabilities — (8 ) (258 ) (266 ) — (11 ) — (11 ) — (4 ) — (4 ) Total net assets (liabilities) $ 20 $ (8 ) $ (258 ) $ (246 ) $ 52 $ (1 ) $ — $ 51 $ 40 $ (4 ) $ — $ 36 ComEd PECO BGE As of December 31, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 29 $ — $ — $ 29 $ 271 $ — $ — $ 271 $ 25 $ — $ — $ 25 Rabbi trust investments Mutual funds — — — — 8 — — 8 4 — — 4 Life insurance contracts — — — — — 12 — 12 — — — — Rabbi trust investments subtotal — — — — 8 12 — 20 4 — — 4 Total assets 29 — — 29 279 12 — 291 29 — — 29 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (12 ) — (12 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (247 ) (247 ) — — — — — — — — Total liabilities — (8 ) (247 ) (255 ) — (12 ) — (12 ) — (4 ) — (4 ) Total net assets (liabilities) $ 29 $ (8 ) $ (247 ) $ (226 ) $ 279 $ — $ — $ 279 $ 29 $ (4 ) $ — $ 25 _________________________ (a) ComEd excludes cash of $36 million and $38 million at December 31, 2016 and 2015 and restricted cash of $2 million and $2 million at December 31, 2016 and 2015 . PECO excludes cash of $22 million and $27 million at December 31, 2016 and 2015 . BGE excludes cash of $13 million and $6 million at December 31, 2016 and 2015 and restricted cash of less than $1 million and $2 million at December 31, 2016 and 2015 and includes long term restricted cash of $2 million at December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) The Level 3 balance consists of the current and noncurrent liability of $19 million and $239 million , respectively, at December 31, 2016 , and $23 million and $224 million , respectively, at December 31, 2015 , related to floating-to-fixed energy swap contracts with unaffiliated suppliers. PHI, Pepco, DPL and ACE The following tables present assets and liabilities measured and recorded at fair value on PHI's, Pepco's, DPL's and ACE's Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and December 31, 2015 : Successor Predecessor As of December 31, 2016 As of December 31, 2015 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 217 $ — $ — $ 217 $ 42 $ — $ — $ 42 Mark-to-market derivative assets (b)(c) 2 — — 2 — — 18 18 Effect of netting and allocation of collateral (2 ) — — (2 ) — — — — Mark-to-market derivative assets subtotal — — — — — — 18 18 Rabbi trust investments Cash equivalents 73 — — 73 12 — — 12 Fixed income — 16 — 16 — 15 — 15 Life insurance contracts — 22 20 42 — 27 19 46 Rabbi trust investments subtotal 73 38 20 131 12 42 19 73 Total assets 290 38 20 348 54 42 37 133 Liabilities Deferred compensation obligation — (28 ) — (28 ) — (30 ) — (30 ) Mark-to-market derivative liabilities (b) — — — — (2 ) — — (2 ) Effect of netting and allocation of collateral — — — — 2 — — 2 Mark-to-market derivative liabilities subtotal — — — — — — — — Total liabilities — (28 ) — (28 ) — (30 ) — (30 ) Total net assets $ 290 $ 10 $ 20 $ 320 $ 54 $ 12 $ 37 $ 103 Pepco DPL ACE As of December 31, 2016 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 33 $ — $ — $ 33 $ 42 $ — $ — $ 42 $ 130 $ — $ — $ 130 Mark-to-market derivative assets (b) — — — — 2 — — 2 — — — — Effect of netting and allocation of collateral — — — — (2 ) — — (2 ) — — — — Mark-to-market derivative assets subtotal — — — — — — — — — — — — Rabbi trust investments Cash equivalents 43 — — 43 — — — — — — — — Fixed income — 16 — 16 — — — — — — — — Life insurance contracts — 22 19 41 — — — — — — — — Rabbi trust investments subtotal 43 38 19 100 — — — — — — — — Total assets 76 38 19 133 42 — — 42 130 — — 130 Liabilities Deferred compensation obligation — (5 ) — (5 ) — (1 ) — (1 ) — — — — Total liabilities — (5 ) — (5 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 76 $ 33 $ 19 $ 128 $ 42 $ (1 ) $ — $ 41 $ 130 $ — $ — $ 130 Pepco DPL ACE As of December 31, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 2 $ — $ — $ 2 $ — $ — $ — $ — $ 30 $ — $ — $ 30 Rabbi trust investments Cash equivalents 11 — — 11 — — — — — — — — Fixed income — 15 — 15 — — — — — — — — Life insurance contracts — 23 19 42 — — — — — — — — Rabbi trust investments subtotal 11 38 19 68 — — — — — — — — Total assets 13 38 19 70 — — — — 30 — — 30 Liabilities Deferred compensation obligation — (6 ) — (6 ) — (1 ) — (1 ) — — — — Mark-to-market derivative liabilities (b) — — — — (2 ) — — (2 ) — — — — Effect of netting and allocation of collateral — — — — 2 — — 2 — — — — Mark-to-market derivative liabilities subtotal — — — — — — — — — — — — Total liabilities — (6 ) — (6 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 13 $ 32 $ 19 $ 64 $ — $ (1 ) $ — $ (1 ) $ 30 $ — $ — $ 30 _______ (a) PHI excludes cash of $19 million and $16 million at December 31, 2016 and 2015 and includes long term restricted cash of $23 million and $18 million at December 31, 2016 and 2015 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $9 million and $5 million at December 31, 2016 and 2015 . DPL excludes cash of $4 million and $5 million at December 31, 2016 and 2015 . ACE excludes cash of $3 million and $3 million at December 31, 2016 and 2015 and includes long term restricted cash of $23 million and $18 million at December 31, 2016 and 2015 which is reported in other deferred debits on the balance sheet. (b) Represents natural gas futures purchased by DPL as part of a natural gas hedging program approved by the DPSC. (c) Prior to the PHI Merger, PHI recorded derivative assets for the embedded call and redemption features on the shares of Preferred Stock outstanding as of December 31, 2015. See Note 19 - Mezzanine Equity for additional information. As a result of the PHI Merger, the PHI preferred stock derivative was reduced to zero as of March 23, 2016 . The following tables present the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis during the year ended December 31, 2016 and 2015 : Successor Generation ComEd PHI (c) Exelon For the year ended December 31, 2016 NDT Fund Investments Pledged Assets Mark-to-Market Other Total Generation Mark-to-Market Derivatives (a) Life Insurance Contracts Eliminated in Consolidation Total Balance as of January 1, 2016 $ 670 $ 22 $ 1,051 $ 33 $ 1,776 $ (247 ) $ — $ — $ 1,529 Included due to merger — — — — — — 20 — 20 Total realized / unrealized gains (losses) Included in net income 7 — (568 ) (b) 1 (560 ) — 3 — (557 ) Included in noncurrent payables to affiliates 16 — — — 16 — — (16 ) — Included in regulatory assets/liabilities — — — — — (11 ) — 16 5 Change in collateral — — (141 ) — (141 ) — — — (141 ) Purchases, sales, issuances and settlements — Purchases 143 2 342 (d) 7 494 — — — 494 Sales (1 ) (5 ) (9 ) — (15 ) — — — (15 ) Issuances — — — — — — (3 ) — (3 ) Settlements (144 ) — — — (144 ) — — — (144 ) Transfers into Level 3 — — 1 1 2 — — — 2 Transfers out of Level 3 (14 ) — (183 ) — (197 ) — — — (197 ) Balance as of December 31, 2016 $ 677 $ 19 $ 493 $ 42 $ 1,231 $ (258 ) $ 20 $ — $ 993 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of December 31, 2016 $ 5 $ — $ 109 $ — $ 114 $ — $ 2 $ — $ 116 Generation ComEd Exelon For the year ended December 31, 2015 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives (d) Other Investments Total Generation Mark-to-Market Derivatives (a) Eliminated in Consolidation Total Balance as of January 1, 2015 $ 605 $ 50 $ 1,050 $ 3 $ 1,708 $ (207 ) $ — $ 1,501 Total realized / unrealized gains (losses) Included in net income 4 — 22 (b) 1 27 — — 27 Included in noncurrent payables to affiliates 18 — — — 18 — (18 ) — Included in payable for Zion Station decommissioning — (2 ) — — (2 ) — — (2 ) Included in regulatory assets/liabilities — — — — — (40 ) 18 (22 ) Change in collateral — — 29 — 29 — — 29 Purchases, sales, issuances and settlements Purchases 146 2 144 30 322 — — 322 Sales (8 ) (28 ) (25 ) — (61 ) — — (61 ) Settlements (95 ) — — — (95 ) — — (95 ) Transfers into Level 3 4 — 80 — 84 — — 84 Transfers out of Level 3 (4 ) — (249 ) (1 ) (254 ) — — (254 ) Balance as of December 31, 2015 $ 670 $ 22 $ 1,051 $ 33 $ 1,776 $ (247 ) $ — $ 1,529 The amount of total gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held as of December 31, 2015 $ 2 $ — $ 856 $ — $ 858 $ — $ — $ 858 _________________________ (a) Includes $29 million of decreases in fair value and an increase for realized losses due to settlements of $18 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the year ended December 31, 2016 . Includes $55 million of decreases in fair value and a reduction for realized losses due to settlements of $(15) million for the year ended December 31, 2015 . (b) Includes a reduction for the reclassification of $677 million and $834 million of realized gains due to the settlement of derivative contracts for the years ended December 31, 2016 and 2015 , respectively. (c) Successor period represents activity from March 24, 2016 to December 31, 2016 . See tables below for PHI's predecessor periods, as well as activity

Derivative Financial Instrument

Derivative Financial Instruments (All Registrants)	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments (All Registrants)	13 . Derivative Financial Instruments (All Registrants) The Registrants use derivative instruments to manage commodity price risk, foreign currency exchange risk and interest rate risk related to ongoing business operations. Commodity Price Risk (All Registrants) To the extent the amount of energy Generation produces differs from the amount of energy it has contracted to sell, Exelon and Generation are exposed to market fluctuations in the prices of electricity, fossil fuels and other commodities. Each of the Registrants employ established policies and procedures to manage their risks associated with market fluctuations in commodity prices by entering into physical and financial derivative contracts, including swaps, futures, forwards, options and short-term and long-term commitments to purchase and sell energy and energy-related products. The Registrants believe these instruments, which are classified as either economic hedges or non-derivatives, mitigate exposure to fluctuations in commodity prices. Derivative accounting guidance requires that derivative instruments be recognized as either assets or liabilities at fair value, with changes in fair value of the derivative recognized in earnings each period. Other accounting treatments are available through special election and designation, provided they meet specific, restrictive criteria both at the time of designation and on an ongoing basis. These alternative permissible accounting treatments include normal purchase normal sale (NPNS), cash flow hedge and fair value hedge. For Generation, all derivative economic hedges related to commodities are recorded at fair value through earnings for the combined company, referred to as economic hedges in the following tables. The Registrants have applied the NPNS scope exception to certain derivative contracts for the forward sale of generation, power procurement agreements, and natural gas supply agreements. Generation has also entered into bilateral long-term contractual obligations for sales of energy to load-serving entities, including electric utilities, municipalities, electric cooperatives and retail load aggregators, as well as contractual obligations to deliver energy to market participants who primarily focus on the resale of energy products for delivery. These non-derivative contracts are accounted for primarily under the accrual method of accounting. Additionally, Generation is exposed to certain market risks through its proprietary trading activities. The proprietary trading activities are a complement to Generation’s energy marketing portfolio but represent a small portion of Generation’s overall energy marketing activities. Economic Hedging. The Registrants are exposed to commodity price risk primarily relating to changes in the market price of electricity, fossil fuels, and other commodities associated with price movements resulting from changes in supply and demand, fuel costs, market liquidity, weather conditions, governmental regulatory and environmental policies, and other factors. Within Exelon, Generation has the most exposure to commodity price risk. As such, Generation uses a variety of derivative and non-derivative instruments to manage the commodity price risk of its electric generation facilities, including power and gas sales, fuel and energy purchases, natural gas transportation and pipeline capacity agreements and other energy-related products marketed and purchased. In order to manage these risks, Generation may enter into fixed-price derivative or non-derivative contracts to hedge the variability in future cash flows from forecasted sales of energy and gas and purchases of fuel and energy. The objectives for entering into such hedges include fixing the price for a portion of anticipated future electricity sales at a level that provides an acceptable return on electric generation operations, fixing the price of a portion of anticipated fuel purchases for the operation of power plants, and fixing the price for a portion of anticipated energy purchases to supply load-serving customers. The portion of forecasted transactions hedged may vary based upon management’s policies and hedging objectives, the market, weather conditions, operational and other factors. Generation is also exposed to differences between the locational settlement prices of certain economic hedges and the hedged generating units. This price difference is actively managed through other instruments which include derivative congestion products, whose changes in fair value are recognized in earnings each period, and auction revenue rights, which are accounted for on an accrual basis. In general, increases and decreases in forward market prices have a positive and negative impact, respectively, on Generation’s owned and contracted generation positions that have not been hedged. Generation hedges commodity price risk on a ratable basis over three-year periods. As of December 31, 2016 , the proportion of expected generation hedged for the major reportable segments was 91% - 94% , 56% - 59% and 28% - 31% for 2017 , 2018 , and 2019 , respectively. The percentage of expected generation hedged is the amount of equivalent sales divided by the expected generation. Expected generation is the volume of energy that best represents our commodity position in energy markets from owned or contracted generating facilities based upon a simulated dispatch model that makes assumptions regarding future market conditions, which are calibrated to market quotes for power, fuel, load following products, and options. Equivalent sales represent all hedging products, which include economic hedges and certain non-derivative contracts, including Generation’s sales to ComEd, PECO and BGE to serve their retail load. On December 17, 2010, ComEd entered into several 20 -year floating-to-fixed energy swap contracts with unaffiliated suppliers for the procurement of long-term renewable energy and associated RECs. Delivery under the contracts began in June 2012. These contracts are designed to lock in a portion of the long-term commodity price risk resulting from the renewable energy resource procurement requirements in the Illinois Settlement Legislation. ComEd has not elected hedge accounting for these derivative financial instruments. ComEd records the fair value of the swap contracts on its balance sheet. Because ComEd receives full cost recovery for energy procurement and related costs from retail customers, the change in fair value each period is recorded by ComEd as a regulatory asset or liability. See Note 3 — Regulatory Matters for additional information. PECO has contracts to procure electric supply that were executed through the competitive procurement process outlined in its PAPUC-approved DSP Programs, which are further discussed in Note 3 — Regulatory Matters . Based on Pennsylvania legislation and the DSP Programs permitting PECO to recover its electric supply procurement costs from retail customers with no mark-up, PECO’s price risk related to electric supply procurement is limited. PECO locked in fixed prices for a significant portion of its commodity price risk through full requirements contracts. PECO has certain full requirements contracts that are considered derivatives and qualify for the NPNS scope exception under current derivative authoritative guidance. PECO’s natural gas procurement policy is designed to achieve a reasonable balance of long-term and short-term gas purchases under different pricing approaches in order to achieve system supply reliability at the least cost. PECO’s reliability strategy is two-fold. First, PECO must assure that there is sufficient transportation capacity to satisfy delivery requirements. Second, PECO must ensure that a firm source of supply exists to utilize the capacity resources. All of PECO’s natural gas supply and asset management agreements that are derivatives either qualify for the NPNS scope exception and have been designated as such, or have no mark-to-market balances because the derivatives are index priced. Additionally, in accordance with the 2016 PAPUC PGC settlement and to reduce the exposure of PECO and its customers to natural gas price volatility, PECO has continued its program to purchase natural gas for both winter and summer supplies using a layered approach of locking-in prices ahead of each season with long-term gas purchase agreements (those with primary terms of at least twelve months). Under the terms of the 2016 PGC settlement, PECO is required to lock in (i.e., economically hedge) the price of a minimum volume of its long-term gas commodity purchases. PECO’s gas-hedging program is designed to cover about 25% of planned natural gas purchases in support of projected firm sales. The hedging program for natural gas procurement has no direct impact on PECO’s financial position or results of operations as natural gas costs are fully recovered from customers under the PGC. BGE has contracts to procure SOS electric supply that are executed through a competitive procurement process approved by the MDPSC. The SOS rates charged recover BGE’s wholesale power supply costs and include an administrative fee. The administrative fee includes an incremental cost component and a shareholder return component for commercial and industrial rate classes. BGE’s price risk related to electric supply procurement is limited. BGE locks in fixed prices for all of its SOS requirements through full requirements contracts. Certain of BGE’s full requirements contracts, which are considered derivatives, qualify for the NPNS scope exception under current derivative authoritative guidance. Other BGE full requirements contracts are not derivatives. BGE provides natural gas to its customers under a MBR mechanism approved by the MDPSC. Under this mechanism, BGE’s actual cost of gas is compared to a market index (a measure of the market price of gas in a given period). The difference between BGE’s actual cost and the market index is shared equally between shareholders and customers. BGE must also secure fixed price contracts for at least 10% , but not more than 20% , of forecasted system supply requirements for flowing (i.e. non-storage) gas for the November through March period. These fixed-price contracts are not subject to sharing under the MBR mechanism. BGE also ensures it has sufficient pipeline transportation capacity to meet customer requirements. All of BGE’s natural gas supply and asset management agreements qualify for the NPNS scope exception and result in physical delivery. Pepco has contracts to procure SOS electric supply that are executed through a competitive procurement process approved by the MDPSC and DCPSC. The SOS rates charged recover Pepco's wholesale power supply costs and include an administrative fee. The administrative fee includes an incremental cost component and a shareholder return component for residential and commercial rate classes. Pepco’s price risk related to electric supply procurement is limited. Pepco locks in fixed prices for all of its SOS requirements through full requirements contracts. Certain of Pepco’s full requirements contracts, which are considered derivatives, qualify for the NPNS scope exception under current derivative authoritative guidance. Other Pepco full requirements contracts are not derivatives. DPL has contracts to procure SOS electric supply that are executed through a competitive procurement process approved by the MDPSC and the DPSC. The SOS rates charged recover DPL's wholesale power supply costs. In Delaware, DPL is also entitled to recover a Reasonable Allowance for Retail Margin (RARM). The RARM includes a fixed annual margin of approximately $2.75 million , plus an incremental cost component and a cash working capital allowance. In Maryland, DPL charges an administrative fee intended to allow it to recover its administrative costs. DPL locks in fixed prices for all of its SOS requirements through full requirements contracts. DPL’s price risk related to electric supply procurement is limited. Certain of DPL’s full requirements contracts, which are considered derivatives, qualify for the NPNS scope exception under current derivative authoritative guidance. Other DPL full requirements contracts are not derivatives. DPL provides natural gas to its customers under an Annual GCR mechanism approved by the DPSC. Under this mechanism, DPL’s Annual GCR Filing establishes a future GCR for firm bundled sales customers by using a forecast of demand and commodity costs. The actual costs are trued up versus the forecast on a monthly basis and any shortfall or excess is carried forward as a recovery balance in the next GCR filing. The demand portion of the GCR is based upon DPL’s firm transportation and storage contracts. DPL has firm deliverability of swing and seasonal storage; a liquefied natural gas facility and firm transportation capacity to meet customer demand and provide a reserve margin. The commodity portion of the GCR includes a commission approved hedging program which is intended to reduce gas commodity price volatility while limiting the firm natural gas customers’ exposure to adverse changes in the market price of natural gas. The hedge program requires that DPL hedge, on a non-discretionary basis, an amount equal to fifty percent (50%) of estimated purchase requirements for each month, including estimated monthly purchases for storage injections. The fifty percent (50%) hedge monthly target is achieved by hedging 1/12th of the 50% target each month beginning 12-months prior to the month in which the physical gas is to be purchased. Currently, DPL uses only exchange traded futures for its Gas Hedging Program, which are considered derivatives, however, it retains the capability to employ other physical and financial hedges if needed. DPL has not elected hedge accounting for these derivative financial instruments. Because of the DPSC-approved fuel adjustment clause for DPL's derivatives, the change in fair value of the derivatives each period, in addition to all premiums paid and other transaction costs incurred as part of the Gas Hedging Program, are fully recoverable and are recorded by DPL as regulatory assets or liabilities. DPL’s physical gas purchases are currently all daily, monthly or intra-month transactions. From time to time, DPL will enter into seasonal purchase or sale arrangements, however, there are none currently in the portfolio. Certain of DPL's full requirements contracts, which are considered derivatives, qualify for the NPNS scope exception under current derivative authoritative guidance. Other DPL full requirements contracts are not derivatives. ACE has contracts to procure BGS electric supply that are executed through a competitive procurement process approved by the NJBPU. The BGS rates charged recover ACE's wholesale power supply costs. ACE does not make any profit or incur any loss on the supply component of the BGS it supplies to customers. ACE’s price risk related to electric supply procurement is limited. ACE locks in fixed prices for all of its BGS requirements through full requirements contracts. Certain of ACE’s full requirements contracts, which are considered derivatives, qualify for the NPNS scope exception under current derivative authoritative guidance. Other ACE full requirements contracts are not derivatives. Proprietary Trading. Generation also enters into certain energy-related derivatives for proprietary trading purposes. Proprietary trading includes all contracts entered into with the intent of benefiting from shifts or changes in market prices as opposed to those entered into with the intent of hedging or managing risk. Proprietary trading activities are subject to limits established by Exelon’s RMC. The proprietary trading activities, which included settled physical sales volumes of 6,179 GWh, 7,310 GWh and 10,571 GWh for the years ended December 31, 2016 , 2015 and 2014 , are a complement to Generation’s energy marketing portfolio but represent a small portion of Generation’s revenue from energy marketing activities. ComEd, PECO, BGE, PHI, Pepco, DPL and ACE do not enter into derivatives for proprietary trading purposes. Interest Rate and Foreign Exchange Risk (Exelon, Generation, ComEd, PECO, BGE and PHI) The Registrants use a combination of fixed-rate and variable-rate debt to manage interest rate exposure. The Registrants utilize fixed-to-floating interest rate swaps, which are typically designated as fair value hedges, as a means to manage their interest rate exposure. In addition, the Registrants may utilize interest rate derivatives to lock in rate levels in anticipation of future financings, which are typically designated as cash flow hedges. These strategies are employed to manage interest rate risks. At December 31, 2016 , Exelon had $800 million of notional amounts of fixed-to-floating hedges outstanding and Exelon and Generation had $659 million of notional amounts of floating-to-fixed hedges outstanding. Assuming the fair value and cash flow interest rate hedges are 100% effective, a hypothetical 50 bps increase in the interest rates associated with unhedged variable-rate debt (excluding Commercial Paper) and fixed-to-floating swaps would result in an approximately $7 million decrease in Exelon Consolidated pre-tax income for the year ended December 31, 2016 . To manage foreign exchange rate exposure associated with international commodity purchases in currencies other than U.S. dollars, Generation utilizes foreign currency derivatives, which are typically designated as economic hedges. Below is a summary of the interest rate and foreign exchange hedge balances as of December 31, 2016 : Generation Exelon Corporate Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary (a) Collateral and Netting (b) Subtotal Derivatives Total Mark-to-market derivative assets (current assets) $ — $ 17 $ 4 $ (13 ) $ 8 $ — $ 8 Mark-to-market derivative assets (noncurrent assets) — 11 1 (8 ) 4 16 20 Total mark-to-market derivative assets — 28 5 (21 ) 12 16 28 Mark-to-market derivative liabilities (current liabilities) (7 ) (13 ) (2 ) 14 (8 ) — (8 ) Mark-to-market derivative liabilities (noncurrent liabilities) (3 ) (8 ) (2 ) 9 (4 ) — (4 ) Total mark-to-market derivative liabilities (10 ) (21 ) (4 ) 23 (12 ) — (12 ) Total mark-to-market derivative net assets (liabilities) $ (10 ) $ 7 $ 1 $ 2 $ — $ 16 $ 16 _________________________ (a) Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts between the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates. (b) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures subject to a master netting or similar agreement, such as accrued interest, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. The following table provides a summary of the interest rate and foreign exchange hedge balances recorded by the Registrants as of December 31, 2015 : Generation Other Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary (a) Collateral and Netting (b) Subtotal Derivatives Subtotal Total Mark-to-market derivative assets (current assets) $ — $ 10 $ 10 $ (5 ) $ 15 $ — $ — $ 15 Mark-to-market derivative assets (noncurrent assets) — 10 5 (1 ) 14 25 $ 25 $ 39 Total mark-to-market derivative assets — 20 15 (6 ) 29 25 25 54 Mark-to-market derivative liabilities (current liabilities) (8 ) (2 ) (9 ) 11 (8 ) — — (8 ) Mark-to-market derivative liabilities (noncurrent liabilities) (8 ) (1 ) (3 ) 4 (8 ) — — (8 ) Total mark-to-market derivative liabilities (16 ) (3 ) (12 ) 15 (16 ) — — (16 ) Total mark-to-market derivative net assets (liabilities) $ (16 ) $ 17 $ 3 $ 9 $ 13 $ 25 $ 25 $ 38 _________________________ (a) Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts between the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates. (b) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures subject to a master netting or similar agreement, such as accrued interest, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. Fair Value Hedges . For derivative instruments that are designated and qualify as fair value hedges, the gain or loss on the derivative as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in current earnings. Exelon includes the gain or loss on the hedged items and the offsetting loss or gain on the related interest rate swaps in interest expense as follows: Year Ended December 31, Income Statement Location 2016 2015 2014 2016 2015 2014 Gain (Loss) on Swaps Gain (Loss) on Borrowings Generation Interest expense (a) $ — $ (1 ) $ (16 ) $ — $ — $ 2 Exelon Interest expense $ (9 ) $ 3 $ 14 $ 23 $ 14 $ (1 ) ______________________ (a) For the years ended December 31, 2015 and 2014 , the loss on Generation swaps included $(1) million and $(17) million realized in earnings, respectively, with an immaterial amount and $4 million excluded from hedge effectiveness testing, respectively. At December 31, 2016 , Exelon had total outstanding fixed-to-floating fair value hedges related to interest rate swaps of $800 million , with a derivative asset of $16 million . At December 31, 2015 , Exelon had outstanding fixed-to-floating fair value hedges related to interest rate swaps of $800 million , with a derivative asset of $25 million . During the years ended December 31, 2016 and 2015 , the impact on the results of operations as a result of ineffectiveness from fair value hedges was a $14 million gain and $17 million gain, respectively. Cash Flow Hedges . During the second quarter of 2016, Exelon entered into $90 million of floating-to-fixed forward starting interest rate swaps to manage a portion of the interest rate exposure associated with an anticipated debt issuance. The swaps were designated as cash flow hedges. Exelon terminated the swaps during the third quarter of 2016 upon issuance of the debt. Exelon did not recognize a gain or loss as a result of the termination. During the first and second quarter of 2016, Exelon entered into $600 million and $100 million of floating-to-fixed forward starting interest rate swaps, respectively, to manage a portion of the interest rate exposure associated with an anticipated debt issuance. The swaps were designated as cash flow hedges. Exelon terminated the swaps during the second quarter of 2016 upon issuance of the debt. Exelon recognized a loss of $3 million related to the swaps and $3 million of AOCI will be amortized into Other, net in Exelon's Consolidated Statement of Operations and Comprehensive Income over the term of the debt. See Note 14 — Debt and Credit Agreements of the Combined Notes to Consolidated Financial Statements for additional information. During the first quarter of 2016, Exelon entered into a $100 million floating-to-fixed forward starting interest rate swaps to manage a portion of the interest rate exposure associated with an anticipated debt issuance. The swap was designated as a cash flow hedge. Exelon terminated the swap during the first quarter of 2016 upon issuance of the debt. Exelon did not recognize a gain or loss as a result of the termination of the swap and an immaterial amount of AOCI will be amortized into Other, net in Exelon's Consolidated Statement of Operations and Comprehensive Income over the term of the debt. During the third quarter of 2014, EGTP, a subsidiary of Generation, entered into a floating-to-fixed interest rate swap to manage a portion of its interest rate exposure in connection with the long-term borrowing. See Note 14 — Debt and Credit Agreements for additional information regarding the financing. The swaps have a notional amount of $495 million as of December 31, 2016 and expire in 2019. The swap was designated as a cash flow hedge in the fourth quarter of 2014. At December 31, 2016 , the subsidiary had a $9 million derivative liability related to the swap. During the first quarter of 2014, EGR, a subsidiary of Generation, entered into floating-to-fixed interest rate swaps to manage a portion of its interest rate exposure in connection with the long-term borrowings. See Note 14 — Debt and Credit Agreements for additional information regarding the financing. The swaps have a notional amount of $164 million as of December 31, 2016 and expire in 2020. The swaps are designated as cash flow hedges. At December 31, 2016 , the subsidiary had a $1 million derivative liability related to the swaps. During the second quarter of 2002, PHI entered into treasury rate lock transactions in anticipation of the issuance of several series of fixed-rate debt commencing in August 2002 to manage a portion of its interest rate exposure. Upon issuance of the fixed-rate debt in August 2002, the treasury rate locks were terminated at a loss and the loss was deferred in AOCI. As a result of the PHI Merger, the remaining unamortized deferred loss recorded in AOCI was adjusted to zero through application of purchase accounting. During the years ended December 31, 2016 and 2015 , the impact on the results of operations as a result of ineffectiveness from cash flow hedges in continuing designated hedge relationships was immaterial. Economic Hedges. During the third quarter of 2011, Sacramento PV Energy, a subsidiary of Generation, entered into floating-to-fixed interest rate swaps to manage a portion of its interest rate exposure in connection with the long-term borrowings. See Note 14 — Debt and Credit Agreements for additional information regarding the financing. During the first quarter of 2016, upon the termination of debt, Generation terminated the swaps. The total notional amount of the swaps were $25 million . No gain or loss was recognized as a result of the termination of the swaps. During the third quarter of 2012, Constellation Solar Horizons, a subsidiary of Generation, entered into a floating-to-fixed interest rate swap to manage a portion of its interest rate exposure in connection with the long-term borrowings. See Note 14 — Debt and Credit Agreements for additional information regarding the financing. During the first quarter of 2016, upon the termination of debt, Generation terminated the swap. The total notional amount of the swap was $24 million . No gain or loss was recognized as a result of the termination of the swap. During the second quarter 2015, upon the issuance of debt, Exelon terminated $2,400 million of floating-to-fixed forward starting interest rate swaps. As a result of the termination of the swaps, Exelon realized a $64 million loss during the second quarter of 2015. At December 31, 2016 , Generation had no notional amounts of interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions and $85 million in notional amounts of foreign currency exchange rate swaps that are marked-to-market to manage the exposure associated with international purchases of commodities in currencies other than U.S. dollars. Fair Value Measurement and Accounting for the Offsetting of Amounts Related to Certain Contracts (Exelon Generation, ComEd, PECO, BGE, PHI and DPL) Fair value accounting guidance and disclosures about offsetting assets and liabilities requires the fair value of derivative instruments to be shown in the Notes to the Consolidated Financial Statements on a gross basis, even when the derivative instruments are subject to legally enforceable master netting agreements and qualify for net presentation in the Consolidated Balance Sheet. A master netting agreement is an agreement between two counterparties that may have derivative and non-derivative contracts with each other providing for the net settlement of all referencing contracts via one payment stream, which takes place as the contracts deliver, when collateral is requested or in the event of default. Generation’s use of cash collateral is generally unrestricted unless Generation is downgraded below investment grade (i.e. to BB+ or Ba1). In the table below, Generation’s energy related economic hedges and proprietary trading derivatives are shown gross. The impact of the netting of fair value balances with the same counterparty that are subject to legally enforceable master netting agreements, as well as netting of cash collateral including initial margin on exchange positions, is aggregated in the collateral and netting column. As of December 31, 2016 and 2015 , $8 million of cash collateral held and $3 million of cash collateral posted, respectively, was not offset against derivative positions because such collateral was not associated with any energy-related derivatives, were associated with accrual positions, or as of the balance sheet date there were no positions to offset. Excluded from the tables below are economic hedges that qualify for the NPNS scope exception and other non-derivative contracts that are accounted for under the accrual method of accounting. ComEd’s use of cash collateral is generally unrestricted unless ComEd is downgraded below investment grade (i.e. to BB+ or Ba1). Cash collateral held by PECO and BGE must be deposited in a non affiliate major U.S. commercial bank or foreign bank with a U.S. branch office that meet certain qualifications. In the table below, DPL's economic hedges are shown gross. The impact of the netting of fair value balances with the same counterparty that are subject to legally enforceable master netting agreements, as well as netting of cash collateral, is aggregated in the collateral and netting column. The following table provides a summary of the derivative fair value balances recorded by the Registrants as of December 31, 2016 : Successor Generation ComEd DPL PHI Exelon Derivatives Economic Hedges Proprietary Trading Collateral and Netting (a) Subtotal (b) Economic Hedges (c) Economic Hedges (d) Collateral and Netting (a) Subtotal Subtotal Total Derivatives Mark-to-market derivative assets (current assets) $ 3,623 $ 55 $ (2,769 ) $ 909 $ — $ 2 $ (2 ) $ — $ — $ 909 Mark-to-market derivative assets (noncurrent assets) 1,467 21 (1,016 ) 472 — — — — — 472 Total mark-to-market derivative assets 5,090 76 (3,785 ) 1,381 — 2 (2 ) — — 1,381 Mark-to-market derivative liabilities (current liabilities) (3,165 ) (54 ) 2,964 (255 ) (19 ) — — — — (274 ) Mark-to-market derivative liabilities (noncurrent liabilities) (1,274 ) (25 ) 1,150 (149 ) (239 ) — — — — (388 ) Total mark-to-market derivative liabilities (4,439 ) (79 ) 4,114 (404 ) (258 ) — — — — (662 ) Total mark-to-market derivative net assets (liabilities) $ 651 $ (3 ) $ 329 $ 977 $ (258 ) $ 2 $ (2 ) $ — $ — $ 719 ______________________ (a) Exelon, Generation, PHI and DPL net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such

Debt and Credit Agreements (All

Debt and Credit Agreements (All Registrants)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Debt and Credit Agreements (All Registrants)	Debt and Credit Agreements (All Registrants) Short-Term Borrowings Exelon, ComEd, and BGE meet their short-term liquidity requirements primarily through the issuance of commercial paper. Generation and PECO meet their short-term liquidity requirements primarily through the issuance of commercial paper and borrowings from the Exelon intercompany money pool. PHI meets its short-term liquidity requirement primarily through the issuance of short-term notes and the Exelon intercompany money pool. Pepco, DPL and ACE meet their short-term liquidity requirements primarily through the issuance of commercial paper and short-term notes. The Registrants may use their respective credit facilities for general corporate purposes, including meeting short-term funding requirements and the issuance of letters of credit. Commercial Paper The following table reflects the Registrants' commercial paper programs supported by the revolving credit agreements and bilateral credit agreements at December 31, 2016 and December 31, 2015 : Maximum Program Size at December 31, Outstanding Commercial Paper at December 31, Average Interest Rate on Commercial Paper Borrowings for the Year Ended December 31, Commercial Paper Issuer 2016 (a)(b) 2015 (a)(b) 2016 2015 2016 2015 Exelon Corporate $ 600 $ 500 $ — $ — 0.70 % n.a. Generation 5,300 5,450 620 — 0.94 % 0.49 % ComEd 1,000 1,000 — 294 0.77 % 0.53 % PECO 600 600 — — n.a n.a. BGE 600 600 45 210 0.77 % 0.48 % PHI Corporate — 875 — 484 1.03 % 0.80 % Pepco 500 500 23 64 0.71 % 0.44 % DPL 500 500 — 105 0.68 % 0.47 % ACE 350 350 — 5 0.65 % 0.46 % Total $ 9,450 $ 10,375 $ 688 $ 1,162 _____________________ (a) Excludes $500 million and $275 million in bilateral credit facilities that do not back Generation's commercial paper program at December 31, 2016 and 2015 , respectively. (b) Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million , $34 million , $34 million , $5 million , $2 million , $2 million and $2 million , respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016 , letters of credit issued under these facilities totaled $7 million , $12 million , $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively. In order to maintain their respective commercial paper programs in the amounts indicated above, each Registrant must have credit facilities in place, at least equal to the amount of its commercial paper program. While the amount of outstanding commercial paper does not reduce available capacity under a Registrant’s credit facility, a Registrant does not issue commercial paper in an aggregate amount exceeding the then available capacity under its credit facility. At December 31, 2016 , the Registrants had the following aggregate bank commitments, credit facility borrowings and available capacity under their respective credit facilities: Available Capacity at December 31, 2016 Borrower Facility Type Aggregate Bank (a)(b) Facility Draws Outstanding Letters of Credit (c) Actual To Support Additional Commercial (d) Exelon Corporate Syndicated Revolver $ 600 $ — $ 29 $ 571 $ 571 Generation Syndicated Revolver 5,300 — 1,170 4,130 3,510 Generation Bilaterals 500 75 306 119 — ComEd Syndicated Revolver 1,000 — 2 998 998 PECO Syndicated Revolver 600 — 2 598 598 BGE Syndicated Revolver 600 — — 600 555 Pepco Syndicated Revolver 300 — — 300 277 DPL Syndicated Revolver 300 — — 300 300 ACE Syndicated Revolver 300 — 1 299 299 Total $ 9,500 $ 75 $ 1,510 $ 7,915 $ 7,108 _______________________ (a) Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million , $34 million , $34 million , $5 million , $2 million , $2 million and $2 million , respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016 , letters of credit issued under these facilities totaled $7 million , $12 million , $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively. (b) Pepco, DPL and ACE's revolving credit facility is subject to available borrowing capacity. The borrowing capacity may be increased or decreased during the term of the facility, except that (i) the sum of the borrowing capacity must equal the total amount of the facility, and (ii) the aggregate amount of credit used at any given time by each of Pepco, DPL or ACE may not exceed $900 million or the maximum amount of short-term debt the company is permitted to have outstanding by its regulatory authorities. The total number of the borrowing reallocations may not exceed eight per year during the term of the facility. (c) Excludes nonrecourse debt letters of credit, see discussion below on Continental Wind. (d) Excludes $500 million in bilateral credit facilities that do not back Generation’s commercial paper program. As of December 31, 2016 , there was $75 million of borrowings under Generation's bilateral credit facilities. The following tables present the short-term borrowings activity for Exelon, Generation, ComEd, BGE, PHI, Pepco, DPL and ACE during 2016 , 2015 and 2014 . PECO did not have any short-term borrowings during 2016 , 2015 or 2014 . Exelon 2016 2015 2014 Average borrowings $ 1,125 $ 499 $ 571 Maximum borrowings outstanding 3,076 739 1,164 Average interest rates, computed on a daily basis 0.88 % 0.53 % 0.32 % Average interest rates, at December 31 1.12 % 0.88 % 0.53 % Generation 2016 2015 2014 Average borrowings $ 536 $ 1 $ 93 Maximum borrowings outstanding 1,735 50 552 Average interest rates, computed on a daily basis 0.94 % 0.49 % 0.32 % Average interest rates, at December 31 1.14 % n.a. n.a. ComEd 2016 2015 2014 Average borrowings $ 256 $ 461 $ 415 Maximum borrowings outstanding 755 684 597 Average interest rates, computed on a daily basis 0.77 % 0.53 % 0.33 % Average interest rates, at December 31 n.a. 0.89 % 0.50 % BGE 2016 2015 2014 Average borrowings $ 143 $ 37 $ 64 Maximum borrowings outstanding 369 210 180 Average interest rates, computed on a daily basis 0.77 % 0.48 % 0.29 % Average interest rates, computed at December 31 0.95 % 0.87 % 0.61 % PHI Successor Predecessor 2016 2015 2014 Average borrowings $ 153 $ 444 $ 153 Maximum borrowings outstanding 559 784 369 Average interest rates, computed on a daily basis 1.03 % 0.90 % 0.56 % Average interest rates, computed at December 31 n.a. 1.22 % 0.78 % Pepco 2016 2015 2014 Average borrowings $ 4 $ 34 $ 37 Maximum borrowings outstanding 73 190 209 Average interest rates, computed on a daily basis 0.71 % 0.44 % 0.28 % Average interest rates, computed at December 31 0.90 % 0.68 % 0.46 % DPL 2016 2015 2014 Average borrowings $ 33 $ 81 $ 69 Maximum borrowings outstanding 116 179 177 Average interest rates, computed on a daily basis 0.68 % 0.47 % 0.26 % Average interest rates, computed at December 31 n.a. 0.79 % 0.42 % ACE 2016 2015 2014 Average borrowings $ — $ 175 $ 112 Maximum borrowings outstanding 5 253 259 Average interest rates, computed on a daily basis 0.65 % 0.46 % 0.27 % Average interest rates, computed at December 31 n.a. 0.65 % 0.52 % Short-Term Loan Agreements On July 30, 2015, PHI entered into a $300 million term loan agreement. The net proceeds of the loan were used to repay PHI's outstanding commercial paper and for general corporate purposes. Pursuant to the loan agreement, loans made thereunder bear interest at a variable rate equal to LIBOR plus 0.95% , and all indebtedness thereunder is unsecured. On April 4, 2016, PHI repaid $300 million of its term loan in full. On January 13, 2016, PHI entered into a $500 million term loan agreement, which was amended on March 28, 2016. The net proceeds of the loan were used to repay PHI's outstanding commercial paper, and for general corporate purposes. Pursuant to the loan agreement, as amended, loans made thereunder bear interest at a variable rate equal to LIBOR plus 1% , and all indebtedness thereunder is unsecured, and the aggregate principal amount of all loans, together with any accrued but unpaid interest due under the Loan Agreement, must be repaid in full on or before March 27, 2017. The loan agreement is reflected in Exelon's and PHI's Consolidated Balance Sheets within Short-term borrowings. On February 22, 2016, Generation and EDF entered into separate member revolving promissory notes with CENG to finance short-term working capital needs. The notes are scheduled to mature on January 31, 2017 and bear interest at a variable rate equal to LIBOR plus 1.75% . On July 25, 2016, CENG paid off the outstanding balances under each note. Credit Agreements On January 5, 2016, Generation entered into a credit agreement establishing a $150 million bilateral credit facility, scheduled to mature in January of 2019. This facility will solely be utilized by Generation to issue lines of credit. This facility does not back Generation's commercial paper program. On April 1, 2016, the credit agreement for CENG's $100 million bilateral credit facility was amended to increase the overall facility size to $200 million . This facility is utilized by CENG to fund working capital and capital projects. The facility does not back Generation's commercial paper program. On May 26, 2016, Exelon Corporate, Generation, ComEd, PECO and BGE entered into amendments to each of their respective syndicated revolving credit facilities, which extended the maturity of each of the facilities to May 26, 2021. Exelon Corporate also increased the size of its facility from $500 million to $600 million . On May 26, 2016, PHI, Pepco, DPL and ACE entered into an amendment to their Second Amended and Restated Credit Agreement dated as of August 1, 2011, which (i) extended the maturity date of the facility to May 26, 2021, (ii) removed PHI as a borrower under the facility, (iii) decreased the size of the facility from $1.5 billion to $900 million and (iv) aligned its financial covenant from debt to capitalization leverage ratio to interest coverage ratio. Borrowings under Exelon Corporate’s, Generation’s, ComEd’s, PECO’s, BGE's, Pepco's, DPL's, and ACE's revolving credit agreements bear interest at a rate based upon either the prime rate or a LIBOR-based rate, plus an adder based upon the particular Registrant’s credit rating. The adders for the prime based borrowings and LIBOR-based borrowings are presented in the following table: Exelon Generation ComEd PECO BGE Pepco DPL ACE Prime based borrowings 27.5 27.5 7.5 0.0 0.0 7.5 7.5 7.5 LIBOR-based borrowings 127.5 127.5 107.5 90.0 100.0 107.5 107.5 107.5 The maximum adders for prime rate borrowings and LIBOR-based rate borrowings are 90 basis points and 165 basis points, respectively. The credit agreements also require the borrower to pay a facility fee based upon the aggregate commitments. The fee varies depending upon the respective credit ratings of the borrower. An event of default under any of the Registrants' credit agreements would not constitute an event of default under any of the other Registrants' credit agreements, except that a bankruptcy or other event of default in the payment of principal, premium or indebtedness in principal amount in excess of $100 million in the aggregate by Generation under its credit agreement would constitute an event of default under the Exelon Corporation credit agreement. Each credit agreement requires the affected borrower to maintain a minimum cash from operations to interest expense ratio for the twelve-month period ended on the last day of any quarter. The ratios exclude revenues and interest expenses attributable to securitization debt, certain changes in working capital, distributions on preferred securities of subsidiaries and, in the case of Exelon and Generation, interest on the debt of its project subsidiaries. The following table summarizes the minimum thresholds reflected in the credit agreements for the year ended December 31, 2016 : Exelon Generation ComEd PECO BGE Pepco DPL ACE Credit agreement threshold 2.50 to 1 3.00 to 1 2.00 to 1 2.00 to 1 2.00 to 1 2.00 to 1 2.00 to 1 2.00 to 1 At December 31, 2016 , the interest coverage ratios at the Registrants were as follows: Exelon Generation ComEd PECO BGE Pepco DPL ACE Interest coverage ratio 7.03 11.81 6.89 8.77 10.47 6.24 8.42 5.84 Through May 26, 2016, when Pepco, DPL and ACE entered into a new restated credit agreement, as mentioned above, PHI, Pepco, DPL and ACE had maintained an unsecured syndicated credit facility to provide for their respective liquidity needs, including obtaining letters of credit, borrowing for general corporate purposes and supporting their commercial paper programs. The termination date of this credit facility was August 1, 2018. The aggregate borrowing limit under the amended and restated credit facility was $1.5 billion , all or any portion of which could have been used to obtain loans and up to $500 million of which could have been used to obtain letters of credit. The facility also included a swingline loan sub-facility, pursuant to which each company could have made same day borrowings in an aggregate amount not to exceed 10% of the total amount of the facility. Any swingline loan had to be repaid by the borrower within fourteen days of receipt. The credit sublimit was $750 million for PHI and $250 million for each of Pepco, DPL and ACE. The sublimits could have been increased or decreased by the individual borrower during the term of the facility, except that (i) the sum of all of the borrower sublimits following any such increase or decrease had to equal the total amount of the facility and (ii) the aggregate amount of credit used at any given time by (a) PHI could not exceed $1.25 billion and (b) each of Pepco, DPL or ACE could not exceed the lesser of $500 million and the maximum amount of short-term debt the company was permitted to have outstanding by its regulatory authorities. The total number of the sublimit reallocations could not exceed eight per year during the term of the facility. The interest rate payable by each company on utilized funds was, at the borrowing company’s election, (i) the greater of the prevailing prime rate, the federal funds effective rate plus 0.5% and the one-month London Interbank Offered Rate (LIBOR) plus 1.0%, or (ii) the prevailing Eurodollar rate, plus a margin that varies according to the credit rating of the borrower. In order for a borrower to use the facility, certain representations and warranties had to be true and correct, and the borrower had to be in compliance with specified financial and other covenants, including (i) the requirement that each borrowing company maintain a ratio of total indebtedness to total capitalization of 65% or less, computed in accordance with the terms of the credit agreement, which calculation excluded from the definition of total indebtedness certain trust preferred securities and deferrable interest subordinated debt (not to exceed 15% of total capitalization), (ii) with certain exceptions, a restriction on sales or other dispositions of assets, and (iii) a restriction on the incurrence of liens on the assets of a borrower or any of its significant subsidiaries other than permitted liens. The credit agreement contained certain covenants and other customary agreements and requirements that, if not complied with, resulted in an event of default and the acceleration of repayment obligations of one or more of the borrowers thereunder. The absence of a material adverse change in PHI’s business, property, results of operations or financial condition was not a condition to the availability of credit under the credit agreement. The credit agreement did not include any rating triggers. Variable Rate Demand Bonds DPL has outstanding obligations in respect of Variable Rate Demand Bonds (VRDB). VRDBs are subject to repayment on the demand of the holders and, for this reason, are accounted for as short-term debt in accordance with GAAP. However, bonds submitted for purchase are remarketed by a remarketing agent on a best efforts basis. PHI expects that any bonds submitted for purchase will be remarketed successfully due to the creditworthiness of the issuer and, as applicable, the credit support, and because the remarketing resets the interest rate to the then-current market rate. The bonds may be converted to a fixed-rate, fixed-term option to establish a maturity which corresponds to the date of final maturity of the bonds. On this basis, PHI views VRDBs as a source of long-term financing. As of December 31, 2016 and December 31, 2015 , $105 million in variable rate demand bonds issued by DPL were outstanding and are included in the Long-term debt due within one year on Exelon's, PHI's and DPL's Consolidated Balance Sheet. Long-Term Debt The following tables present the outstanding long-term debt at the Registrants as of December 31, 2016 and 2015 : Exelon Maturity Date December 31, Rates 2016 2015 Long-term debt Rate stabilization bonds 5.82 % - 5.82 % 2017 $ 41 $ 120 First mortgage bonds (a) 1.70 % - 7.90 % 2017 - 2046 14,123 9,019 Senior unsecured notes 1.55 % - 7.60 % 2017 - 2046 11,868 9,803 Unsecured bonds 2.40 % - 6.35 % 2021 - 2046 2,300 1,750 Pollution control notes 2.50 % - 2.70 % 2025 - 2036 435 435 Nuclear fuel procurement contracts 3.15 % - 3.35 % 2018 - 2020 105 127 Notes payable and other (b)(c) 1.43 % - 7.83 % 2017 - 2053 576 314 Junior subordinated notes 6.50 % 2024 1,150 1,150 Contract payment - junior subordinated notes 2.50 % 2017 19 64 Long-term software licensing agreement 3.95 % 2024 103 111 Unsecured Tax-Exempt Bonds 5.40 % — 2031 112 — Medium-Terms Notes (unsecured) 6.81 % - 7.72 % — 2017 - 2027 40 — Transition bonds 5.05 % - 5.55 % — 2020 - 2023 124 — Nonrecourse debt: Fixed rates 2.29 % - 6.00 % 2031 - 2037 1,400 1,162 Variable rates 3.18 % - 5.00 % 2019 - 2021 915 1,058 Total long-term debt 33,311 25,113 Unamortized debt discount and premium, net (68 ) (63 ) Unamortized debt issuance costs (200 ) (180 ) Fair value adjustment 962 275 Long-term debt due within one year (2,430 ) (1,500 ) Long-term debt $ 31,575 $ 23,645 Long-term debt to financing trusts (d) Subordinated debentures to ComEd Financing III 6.35 % 2033 $ 206 $ 206 Subordinated debentures to PECO Trust III 7.38 % 2028 81 81 Subordinated debentures to PECO Trust IV 5.75 % 2033 103 103 Subordinated debentures to BGE Capital Trust II 6.20 % 2043 258 258 Total long-term debt to financing trusts 648 648 Unamortized debt issuance costs (7 ) (7 ) Long-term debt to financing trusts $ 641 $ 641 ____________________ (a) Substantially all of ComEd’s assets other than expressly excepted property and substantially all of PECO’s, Pepco's, DPL's and ACE's assets are subject to the liens of their respective mortgage indentures. (b) Includes capital lease obligations of $69 million and $29 million at December 31, 2016 and 2015 , respectively. Lease payments of $17 million , $18 million , $20 million , $5 million , $1 million , and $8 million will be made in 2017 , 2018 , 2019 , 2020 , 2021 and thereafter, respectively. (c) Includes financing related to Albany Green Energy, LLC (AGE), which is a consolidated variable interest entity (see Note 2 - Variable Interest Entities for additional information). The agreement is scheduled to expire on November 17, 2017, at a variable rate equal to LIBOR plus 1.25%. As of December 31, 2016, $198 million was outstanding. (d) Amounts owed to these financing trusts are recorded as Long-term debt to financing trusts within Exelon’s Consolidated Balance Sheets. Generation Maturity Date December 31, Rates 2016 2015 Long-term debt Senior unsecured notes 2.00 % - 7.60 % 2017 - 2042 $ 5,971 $ 5,971 Pollution control notes 2.50 % - 2.70 % 2025 - 2036 435 435 Nuclear fuel procurement contracts 3.15 % - 3.35 % 2018 - 2020 105 127 Notes payable and other (a)(b) 1.43 % - 7.83 % 2017 - 2035 382 166 Nonrecourse debt: Fixed rates 2.29 % - 6.00 % 2031 - 2037 1,400 1,162 Variable rates 3.18 % - 5.00 % 2019 - 2021 915 1,058 Total long-term debt 9,208 8,919 Fair value adjustment 115 127 Unamortized debt discount and premium, net (17 ) (17 ) Unamortized debt issuance costs (65 ) (70 ) Long-term debt due within one year (1,117 ) (90 ) Long-term debt $ 8,124 $ 8,869 ______________________ (a) Includes Generation’s capital lease obligations of $22 million and $21 million at December 31, 2016 and 2015 , respectively. Generation will make lease payments of $5 million , $5 million , $6 million and $5 million and $1 million in 2017 , 2018 , 2019 , 2020 and 2021 respectively. The capital lease matures in 2020. (b) Includes financing related to Albany Green Energy, LLC (AGE), which is a consolidated variable interest entity (see Note 2 - Variable Interest Entities for additional information). The agreement is scheduled to expire on November 17, 2017, at a variable rate equal to LIBOR plus 1.25%. As of December 31, 2016, $198 million was outstanding. ComEd Maturity Date December 31, Rates 2016 2015 Long-term debt First mortgage bonds (a) 2.15 % - 6.45 % 2017 - 2046 $ 6,954 $ 6,419 Notes payable and other (b) 6.95 % - 7.49 % 2018 - 2053 147 148 Total long-term debt 7,101 6,567 Unamortized debt discount and premium, net (22 ) (20 ) Unamortized debt issuance costs (46 ) (38 ) Long-term debt due within one year (425 ) (665 ) Long-term debt $ 6,608 $ 5,844 Long-term debt to financing trust (c) Subordinated debentures to ComEd Financing III 6.35 % 2033 $ 206 $ 206 Total long-term debt to financing trusts 206 206 Unamortized debt issuance costs (1 ) (1 ) Long-term debt to financing trusts $ 205 $ 205 ______________________ (a) Substantially all of ComEd’s assets other than expressly excepted property are subject to the lien of its mortgage indenture. (b) Includes ComEd’s capital lease obligations of $8 million at both December 31, 2016 and 2015 , respectively. Lease payments of less than $1 million will be made from 2017 through expiration at 2053. (c) Amount owed to this financing trust is recorded as Long-term debt to financing trust within ComEd’s Consolidated Balance Sheets. PECO Maturity Date December 31, Rates 2016 2015 Long-term debt First mortgage bonds (a) 1.70 % - 5.95 % 2018 - 2044 $ 2,600 $ 2,600 Total long-term debt 2,600 2,600 Unamortized debt discount and premium, net (5 ) (5 ) Unamortized debt issuance costs (15 ) (15 ) Long-term debt due within one year — (300 ) Long-term debt $ 2,580 $ 2,280 Long-term debt to financing trusts (b) Subordinated debentures to PECO Trust III 7.38 % 2028 $ 81 $ 81 Subordinated debentures to PECO Trust IV 5.75 % 2033 103 103 Long-term debt to financing trusts $ 184 $ 184 _____________________ (a) Substantially all of PECO’s assets are subject to the lien of its mortgage indenture. (b) Amounts owed to this financing trust are recorded as Long-term debt to financing trusts within PECO’s Consolidated Balance Sheets. BGE Maturity Date December 31, Rates 2016 2015 Long-term debt Rate stabilization bonds 5.82 % - 5.82 % 2017 $ 41 $ 120 Senior unsecured notes 2.40 % - 6.35 % 2021 - 2046 2,300 1,750 Total long-term debt 2,341 1,870 Unamortized debt discount and premium, net (4 ) (3 ) Unamortized debt issuance costs (15 ) (9 ) Long-term debt due within one year (41 ) (378 ) Long-term debt $ 2,281 $ 1,480 Long-term debt to financing trusts (a) Subordinated debentures to BGE Capital Trust II 6.20 % 2043 $ 258 $ 258 Total long-term debt to financing trusts 258 258 Unamortized debt issuance costs (6 ) (6 ) Long-term debt to financing trusts $ 252 $ 252 ___________________ (a) Amount owed to this financing trust is recorded as Long-term debt to financing trust within BGE’s Consolidated Balance Sheets. PHI Successor Predecessor Maturity December 31, Rates 2016 2015 Long-term debt Notes (unsecured) 6.13 % - 7.45 % 2017 - 2032 $ 266 $ 456 First mortgage bonds 3.05 % - 7.90 % 2018 - 2045 4,569 4,495 Unsecured Tax-Exempt Bonds 5.40 % 2031 112 112 Medium-Terms Notes (unsecured) 6.81 % - 7.72 % 2017 - 2027 40 40 Transition bonds (a) 5.05 % - 5.55 % 2020 - 2023 124 171 Notes payable and other (b) 6.20 % - 8.88 % 2019 - 2021 46 57 Total long-term debt 5,157 5,331 Unamortized debt discount and premium, net 1 (2 ) Unamortized debt issuance costs (2 ) (50 ) Fair value adjustment 742 — Long-term debt due within one year (253 ) (456 ) Long-term debt $ 5,645 $ 4,823 ________________ (a) Transition bonds are recorded as part of Long-term debt within ACE's Consolidated Balance Sheets. (b) Includes Pepco's capital lease obligations of $39 million and $50 million at December 31, 2016 and 2015 , respectively. Pepco Maturity December 31, Rates 2016 2015 Long-term debt First mortgage bonds (a) 3.05 % - 7.90 % 2022 - 2043 $ 2,335 $ 2,335 Notes payable and other (b) 6.20 % - 8.88 % 2019 - 2021 46 50 Total long-term debt 2,381 2,385 Unamortized debt discount and premium, net (2 ) (3 ) Unamortized debt issuance costs (30 ) (31 ) Long-term debt due within one year (16 ) (11 ) Long-term debt $ 2,333 $ 2,340 ________________ (a) Substantially all of Pepco's assets are subject to the lien of its respective mortgage indenture. (b) Includes capital lease obligations of $39 million and $50 million at December 31, 2016 and 2015 , respectively. Lease payments of $12 million , $13 million and $14 million will be made in 2017, 2018 and 2019, respectively. DPL Maturity December 31, Rates 2016 2015 Long-term debt First mortgage bonds (a) 3.50 % - 4.15 % 2023 - 2045 $ 1,196 $ 1,121 Unsecured Tax-Exempt Bonds 5.40 % 2031 112 112 Medium-Terms Notes (unsecured) 6.81 % - 7.72 % 2017 - 2027 40 40 Total long-term debt 1,348 1,273 Unamortized debt discount and premium, net 2 2 Unamortized debt issuance costs (10 ) (10 ) Long-term debt due within one year (119 ) (204 ) Long-term debt $ 1,221 $ 1,061 ___________________ (a) Substantially all of DPL's assets are subject to the lien of its respective mortgage indenture. ACE Maturity December 31, Rates 2016 2015 Long-term debt First mortgage bonds (a) 3.38 % - 7.75 % 2018 - 2036 $ 1,038 $ 1,039 Transition bonds (b) 5.05 % - 5.55 % 2020 - 2023 124 171 Total long-term debt 1,162 1,210 Unamortized debt discount and premium, net (1 ) (1 ) Unamortized debt issuance costs (6 ) (8 ) Long-term debt due within one year (35 ) (48 ) Long-term debt $ 1,120 $ 1,153 ___________________ (a) Substantially all of ACE's assets are subject to the lien of its respective mortgage indenture. (b) Maturities of ACE's Transition Bonds outstanding at December 31, 2016 are $35 million in 2017, $31 million in 2018, $18 million in 2019, $19 million in 2020 and $21 million in 2021. Long-term debt maturities at Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE in the periods 2017 through 2021 and thereafter are as follows: Year Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE 2017 $ 2,430 $ 1,117 $ 425 $ — $ 41 253 16 119 35 2018 1,742 104 840 500 — 298 13 4 281 2019 1,060 606 300 — — 154 124 12 18 2020 3,331 1,912 500 — — 19 — — 19 2021 2,400 888 350 300 300 262 2 — 260 Thereafter 22,996 (a) 4,581 4,892 (b) 1,984 (c) 2,258 (d) 4,171 2,226 1,213 549 Total $ 33,959 $ 9,208 $ 7,307 $ 2,784 $ 2,599 $ 5,157 $ 2,381 $ 1,348 $ 1,162 ____________________ (a) Includes $648 million due to ComEd, PECO and BGE financing trusts. (b) Includes $206 million due to ComEd financing trust. (c) Includes $184 million due to PECO financing trusts. (d) Includes $258 million due to BGE financing trust. PHI Merger Financing In May 2014, concurrently and in connection with entering into the agreement to acquire PHI, Exelon entered into a credit facility to which the lenders committed to provide Exelon a 364-day senior unsecured bridge credit facility of $7.2 billion to support the contemplated transaction and provide flexibility for timing of permanent financing. In June 2015, the remaining $3.2 billion bridge credit facility was terminated as a result of Exelon's issuance of $4.2 billion of long-term debt to fund a portion of the purchase price and related costs and expenses for the pending PHI merger and for general corporate purposes. In connection with the $4.2 billion issuance of Senior Unsecured Notes in 2015, the tranches due in 2025, 2035, and 2045 had to be redeemed at the principal amount plus a 1% premium of principal on December 31, 2015, if the PHI merger was not consummated or terminated prior to such date ("Special Mandatory Redemption"). Exelon also had the option to redeem those notes earlier at a 1% premium of principal, if Exelon determined that the merger would not be completed before December 31, 2015. On October 29, 2015, Exelon commenced a private exchange offer (Exchange Offer) to certain eligible holders whereby, for those that took part, the outstanding Senior Unsecured Notes in the 2025, 2035 and 2045 tranches were exchanged for new Senior Unsecured Notes. On December 2, 201 5, Exelon exchanged $1.9 billion of the Senior Unsecured Notes and paid a consent fee of approximately $5 million , which has been deferred on Exelon's Consolidated Balance Sheet and $4 million of third-party debt issuance costs, which were charged to earnings within Other, net on Exelon's Consolidated Statement of Operations and Comprehensive Income. On December 2, 2015, Exelon also redeemed $0.9 billion of Senior Unsecured Notes not exchanged in the Exchange Offer resulting in the payment of $9 million of redemption premium and the acceleration of the unamortized original issuance discount and deferred financing costs associated with the redeemed debt of $9 million , which were charged to earnings within Other, net on Exelon's Consolidated Statement of Operations and Comprehensive Income. Junior Subordinated Notes In June 2014, Exelon issued $1.15 billion of junior subordinated notes in the form of 23 million equity units at a stated amount of $50.00 per unit. Net proceeds from the issuance were $1.11 billion , net of a $35 million underwriter fee. The net proceeds were used to finance a portion of the merger and related costs and expenses for the pending PHI merger and for general corporate purposes. Each equity unit represents an undivided beneficial ownership interest in Exelon's 2.50% junior subordinated notes due in 2024 and a forward equity purchase contract which settles in 2017. The junior subordinated notes are expected to be remarketed in 2017. At the time of issuance, Exelon determined that the forward equity purchase contract had no value and therefore the entire $1.15 billion of junior subordinated notes were allocated to debt and recorded within Long-term debt on Exelon’s Consolidated Balance Sheet. Additionally, at the time of issuance, the present value of the contract payments of $131 million ("Contract Payment Obligation") were recorded to Long-term debt, representing the obligation to make contract payments, with an offsetting reduction to Common stock. The obligation for the contract payments is accreted to interest expense over the 3 year period ending in 2017 in Exelon’s Consolidated Statement of Operations and Comprehensive Income. During 2016, contract payments of $45 million related to the Contract Payment Obligation were included within Retirements of long-term debt in Exelon's Consolidated Statements of Cash Flows. During 2015, contract payments of $44 million related to the Contract Payment Obligation were included within Retirements of long-term debt in Exelon's Consolidated Statements of Cash Flows. During 2014, the Contract Payment Obligation was considered a non-cash financing transaction that was excluded from Exelon's Consolidated Statements of Cash Flows. Until settlement of the equity purchase contract, earnings per share dilution resulting from the equity unit issuance will be determined under the treasury stock method. Nonrecourse Debt Exelon and Generation have issued nonrecourse debt financing, in which approximately $2.8 billion of generating assets have been pledged as collateral at December 31, 2016 . Borrowings under these agreements are secured by the assets and equity of each respective project. The lenders do not have recourse against Exelon or Generation in the event of a default. If a specific project financing entity does not maintain compliance with its specific nonrecourse debt financing covenants, there could be a requirement to accelerate repayment of the associated debt or other borrowings earlier than the stated maturity dates. In these instances, if such repayment was not sat

Income Taxes (All Registrants)

Income Taxes (All Registrants)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes (All Registrants)	Income Taxes (All Registrants) Income tax expense (benefit) from continuing operations is comprised of the following components: Successor Predecessor For the Year Ended December 31, 2016 March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Included in operations: Federal Current $ 60 $ 513 $ (135 ) $ 63 $ 51 $ (118 ) $ (88 ) $ (26 ) $ (281 ) $ — Deferred 607 (247 ) 379 72 88 136 97 22 283 10 Investment tax credit amortization (24 ) (20 ) (2 ) — (1 ) — — — (1 ) — State Current 39 45 (4 ) 9 5 7 1 — (11 ) — Deferred 79 (1 ) 63 5 31 16 12 — 13 7 Total $ 761 $ 290 $ 301 $ 149 $ 174 $ 41 $ 22 $ (4 ) $ 3 $ 17 For the Year Ended December 31, 2015 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Included in operations: Federal Current $ 407 $ 546 $ (80 ) $ 64 $ 25 $ (54 ) $ (27 ) $ (2 ) $ 12 Deferred 566 16 310 69 126 126 73 27 103 Investment tax credit amortization (22 ) (19 ) (2 ) — (1 ) — — — (1 ) State Current (86 ) (90 ) 7 (10 ) — 6 2 3 17 Deferred 208 49 45 20 39 24 1 5 32 Total $ 1,073 $ 502 $ 280 $ 143 $ 189 $ 102 $ 49 $ 33 $ 163 For the Year Ended December 31, 2014 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Included in operations: Federal Current $ 121 $ 360 $ (171 ) $ 28 $ 24 $ (79 ) $ (45 ) $ (6 ) $ (153 ) Deferred 576 (35 ) 395 87 90 150 98 31 261 Investment tax credit amortization (20 ) (16 ) (2 ) — (1 ) — (1 ) (1 ) (1 ) State Current 42 35 7 (2 ) — (2 ) — (1 ) (10 ) Deferred (53 ) (137 ) 39 1 27 24 13 7 41 Total $ 666 $ 207 $ 268 $ 114 $ 140 $ 93 $ 65 $ 30 $ 138 The effective income tax rate from continuing operations varies from the U.S. Federal statutory rate principally due to the following: Successor Predecessor For the Year Ended December 31, 2016 March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL (a) ACE (a) PHI (a) PHI U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit (b) 3.3 3.3 5.6 1.3 5.0 15.7 52.7 6.2 5.8 11.9 Qualified nuclear decommissioning trust fund loss 3.4 7.8 — — — — — — — — Domestic production activities deduction — — — — — — — — — — Health care reform legislation — — — — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.2 ) (2.3 ) (0.3 ) (0.1 ) (0.1 ) (0.2 ) (3.7 ) 0.8 1.4 (0.9 ) Plant basis differences (4.8 ) — (0.6 ) (9.6 ) (2.7 ) (22.8 ) (25.5 ) 10.3 39.0 (13.5 ) Production tax credits and other credits (3.6 ) (8.2 ) — — — — — — — — Noncontrolling interests (0.2 ) (0.3 ) — — — — — — — — Statute of limitations expiration (0.4 ) (1.7 ) — — — — — — — — Penalties 1.9 — 4.5 — — — — — (0.7 ) — Merger Expenses 5.5 1.1 — — — 23.5 112.9 (44.9 ) (89.0 ) 11.1 Other (c) (0.6 ) (1.5 ) 0.1 (1.2 ) — (1.8 ) (2.2 ) 1.3 3.3 3.6 Effective income tax rate 38.3 % 33.2 % 44.3 % 25.4 % 37.2 % 49.4 % 169.2 % 8.7 % (5.2 )% 47.2 % For the Year Ended December 31, 2015 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 3.7 1.0 4.9 1.0 5.3 6.7 1.7 5.7 6.6 Qualified nuclear decommissioning trust fund income (0.4 ) (0.8 ) — — — — — — — Domestic production activities deduction (0.7 ) (1.3 ) — — — — — — — Health care reform legislation — — — — 0.1 — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.9 ) (1.5 ) (0.3 ) (0.1 ) (0.1 ) (0.1 ) (0.4 ) (0.6 ) (0.2 ) Plant basis differences (1.5 ) — (0.1 ) (8.7 ) (0.7 ) (5.8 ) (2.3 ) (1.3 ) (4.3 ) Production tax credits and other credits (1.9 ) (3.4 ) — — — — — — — Noncontrolling interests 0.3 0.5 — — — — — — — Statute of limitations expiration (1.4 ) (2.4 ) — — — — — — — Other (d) — — 0.2 0.2 — (0.5 ) 5.2 6.4 (3.2 ) Effective income tax rate 32.2 % 27.1 % 39.7 % 27.4 % 39.6 % 35.3 % 39.2 % 45.2 % 33.9 % For the Year Ended December 31, 2014 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 1.3 (1.9 ) 4.5 (0.1 ) 5.0 5.4 4.8 5.8 5.3 Qualified nuclear decommissioning trust fund income 2.4 4.8 — — — — — — — Domestic production activities deduction (2.0 ) (4.1 ) — — — — — — — Health care reform legislation 0.1 — 0.2 — 0.2 — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.1 ) (2.0 ) (0.3 ) (0.1 ) (0.3 ) (0.1 ) (0.3 ) (0.6 ) (0.3 ) Plant basis differences (1.9 ) — (0.1 ) (10.4 ) 0.2 (4.9 ) (2.4 ) (0.5 ) (4.5 ) Production tax credits and other credits (2.4 ) (4.8 ) — — — — — — — Noncontrolling interests (1.8 ) (3.7 ) — — — — — — — Statute of limitations expiration (2.6 ) (5.3 ) — — — — — — — Other (0.2 ) (1.1 ) 0.3 0.1 (0.2 ) (0.2 ) 1.4 (0.2 ) 0.8 Effective income tax rate 26.8 % 16.9 % 39.6 % 24.5 % 39.9 % 35.2 % 38.5 % 39.5 % 36.3 % _____________________ (a) DPL and ACE recognized a loss before income taxes for the year ended December 31, 2016 , and PHI recognized a loss before income taxes for the period of March 24, 2016, through December 31, 2016 . As a result, positive percentages represent an income tax benefit for the periods presented. (b) Includes a remeasurement of uncertain state income tax positions for Pepco and DPL. (c) At PECO, includes a cumulative adjustment related to an anticipated gas repairs tax return accounting method change. (d) Includes impacts of the PHI Global Settlement for Pepco, DPL, ACE, and PHI The tax effects of temporary differences and carryforwards, which give rise to significant portions of the deferred tax assets (liabilities), as of December 31, 2016 and 2015 are presented below: As of December 31, 2016 Successor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Plant basis differences $ (17,966 ) $ (4,192 ) $ (5,034 ) $ (3,095 ) $ (1,977 ) $ (1,678 ) $ (973 ) $ (869 ) $ (3,586 ) Accrual based contracts 434 (115 ) — — — — — — 548 Derivatives and other financial instruments (179 ) (162 ) (3 ) — — — — — (1 ) Deferred pension and postretirement obligation 2,287 (316 ) (453 ) (18 ) (43 ) (122 ) (74 ) (21 ) (111 ) Nuclear decommissioning activities (509 ) (509 ) — — — — — — — Deferred debt refinancing costs 325 44 (13 ) (1 ) (3 ) (7 ) (4 ) (2 ) 293 Regulatory assets and liabilities (3,319 ) — (226 ) 10 (240 ) (194 ) (75 ) (69 ) (1,205 ) Tax loss carryforward 189 61 29 — 22 27 39 14 77 Tax credit carryforward 446 493 — — — — — — — Investment in CENG (650 ) (650 ) — — — — — — — Other, net 1,485 403 351 99 27 66 34 34 225 Deferred income tax liabilities (net) $ (17,457 ) $ (4,943 ) $ (5,349 ) $ (3,005 ) $ (2,214 ) $ (1,908 ) $ (1,053 ) $ (913 ) $ (3,760 ) Unamortized investment tax credits (658 ) (626 ) (15 ) (1 ) (5 ) (2 ) (3 ) (4 ) (9 ) Total deferred income tax liabilities (net) and unamortized investment tax credits $ (18,115 ) $ (5,569 ) $ (5,364 ) $ (3,006 ) $ (2,219 ) $ (1,910 ) $ (1,056 ) $ (917 ) $ (3,769 ) As of December 31, 2015 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Plant basis differences $ (13,393 ) $ (4,269 ) $ (4,424 ) $ (2,901 ) $ (1,821 ) $ (1,599 ) $ (915 ) $ (791 ) $ (3,342 ) Accrual based contracts (136 ) (136 ) — — — — — — — Derivatives and other financial instruments (203 ) (181 ) (4 ) — — — — — (1 ) Deferred pension and postretirement obligation 1,801 (371 ) (505 ) (9 ) (47 ) (95 ) (82 ) (20 ) (92 ) Nuclear decommissioning activities (592 ) (592 ) — — — — — — — Deferred debt refinancing costs 133 48 (15 ) (1 ) (4 ) (8 ) (4 ) (3 ) (15 ) Regulatory assets and liabilities (1,706 ) — (219 ) 16 (264 ) (202 ) (91 ) (93 ) (414 ) Tax loss carryforward 103 56 — — 33 141 122 8 378 Tax credit carryforward 327 374 — — — — — — 6 Investment in CENG (595 ) (595 ) — — — — — — — Other, net 1,112 425 270 105 27 42 29 18 103 Deferred income tax liabilities (net) $ (13,149 ) $ (5,241 ) $ (4,897 ) $ (2,790 ) $ (2,076 ) $ (1,721 ) $ (941 ) $ (881 ) $ (3,377 ) Unamortized investment tax credits (622 ) (598 ) (17 ) (2 ) (5 ) (2 ) (4 ) (4 ) (15 ) Total deferred income tax liabilities (net) and unamortized investment tax credits $ (13,771 ) $ (5,839 ) $ (4,914 ) $ (2,792 ) $ (2,081 ) $ (1,723 ) $ (945 ) $ (885 ) $ (3,392 ) The following table provides the Registrants’ carryforwards and any corresponding valuation allowances as of December 31, 2016 . Successor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Federal Federal net operating loss $ 282 (a) $ 11 $ 82 $ — $ — $ 44 $ 38 $ 18 $ 121 Deferred taxes on Federal net operating loss 99 4 29 — — 15 13 6 42 Federal general business credits carryforwards 511 (b) 509 1 — 1 — — — — State State net operating losses and credit carryforwards 3,501 (c) 1,245 (c) — — 425 (d) 360 (e) 639 (f) 272 (g) 1,522 (h) Deferred taxes on state tax attributes (net) 186 65 — — 23 20 36 16 86 Valuation allowance on state tax attributes 20 9 — — 1 — — — 10 _____________________ (a) Exelon's federal net operating loss will begin expiring in 2032. (b) Exelon’s federal general business credit carryforwards will begin expiring in 2033. (c) Exelon’s and Generation's state net operating losses and credit carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2017. (d) BGE's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2026. (e) Pepco's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2028. (f) DPL's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2023. (g) ACE's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2032. (h) PHI's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2023. Tabular reconciliation of unrecognized tax benefits The following tables provide a reconciliation of the Registrants’ unrecognized tax benefits as of December 31, 2016 , 2015 and 2014 : Successor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Unrecognized tax benefits at January 1, 2016 $ 1,078 $ 534 $ 142 $ — $ 120 $ 8 $ 3 $ — $ 22 Merger balance transfer 22 5 — — — — — — (5 ) Increases based on tax positions related to 2016 108 10 — — — 21 16 22 59 Change to positions that only affect timing (332 ) (12 ) (154 ) — — — — — — Increases based on tax positions prior to 2016 88 — — — — 51 18 — 96 Decreases based on tax positions prior to 2016 (21 ) (20 ) — — — — — — — Decrease from settlements with taxing authorities (27 ) (27 ) — — — — — — — Decreases from expiration of statute of limitations — — — — — — — — — Unrecognized tax benefits at December 31, 2016 $ 916 $ 490 $ (12 ) $ — $ 120 $ 80 $ 37 $ 22 $ 172 Predecessor Generation ComEd PECO BGE Pepco DPL ACE PHI Unrecognized tax benefits at January 1, 2015 $ 1,829 $ 1,357 $ 149 $ 44 $ — $ — $ — $ — $ 702 Increases based on tax positions related to 2015 108 — — — 106 — — — — Change to positions that only affect timing (705 ) (659 ) (7 ) (44 ) — — — — (688 ) Increases based on tax positions prior to 2015 79 65 — — 14 8 3 — 11 Decreases based on tax positions prior to 2015 (116 ) (112 ) — — — — — — — Decrease from settlements with taxing authorities (31 ) (31 ) — — — — — — — Decreases from expiration of statute of limitations (86 ) (86 ) — — — — — — (3 ) Unrecognized tax benefits at December 31, 2015 $ 1,078 $ 534 $ 142 $ — $ 120 $ 8 $ 3 $ — $ 22 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Unrecognized tax benefits at January 1, 2014 $ 2,175 $ 1,415 $ 324 $ 44 $ — $ 45 $ 3 $ 3 $ 743 Increases based on tax positions related to 2014 15 15 — — — — — — — Change to positions that only affect timing (255 ) 33 (175 ) — — (45 ) (3 ) (3 ) (41 ) Increases based on tax positions prior to 2014 18 18 — — — — — — — Decreases based on tax positions prior to 2014 (1 ) (2 ) — — — — — — — Decreases from settlements with taxing authorities (35 ) (34 ) — — — — — — — Decreases from expiration of statute of limitations (88 ) (88 ) — — — — — — — Unrecognized tax benefits at December 31, 2014 $ 1,829 $ 1,357 $ 149 $ 44 $ — $ — $ — $ — $ 702 Exelon, Generation, and ComEd have $ 83 million , $ 7 million , and $ (12) million of unrecognized tax benefits balance at December 31, 2016 for which the ultimate tax benefit is highly certain, but for which there is uncertainty about the timing of such benefits. Exelon, Generation, and ComEd had $ 415 million , $ 20 million , and $ 142 million of unrecognized tax benefits at December 31, 2015 for which the ultimate tax benefit is highly certain, but for which there is uncertainty about the timing of such benefits Exelon, Generation, ComEd, PECO, and PHI had $ 1,122 million , $ 680 million , $ 149 million , $ 43 million , and $ 686 million of unrecognized tax benefits at December 31, 2014 for which the ultimate tax benefit is highly certain, but for which there is uncertainty about the timing of such benefits The disallowance of such positions would not materially affect the annual effective tax rate but would accelerate the payment of cash to, or defer the receipt of the cash tax benefit from, the taxing authority to an earlier or later period respectively. Unrecognized tax benefits that if recognized would affect the effective tax rate Exelon, Generation, PHI, Pepco, ACE, and DPL have $633 million , $483 million , $ 93 million , $ 21 million , $ 22 million , and $ 16 million , respectively, of unrecognized tax benefits at December 31, 2016 that, if recognized, would decrease the effective tax rate. BGE, PHI, Pepco, and DPL have $120 million , $ 80 million , $ 59 million , and $ 21 million of unrecognized tax benefits at December 31, 2016 that, if recognized, may be included in future base rates and that portion would have no impact to the effective tax rate. Exelon, Generation, and PHI had $538 million , $509 million , and $ 11 million , respectively, of unrecognized tax benefits at December 31, 2015 that, if recognized, would decrease the effective tax rate. BGE, PHI, Pepco, and DPL had $ 120 million , $ 11 million , $ 8 million , and $ 3 million of unrecognized tax benefits at December 31, 2015 that, if recognized, may be included in future base rates and that portion would have no impact to the effective tax rate. Exelon, Generation, and PHI had $ 701 million , $ 672 million , and $ 15 million , respectively, of unrecognized tax benefits at December 31, 2014 that, if recognized, would decrease the effective tax rate. Reasonably possible that total amount of unrecognized tax benefits could significantly increase or decrease within 12 months after the reporting date Settlement of Income Tax Audits and Litigation As of December 31, 2016 , Exelon, Generation, PHI, Pepco, ACE and DPL have approximately $146 million , $19 million , $59 million , $21 million , $22 million , and $16 million , respectively, of unrecognized federal and state tax benefits that will decrease in the first quarter of 2017 due to the receipt in January of favorable IRS guidance as to whether certain business expenses should be capitalized or deducted. The recognition of these unrecognized tax benefits will decrease the effective tax rate in the first quarter of 2017. As of December 31, 2016 , Exelon, Generation, BGE, PHI, Pepco, and DPL have approximately $244 million , $44 million , $120 million , $80 million , $59 million , and $ 21 million , respectively, of unrecognized state tax benefits that could significantly decrease within the 12 months after the reporting date as a result of completing audits, potential settlements, and expected statute of limitation expirations. Of the above unrecognized tax benefits, Exelon and Generation have $44 million that, if recognized, would decrease the effective tax rate. The unrecognized tax benefit related to BGE, Pepco, and DPL if recognized, may be included in future base rates and that portion would have no impact to the effective tax rate. Total amounts of interest and penalties recognized The following tables represent the net interest and penalties receivable (payable), including interest and penalties related to tax positions reflected in the Registrants’ Consolidated Balance Sheets. Net interest receivable (payable) as of Exelon Generation ComEd PECO BGE Pepco DPL ACE December 31, 2016 $ (507 ) $ 46 $ (384 ) $ 8 $ (1 ) $ 1 $ — $ 1 December 31, 2015 (288 ) 80 (210 ) 3 (1 ) 20 3 24 Net penalties receivable (payable) as of Exelon Generation ComEd PECO BGE Pepco DPL ACE December 31, 2016 $ (106 ) $ — $ (86 ) $ — $ — $ — $ — $ — December 31, 2015 — — — — — — — — Successor Predecessor PHI December 31, 2016 December 31, 2015 Net interest receivable (payable) $ 2 $ (34 ) Net penalties receivable (payable) — — The following tables set forth the net interest and penalty expense, including interest and penalties related to tax positions, recognized in Interest expense, net and Other, net in Other income and deductions in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Net interest expense (income) for the years ended Exelon Generation ComEd PECO BGE Pepco DPL ACE December 31, 2016 $ 165 $ (13 ) $ 117 $ — $ — $ 6 $ — $ (1 ) December 31, 2015 (13 ) (31 ) 7 — — (4 ) — — December 31, 2014 (36 ) (50 ) 6 — 1 (1 ) — (1 ) Net penalty expense (income) for the years ended Exelon Generation ComEd PECO BGE Pepco DPL ACE December 31, 2016 $ 106 $ — $ 86 — $ — $ — $ — $ — $ — December 31, 2015 — — — — — — — — December 31, 2014 — — — — — — — — Successor Predecessor PHI March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 December 31, 2015 December 31, 2014 Net interest expense (income) $ (2 ) $ — $ (34 ) $ — Net penalty expense (income) — — — — Description of tax years that remain open to assessment by major jurisdiction Taxpayer Open Years Exelon (and predecessors) and subsidiaries consolidated Federal income tax returns 1999, 2001-2015 PHI Holdings and subsidiaries consolidated Federal income tax returns 2013-2015 Exelon and subsidiaries Illinois unitary income tax returns 2010-2015 Constellation combined New York corporate income tax returns 2010-March 2012 Exelon combined New York corporate income tax returns 2011-2015 Various separate company (excluding PECO) Pennsylvania corporate net income tax returns 2011-2015 PECO Pennsylvania separate company returns 2010-2015 DPL Delaware separate company returns Same as Federal ACE New Jersey separate company returns 2012-2015 Various separate company Maryland corporate net income tax returns Same as Federal Washington D.C. corporate income tax returns 2013-2015 Other Tax Matters Like-Kind Exchange Exelon, through its ComEd subsidiary, took a position on its 1999 income tax return to defer approximately $1.2 billion of tax gain on the sale of ComEd’s fossil generating assets. The gain was deferred by reinvesting a portion of the proceeds from the sale in qualifying replacement property under the like-kind exchange provisions of the IRC. The like-kind exchange replacement property purchased by Exelon included interests in three municipal-owned electric generation facilities which were properly leased back to the municipalities. The IRS disagreed with this position and asserted that the entire gain of approximately $1.2 billion was taxable in 1999. Exelon was unable to reach agreement with the IRS regarding the dispute over the like-kind exchange position. The IRS asserted that the Exelon purchase and leaseback transaction was substantially similar to a leasing transaction, known as a SILO, which the IRS does not respect as the acquisition of an ownership interest in property. A SILO is a “listed transaction” that the IRS has identified as a potentially abusive tax shelter under guidance issued in 2005. Accordingly, the IRS asserted that the sale of the fossil plants followed by the purchase and leaseback of the municipal owned generation facilities did not qualify as a like-kind exchange and the gain on the sale is fully subject to tax. The IRS also asserted a penalty of approximately $90 million for a substantial understatement of tax. In accordance with applicable accounting standards, Exelon was required to assess whether it was more-likely-than-not that to prevail in litigation. In light of the outcome of another case involving a listed transaction and Exelon’s determination that settlement was unlikely, Exelon concluded that subsequent to December 31, 2012, it was no longer more-likely-than-not that its position would be sustained. As a result, in the first quarter of 2013 Exelon recorded a non-cash charge to earnings of approximately $265 million , which represented the amount of interest expense (after-tax) and incremental state income tax expense for periods through March 31, 2013, that would be payable in the event that Exelon is unsuccessful in litigation. Of this amount, approximately $172 million was recorded at ComEd. Exelon has agreed to hold ComEd harmless from any unfavorable impacts on ComEd’s equity of the after-tax interest or penalty amounts. As a result, ComEd recorded on its consolidated balance sheet as of March 31, 2013, a $172 million receivable and non-cash equity contributions from Exelon. Based on applicable case law and the facts of the transaction, Exelon did not believe it was likely a penalty would be assessed. Accordingly, no charge was recorded for the penalty asserted nor for after-tax interest that could be due on the asserted penalty. On September 30, 2013, the IRS issued a notice of deficiency to Exelon for the like-kind exchange position. Exelon filed a petition on December 13, 2013 to initiate litigation in the United States Tax Court and the trial took place in August of 2015. Exelon was not required to remit any part of the asserted tax or penalty in order to litigate the issue. On September 19, 2016, the Tax Court rejected Exelon’s position in the case and ruled that Exelon was not entitled to defer gain on the transaction. In addition, contrary to Exelon’s evaluation that the penalty was unwarranted, the Tax Court ruled that Exelon is liable for the penalty and interest due on the asserted penalty. In the second quarter of 2017, Exelon expects to timely appeal this decision to the U.S. Court of Appeals for the Seventh Circuit. While it has strong arguments on appeal with respect to both the merits and the penalty, Exelon has determined that, pursuant to accounting standards, it is no longer more-likely-than-not to avoid the penalty. As a result, in the third quarter of 2016, Exelon and ComEd recorded a charge to earnings of approximately $106 million and $86 million , respectively, of penalty and approximately $ 94 million and $ 64 million , respectively, of after-tax interest. Exelon and ComEd recorded the penalty and pre-tax interest due on the asserted penalty to Other, net and Interest expense, net, respectively, on their Consolidated Statements of Operations. Consistent with Exelon’s agreement to continue to hold ComEd harmless from any unfavorable impact on its equity, ComEd recorded on its Consolidated Balance Sheets as of September 30, 2016, a $ 150 million receivable and non-cash equity contributions from Exelon. In order to appeal the decision, Exelon is required to pay the tax, penalty and interest at the time Exelon files its appeal (expected in the second quarter of 2017). While the final calculation of tax, penalty and interest has not yet been finalized by the IRS, Exelon estimates that a payment of approximately $1.4 billion related to the like-kind exchange will be due, including $300 million from ComEd, in the second quarter of 2017. While Exelon will receive a tax benefit of $400 million associated with the deduction for the interest, Exelon expects to have a net operating loss carryforward and thus does not expect to realize the cash benefit until 2018. After taking into account these interest deduction tax benefits, the total estimated net cash outflow for the like-kind exchange is $1 billion , of which approximately $300 million is attributable to ComEd after giving consideration to Exelon’s agreement to hold ComEd harmless from any unfavorable impacts of after-tax interest or penalty amounts on ComEd’s equity. Upon a final appellate decision, which could take up to several years, Exelon expects to receive $80 million related to final interest computations . Of the above amounts payable, Exelon deposited with the IRS approximately $ 1.25 billion in October of 2016. The remaining amount will be paid in the second quarter of 2017 at the time Exelon files its appeal of the Tax Court decision. Exelon funded the $ 1.25 billion deposit with a combination of cash on hand and short-term borrowings. The deposit is reflected as a current asset and the related liabilities for the tax, penalty, and interest are included on Exelon’s balance sheet as current obligations. As of December 31, 2016 , ComEd has a total receivable from Exelon pursuant to the hold harmless agreement of $345 million , which is included in Current Receivables from Affiliates on ComEd’s Consolidated Balance Sheet. Under the agreement, Exelon will settle this receivable with ComEd no later than the time that the payments related to the like-kind exchange are due to the IRS, currently anticipated in the second quarter of 2017. Exelon will not seek recovery from ComEd customers for any interest or penalty amounts associated with the like-kind exchange tax position. As previously disclosed, in the first quarter of 2014, Exelon entered into an agreement to terminate its investment in one of the three municipal-owned electric generation properties in exchange for a net early termination amount of $335 million . On March 31, 2016, Exelon entered into an agreement to terminate its interests in the remaining two municipal-owned electric generation properties in exchange for $360 million . PHI Global Tax Settlement On November 18, 2015, PHI entered into a settlement with the IRS and the DOJ (the Global Tax Settlement) to primarily provide for the resolution of the uncertain tax treatment of its previously held cross-border energy lease investments involving public utility assets located outside of the United States structured as sale-in, lease-out, or SILO, transactions. As a result of the Global Tax Settlement in the fourth quarter of 2015, PHI re-measured uncertain tax positions resulting in the recognition of a tax benefit of $ 35 million , including $ 26 million related to continuing operations and $ 9 million related to discontinued operations. PHI also recorded an interest benefit, net of tax, of $ 21 million . Pepco recorded a tax benefit of $ 6 million and interest benefit, net of tax, of $ 3 million . ACE and DPL recorded a tax expense of $ 3 million and $ 3 million , respectively. Long-Term State Tax Apportionment (Exelon, Generation and PHI) Exelon, Generation and PHI periodically review events that may significantly impact how income is apportioned among the states and, therefore, the calculation of their respective deferred state income taxes. Events that may require Exelon, Generation and PHI to update their long-term state tax apportionment include significant changes in tax law and/or significant operational changes, such as the merger with PHI. As a result of the merger, Exelon and Generation reevaluated their long-term state tax apportionment for all states where they have state income tax obligations, which include Delaware, Illinois, Maryland, New Jersey, Pennsylvania, and Washington D.C., as well as other states. The total effect of revising the long-term state tax apportionment resulted in the recording of deferred state tax benefit in the amount of $1 million and $6 million , net of tax, for Exelon and Generation, respectively. Further, Exelon and PHI recorded deferred state tax liabilities of $59 million and $8 million , net of tax, respectively, as part of purchase accounting during the first quarter of 2016. The long-term state tax apportionment was revised in the fourth quarter of 2016 pursuant to Exelon's long-term state tax apportionment policy, resulting in the recording of a deferred state tax expense for Exelon and Generation of $8 million and $14 million , net of tax. Allocation of Tax Benefits (All Registrants) Generation, ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE are all party to an agreement with Exelon and other subsidiaries of Exelon that provides for the allocation of consolidated tax liabilities and benefits (Tax Sharing Agreement). The Tax Sharing Agreement provides that each party is allocated an amount of tax similar to that which would be owed had the party been separately subject to tax. In addition, any net benefit attributable to Exelon is reallocated to the other Registrants. That allocation is treated as a contribution to the capital of the party receiving the benefit. During 2016, Generation, PECO, and BGE recorded an allocation of Federal tax benefits from Exelon under the Tax Sharing Agreement of $94 million , $18 million , and $8 million respectively. ComEd did not record an allocation of Federal tax benefits from Exelon under the Tax Sharing Agreement as a result of a tax net operating loss. PHI, Pepco, DPL, and ACE did not record an allocation of Federal tax benefits from Exelon as they were not a part of Exelon's 2015 consolidated tax return. During 2015, Generation, PECO, and BGE recorded an allocation of Federal tax benefits from Exelon under the Tax Sharing Agreement of $57 million , $16 million , and $7 million respectively. ComEd did not record an allocation of Federal tax benefits from Exelon under the Tax Sharing Agreement as a result of a tax net operating loss. During 2014, Generation and PECO recorded an allocation of Federal tax benefits from Exelon under the Tax Sharing Agreement of $55 million and $25 million , respectively. ComEd and BGE did not record an allocation of Federal tax benefits from Exelon under the Tax Sharing Agreement as a result of tax net operating losses.

Asset Retirement Obligations (A

Asset Retirement Obligations (All Registrants)	12 Months Ended
	Dec. 31, 2016
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations (All Registrants)	Asset Retirement Obligations (All Registrants) Nuclear Decommissioning Asset Retirement Obligations Generation has a legal obligation to decommission its nuclear power plants following the expiration of their operating licenses. To estimate its decommissioning obligation related to its nuclear generating stations for financial accounting and reporting purposes, Generation uses a probability-weighted, discounted cash flow model which, on a unit-by-unit basis, considers multiple outcome scenarios that include significant estimates and assumptions, and are based on decommissioning cost studies, cost escalation rates, probabilistic cash flow models and discount rates. Generation updates its ARO annually unless circumstances warrant more frequent updates, based on its review of updated cost studies and its annual evaluation of cost escalation factors and probabilities assigned to various scenarios. The following table provides a rollforward of the nuclear decommissioning ARO reflected on Exelon’s and Generation’s Consolidated Balance Sheets, from January 1, 2015 to December 31, 2016 : Exelon and Generation Nuclear decommissioning ARO at January 1, 2015 $ 6,961 Accretion expense 387 Net increase for changes in and timing of estimated future cash flows 901 Costs incurred related to decommissioning plants (3 ) Nuclear decommissioning ARO at December 31, 2015 (a) 8,246 Accretion expense 436 Net increase for changes in and timing of estimated future cash flows 61 Costs incurred related to decommissioning plants (9 ) Nuclear decommissioning ARO at December 31, 2016 (a) $ 8,734 _________________________ (a) Includes $ 10 million and $ 7 million as the current portion of the ARO at December 31, 2016 and 2015 , respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets. During 2016 , Generation’s total nuclear ARO increased by approximately $488 million , primarily reflecting year-to-date accretion of the ARO liability of approximately $436 million due to the passage of time and impacts of ARO updates completed during 2016 to reflect changes in amounts and timing of estimated decommissioning cash flows. The $61 million increase in the ARO during 2016 for changes in the amounts and timing of estimated decommissioning cash flows was driven by multiple adjustments throughout the year, some with offsetting impacts. These adjustments include increases of $288 million resulting from the change in the assumed DOE spent fuel acceptance date for disposal from 2025 to 2030 as well as increases resulting from updates to the cost studies of Oyster Creek, Zion, Calvert Cliffs, R.E. Ginna and Nine Mile Point. These increases were partially offset by a decrease of $165 million resulting from changes to the decommissioning scenarios and their probabilities as well as reductions in estimated cost escalation rates, primarily for labor, energy and waste burial costs. Most of the increase to the ARO resulting from the June 2, 2016, announcement to early retire Clinton and Quad Cities was reversed pursuant to the December 7, 2016, enactment of the Illinois FEJA. See Note 9 - Early Nuclear Plant Retirements for additional information. The financial statement impact related to changes in the ARO, on an individual unit basis, due to the changes in, and timing of, estimated cash flows primarily resulted in a corresponding change in the unit’s ARC within Property, plant and equipment on Exelon’s and Generation’s Consolidated Balance Sheets. If the ARO decreases for a unit that does not have any remaining ARC, the corresponding change is recorded as a credit to income in Operating and maintenance expense within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income . Approximately $89 million of the 2016 adjustment resulted in a credit to income, which is included in Operating and maintenance expense within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. During 2015 , Generation’s ARO increased by approximately $1.3 billion . The increase was primarily driven by an increase of approximately $630 million for costs expected to be incurred for required site security during the decommissioning periods in which SNF remains on-site and until major reactor components and buildings have been dismantled and removed. This projected increase was based on emerging industry experience at nuclear sites in the planning or early stage of decommissioning indicating greater than originally expected numbers of security personnel required to be on site during these decommissioning periods. Generation will continue to monitor emerging security cost trends, including potential strategies to limit such costs by, for example, optimizing the transfer of SNF when DOE starts taking possession of SNF or increasing the use of dry SNF storage, and will adjust the ARO liability accordingly. The 2015 increase in the ARO included an increase of approximately $285 million for the impacts of a change implemented in the 2015 annual assessment of Generation’s SNF storage and disposal cost estimation methodology to better align the projected timing of SNF transfers to the DOE with assumed plant shutdown dates as well as higher assumed probabilities of early retirements of certain economically challenged nuclear plants (See Note 9 - Early Nuclear Plant Retirements for additional information) and further accretion of the obligation. These increases were partially offset by reductions in estimated cost escalation rates, primarily for labor and energy costs. Nuclear Decommissioning Trust Fund Investments NDT funds have been established for each generating station unit to satisfy Generation’s nuclear decommissioning obligations. Generally, NDT funds established for a particular unit may not be used to fund the decommissioning obligations of any other unit. The NDT funds associated with Generation's nuclear units have been funded with amounts collected from the previous owners and their respective utility customers. PECO is authorized to collect funds, in revenues, for decommissioning the former PECO nuclear plants through regulated rates, and these collections are scheduled through the operating lives of the former PECO plants. The amounts collected from PECO customers are remitted to Generation and deposited into the NDT funds for the unit for which funds are collected. Every five years, PECO files a rate adjustment with the PAPUC that reflects PECO’s calculations of the estimated amount needed to decommission each of the former PECO units based on updated fund balances and estimated decommissioning costs. The rate adjustment is used to determine the amount collectible from PECO customers. The most recent rate adjustment occurred on January 1, 2013, and the effective rates currently yield annual collections of approximately $ 24 million . The next five-year adjustment is expected to be reflected in rates charged to PECO customers effective January 1, 2018. Aside from the former PECO units, Generation does not currently collect any amounts, nor is there any mechanism by which Generation can seek to collect additional amounts, from utility customers. Apart from the contributions made to the NDT funds from amounts previously collected from ComEd and currently collected from PECO customers, Generation has not made contributions to the NDT funds. Any shortfall of funds necessary for decommissioning, determined for each generating station unit, is ultimately required to be funded by Generation, with the exception of a shortfall for the current decommissioning activities at Zion Station, where certain decommissioning activities have been transferred to a third-party (see Zion Station Decommissioning below) and the CENG units, where any shortfall is required to be funded by both Generation and EDF. Generation, through PECO, has recourse to collect additional amounts from PECO customers related to a shortfall of NDT funds for the former PECO units, subject to certain limitations and thresholds, as prescribed by an order from the PAPUC. Generally, PECO, and likewise Generation will not be allowed to collect amounts associated with the first $ 50 million of any shortfall of trust funds compared to decommissioning costs, as well as 5% of any additional shortfalls, on an aggregate basis for all former PECO units. The initial $ 50 million and up to 5% of any additional shortfalls would be borne by Generation. No recourse exists to collect additional amounts from utility customers for any of Generation's other nuclear units. With respect to the former ComEd and PECO units, any funds remaining in the NDTs after all decommissioning has been completed are required to be refunded to ComEd’s or PECO’s customers, subject to certain limitations that allow sharing of excess funds with Generation related to the former PECO units. With respect to Generation's other nuclear units, Generation retains any funds remaining after decommissioning. However, in connection with CENG's acquisition of the Nine Mile Point and Ginna plants and settlements with certain regulatory agencies, CENG is subject to certain conditions pertaining to nuclear decommissioning trust funds that, if met, could possibly result in obligations to make payments to certain third parties (clawbacks). For Nine Mile Point and Ginna, the clawback provisions are triggered only in the event that the required decommissioning activities are discontinued or not started or completed in a timely manner. In the event that the clawback provisions are triggered for Nine Mile Point, then, depending upon the triggering event, an amount equal to 50% of the total amount withdrawn from the funds for non-decommissioning activities or 50% of any excess funds in the trust funds above the amounts required for decommissioning (including spent fuel management and decommissioning) is to be paid to the Nine Mile Point sellers. In the event that the clawback provisions are triggered for Ginna, then an amount equal to any estimated cost savings realized by not completing any of the required decommissioning activities is to be paid to the Ginna sellers. Generation expects to comply with applicable regulations and timely commence and complete all required decommissioning activities. At December 31, 2016 , and 2015 , Exelon and Generation had NDT fund investments totaling $ 11,061 million and $10,342 million , respectively. For additional information related to the NDT fund investments, refer to Note 12 — Fair Value of Financial Assets and Liabilities . The following table provides unrealized gains on NDT funds for 2016 , 2015 and 2014 : Exelon and Generation For the Years Ended December 31, 2016 2015 2014 Net unrealized gains (losses) on decommissioning trust funds—Regulatory Agreement Units (a) $ 216 $ (282 ) $ 180 Net unrealized gains (losses) on decommissioning trust funds—Non-Regulatory Agreement Units (b)(c) 194 (197 ) 134 _______________________ (a) Net unrealized gains (losses) related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets. (b) Excludes $ (1) million , $7 million and $ 29 million of net unrealized gains (losses) related to the Zion Station pledged assets in 2016 , 2015 and 2014 , respectively. Net unrealized gains related to Zion Station pledged assets are included in the Payable for Zion Station decommissioning on Exelon’s and Generation’s Consolidated Balance Sheets. (c) Net unrealized gains (losses) related to Generation’s NDT funds with Non-Regulatory Agreement Units are included within Other, net in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. Interest and dividends on NDT fund investments are recognized when earned and are included in Other, net in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. Interest and dividends earned on the NDT fund investments for the Regulatory Agreement Units are eliminated within Other, net in Exelon’s and Generation’s Consolidated Statement of Operations and Comprehensive Income. Accounting Implications of the Regulatory Agreements with ComEd and PECO . Based on the regulatory agreement with the ICC that dictates Generation’s obligations related to the shortfall or excess of NDT funds necessary for decommissioning the former ComEd units on a unit-by-unit basis, as long as funds held in the NDT funds are expected to exceed the total estimated decommissioning obligation, decommissioning-related activities, including realized and unrealized gains and losses on the NDT funds and accretion of the decommissioning obligation, are generally offset within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. The offset of decommissioning-related activities within the Consolidated Statement of Operations and Comprehensive Income results in an equal adjustment to the noncurrent payables to affiliates at Generation and an adjustment to the regulatory liabilities at Exelon. Likewise, ComEd has recorded an equal noncurrent affiliate receivable from Generation and corresponding regulatory liability. Should the expected value of the NDT fund for any former ComEd unit fall below the amount of the expected decommissioning obligation for that unit, the accounting to offset decommissioning-related activities in the Consolidated Statement of Operations and Comprehensive Income for that unit would be discontinued, the decommissioning-related activities would be recognized in the Consolidated Statements of Operations and Comprehensive Income and the adverse impact to Exelon’s and Generation’s results of operations and financial position could be material. As of December 31, 2016 , the NDT funds of each of the former ComEd units, except for Zion (see Zion Station Decommissioning below), are expected to exceed the related decommissioning obligation for each of the units. For the purposes of making this determination, the decommissioning obligation referred to is different, as described below, from the calculation used in the NRC minimum funding obligation filings based on NRC guidelines. Based on the regulatory agreement supported by the PAPUC that dictates Generation’s rights and obligations related to the shortfall or excess of trust funds necessary for decommissioning the former PECO units, regardless of whether the funds held in the NDT funds are expected to exceed or fall short of the total estimated decommissioning obligation, decommissioning-related activities are generally offset within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. The offset of decommissioning-related activities within the Consolidated Statement of Operations and Comprehensive Income results in an equal adjustment to the noncurrent payables to affiliates at Generation and an adjustment to the regulatory liabilities at Exelon. Likewise, PECO has recorded an equal noncurrent affiliate receivable from Generation and a corresponding regulatory liability. Any changes to the PECO regulatory agreements could impact Exelon’s and Generation’s ability to offset decommissioning-related activities within the Consolidated Statement of Operations and Comprehensive Income, and the impact to Exelon’s and Generation’s results of operations and financial position could be material. The decommissioning-related activities related to the Non-Regulatory Agreement Units are reflected in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. Refer to Note 3 — Regulatory Matters and Note 27 — Related Party Transactions for information regarding regulatory liabilities at ComEd and PECO and intercompany balances between Generation, ComEd and PECO reflecting the obligation to refund to customers any decommissioning-related assets in excess of the related decommissioning obligations. Zion Station Decommissioning On September 1, 2010, Generation completed an Asset Sale Agreement (ASA) with EnergySolutions Inc. and its wholly owned subsidiaries, EnergySolutions, LLC (EnergySolutions) and ZionSolutions under which ZionSolutions has assumed responsibility for decommissioning Zion Station, which is located in Zion, Illinois and ceased operation in 1998. Specifically, Generation transferred to ZionSolutions substantially all of the assets (other than land) associated with Zion Station, including assets held in related NDT funds. In consideration for Generation’s transfer of those assets, ZionSolutions assumed decommissioning and other liabilities, excluding the obligation to dispose of SNF and decommission the SNF dry storage facility, associated with Zion Station. Pursuant to the ASA, ZionSolutions will periodically request reimbursement from the Zion Station-related NDT funds for costs incurred related to its decommissioning efforts at Zion Station. During 2013, EnergySolutions entered a definitive acquisition agreement and was acquired by another Company. Generation reviewed the acquisition as it relates to the ASA to decommission Zion Station. Based on that review, Generation determined that the acquisition will not adversely impact decommissioning activities under the ASA. ZionSolutions is subject to certain restrictions on its ability to request reimbursements from the Zion Station NDT funds as defined within the ASA. Therefore, the transfer of the Zion Station assets did not qualify for asset sale accounting treatment and, as a result, the related NDT funds were reclassified to Pledged assets for Zion Station decommissioning within Generation’s and Exelon’s Consolidated Balance Sheets and will continue to be measured in the same manner as prior to the completion of the transaction. Additionally, the transferred ARO for decommissioning was replaced with a Payable for Zion Station decommissioning in Generation’s and Exelon’s Consolidated Balance Sheets. Changes in the value of the Zion Station NDT assets, net of applicable taxes, will be recorded as a change in the Payable to ZionSolutions. At no point will the payable to ZionSolutions exceed the project budget of the costs remaining to decommission Zion Station. Generation has retained its obligation for the SNF. Following ZionSolutions' completion of its contractual obligations and transfer of the NRC license to Generation, Generation will store the SNF at Zion Station until it is transferred to the DOE for ultimate disposal, and will complete all remaining decommissioning activities associated with the SNF dry storage facility. Generation has a liability of approximately $ 111 million , which is included within the nuclear decommissioning ARO at December 31, 2016 . Generation also has retained NDT assets to fund its obligation to maintain the SNF at Zion Station until transfer to the DOE and to complete all remaining decommissioning activities for the SNF storage facility. Any shortage of funds necessary to maintain the SNF and decommission the SNF storage facility is ultimately required to be funded by Generation. Any Zion Station NDT funds remaining after the completion of all decommissioning activities will be returned to ComEd customers in accordance with the applicable orders. The following table provides the pledged assets and payables to ZionSolutions, and withdrawals by ZionSolutions at December 31, 2016 and 2015 : Exelon and Generation 2016 2015 Carrying value of Zion Station pledged assets $ 113 $ 206 Payable to Zion Solutions (a) 104 189 Current portion of payable to Zion Solutions (b) 90 99 Cumulative withdrawals by Zion Solutions to pay decommissioning costs (c) 878 786 ___________________ (a) Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT Funds. The NDT Funds will be utilized to satisfy the tax obligations as gains and losses are realized. (b) Included in Other current liabilities within Exelon’s and Generation’s Consolidated Balance Sheets. (c) Includes project expenses to decommission Zion Station and estimated tax payments on Zion Station NDT fund earnings. ZionSolutions leased the land associated with Zion Station from Generation pursuant to a Lease Agreement. Under the Lease Agreement, ZionSolutions has committed to complete the required decommissioning work according to an established schedule and constructed a dry cask storage facility on the land and has loaded the SNF from the SNF pools onto the dry cask storage facility at Zion Station. Rent payable under the Lease Agreement is $ 1.00 per year, although the Lease Agreement requires ZionSolutions to pay property taxes associated with Zion Station and penalty rents may accrue if there are unexcused delays in the progress of decommissioning work at Zion Station or the construction of the dry cask SNF storage facility. To reduce the risk of default by ZionSolutions, EnergySolutions provided a $ 200 million letter of credit to be used to fund decommissioning costs in the event the NDT assets are insufficient. In accordance with the terms of the ASA, the letter of credit was reduced to $173 million in November 2016 due to the completion of key decommissioning milestones. EnergySolutions and its parent company have also provided a performance guarantee and EnergySolutions has entered into other agreements that will provide rights and remedies for Generation and the NRC in the case of other specified events of default, including a special purpose easement for disposal capacity at the EnergySolutions site in Clive, Utah, for all LLRW volume of Zion Station. NRC Minimum Funding Requirements NRC regulations require that licensees of nuclear generating facilities demonstrate reasonable assurance that funds will be available in specified minimum amounts to decommission the facility at the end of its life. The estimated decommissioning obligations as calculated using the NRC methodology differ from the ARO recorded on Generation’s and Exelon’s Consolidated Balance Sheets primarily due to differences in the type of costs included in the estimates, the basis for estimating such costs, and assumptions regarding the decommissioning alternatives to be used, potential license renewals, decommissioning cost escalation, and the growth rate in the NDT funds. Under NRC regulations, if the minimum funding requirements calculated under the NRC methodology are less than the future value of the NDT funds, also calculated under the NRC methodology, then the NRC requires either further funding or other financial guarantees. Key assumptions used in the minimum funding calculation using the NRC methodology at December 31, 2016 include: (1) consideration of costs only for the removal of radiological contamination at each unit; (2) the option on a unit-by-unit basis to use generic, non-site specific cost estimates; (3) consideration of only one decommissioning scenario for each unit; (4) the plants cease operation at the end of their current license lives (with no assumed license renewals for those units that have not already received renewals and with an assumed end-of-operations date of 2019 for Oyster Creek); (5) the assumption of current nominal dollar cost estimates that are neither escalated through the anticipated period of decommissioning, nor discounted using the CARFR; and (6) assumed annual after-tax returns on the NDT funds of 2% ( 3% for the former PECO units, as specified by the PAPUC). In contrast, the key criteria and assumptions used by Generation to determine the ARO and to forecast the target growth in the NDT funds at December 31, 2016 include: (1) the use of site specific cost estimates that are updated at least once every five years; (2) the inclusion in the ARO estimate of all legally unavoidable costs required to decommission the unit (e.g., radiological decommissioning and full site restoration for certain units, on-site spent fuel maintenance and storage subsequent to ceasing operations and until DOE acceptance, and disposal of certain low-level radioactive waste); (3) the consideration of multiple scenarios where decommissioning and site restoration activities, as applicable, are completed under four possible scenarios ranging from 10 to 70 years after the cessation of plant operations; (4) the consideration of multiple end of life scenarios; (5) the measurement of the obligation at the present value of the future estimated costs and an annual average accretion of the ARO of approximately 5% through a period of approximately 30 years after the end of the extended lives of the units; and (6) an estimated targeted annual pre-tax return on the NDT funds of 5.3% to 5.9% (as compared to a historical 5-year annual average pre-tax return of approximately 8% ). Generation is required to provide to the NRC a biennial report by unit (annually for units that have been retired or are within five years of the current approved license life), based on values as of December 31, addressing Generation’s ability to meet the NRC minimum funding levels. Depending on the value of the trust funds, Generation may be required to take steps, such as providing financial guarantees through letters of credit or parent company guarantees or making additional contributions to the trusts, which could be significant, to ensure that the trusts are adequately funded and that NRC minimum funding requirements are met. As a result, Exelon’s and Generation’s cash flows and financial position may be significantly adversely affected. Generation filed its biennial decommissioning funding status report with the NRC on March 31, 2015. This report reflects the status of decommissioning funding assurance for all units as of December 31, 2014. Due to increased cost estimates received in the second half of 2014, Braidwood Unit 1, Braidwood Unit 2, and Byron Unit 2 did not meet the NRC's minimum funding assurance criteria as of December 31, 2014. NRC guidance provides licensees with two years or by the time of submitting the next biennial report (on or before March 31, 2017) to resolve funding assurance shortfalls. On February 4, 2016, Generation submitted an updated decommissioning funding status report with the NRC for Braidwood Units 1 and 2, and Byron Unit 2. This report reflected the approved license renewals for these units, and showed adequate decommissioning funding assurance for each of the three units. On March 31, 2016, Generation submitted its NRC required annual decommissioning funding status report as of December 31, 2015 for reactors that have been shut down or are within five years of shut down (Dresden Unit 1, Oyster Creek, Zion and Peach Bottom Unit 1), except for Zion Station which is included in a separate report to the NRC submitted by EnergySolutions (see Zion Station Decommissioning above). The status report demonstrated adequate decommissioning funding assurance for all these units except for Peach Bottom Unit 1. As a former PECO plant, financial assurance for decommissioning Peach Bottom Unit 1 is provided by the NDT fund in addition to collections from PECO ratepayers. As discussed under Nuclear Decommissioning Trust Fund Investments above, the amount collected from PECO ratepayers will be adjusted in the next filing to the PAPUC with new rates effective January 1, 2018. Generation will file its next decommissioning funding status report with the NRC by March 31, 2017. This report will reflect the status of decommissioning funding assurance as of December 31, 2016. As the future values of trust funds change due to market conditions, the NRC minimum funding status of Generation’s units will change. In addition, if changes occur to the regulatory agreement with the PAPUC that currently allows amounts to be collected from PECO customers for decommissioning the former PECO units, the NRC minimum funding status of those plants could change at subsequent NRC filing dates. Non-Nuclear Asset Retirement Obligations (All Registrants) Generation has AROs for plant closure costs associated with its fossil and renewable generating facilities, including asbestos abatement, removal of certain storage tanks, restoring leased land to the condition it was in prior to construction of renewable generating stations and other decommissioning-related activities. PHI and the Utility Registrants have AROs primarily associated with the abatement and disposal of equipment and buildings contaminated with asbestos and PCBs. See Note 1 — Significant Accounting Policies for additional information on the Registrants’ accounting policy for AROs. The following table provides a rollforward of the non-nuclear AROs reflected on the Registrants’ Consolidated Balance Sheets from January 1, 2015 to December 31, 2016 : Successor Exelon Generation ComEd PECO BGE PHI (f) Pepco DPL ACE Non-nuclear AROs at January 1, 2015 $ 346 $ 194 $ 104 $ 30 $ 18 $ — $ — $ — $ — Net (decrease) increase due to changes in, and timing of, estimated future cash flows (a) (10 ) (12 ) 6 (4 ) — — — — — Development projects (b) 10 10 — — — — — — — Accretion expense (c) 16 10 5 1 — — — — — Sale of generating assets (d) (2 ) (2 ) — — — — — — — Payments (5 ) (3 ) (2 ) — — — — — — Non-nuclear AROs at December 31, 2015 (e) 355 197 113 27 18 — — — — Merger with PHI (g) 8 1 — — — — — — — Net increase (decrease) due to changes in, and timing of, estimated future cash flows (a) 34 8 4 1 7 14 2 9 3 Development projects (b) 11 11 — — — — — — — Accretion expense (c) 18 10 7 1 — — — — — Sale of generating assets (d) (22 ) (22 ) — — — — — — — Payments (11 ) (6 ) (3 ) (1 ) (1 ) — — — — Non-nuclear AROs at December 31, 2016 (e) $ 393 $ 199 $ 121 $ 28 $ 24 $ 14 $ 2 $ 9 $ 3 Predecessor PHI (f) Non-nuclear AROs at January 1, 2015 $ 7 Accretion expense (c) 1 Non-nuclear AROs at December 31, 2015 $ 8 Non-nuclear AROs at March 23, 2016 $ 8 ________________________ (a) During the year ended December 31, 2016 , Generation recorded an increase of $1 million in Operating and maintenance expense. ComEd, PECO and BGE did not record any adjustments in Operating and maintenance expense for the year ended December 31, 2016 . During the year ended December 31, 2015 , Generation recorded a decrease of $(2) million in Operating and maintenance expense. ComEd, PECO and BGE did not record any adjustments in Operating and maintenance expense for the year ended December 31, 2015 . (b) Relates to new AROs recorded due to the construction of solar, wind and other non-nuclear generating sites. (c) For ComEd, PECO, and BGE, the majority of the accretion is recorded as an increase to a regulatory asset due to the associated regulatory treatment. (d) Reflects a reduction to the ARO resulting primarily from the sales of the New Boston generating site and Upstream business in 2016 and Schuylkill generating station in 2015. See Note 4 — Mergers, Acquisitions, and Dispositions for further information. (e) Excludes $1 million , $2 million and $3 million as the current portion of the ARO at December 31, 2016 for Generation, ComEd and BGE, respectively. Excludes $5 million , $2 million and $1 million as the current portion of the ARO at December 31, 2015 for Generation, ComEd and BGE, respectively. This is included in Other current liabilities on the Registrants' respective Consolidated Balance Sheets. (f) For PHI, the successor period includes activity for the period of March 24, 2016 through December 31, 2016. The PHI predecessor periods include activity for the year ended December 31, 2015 and the period January 1, 2016 through March 23, 2016. (g) Following the completion of the PHI merger on March 23, 2016, PHI's AROs related to its unregulated business interests were transferred to Exelon and Generation.

Retirement Benefits (All Regist

Retirement Benefits (All Registrants)	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Retirement Benefits (All Registrants)	(All Registrants) As of December 31, 2016 , Exelon sponsored defined benefit pension plans and other postretirement benefit plans for essentially all employees. Effective March 23, 2016 , Exelon became the sponsor of all of PHI's defined benefit pension and other postretirement benefit plans, and assumed PHI's benefit plan obligations and related assets. As a result, PHI's benefit plan net obligation and related regulatory assets were transferred to Exelon and remeasured at the merger date using current assumptions, including discount rates. The table below shows the pension and other postretirement benefit plans in which employees of each operating company participated at December 31, 2016 . Operating Company (e) Name of Plan: Generation ComEd PECO BGE BSC PHI Pepco DPL ACE Qualified Pension Plans: Exelon Corporation Retirement Program (a) X X X X X Exelon Corporation Cash Balance Pension Plan (a) X X X X X Exelon Corporation Pension Plan for Bargaining Unit Employees (a) X X X Exelon New England Union Employees Pension Plan (a) X Exelon Employee Pension Plan for Clinton, TMI and Oyster Creek (a) X X X X Pension Plan of Constellation Energy Group, Inc. (b) X X X X X Pension Plan of Constellation Energy Nuclear Group, LLC (c) X X X Nine Mile Point Pension Plan (c) X X Constellation Mystic Power, LLC Union Employees Pension Plan Including Plan A and Plan B (b) X Pepco Holdings LLC Retirement Plan (d) X X X X X Non-Qualified Pension Plans: Exelon Corporation Supplemental Pension Benefit Plan and 2000 Excess Benefit Plan (a) X X X X Exelon Corporation Supplemental Management Retirement Plan (a) X X X X X Constellation Energy Group, Inc. Senior Executive Supplemental Plan (b) X X X Constellation Energy Group, Inc. Supplemental Pension Plan (b) X X X Constellation Energy Group, Inc. Benefits Restoration Plan (b) X X X X Constellation Energy Nuclear Plan, LLC Executive Retirement Plan (c) X X Constellation Energy Nuclear Plan, LLC Benefits Restoration Plan (c) X X Baltimore Gas & Electric Company Executive Benefit Plan (b) X X X Baltimore Gas & Electric Company Manager Benefit Plan (b) X X X X Pepco Holdings LLC 2011 Supplemental Executive Retirement Plan (d) X X X X X Conectiv Supplemental Executive Retirement Plan (d) X X X X Pepco Holdings LLC Combined Executive Retirement Plan (d) X X X Atlantic City Electric Director Retirement Plan (d) X X Operating Company (e) Name of Plan: Generation ComEd PECO BGE BSC PHI Pepco DPL ACE Other Postretirement Benefit Plans: PECO Energy Company Retiree Medical Plan (a) X X X X X Exelon Corporation Health Care Program (a) X X X X X Exelon Corporation Employees’ Life Insurance Plan (a) X X X X X Exelon Corporation Health Reimbursement (a) X X X X X Constellation Energy Group, Inc. Retiree Medical Plan (b) X X X X X Constellation Energy Group, Inc. Retiree Dental Plan (b) X X X Constellation Energy Group, Inc. Employee Life Insurance Plan and Family Life Insurance Plan (b) X X X X X Constellation Mystic Power, LLC Post-Employment Medical Account Savings Plan (b) X Exelon New England Union Post-Employment Medical Savings Account Plan (a) X Retiree Medical Plan of Constellation Energy Nuclear Group LLC (c) X X X Retiree Dental Plan of Constellation Energy Nuclear Group LLC (c) X X X Nine Mile Point Nuclear Station, LLC Medical Care and Prescription Drug Plan for Retired Employees (c) X X Pepco Holdings LLC Welfare Plan for Retirees (d) X X X X X ______________________ (a) These plans are collectively referred to as the legacy Exelon plans. (b) These plans are collectively referred to as the legacy Constellation Energy Group (CEG) Plans. (c) These plans are collectively referred to as the legacy CENG plans. (d) These plans are collectively referred to as the legacy PHI plans. (e) Employees generally remain in their legacy benefit plans when transferring between operating companies. Exelon’s traditional and cash balance pension plans are intended to be tax-qualified defined benefit plans. Substantially all non-union employees and electing union employees hired on or after January 1, 2001 participate in cash balance pension plans. Effective January 1, 2009, substantially all newly-hired union-represented employees participate in cash balance pension plans. Exelon has elected that the trusts underlying these plans be treated as qualified trusts under the IRC. If certain conditions are met, Exelon can deduct payments made to the qualified trusts, subject to certain IRC limitations. Benefit Obligations, Plan Assets and Funded Status Exelon recognizes the overfunded or underfunded status of defined benefit pension and OPEB plans as an asset or liability on its balance sheet, with offsetting entries to AOCI and regulatory assets (liabilities), in accordance with the applicable authoritative guidance. The measurement date for the plans is December 31. During the first quarter of 2016 , Exelon received an updated valuation of its legacy Exelon, CEG and CENG pension and other postretirement benefit obligations to reflect actual census data as of January 1, 2016 . This valuation resulted in an increase to the pension obligation of $35 million and a decrease to the other postretirement benefit obligation of $8 million . Additionally, accumulated other comprehensive loss increased by approximately $2 million (after tax), regulatory assets increased by approximately $27 million , and regulatory liabilities increased by approximately $3 million . The legacy PHI pension and other postretirement benefit plans were initially remeasured on February 29, 2016 as a result of the short time between the merger close and the end of the first quarter of 2016, using current assumptions, including the discount rate. Exelon updated these amounts in the second quarter of 2016 to reflect assumptions at March 31, 2016 resulting in a $25 million reduction in the net obligation. The following tables provide a rollforward of the changes in the benefit obligations and plan assets for the most recent two years for all plans combined: Pension Benefits Other Postretirement Benefits Exelon 2016(b) 2015 2016(b) 2015 Change in benefit obligation: Net benefit obligation at beginning of year $ 17,753 $ 18,256 $ 3,938 $ 4,197 Service cost 354 326 107 119 Interest cost 830 710 185 167 Plan participants’ contributions — — 54 42 Actuarial (gain) loss 567 (582 ) (136 ) (341 ) Plan amendments (60 ) — — (23 ) Acquisitions/divestitures (a) 2,667 — 589 — Settlements — (34 ) — — Gross benefits paid (1,051 ) (923 ) (280 ) (223 ) Net benefit obligation at end of year $ 21,060 $ 17,753 $ 4,457 $ 3,938 Pension Benefits Other Postretirement Benefits Exelon 2016(b) 2015 2016(b) 2015 Change in plan assets: Fair value of net plan assets at beginning of year $ 14,347 $ 14,874 $ 2,293 $ 2,430 Actual return on plan assets 1,061 (32 ) 128 4 Employer contributions 347 462 50 40 Plan participants’ contributions — — 54 42 Gross benefits paid (1,051 ) (923 ) (280 ) (223 ) Acquisitions/divestitures (a) 2,087 — 333 — Settlements — (34 ) — — Fair value of net plan assets at end of year $ 16,791 $ 14,347 $ 2,578 $ 2,293 Predecessor Pension Benefits Other Postretirement Benefits PHI January 1, 2016 to March 23, 2016 2015 January 1, 2016 to March 23, 2016 2015 Change in benefit obligation: Net benefit obligation at beginning of the period $ 2,490 $ 2,638 $ 563 $ 632 Service cost 12 57 1 7 Interest cost 26 109 6 24 Actuarial (gain) loss (30 ) (151 ) (5 ) (61 ) Gross benefits paid (2 ) (163 ) (1 ) (39 ) Net benefit obligation at end of the period $ 2,496 $ 2,490 $ 564 $ 563 Predecessor Pension Benefits Other Postretirement Benefits PHI January 1, 2016 to March 23, 2016 2015 January 1, 2016 to March 23, 2016 2015 Change in plan assets: Fair value of net plan assets at beginning of the period $ 2,018 $ 2,236 $ 348 $ 367 Actual return on plan assets — (61 ) — 1 Employer and plan participant contributions 4 6 1 5 Gross benefits paid by plan (2 ) (163 ) (1 ) (25 ) Fair value of net plan assets at end of the period $ 2,020 $ 2,018 $ 348 $ 348 ____________________ (a) Effective March 23, 2016 , Exelon became the sponsor of PHI's defined benefit pension and other postretirement benefit plans. (b) 2016 amounts include PHI for the period of March 24, 2016 through December 31, 2016. Exelon and PHI present their benefit obligations and plan assets net on their balance sheet within the following line items: Pension Benefits Other Postretirement Benefits Exelon 2016(a) 2015 2016(a) 2015 Other current liabilities $ 21 $ 21 $ 31 $ 27 Pension obligations 4,248 3,385 — — Non-pension postretirement benefit obligations — — 1,848 1,618 Unfunded status (net benefit obligation less plan assets) $ 4,269 $ 3,406 $ 1,879 $ 1,645 Pension Benefits Other Predecessor Predecessor PHI 2015 2015 Other current liabilities $ 6 $ — Pension obligations 466 — Non-pension postretirement benefit obligations — 215 Unfunded status (net benefit obligation less plan assets) $ 472 $ 215 ____________________ (a) Effective March 23, 2016 , Exelon became the sponsor of PHI's defined benefit pension and other postretirement benefit plans, and assumed PHI's benefit plan obligations and related assets. The funded status of the pension and other postretirement benefit obligations refers to the difference between plan assets and estimated obligations of the plan. The funded status changes over time due to several factors, including contribution levels, assumed discount rates and actual returns on plan assets. The following tables provide the projected benefit obligations (PBO), accumulated benefit obligation (ABO), and fair value of plan assets for all pension plans with a PBO or ABO in excess of plan assets. PBO in excess of plan assets Predecessor Exelon PHI 2016 2015 2015 Projected benefit obligation $ 21,060 $ 17,753 $ 2,490 Fair value of net plan assets 16,791 14,347 2,018 ABO in excess of plan assets Predecessor Exelon PHI 2016 2015 2015 Projected benefit obligation $ 21,060 $ 17,753 $ 2,490 Accumulated benefit obligation 19,930 16,792 2,275 Fair value of net plan assets 16,791 14,347 2,018 On a PBO basis, the Exelon plans were funded at 80% and 81% at December 31, 2016 and December 31, 2015 , respectively, and the PHI plans were funded at 81% at December 31, 2015 . On an ABO basis, the Exelon plans were funded at 84% and 85% at December 31, 2016 and December 31, 2015 , respectively, and the PHI plans were funded at 89% at December 31, 2015 . The ABO differs from the PBO in that the ABO includes no assumption about future compensation levels. Components of Net Periodic Benefit Costs The majority of the 2016 pension benefit cost for the legacy Exelon, CEG and CENG plans is calculated using an expected long-term rate of return on plan assets of 7.00% and a discount rate of 4.29% . The majority of the 2016 other postretirement benefit cost for the legacy Exelon, CEG and CENG plans is calculated using an expected long-term rate of return on plan assets of 6.71% for funded plans and a discount rate of 4.29% . The majority of the 2016 pension benefit cost of the legacy PHI plans is calculated using an expected long-term rate of return on plan assets of 6.50% and a discount rate of 3.96% . The 2016 other postretirement benefit cost for the legacy PHI plan is calculated using an expected long-term rate of return on plan assets of 6.75% and a discount rate of 3.80% . A portion of the net periodic benefit cost for all pension and OPEB plans is capitalized within each of the Registrants' Consolidated Balance Sheets. The following tables present the components of Exelon’s net periodic benefit costs, prior to any capitalization, for the years ended December 31, 2016 , 2015 and 2014 and the components of PHI's predecessor net periodic benefit costs, prior to any capitalization, for the years ended December 31, 2015 and 2014 , and the period January 1, 2016 to March 23, 2016 . Pension Benefits Other Postretirement Benefits Exelon 2016(a) 2015 2014 2016(a) 2015 2014 Components of net periodic benefit cost: Service cost $ 354 $ 326 $ 293 $ 107 $ 119 $ 117 Interest cost 830 710 749 185 167 186 Expected return on assets (1,141 ) (1,026 ) (994 ) (162 ) (151 ) (154 ) Amortization of: Prior service cost (credit) 14 13 14 (185 ) (174 ) (122 ) Actuarial loss 554 571 420 63 80 50 Settlement and other charges (b) 2 2 2 — — — Net periodic benefit cost $ 613 $ 596 $ 484 $ 8 $ 41 $ 77 _______________________ (a) 2016 amounts include PHI for the period of March 24, 2016 through December 31, 2016. (b) 2016 amount includes an additional termination benefit for PHI. Predecessor Pension Benefits Other PHI January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 Components of net periodic benefit cost: Service cost $ 12 $ 57 $ 44 $ 1 $ 7 $ 7 Interest cost 26 109 109 6 24 26 Expected return on assets (30 ) (140 ) (141 ) (5 ) (22 ) (24 ) Amortization of: Prior service cost (credit) — 2 2 (3 ) (13 ) (13 ) Actuarial loss 14 65 45 2 8 3 Net periodic benefit cost $ 22 $ 93 $ 59 $ 1 $ 4 $ (1 ) Components of AOCI and Regulatory Assets Under the authoritative guidance for regulatory accounting, a portion of current year actuarial gains and losses and prior service costs (credits) is capitalized within Exelon’s Consolidated Balance Sheets to reflect the expected regulatory recovery of these amounts, which would otherwise be recorded to AOCI. The following tables provide the components of AOCI and regulatory assets (liabilities) for the years ended December 31, 2016 , 2015 and 2014 for all plans combined and the components of PHI's predecessor AOCI and regulatory assets (liabilities) for the years ended December 31, 2015 and 2014 , and the period January 1, 2016 to March 23, 2016 . Pension Benefits Other Postretirement Benefits Exelon 2016(a) 2015 2014 2016(a) 2015 2014 Changes in plan assets and benefit obligations recognized in AOCI and regulatory assets (liabilities): Current year actuarial loss (gain) $ 644 $ 476 $ 1,639 $ (101 ) $ (194 ) $ 561 Amortization of actuarial loss (554 ) (571 ) (420 ) (63 ) (80 ) (50 ) Current year prior service (credit) cost (60 ) — — — (23 ) (1,012 ) Amortization of prior service (cost) credit (14 ) (13 ) (14 ) 185 174 122 Settlements — (2 ) (2 ) — — — Acquisitions 994 — — 94 — — Total recognized in AOCI and regulatory assets (liabilities) $ 1,010 $ (110 ) $ 1,203 $ 115 $ (123 ) $ (379 ) Total recognized in AOCI $ 51 $ (64 ) $ 788 $ 20 $ (63 ) $ (162 ) Total recognized in regulatory assets (liabilities) $ 959 $ (46 ) $ 415 $ 95 $ (60 ) $ (217 ) Predecessor Pension Benefits Other PHI January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 Changes in plan assets and benefit Current year actuarial loss (gain) $ — $ 50 $ 276 $ — $ (39 ) $ 62 Amortization of actuarial loss (14 ) (65 ) (45 ) (2 ) (8 ) (3 ) Amortization of prior service (cost) credit — (2 ) (2 ) 3 13 13 Total recognized in AOCI and regulatory assets (liabilities) $ (14 ) $ (17 ) $ 229 $ 1 $ (34 ) $ 72 Total recognized in AOCI $ (1 ) $ (11 ) $ 17 $ — $ — $ — Total recognized in regulatory assets (liabilities) $ (13 ) $ (6 ) $ 212 $ 1 $ (34 ) $ 72 _______________________ (a) 2016 amounts include PHI for the period of March 24, 2016 through December 31, 2016. The following table provides the components of gross accumulated other comprehensive loss and regulatory assets (liabilities) that have not been recognized as components of periodic benefit cost at December 31, 2016 and 2015 , respectively, for all plans combined: Predecessor Predecessor Exelon PHI Exelon PHI Pension Benefits Other Postretirement Benefits 2016(a) 2015 2015 2016(a) 2015 2015 Prior service cost (credit) $ (31 ) $ 36 $ 6 $ (710 ) $ (812 ) $ (88 ) Actuarial loss 8,387 7,310 910 724 711 128 Total (a) $ 8,356 $ 7,346 $ 916 $ 14 $ (101 ) $ 40 Total included in AOCI $ 4,297 $ 4,246 $ 46 $ (42 ) $ (63 ) $ — Total included in regulatory assets (liabilities) $ 4,059 $ 3,100 $ 870 $ 56 $ (38 ) $ 40 ______________________ (a) Effective March 23, 2016 , Exelon became the sponsor of PHI's defined benefit pension and other postretirement benefit plans, and assumed PHI's benefit plan obligations and related assets. The following table provides the impact to Exelon’s AOCI and regulatory assets (liabilities) at December 31, 2016 as a result of the components of periodic benefit costs that are expected to be amortized in 2017 . These estimates are subject to the completion of an actuarial valuation of Exelon’s pension and other postretirement benefit obligations, which will reflect actual census data as of January 1, 2017 and actual claims activity as of December 31, 2016 . The valuation is expected to be completed in the first quarter of 2017 for the majority of the benefit plans. Pension Benefits Other Postretirement Benefits Prior service cost (credit) $ 1 $ (188 ) Actuarial loss 605 55 Total (a) $ 606 $ (133 ) ___________________ (a) Of the $606 million related to pension benefits at December 31, 2016 , $297 million and $309 million are expected to be amortized from AOCI and regulatory assets in 2017 , respectively. Of the $(133) million related to other postretirement benefits at December 31, 2016 , $(70) million and $(63) million are expected to be amortized from AOCI and regulatory assets (liabilities) in 2017 , respectively. Assumptions The measurement of the plan obligations and costs of providing benefits under Exelon’s defined benefit and other postretirement plans involves various factors, including the development of valuation assumptions and inputs and accounting policy elections. The measurement of benefit obligations and costs is impacted by several assumptions and inputs, including the discount rate applied to benefit obligations, the long-term EROA, Exelon’s expected level of contributions to the plans, the long-term expected investment rate credited to employees participating in cash balance plans and the anticipated rate of increase of health care costs. Additionally, assumptions related to plan participants include the incidence of mortality, the expected remaining service period, the level of compensation and rate of compensation increases, employee age and length of service, among other factors. When developing the required assumptions, Exelon considers historical information as well as future expectations. Expected Rate of Return. In selecting the EROA, Exelon considers historical economic indicators (including inflation and GDP growth) that impact asset returns, as well as expectations regarding future long-term capital market performance, weighted by Exelon’s target asset class allocations. Mortality. For the December 31, 2014 actuarial valuation, Exelon changed its assumption of mortality to reflect more recent expectations of future improvements in life expectancy. The change was supported through completion of an experience study and supplemental analyses performed by Exelon's actuaries. The change in assumption resulted in increases of $361 million and $117 million in the pension and other postretirement benefits obligations as of December 31, 2014, respectively. There were no changes to the mortality assumption in 2015 or 2016 . The following assumptions were used to determine the benefit obligations for the plans at December 31, 2016 , 2015 and 2014 . Assumptions used to determine year-end benefit obligations are the assumptions used to estimate the subsequent year’s net periodic benefit costs. Pension Benefits Other Postretirement Benefits Exelon 2016 2015 2014 2016 2015 2014 Discount rate 4.04 % (a) 4.29 % (b) 3.94 % (c) 4.04 % (a) 4.29 % (b) 3.92 % (c) Rate of compensation increase (d) (d) (d) (d) (d) (d) Mortality table RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) Health care cost trend on covered charges N/A N/A N/A 5.50% with ultimate trend of 5.00% in 2017 5.50% 6.00% decreasing to ultimate trend of 5.00% in 2017 Predecessor Predecessor Pension Benefits Other Postretirement Benefits PHI January 1, 2016 to March 23, 2016 (e) 2015 2014 January 1, 2016 to March 23, 2016 (e) 2015 2014 Discount rate 4.65%/4.55% (f) 4.20 % 4.55 % 4.15 % Rate of compensation 5.00 % 5.00 % 5.00 % 5.00 % Mortality table RP-2014 table with improvement scale MP-2015 RP-2014 table with improvement scale MP-2014 RP-2014 table with improvement scale MP-2015 RP-2014 table with improvement scale MP-2014 Health care cost trend on covered charges N/A N/A 6.33% pre-65 and 5.40% post-65 6.67% pre-65 and 5.50% post-65 _____________________________ (a) The discount rates above represent the blended rates used to determine the majority of Exelon’s pension and other postretirement benefits obligations as of December 31, 2016. Certain benefit plans used individual rates ranging from 3.66% - 4.11% and 4.00% - 4.17% for pension and other postretirement plans, respectively. (b) The discount rates above represent the blended rates used to determine the majority of Exelon’s pension and other postretirement benefits obligations as of December 31, 2015. Certain benefit plans used individual rates ranging from 3.68% - 4.14% and 4.32% - 4.43% for pension and other postretirement plans, respectively. (c) The discount rates above represent the blended rates used to determine the majority of Exelon’s pension and other postretirement benefits obligations as of December 31, 2014. Certain benefit plans used individual rates ranging from 3.29% - 3.82% and 3.99% - 4.06% for pension and other postretirement plans, respectively. (d) The legacy Exelon, CEG and CENG pension and other postretirement plans used a rate of compensation increase of 3.25% through 2019 and 3.75% thereafter, while the legacy PHI pension and other postretirement plans used a weighted-average rate of compensation increase of 5% for all periods. (e) Obligation was not remeasured during this period. (f) The discount rate for the qualified and nonqualified pension plans was 4.65% and 4.55%, respectively. The following assumptions were used to determine the net periodic benefit costs for the plans for the years ended December 31, 2016 , 2015 and 2014 , as well as for the PHI predecessor period January 1, 2016 to March 23, 2016 : Pension Benefits Other Postretirement Benefits Exelon 2016 2015 2014 2016 2015 2014 Discount rate 4.29 % (a) 3.94 % (b) 4.80 % (c) 4.29 % (a) 3.92 % (b) 4.90 % (c) Expected return on plan assets 7.00 % (d) 7.00 % (d) 7.00 % (d) 6.71 % (d) 6.50 % (d) 6.59 % (d) Rate of compensation increase (e) (e) Mortality table RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table with Scale AA improvements RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table with Scale AA improvements Health care cost trend on covered charges N/A N/A N/A 5.50% decreasing to ultimate trend of 5.00% in 2017 6.00% 6.00% decreasing to ultimate trend of 5.00% in 2017 Predecessor Predecessor Pension Benefits Other Postretirement Benefits PHI January 1, 2016 to March 23, 2016 2015 2014 January 1, 2016 to March 23, 2016 2015 2014 Discount rate 4.65%/4.55% (h) 4.20 % 5.05 % 4.55 % 4.15 % 5.00 % Expected return on plan assets (g) 6.50 % 6.50 % 7.00 % 6.75 % 6.75 % 7.25 % Rate of compensation 5.00 % 5.00 % 5.00 % 5.00 % 5.00 % 5.00 % Mortality table RP-2014 table with improvement scale MP-2015 RP-2014 table with improvement scale MP-2014 2014 Mortality tables prescribed by the Pension Protection Act of 2006 RP-2014 table with improvement scale MP-2015 RP-2014 table with improvement scale MP-2014 2014 Mortality tables prescribed by the Pension Protection Act of 2006 Health care cost trend on covered charges N/A N/A N/A 6.33% pre-65 and 5.40% post-65 6.67% pre-65 and 5.50% post-65 7.00% pre-65 and 5.60% post-65 ___________________________ (a) The discount rates above represent the blended rates used to establish the majority of Exelon’s pension and other postretirement benefits costs for the year ended December 31, 2016 . Certain benefit plans used individual rates ranging from 3.68% - 4.14% and 4.32% - 4.43% for pension and other postretirement plans, respectively. (b) The discount rates above represent the blended rates used to establish the majority of Exelon's pension and other postretirement benefits costs for the year ended December 31, 2015 . Certain benefit plans used individual rates ranging from 3.29% - 3.82% and 3.99% - 4.06% for pension and other postretirement plans, respectively. (c) The discount rates above represent the blended rates used to establish the majority of Exelon’s pension and other postretirement benefits costs for the year ended December 31, 2014 . Certain of the other postretirement benefit plans were remeasured as of April 30, 2014 using an expected long-term rate of return on plan assets of 6.59% and a discount rate of 4.30% . Costs for the year ended December 31, 2014 reflect the impact of this remeasurement. On April 1, 2014, Generation assumed operational control of CENG’s nuclear fleet. As a result, Exelon became the sponsor of CENG’s legacy pension and OPEB plans effective July 14, 2014; discount rates for those plans, impacting 2014 costs, ranged from 3.60% - 4.30% and 4.09% - 4.55% , respectively. See Note 5 - Investment in Constellation Energy Nuclear Group, LLC for further information. (d) Not applicable to pension and other postretirement benefit plans that do not have plan assets. (e) 3.25% through 2019 and 3.75% thereafter. (f) 3.25% through 2018 and 3.75% thereafter. (g) Expected return on other postretirement benefit plan assets is pre-tax. (h) The discount rate for the qualified and nonqualified pension plans was 4.65% and 4.55%, respectively. Assumed health care cost trend rates impact the other postretirement benefit plan costs reported for Exelon's participant populations with plan designs that do not have a cap on cost growth. A one percentage point change in assumed health care cost trend rates would have the following effects: Effect of a one percentage point increase in assumed health care cost trend: on 2016 total service and interest cost components $ 9 on postretirement benefit obligation at December 31, 2016 105 Effect of a one percentage point decrease in assumed health care cost trend: on 2016 total service and interest cost components (8 ) on postretirement benefit obligation at December 31, 2016 (95 ) Contributions The following tables provide contributions to the pension and other postretirement benefit plans: Pension Benefits Other Postretirement Benefits 2016 (a) 2015 (a) 2014 (a) 2016 2015 2014 Exelon $ 347 $ 462 $ 332 $ 50 $ 40 $ 291 Generation 140 231 173 12 14 124 ComEd 33 143 122 5 7 125 PECO 30 40 11 — — 5 BGE 31 1 — 18 16 17 BSC (b) 39 47 26 3 3 20 Pepco 24 — — 8 2 1 DPL 22 — — — — — ACE 15 — — 2 3 3 PHISCO (c) 17 — — 2 — — Pension Benefits Other Postretirement Benefits Successor Predecessor Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 PHI $ 74 $ 4 $ — $ — $ 12 $ — $ 5 $ 4 _________________________ (a) Exelon's and Generation's pension contributions include $25 million , $36 million and $43 million related to the legacy CENG plans that was funded by CENG as provided in an Employee Matters Agreement (EMA) between Exelon and CENG for the years ended December 31, 2016 , 2015 and 2014 , respectively. (b) Includes $6 million , $5 million , and $9 million of pension contributions funded by Exelon Corporate, for the years ended December 31, 2016 , 2015 , and 2014 , respectively. (c) PHISCO’s pension contributions for the year ended December 31, 2016 include $4 million of contributions made prior to the closing of Exelon’s merger with PHI on March 23, 2016 . Management considers various factors when making pension funding decisions, including actuarially determined minimum contribution requirements under ERISA, contributions required to avoid benefit restrictions and at-risk status as defined by the Pension Protection Act of 2006 (the Act), management of the pension obligation and regulatory implications. The Act requires the attainment of certain funding levels to avoid benefit restrictions (such as an inability to pay lump sums or to accrue benefits prospectively), and at-risk status (which triggers higher minimum contribution requirements and participant notification). Additionally, the projected contribution reflects a funding strategy for the legacy Exelon, CEG and CENG plans of contributing the greater of $250 million until the qualified plans are fully funded on an ABO basis, and the minimum amounts under ERISA to avoid benefit restrictions and at-risk status. This level funding strategy helps minimize volatility of future period required pension contributions. Contributions to the PHI qualified pension plan are $60 million . The following table provides all registrants' planned contributions to the qualified pension plans, planned benefit payments to non-qualified pension plans, and planned contributions to other postretirement plans in 2017: Qualified Pension Plans (a) Non-Qualified Pension Plans (b) Other Postretirement Benefits (c) Exelon $ 310 $ 23 $ 44 Generation 127 6 12 ComEd 33 1 2 PECO 23 1 — BGE 38 2 16 PHI 60 8 12 Pepco 60 1 10 DPL — — — ACE — — — _____________________ (a) Exelon's and Generation's expected qualified pension plan contributions above include $21 million related to the legacy CENG plans that will be funded by CENG as provided in an EMA between Exelon and CENG. (b) Unlike the qualified pension plans, Exelon’s non-qualified pension plans are not funded. (c) Unlike the qualified pension plans, other postretirement plans are not subject to statutory minimum contribution requirements. OPEB funding generally follows accounting costs however, Exelon’s management has historically considered several factors in determining the level of contributions to its other postretirement benefit plans, including liabilities management, levels of benefit claims paid and regulatory implications (amounts deemed prudent to meet regulatory expectations and best assure continued rate recovery). These amounts include benefit payments related to unfunded plans. Estimated Future Benefit Payments Estimated future benefit payments to participants in all of the pension plans and postretirement benefit plans at December 31, 2016 were: Pension Benefits Other Postretirement Benefits 2017 $ 1,360 $ 244 2018 1,170 250 2019 1,191 256 2020 1,223 263 2021 1,275 272 2022 through 2026 6,791 1,456 Total estimated future benefit payments through 2026 $ 13,010 $ 2,741 Allocation to Exelon Subsidiaries All registrants account for their participation in Exelon’s pension and other postretirement benefit plans by applying multi-employer accounting. Employee-related assets and liabilities, including both pension and postretirement liabilities, for the legacy Exelon plans were allocated by Exelon to its subsidiaries based on the number of active employees as of January 1, 2001 as part of Exelon’s corporate restructuring. The obligation for Generation, ComEd and PECO reflects the initial allocation and the cumulative costs incurred and contributions made since January 1, 2001. Historically, Exelon has allocated the components of pension and other postretirement costs to the subsidiaries in the legacy Exelon plans based upon several factors, including the measures of active employee participation in each plan. Pension and other postretirement benefit contributions were allocated to legacy Exelon subsidiaries in proportion to a

Severance (All Registrants)

Severance (All Registrants)	12 Months Ended
	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Severance (All Registrants)	(All Registrants) The Registrants have an ongoing severance plan under which, in general, the longer an employee worked prior to termination the greater the amount of severance benefits. The Registrants record a liability and expense or regulatory asset for severance once terminations are probable of occurrence and the related severance benefits can be reasonably estimated. For severance benefits that are incremental to its ongoing severance plan (“one-time termination benefits”), the Registrants measure the obligation and record the expense at fair value at the communication date if there are no future service requirements, or, if future service is required to receive the termination benefit, ratably over the required service period. Ongoing Severance Plans The Registrants provide severance and health and welfare benefits under Exelon’s ongoing severance benefit plans to terminated employees in the normal course of business. These benefits are accrued for when the benefits are considered probable and can be reasonably estimated. For the years ended December 31, 2016 and 2015 , the Registrants recorded the following severance costs associated with ongoing severance benefits within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income: Exelon Generation (a) ComEd (a) PECO (a) BGE (a) Year ended December 31, 2016 $ 19 $ 13 $ 3 $ 1 $ 1 2015 18 15 2 — 1 Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 PHI (a) Severance Benefits $ 1 $ — $ — _______ (a) The amounts above for Generation, ComEd, PECO, BGE and PHI include immaterial amounts billed by BSC for the years ended December 31, 2016 and 2015 . Early Plant Retirement-Related Severance On December 7, 2016 the Future Energy Jobs Bill was signed into law by the Governor of Illinois and included a ZES. With the passage of the IL ZES, Generation reversed its decision to permanently cease generation operations at the Clinton and Quad Cities nuclear generating plants and expects the plants to continue operation for at least another 10 years. As a result, Exelon and Generation reversed the associated severance benefit costs of $ 44 million in December 2016 which were previously recorded for expected employee severances. Cost Management Program-Related Severance In August 2015, Exelon announced a cost management program focused on cost savings at BSC and Generation, including the elimination of approximately 500 positions. These actions are in response to the continuing economic challenges confronting all parts of Exelon’s business and industry, necessitating continued focus on cost management through enhanced efficiency and productivity. Exelon expects that approximately 250 corporate support positions in BSC and approximately 250 positions located throughout Generation will be eliminated. The final amount of the severance charges related to the cost management program will ultimately depend on the specific employees severed. For the year ended December 31, 2016 , the Registrants recorded the following severance costs related to the cost management program within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income, pursuant to the authoritative guidance for ongoing severance plans: Exelon Generation ComEd PECO BGE Severance benefits (a) $ 23 $ 18 $ 3 $ 1 $ 1 _______ (a) The amounts above for Generation, ComEd, PECO and BGE include $7 million , $3 million , $1 million , and $1 million , respectively, for amounts billed by BSC through intercompany allocations for the year ended December 31, 2016 . Severance Costs Related to the PHI Merger Upon closing the PHI Merger, Exelon recorded a severance accrual for the anticipated employee position reductions as a result of the post-merger integration. Cash payments under the plan began in May 2016 and will continue through 2020. For the year ended December 31, 2016 , the Registrants recorded the following severance costs associated with the identified job reductions within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income, pursuant to the authoritative guidance for ongoing severance plans: Successor Exelon Generation ComEd PECO BGE PHI Pepco (b) DPL (c) ACE Severance benefits (a) $ 57 $ 9 $ 2 $ 1 $ 1 $ 44 $ 21 $ 13 $ 10 ______________ (a) The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $8 million , $2 million , $1 million , $1 million , $20 million , $12 million and $10 million , respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the year ended December 31, 2016 . (b) Pepco established a regulatory asset of $11 million as of December 31, 2016 , primarily for severance benefit costs related to the PHI merger. (c) DPL established a regulatory asset of $4 million as of December 31, 2016 , primarily for severance benefit costs related to the PHI merger. Severance Liability Amounts included in the table below represent the severance liability recorded for employees of each Registrant and exclude amounts included at Exelon and billed through intercompany allocations: Successor Severance Liability Exelon Generation ComEd PECO BGE PHI (b) Pepco DPL ACE Balance at December 31, 2014 $ 50 $ 34 $ 2 $ — $ 2 $ — $ 1 $ — $ — Severance charges 16 10 2 — — — — — — Payments (31 ) (21 ) (1 ) — (1 ) — (1 ) — — Balance at December 31, 2015 $ 35 $ 23 $ 3 $ — $ 1 $ — $ — $ — $ — Severance charges (a) 99 22 2 — — 56 1 1 — Payments (46 ) (9 ) (2 ) — (1 ) (27 ) (1 ) (1 ) — Balance at December 31, 2016 $ 88 $ 36 $ 3 $ — $ — $ 29 $ — $ — $ — Predecessor Severance Liability PHI (b) Balance at December 31, 2014 $ 3 Severance charges — Payments (3 ) Balance at December 31, 2015 $ — ______________ (a) Includes salary continuance and health and welfare severance benefits. Amounts primarily represent benefits provided for the PHI post-merger integration and the cost management program. (b) For PHI, the successor period includes activity for the period from March 24, 2016 through December 31, 2016 . The PHI predecessor periods include activity for the year ended December 31, 2015 and the period January 1, 2016 through March 23, 2016 . There was no activity in the 2016 PHI predecessor period.

Shareholder Equity (All Registr

Shareholder Equity (All Registrants)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Stockholders' Equity Note Disclosure [Text Block]	20 . Shareholders' Equity (Exelon, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE) The following table presents common stock authorized and outstanding as of December 31, 2016 and 2015 : December 31, 2016 2015 Par Value Shares Authorized Shares Outstanding Common Stock Exelon no par value 2,000,000,000 924,035,059 919,924,742 ComEd $ 12.50 250,000,000 127,017,157 127,016,973 PECO no par value 500,000,000 170,478,507 170,478,507 BGE no par value 175,000,000 1,000 1,000 PHI Predecessor $ 0.01 400,000,000 n/a 254,289,261 Pepco $ 0.01 200,000,000 100 100 DPL $ 2.25 1,000 1,000 1,000 ACE $ 3.00 25,000,000 8,546,017 8,546,017 ComEd had 72,859 and 73,434 warrants outstanding to purchase ComEd common stock at December 31, 2016 and 2015 , respectively. The warrants entitle the holders to convert such warrants into common stock of ComEd at a conversion rate of one share of common stock for three warrants. At December 31, 2016 and 2015 , 24,286 and 24,478 shares of common stock, respectively, were reserved for the conversion of warrants. Equity Securities Offering In June 2014, Exelon marketed an equity offering of 57.5 million shares of its common stock at a public offering price of $ 35 per share. In connection with such offering, Exelon entered into forward sale agreements with two counterparties. In July 2015, Exelon settled the forward sale agreement by the issuance of 57.5 million shares of Exelon common stock. Exelon received net cash proceeds of $1.87 billion , which was calculated based on a forward price of $32.48 per share as specified in the forward sale agreements. The net proceeds were used to fund the merger with PHI and related costs and expenses, and for general corporate purposes. The forward sale agreements are classified as equity transactions. As a result, no amounts were recorded in the consolidated financial statements until the July 2015 settlement of the forward sale agreements. However, prior to the July 2015 settlement, incremental shares, if any, were included within the calculation of diluted EPS using the treasury stock method. Concurrent with the forward equity transaction, Exelon also issued $1.15 billion of junior subordinated notes in the form of 23 million equity units. See Note 14 — Debt and Credit Agreements for further information on the equity units. Share Repurchases Share Repurchase Programs . There currently is no Exelon Board of Director authority to repurchase shares. Any previous shares repurchased are held as treasury shares, at cost, unless cancelled or reissued at the discretion of Exelon’s management. Under the previous share repurchase programs, 35 million shares of common stock are held as treasury stock with a cost of $2.3 billion at December 31, 2016 . During 2016 , 2015 and 2014 , Exelon had no common stock repurchases. Preferred and Preference Securities of Subsidiaries At December 31, 2016 and 2015 , Exelon was authorized to issue up to 100,000,000 shares of preferred securities, none of which were outstanding. At December 31, 2016 and 2015 , ComEd prior preferred securities and ComEd cumulative preference securities consisted of 850,000 shares and 6,810,451 shares authorized, respectively, none of which were outstanding. On July 3, 2016, BGE redeemed all 400,000 shares of its outstanding 7.125% Cumulative Preference Stock, 1993 Series and all 600,000 shares of its outstanding 6.990% Cumulative Preference Stock, 1995 Series for $100 million , plus accrued and unpaid dividends. On September 18, 2016, BGE redeemed the remaining 500,000 shares of its outstanding 6.970% Cumulative Preference Stock, 1993 Series and the remaining 400,000 shares of its outstanding 6.700% Cumulative Preference Stock, 1993 Series for $90 million , plus accrued and unpaid dividends. At December 31, 2016 and 2015 , BGE cumulative preference stock, $100 par value, consisted of 6,500,000 shares authorized and the outstanding amounts set forth in the table below. Shares of BGE preference stock have no voting power except for the following: • The preference stock has one vote per share on any charter amendment that i) with regards to either dividends or distribution of assets, would create or authorize any shares of stock ranking prior to or on a parity with the preference stock or ii) substantially adversely affect the contract rights, as expressly set forth in BGE’s charter, of the preference stock. Each such amendment would require the affirmative vote of two-thirds of all the shares of preference stock outstanding; and • Whenever BGE fails to pay full dividends on the preference stock and such failure continues for one year, the preference stock shall have one vote per share on all matters, until and unless such dividends shall have been paid in full. Upon liquidation, the holders of the preference stock of each series outstanding are entitled to receive the par amount of their shares and an amount equal to the unpaid accrued dividends. December 31, Redemption (a) 2016 2015 2016 2015 Shares Outstanding Dollar Amount Series (without mandatory redemption) 7.125%, 1993 Series $ 100.00 — 400,000 $ — $ 40 6.97%, 1993 Series 100.00 — 500,000 — 50 6.70%, 1993 Series 100.00 — 400,000 — 40 6.99%, 1995 Series 100.00 — 600,000 — 60 Total preference stock — 1,900,000 $ — $ 190 ______________________ (a) Redeemable, at the option of BGE, at the indicated dollar amounts per share, plus accrued and unpaid dividends.

Stock-Based Compensation Plans

Stock-Based Compensation Plans (All Registrants)	12 Months Ended
	Dec. 31, 2016
Common Stock [Abstract]
Stock-Based Compensation Plans	Stock-Based Compensation Plans (All Registrants) Stock-Based Compensation Plans Exelon grants stock-based awards through its LTIP, which primarily includes stock options, restricted stock units and performance share awards. At December 31, 2016 , there were approximately 14 million shares authorized for issuance under the LTIP. For the years ended December 31, 2016 , 2015 and 2014 , exercised and distributed stock-based awards were primarily issued from authorized but unissued common stock shares. Beginning in 2014, ComEd, PECO and BGE grant cash awards. The following tables do not include expense related to these plans as they are not considered stock-based compensation plans under the applicable accounting guidance . In connection with the acquisition of PHI in March 2016, PHI’s unvested time-based restricted stock units and performance-based restricted stock units issued prior to April 29, 2014 were immediately vested and paid in cash upon the close of the merger. PHI’s remaining unvested time-based restricted stock units as of the close of the merger were cancelled. There were no remaining unvested performance-based restricted stock units as of the close of the merger. The following tables present the stock-based compensation expense included in Exelon's and PHI’s Consolidated Statements of Operations and Comprehensive Income for the years ended December 31, 2016 , 2015 and 2014 , as well as for the PHI predecessor period January 1, 2016 to March 23, 2016 : Exelon Year Ended December 31, Components of Stock-Based Compensation Expense 2016(a) 2015 2014 Performance share awards $ 93 $ 41 $ 59 Restricted stock units 75 71 61 Stock options — 1 2 Other stock-based awards 7 6 5 Total stock-based compensation expense included in operating and maintenance expense 175 119 127 Income tax benefit (68 ) (46 ) (47 ) Total after-tax stock-based compensation expense $ 107 $ 73 $ 80 ____________________ (a) 2016 amounts include expense related to stock-based compensation granted to eligible PHI employees since the merger date of March 23, 2016 . PHI Predecessor January 1 to March 23, Years Ended December 31, Components of Stock-Based Compensation Expense 2016 2015 2014 Time-based restricted stock units $ 2 $ 7 $ 5 Performance-based restricted stock units 1 5 8 Time-based restricted stock awards — 1 5 Total stock-based compensation expense included in operating and maintenance expense 3 13 18 Income tax benefit (1 ) (5 ) (7 ) Total after-tax stock-based compensation expense $ 2 $ 8 $ 11 The following tables present the Registrants' stock-based compensation expense (pre-tax) for the years ended December 31, 2016 , 2015 and 2014 , as well as for the PHI predecessor period January 1, 2016 to March 23, 2016 : Years Ended December 31, Subsidiaries 2016 2015 2014 Exelon $ 175 $ 119 $ 127 Generation 78 64 52 ComEd 8 6 7 PECO 3 3 3 BGE 1 3 5 BSC (a) 81 43 60 PHI (a)(b) 7 13 18 Successor Predecessor March 24 to January 1 to Years Ended 2016 2016 2015 2014 PHI $ 4 $ 3 $ 13 $ 18 ____________________ (a) These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO, BGE or PHI amounts above. (b) Pepco's, DPL's and ACE's stock-based compensation expense for the year ended December 31, 2016 and for the period January 1, 2016 through March 23, 2016 was not material. PHI's stock-based compensation expense for the year ended December 31, 2016 includes $3 million of costs incurred prior to the closing of Exelon’s merger with PHI on March 23, 2016 . There were no significant stock-based compensation costs capitalized during the years ended December 31, 2016 , 2015 and 2014 for Exelon or PHI, or for PHI during the predecessor period January 1, 2016 to March 23, 2016 . Exelon and PHI receive a tax deduction based on the intrinsic value of the award on the exercise date for stock options and the distribution date for performance share awards and restricted stock units. For each award, throughout the requisite service period, Exelon and PHI recognize the tax benefit related to compensation costs. The following tables present information regarding Exelon’s and PHI's tax benefits for the years ended December 31, 2016 , 2015 and 2014 and PHI's predecessor period January 1, 2016 to March 23, 2016 : Exelon Years Ended December 31, 2016 2015 2014 Realized tax benefit when exercised/distributed: Restricted stock units $ 27 $ 30 $ 17 Performance share awards 18 18 11 PHI Predecessor January 1 to Years Ended December 31, 2016 2015 2014 Realized tax benefit when exercised/distributed: Time-based restricted stock units $ — $ 2 $ 3 Performance-based restricted stock units — 5 4 Time-based restricted stock awards — — 1 Stock Options Non-qualified stock options to purchase shares of Exelon’s common stock were granted under the LTIP through 2012. Due to changes in the LTIP, there were no stock options granted in 2014, 2015 or 2016. For all stock options granted through 2012, the exercise price of the stock options is equal to the fair market value of the underlying stock on the date of option grant. The vesting period of stock options is generally four years. As of December 31, 2016 all stock options are fully vested. All stock options expire ten years from the date of grant. The value of stock options at the date of grant is expensed over the requisite service period using the straight-line method. The requisite service period for stock options is generally four years . However, certain stock options become fully vested upon the employee reaching retirement-eligibility. The value of the stock options granted to retirement-eligible employees is either recognized immediately upon the date of grant or through the date at which the employee reaches retirement eligibility. The following table presents information with respect to stock option activity for the year ended December 31, 2016 : Shares Weighted Average Exercise Price (per share) Weighted Average Remaining Contractual Life (years) Aggregate Intrinsic Value Balance of shares outstanding at December 31, 2015 15,572,757 $ 46.68 Options exercised (840,672 ) 22.12 Options forfeited — — Options expired (2,200,494 ) 58.60 Balance of shares outstanding at December 31, 2016 12,531,591 $ 46.23 3.50 $ 13 Exercisable at December 31, 2016 (a) 12,531,591 $ 46.23 3.50 $ 13 ____________________ (a) Includes stock options issued to retirement eligible employees. The following table summarizes additional information regarding stock options exercised for the years ended December 31, 2016 , 2015 and 2014 : Years Ended December 31, 2016 2015 2014 Intrinsic value (a) $ 11 $ — $ 3 Cash received for exercise price 19 — 7 ______________________ (a) The difference between the market value on the date of exercise and the option exercise price. The following table summarizes Exelon’s nonvested stock option activity for the year ended December 31, 2016 : Shares Weighted Average Exercise Price (per share) Nonvested at December 31, 2015 (a) 82,250 $ 39.81 Vested (82,250 ) 39.81 Nonvested at December 31, 2016 (a) — $ — _____________________ (a) Excludes 279,000 of stock options issued to retirement-eligible employees as of December 31, 2015 as they are fully vested. As of December 31, 2016 , all stock options are fully vested. At December 31, 2016 , there was no unrecognized compensation costs related to nonvested stock options. Restricted Stock Units Restricted stock units are granted under the LTIP with the majority being settled in a specific number of shares of common stock after the service condition has been met. The corresponding cost of services is measured based on the grant date fair value of the restricted stock unit issued. The value of the restricted stock units is expensed over the requisite service period using the straight-line method. The requisite service period for restricted stock units is generally three to five years . However, certain restricted stock unit awards become fully vested upon the employee reaching retirement-eligibility. The value of the restricted stock units granted to retirement-eligible employees is either recognized immediately upon the date of grant or through the date at which the employee reaches retirement eligibility. Exelon uses historical data to estimate employee forfeitures, which are compared to actual forfeitures on a quarterly basis and adjusted as necessary. The following tables summarize Exelon’s and PHI's nonvested restricted stock unit activity for the year ended December 31, 2016 and PHI's for the predecessor period January 1, 2016 to March 23, 2016 : Exelon Shares Weighted Average Grant Date Fair Value (per share) Nonvested at December 31, 2015 (a) 3,563,254 $ 32.92 Granted 3,042,184 28.14 Vested (1,797,536 ) 32.44 Forfeited (85,940 ) 30.08 Undistributed vested awards (b) (897,546 ) 28.35 Nonvested at December 31, 2016 (a)(c) 3,824,416 $ 30.49 PHI Time-based Shares Weighted Average Grant Date Fair Value (per share) Performance-based Shares Weighted Average Nonvested at December 31, 2015 628,514 $ 24.71 $ 408,638 $ 18.56 Granted 152,928 26.01 305,856 25.41 Vested — — (4,950 ) 26.08 Forfeited — — (1,238 ) 26.08 Nonvested at March 23, 2016 781,442 $ 24.96 $ 708,306 $ 21.45 ______________________ (a) Excludes 1,319,372 and 975,116 of restricted stock units issued to retirement-eligible employees as of December 31, 2016 and 2015 , respectively, as they are fully vested. (b) Represents restricted stock units that vested but were not distributed to retirement-eligible employees during 2016 . (c) 2016 amounts include activity related to stock-based compensation granted to eligible PHI employees since the merger date of March 23, 2016 . For Exelon, the weighted average grant date fair value (per share) of restricted stock units granted for the years ended December 31, 2016 , 2015 and 2014 was $28.14 , $36.55 and $28.71 , respectively. At December 31, 2016 and 2015 , Exelon had obligations related to outstanding restricted stock units not yet settled of $101 million and $97 million , respectively, which are included in common stock in Exelon’s Consolidated Balance Sheets. For the years ended December 31, 2016 , 2015 and 2014 , Exelon settled restricted stock units with fair value totaling $68 million , $75 million and $43 million , respectively. At December 31, 2016 , $58 million of total unrecognized compensation costs related to nonvested restricted stock units are expected to be recognized over the remaining weighted-average period of 2 years. For PHI, the weighted average grant date fair value (per share) of time-based restricted stock units granted for the years ended December 31, 2015 and 2014 was $27.40 and $19.77 , respectively, and for performance-based restricted stock units was $26.08 and $18.53 for the same periods, respectively. At December 31, 2015 PHI had obligations related to outstanding time-based and performance-based restricted stock units not yet settled of $1 million each, which are included in common stock in PHI’s Consolidated Balance Sheet. For the years ended December 31, 2015 and 2014 , PHI settled time-based restricted stock units with fair value totaling $6 million and $8 million , respectively, and settled performance-based restricted stock units with fair value totaling $15 million and $9 million , for the same periods, respectively. There were no settled restricted stock units for the predecessor period January 1, 2016 to March 23, 2016 . Performance Share Awards Performance share awards are granted under the LTIP. The performance share awards are being settled 50% in common stock and 50% in cash at the end of the three-year performance period, except for awards granted to vice presidents and higher officers that may be settled 100% in common stock, 100% in cash or 50%in common stock and 50% in cash if certain ownership requirements are satisfied. The common stock portion of the performance share is considered an equity award and is valued based on Exelon's stock price on the grant date. The cash portion of the awards is considered a liability award which is remeasured each reporting period based on Exelon’s current stock price. As the value of the common stock and cash portions of the awards are based on Exelon’s stock price during the performance period, coupled with changes in the total shareholder return modifier and expected payout of the award, the compensation costs are subject to volatility until payout is established. For nonretirement-eligible employees, stock-based compensation costs are recognized over the vesting period of three years using the graded-vesting method. For performance share awards granted to retirement-eligible employees, the value of the performance shares is recognized ratably over the vesting period, which is the year of grant. The following tables summarize Exelon’s and PHI's nonvested performance share awards activity for the year ended December 31, 2016 and PHI's for the predecessor period January 1, 2016 to March 23, 2016 : Exelon Shares (c) Weighted Average Grant Date Fair Value (per share) Nonvested at December 31, 2015 (a) 2,557,159 $ 31.88 Granted 2,319,407 28.85 Change in performance 627,303 30.04 Vested (949,315 ) 31.31 Forfeited (70,876 ) 30.90 Undistributed vested awards (b) (1,367,417 ) 28.33 Nonvested at December 31, 2016 (a) 3,116,261 $ 30.77 PHI Time-based Shares Weighted Average Grant Date Fair Value (per share) Performance-based Shares Weighted Average Nonvested at December 31, 2015 54,165 $ 26.80 24,717 $ 26.10 Vested — — (24,717 ) 26.10 Nonvested at March 23, 2016 54,165 $ 26.80 — $ — ________________ (a) Excludes 2,443,409 and 1,817,883 of performance share awards issued to retirement-eligible employees as of December 31, 2016 and 2015 , respectively, as they are fully vested. (b) Represents performance share awards that vested but were not distributed to retirement-eligible employees during 2016 . (c) 2016 amounts include PHI for the period of March 24, 2016 through December 31, 2016. For Exelon, the weighted average grant date fair value (per share) of performance share awards granted during the years ended December 31, 2016 , 2015 and 2014 was $28.85 , $35.88 , and $28.75 , respectively. During the years ended December 31, 2016 , 2015 and 2014 , Exelon settled performance shares with a fair value totaling $45 million , $46 million and $27 million , respectively, of which $28 million , $29 million and $13 million was paid in cash, respectively. As of December 31, 2016 , $51 million of total unrecognized compensation costs related to nonvested performance shares are expected to be recognized over the remaining weighted-average period of 2 years. For PHI, the weighted average grant date fair value (per share) of time-based restricted stock awards granted for the year ended December 31, 2014 was $26.80 and for performance-based restricted stock awards was $26.10 and $27.01 for the years ended December 31, 2015 and 2014 , respectively. There were no time-based restricted stock awards granted for the year ended December 31, 2015 . At December 31, 2015 PHI had no obligations related to vested time-based and performance-based restricted stock awards not yet settled. For the year ended December 31, 2014 PHI settled time-based shares with a fair value totaling $3 million . There were no time-based share settlements for the year-ended December 31, 2015 or the predecessor period January 1, 2016 to March 23, 2016 or performance-based share settlements for the predecessor period January 1, 2016 to March 23, 2016 and the years ended December 31, 2015 and 2014 . The following table presents the balance sheet classification of obligations related to outstanding performance share awards not yet settled: December 31, 2016 2015 (c) Current liabilities (a) $ 49 $ 28 Deferred credits and other liabilities (b) 52 32 Common stock 40 35 Total $ 141 $ 95 __________________________ (a) Represents the current liability related to performance share awards expected to be settled in cash. (b) Represents the long-term liability related to performance share awards expected to be settled in cash. (c) Excludes $8 million of common stock for PHI at December 31, 2015 .

Earnings Per Share and Equity (

Earnings Per Share and Equity (Exelon and BGE)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Earnings Per Share and Equity (Exelon and BGE)	(Exelon) Diluted earnings per share is calculated by dividing Net income attributable to common shareholders by the weighted average number of shares of common stock outstanding, including shares to be issued upon exercise of stock options, performance share awards and restricted stock outstanding under Exelon’s LTIPs considered to be common stock equivalents. The following table sets forth the components of basic and diluted earnings per share and shows the effect of the stock options, performance share awards and restricted stock on the weighted average number of shares outstanding used in calculating diluted earnings per share: Years Ended December 31, 2016 2015 2014 Net income attributable to common shareholders $ 1,134 $ 2,269 $ 1,623 Weighted average common shares outstanding—basic 924 890 860 Assumed exercise and/or distributions of stock-based awards 3 3 4 Weighted average common shares outstanding—diluted 927 893 864 The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was approximately 12 million in 2016 , 16 million in 2015 , and 17 million in 2014 . There were no equity units related to the PHI merger not included in the calculation of diluted common shares outstanding due to their antidilutive effect for the year ended December 31, 2016 . The number of equity units related to the PHI merger not included in the calculation of diluted common shares outstanding due to their antidilutive effect were 3 million and less than 1 million for the years ended December 31, 2015 and 2014 . Refer to Note 20 — Shareholders' Equity for further information regarding the equity units and equity forward units. Under share repurchase programs, 35 million shares of common stock are held as treasury stock with a cost of $ 2.3 billion as of December 31, 2016 . In 2008, Exelon management decided to defer indefinitely any share repurchases.

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Exelon, Generation, PECO and PHI)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Changes in Accumulated Other Comprehensive Income (Exelon, Generation, PECO and PHI)	Changes in Accumulated Other Comprehensive Income (Exelon, Generation, PECO and PHI) The following tables present changes in accumulated other comprehensive income (loss) (AOCI) by component for the years ended December 31, 2016 and 2015 : For the Year Ended December 31, 2016 Gains and (Losses) on Cash Flow Hedges Unrealized Pension and Gains and (Losses) on Foreign AOCI of Equity Investments Total Exelon (a) Beginning balance $ (19 ) $ 3 $ (2,565 ) $ (40 ) $ (3 ) $ (2,624 ) OCI before reclassifications (6 ) 1 (182 ) 5 (4 ) (186 ) Amounts reclassified from AOCI (b) 8 — 137 5 — 150 Net current-period OCI 2 1 (45 ) 10 (4 ) (36 ) Ending balance $ (17 ) $ 4 $ (2,610 ) $ (30 ) $ (7 ) $ (2,660 ) Generation (a) Beginning balance $ (21 ) $ 1 $ — $ (40 ) $ (3 ) $ (63 ) OCI before reclassifications (6 ) 1 — 5 (4 ) (4 ) Amounts reclassified from AOCI (b) 8 — — 5 — 13 Net current-period OCI 2 1 — 10 (4 ) 9 Ending balance $ (19 ) $ 2 $ — $ (30 ) $ (7 ) $ (54 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 PHI Predecessor (a) Beginning balance January 1, 2016 $ (8 ) $ — $ (28 ) $ — $ — $ (36 ) OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — 1 — — 1 Net current-period OCI — — 1 — — 1 Ending balance March 23, 2016 (c) $ (8 ) $ — $ (27 ) $ — $ — $ (35 ) For the Year Ended December 31, 2015 Gains and Unrealized Pension and Gains and (Losses) on Foreign AOCI of Total Exelon (a) Beginning balance $ (28 ) $ 3 $ (2,640 ) $ (19 ) $ — $ (2,684 ) OCI before reclassifications (12 ) — (100 ) (21 ) (3 ) (136 ) Amounts reclassified from AOCI (b) 21 — 175 — — 196 Net current-period OCI 9 — 75 (21 ) (3 ) 60 Ending balance $ (19 ) $ 3 $ (2,565 ) $ (40 ) $ (3 ) $ (2,624 ) Generation (a) Beginning balance $ (18 ) $ 1 $ — $ (19 ) $ — (36 ) OCI before reclassifications (8 ) — — (21 ) (3 ) (32 ) Amounts reclassified from AOCI (b) 5 — — — — 5 Net current-period OCI (3 ) — — (21 ) (3 ) (27 ) Ending balance $ (21 ) $ 1 $ — $ (40 ) $ (3 ) $ (63 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 PHI Predecessor (a) Beginning balance $ (9 ) $ — $ (37 ) $ — $ — $ (46 ) OCI before reclassifications — — 5 — — 5 Amounts reclassified from AOCI (b) 1 — 4 — — 5 Net current-period OCI 1 — 9 — — 10 Ending balance $ (8 ) $ — $ (28 ) $ — $ — $ (36 ) _______________________ (a) All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in accumulated other comprehensive income. (b) See next tables for details about these reclassifications. (c) As a result of the PHI Merger, the PHI predecessor balances at March 23, 2016 were reduced to zero on March 24, 2016 due to purchase accounting adjustments applied to PHI. ComEd, PECO, BGE, Pepco, DPL and ACE did not have any reclassifications out of AOCI to Net income during the years ended December 31, 2016 and 2015 . The following tables present amounts reclassified out of AOCI to Net income for Exelon, Generation and PHI during the years ended December 31, 2016 and 2015 : For the Year Ended December 31, 2016 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Predecessor January 1, 2016 to March 23, 2016 Exelon Generation PHI Gains and (losses) on cash flow hedges Other cash flow hedges $ (13 ) $ (13 ) $ — Interest expense Total before tax (13 ) (13 ) — Tax benefit 5 5 — Net of tax $ (8 ) $ (8 ) $ — Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 78 $ — $ — Actuarial losses (b) (302 ) — (1 ) Total before tax (224 ) — (1 ) Tax benefit 87 — — Net of tax $ (137 ) $ — $ (1 ) Gains and (losses) of FX Gains $ (5 ) $ (5 ) $ — Other — — — Total before tax (5 ) (5 ) — Tax benefit — — — Net of tax $ (5 ) $ (5 ) $ — Total Reclassifications $ (150 ) $ (13 ) $ (1 ) Comprehensive income For the Year Ended December 31, 2015 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Predecessor Exelon Generation PHI Gains and (losses) on cash flow hedges Terminated interest rate swaps $ (26 ) $ — $ — Other, net Energy related hedges 2 2 — Operating revenues Other cash flow hedges (11 ) (11 ) (1 ) Interest expense Total before tax (35 ) (9 ) (1 ) Tax benefit 14 4 — Net of tax $ (21 ) $ (5 ) $ (1 ) Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 74 $ — $ — Actuarial losses (b) (361 ) — (6 ) Total before tax (287 ) — (6 ) Tax benefit 112 — 2 Net of tax $ (175 ) $ — $ (4 ) Total Reclassifications $ (196 ) $ (5 ) $ (5 ) Comprehensive income _____________________ (a) Amounts in parenthesis represent a decrease in net income. (b) This accumulated other comprehensive income component is included in the computation of net periodic pension and OPEB cost (see Note 17 — Retirement Benefits for additional details). (c) Amortization of the deferred compensation unit plan is allocated to capital and operating and maintenance expense. The following table presents income tax expense (benefit) allocated to each component of other comprehensive income (loss) during the years ended December 31, 2016 and 2015 : For the Years Ended December 31, 2016 2015 2014 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 30 $ 30 $ 19 Actuarial loss reclassified to periodic cost (118 ) (140 ) (93 ) Pension and non-pension postretirement benefit plan valuation adjustment 115 62 317 Change in unrealized (gain) loss on cash flow hedges — (6 ) 96 Change in unrealized (gain) loss on equity investments 3 1 73 Total $ 30 $ (53 ) $ 412 Generation Change in unrealized loss on cash flow hedges $ (2 ) $ 2 $ 84 Change in unrealized (gain) loss on equity investments 3 1 73 Total $ 1 $ 3 $ 157 Predecessor January 1 to For the Years Ended December 31, PHI 2016 2015 2014 Pension and non-pension postretirement benefit plans: Actuarial loss reclassified to periodic cost $ — $ 6 $ 5

Commitments and Contingencies (

Commitments and Contingencies (All Registrants)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies (All Registrants)	Commitments and Contingencies (All Registrants) Commitments Constellation Merger Commitments In February 2012, the MDPSC issued an Order approving the Exelon and Constellation merger. As part of the MDPSC Order, Exelon agreed to provide a package of benefits to BGE customers, the City of Baltimore and the State of Maryland, resulting in an estimated direct investment in the State of Maryland of approximately $ 1 billion. The direct investment estimate includes $ 95 million to $ 120 million relating to the construction of a headquarters building in Baltimore for Generation’s competitive energy businesses. The direct investment commitment also includes $ 450 million to $ 500 million relating to Exelon and Generation’s development or assistance in the development of 285 - 300 MWs of new generation in Maryland, which is expected to be completed within a period of 10 years. The MDPSC order contemplates various options for complying with the new generation development commitments, including building or acquiring generating assets, making subsidy or compliance payments, or in circumstances in which the generation build is delayed or certain specified provisions are elected, making liquidated damages payments. Exelon and Generation have incurred $ 454 million towards satisfying the commitment for new generation development in the state of Maryland, with approximately 220 MW of the new generation commencing with commercial operations to date. D uring the third quarter of 2014, the conditions associated with one of the generation development commitments changed such that the most likely outcome would involve Exelon and Generation making subsidy payments and/or liquidated damages payments rather than constructing the specified generating plant. As a result, Exelon and Generation recorded a pre-tax $44 million loss contingency in Operating and maintenance expense related to this specific commitment that is included in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income for the year ended December 31, 2014. On December 19, 2016, Generation paid $44 million to the Maryland Energy Administration in full satisfaction of this commitment. During the fourth quarter of 2016, given continued declines in projected energy and capacity prices, Generation terminated rights to certain development projects originally intended to meet its remaining 55 MW commitment amount. The commitment will now most likely be satisfied via payment of liquidated damages or execution of a third party PPA, rather than by Generation constructing renewable generating assets. As a result, Exelon and Generation recorded a pre-tax $50 million loss contingency in Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income for the year ended December 31, 2016. Equity Investment Commitments As part of Generation's recent investments in technology development, Generation enters into equity purchase agreements that include commitments to invest additional equity through incremental payments to fund the anticipated needs of the planned operations of the associated companies. The commitment includes approximately $ 20 million of in-kind services and 100% of 2015 ESA Investco, LLC’s equity commitment since 2015 ESA Investco, LLC is consolidated by Generation (see Note 2 - Variable Interest Entities for additional details). As of December 31, 2016 , Generation’s estimated commitment relating to its equity purchase agreements, including in-kind services contributions, is anticipated to be as follows: Total 2017 $ 34 2018 5 Total $ 39 Commercial Commitments Exelon’s commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 1,614 $ 1,355 $ 246 $ — $ 13 $ — $ — Surety bonds (b) 1,035 978 33 2 16 6 — Financing trust guarantees (c) 628 — — — — — 628 Guaranteed lease residual values (d) 20 — — — — — 20 Total commercial commitments $ 3,297 $ 2,333 $ 279 $ 2 $ 29 $ 6 $ 648 ___________________________ (a) Letters of credit (non-debt)—Exelon and certain of its subsidiaries maintain non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (c) Includes $ 200 million of Trust Preferred Securities of ComEd Financing III, $ 178 million of Trust Preferred Securities of PECO Trust III and IV and $ 250 million of Trust Preferred Securities of BGE Capital Trust II. (d) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $50 million , $14 million of which is a guarantee by Pepco, $17 million by DPL and $13 million by ACE. The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote. Generation’s commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 1,546 $ 1,287 $ 246 $ — $ 13 $ — $ — Surety bonds 945 918 27 — — — — Total commercial commitments $ 2,491 $ 2,205 $ 273 $ — $ 13 $ — $ — ________________________ (a) Letters of credit (non-debt)—Non-debt letters of credit maintained to provide credit support for certain transactions as requested by third parties. ComEd’s commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 14 $ 14 $ — $ — $ — $ — $ — Surety bonds (b) 11 9 2 — — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 225 $ 23 $ 2 $ — $ — $ — $ 200 _________________________ (a) Letters of credit (non-debt)—ComEd maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. PECO’s commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 23 $ 23 $ — $ — $ — $ — $ — Surety bonds (b) 9 9 — — — — — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 210 $ 32 $ — $ — $ — $ — $ 178 ________________________ (a) Letters of credit (non-debt)—PECO maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. BGE’s commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 2 $ 2 $ — $ — $ — $ — $ — Surety bonds (b) 11 10 1 — — — — Financing trust guarantees 250 — — — — — 250 Total commercial commitments $ 263 $ 12 $ 1 $ — $ — $ — $ 250 ________________________ (a) Letters of credit (non-debt)—BGE maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. PHI commercial commitments (Successor) as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 1 $ 1 $ — $ — $ — $ — $ — Surety bonds (b) 16 14 2 — — — — Guaranteed lease residual values (c) 20 — — — — — 20 Total commercial commitments $ 37 $ 15 $ 2 $ — $ — $ — $ 20 ________________________ (a) Letters of credit (non-debt)—PHI and certain of its subsidiaries maintain non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (c) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $50 million . The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote. Pepco commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Surety bonds (a) 9 9 — — — — — Guaranteed lease residual values (b) 6 — — — — — 6 Total commercial commitments $ 15 $ 9 $ — $ — $ — $ — $ 6 ________________________ (a) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (b) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $ 14 million . The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote. DPL commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Surety bonds (a) 4 3 1 — — — — Guaranteed lease residual values (b) 7 — — — — — 7 Total commercial commitments $ 11 $ 3 $ 1 $ — $ — $ — $ 7 ________________________ (a) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (b) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $ 17 million . The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote. ACE commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 1 $ 1 $ — $ — $ — $ — $ — Surety bonds (b) 3 2 1 — — — — Guaranteed lease residual values (c) 5 — — — — — 5 Total commercial commitments $ 9 $ 3 $ 1 $ — $ — $ — $ 5 ________________________ (a) Letters of credit (non-debt)—ACE maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (c) R epresents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $ 13 million . The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote. Leases Minimum future operating lease payments, including lease payments for contracted generation, vehicles, real estate, computers, rail cars, operating equipment and office equipment, as of December 31, 2016 were: Exelon (a) Generation (a) ComEd (b) PECO (b) BGE (b)(c)(d) PHI Pepco DPL (b) ACE 2017 $ 183 $ 70 $ 11 $ 3 $ 32 $ 50 $ 7 $ 13 $ 8 2018 179 75 6 3 34 49 6 17 8 2019 123 30 6 4 34 36 5 7 7 2020 140 48 3 4 34 38 4 10 6 2021 133 47 3 4 32 34 3 9 5 Remaining years 968 644 — — 33 211 7 54 20 Total minimum future lease payments $ 1,726 $ 914 $ 29 $ 18 $ 199 $ 418 $ 32 $ 110 $ 54 ______________________ (a) Excludes Generation’s contingent operating lease payments associated with contracted generation agreements. (b) Amounts related to certain real estate leases and railroad licenses effectively have indefinite payment periods. As a result, ComEd, PECO, BGE and DPL have excluded these payments from the remaining years, as such amounts would not be meaningful. ComEd’s, PECO’s, BGE’s and DPL's average annual obligation for these arrangements, included in each of the years 2017—2021, was $ 2 million , $ 4 million , $ 2 million and $2 million , respectively. (c) Includes all future lease payments on a 99 year real estate lease that expires in 2106 . (d) The BGE column above includes minimum future lease payments associated with a 6-year lease for the Baltimore City conduit system that became effective during the fourth quarter of 2016. BGE's total commitments under the lease agreement are $ 21 million $ 25 million , $ 26 million , $ 27 million , $ 28 million , and $ 14 million related to years 2017, 2018, 2019, 2020, 2021 and thereafter, respectively. The following table presents the Registrants’ rental expense under operating leases for the years ended December 31, 2016, 2015 and 2014: For the Year Ended December 31, Exelon Generation (a) ComEd PECO BGE Pepco DPL ACE 2016 $ 777 $ 667 $ 15 $ 7 $ 22 $ 8 $ 15 $ 13 2015 922 851 12 9 32 7 14 13 2014 865 806 15 14 12 8 14 12 Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 PHI Rental expense under operating leases $ 49 12 60 59 ________________________ (a) Includes contingent operating lease payments associated with contracted generation agreements that are not included in the minimum future operating lease payments table above. Payments made under Generation’s contracted generation lease agreements totaled $604 million , $798 million and $755 million during 2016 , 2015 and 2014 , respectively. Excludes contract amortization associated with purchase accounting and contract acquisitions. For information regarding capital lease obligations, see Note 14 —Debt and Credit Agreements. Nuclear Insurance Generation is subject to liability, property damage and other risks associated with major incidents at any of its nuclear stations, including the CENG nuclear stations. Generation has mitigated its financial exposure to these risks through insurance and other industry risk-sharing provisions. The Price-Anderson Act was enacted to ensure the availability of funds for public liability claims arising from an incident at any of the U.S. licensed nuclear facilities and also to limit the liability of nuclear reactor owners for such claims from any single incident. As of December 31, 2016 , the current liability limit per incident is $13.4 billion and is subject to change to account for the effects of inflation and changes in the number of licensed reactors at least once every five years with the last adjustment effective September 10, 2013. In accordance with the Price-Anderson Act, Generation maintains financial protection at levels equal to the amount of liability insurance available from private sources through the purchase of private nuclear energy liability insurance for public liability claims that could arise in the event of an incident. Effective January 1, 2017, the required amount of nuclear energy liability insurance purchased is $450 million for each operating site. Claims exceeding that amount are covered through mandatory participation in a financial protection pool, as required by the Price Anderson-Act, which provides the additional $ 13.0 billion per incident in funds available for public liability claims. Participation in this secondary financial protection pool requires the operator of each reactor to fund its proportionate share of costs for any single incident that exceeds the primary layer of financial protection. Exelon’s share of this secondary layer would be approximately $ 2.7 billion , including CENG's related liability, however any amounts payable under this secondary layer would be capped at $ 400 million per year. In addition, the U.S. Congress could impose revenue-raising measures on the nuclear industry to pay public liability claims exceeding the $ 13.4 billion limit for a single incident. As part of the execution of the NOSA on April 1, 2014, Generation executed an Indemnity Agreement pursuant to which Generation agreed to indemnify EDF and its affiliates against third-party claims that may arise from any future nuclear incident (as defined in the Price-Anderson Act) in connection with the CENG nuclear plants or their operations. Exelon guarantees Generation’s obligations under this indemnity. See Note 5 - Investment in Constellation Energy Nuclear Group, LLC for additional information on Generation’s operations relating to CENG. Generation is required each year to report to the NRC the current levels and sources of property insurance that demonstrates Generation possesses sufficient financial resources to stabilize and decontaminate a reactor and reactor station site in the event of an accident. The property insurance maintained for each facility is currently provided through insurance policies purchased from NEIL, an industry mutual insurance company of which Generation is a member. NEIL may declare distributions to its members as a result of favorable operating experience. In recent years NEIL has made distributions to its members, but Generation cannot predict the level of future distributions or if they will continue at all. Generation's portion of the distribution declared by NEIL is estimated to be $21 million for 2016, and was $21 million for 2015 and $18 million for 2014. The distributions were recorded as a reduction to Operating and maintenance expense within Exelon and Generation’s Consolidated Statements of Operations and Comprehensive Income. Premiums paid to NEIL by its members are also subject to a potential assessment for adverse loss experience in the form of a retrospective premium obligation. NEIL has never assessed this retrospective premium since its formation in 1973, and Generation cannot predict the level of future assessments if any. The current maximum aggregate annual retrospective premium obligation for Generation is approximately $353 million . NEIL requires its members to maintain an investment grade credit rating or to ensure collectability of their annual retrospective premium obligation by providing a financial guarantee, letter of credit, deposit premium, or some other means of assurance. NEIL provides “all risk” property damage, decontamination and premature decommissioning insurance for each station for losses resulting from damage to its nuclear plants, either due to accidents or acts of terrorism. If the decision is made to decommission the facility, a portion of the insurance proceeds will be allocated to a fund, which Generation is required by the NRC to maintain, to provide for decommissioning the facility. In the event of an insured loss, Generation is unable to predict the timing of the availability of insurance proceeds to Generation and the amount of such proceeds that would be available. In the event that one or more acts of terrorism cause accidental property damage within a twelve-month period from the first accidental property damage under one or more policies for all insured plants, the maximum recovery by Exelon will be an aggregate of $ 3.2 billion plus such additional amounts as the insurer may recover for all such losses from reinsurance, indemnity and any other source, applicable to such losses. For its insured losses, Generation is self-insured to the extent that losses are within the policy deductible or exceed the amount of insurance maintained. Uninsured losses and other expenses, to the extent not recoverable from insurers or the nuclear industry, could also be borne by Generation. Any such losses could have a material adverse effect on Exelon’s and Generation’s financial condition, results of operations and liquidity. Spent Nuclear Fuel Obligation Under the NWPA, the DOE is responsible for the development of a geologic repository for and the disposal of SNF and high-level radioactive waste. As required by the NWPA, Generation is a party to contracts with the DOE (Standard Contracts) to provide for disposal of SNF from Generation’s nuclear generating stations. In accordance with the NWPA and the Standard Contracts, Generation historically had paid the DOE one mill ( $0.001 ) per kWh of net nuclear generation for the cost of SNF disposal. On November 19, 2013, the D.C. Circuit Court ordered the DOE to submit to Congress a proposal to reduce the current SNF disposal fee to zero, unless and until there is a viable disposal program. On May 9, 2014, the DOE notified Generation that the SNF disposal fee remained in effect through May 15, 2014, after which time the fee was set to zero. As a result, for the year ended December 31, 2016 , and December 31, 2015 , Generation did not incur any expense in SNF disposal fees. For the year ended December 31, 2014 , Generation incurred expense of $49 million in SNF disposal fees recorded in Purchased power and fuel expense within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income, including Exelon’s share of Salem and net of co-owner reimbursements (not including such fees incurred by CENG). Until such time as a new fee structure is in effect, Exelon and Generation will not accrue any further costs related to SNF disposal fees. This fee may be adjusted prospectively in order to ensure full cost recovery. The NWPA and the Standard Contracts required the DOE to begin taking possession of SNF generated by nuclear generating units by no later than January 31, 1998. The DOE, however, failed to meet that deadline and its performance has been, and is expected to be, delayed significantly. The 2010 Federal budget (which became effective October 1, 2009) eliminated almost all funding for the creation of the Yucca Mountain repository while the Obama Administration devised a new strategy for long-term SNF management. A Blue Ribbon Commission (BRC) on America’s Nuclear Future, appointed by the U.S. Energy Secretary, released a report on January 26, 2012, detailing comprehensive recommendations for creating a safe, long-term solution for managing and disposing of the nation’s SNF and high-level radioactive waste. In early 2013, the DOE issued an updated “Strategy for the Management and Disposal of Used Nuclear Fuel and High-Level Radioactive Waste” in response to the BRC recommendations. This strategy included a consolidated interim storage facility that was planned to be operational in 2025. However, due to continued delays on the part of the DOE, Generation currently assumes the DOE will begin accepting SNF in 2030. The SNF acceptance date assumption is based on management’s estimates of the amount of time required for DOE to select a site location and develop the necessary infrastructure for long-term SNF storage. Generation uses the 2030 date as the assumed date for when the DOE will begin accepting SNF for purposes of determining nuclear decommissioning asset retirement obligations. In August 2004, Generation and the DOJ, in close consultation with the DOE, reached a settlement under which the government agreed to reimburse Generation, subject to certain damage limitations based on the extent of the government’s breach, for costs associated with storage of SNF at Generation’s nuclear stations pending the DOE’s fulfillment of its obligations. A settlement agreement for Calvert Cliffs and Nine Mile Point was executed during 2011, pursuant to which the government agreed to reimburse the costs associated with SNF storage expended or to be expended during a term set by the agreement. The term was subsequently extended during 2014 to include SNF storage costs incurred at Calvert Cliffs and Nine Mile Point through December 31, 2016. A DOE settlement agreement for Ginna was also executed during 2011. During 2015, Ginna executed another DOE settlement agreement providing for the reimbursement of SNF storage costs incurred through December 31, 2016. Generation expects the terms for each of the settlement agreements to be extended during 2017 for another three years to cover SNF storage costs through December 31, 2019. Generation, including CENG, submits annual reimbursement requests to the DOE for costs associated with the storage of SNF. In all cases, reimbursement requests are made only after costs are incurred and only for costs resulting from DOE delays in accepting the SNF. Under the settlement agreement, Generation has received cumulative cash reimbursements for costs incurred as follows: Total Net (a) Cumulative cash reimbursements (b) $ 1,038 $ 887 _____________________________ (a) Total after considering amounts due to co-owners of certain nuclear stations and to the former owner of Oyster Creek. (b) Includes $53 million and $49 million , respectively, for amounts received since April 1, 2014, for costs incurred under the CENG DOE Settlement Agreements prior to the consolidation of CENG. As of December 31, 2016, and 2015, the amount of SNF storage costs for which reimbursement has been or will be requested from the DOE under the DOE settlement agreements is as follows: December 31, 2016 December 31, 2015 DOE receivable - current (a) $ 109 $ 76 DOE receivable - noncurrent (b) 15 14 Amounts owed to co-owners (a)(c) (13 ) (5 ) _____________________________ (a) Recorded in Accounts receivable, other. (b) Recorded in Deferred debits and other assets, other (c) Non-CENG amounts owed to co-owners are recorded in Accounts receivable, other. CENG amounts owed to co-owners are recorded in Accounts payable. Represents amounts owed to the co-owners of Peach Bottom, Quad Cities, and Nine Mile Point Unit 2 generating facilities. The Standard Contracts with the DOE also required the payment to the DOE of a one-time fee applicable to nuclear generation through April 6, 1983. The fee related to the former PECO units has been paid. Pursuant to the Standard Contracts, ComEd previously elected to defer payment of the one-time fee of $277 million for its units (which are now part of Generation), with interest to the date of payment, until just prior to the first delivery of SNF to the DOE. As of December 31, 2016 , the unfunded SNF liability for the one-time fee with interest was $1,024 million . Interest accrues at the 13 -week Treasury Rate. The 13 -week Treasury Rate in effect, for calculation of the interest accrual at December 31, 2016 , was 0.355% . The liabilities for SNF disposal costs, including the one-time fee, were transferred to Generation as part of Exelon’s 2001 corporate restructuring. The outstanding one-time fee obligations for the Nine Mile Point, Ginna, Oyster Creek and TMI units remain with the former owners. The Clinton and Calvert Cliffs units have no outstanding obligation. See Note 12 — Fair Value of Financial Assets and Liabilities for additional information. Environmental Remediation Matters General. The Registrants’ operations have in the past, and may in the future, require substantial expenditures in order to comply with environmental laws. Additionally, under Federal and state environmental laws, the Registrants are generally liable for the costs of remediating environmental contamination of property now or formerly owned by them and of property contaminated by hazardous substances generated by them. The Registrants own or lease a number of real estate parcels, including parcels on which their operations or the operations of others may have resulted in contamination by substances that are considered hazardous under environmental laws. In addition, the Registrants are currently involved in a number of proceedings relating to sites where hazardous substances have been deposited and may be subject to additional proceedings in the future. ComEd, PECO, BGE, and DPL have identified sites where former MGP activities have or may have resulted in actual site contamination. For almost all of these sites, there are additional PRPs that may share responsibility for the ultimate remediation of each location. • ComEd has identified 42 sites, 18 of which have been remediated and approved by the Illinois EPA or the U.S. EPA and 24 that are currently under some degree of active study and/or remediation. ComEd expects the majority of the remediation at these sites to continue through at least 2021. • PECO has identified 26 sites, 17 of which have been remediated in accordance with applicable PA DEP regulatory requirements. The remaining 9 sites are currently under some degree of active study and/or remediation. PECO expects the majority of the remediation at these sites to continue through at least 2022. • BGE has identified 13 former gas manufacturing or purification sites that it currently owns or owned at one time through a predecessor’s acquisition. Two gas manufacturing sites require some level of remediation and ongoing monitoring under the direction of the MDE. The required costs at these 2 sites are not considered material. An investigation of an additional gas purification site was completed during the first quarter of 2015 at the direction of the MDE. For more information, see the discussion of the Riverside site below. • DPL has identified 2 sites, all of which the remediation has been completed and approved by the MDE or the Delaware Department of Natural Resources and Environmental Control. ComEd, pursuant to an ICC order, and PECO, pursuant to settlements of natural gas distribution rate cases with the PAPUC, are currently recovering environmental remediation costs of former MGP facility sites through customer rates. See Note 3 — Regulatory Matters for additional information regarding the associated regulatory assets. BGE is authorized to recover, and is currently recovering, environmental costs for the remediation of the former MGP facility sites from customers; however, while BGE does not have a rider for MGP clean-up costs, BGE has historically received recovery of actual clean-up costs in distribution rates. DPL has historically received recovery of actual clean-up costs in distribution rates. As of December 31, 2016 and 2015, the Registrants had accrued the following undiscounted amounts for environmental liabilities in Other current liabilities and Other deferred credits and other liabilities within their respective Consolidated Balance Sheets: December 31, 2016 Total environmental investigation and remediation reserve Portion of total related to MGP investigation and remediation (a) Exelon $ 429 $ 325 Generation 72 — ComEd 292 291 PECO 33 31 BGE (a) 2 2 PHI 30 1 Pepco 27 — DPL 2 1 ACE 1 — December 31, 2015 Total environmental investigation and remediation reserve Portion of total related to MGP investigation and remediation Exelon $ 369 $ 301 Generation 63 — ComEd 266 264 PECO 37 35 BGE 3 2 PHI (Predecessor) 33 1 Pepco 24 — DPL 3 1 ACE 1 — The historical nature of the MGP sites and the fact that many of the sites have been buried and built over, impacts the ability to determine a precise estimate of the ultimate costs prior to initial sampling and determination of the exact scope and method of remedial activity. Management determines its best estimate of remediation costs using all available information at t

Supplemental Financial Informat

Supplemental Financial Information (All Registrants)	12 Months Ended
	Dec. 31, 2016
Supplemental Financial Information [Abstract]
Supplemental Financial Information (All Registrants)	Supplemental Financial Information (All Registrants) Supplemental Statement of Operations Information The following tables provide additional information about the Registrants’ Consolidated Statements of Operations and Comprehensive Income for the years ended December 31, 2016 , 2015 and 2014 . Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the year ended December 31, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Taxes other than income Utility (a) $ 753 $ 122 $ 242 $ 136 $ 85 $ 312 $ 18 $ — $ 253 $ 78 Property 483 246 27 13 123 53 31 3 73 18 Payroll 226 117 28 15 17 8 5 3 23 8 Other 114 21 (4 ) — 4 4 1 1 5 1 Total taxes other than income $ 1,576 $ 506 $ 293 $ 164 $ 229 $ 377 $ 55 $ 7 $ 354 $ 105 Predecessor For the year ended December 31, 2015 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Taxes other than income Utility (a) $ 474 $ 105 $ 236 $ 133 $ 85 $ 326 $ 308 $ 18 $ — Property 407 250 27 11 119 94 57 28 3 Payroll 201 118 28 14 16 27 6 4 2 Other 118 16 5 2 4 8 5 1 2 Total taxes other than income $ 1,200 $ 489 $ 296 $ 160 $ 224 $ 455 $ 376 $ 51 $ 7 Predecessor For the year ended December 31, 2014 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Taxes other than income Utility (a) $ 456 $ 89 $ 238 $ 128 $ 86 $ 324 $ 307 $ 17 $ — Property 396 240 25 15 114 85 51 24 3 Payroll 200 118 28 14 18 23 6 4 2 Other 102 18 2 2 3 5 5 1 (1 ) Total taxes other than income $ 1,154 $ 465 $ 293 $ 159 $ 221 $ 437 $ 369 $ 46 $ 4 _____________________ (a) Generation’s utility tax represents gross receipts tax related to its retail operations and ComEd’s, PECO’s, BGE’s, Pepco's, DPL's and ACE's utility taxes represent municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the year ended December 31, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 237 $ 237 $ — $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 126 126 — — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 216 216 — — — — — — — — Non-regulatory agreement units 194 194 — — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (1 ) (1 ) — — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (372 ) (372 ) — — — — — — — — Total decommissioning-related activities 400 400 — — — — — — — — Investment income (loss) 17 8 — (1 ) 2 (f) 1 — 1 1 — Long-term lease income 4 — — — — — — — — — Interest income related to uncertain income tax positions 13 — — — — 1 — — (1 ) — Penalty related to uncertain income tax positions (c) (106 ) — (86 ) — — — — — — — AFUDC—Equity 64 — 14 8 19 19 5 6 23 7 Loss on debt extinguishment (3 ) (2 ) — — — — — — — — Other 24 (5 ) 7 1 — 15 8 2 21 (11 ) Other, net $ 413 $ 401 $ (65 ) $ 8 $ 21 $ 36 $ 13 $ 9 $ 44 $ (4 ) Predecessor For the year ended December 31, 2015 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 232 $ 232 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 156 156 — — — — — — — Net unrealized losses on decommissioning trust funds— Regulatory agreement units (282 ) (282 ) — — — — — — — Non-regulatory agreement units (197 ) (197 ) — — — — — — — Net unrealized gains on pledged assets Zion Station decommissioning 7 7 — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) 21 21 — — — — — — — Total decommissioning-related activities (63 ) (63 ) — — — — — — — Investment income (loss) 8 3 — (2 ) 4 (f) — — — — Long-term lease income 15 — — — — — — — — Interest income related to uncertain income tax positions 1 1 — — — 34 5 — — AFUDC—Equity 24 — 5 5 14 14 12 1 1 Terminated interest rate swaps (d) (26 ) — — — — — — — — PHI merger related debt exchange (e) (22 ) — — — — — — — — Other 17 (1 ) 16 2 — 40 11 9 2 Other, net $ (46 ) $ (60 ) $ 21 $ 5 $ 18 $ 88 $ 28 $ 10 $ 3 Predecessor For the year ended December 31, 2014 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 216 $ 216 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 159 159 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 180 180 — — — Non-regulatory agreement units 134 134 — — — — — — — Net unrealized gains on pledged assets Zion Station decommissioning 29 29 — — — — Regulatory offset to decommissioning trust fund-related activities (b) (358 ) (358 ) — — — — — — Total decommissioning-related activities 360 360 — — — — — — — Investment income (loss) 1 1 — (1 ) 7 (f) 1 — — — Long-term lease income 24 — — — — — — — — Interest income related to uncertain income tax positions 40 54 — — — — 1 — 1 AFUDC—Equity 21 — 3 6 12 13 10 2 1 Other 9 (9 ) 14 2 (1 ) 30 19 8 1 Other, net $ 455 $ 406 $ 17 $ 7 $ 18 $ 44 $ 30 $ 10 $ 3 _________________________ (a) Includes investment income and realized gains and losses on sales of investments within the nuclear decommissioning trust funds. (b) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of net income taxes related to all NDT fund activity for those units. See Note 16 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning. (c) See Note 15 — Income Taxes for discussion of the penalty related to the Tax Court’s decision on Exelon’s like-kind exchange tax position. (d) In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated certain floating-to-fixed interest rate swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from AOCI to Other, net in Exelon's Consolidated Statements of Operations and Comprehensive Income. (e) See Note 14 — Debt and Credit Agreements and Note 4 — Mergers, Acquisitions, and Dispositions for additional information on the PHI merger related debt exchange. (f) Relates to the cash return on BGE’s rate stabilization deferral. See Note 3 — Regulatory Matters for additional information regarding the rate stabilization deferral. Supplemental Cash Flow Information The following tables provide additional information regarding the Registrants’ Consolidated Statements of Cash Flows for the years ended December 31, 2016 , 2015 and 2014 . Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the year ended December 31, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Depreciation, amortization and accretion Property, plant and equipment $ 3,477 $ 1,835 $ 708 $ 244 $ 299 $ 175 $ 110 $ 82 $ 325 $ 94 Regulatory assets 407 — 67 26 124 120 47 83 190 58 Amortization of intangible assets, net 52 44 — — — — — — — — Amortization of energy contract assets and liabilities (a) 35 35 — — — — — — — — Nuclear fuel (b) 1,159 1,159 — — — — — — — — ARO accretion (c) 446 446 — — — — — — — — Total depreciation, amortization and accretion $ 5,576 $ 3,519 $ 775 $ 270 $ 423 $ 295 $ 157 $ 165 $ 515 $ 152 Predecessor For the year ended December 31, 2015 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Depreciation, amortization and accretion Property, plant and equipment $ 2,227 $ 1,007 $ 635 $ 240 $ 289 $ 164 $ 103 $ 76 $ 392 Regulatory assets 170 — 72 20 77 92 45 99 232 Amortization of intangible assets, net 54 47 — — — — — — — Amortization of energy contract assets and liabilities (a) 22 22 — — — — — — — Nuclear fuel (b) 1,116 1,116 — — — — — — — ARO accretion (c) 398 397 — — — — — — — Total depreciation, amortization and accretion $ 3,987 $ 2,589 $ 707 $ 260 $ 366 $ 256 $ 148 $ 175 $ 624 Predecessor For the year ended December 31, 2014 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Depreciation, amortization and accretion Property, plant and equipment $ 2,080 $ 922 $ 588 $ 227 $ 288 $ 155 $ 94 $ 72 $ 363 Regulatory assets 191 — 99 9 83 57 28 83 163 Amortization of intangible assets, net 44 44 — — — — — — — Amortization of energy contract assets and liabilities (a) 135 135 — — — — — — — Nuclear fuel (b) 1,073 1,073 — — — — — — — ARO accretion (c) 345 345 — — — — — — — Total depreciation, amortization and accretion $ 3,868 $ 2,519 $ 687 $ 236 $ 371 $ 212 $ 122 $ 155 $ 526 ________________________ (a) Included in Operating revenues or Purchased power and fuel on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (b) Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the year ended December 31, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Cash paid (refunded) during the year: Interest (net of amount capitalized) $ 1,340 $ 339 $ 298 $ 104 $ 92 $ 118 $ 47 $ 62 $ 209 $ 43 Income taxes (net of refunds) (441 ) 435 (444 ) 64 31 216 115 200 258 11 Pension and non-pension postretirement benefit costs $ 619 $ 218 $ 166 $ 33 $ 67 $ 31 $ 18 $ 15 $ 86 $ 23 Loss from equity method investments 24 25 — — — — — — — — Provision for uncollectible accounts 155 19 41 30 1 29 23 32 65 16 Provision for excess and obsolete inventory 12 6 4 — — 3 1 1 1 1 Stock-based compensation costs 111 — — — — — — — — 3 Other decommissioning-related activity (a) (384 ) (384 ) — — — — — — — — Energy-related options (b) (11 ) (11 ) — — — — — — — — Amortization of regulatory asset related to debt costs 9 — 4 1 — 2 1 1 3 1 Amortization of rate stabilization deferral 76 — — — 81 (12 ) 2 — (5 ) 5 Amortization of debt fair value adjustment (11 ) (11 ) — — — — — — — — Merger-related commitments (c)(d) 558 53 — — — 125 82 110 317 — Severance costs 99 22 — — — — — — 56 — Asset retirement costs 2 — — — — — 1 2 2 — Amortization of debt costs 35 17 4 3 1 — — — 1 — Discrete impacts from EIMA (e) 8 — 8 — — — — — — — Lower of cost or market inventory adjustment 37 36 — 1 — — — — — — Baltimore City Conduit Lease Settlement (28 ) — — — (28 ) — — — — — Cash Working Capital Order (13 ) — — — (13 ) — — — — — Other 35 25 (12 ) (3 ) (21 ) 5 (14 ) (6 ) (12 ) (3 ) Total other non-cash operating activities $ 1,333 $ 15 $ 215 $ 65 $ 88 $ 183 $ 114 $ 155 $ 514 $ 46 Non-cash investing and financing activities: Change in capital expenditures not paid $ (128 ) $ 50 $ (91 ) $ (11 ) $ (86 ) $ 27 $ (12 ) $ 11 $ 21 $ 11 Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash — 119 — — — — — — — — Fair value of net assets distributed to Exelon in connection with the PHI Merger, net of cash (c)(f) — — — — — — — — 127 — Fair value of pension obligation transferred in connection with the PHI Merger (c)(f) — — — — — — — — 53 — Assumption of member purchase liability — — — — — — — — 29 — Assumption of merger commitment liability — — — — — 33 — — 33 — Change in PPE related to ARO update 191 191 — — — — — — — — Non-cash financing of capital projects 95 95 — — — — — — — — Indemnification of like-kind exchange position (h) — — 158 — — — — — — — Sale of Upstream assets (c) 37 37 — — — — — — — — Pending FitzPatrick Acquisition (i) (54 ) (54 ) — — — — — — — — ____________________________ (a) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 16 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) See Note 4 - Mergers, Acquisitions, and Dispositions for more information. (d) Excludes $5 million of forgiveness of Accounts receivable related to merger commitments recorded in connection with the PHI Merger, the balance is included within Provision for uncollectible accounts. (e) Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate. See Note 3 — Regulatory Matters for more information. (f) Immediately following closing of the PHI Merger, the net assets associated with PHI’s unregulated business interests were distributed by PHI to Exelon. Exelon contributed a portion of such net assets to Generation. (g) Relates to the nuclear fuel procurement contract for the purchase of fixed quantities of converted uranium, which was delivered to Generation in 2015. Generation is required to make payments starting September 28, 2018, with the final payment being due no later than September 30, 2020. (h) See Note 15 — Income Taxes for discussion of the like-kind exchange tax position. (i) Reflects the transfer of nuclear fuel to Entergy under the cost reimbursement provisions of the FitzPatrick acquisition agreements. See Note 4 - Mergers, Acquisitions, and Dispositions for more information. Predecessor For the year ended December 31, 2015 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Cash paid (refunded) during the year: Interest (net of amount capitalized) $ 930 $ 348 $ 308 $ 94 $ 120 $ 116 $ 47 $ 63 $ 268 Income taxes (net of refunds) 342 476 (265 ) 64 73 (6 ) (5 ) — (13 ) Pension and non-pension postretirement benefit costs $ 637 $ 269 $ 206 $ 39 $ 65 $ 30 $ 15 $ 15 $ 97 Loss from equity method investments 7 8 — — — — — — — Provision for uncollectible accounts 120 22 53 30 15 21 20 20 61 Stock-based compensation costs 97 — — — — — — — 13 Other decommissioning-related activity (a) (82 ) (82 ) — — — — — — — Energy-related options (b) 21 21 — — — — — — — Amortization of regulatory asset related to debt costs 7 — 5 2 — 2 1 1 5 Amortization of rate stabilization deferral 73 — — — 73 1 (3 ) — (2 ) Amortization of debt fair value adjustment (17 ) (17 ) — — — — — — — Discrete impacts from EIMA (c) 144 — 144 — — — — — — Amortization of debt costs 58 15 4 2 2 — — — 2 Provision for excess and obsolete inventory 10 9 1 — — — — — 1 Lower of cost or market inventory adjustment 23 23 — — — — — — — Other 11 — 3 (3 ) (18 ) — — 1 (10 ) Total other non-cash operating activities $ 1,109 $ 268 $ 416 $ 70 $ 137 $ 54 $ 33 $ 37 $ 167 Non-cash investing and financing activities: Change in capital expenditures not paid $ 96 $ 82 $ 34 $ (13 ) $ (9 ) $ (1 ) $ 3 $ 3 $ 6 Nuclear fuel procurement (d) 57 57 — — — — — — — Change in PPE related to ARO update 885 885 — — — — — — — Indemnification of like-kind exchange position (e) — — 7 — — — — — — Non-cash financing of capital projects 77 77 — — — — — — — Long-term software licensing agreement (f) 95 — — — — — — — — ______________________ (a) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 16 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate. See Note 3 — Regulatory Matters for more information. (d) Relates to the nuclear fuel procurement contract for the purchase of fixed quantities of converted uranium, which was delivered to Generation in 2015. Generation is required to make payments starting September 28, 2018, with the final payment being due no later than September 30, 2020. (e) See Note 15 — Income Taxes for discussion of the like-kind exchange tax position. (f) Relates to a long-term software license agreement entered into on May 30, 2015. Exelon is required to make payments starting August of 2015 through May of 2024. See Note 14 — Debt and Credit Agreements for additional information. Predecessor For the year ended December 31, 2014 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Cash paid (refunded) during the year: Interest (net of amount capitalized) $ 940 $ 322 $ 292 $ 94 $ 111 $ 111 $ 45 $ 61 $ 257 Income taxes (net of refunds) 314 227 (6 ) 85 (21 ) (58 ) (43 ) (3 ) (2 ) Pension and non-pension postretirement benefit costs $ 560 $ 249 $ 162 $ 36 $ 64 $ 22 $ 7 $ 13 $ 58 Loss from equity method investments 22 20 — — — — — — — Provision for uncollectible accounts 156 14 26 52 64 17 14 13 49 Provision for excess and obsolete inventory 5 5 — — — — — — — Stock-based compensation costs 91 — — — — — — — 18 Other decommissioning-related activity (a) (132 ) (132 ) — — — — — — — Energy-related options (b) 122 122 — — — — — — — Amortization of regulatory asset related to debt costs 11 — 8 3 — 3 2 — 5 Amortization of rate stabilization deferral 65 — — — 65 3 (1 ) — 2 Amortization of debt fair value adjustment (23 ) (23 ) — — — — — — — Merger-related commitments 44 44 — — — — — — — Discrete impacts from EIMA (c) 53 — 53 — — — — — — Amortization of debt costs 53 12 4 2 2 — — — 1 Lower of cost or market inventory adjustment 29 29 — — — — — — — Other (2 ) 6 2 (1 ) (15 ) (8 ) — — (6 ) Total other non-cash operating activities $ 1,054 $ 346 $ 255 $ 92 $ 180 $ 37 $ 22 $ 26 $ 127 Non-cash investing and financing activities: Change in PPE related to ARO update $ 72 $ 72 $ — $ — $ — $ — $ — $ — $ — Change in capital expenditures not paid 220 (61 ) (d) 78 — 25 10 8 9 28 Fair value of net assets recorded upon CENG consolidation (e) 3,400 3,400 — — — — — — — Issuance of equity units (f) 131 — — — — — — — — Nuclear fuel procurement (g) 70 70 — — — — — — — Indemnification of like-kind exchange position (h) — — 5 — — — — — — _________________________ (a) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 16 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate. See Note 3 — Regulatory Matters for more information. (d) Includes $170 million of changes in capital expenditures not paid between December 31, 2014 and 2013 related to Antelope Valley. (e) See Note 5 — Investment in Constellation Energy Nuclear Group, LLC for additional information. (f) Relates to the present value of the contract payments for the equity units issued by Exelon. See Note 21 — Stock-Based Compensation Plans for additional information. (g) Relates to the nuclear fuel procurement contracts for the purchase of fixed quantities of uranium, which was delivered to Generation in 2014. Generation is required to make payments starting June 30, 2016, with the final payment being due no later than June 30, 2018. (h) See Note 15 — Income Taxes for discussion of the like-kind exchange tax position. DOE Smart Grid Investment Grant (Exelon, PECO and BGE). For the year ended December 31, 2014, PECO has included in the capital expenditures line item under investing activities of the cash flow statement capital expenditures of $ 2 million and reimbursements of $ 5 million related to PECO’s DOE SGIG programs. For the years ended December 31, 2016 and 2015, PECO had no capital expenditures or reimbursements, as the DOE SGIG program was completed during 2014. See Note 3 — Regulatory Matters for additional information regarding the DOE SGIG. Supplemental Balance Sheet Information The following tables provide additional information about assets and liabilities of the Registrants at December 31, 2016 and 2015 . Successor December 31, 2016 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Investments Equity method investments: Financing trusts (a) $ 22 $ — $ 6 $ 8 $ 8 $ — $ — $ — $ — Bloom 216 216 — — — — — — — Net Power 57 57 — — — — — — — Other equity method investments 16 15 — — — — — — — Total equity method investments 311 288 6 8 8 — — — — Other investments: Employee benefit trusts and investments (c) 232 44 — 17 4 133 102 — — Other cost method investments 52 52 — — — — — — — Other available for sale investments 34 34 — — — — — — — Total investments $ 629 $ 418 $ 6 $ 25 $ 12 $ 133 $ 102 $ — $ — Predecessor December 31, 2015 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Investments Equity method investments: Financing trusts (a) $ 22 $ — $ 6 $ 8 $ 8 $ — $ — $ — $ — Bloom 63 63 — — — — — — — Net Power 23 23 — — — — — — — Other equity method investments 4 3 — — — — — — — Total equity method investments 112 89 6 8 8 — — — — Other investments: Net investment in leases (b) 358 6 — — — — — — — Employee benefit trusts and investments(c) 85 31 — 20 4 80 68 — — Other cost method investments 55 55 — — — — — — — Other available for sale investments 29 29 — — — — — — — Total investments $ 639 $ 210 $ 6 $ 28 $ 12 $ 80 $ 68 $ — $ — _________________________ (a) Includes investments in affiliated financing trusts, which were not consolidated within the financial statements of Exelon and are shown as investments on the Consolidated Balance Sheets. See Note 1 — Significant Accounting Policies for additional information. (b) Represents direct financing lease investments. See Note 8 — Impairment of Long-Lived Assets for additional information. (c) The Registrants’ investments in these marketable securities are recorded at fair market value. The following tables provide additional information about liabilities of the Registrants at December 31, 2016 and 2015 . Successor December 31, 2016 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Accrued expenses Compensation-related accruals (a) $ 1,199 $ 557 $ 199 $ 67 $ 64 $ 112 $ 30 $ 17 $ 11 Taxes accrued 723 239 330 4 78 65 48 4 9 Interest accrued 1,234 82 609 30 31 49 21 8 12 Severance accrued 44 15 2 — — 19 — — — Other accrued expenses 260 96 110 3 2 27 14 7 6 Total accrued expenses $ 3,460 $ 989 $ 1,250 $ 104 $ 175 $ 272 $ 113 $ 36 $ 38 Predecessor December 31, 2015 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Accrued expenses Compensation-related accruals (a) $ 1,014 $ 547 $ 183 $ 66 $ 57 $ 88 $ 26 $ 14 $ 8 Taxes accrued 293 186 63 4 23 77 56 3 23 Interest accrued 915 77 443 35 27 54 23 8 13 Severance accrued 21 11 3 — 1 — — — — Other accrued expenses 133 114 14 4 2 47 14 6 26 Total accrued expenses $ 2,376 $ 935 $ 706 $ 109 $ 110 $ 266 $ 119 $ 31 $ 70 _______________________ (a) Primarily includes accrued payroll, bonuses and other incentives, vacation and benefits.

Segment Information (All Regist

Segment Information (All Registrants)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Segment Information (All Registrants)	Segment Information (All Registrants) Operating segments for each of the Registrants are determined based on information used by the chief operating decision maker(s) (CODM) in deciding how to evaluate performance and allocate resources at each of the Registrants. In the first quarter of 2016, following the consummation of the PHI Merger, three new reportable segments were added: Pepco, DPL and ACE. As a result, Exelon has twelve reportable segments, which include ComEd, PECO, BGE, PHI's three reportable segments consisting of Pepco, DPL, and ACE, and Generation’s six reportable segments consisting of the Mid-Atlantic, Midwest, New England, New York, ERCOT and all other power regions referred to collectively as “Other Power Regions”, which includes activities in the South, West and Canada. ComEd, PECO, BGE, Pepco, DPL and ACE each represent a single reportable segment, and as such, no separate segment information is provided for these Registrants. Exelon, ComEd, PECO, BGE, Pepco, DPL and ACE's CODMs evaluate the performance of and allocate resources to ComEd, PECO, BGE, Pepco, DPL and ACE based on net income and return on equity. Effective with the consummation of the PHI Merger, PHI's reportable segments have changed based on the information used by the CODM to evaluate performance and allocate resources. PHI's reportable segments consist of Pepco, DPL and ACE. PHI's Predecessor periods' segment information has been recast to conform to the current presentation. The reclassification of the segment information did not impact PHI's reported consolidated revenues or net income. PHI's CODM evaluates the performance of and allocates resources to Pepco, DPL and ACE based on net income and return on equity. The basis for Generation's reportable segments is the integrated management of its electricity business that is located in different geographic regions, and largely representative of the footprints of ISO/RTO and/or NERC regions, which utilize multiple supply sources to provide electricity through various distribution channels (wholesale and retail). Generation's hedging strategies and risk metrics are also aligned to these same geographic regions. Descriptions of each of Generation’s six reportable segments are as follows: • Mid-Atlantic represents operations in the eastern half of PJM, which includes New Jersey, Maryland, Virginia, West Virginia, Delaware, the District of Columbia and parts of Pennsylvania and North Carolina. • Midwest represents operations in the western half of PJM, which includes portions of Illinois, Pennsylvania, Indiana, Ohio, Michigan, Kentucky and Tennessee, and the United States footprint of MISO, excluding MISO’s Southern Region, which covers all or most of North Dakota, South Dakota, Nebraska, Minnesota, Iowa, Wisconsin, the remaining parts of Illinois, Indiana, Michigan and Ohio not covered by PJM, and parts of Montana, Missouri and Kentucky. • New England represents the operations within ISO-NE covering the states of Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont. • New York represents operations within ISO-NY, which covers the state of New York in its entirety. • ERCOT represents operations within Electric Reliability Council of Texas, covering most of the state of Texas. • Other Power Regions : • South represents operations in the FRCC, MISO’s Southern Region, and the remaining portions of the SERC not included within MISO or PJM, which includes all or most of Florida, Arkansas, Louisiana, Mississippi, Alabama, Georgia, Tennessee, North Carolina, South Carolina and parts of Missouri, Kentucky and Texas. Generation’s South region also includes operations in the SPP, covering Kansas, Oklahoma, most of Nebraska and parts of New Mexico, Texas, Louisiana, Missouri, Mississippi and Arkansas. • West represents operations in the WECC, which includes California ISO, and covers the states of California, Oregon, Washington, Arizona, Nevada, Utah, Idaho, Colorado and parts of New Mexico, Wyoming and South Dakota. • Canada represents operations across the entire country of Canada and includes AESO, OIESO and the Canadian portion of MISO. The CODMs for Exelon and Generation evaluate the performance of Generation’s electric business activities and allocate resources based on revenues net of purchased power and fuel expense (RNF). Generation believes that RNF is a useful measurement of operational performance. RNF is not a presentation defined under GAAP and may not be comparable to other companies’ presentations or deemed more useful than the GAAP information provided elsewhere in this report. Generation’s operating revenues include all sales to third parties and affiliated sales to the Utility Registrants. Purchased power costs include all costs associated with the procurement and supply of electricity including capacity, energy and ancillary services. Fuel expense includes the fuel costs for Generation’s owned generation and fuel costs associated with tolling agreements. The results of Generation's other business activities are not regularly reviewed by the CODM and are therefore not classified as operating segments or included in the regional reportable segment amounts. These activities include natural gas, as well as other miscellaneous business activities that are not significant to Generation's overall operating revenues or results of operations. Further, Generation’s unrealized mark-to-market gains and losses on economic hedging activities and its amortization of certain intangible assets and liabilities relating to commodity contracts recorded at fair value from mergers and acquisitions are also excluded from the regional reportable segment amounts. Exelon and Generation do not use a measure of total assets in making decisions regarding allocating resources to or assessing the performance of these reportable segments. An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements for the years ended December 31, 2016 , 2015 , and 2014 is as follows: Successor Generation (a) ComEd PECO BGE PHI (e) Other (b) Intersegment Eliminations Exelon Operating revenues (c) : 2016 Competitive businesses electric revenues $ 15,390 $ — $ — $ — $ — $ — $ (1,430 ) $ 13,960 Competitive businesses natural gas revenues 2,146 — — — — — — 2,146 Competitive businesses other revenues 215 — — — — — (4 ) 211 Rate-regulated electric revenues — 5,254 2,531 2,609 3,506 — (31 ) 13,869 Rate-regulated natural gas revenues — — 463 624 92 — (13 ) 1,166 Shared service and other revenues — — — — 45 1,648 (1,686 ) 7 2015 Competitive businesses electric revenues $ 15,944 $ — $ — $ — $ — $ — $ (744 ) $ 15,200 Competitive businesses natural gas revenues 2,433 — — — — — — 2,433 Competitive businesses other revenues 758 — — — — — (1 ) 757 Rate-regulated electric revenues — 4,905 2,486 2,490 — — (5 ) 9,876 Rate-regulated natural gas revenues — — 546 645 — — (15 ) 1,176 Shared service and other revenues — — — — — 1,372 (1,367 ) 5 2014 Competitive businesses electric revenues $ 14,533 $ — $ — $ — $ — $ — $ (760 ) $ 13,773 Competitive businesses natural gas revenues 2,705 — — — — — (1 ) 2,704 Competitive businesses other revenues 155 — — — — — (1 ) 154 Rate-regulated electric revenues — 4,564 2,448 2,460 — — (5 ) 9,467 Rate-regulated natural gas revenues — — 646 705 — — (26 ) 1,325 Shared service and other revenues — — — — — 1,285 (1,279 ) 6 Intersegment revenues (d) : 2016 $ 1,428 $ 15 $ 8 $ 21 $ 45 $ 1,647 $ (3,159 ) $ 5 2015 745 4 2 14 — 1,367 (2,127 ) 5 2014 762 4 2 25 — 1,280 (2,067 ) 6 Depreciation and amortization: 2016 $ 1,879 $ 775 $ 270 $ 423 $ 515 $ 74 $ — $ 3,936 2015 1,054 707 260 366 — 63 — 2,450 2014 967 687 236 371 — 53 — 2,314 Operating expenses (c) : 2016 $ 16,856 $ 4,056 $ 2,292 $ 2,683 $ 3,549 $ 1,928 $ (3,164 ) $ 28,200 2015 16,872 3,889 2,404 2,578 — 1,444 (2,131 ) 25,056 2014 16,923 3,586 2,522 2,726 — 1,353 (2,071 ) 25,039 Equity in earnings (losses) of unconsolidated affiliates: 2016 $ (25 ) $ — $ — $ — $ — $ 1 $ — $ (24 ) 2015 (8 ) — — — — 1 — (7 ) 2014 (20 ) — — — — — — (20 ) Interest expense, net: 2016 $ 364 $ 461 $ 123 $ 103 $ 195 $ 290 $ — $ 1,536 2015 365 332 114 99 — 123 — 1,033 2014 356 321 113 106 — 169 — 1,065 Income (loss) before income taxes: 2016 $ 873 $ 679 $ 587 $ 468 $ (58 ) $ (555 ) $ (5 ) $ 1,989 2015 1,850 706 521 477 — (219 ) (5 ) 3,330 2014 1,226 676 466 351 — (227 ) (6 ) 2,486 Income taxes: 2016 $ 290 $ 301 $ 149 $ 174 $ 3 $ (156 ) $ — $ 761 2015 502 280 143 189 — (41 ) — 1,073 2014 207 268 114 140 — (63 ) — 666 Net income (loss): 2016 $ 558 $ 378 $ 438 $ 294 $ (61 ) $ (398 ) $ (5 ) $ 1,204 2015 1,340 426 378 288 — (177 ) (5 ) 2,250 2014 1,019 408 352 211 — (164 ) (6 ) 1,820 Capital expenditures: 2016 $ 3,078 $ 2,734 $ 686 $ 934 $ 1,008 $ 113 $ — $ 8,553 2015 3,841 2,398 601 719 — 65 — 7,624 2014 3,012 1,689 661 620 — 95 — 6,077 Total assets: 2016 $ 46,974 $ 28,335 $ 10,831 $ 8,704 $ 21,025 $ 10,369 $ (11,334 ) $ 114,904 2015 46,529 26,532 10,367 8,295 — 15,389 (11,728 ) 95,384 __________________________ (a) Generation includes the six reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. For the year ended December 31, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $ 290 million , sales to BGE of $ 608 million , sales to Pepco of $295 million , sales to DPL of $154 million and sales to ACE of $37 million in the Mid-Atlantic region, and sales to ComEd of $ 47 million in the Midwest region, which eliminate upon consolidation. For the year ended December 31, 2015 , intersegment revenues for Generation include revenue from sales to PECO of $ 224 million and sales to BGE of $ 502 million in the Mid-Atlantic region, and sales to ComEd of $ 18 million in the Midwest region, which eliminate upon consolidation. For the year ended December 31, 2014 , intersegment revenues for Generation include revenue from sales to PECO of $ 198 million and sales to BGE of $ 387 million in the Mid-Atlantic region, and sales to ComEd of $ 176 million in the Midwest region, net of $ 7 million related to the unrealized mark-to-market losses related to the ComEd swap, which eliminate upon consolidation. (b) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (c) For the years ended December 31, 2016 , 2015 and 2014 , utility taxes of $122 million , $105 million and $89 million , respectively, are included in revenues and expenses for Generation. For the years ended December 31, 2016 , 2015 and 2014 , utility taxes of $242 million , $236 million and $238 million , respectively, are included in revenues and expenses for ComEd. For the years ended December 31, 2016 , 2015 and 2014 , utility taxes of $136 million , $133 million and $128 million , respectively, are included in revenues and expenses for PECO. For the years ended December 31, 2016 , 2015 and 2014 , utility taxes of $85 million , $85 million and $86 million are included in revenues and expenses for BGE, respectively. (d) Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in operating revenues in the Consolidated Statements of Operations and Comprehensive Income. (e) Amounts included represent activity for PHI's successor period, March 24, 2016 through December 31, 2016 . PHI includes the three reportable segments: Pepco, DPL and ACE. See tables below for PHI's predecessor periods, including Pepco, DPL and ACE, for January 1, 2016 to March 23, 2016 and for the years ended December 31, 2015 and December 31, 2014 . Successor and Predecessor PHI: Pepco DPL ACE Other (b) Intersegment PHI Operating revenues (a) : March 24, 2016 to December 31, 2016 - Successor Rate-regulated electric revenues $ 1,675 $ 850 $ 989 $ 5 $ (13 ) $ 3,506 Rate-regulated natural gas revenues — 92 — — — 92 Shared service and other revenues — — — 45 — 45 January 1, 2016 to March 23, 2016 - Predecessor Rate-regulated electric revenues $ 511 $ 279 $ 268 $ 42 $ (4 ) $ 1,096 Rate-regulated natural gas revenues — 56 — 1 — 57 Shared service and other revenues — — — — — — December 31, 2015 - Predecessor Rate-regulated electric revenues $ 2,129 $ 1,138 $ 1,295 $ 210 $ (2 ) $ 4,770 Rate-regulated natural gas revenues — 164 — 1 — 165 Shared service and other revenues — — — — — — December 31, 2014 - Predecessor Rate-regulated electric revenues $ 2,055 $ 1,088 $ 1,210 $ 264 $ (3 ) $ 4,614 Rate-regulated natural gas revenues — 194 — — — 194 Shared service and other revenues — — — — — — Intersegment revenues: March 24, 2016 to December 31, 2016 - Successor $ 4 $ 5 $ 2 $ 47 $ (13 ) $ 45 January 1, 2016 to March 23, 2016 - Predecessor 1 2 1 — (4 ) — December 31, 2015 - Predecessor 5 6 4 — (15 ) — December 31, 2014 - Predecessor 5 7 4 — (16 ) — Depreciation and amortization: March 24, 2016 to December 31, 2016 - Successor $ 224 $ 120 $ 128 $ 43 $ — $ 515 January 1, 2016 to March 23, 2016 - Predecessor 71 37 37 11 (4 ) 152 December 31, 2015 - Predecessor 256 148 175 45 — 624 December 31, 2014 - Predecessor 212 122 155 38 (1 ) 526 Operating expenses: March 24, 2016 to December 31, 2016 - Successor $ 1,577 $ 952 $ 1,000 $ 33 $ (13 ) $ 3,549 January 1, 2016 to March 23, 2016 - Predecessor 443 284 251 73 (3 ) 1,048 December 31, 2015 - Predecessor 1,790 1,137 1,161 220 — 4,308 December 31, 2014 - Predecessor 1,706 1,075 1,073 350 (1 ) 4,203 Interest expense, net: March 24, 2016 to December 31, 2016 - Successor $ 98 $ 38 $ 47 $ 12 $ — $ 195 January 1, 2016 to March 23, 2016 - Predecessor 29 12 15 11 (2 ) 65 December 31, 2015 - Predecessor 124 50 64 43 (1 ) 280 December 31, 2014 - Predecessor 115 48 64 42 — 269 Income (loss) before income taxes: March 24, 2016 to December 31, 2016 - Successor $ 36 $ (30 ) $ (51 ) $ (84 ) $ 71 $ (58 ) January 1, 2016 to March 23, 2016 - Predecessor 47 43 5 59 (118 ) 36 December 31, 2015 - Predecessor 289 125 73 23 (29 ) 481 December 31, 2014 - Predecessor 264 169 76 306 (435 ) 380 Income taxes: March 24, 2016 to December 31, 2016 - Successor $ 26 $ 5 $ (5 ) $ (23 ) $ — $ 3 January 1, 2016 to March 23, 2016 - Predecessor 15 17 1 (16 ) — 17 December 31, 2015 - Predecessor 102 49 33 (48 ) 27 163 December 31, 2014 - Predecessor 93 65 30 (228 ) 178 138 Net income (loss): March 24, 2016 to December 31, 2016 - Successor $ 10 $ (35 ) $ (47 ) $ (34 ) $ 45 $ (61 ) January 1, 2016 to March 23, 2016 - Predecessor 32 26 5 (44 ) — 19 December 31, 2015 - Predecessor 187 76 40 25 (1 ) 327 December 31, 2014 - Predecessor 171 104 46 (78 ) (1 ) 242 Capital Expenditures: March 24, 2016 to December 31, 2016 - Successor $ 489 $ 277 $ 218 $ 24 $ — $ 1,008 January 1, 2016 to March 23, 2016 - Predecessor 97 72 93 11 — 273 December 31, 2015 - Predecessor 544 352 300 34 — 1,230 December 31, 2014 - Predecessor 567 352 225 79 — 1,223 Total assets: December 31, 2016 - Successor $ 7,335 $ 4,153 $ 3,457 $ 10,804 $ (4,724 ) $ 21,025 December 31, 2015 - Predecessor 6,908 3,969 3,387 7,162 (5,238 ) 16,188 _________ (a) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 25 — Supplemental Financial Information for total utility taxes for the year ended December 31, 2016 and 2015 (b) Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities. For the predecessor periods presented, Other includes the activity of PHI’s unregulated businesses which were distributed to Exelon and Generation as a result of the PHI Merger. Generation total revenues: 2016 2015 2014 Revenues from external customers (b) Intersegment revenues Total revenues Revenues from external customers (b) Intersegment revenues Total revenues Revenues from external customers (b)(d) Intersegment revenues (d) Total revenues Mid-Atlantic (a) $ 6,212 $ (33 ) $ 6,179 $ 5,974 $ (74 ) $ 5,900 $ 5,414 $ (155 ) $ 5,259 Midwest 4,402 10 4,412 4,712 (2 ) 4,710 4,488 (13 ) 4,475 New England 1,778 (9 ) 1,769 2,217 (5 ) 2,212 1,468 (46 ) 1,422 New York (a) 1,198 (42 ) 1,156 996 (11 ) 985 846 (3 ) 843 ERCOT 831 6 837 863 (6 ) 857 938 (3 ) 935 Other Power Regions 969 (62 ) 907 1,182 (80 ) 1,102 1,379 (70 ) 1,309 Total Revenues for Reportable Segments $ 15,390 $ (130 ) $ 15,260 $ 15,944 $ (178 ) $ 15,766 $ 14,533 $ (290 ) $ 14,243 Other (c) 2,361 130 2,491 3,191 178 3,369 2,860 290 3,150 Total Generation Consolidated Operating Revenues $ 17,751 $ — $ 17,751 $ 19,135 $ — $ 19,135 $ 17,393 $ — $ 17,393 _______________________ (a) On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, beginning on April 1, 2014, CENG's revenues are included on a fully consolidated basis. (b) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $52 million decrease to revenues, a $ 7 million increase to revenues, and a $ 289 million decrease to revenues for the amortization of intangible assets related to commodity contracts recorded at fair value for the years ended December 31, 2016 , 2015 , and 2014 , respectively, unrealized mark-to-market losses of $500 million , gains of $203 million , and losses of $174 million for the years ended December 31, 2016 , 2015 , and 2014 , respectively, and elimination of intersegment revenues. (d) Exelon corrected an error in the December 31, 2014 balances within Intersegment revenues and Revenues from external customers for an overstatement of Intersegment revenues for Reportable Segments of $284 million for the year ended December 31, 2014, an understatement of Revenues from external customers for Reportable Segments of $284 million for the year ended December 31, 2014, an understatement of Intersegment revenues for Other of $284 million for the year ended December 31, 2014, and an overstatement of Revenues from external customers for Other of $284 million for the year ended December 31, 2014. The error is not considered material to any prior period, and there is no net impact to Total Revenues. Generation total revenues net of purchased power and fuel expense: 2016 2015 2014 RNF from external (b) Intersegment Total RNF RNF from external (b) Intersegment RNF Total RNF RNF from external (b)(d) Intersegment (d) Total RNF Mid-Atlantic (a) $ 3,282 $ 35 $ 3,317 $ 3,556 $ 15 $ 3,571 $ 3,544 $ (113 ) $ 3,431 Midwest 2,969 2 2,971 2,912 (20 ) 2,892 2,607 (8 ) 2,599 New England 467 (29 ) 438 519 (58 ) 461 450 (99 ) 351 New York (a) 761 (19 ) 742 584 50 634 439 44 483 ERCOT 412 (131 ) 281 425 (132 ) 293 573 (256 ) 317 Other Power Regions 483 (147 ) 336 440 (190 ) 250 517 (190 ) 327 Total Revenues net of purchased power and fuel expense for Reportable Segments $ 8,374 $ (289 ) $ 8,085 $ 8,436 $ (335 ) $ 8,101 $ 8,130 $ (622 ) $ 7,508 Other (c) 547 289 836 678 335 1,013 (662 ) 622 (40 ) Total Generation Revenues net of purchased power and fuel expense $ 8,921 $ — $ 8,921 $ 9,114 $ — $ 9,114 $ 7,468 $ — $ 7,468 ____________________________ (a) On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, beginning on April 1, 2014, CENG's revenues net of purchased power and fuel expense are included on a fully consolidated basis. (b) Includes purchases and sales from third parties and affiliated sales to the Utility Registrants. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $57 million decrease in RNF, a $ 8 million increase in RNF, and a $ 124 million decrease in RNF for the amortization of intangible assets related to commodity contracts recorded at fair value for the years ended December 31, 2016 , 2015 , and 2014 , respectively, unrealized mark-to-market losses of $41 million , gains of $257 million , and losses of $591 million for the years ended December 31, 2016 , 2015 , and 2014 , respectively, accelerated nuclear fuel amortization associated with the initial early retirement decision for Clinton and Quad Cities as discussed in Note 9 - Early Nuclear Plant Retirements of $60 million for the year ended December 31, 2016, and the elimination of intersegment revenues net of purchased power and fuel expense. (d) Exelon corrected an error in the December 31, 2014 balances within Intersegment RNF and RNF from external customers for an understatement of $8 million of Intersegment RNF for Reportable Segments for the year ended December 31, 2014, an understatement of RNF from external customers for Reportable Segments of $11 million for the year ended December 31, 2014, an overstatement of $8 million of Intersegment RNF for Other for the year ended December 31, 2014, and an overstatement of RNF from external customers for Other of $11 million for the year ended December 31, 2014. This also included an understatement of total RNF for Reportable Segments and an overstatement of total RNF for Other of $19 million for the year ended December 31, 2014. The error is not considered material to any prior period, and there is no net impact to Generation Total RNF for 2014.

Related Party Transactions (All

Related Party Transactions (All Registrants)	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
Related-Party Transactions (All Registrants)	(All Registrants) Exelon The financial statements of Exelon include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: PECO (a) $ 1 $ 1 $ 1 CENG (b) — — 17 BGE (a) 4 4 5 Other 5 4 — Total operating revenues from affiliates $ 10 $ 9 $ 23 Purchase power and fuel from affiliates: CENG (c) $ — $ — $ 282 Keystone Fuels, LLC (d) — — 138 Conemaugh Fuels, LLC (d) — — 99 Safe Harbor Water Power Corp (d) — — 12 Total purchase power and fuel from affiliates $ — $ — $ 531 Interest expense to affiliates, net: ComEd Financing III $ 13 $ 13 $ 13 PECO Trust III 6 6 6 PECO Trust IV 6 6 6 BGE Capital Trust II 16 16 16 Total interest expense to affiliates, net $ 41 $ 41 $ 41 Earnings (losses) in equity method investments: CENG (e) $ — $ — $ (19 ) Qualifying facilities and domestic power projects (25 ) (8 ) (1 ) Other 1 1 — Total losses in equity method investments $ (24 ) $ (7 ) $ (20 ) December 31, 2016 2015 Payables to affiliates (current): ComEd Financing III $ 4 $ 4 PECO Trust III 1 1 BGE Capital Trust II 3 3 Total payables to affiliates (current) $ 8 $ 8 Long-term debt due to financing trusts: ComEd Financing III $ 205 $ 205 PECO Trust III 81 81 PECO Trust IV 103 103 BGE Capital Trust II 252 252 Total long-term debt due to financing trusts $ 641 $ 641 ____________________________ (a) The intersegment profit associated with the sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in operating revenues in the Consolidated Statements of Operations. See Note 3 — Regulatory Matters for additional information. (b) Beginning in 2012, Generation entered into a power services agency agreement (PSAA) with the CENG plants, which as of April 1, 2014, was amended and extended until the permanent cessation of power generation by the CENG generation plants. The PSAA is an agreement under which Generation provides scheduling, asset management and billing services to the CENG plants for a specified monthly fee. The charges for services reflect the cost of the services. On April 1, 2014, Generation and CENG entered into a Nuclear Operating Services Agreement (NOSA) pursuant to which Generation will operate the CENG nuclear generation fleet owned by CENG subsidiaries and provide corporate and administrative services for the remaining life of the CENG nuclear plants as if they were part of the Generation nuclear fleet. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . (c) CENG owns 100% of four nuclear units in Maryland and New York and 82% of Nine Mile Point Unit 2 in New York. Beginning in 2012, Generation had a PPA under which it purchased 85% of the nuclear plant output owned by CENG that was not sold to third parties under pre-existing unit-contingent PPAs through 2014. Beginning on January 1, 2015 and continuing to the end of the life of the respective plants, Generation will purchase on a unit-contingent basis 50.01% of the nuclear plant output owned by CENG and a subsidiary of EDF will purchase on a unit-contingent basis 49.99% of the nuclear plant output owned by CENG (EDF PPA) not sold to third parties. Beginning April 1, 2014, sales to Generation are eliminated in consolidation. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . (d) During 2014, Generation closed the sale of Safe Harbor Water Power Corporation, Keystone Fuels, LLC, and Conemaugh Fuels LLC. Generation recorded purchase power and fuel costs from affiliates related to these generating assets during the time these assets were still partially owned by Generation. See Note 4 — Mergers, Acquisitions, and Dispositions for more information. (e) Prior to April 1, 2014, Generation’s total gain (loss) in equity method investments includes equity investment income (loss) and amortization of the basis difference established as a result of purchase accounting applied upon Constellation merger in 2012. CENG was fully consolidated on April 1, 2014. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . Transactions involving Generation, ComEd, PECO,BGE, PHI, Pepco, DPL and ACE are further described in the tables below. Generation The financial statements of Generation include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: ComEd (a) $ 47 $ 18 $ 176 PECO (b) 290 224 198 BGE (c) 608 502 387 Pepco (d) 295 — — DPL (e) 154 — — ACE (f) 37 — — CENG (g) — — 17 BSC 2 1 1 Other 6 4 — Total operating revenues from affiliates $ 1,439 $ 749 $ 779 Purchase power and fuel from affiliates: ComEd $ — $ — $ 1 BGE 12 14 25 CENG (h) — — 282 Keystone Fuels, LLC (l) — — 138 Conemaugh Fuels, LLC (l) — — 99 Safe Harbor Water Power Corporation (l) — — 12 Total purchase power and fuel from affiliates $ 12 $ 14 $ 557 Operating and maintenance from affiliates: ComEd (i) $ 7 $ 4 $ 3 PECO (i) 3 2 2 BGE (i) 1 — — PHI 1 — — Pepco 1 — — BSC (j) 650 614 618 Total operating and maintenance from affiliates $ 663 $ 620 $ 623 Interest expense to affiliates, net: Exelon Corporate (m) $ 39 $ 43 $ 53 Earnings (losses) in equity method investments CENG (k) $ — $ — $ (19 ) Qualifying facilities and domestic power projects (25 ) (8 ) (1 ) Total losses in equity method investments $ (25 ) $ (8 ) $ (20 ) Capitalized costs BSC (j) $ 98 $ 76 $ 91 Cash distribution paid to member $ 922 $ 2,474 $ 645 Contribution from member $ 142 $ 47 $ 53 December 31, 2016 2015 Receivables from affiliates (current): ComEd (a) $ 14 $ 15 PECO (b) 33 36 BGE (c) 26 31 Pepco (d) 44 — DPL (e) 16 — ACE (f) 9 — PHISCO (j) 5 — PCI 8 — Other 1 1 Total receivables from affiliates (current) $ 156 $ 83 Intercompany money pool (current): Exelon Corporate $ — $ 1,252 PCI 55 — Total intercompany money pool (current) $ 55 $ 1,252 Payables to affiliates (current): Exelon Corporate (m) $ 22 $ 16 BSC (j) 99 78 ComEd 9 9 Other 7 1 Total payables to affiliates (current) $ 137 $ 104 Long-term debt due to affiliates (noncurrent): Exelon Corporate (o) $ 922 $ 933 Payables to affiliates (noncurrent): BSC (g) $ 1 $ — ComEd (n) 2,169 2,172 PECO (n) 438 405 Total payables to affiliates (noncurrent) $ 2,608 $ 2,577 _______________________ (a) Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs to ComEd. In addition, Generation had revenue from ComEd associated with the settled portion of the financial swap contract established as part of the Illinois Settlement. See Note 3 — Regulatory Matters for additional information. (b) Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has a ten-year agreement with PECO to sell solar AECs. See Note 3 — Regulatory Matters for additional information. (c) Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs. See Note 3 — Regulatory Matters for additional information. (d) Generation provides electric supply to Pepco under contracts executed through Pepco's competitive procurement process approved by the MDPSC and DCPSC. See Note 3 — Regulatory Matters for additional information. (e) Generation provides a portion of DPL's energy requirements under its MDPSC and DPSC approved market based SOS and gas commodity programs. See Note 3 — Regulatory Matters for additional information. (f) Generation provides electric supply to ACE under contracts executed through ACE's competitive procurement process. See Note 3 — Regulatory Matters for additional information. (g) Beginning in 2012, Generation entered into a power services agency agreement (PSAA) with the CENG plants, which as of April 1, 2014, was amended and extended until the permanent cessation of power generation by the CENG generation plants. The PSAA is an agreement under which Generation provides scheduling, asset management and billing services to the CENG plants for a specified monthly fee. The charges for services reflect the cost of the services. On April 1, 2014, Generation and CENG entered into a Nuclear Operating Services Agreement (NOSA) pursuant to which Generation will operate the CENG nuclear generation fleet owned by CENG subsidiaries and provide corporate and administrative services for the remaining life of the CENG nuclear plants as if they were part of the Generation nuclear fleet. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . (h) CENG owns 100% of four nuclear units in Maryland and New York and 82% of Nine Mile Point Unit 2 in New York. Beginning in 2012, Generation had a PPA under which it purchased 85% of the nuclear plant output owned by CENG that was not sold to third parties under pre-existing unit-contingent PPAs through 2014. Beginning on January 1, 2015 and continuing to the end of the life of the respective plants, Generation will purchase on a unit-contingent basis 50.01% of the nuclear plant output owned by CENG and a subsidiary of EDF will purchase on a unit-contingent basis 49.99% of the nuclear plant output owned by CENG (EDF PPA) not sold to third parties. Beginning April 1, 2014, sales to Generation are eliminated in consolidation. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . (i) Generation requires electricity for its own use at its generating stations. Generation purchases electricity and distribution and transmission services from PECO and BGE and only distribution and transmission services from ComEd for the delivery of electricity to its generating stations. (j) Generation receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. (k) Prior to April 1, 2014, Generation’s total gain (loss) in equity method investments includes equity income (loss) and amortization of the basis difference established as a result of purchase accounting applied upon Constellation merger in 2012. CENG was fully consolidated on April 1, 2014. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . (l) During 2014, Generation closed the sale of Safe Harbor Water Power Corporation, Keystone Fuels, LLC, and Conemaugh Fuels LLC. Generation recorded purchase power and fuel costs from affiliates related to these generating assets during the time these assets were still partially owned by Generation. See Note 4 — Mergers, Acquisitions, and Dispositions for more information. (m) The balance consists of interest owed to Exelon Corporation related to the senior unsecured notes, as well as, expense related to certain invoices Exelon Corporation processed on behalf of Generation. (n) Generation has long-term payables to ComEd and PECO as a result of the nuclear decommissioning contractual construct whereby, to the extent NDT funds are greater than the underlying ARO at the end of decommissioning, such amounts are due back to ComEd and PECO, as applicable, for payment to their respective customers. See Note 16 — Asset Retirement Obligations . (o) In connection with the debt obligations assumed by Exelon as part of the Constellation merger, Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable included in Long-term Debt to affiliate on Generation’s Consolidated Balance Sheets and intercompany notes receivable at Exelon Corporate, which are eliminated in consolidation on Exelon’s Consolidated Balance Sheets. ComEd The financial statements of ComEd include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates Generation $ 7 $ 4 $ 4 BSC 6 — — PECO 1 — — BGE 1 — — Total operating revenues from affiliates $ 15 $ 4 $ 4 Purchased power from affiliate Generation (a) $ 47 $ 18 $ 176 Operating and maintenance from affiliates BSC (b) $ 225 $ 195 $ 166 PECO 1 — — BGE 1 — — Total operating and maintenance from affiliates 227 195 166 Interest expense to affiliates, net: ComEd Financing III $ 13 $ 13 $ 13 Capitalized costs BSC (b) $ 112 $ 103 $ 77 Cash dividends paid to parent $ 369 $ 299 $ 307 Contribution from parent $ 315 $ 202 $ 273 December 31, 2016 2015 Prepaid voluntary employee beneficiary association trust (c) $ 5 $ 11 Receivable from affiliates (current): Voluntary employee beneficiary association trust $ 2 $ 2 Generation 9 9 Exelon Corporate (e) 345 188 Total receivable from affiliates (current) $ 356 $ 199 Receivable from affiliates (noncurrent): Generation (d) $ 2,169 $ 2,172 Other 1 — Total receivable from affiliates (noncurrent) $ 2,170 $ 2,172 Payables to affiliates (current): Generation (a) $ 14 $ 15 BSC (b) 42 39 ComEd Financing III 4 4 PECO 2 2 Exelon Corporate 3 2 Total payables to affiliates (current) $ 65 $ 62 Long-term debt to ComEd financing trust ComEd Financing III $ 205 $ 205 _______________________ (a) ComEd procures a portion of its electricity supply requirements from Generation under an ICC-approved RFP contract. ComEd also purchases RECs from Generation. In addition, purchased power expense includes the settled portion of the financial swap contract with Generation, which expired in 2013. See Note 3 — Regulatory Matters and Note 13 — Derivative Financial Instruments for additional information. (b) ComEd receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. (c) The voluntary employee benefit association trusts covering active employees are included in corporate operations and are funded by the Registrants. A prepayment to the active welfare plans has accumulated due to actuarially determined contribution rates, which are the basis for ComEd’s contributions to the plans, being higher than actual claim expense incurred by the plans over time. The prepayment is included in other current assets. (d) ComEd has a long-term receivable from Generation as a result of the nuclear decommissioning contractual construct for generating facilities previously owned by ComEd. To the extent the assets associated with decommissioning are greater than the applicable ARO at the end of decommissioning, such amounts are due back to ComEd for payment to ComEd’s customers. (e) Represents indemnification from Exelon Corporate related to the like-kind exchange. PECO The financial statements of PECO include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: Generation (a) $ 3 $ 2 $ 2 BSC 3 — — ComEd 1 — — BGE 1 — — Total operating revenues from affiliates $ 8 $ 2 $ 2 Purchased power from affiliate Generation (b) $ 287 $ 220 $ 194 Operating and maintenance from affiliates: BSC (c) $ 142 $ 107 $ 96 Generation 2 3 3 ComEd 1 — — BGE 1 — $ — Total operating and maintenance from affiliates $ 146 $ 110 $ 99 Interest expense to affiliates, net: PECO Trust III $ 6 $ 6 $ 6 PECO Trust IV 6 6 6 Total interest expense to affiliates, net $ 12 $ 12 $ 12 Capitalized costs BSC (c) $ 57 $ 40 $ 39 Cash dividends paid to parent $ 277 $ 279 $ 320 Contribution from parent $ 18 $ 16 $ 24 December 31, 2016 2015 Prepaid voluntary employee beneficiary association trust (d) $ 1 $ 2 Receivable from affiliate (current): ComEd $ 2 $ 2 BGE 2 — Total receivable from affiliates (current) $ 4 $ 2 Receivable from affiliate (noncurrent): Generation (e) $ 438 $ 405 Payables to affiliates (current): Generation (b) $ 33 $ 36 BSC (c) 28 17 Exelon Corporate 1 1 PECO Trust III 1 1 Total payables to affiliates (current) $ 63 $ 55 Long-term debt to financing trusts: PECO Trust III $ 81 $ 81 PECO Trust IV 103 103 Total long-term debt to financing trusts $ 184 $ 184 ________________________ (a) PECO provides energy to Generation for Generation’s own use. (b) PECO purchases electric supply from Generation under contracts executed through its competitive procurement process. In addition, PECO has five-year and ten-year agreements with Generation to purchase non-solar and solar AECs, respectively. See Note 3 — Regulatory Matters for additional information on AECs. (c) PECO receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. (d) The voluntary employee beneficiary association trusts covering active employees are included in corporate operations and are funded by the Registrants. A prepayment to the active welfare plans has accumulated due to actuarially determined contribution rates, which are the basis for PECO’s contributions to the plans, being higher than actual claim expense incurred by the plans over time. (e) PECO has a long-term receivable from Generation as a result of the nuclear decommissioning contractual construct, whereby, to the extent the assets associated with decommissioning are greater than the applicable ARO at the end of decommissioning, such amounts are due back to PECO for payment to PECO’s customers. BGE The financial statements of BGE include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: Generation (a) $ 13 $ 14 $ 25 BSC 6 — — ComEd 1 — — PECO 1 — — Total operating revenues from affiliates $ 21 $ 14 $ 25 Purchased power from affiliate Generation (b) $ 604 $ 498 $ 382 Operating and maintenance from affiliates: BSC (c) $ 130 $ 118 $ 103 ComEd 1 — — PECO 1 — — Total operating and maintenance from affiliates $ 132 $ 118 $ 103 Interest expense to affiliates, net: BGE Capital Trust II $ 16 $ 16 $ 16 Capitalized costs BSC (c) $ 36 $ 28 $ 19 Cash dividends paid to parent $ 179 $ 158 $ — Contribution from parent $ 61 $ 7 $ — December 31, 2016 2015 Payables to affiliates (current): Generation (b) $ 26 $ 31 BSC (c) 22 17 Exelon Corporate 1 1 PECO 2 — BGE Capital Trust II 3 3 Other 1 — Total payables to affiliates (current) $ 55 $ 52 Long-term debt to BGE financing trust BGE Capital Trust II $ 252 $ 252 ______________________ (a) BGE provides energy to Generation for Generation’s own use. (b) BGE procures a portion of its electricity and gas supply requirements from Generation under its MDPSC-approved market-based SOS and gas commodity programs. See Note 3 — Regulatory Matters for additional information. (c) BGE receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. PHI The financial statements of PHI include related party transactions as presented in the tables below: Successor March 24, 2016 to December 31, 2016 Operating revenues from affiliates: BSC $ 44 Generation 1 Total operating revenues from affiliates $ 45 Purchased power from affiliate Generation $ 486 Operating and maintenance from affiliates: BSC $ 86 PCI 3 Total operating and maintenance from affiliates $ 89 Cash dividends paid to parent $ 273 Contribution from member $ 1,251 December 31, 2016 Successor Payables to affiliates (current): Generation $ 74 BSC 10 Exelon Corporate 6 PHI Corporate 4 Total payables to affiliates (current) $ 94 Pepco The financial statements of Pepco include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: Generation (a) $ 1 $ — $ — PHISCO 4 5 5 Total operating revenues from affiliates $ 5 $ 5 $ 5 Purchased power from affiliate Generation (b) $ 295 $ — $ — Operating and maintenance: PHISCO (c) $ 263 $ 240 $ 220 PES (d) 39 26 30 Total operating and maintenance $ 302 $ 266 $ 250 Operating and maintenance from affiliates: BSC (c) $ 31 $ — $ — PHISCO (c) 4 4 4 Total operating and maintenance from affiliates $ 35 $ 4 $ 4 Cash dividends paid to parent $ 136 $ 146 $ 86 Contribution from parent $ 187 $ 112 $ 80 December 31, 2016 2015 Payables to affiliates (current): Generation (b) $ 44 $ — BSC (c) 4 — DPL 1 — PHISCO (c) 25 25 PES (e) — 4 Other — 1 Total payables to affiliates (current) $ 74 $ 30 ______________________ (a) Pepco provides energy to Generation for Generation’s own use. (b) Pepco procures a portion of its electricity and gas supply requirements from Generation under its MDPSC and DPSC approved market based SOS and gas commodity programs. See Note 3 — Regulatory Matters for additional information. (c) Pepco receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. (d) PES performs underground transmission, distribution construction and maintenance services, including services that are treated as capital costs, for Pepco. (e) Pepco bills customers on behalf of PES where PES has performed work for certain government agencies under a General Services Administration area-wide agreement on behalf of Pepco. DPL The financial statements of DPL include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: PHISCO $ 5 $ 5 $ 6 Other 2 1 1 Total operating revenues from affiliates $ 7 $ 6 $ 7 Purchased power from affiliate Generation (a) $ 154 $ — $ — Operating and maintenance: PHISCO (b) $ 194 $ 179 $ 163 PES (c) 8 3 — Total operating and maintenance $ 202 $ 182 $ 163 Operating and maintenance from affiliates: BSC (b) $ 18 $ — $ — Other 1 1 1 Total operating and maintenance from affiliates $ 19 $ 1 $ 1 Cash dividends paid to parent $ 54 $ 92 $ 100 Contribution from parent $ 152 $ 75 $ 130 December 31, 2016 2015 Receivables from affiliates (current): Pepco $ 1 $ — ACE 2 — Total receivable from affiliates (current) $ 3 $ — Payables to affiliates (current): Generation (a) $ 16 $ — BSC (b) 3 — PHISCO (b) 19 19 Other — 1 Total payables to affiliates (current) $ 38 $ 20 ______________________ (a) DPL procures a portion of its electricity and gas supply requirements from Generation under its MDPSC and DPSC approved market based SOS and gas commodity programs. See Note 3 — Regulatory Matters for additional information. (b) DPL receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. (c) PES performs underground transmission construction services, including services that are treated as capital costs, for DPL. ACE The financial statements of ACE include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: PHISCO $ 2 $ 2 $ 1 Other 1 2 3 Total operating revenues from affiliates $ 3 $ 4 $ 4 Purchased power from affiliate Generation (a) $ 37 $ — $ — Operating and maintenance: PHISCO (b) $ 155 $ 143 $ 124 Operating and maintenance from affiliates: BSC (b) $ 15 $ — $ — Other 3 3 3 Total operating and maintenance from affiliates $ 18 $ 3 $ 3 Cash dividends paid to parent $ 63 $ 12 $ 26 Contribution from parent $ 139 $ 95 $ — December 31, 2016 2015 Payables to affiliates (current): Generation (a) $ 9 $ — BSC (b) 2 — DPL 2 — PHISCO (b) 16 15 Other — 1 Total payables to affiliates (current) $ 29 $ 16 ______________________ (a) ACE purchases electric supply from Generation under contracts executed through its competitive procurement process. See Note 3 — Regulatory Matters for additional information. (b) ACE receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.

Quarterly Data (Unaudited) (All

Quarterly Data (Unaudited) (All Registrants)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Quarterly Data (Unaudited) (All Registrants)	(Unaudited) (All Registrants) Exelon The data shown below, which may not equal the total for the year due to the effects of rounding and dilution, includes all adjustments that Exelon considers necessary for a fair presentation of such amounts: Operating Revenues Operating Income Net Income 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 7,573 $ 8,830 $ 483 $ 1,366 $ 173 $ 693 June 30 6,910 6,514 647 1,134 267 638 September 30 9,002 7,401 1,267 1,200 490 629 December 31 7,875 6,702 714 707 204 309 Average Basic Shares Outstanding (in millions) Net Income 2016 2015 2016 2015 Quarter ended: March 31 923 862 $ 0.19 $ 0.80 June 30 924 863 0.29 0.74 September 30 925 913 0.53 0.69 December 31 925 921 0.22 0.34 Average Diluted Shares Outstanding (in millions) Net Income 2016 2015 2016 2015 Quarter ended: March 31 925 867 $ 0.19 $ 0.80 June 30 926 866 0.29 0.74 September 30 927 915 0.53 0.69 December 31 928 924 0.22 0.33 The following table presents the New York Stock Exchange—Composite Common Stock Prices and dividends by quarter on a per share basis: 2016 2015 Fourth Quarter Third Quarter Second Quarter First Quarter Fourth Quarter Third Quarter Second Quarter First Quarter High price $ 36.36 $ 37.70 $ 36.37 $ 35.95 $ 31.37 $ 34.44 $ 34.98 $ 38.25 Low price 29.82 32.86 33.18 26.26 25.09 28.41 31.28 31.71 Close 35.49 33.29 36.36 35.86 27.77 29.70 31.42 33.61 Dividends 0.318 0.318 0.318 0.310 0.310 0.310 0.310 0.310 Generation The data shown below includes all adjustments that Generation considers necessary for a fair presentation of such amounts: Operating Revenues Operating (Loss) Income Net (Loss) Income 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 4,739 $ 5,840 $ 415 $ 719 $ 310 $ 443 June 30 3,589 4,232 (13 ) 703 (8 ) 398 September 30 5,035 4,768 342 622 236 377 December 31 4,388 4,294 94 230 (41 ) 154 ComEd The data shown below includes all adjustments that ComEd considers necessary for a fair presentation of such amounts: Operating Revenues Operating Income Net Income 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 1,249 $ 1,185 $ 274 $ 230 $ 115 $ 90 June 30 1,286 1,148 324 243 145 99 September 30 1,497 1,376 389 327 37 149 December 31 1,223 1,196 217 217 80 87 PECO The data shown below includes all adjustments that PECO considers necessary for a fair presentation of such amounts: Operating Revenues Operating Income Net Income Attributable to Common Shareholders 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 841 $ 985 $ 196 $ 223 $ 124 $ 139 June 30 664 661 152 124 100 70 September 30 788 740 204 154 122 90 December 31 701 645 150 128 92 79 BGE The data shown below includes all adjustments that BGE considers necessary for a fair presentation of such amounts: Operating Revenues Operating Income Net Income Attributable to Common Shareholders 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 929 $ 1,036 $ 187 $ 204 $ 98 $ 106 June 30 680 628 59 99 31 44 September 30 812 725 115 110 54 51 December 31 812 746 190 144 103 74 PHI The data shown below includes all adjustments that PHI considers necessary for a fair presentation of such amounts: Successor Predecessor Successor Predecessor Successor Predecessor Operating Revenues Operating (Loss) Income Net (Loss) Income Membership Interest 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 105 (a) $ 1,354 $ (411 ) (a) $ 142 $ (309 ) (a) $ 53 June 30 1,066 1,119 136 139 52 53 September 30 1,394 1,336 279 184 166 91 December 31 1,078 1,126 90 208 30 130 Predecessor Operating Revenues Operating Income Net Income Attributable to Membership Interest January 1, 2016 - March 23, 2016 1,153 105 19 ____________________________ (a) Amounts for March 31, 2016 reflect the PHI Successor activity for the period March 24, 2016 to March 31, 2016. Pepco The data shown below includes all adjustments that Pepco considers necessary for a fair presentation of such amounts: Operating Revenues Operating (Loss) Income Net (Loss) Income Common Shareholders 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 551 $ 545 $ (105 ) $ 63 $ (108 ) $ 26 June 30 509 504 97 83 49 42 September 30 635 592 132 115 79 60 December 31 491 488 51 123 23 59 DPL The data shown below includes all adjustments that DPL considers necessary for a fair presentation of such amounts: Operating Revenues Operating (Loss) Income Net (Loss) Income 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 362 $ 421 $ (72 ) $ 63 $ (72 ) $ 32 June 30 281 271 30 24 12 8 September 30 331 314 72 32 44 15 December 31 303 296 20 46 7 21 ACE The data shown below includes all adjustments that ACE considers necessary for a fair presentation of such amounts: Operating Revenues Operating (Loss) Income Net (Loss) Income 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 291 $ 334 $ (121 ) $ 29 $ (100 ) $ 9 June 30 270 285 19 25 3 6 September 30 421 386 83 51 47 22 December 31 275 291 26 29 8 3

Schedule I - Condensed Financia

Schedule I - Condensed Financial Information of Parent (Exelon Corporate)	12 Months Ended
	Dec. 31, 2016
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule I - Condensed Financial Information of Parent (Exelon Corporate)	Exelon Corporation and Subsidiary Companies Schedule I – Condensed Financial Information of Parent (Exelon Corporate) Condensed Statements of Operations and Other Comprehensive Income For the Years Ended December 31, (In millions) 2016 2015 2014 Operating expenses Operating and maintenance $ 221 $ — $ 9 Operating and maintenance from affiliates 51 43 38 Other 4 4 3 Total operating expenses 276 47 50 Operating loss (276 ) (47 ) (50 ) Other income and (deductions) Interest expense, net (312 ) (168 ) (237 ) Equity in earnings of investments 1,521 2,461 1,779 Interest income from affiliates, net 39 43 53 Other, net 7 (43 ) (2 ) Total other income 1,255 2,293 1,593 Income before income taxes 979 2,246 1,543 Income taxes (155 ) (23 ) (80 ) Net income $ 1,134 $ 2,269 $ 1,623 Other comprehensive income (loss) Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic costs $ (48 ) $ (46 ) $ (30 ) Actuarial loss reclassified to periodic cost 184 220 147 Pension and non-pension postretirement benefit plan valuation adjustment (181 ) (99 ) (497 ) Unrealized gain (loss) on cash flow hedges 2 9 (148 ) Unrealized gain on marketable securities 1 — 1 Unrealized (loss) gain on equity investments (4 ) (3 ) 8 Unrealized gain (loss) on foreign currency translation 10 (21 ) (9 ) Reversal of CENG equity method AOCI — — (116 ) Other comprehensive (loss) income (36 ) 60 (644 ) Comprehensive income $ 1,098 $ 2,329 $ 979 See Notes to Financial Statements Exelon Corporation and Subsidiary Companies Schedule I – Condensed Financial Information of Parent (Exelon Corporate) Condensed Statements of Cash Flows For the Years Ended December 31, (In millions) 2016 2015 2014 Net cash flows provided by operating activities $ 1,029 $ 3,071 $ 806 Cash flows from investing activities Return on investment of direct financing lease termination — — 335 Changes in Exelon intercompany money pool 1,390 (1,217 ) (83 ) Note receivable from affiliates — 550 — Capital expenditures — — 1 Investment in affiliates (1,757 ) (212 ) (70 ) Acquisition of business (6,962 ) — — Other investing activities 5 (55 ) (126 ) Net cash flows (used in) provided by investing activities (7,324 ) (934 ) 57 Cash flows from financing activities Issuance of long-term debt 1,800 4,200 1,150 Retirement of long-term debt (46 ) (2,263 ) (23 ) Issuance of common stock — 1,868 — Dividends paid on common stock (1,166 ) (1,105 ) (1,065 ) Proceeds from employee stock plans 55 32 35 Other financing activities (20 ) (58 ) (84 ) Net cash flows provided by financing activities 623 2,674 13 (Decrease) Increase in cash and cash equivalents (5,672 ) 4,811 876 Cash and cash equivalents at beginning of period 5,690 879 3 Cash and cash equivalents at end of period $ 18 $ 5,690 $ 879 See Notes to Financial Statements Exelon Corporation and Subsidiary Companies Schedule I – Condensed Financial Information of Parent (Exelon Corporate) Condensed Balance Sheets December 31, (In millions) 2016 2015 ASSETS Current assets Cash and cash equivalents $ 18 $ 5,690 Deposit with IRS 1,250 — Accounts receivable, net Other accounts receivable 73 272 Accounts receivable from affiliates 48 20 Notes receivable from affiliates 88 1,478 Regulatory assets 263 241 Other — 5 Total current assets 1,740 7,706 Property, plant and equipment, net 51 53 Deferred debits and other assets Regulatory assets 4,033 3,072 Investments in affiliates 34,869 26,119 Deferred income taxes 2,107 2,036 Non-pension postretirement benefit asset — 108 Notes receivable from affiliates 922 933 Other 256 404 Total deferred debits and other assets 42,187 32,672 Total assets $ 43,978 $ 40,431 See Notes to Financial Statements Exelon Corporation and Subsidiary Companies Schedule I – Condensed Financial Information of Parent (Exelon Corporate) Condensed Balance Sheets December 31, (In millions) 2016 2015 LIABILITIES AND SHAREHOLDERS’ EQUITY Current liabilities Short-term borrowings $ — $ 188 Long-term debt due within one year 570 60 Accounts payable 2 5 Accrued expenses 489 440 Payables to affiliates 706 — Regulatory liabilities 16 63 Pension obligations 58 52 Other 50 1 Total current liabilities 1,891 809 Long-term debt 7,193 6,017 Deferred credits and other liabilities Regulatory liabilities 31 31 Pension obligations 8,608 7,520 Non-pension postretirement benefit obligations 7 — Deferred income taxes 226 134 Other 182 122 Total deferred credits and other liabilities 9,054 7,807 Total liabilities 18,138 14,633 Commitments and contingencies Shareholders’ equity Common stock (No par value, 2000 shares authorized, 924 shares and 920 shares outstanding at December 31, 2016 and 2015, respectively) 18,797 18,678 Treasury stock, at cost (35 shares at December 31, 2016 and 2015, respectively) (2,327 ) (2,327 ) Retained earnings 12,030 12,068 Accumulated other comprehensive loss, net (2,660 ) (2,624 ) Total shareholders’ equity 25,840 25,795 BGE preference stock not subject to mandatory redemption — 3 Total liabilities and shareholders’ equity $ 43,978 $ 40,431 See Notes to Financial Statements Basis of Presentation Exelon Corporate is a holding company that conducts substantially all of its business operations through its subsidiaries. These condensed financial statements and related footnotes have been prepared in accordance with Rule 12-04, Schedule I of Regulation S-X. These statements should be read in conjunction with the consolidated financial statements and notes thereto of Exelon Corporation. Exelon Corporate owns 100% of all of its significant subsidiaries, either directly or indirectly, except for Commonwealth Edison Company (ComEd), of which Exelon Corporate owns more than 99% , and BGE, of which Exelon owns 100% of the common stock but none of BGE’s preferred stock. BGE redeemed all of its outstanding preferred stock in 2016. Mergers On March 23, 2016, Exelon completed the merger contemplated by the Merger Agreement among Exelon, Purple Acquisition Corp., a wholly owned subsidiary of Exelon (Merger Sub) and Pepco Holdings, Inc. (PHI). As a result of that merger, Merger Sub was merged into PHI (the PHI Merger) with PHI surviving as a wholly owned subsidiary of Exelon and Exelon Energy Delivery Company, LLC (EEDC), a wholly owned subsidiary of Exelon which also owns Exelon's interests in ComEd, PECO and BGE (through a special purpose subsidiary in the case of BGE). See Note 4 — Mergers, Acquisitions, and Dispositions of the Combined Notes to Consolidated Financial Statements for additional information on the PHI Merger. Debt and Credit Agreements Short-Term Borrowings Exelon Corporate meets its short-term liquidity requirements primarily through the issuance of commercial paper. Exelon Corporate had no commercial paper borrowings at both December 31, 2016 and December 31, 2015 . Credit Agreements On May 30, 2014, Exelon Corporate amended and extended its unsecured syndicated revolving credit facility with aggregate bank commitments of $600 million through May 2019. As of December 31, 2016 , Exelon Corporation had available capacity under those commitments of $571 million . See Note 14 — Debt and Credit Agreements of the Combined Notes to Consolidated Financial Statements for further information regarding Exelon Corporation’s credit agreement. Long-Term Debt The following tables present the outstanding long-term debt for Exelon Corporate as of December 31, 2016 and December 31, 2015 : Maturity Date December 31, Rates 2016 2015 Long-term debt Junior subordinated notes 6.5 % 2024 $ 1,150 $ 1,150 Contract payment - junior subordinated notes 2.5 % 2017 19 64 Senior unsecured notes (a) 1.6 % 7.6 % 2017 - 2046 6,439 4,639 Total long-term debt 7,608 5,853 Unamortized debt discount and premium, net (8 ) (4 ) Unamortized debt issuance costs (57 ) (47 ) Fair value adjustment of consolidated subsidiary 220 275 Long-term debt due within one year (570 ) (60 ) Long-term debt $ 7,193 $ 6,017 ___________ (a) Senior unsecured notes include mirror debt that is held on both Generation and Exelon Corporation's balance sheets. The debt maturities for Exelon Corporate for the periods 2017 , 2018 , 2019 , 2020 , 2021 and thereafter are as follows: 2017 $ 570 2018 — 2019 — 2020 1,450 2021 300 Remaining years 5,288 Total long-term debt $ 7,608 Commitments and Contingencies See Note 24 — Commitments and Contingencies of the Combined Notes to Consolidated Financial Statements for Exelon Corporate’s commitments and contingencies related to environmental matters and fund transfer restrictions. Related Party Transactions The financial statements of Exelon Corporate include related party transactions as presented in the tables below: For the Years Ended December 31, (In millions) 2016 2015 2014 Operating and maintenance from affiliates: BSC (a) $ 51 $ 43 $ 38 Interest income from affiliates, net: Generation $ 39 $ 43 $ 53 Equity in earnings (losses) of investments: Exelon Energy Delivery Company, LLC (b) $ 1,041 $ 1,079 $ 958 PCI 6 — — BSC 1 — — Exelon Ventures Company, LLC (c) — — 926 UII, LLC (9 ) 20 (6 ) Exelon Transmission Company, LLC (13 ) (8 ) (7 ) Exelon Enterprise (1 ) (1 ) (1 ) Generation 496 1,371 (91 ) Total equity in earnings of investments $ 1,521 $ 2,461 $ 1,779 Cash contributions received from affiliates $ 1,912 $ 3,209 $ 1,370 December 31, (in millions) 2016 2015 Accounts receivable from affiliates (current): BSC (a) $ 15 $ — Generation 22 16 ComEd 3 2 PECO 1 1 BGE 1 1 PHISCO 6 — Total accounts receivable from affiliates (current) $ 48 $ 20 Notes receivable from affiliates (current): BSC (a) $ 88 $ 226 Generation (d) — 1,252 Total notes receivable from affiliates (current): $ 88 $ 1,478 Investments in affiliates: BSC (a) $ 194 $ 191 Exelon Energy Delivery Company, LLC (b) 23,003 14,163 PCI 77 — UII, LLC 92 102 Exelon Transmission Company, LLC 5 3 Voluntary Employee Beneficiary Association trust (5 ) 7 Exelon Enterprises 21 22 Generation 11,488 11,637 Other (6 ) (6 ) Total investments in affiliates $ 34,869 $ 26,119 Notes receivable from affiliates (non-current): Generation (d) $ 922 $ 933 Notes payable to affiliates (current): ComEd $ — $ 188 Accounts payable to affiliates (current): ComEd $ 345 $ — UII, LLC 361 — Total accounts payable to affiliates (current) $ 706 $ — _____________________ (a) Exelon Corporate receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. (b) Exelon Energy Delivery Company, LLC consists of ComEd, PECO, BGE, PHI, Pepco, DPL and ACE. (c) Exelon Ventures Company, LLC primarily consisted of Generation and was fully dissolved as of December 31, 2014. Exelon Enterprises, Exelon Generation Company, LLC, and Exelon Consolidations are now directly owned Exelon Corporate investments as of December 31, 2014. (d) In connection with the debt obligations assumed by Exelon as part of the Constellation merger, Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable included in Long-Term Debt to affiliate on Generation’s Consolidated Balance Sheets and intercompany notes receivable at Exelon Corporate, which are eliminated in consolidation on Exelon’s Consolidated Balance Sheets.

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2016
Valuation and Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	Exelon Corporation and Subsidiary Companies Schedule II – Valuation and Qualifying Accounts Column A Column B Column C Column D Column E Additions and adjustments Description Balance at Beginning of Period Charged to Costs and Expenses Charged to Other Accounts Deductions Balance at End of Period (in millions) For the year ended December 31, 2016 Allowance for uncollectible accounts (a) $ 284 $ 162 $ 99 (b) (c) $ 211 (d) $ 334 Deferred tax valuation allowance 13 — 10 (b) 3 20 Reserve for obsolete materials 105 12 1 (b) 5 113 For the year ended December 31, 2015 Allowance for uncollectible accounts (a) $ 311 $ 113 $ 27 (c) $ 167 (d) $ 284 Deferred tax valuation allowance 50 — (27 ) 10 13 Reserve for obsolete materials 95 10 2 2 105 For the year ended December 31, 2014 Allowance for uncollectible accounts (a) $ 272 $ 175 $ 69 (c) $ 205 (d) $ 311 Deferred tax valuation allowance 13 — 37 — 50 Reserve for obsolete materials 58 5 34 2 95 ___________________ (a) Excludes the non-current allowance for uncollectible accounts related to PECO’s installment plan receivables of $23 million , $8 million , and $8 million for the years ended December 31, 2016 , 2015 , and 2014 , respectively. (b) Primarily represents the addition of PHI's results as of March 23, 2016 , the date of the merger (c) Includes charges for late payments and non-service receivables. (d) Write-off of individual accounts receivable. Exelon Generation Company, LLC and Subsidiary Companies Generation 1. Financial Statements: Report of Independent Registered Public Accounting Firm dated February 13, 2017 of PricewaterhouseCoopers LLP Consolidated Statements of Operations and Comprehensive Income for the Years Ended December 31, 2016, 2015 and 2014 Consolidated Statements of Cash Flows for the Years Ended December 31, 2016, 2015 and 2014 Consolidated Balance Sheets at December 31, 2016 and 2015 Consolidated Statements of Changes in Equity for the Years Ended December 31, 2016, 2015 and 2014 Notes to Consolidated Financial Statements 2. Financial Statement Schedules: Schedule II – Valuation and Qualifying Accounts Schedules not included are omitted because of the absence of conditions under which they are required or because the required information is provided in the consolidated financial statements, including the notes thereto Exelon Generation Company, LLC and Subsidiary Companies Schedule II – Valuation and Qualifying Accounts Column A Column B Column C Column D Column E Additions and adjustments Description Balance at Beginning of Period Charged to Costs and Expenses Charged to Other Accounts Deductions Balance at End of Period (in millions) For the year ended December 31, 2016 Allowance for uncollectible accounts $ 77 $ 19 $ 3 $ 8 $ 91 Deferred tax valuation allowance 11 — — 2 9 Reserve for obsolete materials 102 6 — 2 106 For the year ended December 31, 2015 Allowance for uncollectible accounts $ 60 $ 22 $ — $ 5 $ 77 Deferred tax valuation allowance 48 — (27 ) 10 11 Reserve for obsolete materials 93 9 — — 102 For the year ended December 31, 2014 Allowance for uncollectible accounts $ 57 $ 14 $ 8 $ 19 $ 60 Deferred tax valuation allowance 11 — 37 — 48 Reserve for obsolete materials 55 5 32 (1 ) 93 Commonwealth Edison Company and Subsidiary Companies ComEd 1. Financial Statements: Report of Independent Registered Public Accounting Firm dated February 13, 2017 of PricewaterhouseCoopers LLP Consolidated Statements of Operations and Comprehensive Income for the Years Ended December 31, 2016, 2015 and 2014 Consolidated Statements of Cash Flows for the Years Ended December 31, 2016, 2015 and 2014 Consolidated Balance Sheets at December 31, 2016 and 2015 Consolidated Statements of Changes in Shareholders’ Equity for the Years Ended December 31, 2016, 2015 and 2014 Notes to Consolidated Financial Statements 2. Financial Statement Schedules: Schedule II – Valuation and Qualifying Accounts Schedules not included are omitted because of the absence of conditions under which they are required or because the required information is provided in the consolidated financial statements, including the notes thereto Commonwealth Edison Company and Subsidiary Companies Schedule II – Valuation and Qualifying Accounts Column A Column B Column C Column D Column E Additions and adjustments Description Balance at Beginning of Period Charged to Costs and Expenses Charged to Other Accounts Deductions Balance at End of Period (in millions) For the year ended December 31, 2016 Allowance for uncollectible accounts $ 75 $ 45 $ 23 (a) $ 73 (b) $ 70 Reserve for obsolete materials 3 4 1 4 4 For the year ended December 31, 2015 Allowance for uncollectible accounts $ 84 $ 39 $ 18 (a) $ 66 (b) $ 75 Reserve for obsolete materials 2 1 2 2 3 For the year ended December 31, 2014 Allowance for uncollectible accounts $ 62 $ 45 $ 33 (a) $ 56 (b) $ 84 Reserve for obsolete materials 2 — 2 2 2 _____________________ (a) Primarily charges for late payments and non-service receivables. (b) Write-off of individual accounts receivable. PECO Energy Company and Subsidiary Companies PECO 1. Financial Statements: Report of Independent Registered Public Accounting Firm dated February 13, 2017 of PricewaterhouseCoopers LLP Consolidated Statements of Operations and Comprehensive Income for the Years Ended December 31, 2016, 2015 and 2014 Consolidated Statements of Cash Flows for the Years Ended December 31, 2016, 2015 and 2014 Consolidated Balance Sheets at December 31, 2016 and 2015 Consolidated Statements of Changes in Shareholder's Equity for the Years Ended December 31, 2016, 2015 and 2014 Notes to Consolidated Financial Statements 2. Financial Statement Schedules: Schedule II – Valuation and Qualifying Accounts Schedules not included are omitted because of the absence of conditions under which they are required or because the required information is provided in the consolidated financial statements, including the notes thereto PECO Energy Company and Subsidiary Companies Schedule II – Valuation and Qualifying Accounts Column A Column B Column C Column D Column E Additions and adjustments Description Balance at Beginning of Period Charged to Costs and Expenses Charged to Other Accounts Deductions Balance at End of Period (in millions) For the year ended December 31, 2016 Allowance for uncollectible accounts (a) $ 83 $ 32 $ 7 (b) $ 61 (c) $ 61 Reserve for obsolete materials 1 1 — — 2 For the year ended December 31, 2015 Allowance for uncollectible accounts (a) $ 100 $ 37 $ 9 (b) $ 63 (c) $ 83 Reserve for obsolete materials 1 — — — 1 For the year ended December 31, 2014 Allowance for uncollectible accounts (a) $ 107 $ 52 $ 11 (b) $ 70 (c) $ 100 Reserve for obsolete materials 1 — — — 1 _____________________ (a) Excludes the non-current allowance for uncollectible accounts related to PECO’s installment plan receivables of $23 million , $8 million , and $8 million for the years ended December 31, 2016 , 2015 , and 2014 , respectively. (b) Primarily charges for late payments. (c) Write-off of individual accounts receivable. Baltimore Gas and Electric Company and Subsidiary Companies BGE 1. Financial Statements: Report of Independent Registered Public Accounting Firm dated February 13, 2017 of PricewaterhouseCoopers LLP Consolidated Statements of Operations and Comprehensive Income for the Years Ended December 31, 2016, 2015 and 2014 Consolidated Statements of Cash Flows for the Years Ended December 31, 2016, 2015 and 2014 Consolidated Balance Sheets at December 31, 2016 and 2015 Consolidated Statements of Changes in Shareholders’ Equity for the Years Ended December 31, 2016, 2015 and 2014 Notes to Consolidated Financial Statements 2. Financial Statement Schedules: Schedule II – Valuation and Qualifying Accounts Schedules not included are omitted because of the absence of conditions under which they are required or because the required information is provided in the consolidated financial statements, including the notes thereto Baltimore Gas and Electric Company and Subsidiary Companies Schedule II – Valuation and Qualifying Accounts Column A Column B Column C Column D Column E Additions and adjustments Description Balance at Beginning of Period Charged to Costs and Expenses Charged to Other Accounts Deductions Balance at End of Period (in millions) For the year ended December 31, 2016 Allowance for uncollectible accounts $ 49 $ 1 $ 9 (b) $ 27 (a) $ 32 Deferred tax valuation allowance 1 — — — 1 Reserve for obsolete materials — — — — — For the year ended December 31, 2015 Allowance for uncollectible accounts $ 67 $ 15 $ — (b) $ 33 (a) $ 49 Deferred tax valuation allowance 1 — — — 1 Reserve for obsolete materials — — — — — For the year ended December 31, 2014 Allowance for uncollectible accounts $ 46 $ 64 $ 17 (b) $ 60 (a) $ 67 Deferred tax valuation allowance 1 — — — 1 Reserve for obsolete materials 1 — — 1 — _____________________ (a) Write-off of individual accounts receivable. (b) Primarily charges for late payments. Pepco Holdings LLC and Subsidiary Companies PHI 1. Successor Company Financial Statements: Report of Independent Registered Public Accounting Firm dated February 13, 2017 of PricewaterhouseCoopers LLP Consolidated Statement of Operations and Comprehensive Income for the Periods March 24, 2016 to December 31, 2016 Consolidated Statement of Cash Flows for the Periods March 24, 2016 to December 31, 2016 Consolidated Balance Sheet at December 31, 2016 Consolidated Statement of Changes in Equity for the Periods March 24, 2016 to December 31, 2016 Notes to Consolidated Financial Statements Predecessor Company Financial Statements: Report of Independent Registered Public Accounting Firm date February 13, 2017 of PricewaterhouseCoopers LLP Consolidated Statements of Operations and Comprehensive Income for the Period January 1, 2016 to March 23, 2016 and the Years Ended December 31, 2015 and 2014 Consolidated Statements of Cash Flows for the Period January 1, 2016 to March 23, 2016 and for the Years Ended December 31, 2015 and 2014 (Predecessor) Consolidated Balance Sheet at December 31, 2015 Consolidated Statements of Changes in Equity for the Period January 1, 2016 to March 23, 2016 and for the Years Ended December 31, 2015 and 2014 Notes to Consolidated Financial Statements 2. Successor Financial Statement Schedules: Schedule II – Valuation and Qualifying Accounts - For the Period March 24, 2016 to December 31, 2016 Predecessor Financial Statement Schedules: Schedule II – Valuation and Qualifying Accounts - For the Period January 1, 2016 to March 23, 2016 and For the Years Ended December 31, 2015 and 2014 Schedules not included are omitted because of the absence of conditions under which they are required or because the required information is provided in the consolidated financial statements, including the notes thereto Pepco Holdings LLC and Subsidiary Companies Schedule II – Valuation and Qualifying Accounts Column A Column B Column C Column D Column E Additions and adjustments Description Balance at Charged to Charged Deductions Balance at (in millions) March 24, 2016 to December 31, 2016 (Successor) Allowance for uncollectible accounts $ 52 $ 65 $ 5 (a) $ 42 (b) $ 80 Deferred tax valuation allowance 63 — (53 ) — 10 Reserve for obsolete materials — 1 — (1 ) 2 January 1, 2016 to March 23, 2016 (Predecessor) Allowance for uncollectible accounts $ 56 $ 16 $ 2 (a) $ 22 (b) $ 52 Deferred tax valuation allowance 63 — — — 63 Reserve for obsolete materials — — — — — For the Year Ended December 31, 2015 (Predecessor) Allowance for uncollectible accounts $ 40 $ 59 $ 5 (a) $ 48 (b) $ 56 Deferred tax valuation allowance 61 — 2 — 63 Reserve for obsolete materials — — — — — For the Year Ended December 31, 2014 (Predecessor) Allowance for uncollectible accounts $ 38 $ 46 $ 9 (a) $ 53 (b) $ 40 Deferred tax valuation allowance 21 — 40 — 61 Reserve for obsolete materials — — — — — (a) Primarily charges for late payments. (b) Write-off of individual accounts receivable. Potomac Electric Power Company Pepco 1. Financial Statements: Report of Independent Registered Public Accounting Firm dated February 13, 2017 of PricewaterhouseCoopers LLP Statements of Operations and Comprehensive Income for the Years Ended December 31, 2016, 2015 and 2014 Statements of Cash Flows for the Years Ended December 31, 2016, 2015 and 2014 Balance Sheets at December 31, 2016 and 2015 Statements of Changes in Shareholder's Equity for the Years Ended December 31, 2016, 2015 and 2014 Notes to Consolidated Financial Statements 2. Financial Statement Schedules: Schedule II – Valuation and Qualifying Accounts Schedules not included are omitted because of the absence of conditions under which they are required or because the required information is provided in the consolidated financial statements, including the notes thereto Potomac Electric Power Company Schedule II – Valuation and Qualifying Accounts Column A Column B Column C Column D Column E Additions and adjustments Description Balance at Charged to Charged Deductions Balance at (in millions) For the year ended December 31, 2016 Allowance for uncollectible accounts $ 17 $ 29 $ 3 (a) $ 20 (b) $ 29 Deferred tax valuation allowance — — — — — Reserve for obsolete materials — 3 — 2 1 For the year ended December 31, 2015 Allowance for uncollectible accounts $ 16 $ 20 $ 1 (a) $ 20 (b) $ 17 Deferred tax valuation allowance — — — — — Reserve for obsolete materials — — — — — For the year ended December 31, 2014 Allowance for uncollectible accounts $ 16 $ 17 $ 2 (a) $ 19 (b) $ 16 Deferred tax valuation allowance — — — — — Reserve for obsolete materials — — — — — (a) Primarily charges for late payments. (b) Write-off of individual accounts receivable. Power & Light Company DPL 1. Financial Statements: Report of Independent Registered Public Accounting Firm dated February 13, 2017 of PricewaterhouseCoopers LLP Statements of Operations and Comprehensive Income for the Years Ended December 31, 2016, 2015 and 2014 Statements of Cash Flows for the Years Ended December 31, 2016, 2015 and 2014 Balance Sheets at December 31, 2016 and 2015 Statements of Changes in Shareholder's Equity for the Years Ended December 31, 2016, 2015 and 2014 Notes to Consolidated Financial Statements 2. Financial Statement Schedules: Schedule II – Valuation and Qualifying Accounts Schedules not included are omitted because of the absence of conditions under which they are required or because the required information is provided in the consolidated financial statements, including the notes thereto Delmarva Power & Light Company Schedule II – Valuation and Qualifying Accounts Column A Column B Column C Column D Column E Additions and adjustments Description Balance at Charged to Charged Deductions Balance at (in millions) For the year ended December 31, 2016 Allowance for uncollectible accounts $ 17 $ 23 $ 2 (a) $ 18 (b) $ 24 Deferred tax valuation allowance — — — — — Reserve for obsolete materials — 1 — 1 — For the year ended December 31, 2015 Allowance for uncollectible accounts $ 11 $ 20 $ 2 (a) $ 16 (b) $ 17 Deferred tax valuation allowance — — — — — Reserve for obsolete materials — — — — — For the year ended December 31, 2014 Allowance for uncollectible accounts $ 12 $ 13 $ 4 (a) $ 18 (b) $ 11 Deferred tax valuation allowance — — — — — Reserve for obsolete materials — — — — — (a) Primarily charges for late payments. (b) Write-off of individual accounts receivable. Atlantic City Electric Company and Subsidiary Company ACE 1. Financial Statements: Report of Independent Registered Public Accounting Firm dated February 13, 2017 of PricewaterhouseCoopers LLP Consolidated Statements of Operations and Comprehensive Income for the Years Ended December 31, 2016, 2015 and 2014 Consolidated Statements of Cash Flows for the Years Ended December 31, 2016, 2015 and 2014 Consolidated Balance Sheets at December 31, 2016 and 2015 Consolidated Statements of Changes in Shareholder's Equity for the Years Ended December 31, 2016, 2015 and 2014 Notes to Consolidated Financial Statements 2. Financial Statement Schedules: Schedule II – Valuation and Qualifying Accounts Schedules not included are omitted because of the absence of conditions under which they are required or because the required information is provided in the consolidated financial statements, including the notes thereto Atlantic City Electric Company and Subsidiary Company Schedule II – Valuation and Qualifying Accounts Column A Column B Column C Column D Column E Additions and adjustments Description Balance at Charged to Charged Deductions Balance at (in millions) For the year ended December 31, 2016 Allowance for uncollectible accounts $ 17 $ 32 $ 2 (a) $ 24 (b) $ 27 Deferred tax valuation allowance — — — — — Reserve for obsolete materials — 1 — — 1 For the year ended December 31, 2015 Allowance for uncollectible accounts $ 9 $ 18 $ 2 (a) $ 12 (b) $ 17 Deferred tax valuation allowance — — — — — Reserve for obsolete materials — — — — — For the year ended December 31, 2014 Allowance for uncollectible accounts $ 10 $ 12 $ 3 (a) $ 16 (b) $ 9 Deferred tax valuation allowance — — — — — Reserve for obsolete materials — — — — — (a) Primarily charges for late payments. (b) Write-off of individual accounts receivable.

Significant Accounting Polici37

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Description of Business (All Registrants)	Description of Business (All Registrants) Exelon is a utility services holding company engaged through its principal subsidiaries in the energy generation and energy distribution and transmission businesses. Prior to March 23, 2016 , Exelon's principal, wholly owned subsidiaries included Generation, ComEd, PECO and BGE. On March 23, 2016 , in conjunction with the Amended and Restated Agreement and Plan of Merger (the PHI Merger Agreement), Purple Acquisition Corp, a wholly owned subsidiary of Exelon, merged with and into PHI, with PHI continuing as the surviving entity as a wholly owned subsidiary of Exelon. PHI is a utility services holding company engaged through its principal wholly owned subsidiaries, Pepco, DPL and ACE, in the energy distribution and transmission businesses. Refer to Note 4 - Mergers, Acquisitions, and Dispositions for further information regarding the merger transaction. The energy generation business includes: • Generation : Generation, physical delivery and marketing of power across multiple geographical regions through its customer-facing business, Constellation. Generation also sells renewable energy and other energy-related products and services. Generation has six reportable segments consisting of the Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. The energy delivery businesses include: • ComEd : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in northern Illinois, including the City of Chicago. • PECO : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in southeastern Pennsylvania, including the City of Philadelphia, and the purchase and regulated retail sale of natural gas and the provision of natural gas distribution services in the Pennsylvania counties surrounding the City of Philadelphia. • BGE : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in central Maryland, including the City of Baltimore, and the purchase and regulated retail sale of natural gas and the provision of natural gas distribution services in central Maryland, including the City of Baltimore. • Pepco : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in the District of Columbia and major portions of Prince George's County and Montgomery County in Maryland. • DPL : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in portions of Maryland and Delaware, and the purchase and regulated retail sale of natural gas and the provision of natural gas distribution services in northern Delaware. • ACE : Purchase and regulated retail sale of electricity and the provision of electric distribution and transmission services in southern New Jersey. Basis of Presentation (All Registrants) This is a combined annual report of all registrants. The Notes to the Consolidated Financial Statements apply to the registrants as indicated above in the Index to Combined Notes to Consolidated Financial Statements and parenthetically next to each corresponding disclosure. When appropriate, the registrants are named specifically for their related activities and disclosures. Each of the Registrant’s Consolidated Financial Statements includes the accounts of its subsidiaries. All intercompany transactions have been eliminated. All Equity in earnings (losses) from unconsolidated affiliates have been presented below Income taxes in the Registrants' Consolidated Statements of Operations and Comprehensive Income starting in the first quarter of 2015. Pursuant to the acquisition of PHI, Exelon’s financial reporting reflects PHI’s consolidated financial results subsequent to the March 23, 2016 , acquisition date. Exelon has accounted for the merger transaction applying the acquisition method of accounting, which requires the assets acquired and liabilities assumed by Exelon to be reported in Exelon’s financial statements at fair value, with any excess of the purchase price over the fair value of net assets acquired reported as goodwill. Exelon has pushed-down the application of the acquisition method of accounting to the consolidated financial statements of PHI such that the assets and liabilities of PHI are similarly recorded at their respective fair values, and goodwill has been established as of the acquisition date. Accordingly, the consolidated financial statements of PHI for periods before and after the March 23, 2016 , acquisition date reflect different bases of accounting, and the financial positions and the results of operations of the predecessor and successor periods are not comparable. The acquisition method of accounting has not been pushed down to PHI’s wholly-owned subsidiary utility registrants, Pepco, DPL and ACE. For financial statement purposes, beginning on March 24, 2016 , disclosures that had solely related to PHI, Pepco, DPL or ACE activities now also apply to Exelon, unless otherwise noted. Through its business services subsidiary, BSC, Exelon provides its subsidiaries with a variety of support services at cost, including legal, human resources, financial, information technology and supply management services. The costs of BSC, including support services, are directly charged or allocated to the applicable subsidiaries using a cost-causative allocation method. Corporate governance-type costs that cannot be directly assigned are allocated based on a Modified Massachusetts Formula, which is a method that utilizes a combination of gross revenues, total assets and direct labor costs for the allocation base. The results of Exelon’s corporate operations are presented as “Other” within the consolidated financial statements and include intercompany eliminations unless otherwise disclosed. PHISCO, a wholly owned subsidiary of PHI, provides a variety of support services at cost, including legal, accounting, engineering, distribution and transmission planning, asset management, system operations, and power procurement, to PHI and its operating subsidiaries. These services are directly charged or allocated pursuant to service agreements among PHI Service Company and the participating operating subsidiaries. Exelon owns 100% of all of its significant consolidated subsidiaries, including PHI, either directly or indirectly, except for ComEd, of which Exelon owns more than 99% . As of December 31, 2016, Exelon owned none of BGE's preferred securities, which BGE redeemed in 2016. Exelon has reflected the third-party interests in ComEd, which totaled less than $1 million at December 31, 2016 and December 31, 2015 , as equity, and BGE’s preference stock as BGE preference stock not subject to mandatory redemption in its consolidated financial statements. BGE is subject to some ring-fencing measures established by order of the MDPSC. As part of this arrangement, BGE common stock is held directly by RF Holdco LLC, which is an indirect subsidiary of Exelon. GSS Holdings (BGE Utility), an unrelated party, holds a nominal non-economic interest in RF Holdco LLC with limited voting rights on specified matters. PHI is subject to some ring-fencing measures established by orders of the DCPSC, DPSC, MDPSC and NJBPU, pursuant to which all of the membership interest in PHI is held directly by PH Holdco LLC, which is an indirect subsidiary of Exelon. GSS Holdings (PH Utility), Inc., an unrelated party, holds a nominal non-economic interest in PH Holdco LLC with limited voting rights on specified matters. PHI owns 100% of its subsidiaries including Pepco, DPL and ACE. Generation owns 100% of all of its significant consolidated subsidiaries, either directly or indirectly, except for certain variable interest entities, including CENG, of which Generation holds a 50.01% interest. The remaining interests are included in noncontrolling interests on Exelon’s and Generation’s Consolidated Balance Sheets. See Note 2 — Variable Interest Entities for further discussion of Exelon’s and Generation’s consolidated VIEs. The Registrants consolidate the accounts of entities in which a Registrant has a controlling financial interest, after the elimination of intercompany transactions. A controlling financial interest is evidenced by either a voting interest greater than 50% in which the Registrant can exercise control over the operations and policies of the investee, or the results of a model that identifies the Registrant or one of its subsidiaries as the primary beneficiary of a VIE. Where the Registrants do not have a controlling financial interest in an entity, proportionate consolidation, equity method accounting or cost method accounting is applied. The Registrants apply proportionate consolidation when they have an undivided interest in an asset and are proportionately liable for their share of each liability associated with the asset. The Registrants proportionately consolidate their undivided ownership interests in jointly owned electric plants and transmission facilities. Under proportionate consolidation, the Registrants separately record their proportionate share of the assets, liabilities, revenues and expenses related to the undivided interest in the asset. The Registrants apply equity method accounting when they have significant influence over an investee through an ownership in common stock, which generally approximates a 20% to 50% voting interest. The Registrants apply equity method accounting to certain investments and joint ventures, including certain financing trusts of ComEd, PECO and BGE. Under the equity method, the Registrants report their interest in the entity as an investment and the Registrants’ percentage share of the earnings from the entity as single line items in their financial statements. The Registrants use the cost method if they lack significant influence, which generally results when they hold less than 20% of the common stock of an entity. Under the cost method, the Registrants report their investments at cost and recognize income only to the extent dividends or distributions are received. The accompanying consolidated financial statements have been prepared in accordance with GAAP for annual financial statements and in accordance with the instructions to Form 10-K and Regulation S-X promulgated by the SEC.
Use Of Estimates (All Registrants)	Use of Estimates (All Registrants) The preparation of financial statements of each of the Registrants in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Areas in which significant estimates have been made include, but are not limited to, the accounting for nuclear decommissioning costs and other AROs, pension and other postretirement benefits, the application of purchase accounting, inventory reserves, allowance for uncollectible accounts, goodwill and asset impairments, derivative instruments, unamortized energy contracts, fixed asset depreciation, environmental costs and other loss contingencies, taxes and unbilled energy revenues. Actual results could differ from those estimates.
Reclassifications (Exelon, ComEd, and BGE)	Reclassifications (All Registrants) Certain prior year amounts in the Registrants' Consolidated Statements of Operations and Comprehensive Income, Consolidated Balance Sheets and Consolidated Statements of Cash Flows have been reclassified between line items for comparative purposes. The reclassifications did not affect any of the Registrants’ net income, financial positions, or cash flows from operating activities. Certain prior year amounts in the Consolidated Statements of Operations and Comprehensive Income, Consolidated Balance Sheets and Consolidated Statements of Cash Flows of PHI, Pepco, DPL and ACE have been reclassified to conform the presentation of these amounts to the current period presentation in Exelon’s financial statements. Most significantly for PHI, Pepco, DPL and ACE, current regulatory assets and liabilities have been presented separately from the non-current portions in each respective Consolidated Balance Sheet where recovery or refund is expected within the next 12 months. Additionally, for PHI, Pepco, DPL and ACE, the removal cost within Accumulated depreciation was reclassified to the Regulatory liability or Regulatory asset account to align with Exelon’s presentation. The reclassifications were not considered errors in the prior financial statements.
Accounting for the Effects of Regulation (Exelon, ComEd, PECO and BGE)	Accounting for the Effects of Regulation (Exelon, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE) The Registrants apply the authoritative guidance for accounting for certain types of regulation, which requires them to record in their consolidated financial statements the effects of cost-based rate regulation for entities with regulated operations that meet the following criteria: 1) rates are established or approved by a third-party regulator; (2) rates are designed to recover the entities’ cost of providing services or products; and (3) there is a reasonable expectation that rates are set at levels that will recover the entities’ costs from customers. Exelon and the Utility Registrants account for their regulated operations in accordance with regulatory and legislative guidance from the regulatory authorities having jurisdiction, principally the ICC, the PAPUC, the MDPSC, the DCPSC, the DPSC and the NJBPU, under state public utility laws and the FERC under various Federal laws. Regulatory assets and liabilities are amortized and the related expense or revenue is recognized in the Consolidated Statements of Operations consistent with the recovery or refund included in customer rates. Exelon believes that it is probable that its currently recorded regulatory assets and liabilities will be recovered and settled, respectively, in future rates. Exelon and the Utility Registrants continue to evaluate their respective abilities to continue to apply the authoritative guidance for accounting for certain types of regulation, including consideration of current events in their respective regulatory and political environments. If a separable portion of the Registrants' business was no longer able to meet the criteria discussed above, the affected entities would be required to eliminate from their consolidated financial statements the effects of regulation for that portion, which could have a material impact on their results of operations and financial positions. See Note 3 — Regulatory Matters for additional information. ACE has a recovery mechanism for purchased power costs associated with BGS. ACE records a deferred energy supply costs regulatory asset or regulatory liability for under or over-recovered costs that are expected to be recovered from or refunded to ACE customers, respectively. In the first quarter of 2016, ACE changed its method of accounting for determining under or over-recovered costs in this recovery mechanism to include unbilled revenues in the determination of under or over-recovered costs. ACE believes this change is preferable as it better reflects the economic impacts of dollar-for-dollar cost recovery mechanisms. ACE applied the change retrospectively. The impact of the change was a $12 million reduction to ACE’s opening Retained earnings as of January 1, 2014 with a corresponding reduction to Regulatory assets. The impact of the change on Net income attributable to common shareholder was an increase of $2 million and $1 million for the years ended December 31, 2015 and December 31, 2014 , respectively. The Registrants treat the impacts of a final rate order received after the balance sheet date but prior to the issuance of the financial statements as a non-recognized subsequent event, as the receipt of a final rate order is a separate and distinct event that has future impacts on the parties affected by the order.
Revenues (All Registrants)	Revenues (All Registrants) Operating Revenues. Operating revenues are recorded as service is rendered or energy is delivered to customers. At the end of each month, the Registrants accrue an estimate for the unbilled amount of energy delivered or services provided to customers. ComEd records its best estimates of the distribution and transmission revenue impacts resulting from changes in rates that ComEd believes are probable of approval by the ICC and FERC in accordance with its formula rate mechanisms. BGE, Pepco, DPL and ACE record their best estimate of the transmission revenue impacts resulting from changes in rates that they each believe are probable of approval by FERC in accordance with their formula rate mechanisms. See Note 3 — Regulatory Matters and Note 6 — Accounts Receivable for further information. RTOs and ISOs. In RTO and ISO markets that facilitate the dispatch of energy and energy-related products, the Registrants generally report sales and purchases conducted on a net hourly basis in either revenues or purchased power on their Consolidated Statements of Operations and Comprehensive Income, the classification of which depends on the net hourly activity. In addition, capacity revenue and expense classification is based on the net sale or purchase position of the Company in the different RTOs and ISOs. Option Contracts, Swaps and Commodity Derivatives. Certain option contracts and swap arrangements that meet the definition of derivative instruments are recorded at fair value with subsequent changes in fair value recognized as revenue or expense. The classification of revenue or expense is based on the intent of the transaction. For example, gas transactions may be used to hedge the sale of power. This will result in the change in fair value recorded through revenue. To the extent a Utility Registrant receives full cost recovery for energy procurement and related costs from retail customers, it records the fair value of its energy swap contracts with unaffiliated suppliers as well as an offsetting regulatory asset or liability on its Consolidated Balance Sheets. Refer to Note 3 — Regulatory Matters and Note 13 — Derivative Financial Instruments for further information. Proprietary Trading Activities. Exelon and Generation account for Generation’s trading activities under the provisions of the authoritative guidance for accounting for contracts involved in energy trading and risk management activities, which require energy revenues and costs related to energy trading contracts to be presented on a net basis in the Consolidated Statements of Operations and Comprehensive Income. Commodity derivatives used for trading purposes are accounted for using the mark-to-market method with unrealized gains and losses recognized in operating revenues. Refer to Note 13 — Derivative Financial Instruments for further information.
Income Taxes (All Registrants)	Income Taxes (All Registrants) Deferred Federal and state income taxes are provided on all significant temporary differences between the book basis and the tax basis of assets and liabilities and for tax benefits carried forward. Investment tax credits have been deferred on the Registrants’ Consolidated Balance Sheets and are recognized in book income over the life of the related property. In accordance with applicable authoritative guidance, the Registrants account for uncertain income tax positions using a benefit recognition model with a two-step approach; a more-likely-than-not recognition criterion; and a measurement approach that measures the position as the largest amount of tax benefit that is greater than 50% likely of being realized upon ultimate settlement. If it is not more-likely-than-not that the benefit of the tax position will be sustained on its technical merits, no benefit is recorded. Uncertain tax positions that relate only to timing of when an item is included on a tax return are considered to have met the recognition threshold. The Registrants recognize accrued interest related to unrecognized tax benefits in Interest expense or Other income and deductions (interest income) and recognize penalties related to unrecognized tax benefits in Other, net on their Consolidated Statements of Operations and Comprehensive Income. In the first quarter of 2016, PHI, Pepco, DPL and ACE changed their accounting for classification of interest on uncertain tax positions. PHI, Pepco, DPL and ACE have reclassified interest on uncertain tax positions as Interest expense from Income tax expense in the Consolidated Statements of Operations and Comprehensive Income. GAAP does not address the preferability of one acceptable method of accounting over the other for the classification of interest on uncertain tax positions. However, PHI, Pepco, DPL and ACE believe this change is preferable for comparability of their financial statements with the financial statements of the other Registrants in the combined filing, for consistency with FERC classification and for a more appropriate representation of the effective tax rate as they manage the settlement of uncertain tax positions and interest expense separately. PHI, Pepco, DPL and ACE applied the change retrospectively. The reclassification in the Consolidated Statements of Operations and Comprehensive Income for the year ended December 31, 2015 is $34 million and $4 million for PHI and Pepco, respectively, and for the year ended December 31, 2014 is $1 million for both Pepco and ACE. The impact on all other PHI Registrants for years ended December 31, 2015 and December 31, 2014 is less than $1 million . Pursuant to the IRC and relevant state taxing authorities, Exelon and its subsidiaries file consolidated or combined income tax returns for Federal and certain state jurisdictions where allowed or required. See Note 15 — Income Taxes for further information. Taxes Directly Imposed on Revenue-Producing Transactions (All Registrants) The Registrants collect certain taxes from customers such as sales and gross receipts taxes, along with other taxes, surcharges and fees that are levied by state or local governments on the sale or distribution of gas and electricity. Some of these taxes are imposed on the customer, but paid by the Registrants, while others are imposed on the Registrants. Where these taxes are imposed on the customer, such as sales taxes, they are reported on a net basis with no impact to the Consolidated Statements of Operations and Comprehensive Income. However, where these taxes are imposed on the Registrants, such as gross receipts taxes or other surcharges or fees, they are reported on a gross basis. Accordingly, revenues are recognized for the taxes collected from customers along with an offsetting expense. See Note 25 — Supplemental Financial Information for Generation’s, ComEd’s, PECO’s, BGE’s, Pepco's, DPL's and ACE's utility taxes that are presented on a gross basis.
Cash and Cash Equivalents (All Registrants)	Cash and Cash Equivalents (All Registrants) The Registrants consider investments purchased with an original maturity of three months or less to be cash equivalents. Restricted Cash and Cash Equivalents (All Registrants) Restricted cash and cash equivalents represent funds that are restricted to satisfy designated current liabilities. As of December 31, 2016 and 2015 , Exelon Corporate’s restricted cash and cash equivalents primarily represented restricted funds for payment of medical, dental, vision and long-term disability benefits. Generation’s restricted cash and cash equivalents primarily included cash at various project-specific non-recourse financing structures for debt service and financing of operations of the underlying entities, see Note 14 - Debt and Credit Agreements for additional information on Generation’s project- specific financing structures. ComEd’s restricted cash primarily represented cash collateral held from suppliers associated with ComEd’s energy and REC procurement contracts. PECO’s restricted cash primarily represented funds from the sales of assets that were subject to PECO’s mortgage indenture. BGE’s restricted cash primarily represented funds restricted at its consolidated variable interest entity for repayment of rate stabilization bonds and cash collateral held from suppliers. PHI Corporate's restricted cash and cash equivalents primarily represented funds restricted for the payment of merger commitments and cash collateral held from its utility suppliers. Pepco's restricted cash and cash equivalents primarily represented funds restricted for the payment of merger commitments and collateral held from its utility suppliers. DPL's restricted cash and cash equivalents primarily represented cash collateral held from suppliers associated with procurement contracts. ACE's restricted cash and cash equivalents primarily represented funds restricted at its consolidated variable interest entity for repayment of transition bonds and cash collateral held from suppliers. Restricted cash and cash equivalents not available to satisfy current liabilities are classified as noncurrent assets. As of December 31, 2016 and 2015 , Exelon’s and Generation’s NDT funds, which are designated to satisfy future decommissioning obligations, were classified as noncurrent assets. As of December 31, 2016 , Exelon, Generation, ComEd, PECO, BGE, PHI and Pepco had investments in Rabbi trusts classified as noncurrent assets.
Allowance for Uncollectible Accounts (All Registrants)	Allowance for Uncollectible Accounts (All Registrants) The allowance for uncollectible accounts reflects the Registrants’ best estimates of losses on the accounts receivable balances. For Generation, the allowance is based on accounts receivable aging historical experience and other currently available information. ComEd, PECO and BGE estimate the allowance for uncollectible accounts on customer receivables by applying loss rates developed specifically for each company to the outstanding receivable balance by customer risk segment. At December 31, 2015, Pepco, DPL and ACE estimated the allowance for uncollectible accounts based on specific identification of material amounts at risk by customer and maintained a reserve based on their historical collection experience. At December 31, 2016, Pepco, DPL and ACE aligned the estimation of their allowance for uncollectible accounts to be consistent with ComEd, PECO and BGE, as described above. Risk segments represent a group of customers with similar credit quality indicators that are comprised based on various attributes, including delinquency of their balances and payment history. Loss rates applied to the accounts receivable balances are based on historical average charge-offs as a percentage of accounts receivable in each risk segment. Utility Registrants customers’ accounts are generally considered delinquent if the amount billed is not received by the time the next bill is issued, which normally occurs on a monthly basis. Utility Registrants' customer accounts are written off consistent with approved regulatory requirements. Utility Registrants' allowances for uncollectible accounts will continue to be affected by changes in volume, prices and economic conditions as well as changes in ICC, PAPUC, MDPSC, DCPSC, DPSC and NJBPU regulations. See Note 3 — Regulatory Matters for additional information regarding the regulatory recovery of uncollectible accounts receivable at ComEd.
Variable Interest Entities (All Registrants)	Variable Interest Entities (All Registrants) Exelon accounts for its investments in and arrangements with VIEs based on the authoritative guidance which includes the following specific requirements: • requires an entity to qualitatively assess whether it should consolidate a VIE based on whether the entity has a controlling financial interest, meaning (1) has the power to direct matters that most significantly impact the activities of the VIE, and (2) has the obligation to absorb losses or the right to receive benefits of the VIE that could potentially be significant to the VIE, • requires an ongoing reconsideration of this assessment instead of only upon certain triggering events, and • requires the entity that consolidates a VIE (the primary beneficiary) to disclose (1) the assets of the consolidated VIE, if they can be used to only settle specific obligations of the consolidated VIE, and (2) the liabilities of a consolidated VIE for which creditors do not have recourse to the general credit of the primary beneficiary. See Note 2 — Variable Interest Entities for additional information.
Inventories (All Registrants)	Inventories (All Registrants) Inventory is recorded at the lower of weighted average cost or net realizable value. Provisions are recorded for excess and obsolete inventory. Fossil Fuel. Fossil fuel inventory includes natural gas held in storage, propane and oil. The costs of natural gas, propane and oil are generally included in inventory when purchased and charged to purchased power and fuel expense at weighted average cost when used or sold. Materials and Supplies. Materials and supplies inventory generally includes transmission, distribution and generating plant materials. Materials are generally charged to inventory when purchased and expensed or capitalized to property, plant and equipment, as appropriate, at weighted average cost when installed or used. Emission Allowances. Emission allowances are included in inventory (for emission allowances exercisable in the current year) and other deferred debits (for emission allowances that are exercisable beyond one year) and charged to purchased power and fuel expense at weighted average cost as they are used in operations.
Marketable Securities (All Registrants)	Marketable Securities (All Registrants) All marketable securities are reported at fair value. Marketable securities held in the NDT funds are classified as trading securities, and all other securities are classified as available-for-sale securities. Realized and unrealized gains and losses, net of tax, on Generation’s NDT funds associated with the Regulatory Agreement Units are included in regulatory liabilities at Exelon, ComEd and PECO and in Noncurrent payables to affiliates at Generation and in Noncurrent receivables from affiliates at ComEd and PECO. Realized and unrealized gains and losses, net of tax, on Generation’s NDT funds associated with the Non-Regulatory Agreement Units are included in earnings at Exelon and Generation. Unrealized gains and losses, net of tax, for Exelon's available-for-sale securities are reported in OCI. Any decline in the fair value of Exelon's available-for-sale securities below the cost basis is reviewed to determine if such decline is other-than-temporary. If the decline is determined to be other-than-temporary, the cost basis of the available-for-sale securities is written down to fair value as a new cost basis and the amount of the write-down is included in earnings. See Note 3 — Regulatory Matters for additional information regarding ComEd’s and PECO’s regulatory assets and liabilities and Note 12 — Fair Value of Financial Assets and Liabilities and Note 16 — Asset Retirement Obligations for information regarding marketable securities held by NDT funds.
Property Plant And Equipment (All Registrants)	Property, Plant and Equipment (All Registrants) Property, plant and equipment is recorded at original cost. Original cost includes construction-related direct labor and material costs. The Utility Registrants also include indirect construction costs including labor and related costs of departments associated with supporting construction activities. When appropriate, original cost also includes capitalized interest for Generation and Exelon Corporate and AFUDC for regulated property at ComEd, PECO, BGE, Pepco, DPL and ACE. The cost of repairs and maintenance, including planned major maintenance activities and minor replacements of property, is charged to maintenance expense as incurred. Third parties reimburse the Utility Registrants for all or a portion of expenditures for certain capital projects. Such contributions in aid of construction costs (CIAC) are recorded as a reduction to Property, plant and equipment. DOE SGIG funds reimbursed to PECO, BGE, Pepco and ACE have been accounted for as CIAC. For Generation, upon retirement, the cost of property is generally charged to accumulated depreciation in accordance with the composite method of depreciation. Upon replacement of an asset, the costs to remove the asset, net of salvage, are capitalized to gross plant when incurred as part of the cost of the newly-installed asset and recorded to depreciation expense over the life of the new asset. Removal costs, net of salvage, incurred for property that will not be replaced is charged to Operating and maintenance expense as incurred. For the Utility Registrants, upon retirement, the cost of property, net of salvage, is charged to accumulated depreciation in accordance with the composite method of depreciation. The Utility Registrants' depreciation expense includes the estimated cost of dismantling and removing plant from service upon retirement, which is consistent with each utility’s regulatory recovery method. The Utility Registrants' actual incurred removal costs are applied against a related regulatory liability. PECO’s removal costs are capitalized to accumulated depreciation when incurred, and recorded to depreciation expense over the life of the new asset constructed consistent with PECO’s regulatory recovery method. See Note 7 — Property, Plant and Equipment , Note 10 — Jointly Owned Electric Utility Plant and Note 25 — Supplemental Financial Information for additional information regarding property, plant and equipment.
Nuclear Fuel (Exelon and Generation)	Nuclear Fuel (Exelon and Generation) The cost of nuclear fuel is capitalized within Property, plant and equipment and charged to fuel expense using the unit-of-production method. Prior to May 16, 2014, the estimated disposal cost of SNF was established per the Standard Waste Contract with the DOE and was expensed through fuel expense at one mill ($0.001) per kWh of net nuclear generation. Effective May 16, 2014, the SNF disposal fee was set to zero by the DOE and Exelon and Generation are not accruing any further costs related to SNF disposal fees until a new fee structure goes into effect. Certain on-site SNF storage costs are being reimbursed by the DOE since a DOE (or government-owned) long-term storage facility has not been completed. See Note 24 — Commitments and Contingencies for additional information regarding the SNF disposal fee.
Nuclear Outage Costs (Exelon and Generation)	Nuclear Outage Costs (Exelon and Generation) Costs associated with nuclear outages, including planned major maintenance activities, are expensed to operating and maintenance expense or capitalized to property, plant and equipment (based on the nature of the activities) in the period incurred.
New Site Development Costs (Exelon and Generation)	New Site Development Costs (Exelon and Generation) New site development costs represent the costs incurred in the assessment and design of new power generating facilities. Such costs are capitalized when management considers project completion to be probable, primarily based on management’s determination that the project is economically and operationally feasible, management and/or the Exelon board of directors has approved the project and has committed to a plan to develop it, and Exelon and Generation have received the required regulatory approvals or management believes the receipt of required regulatory approvals is probable. As of December 31, 2016 and 2015 , Generation has capitalized $1.7 billion and $1.3 billion , respectively, to Property, plant and equipment,net on its Consolidated Balance Sheets. Capitalized development costs are charged to Operating and maintenance expense when project completion is no longer probable. New site development costs incurred prior to a project’s completion being deemed probable are expensed as incurred. Approximately $30 million , $22 million and $13 million of costs were expensed by Exelon and Generation for the years ended December 31, 2016 , 2015 , and 2014 , respectively.
Capitalized Software Costs (Exelon, Generation, ComEd, PECO and BGE)	Capitalized Software Costs (All Registrants) Costs incurred during the application development stage of software projects that are internally developed or purchased for operational use are capitalized within property, plant, and equipment. Such capitalized amounts are amortized ratably over the expected lives of the projects when they become operational, generally not to exceed five years. Certain other capitalized software costs are being amortized over longer lives based on the expected life or pursuant to prescribed regulatory requirements
Depreciation, Depletion, and Amortization (All Registrants)	Depreciation, Depletion and Amortization (All Registrants) Except for the amortization of nuclear fuel, depreciation is generally recorded over the estimated service lives of property, plant and equipment on a straight-line basis using the composite method in which depreciation is calculated using the average estimated service life of assets within a group. The Utility Registrants' depreciation expense includes the estimated cost of dismantling and removing plant from service upon retirement, which is consistent with each utility's regulatory recovery method. The estimated service lives for the Utility Registrants are primarily based on each company's most recent depreciation studies of historical asset retirement and removal cost experience. At Generation, along with depreciation study results, management considers expected future energy market conditions and generation plant operating costs and capital investment requirements in determining the estimated service lives of its generating facilities. For its nuclear generating facilities, except for Oyster Creek and Clinton, Generation estimates each unit will operate through the full term of its initial 20-year operating license renewal period. See Note 9 - Early Nuclear Plant Retirements for additional information on the impacts of expected and potential early plant retirements . The estimated service lives of Generation's hydroelectric generating facilities are based on the remaining useful lives of the stations, which assume a license renewal extension of 40 years. See Note 7 — Property, Plant and Equipment for further information regarding depreciation. Amortization of regulatory assets and liabilities are recorded over the recovery or refund period specified in the related legislation or regulatory order or agreement. When the recovery or refund period is less than one year, amortization is recorded to the line item in which the deferred cost or income would have originally been recorded in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Amortization of ComEd’s distribution formula rate regulatory asset and ComEd’s, BGE’s, Pepco's, DPL's and ACE's transmission formula rate regulatory assets is recorded to Operating revenues. Amortization of income tax related regulatory assets and liabilities are generally recorded to Income tax expense. With the exception of the regulatory assets and liabilities discussed above, when the recovery period is more than one year, the amortization is generally recorded to Depreciation and amortization in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 3 — Regulatory Matters and Note 25 — Supplemental Financial Information for additional information regarding Generation’s nuclear fuel, Generation’s ARC and the amortization of the Utility Registrants' regulatory assets.
Asset Retirement Obligations (All Registrants)	Asset Retirement Obligations (All Registrants) The authoritative guidance for accounting for AROs requires the recognition of a liability for a legal obligation to perform an asset retirement activity even though the timing and/or method of settlement may be conditional on a future event. To estimate its decommissioning obligation related to its nuclear generating stations, Generation uses a probability-weighted, discounted cash flow model which, on a unit-by-unit basis, considers multiple outcome scenarios that include significant estimates and assumptions, and are based on decommissioning cost studies, cost escalation rates, probabilistic future cash flow models and discount rates. Generation generally updates its ARO annually, unless circumstances warrant more frequent updates, based on its review of updated cost studies and its annual evaluation of cost escalation factors and probabilities assigned to various decommissioning scenarios. Decommissioning cost studies are updated, on a rotational basis, for each of Generation’s nuclear units at least every five years unless circumstances warrant more frequent updates (such as a change in assumed operating life for a nuclear plant). As part of the annual cost study update process, Generation evaluates newly assumed costs or substantive changes in previously assumed costs to determine if the cost estimate impacts are sufficiently material to warrant application of the updated estimates to the AROs across the nuclear fleet outside of the normal five-year rotating cost study update cycle. The liabilities associated with Exelon’s non-nuclear AROs are adjusted on an ongoing rotational basis, at least once every five years unless circumstances warrant more frequent updates. Changes to the recorded value of an ARO result from the passage of new laws and regulations, revisions to either the timing or amount of estimated undiscounted cash flows, and estimates of cost escalation factors. AROs are accreted throughout each year to reflect the time value of money for these present value obligations through a charge to Operating and maintenance expense in the Consolidated Statements of Operations and Comprehensive Income or, in the case of the Utility Registrants' accretion, through an increase to regulatory assets. See Note 16 — Asset Retirement Obligations for additional information.
Capitalized Interest (All Registrants)	Capitalized Interest and AFUDC (All Registrants) During construction, Exelon and Generation capitalize the costs of debt funds used to finance non-regulated construction projects. Capitalization of debt funds is recorded as a charge to construction work in progress and as a non-cash credit to interest expense.
Allowance For Funds Used During Construction (Exelon, Generation, ComEd, PECO and BGE)	Exelon, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE apply the authoritative guidance for accounting for certain types of regulation to calculate AFUDC, which is the cost, during the period of construction, of debt and equity funds used to finance construction projects for regulated operations. AFUDC is recorded to construction work in progress and as a non-cash credit to AFUDC that is included in interest expense for debt-related funds and other income and deductions for equity-related funds. The rates used for capitalizing AFUDC are computed under a method prescribed by regulatory authorities.
Guarantees (All Registrants)	Guarantees (All Registrants) The Registrants recognize, at the inception of a guarantee, a liability for the fair market value of the obligations they have undertaken by issuing the guarantee, including the ongoing obligation to perform over the term of the guarantee in the event that the specified triggering events or conditions occur. The liability that is initially recognized at the inception of the guarantee is reduced as the Registrants are released from risk under the guarantee. Depending on the nature of the guarantee, the release from risk of the Registrant may be recognized only upon the expiration or settlement of the guarantee or by a systematic and rational amortization method over the term of the guarantee. See Note 24 — Commitments and Contingencies for additional information.
Long-lived Assets (All Registrants)	Long-Lived Assets. The Registrants evaluate the carrying value of their long-lived assets or asset groups, excluding goodwill, when circumstances indicate the carrying value of those assets may not be recoverable. Indicators of impairment may include a deteriorating business climate, including, but not limited to, declines in energy prices, condition of the asset, specific regulatory disallowance, or plans to dispose of a long-lived asset significantly before the end of its useful life. The Registrants determine if long-lived assets and asset groups are impaired by comparing the undiscounted expected future cash flows to the carrying value. When the undiscounted cash flow analysis indicates a long-lived asset or asset group is not recoverable, the amount of the impairment loss is determined by measuring the excess of the carrying amount of the long-lived asset or asset group over its fair value less costs to sell. Cash flows for long-lived assets and asset groups are determined at the lowest level for which identifiable cash flows are largely independent of the cash flows of other assets and liabilities. The cash flows from the generating units are generally evaluated at a regional portfolio level along with cash flows generated from the customer supply and risk management activities, including cash flows from related intangible assets and liabilities on the balance sheet. In certain cases, generating assets may be evaluated on an individual basis where those assets are contracted on a long-term basis with a third party and operations are independent of other generation assets (typically contracted renewables). See Note 8 — Impairment of Long-Lived Assets for additional information.
Goodwill (All Registrants)	Goodwill. Goodwill represents the excess of the purchase price paid over the estimated fair value of the assets acquired and liabilities assumed in the acquisition of a business. Goodwill is not amortized, but is tested for impairment at least annually or on an interim basis if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying value. See Note 11 — Intangible Assets for additional information regarding Exelon’s, Generation's, ComEd’s and PHI's goodwill.
Equity Method Investments (All Registrants)	Equity Method Investments. Exelon and Generation regularly monitor and evaluate equity method investments to determine whether they are impaired. An impairment is recorded when the investment has experienced a decline in value that is other-than-temporary in nature. Additionally, if the project in which Generation holds an investment recognizes an impairment loss, Exelon and Generation would record their proportionate share of that impairment loss and evaluate the investment for an other-than-temporary decline in value. Debt and Equity Security Investments. Exelon and Generation regularly monitor and evaluate debt and equity investments to determine whether they are impaired. An impairment is recorded when the investment has experienced a decline in value that is other-than-temporary in nature. Equity Investment Earnings (Losses) of Unconsolidated Affiliates (Exelon and Generation) Exelon and Generation include equity in earnings from equity method investments in qualifying facilities, power projects and joint ventures, in equity in earnings (losses) of unconsolidated affiliates within their Consolidated Statements of Operations and Comprehensive Income. Equity in earnings (losses) of unconsolidated affiliates also includes any adjustments to amortize the difference, if any, except for goodwill and land, between the cost in an equity method investment and the underlying equity in net assets of the investee at the date of investment.
Direct Financing Lease Investments (Exelon, Generation, ComEd, PECO and BGE)
Derivatives Financial Instruments (All Registrants)	Derivative Financial Instruments (All Registrants) All derivatives are recognized on the balance sheet at their fair value unless they qualify for certain exceptions, including the normal purchases and normal sales exception. Additionally, derivatives that qualify and are designated for hedge accounting are classified as either hedges of the fair value of a recognized asset or liability or of an unrecognized firm commitment (fair value hedge) or hedges of a forecasted transaction or the variability of cash flows to be received or paid related to a recognized asset or liability (cash flow hedge). For fair value hedges, changes in fair values for both the derivative and the underlying hedged exposure are recognized in earnings each period. For cash flow hedges, the portion of the derivative gain or loss that is effective in offsetting the change in the cost or value of the underlying exposure is deferred in AOCI and later reclassified into earnings when the underlying transaction occurs. Gains and losses from the ineffective portion of any hedge are recognized in earnings immediately. For derivative contracts intended to serve as economic hedges and that are not designated or do not qualify for hedge accounting or the normal purchases and normal sales exception, changes in the fair value of the derivatives are recognized in earnings each period, except for the Utility Registrants where changes in fair value may be recorded as a regulatory asset or liability if there is an ability to recover or return the associated costs. See Note 3 — Regulatory Matters and Note 13 — Derivative Financial Instruments for additional information. Amounts classified in earnings are included in revenue, purchased power and fuel, interest expense or other, net on the Consolidated Statements of Operations and Comprehensive Income based on the activity the transaction is economically hedging. For energy-related derivatives entered into for proprietary trading purposes, which are subject to Exelon’s Risk Management Policy, changes in the fair value of the derivatives are recognized in earnings each period. All amounts classified in earnings related to proprietary trading are included in revenue on the Consolidated Statements of Operations and Comprehensive Income. Cash inflows and outflows related to derivative instruments are included as a component of operating, investing or financing cash flows in the Consolidated Statements of Cash Flows, depending on the nature of each transaction. For commodity derivative contracts Generation no longer utilizes the election provided for by the cash flow hedge designation and de-designated all of its existing cash flow hedges prior to the March 2012 merger of Exelon and Constellation. Because the underlying forecasted transactions at that time remained probable, the fair value of the effective portion of these cash flow hedges was frozen in AOCI and was reclassified to results of operations when the forecasted purchase or sale of the energy commodity occurred through March 31, 2015. Accordingly, all derivatives executed to hedge economic risk related to commodities are recorded at fair value with changes in fair value recognized through earnings for the combined company. As part of Generation’s energy marketing business, Generation enters into contracts to buy and sell energy to meet the requirements of its customers. These contracts include short-term and long-term commitments to purchase and sell energy and energy-related products in the energy markets with the intent and ability to deliver or take delivery of the underlying physical commodity. Normal purchases and normal sales are contracts where physical delivery is probable, quantities are expected to be used or sold in the normal course of business over a reasonable period of time and will not be financially settled. Revenues and expenses on derivative contracts that qualify, and are designated, as normal purchases and normal sales are recognized when the underlying physical transaction is completed. While these contracts are considered derivative financial instruments, they are not required to be recorded at fair value, but rather are recorded on an accrual basis of accounting. See Note 13 — Derivative Financial Instruments for additional information.
Retirement Benefits (All Registrants)	Retirement Benefits (All Registrants) Exelon sponsors defined benefit pension plans and other postretirement benefit plans for essentially all employees. The measurement of the plan obligations and costs of providing benefits under these plans involve various factors, including numerous assumptions and inputs and accounting elections. The assumptions are reviewed annually and at any interim remeasurement of the plan obligations. The impact of assumption changes or experience different from that assumed on pension and other postretirement benefit obligations is recognized over time rather than immediately recognized in the Consolidated Statements of Operations and Comprehensive Income. Gains or losses in excess of the greater of ten percent of the projected benefit obligation or the MRV of plan assets are amortized over the expected average remaining service period of plan participants. See Note 17 — Retirement Benefits for additional information.
Investment, Policy [Policy Text Block]	Debt and Equity Security Investments. Exelon and Generation regularly monitor and evaluate debt and equity investments to determine whether they are impaired. An impairment is recorded when the investment has experienced a decline in value that is other-than-temporary in nature. Equity Investment Earnings (Losses) of Unconsolidated Affiliates (Exelon and Generation) Exelon and Generation include equity in earnings from equity method investments in qualifying facilities, power projects and joint ventures, in equity in earnings (losses) of unconsolidated affiliates within their Consolidated Statements of Operations and Comprehensive Income. Equity in earnings (losses) of unconsolidated affiliates also includes any adjustments to amortize the difference, if any, except for goodwill and land, between the cost in an equity method investment and the underlying equity in net assets of the investee at the date of investment.

Significant Accounting Polici38

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Schedule Of Capitalized Software	The following table presents net unamortized capitalized software costs and amortization of capitalized software costs by year: Net unamortized software costs Exelon Generation ComEd PECO BGE Pepco DPL ACE December 31, 2016 $ 808 $ 173 $ 213 $ 91 $ 164 $ 1 $ 1 $ 1 December 31, 2015 633 180 172 86 178 — 1 1 Amortization of capitalized software costs Exelon Generation ComEd PECO BGE Pepco DPL ACE 2016 $ 255 $ 72 $ 62 $ 33 $ 44 $ — $ — $ — 2015 208 73 47 33 46 (2 ) — — 2014 186 59 45 28 43 2 — — Successor Predecessor PHI December 31, 2016 December 31, 2015 Net unamortized software costs $ 153 $ 172 Successor Predecessor PHI March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 Amortization of capitalized software costs $ 29 $ 8 $ 36 $ 30
Schedule Of Capitalized Interest And AFUDC	The following table summarizes total incurred interest, capitalized interest and credits to AFUDC by year: Exelon (a) Generation (a) ComEd PECO BGE Pepco DPL ACE 2016 Total incurred interest (b) $ 1,678 $ 472 $ 469 $ 127 $ 114 $ 137 $ 52 $ 65 Capitalized interest 108 107 — — — — — — Credits to AFUDC debt and equity 98 — 22 11 30 29 7 9 2015 Total incurred interest (b) $ 1,170 $ 445 $ 336 $ 116 $ 113 $ 131 $ 51 $ 65 Capitalized interest 79 79 — — — — — — Credits to AFUDC debt and equity 44 — 9 7 28 19 2 2 2014 Total incurred interest (b) $ 1,144 $ 419 $ 323 $ 115 $ 118 $ 121 $ 49 $ 65 Capitalized interest 63 63 — — — — — — Credits to AFUDC debt and equity 37 — 5 8 24 16 3 2 Successor Predecessor PHI March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 Total incurred interest (b) $ 207 $ 68 $ 289 $ 277 Credits to AFUDC debt and equity 35 10 23 21

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2016
Variable Interest Entity [Abstract]
Schedule of Variable Interest Entities	The carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in the Registrants' consolidated financial statements at December 31, 2016 and December 31, 2015 are as follows: December 31, 2016 December 31, 2015 Successor Predecessor Exelon (a)(b) Generation BGE PHI (b) ACE Exelon (a) Generation BGE PHI ACE Current assets $ 954 $ 916 $ 23 $ 14 9 $ 909 $ 881 $ 23 $ 12 $ 12 Noncurrent assets 8,563 8,525 3 35 23 8,009 8,004 3 18 18 Total assets $ 9,517 $ 9,441 $ 26 $ 49 $ 32 $ 8,918 $ 8,885 $ 26 $ 30 $ 30 Current liabilities $ 885 $ 802 $ 42 $ 42 37 $ 473 $ 387 $ 81 $ 48 $ 48 Noncurrent liabilities 2,713 2,612 — 101 89 2,927 2,884 41 124 124 Total liabilities $ 3,598 $ 3,414 $ 42 $ 143 $ 126 $ 3,400 $ 3,271 $ 122 $ 172 $ 172 _______________________ (a) Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity. (b) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. December 31, 2016 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 638 $ 567 $ 1,205 Total liabilities (a) 215 287 502 Exelon's ownership interest in VIE (a) — 248 248 Other ownership interests in VIE (a) 423 32 455 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 264 264 Contract intangible asset 9 — 9 Debt and payment guarantees — 3 3 Net assets pledged for Zion Station decommissioning (b) 9 — 9 December 31, 2015 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 263 $ 164 $ 427 Total liabilities (a) 22 125 147 Exelon's ownership interest in VIE (a) — 11 11 Other ownership interests in VIE (a) 241 28 269 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 21 21 Contract intangible asset 9 — 9 Debt and payment guarantees — 3 3 Net assets pledged for Zion Station decommissioning (b) 17 — 17 ___________________ (a) These items represent amounts on the unconsolidated VIE balance sheets, not on Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs. (b) These items represent amounts on Exelon’s and Generation’s Consolidated Balance Sheets related to the asset sale agreement with ZionSolutions, LLC. The net assets pledged for Zion Station decommissioning includes gross pledged assets of $113 million and $206 million as of December 31, 2016 and December 31, 2015 , respectively; offset by payables to ZionSolutions LLC of $104 million and $189 million as of December 31, 2016 and December 31, 2015 , respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE. As of December 31, 2016 and December 31, 2015 , these assets and liabilities primarily consisted of the following: December 31, 2016 December 31, 2015 Successor Predecessor Exelon (a)(b) Generation BGE PHI (b) ACE Exelon (a) Generation BGE PHI ACE Cash and cash equivalents $ 150 $ 150 $ — $ — $ — $ 164 $ 164 $ — $ — $ — Restricted cash 59 27 23 9 9 100 77 23 12 12 Accounts receivable, net Customer 371 371 — — — 219 219 — — — Other 48 48 — — — 43 43 — — — Mark-to-market derivatives assets 31 31 — — — 140 140 — — — Inventory Materials and supplies 199 199 — — — 181 181 — — — Other current assets 50 44 — 5 — 35 30 — — — Total current assets 908 870 23 14 9 882 854 23 12 12 Property, plant and equipment, net 5,415 5,415 — — — 5,160 5,160 — — — Nuclear decommissioning trust funds 2,185 2,185 — — — 2,036 2,036 — — — Goodwill 47 47 — — — 47 47 — — — Mark-to-market derivatives assets 23 23 — — — 53 53 — — — Other noncurrent assets 315 277 3 35 23 90 85 3 18 18 Total noncurrent assets 7,985 7,947 3 35 23 7,386 7,381 3 18 18 Total assets $ 8,893 $ 8,817 $ 26 $ 49 $ 32 $ 8,268 $ 8,235 $ 26 $ 30 $ 30 Long-term debt due within one year $ 181 $ 99 $ 41 $ 40 $ 35 $ 111 $ 27 $ 79 $ 46 $ 46 Accounts payable 269 269 — — — 216 216 — — — Accrued expenses 119 116 1 2 2 115 113 2 2 2 Mark-to-market derivative liabilities 60 60 — — — 5 5 — — — Unamortized energy contract liabilities 15 15 — — — 12 12 — — — Other current liabilities 30 30 — — — 13 13 — — — Total current liabilities 674 589 42 42 37 472 386 81 48 48 Long-term debt 641 540 — 101 89 666 623 41 124 124 Asset retirement obligations 1,904 1,904 — — — 1,999 1,999 — — — Pension obligation (c) 9 9 — — — 9 9 — — — Unamortized energy contract liabilities 22 22 — — — 39 39 — — — Other noncurrent liabilities 106 106 — — — 79 79 — — — Noncurrent liabilities 2,682 2,581 — 101 89 2,792 2,749 41 124 124 Total liabilities $ 3,356 $ 3,170 $ 42 $ 143 $ 126 $ 3,264 $ 3,135 $ 122 $ 172 $ 172 ___________ (a) Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity. (b) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. (c) Includes the CNEG retail gas pension obligation, which is presented as a net asset balance within the Prepaid pension asset line item on Generation’s balance sheet. See Note 17 - Retirement Benefits for additional details

Regulatory Matters (Tables)

Regulatory Matters (Tables)	12 Months Ended
	Dec. 31, 2016
Regulated Operations [Abstract]
Public Utilities General Disclosures [Table Text Block]	For each of the following years, the following total increases/(decreases) were included in ComEd’s, BGE’s, Pepco's, DPL's and ACE's electric transmission formula rate filings: ComEd BGE Annual Transmission Filings 2016 2015 2014 2016 2015 2014 Initial revenue requirement increase $ 90 $ 68 $ 36 $ 12 $ — $ 9 Annual reconciliation increase (decrease) 4 18 (14 ) 3 (3 ) 5 Dedicated facilities increase (a) — — — 13 13 3 Total revenue requirement increase $ 94 $ 86 $ 22 $ 28 $ 10 $ 17 Allowed return on rate base (c) 8.47 % 8.61 % 8.62 % 8.09 % 8.46 % 8.53 % Allowed ROE (d) 11.50 % 11.50 % 11.50 % 10.50 % 11.30 % 11.30 % Effective date of rates June 2016 June 2015 June 2014 June 2016 June 2015 June 2014 Pepco DPL ACE Annual Transmission Filings 2016 2015 2014 2016 2015 2014 2016 2015 2014 Initial revenue requirement increase (decrease) $ 2 $ 10 $ (9 ) $ 8 $ 15 $ 4 $ 8 $ 10 $ 4 Annual reconciliation (decrease) increase (10 ) (3 ) (1 ) (10 ) (1 ) 6 (14 ) 2 3 MAPP abandonment recovery (decrease) increase (b) (15 ) (2 ) 17 (12 ) (2 ) 15 — — — Total revenue requirement (decrease) increase $ (23 ) $ 5 $ 7 $ (14 ) $ 12 $ 25 $ (6 ) $ 12 $ 7 Allowed return on rate base (c) 7.88 % 8.36 % 8.60 % 7.21 % 7.80 % 8.05 % 7.83 % 8.51 % 8.66 % Allowed ROE (d) 10.50 % 11.30 % 11.30 % 10.50 % 11.30 % 11.30 % 10.50 % 11.30 % 11.30 % Effective date of rates (e) June 2016 June 2015 June 2014 June 2016 June 2015 June 2014 June 2016 June 2015 June 2014 ____________ (a) BGE's transmission revenues include a FERC approved dedicated facilities charge to recover the costs of providing transmission service to specifically designated load by BGE. For each of the following years, the ICC approved the following total increases/(decreases) in ComEd's electric distributions formula rate filings: Annual Electric Distribution Filings 2016 2015 2014 ComEd's requested total revenue requirement increase (decrease) $ 138 $ (50 ) $ 269 Final ICC Order Initial revenue requirement increase $ 134 $ 85 $ 160 Annual reconciliation (decrease) increase (7 ) (152 ) 72 Total revenue requirement increase (decrease) $ 127 (a) $ (67 ) $ 232 Allowed Return on Rate Base: Initial revenue requirement 6.71 % 7.05 % 7.06 % Annual reconciliation 6.69 % 7.02 % 7.04 % Allowed ROE: Initial revenue requirement 8.64 % 9.14 % 9.25 % Annual reconciliation 8.59 % (b) 9.09 % (b) 9.20 % (b) Effective date of rates January 2017 January 2016 January 2015 __________________ (a) On December 20, 2016, the ICC granted ComEd's and other parties' joint application for rehearing on the impact that changing ComEd’s OSHA recordable rate for 2014 and 2015 has on the revenue requirement approved in this order. ComEd has proposed that the 2016 total electric distribution revenue requirement be reduced by $18 million which would be refunded to customers in 2017. (b) Includes a reduction of 5 basis points for a reliability performance metric penalty. ComEd BGE Annual Transmission Filings 2016 2015 2014 2016 2015 2014 Initial revenue requirement increase $ 90 $ 68 $ 36 $ 12 $ — $ 9 Annual reconciliation increase (decrease) 4 18 (14 ) 3 (3 ) 5 Dedicated facilities increase (a) — — — 13 13 3 Total revenue requirement increase $ 94 $ 86 $ 22 $ 28 $ 10 $ 17 Allowed return on rate base (c) 8.47 % 8.61 % 8.62 % 8.09 % 8.46 % 8.53 % Allowed ROE (d) 11.50 % 11.50 % 11.50 % 10.50 % 11.30 % 11.30 % Effective date of rates June 2016 June 2015 June 2014 June 2016 June 2015 June 2014
Regulatory Construction Commitment	will work with PJM to continue to evaluate the scope and timing of any required construction projects. The Utility Registrant's estimated commitments are as follows: Total 2017 2018 2019 2020 2021 ComEd $ 97 $ 64 $ 28 $ 5 $ — $ — PECO 34 14 10 7 2 1 BGE 226 113 55 44 14 — Pepco 104 6 39 40 19 — DPL 63 47 16 — — — ACE 93 36 39 18 — —
Schedule of Regulatory Assets	Successor December 31, 2016 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory assets Pension and other postretirement benefits $ 4,162 $ — $ — $ — $ — $ — $ — $ — Deferred income taxes 2,016 75 1,583 98 260 171 38 51 AMI programs 701 164 49 230 258 174 84 — Under-recovered distribution service costs 188 188 — — — — — — Debt costs 124 42 1 7 81 17 9 6 Fair value of long-term debt 812 — — — 671 — — — Fair value of PHI's unamortized energy contracts 1,085 — — — 1,085 — — — Severance 5 — — 5 — — — — Asset retirement obligations 111 76 23 12 — — — — MGP remediation costs 305 278 26 1 — — — — Under-recovered uncollectible accounts 56 56 — — — — — — Renewable energy 260 258 — — 2 — — 2 Energy and transmission programs 89 23 — 38 28 6 5 17 Deferred storm costs 36 — — 1 35 12 5 18 Electric generation-related regulatory asset 10 — — 10 — — — — Rate stabilization deferral 7 — — 7 — — — — Energy efficiency and demand response programs 621 — 1 285 335 250 85 — Merger integration costs 25 — — 10 15 11 4 — Under-recovered revenue decoupling 27 — — 3 24 21 3 — COPCO acquisition adjustment 8 — — — 8 — 8 — Recoverable workers compensation and long-term disability costs 34 — — — 34 34 — — Vacation accrual 31 — 7 — 24 — 14 10 Securitized stranded costs 138 — — — 138 — — 138 CAP arrearage 11 — 11 — — — — — Removal costs 477 — — — 477 134 88 255 Other 49 7 9 5 29 22 5 4 Total regulatory assets 11,388 1,167 1,710 712 3,504 852 348 501 Less: current portion 1,342 190 29 208 653 162 59 96 Total noncurrent regulatory assets $ 10,046 $ 977 $ 1,681 $ 504 $ 2,851 $ 690 $ 289 $ 405 Predecessor December 31, 2015 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory assets Pension and other postretirement benefits $ 3,156 $ — $ — $ — $ 910 $ — $ — $ — Deferred income taxes 1,616 64 1,473 79 214 137 36 41 AMI programs 399 140 63 196 267 180 87 — Under-recovered distribution service costs 189 189 — — — — — — Debt costs 47 46 1 8 36 19 10 7 Fair value of long-term debt 162 — — — — — — — Severance 9 — — 9 — — — — Asset retirement obligations 108 67 22 19 1 1 — — MGP remediation costs 286 255 30 1 — — — — Under-recovered uncollectible accounts 52 52 — — — — — — Renewable energy 247 247 — — 6 — 1 5 Energy and transmission programs 84 43 1 40 33 9 11 13 Deferred storm costs 2 — — 2 43 19 6 18 Electric generation-related regulatory asset 20 — — 20 — — — — Rate stabilization deferral 87 — — 87 — — — — Energy efficiency and demand response programs 279 — 1 278 401 289 111 1 Merger integration costs 6 — — 6 — — — — Conservation voltage reduction 3 — — 3 — — — — Under-recovered revenue decoupling 30 — — 30 14 10 4 — COPCO acquisition adjustment — — — — — — 13 — Workers compensation and long-term disability costs — — — — 31 31 — — Vacation accrual 6 — 6 — 23 — 14 9 Securitized stranded costs — — — — 202 — — 202 CAP arrearage 7 — 7 — — — — — Removal costs — — — — 369 92 69 208 Other 29 10 13 3 32 14 9 8 Total regulatory assets 6,824 1,113 1,617 781 2,582 801 371 512 Less: current portion 759 218 34 267 305 140 72 98 Total noncurrent regulatory assets $ 6,065 $ 895 $ 1,583 $ 514 $ 2,277 $ 661 $ 299 $ 414
Schedule of Regulatory Liabilities	Predecessor December 31, 2015 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory liabilities Other postretirement benefits $ 94 $ — $ — $ — $ — $ — $ — $ — Nuclear decommissioning 2,577 2,172 405 — — — — — Removal costs 1,527 1,332 — 195 150 21 129 — Energy efficiency and demand response programs 92 52 40 — 1 — — 1 DLC program costs 9 — 9 — — — — — Electric distribution tax repairs 95 — 95 — — — — — Gas distribution tax repairs 28 — 28 — — — — — Energy and transmission programs 131 53 60 18 27 16 19 8 Over-recovered revenue decoupling 1 — — 1 — — — — Other 16 5 2 8 35 7 12 16 Total regulatory liabilities 4,570 3,614 639 222 213 44 160 25 Less: current portion 369 155 112 38 66 15 49 18 Total noncurrent regulatory liabilities $ 4,201 $ 3,459 $ 527 $ 184 $ 147 $ 29 $ 111 $ 7 Successor December 31, 2016 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory liabilities Other postretirement benefits $ 47 $ — $ — $ — $ — $ — $ — $ — Nuclear decommissioning 2,607 2,169 438 — — — — — Removal costs 1,601 1,324 — 141 136 18 118 — Deferred rent 39 — — — 39 — — — Energy efficiency and demand response programs 185 141 41 — 3 3 — — DLC program costs 8 — 8 — — — — — Electric distribution tax repairs 76 — 76 — — — — — Gas distribution tax repairs 20 — 20 — — — — — Energy and transmission programs 134 60 56 — 18 8 5 5 Other 72 4 5 19 41 2 17 20 Total regulatory liabilities 4,789 3,698 644 160 237 31 140 25 Less: current portion 602 329 127 50 79 11 43 25 Total noncurrent regulatory liabilities $ 4,187 $ 3,369 $ 517 $ 110 $ 158 $ 20 $ 97 $ — Predecessor December 31, 2015 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory assets Pension and other postretirement benefits $ 3,156 $ — $ — $ — $ 910 $ — $ — $ — Deferred income taxes 1,616 64 1,473 79 214 137 36 41 AMI programs 399 140 63 196 267 180 87 — Under-recovered distribution service costs 189 189 — — — — — — Debt costs 47 46 1 8 36 19 10 7 Fair value of long-term debt 162 — — — — — — — Severance 9 — — 9 — — — — Asset retirement obligations 108 67 22 19 1 1 — — MGP remediation costs 286 255 30 1 — — — — Under-recovered uncollectible accounts 52 52 — — — — — — Renewable energy 247 247 — — 6 — 1 5 Energy and transmission programs 84 43 1 40 33 9 11 13 Deferred storm costs 2 — — 2 43 19 6 18 Electric generation-related regulatory asset 20 — — 20 — — — — Rate stabilization deferral 87 — — 87 — — — — Energy efficiency and demand response programs 279 — 1 278 401 289 111 1 Merger integration costs 6 — — 6 — — — — Conservation voltage reduction 3 — — 3 — — — — Under-recovered revenue decoupling 30 — — 30 14 10 4 — COPCO acquisition adjustment — — — — — — 13 — Workers compensation and long-term disability costs — — — — 31 31 — — Vacation accrual 6 — 6 — 23 — 14 9 Securitized stranded costs — — — — 202 — — 202 CAP arrearage 7 — 7 — — — — — Removal costs — — — — 369 92 69 208 Other 29 10 13 3 32 14 9 8 Total regulatory assets 6,824 1,113 1,617 781 2,582 801 371 512 Less: current portion 759 218 34 267 305 140 72 98 Total noncurrent regulatory assets $ 6,065 $ 895 $ 1,583 $ 514 $ 2,277 $ 661 $ 299 $ 414
Purchase Of Receivables	December 31, 2016 and December 31, 2015 . Successor As of December 31, 2016 Exelon ComEd PECO BGE PHI Pepco DPL ACE Purchased receivables (c) $ 313 $ 87 $ 72 $ 59 $ 95 $ 63 $ 10 $ 22 Allowance for uncollectible accounts (a) (37 ) (14 ) (6 ) (4 ) (13 ) (7 ) (2 ) (4 ) Purchased receivables, net $ 276 $ 73 $ 66 $ 55 $ 82 $ 56 $ 8 $ 18 Predecessor As of December 31, 2015 Exelon ComEd PECO BGE PHI Pepco DPL ACE Purchased receivables (b)(c) $ 229 $ 103 $ 67 $ 59 $ 100 $ 70 $ 11 $ 19 Allowance for uncollectible accounts (a) (31 ) (16 ) (7 ) (8 ) (6 ) (4 ) — (2 ) Purchased receivables, net $ 198 $ 87 $ 60 $ 51 $ 94 $ 66 $ 11 $ 17 _________________________

Mergers, Acquisitions and Dis41

Mergers, Acquisitions and Dispositions (Tables)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2014
Business Combinations [Abstract]
Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination [Table Text Block]
Business Combination, Separately Recognized Transactions [Table Text Block]	The total purchase price consideration of approximately $7.1 billion for the PHI Merger consisted of cash paid to PHI shareholders, cash paid for PHI preferred securities and cash paid for PHI stock-based compensation equity awards as follows: (In millions of dollars, except per share data) Total Consideration Cash paid to PHI shareholders at $27.25 per share (254 million shares outstanding at March 23, 2016) $ 6,933 Cash paid for PHI preferred stock (a) 180 Cash paid for PHI stock-based compensation equity awards (b) 29 Total purchase price $ 7,142 _____________ (a) As of December 31, 2015 , the preferred stock was included in Other non-current assets on Exelon's Consolidated Balance Sheets. (b) PHI’s unvested time-based restricted stock units and performance-based restricted stock units issued prior to April 29, 2014 were immediately vested and paid in cash upon the close of the merger. PHI’s remaining unvested time-based restricted stock units as of the close of the merger were cancelled. There were no remaining unvested performance-based restricted stock units as of the close of the merger. Expected Payment Period Successor Description Pepco (a) DPL (a) ACE (a) PHI (a) Exelon (a) Rate credits 2016 - 2017 $ 91 $ 67 $ 101 $ 259 $ 259 Energy efficiency 2016 - 2021 — — — — 111 Charitable contributions 2016 - 2026 28 12 10 50 50 Delivery system modernization Q2 2016 — — — — 22 Green sustainability fund Q2 2016 — — — — 14 Workforce development 2016 - 2020 — — — — 24 Other 7 7 — 14 33 Total $ 126 $ 86 $ 111 $ 323 $ 513
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	Preliminary Purchase Price Allocation Current assets $ 1,441 Property, plant and equipment 11,088 Regulatory assets 5,015 Other assets 248 Goodwill 4,005 Total assets $ 21,797 Current liabilities $ 2,752 Unamortized energy contracts 1,515 Regulatory liabilities 297 Long-term debt, including current maturities 5,636 Deferred income taxes 3,447 Pension and OPEB liabilities 821 Other liabilities 187 Total liabilities $ 14,655 Total purchase price $ 7,142 The following table summarizes the acquisition-date fair value of the consideration transferred and the assets and liabilities assumed for the ConEdison Solutions acquisition by Generation as of September 1, 2016: Total consideration transferred $ 257 Identifiable assets acquired and liabilities assumed Working capital assets $ 204 Property, plant and equipment 2 Mark-to-market derivative assets 6 Unamortized energy contract assets 100 Customer relationships 9 Other assets 1 Total assets $ 322 Mark-to-market derivative liabilities $ (65 ) Total liabilities $ (65 ) Total net identifiable assets, at fair value $ 257	The following table summarizes the acquisition-date fair value of the consideration transferred and the assets and liabilities assumed for the Integrys acquisition by Generation: Total consideration transferred $ 332 Identifiable assets acquired and liabilities assumed Working capital assets $ 390 Mark-to-market derivative assets 184 Unamortized energy contract assets 115 Customer relationships 50 Working capital liabilities (196 ) Mark-to-market derivative liabilities (57 ) Unamortized energy contract liabilities (110 ) Deferred tax liability (16 ) Total net identifiable assets, at fair value $ 360 Bargain purchase gain (after-tax) $ 28
Business Acquisition, Pro Forma Information, Nonrecurring Adjustments [Table Text Block]	Year Ended December 31, 2016 (a) 2015 (b) Total operating revenues $ 32,342 $ 33,823 Net income attributable to common shareholders 1,562 2,618 Basic earnings per share $ 1.69 $ 2.85 Diluted earnings per share 1.69 2.84 ______________ (a) The amounts above exclude non-recurring costs directly related to the merger of $680 million and intercompany revenue of $171 million for year ended December 31, 2016 . (b) The amounts above exclude non-recurring costs directly related to the merger of $92 million and intercompany revenue of $559 million for the year ended December 31, 2015 .
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	) The following assets and liabilities of CENG were recorded within Generation’s Consolidated Balance Sheets as of the date of integration, adjusted for the modifications discussed above: Fair Values Exelon and Generation Current assets $ 499 Nuclear decommissioning trust fund 1,955 Property, plant and equipment 3,073 Nuclear fuel 482 Other assets 10 Total assets 6,019 Current liabilities 237 Asset retirement obligation 1,816 Pension and other employee benefit obligations 281 Unamortized energy contract liabilities 171 Other liabilities 114 Total liabilities 2,619 Total net assets $ 3,400
Restructuring and Related Costs [Table Text Block]	For the Year Ended December 31, Acquisition, Integration and Financing Costs (a) 2016 2015 Exelon (b) $ 143 $ 87 Generation 37 24 ComEd (c) (6 ) 9 PECO 5 4 BGE (c) (1 ) 5 Pepco (c) 28 3 DPL (c) 20 2 ACE 19 1 Successor Predecessor Acquisition, Integration and Financing Costs (a) March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 PHI (c) $ 69 $ 29 $ 19 ______________ (a) The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statements of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. Costs do not include merger commitments discussed above. (b) Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps. (c) For the year ended December 31, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million , $6 million , $11 million , $4 million , and $16 million incurred at ComEd, BGE, Pepco, DPL and PHI, respectively, that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 3 - Regulatory Matters for more information. Successor Exelon Generation ComEd PECO BGE PHI Pepco (b) DPL (c) ACE Severance benefits (a) $ 57 $ 9 $ 2 $ 1 $ 1 $ 44 $ 21 $ 13 $ 10 ______________ (a) The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $8 million , $2 million , $1 million , $1 million , $20 million , $12 million and $10 million , respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the year ended December 31, 2016 . (b) Pepco established a regulatory asset of $11 million as of December 31, 2016 , primarily for severance benefit costs related to the PHI merger. (c) DPL established a regulatory asset of $4 million as of December 31, 2016 , primarily for severance benefit costs related to the PHI merger. and 2015 , the Registrants recorded the following severance costs associated with ongoing severance benefits within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income: Exelon Generation (a) ComEd (a) PECO (a) BGE (a) Year ended December 31, 2016 $ 19 $ 13 $ 3 $ 1 $ 1 2015 18 15 2 — 1 Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 PHI (a) Severance Benefits $ 1 $ — $ — _______ (a) The amounts above for Generation, ComEd, PECO, BGE and PHI include immaterial amounts billed by BSC for the years ended December 31, 2016 and 2015 . Amounts included in the table below represent the severance liability recorded for employees of each Registrant and exclude amounts included at Exelon and billed through intercompany allocations: Successor Severance Liability Exelon Generation ComEd PECO BGE PHI (b) Pepco DPL ACE Balance at December 31, 2014 $ 50 $ 34 $ 2 $ — $ 2 $ — $ 1 $ — $ — Severance charges 16 10 2 — — — — — — Payments (31 ) (21 ) (1 ) — (1 ) — (1 ) — — Balance at December 31, 2015 $ 35 $ 23 $ 3 $ — $ 1 $ — $ — $ — $ — Severance charges (a) 99 22 2 — — 56 1 1 — Payments (46 ) (9 ) (2 ) — (1 ) (27 ) (1 ) (1 ) — Balance at December 31, 2016 $ 88 $ 36 $ 3 $ — $ — $ 29 $ — $ — $ — Predecessor Severance Liability PHI (b) Balance at December 31, 2014 $ 3 Severance charges — Payments (3 ) Balance at December 31, 2015 $ — ______________ (a) Includes salary continuance and health and welfare severance benefits. Amounts primarily represent benefits provided for the PHI post-merger integration and the cost management program. (b) For PHI, the successor period includes activity for the period from March 24, 2016 through December 31, 2016 . The PHI predecessor periods include activity for the year ended December 31, 2015 and the period January 1, 2016 through March 23, 2016 . There was no activity in the 2016 PHI predecessor period. , the Registrants recorded the following severance costs related to the cost management program within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income, pursuant to the authoritative guidance for ongoing severance plans: Exelon Generation ComEd PECO BGE Severance benefits (a) $ 23 $ 18 $ 3 $ 1 $ 1 _______ (a) The amounts above for Generation, ComEd, PECO and BGE include $7 million , $3 million , $1 million , and $1 million , respectively, for amounts billed by BSC through intercompany allocations for the year ended December 31, 2016 .

Investment in Constellation E42

Investment in Constellation Energy Nuclear Group, LLC (Tables)	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition [Table Text Block]	) The following assets and liabilities of CENG were recorded within Generation’s Consolidated Balance Sheets as of the date of integration, adjusted for the modifications discussed above: Fair Values Exelon and Generation Current assets $ 499 Nuclear decommissioning trust fund 1,955 Property, plant and equipment 3,073 Nuclear fuel 482 Other assets 10 Total assets 6,019 Current liabilities 237 Asset retirement obligation 1,816 Pension and other employee benefit obligations 281 Unamortized energy contract liabilities 171 Other liabilities 114 Total liabilities 2,619 Total net assets $ 3,400

Accounts Receivable (Tables)

Accounts Receivable (Tables)	12 Months Ended
	Dec. 31, 2016
Receivables [Abstract]
Schedule Of Accounts Notes Loans And Financing Receivable	Accounts receivable at December 31, 2016 and 2015 included estimated unbilled revenues, representing an estimate for the unbilled amount of energy or services provided to customers, and is net of an allowance for uncollectible accounts as follows: Successor 2016 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Unbilled customer revenues $ 1,673 $ 910 (a) $ 219 $ 140 $ 182 $ 222 $ 123 $ 58 $ 41 Allowance for uncollectible accounts (b) (334 ) (91 ) (70 ) (61 ) (c) (32 ) (80 ) (d) (29 ) (d) (24 ) (d) (27 ) (d) Predecessor 2015 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Unbilled customer revenues $ 1,203 $ 732 (a) $ 218 $ 105 $ 148 $ 177 $ 93 $ 45 $ 39 Allowance for uncollectible (b) (284 ) (77 ) (75 ) (83 ) (c) (49 ) (56 ) (17 ) (17 ) (17 ) _________________________ (a) Represents unbilled portion of retail receivables estimated under Exelon’s unbilled critical accounting policy. (b) Includes the allowance for uncollectible accounts on customer and other accounts receivable. (c) Excludes the non-current allowance for uncollectible accounts of $23 million and $8 million at December 31, 2016 and 2015 , respectively, related to PECO’s current installment plan receivables described below. (d) At December 31, 2016 , as explained in Note 1 — Significant Accounting Policies , PHI, Pepco, DPL and ACE estimated the allowance for uncollectible accounts on customer receivables by applying loss rates to the outstanding receivable balance by risk segment. The change in estimate resulted in an overall increase of $30 million , $14 million , $8 million , and $8 million in the allowance for uncollectible accounts with $20 million , $8 million , $4 million , and $8 million deferred as a regulatory asset on PHI's, Pepco's, DPL's and ACE's Consolidated Balance Sheets at December 31, 2016, respectively. This also resulted in a $10 million , $6 million , and $4 million pre-tax charge to provision for uncollectible accounts expense for the year ended December 31, 2016 , which is included in Operating and maintenance expense on PHI's, Pepco's, and DPL's Consolidated Statements of Operations and Comprehensive Income, respectively.

Property, Plant, and Equipment

Property, Plant, and Equipment (Tables)	12 Months Ended
	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—generation 3-56 $ 27,193 $ 25,615 Nuclear fuel (a) 1-8 6,546 6,384 Construction work in progress N/A 2,332 2,017 Other property, plant and equipment (b) 4 76 466 Total property, plant and equipment 36,147 34,482 Less: accumulated depreciation (c) 10,562 8,639 Property, plant and equipment, net $ 25,585 $ 25,843 _________________________ (a) Includes nuclear fuel that is in the fabrication and installation phase of $1,326 million and $1,266 million at December 31, 2016 and 2015 , respectively. (b) Includes buildings under capital lease with a net carrying value of $10 million and $13 million at December 31, 2016 and 2015 , respectively. The original cost basis of the buildings was $52 million , and total accumulated amortization was $42 million and $39 million , as of December 31, 2016 and 2015 , respectively. At December 31, 2015 these balances also include capitalized acquisition, development and exploration costs of $266 million related to oil and gas production activities at Generation, see Note 4 — Mergers, Acquisitions, and Dispositions for additional information regarding the sale of upstream assets. Includes the original cost and progress payments associated with Generation’s turbine equipment held for future use with a carrying value of $17 million and $146 million at December 31, 2016 and 2015 , respectively. See Note 8 — Impairment of Long-Lived Assets for additional information on the impairment of Generations turbine equipment. (c) Includes accumulated amortization of nuclear fuel in the reactor core of $3,186 million and $2,861 million as of December 31, 2016 and 2015 , respectively The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-80 $ 22,636 $ 20,576 Construction work in progress N/A 569 572 Other property, plant and equipment (a), (b) 37-50 67 64 Total property, plant and equipment 23,272 21,212 Less: accumulated depreciation 3,937 3,710 Property, plant and equipment, net $ 19,335 $ 17,502 _________________________ (a) Includes buildings under capital lease with a net carrying value at both December 31, 2016 and 2015 of $7 million . The original cost basis of the buildings was $8 million and total accumulated amortization was $1 million as of both December 31, 2016 and 2015 . (b) Includes land held for future use and non-utility property. The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service life 2016 2015 Asset Category Electric—transmission and distribution 5-68 $ 3,574 $ 3,431 Gas—distribution 5-75 580 547 Common—electric and gas 4-40 115 108 Construction work in progress N/A 163 107 Other property, plant and equipment (a) 10-43 16 16 Total property, plant and equipment 4,448 4,209 Less: accumulated depreciation 1,175 — 1,139 Property, plant and equipment, net $ 3,273 $ 3,070 _______________________ (a) Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien. The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-86 $ 8,018 $ 7,682 Construction work in progress N/A 537 318 Other property, plant and equipment (a) 10-33 66 91 Total property, plant and equipment 8,621 8,091 Less: accumulated depreciation 3,050 — 2,929 Property, plant and equipment, net $ 5,571 $ 5,162 _______________________ (a) Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien. The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-65 $ 7,591 $ 7,230 Gas—transportation and distribution 5-70 2,348 2,206 Common—electric and gas 5-50 670 631 Construction work in progress N/A 188 154 Other property, plant and equipment (a) 50 21 21 Total property, plant and equipment 10,818 10,242 Less: accumulated depreciation 3,253 3,101 Property, plant and equipment, net $ 7,565 $ 7,141 _________________________ (a) Represents land held for future use and non-utility property The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-90 $ 45,698 $ 32,546 Electric—generation 3-56 27,193 25,615 Gas—transportation and distribution 5-90 4,642 3,864 Common—electric and gas 4-50 1,312 1,149 Nuclear fuel (a) 1-8 6,546 6,384 Construction work in progress N/A 4,306 3,075 Other property, plant and equipment (b) 3-50 1,027 1,181 Total property, plant and equipment 90,724 73,814 Less: accumulated depreciation (c) 19,169 16,375 Property, plant and equipment, net $ 71,555 $ 57,439 _________________________ (a) Includes nuclear fuel that is in the fabrication and installation phase of $1,326 million and $1,266 million at December 31, 2016 and 2015 , respectively. (b) Includes Generation’s buildings under capital lease with a net carrying value of $10 million and $13 million at December 31, 2016 and 2015 , respectively. The original cost basis of the buildings was $52 million , and total accumulated amortization was $42 million and $39 million , as of December 31, 2016 and 2015 , respectively. Also includes ComEd’s buildings under capital lease with a net carrying value at both December 31, 2016 and 2015 , of $7 million . The original cost basis of the buildings was $8 million and total accumulated amortization was $1 million as of both December 31, 2016 and 2015 . Includes land held for future use and non utility property at ComEd, PECO, BGE, Pepco, DPL, and ACE of $60 million , $21 million , $32 million , $66 million , $16 million , and $27 million , respectively, at December 31, 2016 . At December 31, 2015 these balances also include capitalized acquisition, development and exploration costs of $266 million related to oil and gas production activities at Generation, see Note 4 — Mergers, Acquisitions, and Dispositions for additional information regarding the sale of upstream assets. Includes the original cost and progress payments associated with Generation’s turbine equipment held for future use with a carrying value of $17 million and $146 million at December 31, 2016 and 2015 , respectively. See Note 8 — Impairment of Long-Lived Assets for additional information on the impairment of Generations turbine equipment. (c) Includes accumulated amortization of nuclear fuel in the reactor core at Generation of $3,186 million and $2,861 million as of December 31, 2016 and 2015 , respectively The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-55 $ 3,341 $ 3,105 Construction work in progress N/A 169 158 Other property, plant and equipment (a) 13-15 27 28 Total property, plant and equipment 3,537 3,291 Less: accumulated depreciation 1,016 — 969 Property, plant and equipment, net $ 2,521 $ 2,322 _______________________ (a) The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Successor Predecessor Average 2016 2015 Asset Category Electric—transmission and distribution 5-86 $ 10,315 $ 14,563 Gas—distribution 5-75 414 547 Common—electric and gas 4-40 65 164 Construction work in progress N/A 892 591 Other property, plant and equipment (a) 3-43 107 339 Total property, plant and equipment 11,793 16,204 Less: accumulated depreciation 195 — 5,340 Property, plant and equipment, net $ 11,598 $ 10,864 _______________________ (a) Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien. The following table presents a summary of property, plant and equipment by asset category as of December 31, 2016 and 2015 : Average Service Life (years) 2016 2015 Asset Category Electric—transmission and distribution 5-90 $ 7,067 $ 6,663 Gas—distribution 5-90 2,170 1,951 Common—electric and gas 5-40 707 655 Construction work in progress N/A 318 312 Other property, plant and equipment (a) 20 32 32 Total property, plant and equipment 10,294 9,613 Less: accumulated depreciation 3,254 3,016 Property, plant and equipment, net $ 7,040 $ 6,597 _______________________ (a) Represents land held for future use and non-utility property
Property Plant And Equipment Average Service Life Percentage By Asset Category Table	The following table presents the annual depreciation provisions as a percentage of average service life for each asset category. Average Service Life Percentage by Asset Category 2016 2015 2014 Electric—transmission and distribution 2.32 % 2.39 % 2.55 % Gas 1.82 % 1.87 % 1.84 % Common—electric and gas 5.11 % 5.16 % 5.16 % The following table presents the annual depreciation provisions as a percentage of average service life for each asset category. Average Service Life Percentage by Asset Category 2016 2015 2014 Electric—transmission and distribution 2.49 % 2.44 % 2.41 % Gas 2.57 % 2.55 % 2.48 % Common—electric and gas 4.99 % 4.24 % 4.08 % The following table presents the annual depreciation provisions as a percentage of average service life for each asset category. Average Service Life Percentage by Asset Category 2016 2015 2014 Electric—transmission and distribution 2.56 % 2.62 % 2.96 % Gas 2.45 % 2.50 % 2.47 % Common—electric and gas 9.45 % 10.35 % 9.49 % The following table presents the annual depreciation provisions as a percentage of average service life for each asset category. Average Service Life Percentage by Asset Category 2016 2015 2014 Electric—transmission and distribution 2.52 % 2.48 % 2.42 % Gas 2.57 % 2.55 % 2.48 % Common—electric and gas 8.12 % 5.19 % 4.55 % The following table presents the annual depreciation provisions as a percentage of average service life for each asset category. Average Service Life Percentage by Asset Category 2016 2015 2014 Electric—transmission and distribution 2.73 % 2.83 % 2.93 % Electric—generation 5.94 % (a) 3.47 % 3.50 % Gas 2.17 % 2.17 % 2.13 % Common—electric and gas 7.41 % 7.79 % 7.32 %

Impairment of Long-Lived asse45

Impairment of Long-Lived assets (Tables)	12 Months Ended
	Dec. 31, 2016
Impairment or Disposal of Tangible Assets Disclosure [Abstract]
Schedule of Capital Leased Assets	As of December 31, 2016 , all the long-term leases had been terminated and no residual and net investment value was outstanding. At December 31, 2015 , the components of the net investment in the long-term leases consisted of estimated residual value of $639 million , unearned income of $287 million and a resulting net investment of $352 million .

Early Nuclear Plant Retiremen46

Early Nuclear Plant Retirements Early Nuclear Plant Retirements (Tables)	12 Months Ended
	Dec. 31, 2016
Implications of Potential Early Plant Retirements [Abstract]
Implications of Potential Early Plant Retirement [Table Text Block] [Table Text Block]	(in millions) TMI Asset Balances Materials and supplies inventory $ 39 Nuclear fuel inventory, net 83 Completed plant, net 1,015 Construction work in progress 37 Liability Balances Asset retirement obligation (565 ) NRC License Renewal Term 2034

Jointly Owned Electric Utilit47

Jointly Owned Electric Utility Plant (Tables)	12 Months Ended
	Dec. 31, 2016
Public Utilities, Property, Plant and Equipment [Abstract]
Schedule of Jointly Owned Utility Plants	Exelon's, Generation's, PECO's, BGE's, PHI's and ACE's undivided ownership interests in jointly owned electric plants and transmission facilities at December 31, 2016 and 2015 were as follows: Nuclear Generation Fossil Fuel Generation Transmission Other Quad Cities Peach Bottom Salem (a) Nine Mile Point Unit 2 Wyman PA (b) NJ/ DE (c) Other (d) Operator Generation Generation PSEG Nuclear Generation FP&L First Energy PSEG/ DPL various Ownership interest 75.00 % 50.00 % 42.59 % 82.00 % 5.89 % various various various Exelon’s share at December 31, 2016: Plant (e) $ 1,054 $ 1,384 $ 596 $ 830 $ 3 $ 27 $ 97 $ 15 Accumulated depreciation (e) 515 407 186 68 3 15 52 13 Construction work in progress — 16 41 37 — — — — Exelon’s share at December 31, 2015: Plant (e) $ 1,035 $ 1,345 $ 566 $ 756 $ 3 $ 27 $ 93 $ 15 Accumulated depreciation (e) 309 368 167 42 3 15 52 13 Construction work in progress 11 18 40 56 — — — — ________________________ (a) Generation also owns a proportionate share in the fossil fuel combustion turbine at Salem, which is fully depreciated. The gross book value was $3 million at December 31, 2016 and 2015 . (b) PECO, BGE, Pepco, DPL and ACE own a 22% , 7% , 27% , 9% and 8% share, respectively, in 127 miles of 500 kV lines located in Pennsylvania as well as a 20.72% , 10.56% , 9.72% , 3.72% and 3.83% share, respectively, of a 500 kV substation immediately outside of the Conemaugh fossil generating station which supplies power to the 500 kV lines including, but not limited to, the lines noted above. (c) PECO, DPL and ACE own a 42.55% , 1% and 13.9% share, respectively in 151.3 miles of 500 kV lines located in New Jersey and Delaware Station. PECO, DPL and ACE also own a 42.55% , 7.45% and 7.45% share, respectively, in 2.5 miles of 500 kV line located over the Delaware River. ACE also has a 21.78% share in a 500 kV New Freedom Switching (d) Generation, DPL and ACE own a 44.24% , 4.83% and 11.91% share, respectively in assets located at Merrill Creek Reservoir located in New Jersey. Pepco, DPL and ACE own a 11.9% , 7.4% and 6.6% share, respectively, in Valley Forge Corporate Center. (e) Excludes asset retirement costs.

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule Of Goodwill	Exelon’s, Generation's, ComEd’s, PHI's, and DPL's gross amount of goodwill, accumulated impairment losses and carrying amount of goodwill for the years ended December 31, 2016 and 2015 were as follows: Balance at January 1, 2015 Impairment losses Balance at December 31, 2015 Goodwill from business combination Impairment losses Measurement period adjustments (b) Balance at December 31, 2016 Exelon Gross amount $ 4,655 $ — $ 4,655 $ 4,016 $ — $ (11 ) $ 8,660 Accumulated impairment loss 1,983 — 1,983 — — — 1,983 Carrying amount 2,672 — 2,672 4,016 — (11 ) 6,677 Generation Gross amount 47 — 47 — — — 47 Carrying amount 47 — 47 — — — 47 ComEd (a) Gross amount 4,608 — 4,608 — — — 4,608 Accumulated impairment loss 1,983 — 1,983 — — — 1,983 Carrying amount 2,625 — 2,625 — — — 2,625 DPL Gross amount 8 — 8 — — — 8 Carrying amount 8 — 8 — — — 8 March 24, 2016 to December 31, 2016 Beginning Balance Goodwill from business combination Impairment losses Measurement period adjustments (b) Ending Balance PHI - Successor Gross amount $ — $ 4,016 $ — $ (11 ) $ 4,005 Accumulated impairment loss — — — — — Carrying amount — 4,016 — (11 ) 4,005 January 1, 2016 to March 23, 2016 PHI - Predecessor Gross amount 1,418 — — — 1,418 Accumulated impairment loss 12 — — — 12 Carrying amount 1,406 — — — 1,406 For the Year Ended December 31, 2015 PHI - Predecessor Gross amount 1,425 — (7 ) — 1,418 Accumulated impairment loss 18 — (6 ) — 12 Carrying amount 1,407 — (1 ) — 1,406 ______________________ (a) Reflects goodwill recorded in 2000 from the PECO/Unicom (predecessor parent company of ComEd) merger net of amortization, resolution of tax matters and other non-impairment-related changes as allowed under previous authoritative guidance.
Schedule of Finite-Lived Intangible Assets	Exelon’s, Generation’s, ComEd’s and PHI's other intangible assets and liabilities, included in Unamortized energy contract assets and liabilities and Other deferred debits and other assets in their Consolidated Balance Sheets, consisted of the following as of December 31, 2016 : Weighted Average Amortization Years (l) Estimated amortization expense Gross Accumulated Amortization Net 2017 2018 2019 2020 2021 Exelon Software License Agreement (a) 10.0 $ 95 $ (15 ) $ 80 $ 10 $ 10 $ 10 $ 10 $ 10 Generation Unamortized Energy Contracts (b) Exelon Wind (c) 18.0 224 (83 ) 141 14 14 14 10 10 Antelope Valley (d) 25 190 (28 ) 162 8 8 8 8 8 Constellation (e) 1.5 1,499 (1,440 ) 59 (21 ) 11 8 10 10 CENG (f) 1.7 (97 ) 59 (38 ) (15 ) (18 ) (15 ) (8 ) (4 ) Integrys (g) 2.4 5 (3 ) 2 1 1 — — — ConEdison (h) 1.5 100 (53 ) 47 37 7 2 1 — Service Contract Backlog PES (h) 1.0 9 (7 ) 2 2 — — — — Customer Relationships (i) Constellation (e) 12.4 214 (94 ) 120 18 18 17 17 17 Integrys (g) 10.0 50 (11 ) 39 5 5 5 5 5 PES (h) 15.0 12 (1 ) 11 1 1 1 1 1 ConEdison (h) 10.0 9 — 9 1 1 1 1 1 Trade Names Constellation (e) 10.0 243 (125 ) 118 23 23 23 23 23 ComEd Chicago settlement—1999 agreement (j) 21.8 100 (86 ) 14 3 3 3 3 — Chicago settlement—2003 agreement (k) 17.9 62 (47 ) 15 4 4 4 4 — PHI Unamortized Energy Contracts (h) 6.8 (1,515 ) 430 (1,085 ) (335 ) (189 ) (119 ) (115 ) (92 ) Pepco DC Sponsorship Agreement (m) 0 25 — 25 — — — — — Total $ 1,225 $ (1,504 ) $ (279 ) $ (244 ) $ (101 ) $ (38 ) $ (30 ) $ (11 ) _________________________ (a) On May 31, 2015, Exelon entered into a long-term software license agreement. Exelon is required to make payments starting August 2015 through May 2024. The intangible asset recognized as a result of these payments is being amortized on a straight-line basis over the contract term. (b) Includes unamortized energy contract assets and liabilities on Exelon's and Generation's Consolidated Balance Sheets. Excludes $10 million of other miscellaneous unamortized energy contracts that have been acquired at various points in time. The estimated amortization for these miscellaneous unamortized energy contracts is $(9) million , $(7) million , $(6) million , $(2) million and $4 million for 2017 , 2018 , 2019 , 2020 and 2021 , respectively. (c) In December 2010, Generation acquired all of the equity interests of John Deere Renewables, LLC (later named Exelon Wind), adding 735 MWs of installed, operating wind capacity located in eight states. (d) In September 2011, Generation acquired all of the interest in Antelope Valley Solar Ranch One, a 242 MW solar project in northern Los Angeles County, CA from First Solar, Inc. (e) On March 12, 2012, Constellation merged into Exelon with Exelon continuing as the surviving corporation pursuant to the transactions contemplated by the Agreement and Plan of Merger. Since the merger transaction, Generation includes the former Constellation generation and customer supply operations. (f) See Note 5 — Investment in Constellation Energy Nuclear Group, LLC for additional information. (g) On November 1, 2014, Generation acquired the competitive retail electric and natural gas business activities of Integrys Energy Group, Inc. (h) See Note 4 — Mergers, Acquisitions, and Dispositions for additional information. (i) Excludes $11 million of other miscellaneous customer relationships that have been acquired. The estimated amortization for these miscellaneous customer relationships is $1 million in each of the years from 2017 to 2021 . (j) In March 1999, ComEd entered into a settlement agreement with the City of Chicago associated with ComEd’s franchise agreement. Under the terms of the settlement, ComEd agreed to make payments to the City of Chicago each year from 1999 to 2002. The intangible asset recognized as a result of these payments is being amortized ratably over the remaining term of the franchise agreement, which ends in 2020. (k) In February 2003, ComEd entered into separate agreements with the City of Chicago and with Midwest Generation, LLC (Midwest Generation). Under the terms of the settlement agreement with the City of Chicago, ComEd agreed to pay the City of Chicago a total of $60 million over a ten -year period, beginning in 2003. The intangible asset recognized as a result of the settlement agreement is being amortized ratably over the remaining term of the City of Chicago franchise agreement, which ends in 2020. As required by the settlement, ComEd also made a payment of $2 million to a third-party on the City of Chicago’s behalf. Under the terms of the agreement with Midwest Generation, ComEd received payments of $32 million from Midwest Generation to relieve Midwest Generation’s obligation under the 1999 fossil sale agreement with ComEd to build the generation facility in the City of Chicago. The payments received by ComEd, which have been recorded in Other deferred credits and other liabilities, and other long-term liabilities on Exelon's and ComEd's Consolidated Balance Sheets are being recognized ratably (approximately $2 million annually) as an offset to amortization expense over the remaining term of the franchise agreement. (l) Weighted-average amortization period was calculated at the date of a) acquisition for acquired assets or b) settlement agreement. (m) In the third quarter of 2015, Pepco entered into a sponsorship agreement with the District of Columbia for future naming rights associated with public property within the District of Columbia to be determined over time through future negotiations. Amortization of the intangible asset will begin once the terms of the naming rights are defined.
Schedule Of Finite-Lived Intangible Assets Amortization Expense	The following table summarizes the amortization expense related to intangible assets and liabilities for each of the years ended December 31, 2016 , 2015 and 2014 : For the Year Ended December 31, Exelon (a) Generation (a) ComEd 2016 $ 87 $ 79 $ 7 2015 76 69 7 2014 179 179 7 ________________________ (a) At Exelon, amortization of unamortized energy contracts totaling $35 million , $22 million and $135 million for the years ended December 31, 2016 , 2015 and 2014 , respectively, was recorded in Operating revenues or Purchase power and fuel expense within Exelon’s Consolidated Statements of Operations and Comprehensive Income. At Generation, amortization of unamortized energy contracts totaling $35 million , $22 million and $135 million for the years ended December 31, 2016 , 2015 and 2014 , respectively, was recorded in Operating revenues or Purchase power and fuel expense within Generation’s Consolidated Statements of Operations and Comprehensive Income

Fair Value of Financial Asset49

Fair Value of Financial Assets and Liabilities (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Text Block]	The following tables present the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis during the year ended December 31, 2016 and 2015 : Successor Generation ComEd PHI (c) Exelon For the year ended December 31, 2016 NDT Fund Investments Pledged Assets Mark-to-Market Other Total Generation Mark-to-Market Derivatives (a) Life Insurance Contracts Eliminated in Consolidation Total Balance as of January 1, 2016 $ 670 $ 22 $ 1,051 $ 33 $ 1,776 $ (247 ) $ — $ — $ 1,529 Included due to merger — — — — — — 20 — 20 Total realized / unrealized gains (losses) Included in net income 7 — (568 ) (b) 1 (560 ) — 3 — (557 ) Included in noncurrent payables to affiliates 16 — — — 16 — — (16 ) — Included in regulatory assets/liabilities — — — — — (11 ) — 16 5 Change in collateral — — (141 ) — (141 ) — — — (141 ) Purchases, sales, issuances and settlements — Purchases 143 2 342 (d) 7 494 — — — 494 Sales (1 ) (5 ) (9 ) — (15 ) — — — (15 ) Issuances — — — — — — (3 ) — (3 ) Settlements (144 ) — — — (144 ) — — — (144 ) Transfers into Level 3 — — 1 1 2 — — — 2 Transfers out of Level 3 (14 ) — (183 ) — (197 ) — — — (197 ) Balance as of December 31, 2016 $ 677 $ 19 $ 493 $ 42 $ 1,231 $ (258 ) $ 20 $ — $ 993 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of December 31, 2016 $ 5 $ — $ 109 $ — $ 114 $ — $ 2 $ — $ 116 Generation ComEd Exelon For the year ended December 31, 2015 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives (d) Other Investments Total Generation Mark-to-Market Derivatives (a) Eliminated in Consolidation Total Balance as of January 1, 2015 $ 605 $ 50 $ 1,050 $ 3 $ 1,708 $ (207 ) $ — $ 1,501 Total realized / unrealized gains (losses) Included in net income 4 — 22 (b) 1 27 — — 27 Included in noncurrent payables to affiliates 18 — — — 18 — (18 ) — Included in payable for Zion Station decommissioning — (2 ) — — (2 ) — — (2 ) Included in regulatory assets/liabilities — — — — — (40 ) 18 (22 ) Change in collateral — — 29 — 29 — — 29 Purchases, sales, issuances and settlements Purchases 146 2 144 30 322 — — 322 Sales (8 ) (28 ) (25 ) — (61 ) — — (61 ) Settlements (95 ) — — — (95 ) — — (95 ) Transfers into Level 3 4 — 80 — 84 — — 84 Transfers out of Level 3 (4 ) — (249 ) (1 ) (254 ) — — (254 ) Balance as of December 31, 2015 $ 670 $ 22 $ 1,051 $ 33 $ 1,776 $ (247 ) $ — $ 1,529 The amount of total gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held as of December 31, 2015 $ 2 $ — $ 856 $ — $ 858 $ — $ — $ 858 _________________________ (a) Includes $29 million of decreases in fair value and an increase for realized losses due to settlements of $18 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the year ended December 31, 2016 . Includes $55 million of decreases in fair value and a reduction for realized losses due to settlements of $(15) million for the year ended December 31, 2015 . (b) Includes a reduction for the reclassification of $677 million and $834 million of realized gains due to the settlement of derivative contracts for the years ended December 31, 2016 and 2015 , respectively. (c) Successor period represents activity from March 24, 2016 to December 31, 2016 . See tables below for PHI's predecessor periods, as well as activity for Pepco and DPL for the year ended December 31, 2016 . (d) Includes $168 million of fair value from contracts acquired as a result of portfolio acquisitions. Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 December 31, 2015 PHI Life Insurance Contracts Preferred Stock Life Insurance Contracts Preferred Stock Life Insurance Contracts Beginning Balance $ 20 $ 18 $ 19 $ 3 $ 19 Total realized / unrealized gains (losses) Included in net income 3 (18 ) 1 15 5 Purchases, sales, issuances and settlements Issuances (3 ) — — — (3 ) Settlements — — — — (2 ) Ending Balance $ 20 $ — $ 20 $ 18 $ 19 The amount of total gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities for the period $ 2 $ — $ 1 $ 15 $ 3 December 31, 2016 December 31, 2015 Pepco DPL Pepco DPL Life Insurance Contracts Life Insurance Contracts Life Insurance Contracts Life Insurance Contracts Balance as of December 31 $ 19 $ — $ 18 $ 1 Total realized / unrealized gains (losses) Included in net income 3 — 5 — Purchases, sales, issuances and settlements Issuances (3 ) — (3 ) — Settlements — — (1 ) (1 ) Balance as of December 31 $ 19 $ — $ 19 $ — The amount of total gains included in income attributed to the change in unrealized gains related to assets and liabilities for the period $ 3 $ — $ 3 $ —
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]	ComEd, PECO and BGE The following tables present assets and liabilities measured and recorded at fair value on ComEd's, PECO's and BGE's Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and 2015 : ComEd PECO BGE As of December 31, 2016 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 20 $ — $ — $ 20 $ 45 $ — $ — $ 45 $ 36 $ — $ — $ 36 Rabbi trust investments Mutual funds — — — — 7 — — 7 4 — — 4 Life insurance contracts — — — — — 10 — 10 — — — — Rabbi trust investments subtotal — — — — 7 10 — 17 4 — — 4 Total assets 20 — — 20 52 10 — 62 40 — — 40 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (11 ) — (11 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (258 ) (258 ) — — — — — — — — Total liabilities — (8 ) (258 ) (266 ) — (11 ) — (11 ) — (4 ) — (4 ) Total net assets (liabilities) $ 20 $ (8 ) $ (258 ) $ (246 ) $ 52 $ (1 ) $ — $ 51 $ 40 $ (4 ) $ — $ 36 ComEd PECO BGE As of December 31, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 29 $ — $ — $ 29 $ 271 $ — $ — $ 271 $ 25 $ — $ — $ 25 Rabbi trust investments Mutual funds — — — — 8 — — 8 4 — — 4 Life insurance contracts — — — — — 12 — 12 — — — — Rabbi trust investments subtotal — — — — 8 12 — 20 4 — — 4 Total assets 29 — — 29 279 12 — 291 29 — — 29 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (12 ) — (12 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (247 ) (247 ) — — — — — — — — Total liabilities — (8 ) (247 ) (255 ) — (12 ) — (12 ) — (4 ) — (4 ) Total net assets (liabilities) $ 29 $ (8 ) $ (247 ) $ (226 ) $ 279 $ — $ — $ 279 $ 29 $ (4 ) $ — $ 25 _________________________ (a) ComEd excludes cash of $36 million and $38 million at December 31, 2016 and 2015 and restricted cash of $2 million and $2 million at December 31, 2016 and 2015 . PECO excludes cash of $22 million and $27 million at December 31, 2016 and 2015 . BGE excludes cash of $13 million and $6 million at December 31, 2016 and 2015 and restricted cash of less than $1 million and $2 million at December 31, 2016 and 2015 and includes long term restricted cash of $2 million at December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) The Level 3 balance consists of the current and noncurrent liability of $19 million and $239 million , respectively, at December 31, 2016 , and $23 million and $224 million , respectively, at December 31, 2015 , related to floating-to-fixed energy swap contracts with unaffiliated suppliers. The following tables present assets and liabilities measured and recorded at fair value on Exelon's and Generation’s Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and 2015 : Generation Exelon As of December 31, 2016 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 39 $ — $ — $ — $ 39 $ 373 $ — $ — $ — $ 373 NDT fund investments Cash equivalents (b) 110 19 — — 129 110 19 — — 129 Equities 3,551 452 — 2,011 6,014 3,551 452 — 2,011 6,014 Fixed income Corporate debt — 1,554 250 — 1,804 — 1,554 250 — 1,804 U.S. Treasury and agencies 1,291 29 — — 1,320 1,291 29 — — 1,320 Foreign governments — 37 — — 37 — 37 — — 37 State and municipal debt — 264 — — 264 — 264 — — 264 Other (c) — 59 — 493 552 — 59 — 493 — 552 Fixed income subtotal 1,291 1,943 250 493 3,977 1,291 1,943 250 493 3,977 Middle market lending — — 427 71 498 — — 427 71 498 Private equity — — — 148 148 — — — 148 148 Real estate — — — 326 326 — — — 326 326 NDT fund investments subtotal (d) 4,952 2,414 677 3,049 11,092 4,952 2,414 677 3,049 11,092 Pledged assets for Zion Station decommissioning Cash equivalents 11 — — — 11 11 — — — 11 Equities — 2 — — 2 — 2 — — 2 Fixed Income - U.S. Treasury and agencies 16 1 — — 17 16 1 — — 17 Middle market lending — — 19 64 83 — — 19 64 83 Pledged assets for Zion Station decommissioning subtotal (e) 27 3 19 64 113 27 3 19 64 113 Rabbi trust investments Cash equivalents 2 — — — 2 74 — — — 74 Mutual funds 19 — — — 19 50 — — — 50 Generation Exelon As of December 31, 2016 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Fixed income — — — — — — 16 — — 16 Life insurance contracts — 18 — — 18 — 64 20 — 84 Rabbi trust investments subtotal 21 18 — — 39 124 80 20 — 224 Commodity derivative assets Economic hedges 1,356 2,505 1,229 — 5,090 1,358 2,505 1,229 — 5,092 Proprietary trading 3 50 23 — 76 3 50 23 — 76 Effect of netting and allocation of collateral (f) (1,162 ) (2,142 ) (481 ) — (3,785 ) (1,164 ) (2,142 ) (481 ) — (3,787 ) Commodity derivative assets subtotal 197 413 771 — 1,381 197 413 771 — 1,381 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 16 — — 16 Economic hedges — 28 — — 28 — 28 — — 28 Proprietary trading 3 2 — — 5 3 2 — — 5 Effect of netting and allocation of collateral (2 ) (19 ) — — (21 ) (2 ) (19 ) — — (21 ) Interest rate and foreign currency derivative assets subtotal 1 11 — — 12 1 27 — — 28 Other investments — — 42 — 42 — — 42 — 42 Total assets 5,237 2,859 1,509 3,113 12,718 5,674 2,937 1,529 3,113 13,253 Liabilities Commodity derivative liabilities Economic hedges (1,267 ) (2,378 ) (794 ) — (4,439 ) (1,267 ) (2,378 ) (1,052 ) — (4,697 ) Proprietary trading (3 ) (50 ) (26 ) — (79 ) (3 ) (50 ) (26 ) — (79 ) Effect of netting and allocation of collateral (f) 1,233 2,339 542 — 4,114 1,233 2,339 542 — 4,114 Commodity derivative liabilities subtotal (37 ) (89 ) (278 ) — (404 ) (37 ) (89 ) (536 ) — (662 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (10 ) — — (10 ) — (10 ) — — (10 ) Economic hedges — (21 ) — — (21 ) — (21 ) — — (21 ) Proprietary trading (4 ) — — — (4 ) (4 ) — — — (4 ) Effect of netting and allocation of collateral 4 19 — — 23 4 19 — — 23 Interest rate and foreign currency derivative liabilities subtotal — (12 ) — — (12 ) — (12 ) — — (12 ) Deferred compensation obligation — (34 ) — — (34 ) — (136 ) — (136 ) Total liabilities (37 ) (135 ) (278 ) — (450 ) (37 ) (237 ) (536 ) — (810 ) Total net assets $ 5,200 $ 2,724 $ 1,231 $ 3,113 $ 12,268 $ 5,637 $ 2,700 $ 993 $ 3,113 $ 12,443 Generation Exelon As of December 31, 2015 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 104 $ — $ — $ — $ 104 $ 5,766 $ — $ — $ — $ 5,766 NDT fund investments Cash equivalents (b) 219 92 — — 311 219 92 — — 311 Equities 3,008 — — 1,894 4,902 3,008 — — 1,894 4,902 Generation Exelon As of December 31, 2015 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Fixed income Corporate debt — 1,824 242 — 2,066 — 1,824 242 — 2,066 U.S. Treasury and agencies 1,323 15 — — 1,338 1,323 15 — — 1,338 Foreign governments — 61 — — 61 — 61 — — 61 State and municipal debt — 326 — — 326 — 326 — — 326 Other (c) — 147 — 390 537 — 147 — 390 537 Fixed income subtotal 1,323 2,373 242 390 4,328 1,323 2,373 242 390 4,328 Middle market lending — — 428 — 428 — — 428 — 428 Private equity — — — 125 125 — — — 125 125 Real estate — — — 35 35 — — — 35 35 Other — — — 216 216 — — — 216 216 Nuclear decommissioning trust fund investments subtotal (d) 4,550 2,465 670 2,660 10,345 4,550 2,465 670 2,660 10,345 Pledged assets for Zion Station decommissioning Cash equivalents — 17 — — 17 — 17 — — 17 Equities 1 5 — — 6 1 5 — — 6 Fixed income U.S. Treasury and agencies 6 2 — — 8 6 2 — — 8 Corporate debt — 46 — — 46 — 46 — — 46 Other — 1 — — 1 — 1 — — 1 Fixed income subtotal 6 49 — — 55 6 49 — — 55 Middle market lending — — 22 105 127 — — 22 105 127 Pledged assets for Zion Station decommissioning subtotal (e) 7 71 22 105 205 7 71 22 105 205 Rabbi trust investments Mutual funds 17 — — — 17 48 — — — 48 Life insurance contracts — 13 — — 13 — 36 — — 36 Rabbi trust investments subtotal 17 13 — — 30 48 36 — — 84 Commodity derivative assets Economic hedges 1,922 3,467 1,707 — 7,096 1,922 3,467 1,707 — 7,096 Proprietary trading 36 64 30 — 130 36 64 30 — 130 Effect of netting and allocation of collateral (f) (1,964 ) (2,629 ) (564 ) — (5,157 ) (1,964 ) (2,629 ) (564 ) — (5,157 ) Commodity derivative assets subtotal (6 ) 902 1,173 — 2,069 (6 ) 902 1,173 — 2,069 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 25 — — 25 Economic hedges — 20 — — 20 — 20 — — 20 Proprietary trading 10 5 — — 15 10 5 — — 15 Effect of netting and allocation of collateral (3 ) (3 ) — — (6 ) (3 ) (3 ) — — (6 ) Interest rate and foreign currency derivative assets subtotal 7 22 — — 29 7 47 — — 54 Other investments — — 33 — 33 — — 33 — 33 Total assets 4,679 3,473 1,898 2,765 12,815 10,372 3,521 1,898 2,765 18,556 Liabilities Commodity derivative liabilities Generation Exelon As of December 31, 2015 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Economic hedges (2,382 ) (3,348 ) (850 ) — (6,580 ) (2,382 ) (3,348 ) (1,097 ) — (6,827 ) Proprietary trading (33 ) (57 ) (37 ) — (127 ) (33 ) (57 ) (37 ) — (127 ) Effect of netting and allocation of collateral (f) 2,440 3,186 765 — 6,391 2,440 3,186 765 — 6,391 Commodity derivative liabilities subtotal 25 (219 ) (122 ) — (316 ) 25 (219 ) (369 ) — (563 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (16 ) — — (16 ) — (16 ) — — (16 ) Economic hedges — (3 ) — — (3 ) — (3 ) — — (3 ) Proprietary trading (12 ) — — — (12 ) (12 ) — — — (12 ) Effect of netting and allocation of collateral 12 3 — — 15 12 3 — — 15 Interest rate and foreign currency derivative liabilities subtotal — (16 ) — — (16 ) — (16 ) — — (16 ) Deferred compensation obligation — (30 ) — — (30 ) — (99 ) — — (99 ) Total liabilities 25 (265 ) (122 ) — (362 ) 25 (334 ) (369 ) — (678 ) Total net assets $ 4,704 $ 3,208 $ 1,776 $ 2,765 $ 12,453 $ 10,397 $ 3,187 $ 1,529 $ 2,765 $ 17,878 _________________________ (a) Generation excludes cash of $252 million and $329 million at December 31, 2016 and 2015 and restricted cash of $157 million and $121 million at December 31, 2016 and 2015 . Exelon excludes cash of $360 million and $763 million at December 31, 2016 and 2015 and restricted cash of $180 million and $178 million at December 31, 2016 and 2015 and includes long term restricted cash of $25 million at December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) Includes $29 million and $52 million of cash received from outstanding repurchase agreements at December 31, 2016 and 2015 , respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (d) below. (c) Includes derivative instruments of $(2) million and $(8) million , which have a total notional amount of $933 million and $1,236 million at December 31, 2016 and 2015 , respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the fiscal years ended and do not represent the amount of the company's exposure to credit or market loss. (d) Excludes net liabilities of $(31) million and $(3) million at December 31, 2016 and 2015 , respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, repurchase agreement obligations, and payables related to pending securities purchases. The repurchase agreements are generally short-term in nature with durations generally of 30 days or less. (e) Excludes net assets of less than $1 million and $1 million at December 31, 2016 and 2015 , respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (f) Collateral posted to/(received from) counterparties totaled $71 million , $197 million and $61 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2016 . Collateral posted to/(received from) counterparties totaled $476 million , $557 million and $201 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2015 . PHI, Pepco, DPL and ACE The following tables present assets and liabilities measured and recorded at fair value on PHI's, Pepco's, DPL's and ACE's Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and December 31, 2015 : Successor Predecessor As of December 31, 2016 As of December 31, 2015 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 217 $ — $ — $ 217 $ 42 $ — $ — $ 42 Mark-to-market derivative assets (b)(c) 2 — — 2 — — 18 18 Effect of netting and allocation of collateral (2 ) — — (2 ) — — — — Mark-to-market derivative assets subtotal — — — — — — 18 18 Rabbi trust investments Cash equivalents 73 — — 73 12 — — 12 Fixed income — 16 — 16 — 15 — 15 Life insurance contracts — 22 20 42 — 27 19 46 Rabbi trust investments subtotal 73 38 20 131 12 42 19 73 Total assets 290 38 20 348 54 42 37 133 Liabilities Deferred compensation obligation — (28 ) — (28 ) — (30 ) — (30 ) Mark-to-market derivative liabilities (b) — — — — (2 ) — — (2 ) Effect of netting and allocation of collateral — — — — 2 — — 2 Mark-to-market derivative liabilities subtotal — — — — — — — — Total liabilities — (28 ) — (28 ) — (30 ) — (30 ) Total net assets $ 290 $ 10 $ 20 $ 320 $ 54 $ 12 $ 37 $ 103 Pepco DPL ACE As of December 31, 2016 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 33 $ — $ — $ 33 $ 42 $ — $ — $ 42 $ 130 $ — $ — $ 130 Mark-to-market derivative assets (b) — — — — 2 — — 2 — — — — Effect of netting and allocation of collateral — — — — (2 ) — — (2 ) — — — — Mark-to-market derivative assets subtotal — — — — — — — — — — — — Rabbi trust investments Cash equivalents 43 — — 43 — — — — — — — — Fixed income — 16 — 16 — — — — — — — — Life insurance contracts — 22 19 41 — — — — — — — — Rabbi trust investments subtotal 43 38 19 100 — — — — — — — — Total assets 76 38 19 133 42 — — 42 130 — — 130 Liabilities Deferred compensation obligation — (5 ) — (5 ) — (1 ) — (1 ) — — — — Total liabilities — (5 ) — (5 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 76 $ 33 $ 19 $ 128 $ 42 $ (1 ) $ — $ 41 $ 130 $ — $ — $ 130 Pepco DPL ACE As of December 31, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 2 $ — $ — $ 2 $ — $ — $ — $ — $ 30 $ — $ — $ 30 Rabbi trust investments Cash equivalents 11 — — 11 — — — — — — — — Fixed income — 15 — 15 — — — — — — — — Life insurance contracts — 23 19 42 — — — — — — — — Rabbi trust investments subtotal 11 38 19 68 — — — — — — — — Total assets 13 38 19 70 — — — — 30 — — 30 Liabilities Deferred compensation obligation — (6 ) — (6 ) — (1 ) — (1 ) — — — — Mark-to-market derivative liabilities (b) — — — — (2 ) — — (2 ) — — — — Effect of netting and allocation of collateral — — — — 2 — — 2 — — — — Mark-to-market derivative liabilities subtotal — — — — — — — — — — — — Total liabilities — (6 ) — (6 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 13 $ 32 $ 19 $ 64 $ — $ (1 ) $ — $ (1 ) $ 30 $ — $ — $ 30 _______ (a) PHI excludes cash of $19 million and $16 million at December 31, 2016 and 2015 and includes long term restricted cash of $23 million and $18 million at December 31, 2016 and 2015 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $9 million and $5 million at December 31, 2016 and 2015 . DPL excludes cash of $4 million and $5 million at December 31, 2016 and 2015 . ACE excludes cash of $3 million and $3 million at December 31, 2016 and 2015 and includes long term restricted cash of $23 million and $18 million at December 31, 2016 and 2015 which is reported in other deferred debits on the balance sheet. (b) Represents natural gas futures purchased by DPL as part of a natural gas hedging program approved by the DPSC. (c) Prior to the PHI Merger, PHI recorded derivative assets for the embedded call and redemption features on the shares of Preferred Stock outstanding as of December 31, 2015. See Note 19 - Mezzanine Equity for additional information. As a result of the PHI Merger, the PHI preferred stock derivative was reduced to zero as of March 23, 2016 .
Fair value of financial liabilities recorded at the carrying amount	The following tables present the carrying amounts and fair values of the Registrants’ short-term liabilities, long-term debt, SNF obligation, and trust preferred securities (long-term debt to financing trusts or junior subordinated debentures) as of December 31, 2016 and 2015 : Exelon December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 1,267 $ — $ 1,267 $ — $ 1,267 Long-term debt (including amounts due within one year) (a) 34,005 1,113 31,741 1,959 34,813 Long-term debt to financing trusts (b) 641 — — 667 667 SNF obligation 1,024 — 732 — 732 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 536 $ 3 $ 533 $ — $ 536 Long-term debt (including amounts due within one year) (a) 25,145 931 23,644 1,349 25,924 Long-term debt to financing trusts (b) 641 — — 673 673 SNF obligation 1,021 — 818 — 818 Generation December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 699 $ — $ 699 $ — $ 699 Long-term debt (including amounts due within one year) (a) 9,241 — 7,482 1,670 9,152 SNF obligation 1,024 — 732 — 732 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 29 $ — $ 29 $ — $ 29 Long-term debt (including amounts due within one year) (a) 8,959 — 7,767 1,349 9,116 SNF obligation 1,021 — 818 — 818 ComEd December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 7,033 $ — $ 7,585 $ — $ 7,585 Long-term debt to financing trusts (b) 205 — — 215 215 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 294 $ — $ 294 $ — $ 294 Long-term debt (including amounts due within one year) (a) 6,509 — 7,069 — 7,069 Long-term debt to financing trusts (b) 205 — — 213 213 PECO December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,580 $ — $ 2,794 $ — $ 2,794 Long-term debt to financing trusts 184 — — 192 192 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,580 $ — $ 2,786 $ — $ 2,786 Long-term debt to financing trusts 184 — — 195 195 BGE December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 45 $ — $ 45 $ — $ 45 Long-term debt (including amounts due within one year) (a) 2,322 — 2,467 — 2,467 Long-term debt to financing trusts (b) 252 — — 260 260 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 213 $ 3 $ 210 $ — $ 213 Long-term debt (including amounts due within one year) (a) 1,858 — 2,044 — 2,044 Long-term debt to financing trusts (b) 252 — — 264 264 PHI December 31, 2016 Carrying Amount Fair Value Successor Level 1 Level 2 Level 3 Total Short-term liabilities $ 522 $ — $ 522 $ — $ 522 Long-term debt (including amounts due within one year) (a) 5,898 — 5,520 289 5,809 December 31, 2015 Carrying Amount Fair Value Predecessor Level 1 Level 2 Level 3 Total Short-term liabilities $ 958 $ — $ 958 $ — $ 958 Long-term debt (including amounts due within one year) (a) 5,279 — 5,231 586 5,817 Preferred stock 183 — — 183 183 Pepco December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 23 $ — $ 23 $ — $ 23 Long-term debt (including amounts due within one year) (a) 2,349 — 2,788 8 2,796 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 64 $ — $ 64 $ — $ 64 Long-term debt (including amounts due within one year) (a) 2,351 — 2,673 — 2,673 DPL December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 1,340 $ — $ 1,383 $ — $ 1,383 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 105 $ — $ 105 $ — $ 105 Long-term debt (including amounts due within one year) (a) 1,265 — 1,185 103 1,288 ACE December 31, 2016 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 1,155 $ — $ 1,007 $ 280 $ 1,287 December 31, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 5 $ — $ 5 $ — $ 5 Long-term debt (including amounts due within one year) (a) 1,201 — 1,044 280 1,324 ________ (a) Includes unamortized debt issuance costs, which are not fair valued, of $200 million , $64 million , $46 million , $15 million , $15 million , $2 million , $30 million , $11 million , and $6 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE respectively, as of December 31, 2016 . Includes unamortized debt issuance costs, which are not fair valued, of $180 million , $70 million , $38 million , $15 million , $9 million , $49 million , $31 million , $10 million , and $6 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE respectively, as of December 31, 2015 . (b) Includes unamortized debt issuance costs which are not fair valued of $7 million , $1 million and $6 million for Exelon, ComEd and BGE, respectively, as of December 31, 2016 and December 31, 2015 .
Assets and liabilities measured and recorded at fair value on recurring basis	ComEd, PECO and BGE The following tables present assets and liabilities measured and recorded at fair value on ComEd's, PECO's and BGE's Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and 2015 : ComEd PECO BGE As of December 31, 2016 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 20 $ — $ — $ 20 $ 45 $ — $ — $ 45 $ 36 $ — $ — $ 36 Rabbi trust investments Mutual funds — — — — 7 — — 7 4 — — 4 Life insurance contracts — — — — — 10 — 10 — — — — Rabbi trust investments subtotal — — — — 7 10 — 17 4 — — 4 Total assets 20 — — 20 52 10 — 62 40 — — 40 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (11 ) — (11 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (258 ) (258 ) — — — — — — — — Total liabilities — (8 ) (258 ) (266 ) — (11 ) — (11 ) — (4 ) — (4 ) Total net assets (liabilities) $ 20 $ (8 ) $ (258 ) $ (246 ) $ 52 $ (1 ) $ — $ 51 $ 40 $ (4 ) $ — $ 36 ComEd PECO BGE As of December 31, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 29 $ — $ — $ 29 $ 271 $ — $ — $ 271 $ 25 $ — $ — $ 25 Rabbi trust investments Mutual funds — — — — 8 — — 8 4 — — 4 Life insurance contracts — — — — — 12 — 12 — — — — Rabbi trust investments subtotal — — — — 8 12 — 20 4 — — 4 Total assets 29 — — 29 279 12 — 291 29 — — 29 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (12 ) — (12 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (247 ) (247 ) — — — — — — — — Total liabilities — (8 ) (247 ) (255 ) — (12 ) — (12 ) — (4 ) — (4 ) Total net assets (liabilities) $ 29 $ (8 ) $ (247 ) $ (226 ) $ 279 $ — $ — $ 279 $ 29 $ (4 ) $ — $ 25 _________________________ (a) ComEd excludes cash of $36 million and $38 million at December 31, 2016 and 2015 and restricted cash of $2 million and $2 million at December 31, 2016 and 2015 . PECO excludes cash of $22 million and $27 million at December 31, 2016 and 2015 . BGE excludes cash of $13 million and $6 million at December 31, 2016 and 2015 and restricted cash of less than $1 million and $2 million at December 31, 2016 and 2015 and includes long term restricted cash of $2 million at December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) The Level 3 balance consists of the current and noncurrent liability of $19 million and $239 million , respectively, at December 31, 2016 , and $23 million and $224 million , respectively, at December 31, 2015 , related to floating-to-fixed energy swap contracts with unaffiliated suppliers. The following tables present assets and liabilities measured and recorded at fair value on Exelon's and Generation’s Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and 2015 : Generation Exelon As of December 31, 2016 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 39 $ — $ — $ — $ 39 $ 373 $ — $ — $ — $ 373 NDT fund investments Cash equivalents (b) 110 19 — — 129 110 19 — — 129 Equities 3,551 452 — 2,011 6,014 3,551 452 — 2,011 6,014 Fixed income Corporate debt — 1,554 250 — 1,804 — 1,554 250 — 1,804 U.S. Treasury and agencies 1,291 29 — — 1,320 1,291 29 — — 1,320 Foreign governments — 37 — — 37 — 37 — — 37 State and municipal debt — 264 — — 264 — 264 — — 264 Other (c) — 59 — 493 552 — 59 — 493 — 552 Fixed income subtotal 1,291 1,943 250 493 3,977 1,291 1,943 250 493 3,977 Middle market lending — — 427 71 498 — — 427 71 498 Private equity — — — 148 148 — — — 148 148 Real estate — — — 326 326 — — — 326 326 NDT fund investments subtotal (d) 4,952 2,414 677 3,049 11,092 4,952 2,414 677 3,049 11,092 Pledged assets for Zion Station decommissioning Cash equivalents 11 — — — 11 11 — — — 11 Equities — 2 — — 2 — 2 — — 2 Fixed Income - U.S. Treasury and agencies 16 1 — — 17 16 1 — — 17 Middle market lending — — 19 64 83 — — 19 64 83 Pledged assets for Zion Station decommissioning subtotal (e) 27 3 19 64 113 27 3 19 64 113 Rabbi trust investments Cash equivalents 2 — — — 2 74 — — — 74 Mutual funds 19 — — — 19 50 — — — 50 Generation Exelon As of December 31, 2016 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Fixed income — — — — — — 16 — — 16 Life insurance contracts — 18 — — 18 — 64 20 — 84 Rabbi trust investments subtotal 21 18 — — 39 124 80 20 — 224 Commodity derivative assets Economic hedges 1,356 2,505 1,229 — 5,090 1,358 2,505 1,229 — 5,092 Proprietary trading 3 50 23 — 76 3 50 23 — 76 Effect of netting and allocation of collateral (f) (1,162 ) (2,142 ) (481 ) — (3,785 ) (1,164 ) (2,142 ) (481 ) — (3,787 ) Commodity derivative assets subtotal 197 413 771 — 1,381 197 413 771 — 1,381 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 16 — — 16 Economic hedges — 28 — — 28 — 28 — — 28 Proprietary trading 3 2 — — 5 3 2 — — 5 Effect of netting and allocation of collateral (2 ) (19 ) — — (21 ) (2 ) (19 ) — — (21 ) Interest rate and foreign currency derivative assets subtotal 1 11 — — 12 1 27 — — 28 Other investments — — 42 — 42 — — 42 — 42 Total assets 5,237 2,859 1,509 3,113 12,718 5,674 2,937 1,529 3,113 13,253 Liabilities Commodity derivative liabilities Economic hedges (1,267 ) (2,378 ) (794 ) — (4,439 ) (1,267 ) (2,378 ) (1,052 ) — (4,697 ) Proprietary trading (3 ) (50 ) (26 ) — (79 ) (3 ) (50 ) (26 ) — (79 ) Effect of netting and allocation of collateral (f) 1,233 2,339 542 — 4,114 1,233 2,339 542 — 4,114 Commodity derivative liabilities subtotal (37 ) (89 ) (278 ) — (404 ) (37 ) (89 ) (536 ) — (662 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (10 ) — — (10 ) — (10 ) — — (10 ) Economic hedges — (21 ) — — (21 ) — (21 ) — — (21 ) Proprietary trading (4 ) — — — (4 ) (4 ) — — — (4 ) Effect of netting and allocation of collateral 4 19 — — 23 4 19 — — 23 Interest rate and foreign currency derivative liabilities subtotal — (12 ) — — (12 ) — (12 ) — — (12 ) Deferred compensation obligation — (34 ) — — (34 ) — (136 ) — (136 ) Total liabilities (37 ) (135 ) (278 ) — (450 ) (37 ) (237 ) (536 ) — (810 ) Total net assets $ 5,200 $ 2,724 $ 1,231 $ 3,113 $ 12,268 $ 5,637 $ 2,700 $ 993 $ 3,113 $ 12,443 Generation Exelon As of December 31, 2015 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 104 $ — $ — $ — $ 104 $ 5,766 $ — $ — $ — $ 5,766 NDT fund investments Cash equivalents (b) 219 92 — — 311 219 92 — — 311 Equities 3,008 — — 1,894 4,902 3,008 — — 1,894 4,902 Generation Exelon As of December 31, 2015 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Fixed income Corporate debt — 1,824 242 — 2,066 — 1,824 242 — 2,066 U.S. Treasury and agencies 1,323 15 — — 1,338 1,323 15 — — 1,338 Foreign governments — 61 — — 61 — 61 — — 61 State and municipal debt — 326 — — 326 — 326 — — 326 Other (c) — 147 — 390 537 — 147 — 390 537 Fixed income subtotal 1,323 2,373 242 390 4,328 1,323 2,373 242 390 4,328 Middle market lending — — 428 — 428 — — 428 — 428 Private equity — — — 125 125 — — — 125 125 Real estate — — — 35 35 — — — 35 35 Other — — — 216 216 — — — 216 216 Nuclear decommissioning trust fund investments subtotal (d) 4,550 2,465 670 2,660 10,345 4,550 2,465 670 2,660 10,345 Pledged assets for Zion Station decommissioning Cash equivalents — 17 — — 17 — 17 — — 17 Equities 1 5 — — 6 1 5 — — 6 Fixed income U.S. Treasury and agencies 6 2 — — 8 6 2 — — 8 Corporate debt — 46 — — 46 — 46 — — 46 Other — 1 — — 1 — 1 — — 1 Fixed income subtotal 6 49 — — 55 6 49 — — 55 Middle market lending — — 22 105 127 — — 22 105 127 Pledged assets for Zion Station decommissioning subtotal (e) 7 71 22 105 205 7 71 22 105 205 Rabbi trust investments Mutual funds 17 — — — 17 48 — — — 48 Life insurance contracts — 13 — — 13 — 36 — — 36 Rabbi trust investments subtotal 17 13 — — 30 48 36 — — 84 Commodity derivative assets Economic hedges 1,922 3,467 1,707 — 7,096 1,922 3,467 1,707 — 7,096 Proprietary trading 36 64 30 — 130 36 64 30 — 130 Effect of netting and allocation of collateral (f) (1,964 ) (2,629 ) (564 ) — (5,157 ) (1,964 ) (2,629 ) (564 ) — (5,157 ) Commodity derivative assets subtotal (6 ) 902 1,173 — 2,069 (6 ) 902 1,173 — 2,069 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 25 — — 25 Economic hedges — 20 — — 20 — 20 — — 20 Proprietary trading 10 5 — — 15 10 5 — — 15 Effect of netting and allocation of collateral (3 ) (3 ) — — (6 ) (3 ) (3 ) — — (6 ) Interest rate and foreign currency derivative assets subtotal 7 22 — — 29 7 47 — — 54 Other investments — — 33 — 33 — — 33 — 33 Total assets 4,679 3,473 1,898 2,765 12,815 10,372 3,521 1,898 2,765 18,556 Liabilities Commodity derivative liabilities Generation Exelon As of December 31, 2015 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Economic hedges (2,382 ) (3,348 ) (850 ) — (6,580 ) (2,382 ) (3,348 ) (1,097 ) — (6,827 ) Proprietary trading (33 ) (57 ) (37 ) — (127 ) (33 ) (57 ) (37 ) — (127 ) Effect of netting and allocation of collateral (f) 2,440 3,186 765 — 6,391 2,440 3,186 765 — 6,391 Commodity derivative liabilities subtotal 25 (219 ) (122 ) — (316 ) 25 (219 ) (369 ) — (563 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (16 ) — — (16 ) — (16 ) — — (16 ) Economic hedges — (3 ) — — (3 ) — (3 ) — — (3 ) Proprietary trading (12 ) — — — (12 ) (12 ) — — — (12 ) Effect of netting and allocation of collateral 12 3 — — 15 12 3 — — 15 Interest rate and foreign currency derivative liabilities subtotal — (16 ) — — (16 ) — (16 ) — — (16 ) Deferred compensation obligation — (30 ) — — (30 ) — (99 ) — — (99 ) Total liabilities 25 (265 ) (122 ) — (362 ) 25 (334 ) (369 ) — (678 ) Total net assets $ 4,704 $ 3,208 $ 1,776 $ 2,765 $ 12,453 $ 10,397 $ 3,187 $ 1,529 $ 2,765 $ 17,878 _________________________ (a) Generation excludes cash of $252 million and $329 million at December 31, 2016 and 2015 and restricted cash of $157 million and $121 million at December 31, 2016 and 2015 . Exelon excludes cash of $360 million and $763 million at December 31, 2016 and 2015 and restricted cash of $180 million and $178 million at December 31, 2016 and 2015 and includes long term restricted cash of $25 million at December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) Includes $29 million and $52 million of cash received from outstanding repurchase agreements at December 31, 2016 and 2015 , respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (d) below. (c) Includes derivative instruments of $(2) million and $(8) million , which have a total notional amount of $933 million and $1,236 million at December 31, 2016 and 2015 , respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the fiscal years ended and do not represent the amount of the company's exposure to credit or market loss. (d) Excludes net liabilities of $(31) million and $(3) million at December 31, 2016 and 2015 , respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, repurchase agreement obligations, and payables related to pending securities purchases. The repurchase agreements are generally short-term in nature with durations generally of 30 days or less. (e) Excludes net assets of less than $1 million and $1 million at December 31, 2016 and 2015 , respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (f) Collateral posted to/(received from) counterparties totaled $71 million , $197 million and $61 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2016 . Collateral posted to/(received from) counterparties totaled $476 million , $557 million and $201 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2015 . PHI, Pepco, DPL and ACE The following tables present assets and liabilities measured and recorded at fair value on PHI's, Pepco's, DPL's and ACE's Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of December 31, 2016 and December 31, 2015 : Successor Predecessor As of December 31, 2016 As of December 31, 2015 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 217 $ — $ — $ 217 $ 42 $ — $ — $ 42 Mark-to-market derivative assets (b)(c) 2 — — 2 — — 18 18 Effect of netting and allocation of collateral (2 ) — — (2 ) — — — — Mark-to-market derivative assets subtotal — — — — — — 18 18 Rabbi trust investments Cash equivalents 73 — — 73 12 — — 12 Fixed income — 16 — 16 — 15 — 15 Life insurance contracts — 22 20 42 — 27 19 46 Rabbi trust investments subtotal 73 38 20 131 12 42 19 73 Total assets 290 38 20 348 54 42 37 133 Liabilities Deferred compensation obligation — (28 ) — (28 ) — (30 ) — (30 ) Mark-to-market derivative liabilities (b) — — — — (2 ) — — (2 ) Effect of netting and allocation of collateral — — — — 2 — — 2 Mark-to-market derivative liabilities subtotal — — — — — — — — Total liabilities — (28 ) — (28 ) — (30 ) — (30 ) Total net assets $ 290 $ 10 $ 20 $ 320 $ 54 $ 12 $ 37 $ 103 Pepco DPL ACE As of December 31, 2016 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 33 $ — $ — $ 33 $ 42 $ — $ — $ 42 $ 130 $ — $ — $ 130 Mark-to-market derivative assets (b) — — — — 2 — — 2 — — — — Effect of netting and allocation of collateral — — — — (2 ) — — (2 ) — — — — Mark-to-market derivative assets subtotal — — — — — — — — — — — — Rabbi trust investments Cash equivalents 43 — — 43 — — — — — — — — Fixed income — 16 — 16 — — — — — — — — Life insurance contracts — 22 19 41 — — — — — — — — Rabbi trust investments subtotal 43 38 19 100 — — — — — — — — Total assets 76 38 19 133 42 — — 42 130 — — 130 Liabilities Deferred compensation obligation — (5 ) — (5 ) — (1 ) — (1 ) — — — — Total liabilities — (5 ) — (5 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 76 $ 33 $ 19 $ 128 $ 42 $ (1 ) $ — $ 41 $ 130 $ — $ — $ 130 Pepco DPL ACE As of December 31, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 2 $ — $ — $ 2 $ — $ — $ — $ — $ 30 $ — $ — $ 30 Rabbi trust investments Cash equivalents 11 — — 11 — — — — — — — — Fixed income — 15 — 15 — — — — — — — — Life insurance contracts — 23 19 42 — — — — — — — — Rabbi trust investments subtotal 11 38 19 68 — — — — — — — — Total assets 13 38 19 70 — — — — 30 — — 30 Liabilities Deferred compensation obligation — (6 ) — (6 ) — (1 ) — (1 ) — — — — Mark-to-market derivative liabilities (b) — — — — (2 ) — — (2 ) — — — — Effect of netting and allocation of collateral — — — — 2 — — 2 — — — — Mark-to-market derivative liabilities subtotal — — — — — — — — — — — — Total liabilities — (6 ) — (6 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 13 $ 32 $ 19 $ 64 $ — $ (1 ) $ — $ (1 ) $ 30 $ — $ — $ 30 _______ (a) PHI excludes cash of $19 million and $16 million at December 31, 2016 and 2015 and includes long term restricted cash of $23 million and $18 million at December 31, 2016 and 2015 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $9 million and $5 million at December 31, 2016 and 2015 . DPL excludes cash of $4 million and $5 million at December 31, 2016 and 2015 . ACE excludes cash of $3 million and $3 million at December 31, 2016 and 2015 and includes long term restricted cash of $23 million and $18 million at December 31, 2016 and 2015 which is reported in other deferred debits on the balance sheet. (b) Represents natural gas futures purchased by DPL as part of a natural gas hedging program approved by the DPSC. (c) Prior to the PHI Merger, PHI recorded derivative assets for the embedded call and redemption features on the shares of Preferred Stock outstanding as of December 31, 2015. See Note 19 - Mezzanine Equity for additional information. As a result of the PHI Merger, the PHI preferred stock derivative was reduced to zero as of March 23, 2016 .
Total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis	The following tables present the income statement classification of the total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis during the years ended December 31, 2016 and 2015 : Generation Exelon Operating Revenues Purchased Power and Fuel Other, net (a) Operating Revenues Purchased Power and Fuel Other, net (a) Total gains (losses) included in net income for the year ended December 31, 2016 $ (477 ) $ (91 ) $ 7 $ (477 ) $ (91 ) $ 10 Change in the unrealized gains (losses) relating to assets and liabilities held for the year ended December 31, 2016 $ 154 $ (45 ) $ 5 $ 154 $ (45 ) $ 7 Generation Exelon Operating Revenues Purchased Power and Fuel Other, net (a) Operating Revenues Purchased Power and Fuel Other, net (a) Total gains (losses) included in net income for the year ended December 31, 2015 $ 67 $ (45 ) $ 4 $ 67 $ (45 ) $ 4 Change in the unrealized gains (losses) relating to assets and liabilities held for the year ended December 31, 2015 $ 858 $ (2 ) $ 2 $ 858 $ (2 ) $ 2 Successor Predecessor PHI PHI Pepco March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 December 31, 2015 December 31, 2016 December 31, 2015 Other, net Other, net Other, net Total (losses) gains included in net income $ 3 $ (17 ) $ 20 $ 3 $ 5 Change in the unrealized gains (losses) relating to assets and liabilities held 2 1 18 3 3 ________________________ (a) Other, net activity consists of realized and unrealized gains (losses) included in income for the NDT funds held by Generation and the life insurance contracts held by Pepco.
Fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis, valuation technique	The table below discloses the significant inputs to the forward curve used to value these positions. Type of trade Fair Value at December 31, 2016 Valuation Technique Unobservable Input Range Mark-to-market derivatives—Economic hedges (Exelon and Generation) (a)(c) $ 435 Discounted Cash Flow Forward power price $11 - $130 Forward gas price $1.72 - $9.20 Option Model Volatility percentage 8% - 173% Mark-to-market derivatives—Proprietary trading (Exelon and Generation) (a)(c) $ (3 ) Discounted Cash Flow Forward power price $19 - $79 Mark-to-market derivatives (Exelon and ComEd) $ (258 ) Discounted Cash Flow Forward heat rate (b) 8x - 9x Marketability reserve 3% - 8% Renewable factor 89% - 121% _________________________ (a) The valuation techniques, unobservable inputs and ranges are the same for the asset and liability positions. (b) Quoted forward natural gas rates are utilized to project the forward power curve for the delivery of energy at specified future dates. The natural gas curve is extrapolated beyond its observable period to the end of the contract’s delivery. (c) The fair values do not include cash collateral posted on level three positions of $61 million as of December 31, 2016 . Type of trade Fair Value at December 31, 2015 Valuation Technique Unobservable Input Range Mark-to-market derivatives—Economic hedges (Exelon and Generation) (a)(c) $ 857 Discounted Cash Flow Forward power price $11 - $88 Forward gas price $1.18 - $8.95 Option Model Volatility percentage 5% - 152% Mark-to-market derivatives— Proprietary trading (Exelon and Generation) (a)(c) $ (7 ) Discounted Cash Flow Forward power price $13 - $78 Mark-to-market derivatives (Exelon and ComEd) $ (247 ) Discounted Cash Flow Forward heat rate (b) 9x - 10x Marketability reserve 3.5% - 7% Renewable factor 87% - 128% __________________________ (a) The valuation techniques, unobservable inputs and ranges are the same for the asset and liability positions. (b) Quoted forward natural gas rates are utilized to project the forward power curve for the delivery of energy at specified future dates. The natural gas curve is extrapolated beyond its observable period to the end of the contract’s delivery. (c) The fair values do not include cash collateral posted on level three positions of $201 million as of December 31, 2015

Derivative Financial Instrume50

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of the derivative fair value	Below is a summary of the interest rate and foreign exchange hedge balances as of December 31, 2016 : Generation Exelon Corporate Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary (a) Collateral and Netting (b) Subtotal Derivatives Total Mark-to-market derivative assets (current assets) $ — $ 17 $ 4 $ (13 ) $ 8 $ — $ 8 Mark-to-market derivative assets (noncurrent assets) — 11 1 (8 ) 4 16 20 Total mark-to-market derivative assets — 28 5 (21 ) 12 16 28 Mark-to-market derivative liabilities (current liabilities) (7 ) (13 ) (2 ) 14 (8 ) — (8 ) Mark-to-market derivative liabilities (noncurrent liabilities) (3 ) (8 ) (2 ) 9 (4 ) — (4 ) Total mark-to-market derivative liabilities (10 ) (21 ) (4 ) 23 (12 ) — (12 ) Total mark-to-market derivative net assets (liabilities) $ (10 ) $ 7 $ 1 $ 2 $ — $ 16 $ 16 _________________________ (a) Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts between the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates. (b) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures subject to a master netting or similar agreement, such as accrued interest, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. The following table provides a summary of the interest rate and foreign exchange hedge balances recorded by the Registrants as of December 31, 2015 : Generation Other Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary (a) Collateral and Netting (b) Subtotal Derivatives Subtotal Total Mark-to-market derivative assets (current assets) $ — $ 10 $ 10 $ (5 ) $ 15 $ — $ — $ 15 Mark-to-market derivative assets (noncurrent assets) — 10 5 (1 ) 14 25 $ 25 $ 39 Total mark-to-market derivative assets — 20 15 (6 ) 29 25 25 54 Mark-to-market derivative liabilities (current liabilities) (8 ) (2 ) (9 ) 11 (8 ) — — (8 ) Mark-to-market derivative liabilities (noncurrent liabilities) (8 ) (1 ) (3 ) 4 (8 ) — — (8 ) Total mark-to-market derivative liabilities (16 ) (3 ) (12 ) 15 (16 ) — — (16 ) Total mark-to-market derivative net assets (liabilities) $ (16 ) $ 17 $ 3 $ 9 $ 13 $ 25 $ 25 $ 38 _________________________ (a) Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts between the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates. (b) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures subject to a master netting or similar agreement, such as accrued interest, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. The following table provides a summary of the derivative fair value balances recorded by the Registrants as of December 31, 2016 : Successor Generation ComEd DPL PHI Exelon Derivatives Economic Hedges Proprietary Trading Collateral and Netting (a) Subtotal (b) Economic Hedges (c) Economic Hedges (d) Collateral and Netting (a) Subtotal Subtotal Total Derivatives Mark-to-market derivative assets (current assets) $ 3,623 $ 55 $ (2,769 ) $ 909 $ — $ 2 $ (2 ) $ — $ — $ 909 Mark-to-market derivative assets (noncurrent assets) 1,467 21 (1,016 ) 472 — — — — — 472 Total mark-to-market derivative assets 5,090 76 (3,785 ) 1,381 — 2 (2 ) — — 1,381 Mark-to-market derivative liabilities (current liabilities) (3,165 ) (54 ) 2,964 (255 ) (19 ) — — — — (274 ) Mark-to-market derivative liabilities (noncurrent liabilities) (1,274 ) (25 ) 1,150 (149 ) (239 ) — — — — (388 ) Total mark-to-market derivative liabilities (4,439 ) (79 ) 4,114 (404 ) (258 ) — — — — (662 ) Total mark-to-market derivative net assets (liabilities) $ 651 $ (3 ) $ 329 $ 977 $ (258 ) $ 2 $ (2 ) $ — $ — $ 719 ______________________ (a) Exelon, Generation, PHI and DPL net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. (b) Current and noncurrent assets are shown net of collateral of $100 million and $72 million , respectively, and current and noncurrent liabilities are shown net of collateral of $95 million and $62 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $329 million at December 31, 2016 . (c) Includes current and noncurrent liabilities relating to floating-to-fixed energy swap contracts with unaffiliated suppliers. (d) Represents natural gas futures purchased by DPL as part of a natural gas hedging program approved by the DPSC. The following table provides a summary of the derivative fair value balances recorded by the Registrants as of December 31, 2015 : Predecessor Generation ComEd Exelon DPL PHI Corporate PHI Derivatives Economic Hedges Proprietary Trading Collateral and Netting (a) Subtotal (b) Economic Hedges (c) Total Economic Hedges (e) Collateral and Netting (a) Subtotal Other (d) Total Mark-to-market derivative assets (current assets) $ 5,236 $ 108 $ (3,994 ) $ 1,350 $ — $ 1,350 $ — $ — $ — $ 18 $ 18 Mark-to-market derivative assets (noncurrent assets) 1,860 22 (1,163 ) 719 — 719 — — — — — Total mark-to-market derivative assets 7,096 130 (5,157 ) 2,069 — 2,069 — — — 18 18 Mark-to-market derivative liabilities (current liabilities) (4,907 ) (94 ) 4,827 (174 ) (23 ) (197 ) (2 ) 2 — — — Mark-to-market derivative liabilities (noncurrent liabilities) (1,673 ) (33 ) 1,564 (142 ) (224 ) (366 ) — — — — — Total mark-to-market derivative liabilities (6,580 ) (127 ) 6,391 (316 ) (247 ) (563 ) (2 ) 2 — — — Total mark-to-market derivative net assets (liabilities) $ 516 $ 3 $ 1,234 $ 1,753 $ (247 ) $ 1,506 $ (2 ) $ 2 $ — $ 18 $ 18 ______________________ (a) Exelon, Generation, PHI and DPL net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, and letters of credit and other forms of non-cash collateral. These are not reflected in the table above. (b) Current and noncurrent assets are shown net of collateral of $352 million and $180 million , respectively, and current and noncurrent liabilities are shown net of collateral of $480 million and $222 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,234 million at December 31, 2015 . (c) Includes current and noncurrent liabilities relating to floating-to-fixed energy swap contracts with unaffiliated suppliers. (d) Prior to the PHI Merger, PHI recorded derivative assets for the embedded call and redemption features on the shares of Preferred Stock outstanding as of December 31, 2015. See Note 19 - Mezzanine Equity for additional information. As a result of the PHI Merger, the PHI preferred stock derivative was reduced to zero as of March 23, 2016 . (e) Represents natural gas futures purchased by DPL as part of a natural gas hedging program approved by the DPSC.
Gain or loss on the hedged items and the offsetting loss or gain on the related interest rate swaps in interest expense	Exelon includes the gain or loss on the hedged items and the offsetting loss or gain on the related interest rate swaps in interest expense as follows: Year Ended December 31, Income Statement Location 2016 2015 2014 2016 2015 2014 Gain (Loss) on Swaps Gain (Loss) on Borrowings Generation Interest expense (a) $ — $ (1 ) $ (16 ) $ — $ — $ 2 Exelon Interest expense $ (9 ) $ 3 $ 14 $ 23 $ 14 $ (1 ) ______________________ (a) For the years ended December 31, 2015 and 2014 , the loss on Generation swaps included $(1) million and $(17) million realized in earnings, respectively, with an immaterial amount and $4 million excluded from hedge effectiveness testing, respectively.
The activity of accumulated OCI related to cash flow hedges	The tables below provide the activity of OCI related to cash flow hedges for the years ended December 31, 2016 and 2015 , containing information about the changes in the fair value of cash flow hedges and the reclassification from Accumulated OCI into results of operations. The amounts reclassified from OCI, when combined with the impacts of the hedged transactions, result in the ultimate recognition of net revenues or expenses at the contractual price. Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon For the Year Ended December 31, 2016 Income Statement Location Total Cash Total Cash Flow Hedges AOCI derivative loss at December 31, 2015 $ (21 ) $ (19 ) Effective portion of changes in fair value (6 ) (6 ) Reclassifications from AOCI to net income Interest expense 8 (a) 8 (a) AOCI derivative loss at December 31, 2016 $ (19 ) $ (17 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon For the Year Ended December 31, 2015 Income Statement Location Total Cash Total Cash Flow Hedges Accumulated OCI derivative loss at December 31, 2014 $ (18 ) $ (28 ) Effective portion of changes in fair value (8 ) (12 ) Reclassifications from AOCI to net income Other, net — 16 (b) Reclassifications from AOCI to net income Interest Expense 7 (c) 7 (c) Reclassifications from AOCI to net income Operating Revenues (2 ) (2 ) Accumulated OCI derivative loss at December 31, 2015 $ (21 ) $ (19 ) _______________________ (a) Amount is net of related income tax expense of $5 million for the year ended December 31, 2016 . (b) Amount is net of related income tax expense of $10 million for the year ended December 31, 2015 . (c) Amount is net of related income tax expense of $4 million for the year ended December 31, 2015 ,
Change in fair value and reclassification of derivative contracts	In the tables below, “Change in fair value” represents the change in fair value of the derivative contracts held at the reporting date. The “Reclassification to realized at settlement” represents the recognized change in fair value that was reclassified to realized due to settlement of the derivative during the period. For the Years Ended December 31, 2016 2015 2014 Change in fair value of commodity positions $ 23 $ 8 $ (1 ) Reclassification to realized at settlement of commodity positions (21 ) (14 ) (29 ) Net commodity mark-to-market gains (losses) 2 (6 ) (30 ) Change in fair value of treasury positions (1 ) 8 1 Reclassification to realized at settlement of treasury positions — (10 ) 3 Net treasury mark-to market gains (losses) (1 ) (2 ) 4 Net mark-to market gains (losses) $ 1 $ (8 ) $ (26 ) In the tables below, “Change in fair value” represents the change in fair value of the derivative contracts held at the reporting date. The “Reclassification to realized at settlement” represents the recognized change in fair value that was reclassified to realized due to settlement of the derivative during the period. Generation Exelon Year Ended December 31, 2016 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ 5 $ 208 $ 213 $ 213 Reclassification to realized at settlement of commodity positions (495 ) 251 (244 ) (244 ) Net commodity mark-to-market gains (losses) (490 ) 459 (31 ) (31 ) Change in fair value of treasury positions (2 ) — (2 ) (2 ) Reclassification to realized at settlement of treasury positions (8 ) — (8 ) (8 ) Net treasury mark-to-market gains (losses) (10 ) — (10 ) (10 ) Net mark-to-market gains (losses) $ (500 ) $ 459 $ (41 ) $ (41 ) Generation Exelon Corporate Exelon Year Ended December 31, 2015 Operating Revenues Purchased Power and Fuel Total Interest Expense Total Change in fair value of commodity positions $ 759 $ (355 ) $ 404 $ — $ 404 Reclassification to realized at settlement of commodity positions (563 ) 409 (154 ) — (154 ) Net commodity mark-to-market gains (losses) 196 54 250 — 250 Change in fair value of treasury positions 13 — 13 36 49 Reclassification to realized at settlement of treasury positions (6 ) — (6 ) 64 58 Net treasury mark-to-market gains (losses) 7 — 7 100 107 Net mark-to-market gains (losses) $ 203 $ 54 $ 257 $ 100 $ 357 Generation Exelon Corporate Exelon Year Ended December 31, 2014 Operating Purchased Interest Expense Total Interest Expense Total Change in fair value of commodity positions $ (413 ) $ (194 ) $ — $ (607 ) $ — $ (607 ) Reclassification to realized at settlement of commodity positions 231 (223 ) — 8 — 8 Net commodity mark-to-market gains (losses) (182 ) (417 ) — (599 ) — (599 ) Change in fair value of treasury positions 10 — (2 ) 8 (100 ) (92 ) Reclassification to realized at settlement of treasury positions (2 ) — — (2 ) — (2 ) Net treasury mark-to-market gains (losses) 8 — (2 ) 6 (100 ) (94 ) Net mark-to-market gains (losses) $ (174 ) $ (417 ) $ (2 ) $ (593 ) $ (100 ) $ (693 )
Information on Generation's credit exposure for all derivative instruments, normal purchase normal sales, and applicable payables and receivables, net of collateral and instruments that are subject to master netting agreements	The aggregate fair value of all derivative instruments with credit-risk-related contingent features in a liability position that are not fully collateralized (excluding transactions on the exchanges that are fully collateralized) is detailed in the table below: For the Years Ended December 31, Credit-Risk Related Contingent Feature 2016 2015 Gross Fair Value of Derivative Contracts Containing this Feature (a) $ (960 ) $ (932 ) Offsetting Fair Value of In-the-Money Contracts Under Master Netting Arrangements (b) 627 684 Net Fair Value of Derivative Contracts Containing This Feature (c) $ (333 ) $ (248 ) __________________________ (a) Amount represents the gross fair value of out-of-the-money derivative contracts containing credit-risk-related contingent features ignoring the effects of master netting agreements. (b) Amount represents the offsetting fair value of in-the-money derivative contracts under legally enforceable master netting agreements with the same counterparty, which reduces the amount of any liability for which a Registrant could potentially be required to post collateral. (c) Amount represents the net fair value of out-of-the-money derivative contracts containing credit-risk related contingent features after considering the mitigating effects of offsetting positions under master netting arrangements and reflects the actual net liability upon which any potential contingent collateral obligations would be based. The figures in the tables below exclude credit risk exposure from individual retail counterparties, Nuclear fuel procurement contracts and exposure through RTOs, ISOs, NYMEX, ICE and Nodal commodity exchanges. Additionally, the figures in the tables below exclude exposures with affiliates, including net receivables with ComEd, PECO, BGE, Pepco, DPL and ACE of $14 million , $33 million $26 million , $44 million , $16 million and $9 million as of December 31, 2016 , respectively. Rating as of December 31, 2016 Total Exposure Before Credit Collateral Credit Collateral (a) Net Exposure Number of Counterparties Greater than 10% of Net Exposure Net Exposure of Counterparties Greater than 10% of Net Exposure Investment grade $ 995 $ — $ 995 1 $ 328 Non-investment grade 118 16 102 — — No external ratings Internally rated — investment grade 352 1 351 — — Internally rated — non-investment grade 72 8 64 — — Total $ 1,537 $ 25 $ 1,512 1 $ 328 Net Credit Exposure by Type of Counterparty December 31, 2016 Financial institutions $ 116 Investor-owned utilities, marketers, power producers 689 Energy cooperatives and municipalities 636 Other 71 Total $ 1,512 ______________________ (a) As of December 31, 2016 , credit collateral held from counterparties where Generation had credit exposure included $9 million of cash and $16 million of letters of credit.

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Schedule of Short-term Debt	The following tables present the short-term borrowings activity for Exelon, Generation, ComEd, BGE, PHI, Pepco, DPL and ACE during 2016 , 2015 and 2014 . PECO did not have any short-term borrowings during 2016 , 2015 or 2014 . Exelon 2016 2015 2014 Average borrowings $ 1,125 $ 499 $ 571 Maximum borrowings outstanding 3,076 739 1,164 Average interest rates, computed on a daily basis 0.88 % 0.53 % 0.32 % Average interest rates, at December 31 1.12 % 0.88 % 0.53 % Generation 2016 2015 2014 Average borrowings $ 536 $ 1 $ 93 Maximum borrowings outstanding 1,735 50 552 Average interest rates, computed on a daily basis 0.94 % 0.49 % 0.32 % Average interest rates, at December 31 1.14 % n.a. n.a. ComEd 2016 2015 2014 Average borrowings $ 256 $ 461 $ 415 Maximum borrowings outstanding 755 684 597 Average interest rates, computed on a daily basis 0.77 % 0.53 % 0.33 % Average interest rates, at December 31 n.a. 0.89 % 0.50 % BGE 2016 2015 2014 Average borrowings $ 143 $ 37 $ 64 Maximum borrowings outstanding 369 210 180 Average interest rates, computed on a daily basis 0.77 % 0.48 % 0.29 % Average interest rates, computed at December 31 0.95 % 0.87 % 0.61 % PHI Successor Predecessor 2016 2015 2014 Average borrowings $ 153 $ 444 $ 153 Maximum borrowings outstanding 559 784 369 Average interest rates, computed on a daily basis 1.03 % 0.90 % 0.56 % Average interest rates, computed at December 31 n.a. 1.22 % 0.78 % Pepco 2016 2015 2014 Average borrowings $ 4 $ 34 $ 37 Maximum borrowings outstanding 73 190 209 Average interest rates, computed on a daily basis 0.71 % 0.44 % 0.28 % Average interest rates, computed at December 31 0.90 % 0.68 % 0.46 % DPL 2016 2015 2014 Average borrowings $ 33 $ 81 $ 69 Maximum borrowings outstanding 116 179 177 Average interest rates, computed on a daily basis 0.68 % 0.47 % 0.26 % Average interest rates, computed at December 31 n.a. 0.79 % 0.42 % ACE 2016 2015 2014 Average borrowings $ — $ 175 $ 112 Maximum borrowings outstanding 5 253 259 Average interest rates, computed on a daily basis 0.65 % 0.46 % 0.27 % Average interest rates, computed at December 31 n.a. 0.65 % 0.52 % December 31, 2016 and December 31, 2015 : Maximum Program Size at December 31, Outstanding Commercial Paper at December 31, Average Interest Rate on Commercial Paper Borrowings for the Year Ended December 31, Commercial Paper Issuer 2016 (a)(b) 2015 (a)(b) 2016 2015 2016 2015 Exelon Corporate $ 600 $ 500 $ — $ — 0.70 % n.a. Generation 5,300 5,450 620 — 0.94 % 0.49 % ComEd 1,000 1,000 — 294 0.77 % 0.53 % PECO 600 600 — — n.a n.a. BGE 600 600 45 210 0.77 % 0.48 % PHI Corporate — 875 — 484 1.03 % 0.80 % Pepco 500 500 23 64 0.71 % 0.44 % DPL 500 500 — 105 0.68 % 0.47 % ACE 350 350 — 5 0.65 % 0.46 % Total $ 9,450 $ 10,375 $ 688 $ 1,162 _____________________ (a) Excludes $500 million and $275 million in bilateral credit facilities that do not back Generation's commercial paper program at December 31, 2016 and 2015 , respectively. (b) Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million , $34 million , $34 million , $5 million , $2 million , $2 million and $2 million , respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016 , letters of credit issued under these facilities totaled $7 million , $12 million , $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.
Schedule of Line of Credit Facilities	The adders for the prime based borrowings and LIBOR-based borrowings are presented in the following table: Exelon Generation ComEd PECO BGE Pepco DPL ACE Prime based borrowings 27.5 27.5 7.5 0.0 0.0 7.5 7.5 7.5 LIBOR-based borrowings 127.5 127.5 107.5 90.0 100.0 107.5 107.5 107.5 At December 31, 2016 , the Registrants had the following aggregate bank commitments, credit facility borrowings and available capacity under their respective credit facilities: Available Capacity at December 31, 2016 Borrower Facility Type Aggregate Bank (a)(b) Facility Draws Outstanding Letters of Credit (c) Actual To Support Additional Commercial (d) Exelon Corporate Syndicated Revolver $ 600 $ — $ 29 $ 571 $ 571 Generation Syndicated Revolver 5,300 — 1,170 4,130 3,510 Generation Bilaterals 500 75 306 119 — ComEd Syndicated Revolver 1,000 — 2 998 998 PECO Syndicated Revolver 600 — 2 598 598 BGE Syndicated Revolver 600 — — 600 555 Pepco Syndicated Revolver 300 — — 300 277 DPL Syndicated Revolver 300 — — 300 300 ACE Syndicated Revolver 300 — 1 299 299 Total $ 9,500 $ 75 $ 1,510 $ 7,915 $ 7,108 _______________________ (a) Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million , $34 million , $34 million , $5 million , $2 million , $2 million and $2 million , respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016 , letters of credit issued under these facilities totaled $7 million , $12 million , $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively. (b) Pepco, DPL and ACE's revolving credit facility is subject to available borrowing capacity. The borrowing capacity may be increased or decreased during the term of the facility, except that (i) the sum of the borrowing capacity must equal the total amount of the facility, and (ii) the aggregate amount of credit used at any given time by each of Pepco, DPL or ACE may not exceed $900 million or the maximum amount of short-term debt the company is permitted to have outstanding by its regulatory authorities. The total number of the borrowing reallocations may not exceed eight per year during the term of the facility. (c) Excludes nonrecourse debt letters of credit, see discussion below on Continental Wind. (d) Excludes $500 million in bilateral credit facilities that do not back Generation’s commercial paper program.
Schedule Of Credit Agreement Covenants	The following table summarizes the minimum thresholds reflected in the credit agreements for the year ended December 31, 2016 : Exelon Generation ComEd PECO BGE Pepco DPL ACE Credit agreement threshold 2.50 to 1 3.00 to 1 2.00 to 1 2.00 to 1 2.00 to 1 2.00 to 1 2.00 to 1 2.00 to 1 At December 31, 2016 , the interest coverage ratios at the Registrants were as follows: Exelon Generation ComEd PECO BGE Pepco DPL ACE Interest coverage ratio 7.03 11.81 6.89 8.77 10.47 6.24 8.42 5.84
Schedule of Long-term Debt Instruments	ACE Maturity December 31, Rates 2016 2015 Long-term debt First mortgage bonds (a) 3.38 % - 7.75 % 2018 - 2036 $ 1,038 $ 1,039 Transition bonds (b) 5.05 % - 5.55 % 2020 - 2023 124 171 Total long-term debt 1,162 1,210 Unamortized debt discount and premium, net (1 ) (1 ) Unamortized debt issuance costs (6 ) (8 ) Long-term debt due within one year (35 ) (48 ) Long-term debt $ 1,120 $ 1,153 ___________________ (a) Substantially all of ACE's assets are subject to the lien of its respective mortgage indenture. (b) Maturities of ACE's Transition Bonds outstanding at December 31, 2016 are $35 million in 2017, $31 million in 2018, $18 million in 2019, $19 million in 2020 and $21 million in 2021. PECO Maturity Date December 31, Rates 2016 2015 Long-term debt First mortgage bonds (a) 1.70 % - 5.95 % 2018 - 2044 $ 2,600 $ 2,600 Total long-term debt 2,600 2,600 Unamortized debt discount and premium, net (5 ) (5 ) Unamortized debt issuance costs (15 ) (15 ) Long-term debt due within one year — (300 ) Long-term debt $ 2,580 $ 2,280 Long-term debt to financing trusts (b) Subordinated debentures to PECO Trust III 7.38 % 2028 $ 81 $ 81 Subordinated debentures to PECO Trust IV 5.75 % 2033 103 103 Long-term debt to financing trusts $ 184 $ 184 _____________________ (a) Substantially all of PECO’s assets are subject to the lien of its mortgage indenture. (b) Amounts owed to this financing trust are recorded as Long-term debt to financing trusts within PECO’s Consolidated Balance Sheets. ComEd Maturity Date December 31, Rates 2016 2015 Long-term debt First mortgage bonds (a) 2.15 % - 6.45 % 2017 - 2046 $ 6,954 $ 6,419 Notes payable and other (b) 6.95 % - 7.49 % 2018 - 2053 147 148 Total long-term debt 7,101 6,567 Unamortized debt discount and premium, net (22 ) (20 ) Unamortized debt issuance costs (46 ) (38 ) Long-term debt due within one year (425 ) (665 ) Long-term debt $ 6,608 $ 5,844 Long-term debt to financing trust (c) Subordinated debentures to ComEd Financing III 6.35 % 2033 $ 206 $ 206 Total long-term debt to financing trusts 206 206 Unamortized debt issuance costs (1 ) (1 ) Long-term debt to financing trusts $ 205 $ 205 ______________________ (a) Substantially all of ComEd’s assets other than expressly excepted property are subject to the lien of its mortgage indenture. (b) Includes ComEd’s capital lease obligations of $8 million at both December 31, 2016 and 2015 , respectively. Lease payments of less than $1 million will be made from 2017 through expiration at 2053. (c) Amount owed to this financing trust is recorded as Long-term debt to financing trust within ComEd’s Consolidated Balance Sheets. BGE Maturity Date December 31, Rates 2016 2015 Long-term debt Rate stabilization bonds 5.82 % - 5.82 % 2017 $ 41 $ 120 Senior unsecured notes 2.40 % - 6.35 % 2021 - 2046 2,300 1,750 Total long-term debt 2,341 1,870 Unamortized debt discount and premium, net (4 ) (3 ) Unamortized debt issuance costs (15 ) (9 ) Long-term debt due within one year (41 ) (378 ) Long-term debt $ 2,281 $ 1,480 Long-term debt to financing trusts (a) Subordinated debentures to BGE Capital Trust II 6.20 % 2043 $ 258 $ 258 Total long-term debt to financing trusts 258 258 Unamortized debt issuance costs (6 ) (6 ) Long-term debt to financing trusts $ 252 $ 252 ___________________ (a) Amount owed to this financing trust is recorded as Long-term debt to financing trust within BGE’s Consolidated Balance Sheets. DPL Maturity December 31, Rates 2016 2015 Long-term debt First mortgage bonds (a) 3.50 % - 4.15 % 2023 - 2045 $ 1,196 $ 1,121 Unsecured Tax-Exempt Bonds 5.40 % 2031 112 112 Medium-Terms Notes (unsecured) 6.81 % - 7.72 % 2017 - 2027 40 40 Total long-term debt 1,348 1,273 Unamortized debt discount and premium, net 2 2 Unamortized debt issuance costs (10 ) (10 ) Long-term debt due within one year (119 ) (204 ) Long-term debt $ 1,221 $ 1,061 Generation Maturity Date December 31, Rates 2016 2015 Long-term debt Senior unsecured notes 2.00 % - 7.60 % 2017 - 2042 $ 5,971 $ 5,971 Pollution control notes 2.50 % - 2.70 % 2025 - 2036 435 435 Nuclear fuel procurement contracts 3.15 % - 3.35 % 2018 - 2020 105 127 Notes payable and other (a)(b) 1.43 % - 7.83 % 2017 - 2035 382 166 Nonrecourse debt: Fixed rates 2.29 % - 6.00 % 2031 - 2037 1,400 1,162 Variable rates 3.18 % - 5.00 % 2019 - 2021 915 1,058 Total long-term debt 9,208 8,919 Fair value adjustment 115 127 Unamortized debt discount and premium, net (17 ) (17 ) Unamortized debt issuance costs (65 ) (70 ) Long-term debt due within one year (1,117 ) (90 ) Long-term debt $ 8,124 $ 8,869 ______________________ (a) Includes Generation’s capital lease obligations of $22 million and $21 million at December 31, 2016 and 2015 , respectively. Generation will make lease payments of $5 million , $5 million , $6 million and $5 million and $1 million in 2017 , 2018 , 2019 , 2020 and 2021 respectively. PHI Successor Predecessor Maturity December 31, Rates 2016 2015 Long-term debt Notes (unsecured) 6.13 % - 7.45 % 2017 - 2032 $ 266 $ 456 First mortgage bonds 3.05 % - 7.90 % 2018 - 2045 4,569 4,495 Unsecured Tax-Exempt Bonds 5.40 % 2031 112 112 Medium-Terms Notes (unsecured) 6.81 % - 7.72 % 2017 - 2027 40 40 Transition bonds (a) 5.05 % - 5.55 % 2020 - 2023 124 171 Notes payable and other (b) 6.20 % - 8.88 % 2019 - 2021 46 57 Total long-term debt 5,157 5,331 Unamortized debt discount and premium, net 1 (2 ) Unamortized debt issuance costs (2 ) (50 ) Fair value adjustment 742 — Long-term debt due within one year (253 ) (456 ) Long-term debt $ 5,645 $ 4,823 ________________ (a) Transition bonds are recorded as part of Long-term debt within ACE's Consolidated Balance Sheets. Pepco Maturity December 31, Rates 2016 2015 Long-term debt First mortgage bonds (a) 3.05 % - 7.90 % 2022 - 2043 $ 2,335 $ 2,335 Notes payable and other (b) 6.20 % - 8.88 % 2019 - 2021 46 50 Total long-term debt 2,381 2,385 Unamortized debt discount and premium, net (2 ) (3 ) Unamortized debt issuance costs (30 ) (31 ) Long-term debt due within one year (16 ) (11 ) Long-term debt $ 2,333 $ 2,340 The following tables present the outstanding long-term debt at the Registrants as of December 31, 2016 and 2015 : Exelon Maturity Date December 31, Rates 2016 2015 Long-term debt Rate stabilization bonds 5.82 % - 5.82 % 2017 $ 41 $ 120 First mortgage bonds (a) 1.70 % - 7.90 % 2017 - 2046 14,123 9,019 Senior unsecured notes 1.55 % - 7.60 % 2017 - 2046 11,868 9,803 Unsecured bonds 2.40 % - 6.35 % 2021 - 2046 2,300 1,750 Pollution control notes 2.50 % - 2.70 % 2025 - 2036 435 435 Nuclear fuel procurement contracts 3.15 % - 3.35 % 2018 - 2020 105 127 Notes payable and other (b)(c) 1.43 % - 7.83 % 2017 - 2053 576 314 Junior subordinated notes 6.50 % 2024 1,150 1,150 Contract payment - junior subordinated notes 2.50 % 2017 19 64 Long-term software licensing agreement 3.95 % 2024 103 111 Unsecured Tax-Exempt Bonds 5.40 % — 2031 112 — Medium-Terms Notes (unsecured) 6.81 % - 7.72 % — 2017 - 2027 40 — Transition bonds 5.05 % - 5.55 % — 2020 - 2023 124 — Nonrecourse debt: Fixed rates 2.29 % - 6.00 % 2031 - 2037 1,400 1,162 Variable rates 3.18 % - 5.00 % 2019 - 2021 915 1,058 Total long-term debt 33,311 25,113 Unamortized debt discount and premium, net (68 ) (63 ) Unamortized debt issuance costs (200 ) (180 ) Fair value adjustment 962 275 Long-term debt due within one year (2,430 ) (1,500 ) Long-term debt $ 31,575 $ 23,645 Long-term debt to financing trusts (d) Subordinated debentures to ComEd Financing III 6.35 % 2033 $ 206 $ 206 Subordinated debentures to PECO Trust III 7.38 % 2028 81 81 Subordinated debentures to PECO Trust IV 5.75 % 2033 103 103 Subordinated debentures to BGE Capital Trust II 6.20 % 2043 258 258 Total long-term debt to financing trusts 648 648 Unamortized debt issuance costs (7 ) (7 ) Long-term debt to financing trusts $ 641 $ 641 ____________________ (a) Substantially all of ComEd’s assets other than expressly excepted property and substantially all of PECO’s, Pepco's, DPL's and ACE's assets are subject to the liens of their respective mortgage indentures. (b) Includes capital lease obligations of $69 million and $29 million at December 31, 2016 and 2015 , respectively. Lease payments of $17 million , $18 million , $20 million , $5 million , $1 million , and $8 million will be made in 2017 , 2018 , 2019 , 2020 , 2021 and thereafter, respectively. (c) Includes financing related to Albany Green Energy, LLC (AGE), which is a consolidated variable interest entity (see Note 2 - Variable Interest Entities for additional information). The agreement is scheduled to expire on November 17, 2017, at a variable rate equal to LIBOR plus 1.25%. As of December 31, 2016, $198 million was outstanding. (d) Amounts owed to these financing trusts are recorded as Long-term debt to financing trusts within Exelon’s Consolidated Balance Sheets.
Schedule of Maturities of Long-term Debt	Long-term debt maturities at Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE in the periods 2017 through 2021 and thereafter are as follows: Year Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE 2017 $ 2,430 $ 1,117 $ 425 $ — $ 41 253 16 119 35 2018 1,742 104 840 500 — 298 13 4 281 2019 1,060 606 300 — — 154 124 12 18 2020 3,331 1,912 500 — — 19 — — 19 2021 2,400 888 350 300 300 262 2 — 260 Thereafter 22,996 (a) 4,581 4,892 (b) 1,984 (c) 2,258 (d) 4,171 2,226 1,213 549 Total $ 33,959 $ 9,208 $ 7,307 $ 2,784 $ 2,599 $ 5,157 $ 2,381 $ 1,348 $ 1,162 ____________________ (a) Includes $648 million due to ComEd, PECO and BGE financing trusts. (b) Includes $206 million due to ComEd financing trust. (c) Includes $184 million due to PECO financing trusts. (d) Includes $258 million due to BGE financing trust.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	Income tax expense (benefit) from continuing operations is comprised of the following components: Successor Predecessor For the Year Ended December 31, 2016 March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Included in operations: Federal Current $ 60 $ 513 $ (135 ) $ 63 $ 51 $ (118 ) $ (88 ) $ (26 ) $ (281 ) $ — Deferred 607 (247 ) 379 72 88 136 97 22 283 10 Investment tax credit amortization (24 ) (20 ) (2 ) — (1 ) — — — (1 ) — State Current 39 45 (4 ) 9 5 7 1 — (11 ) — Deferred 79 (1 ) 63 5 31 16 12 — 13 7 Total $ 761 $ 290 $ 301 $ 149 $ 174 $ 41 $ 22 $ (4 ) $ 3 $ 17 For the Year Ended December 31, 2015 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Included in operations: Federal Current $ 407 $ 546 $ (80 ) $ 64 $ 25 $ (54 ) $ (27 ) $ (2 ) $ 12 Deferred 566 16 310 69 126 126 73 27 103 Investment tax credit amortization (22 ) (19 ) (2 ) — (1 ) — — — (1 ) State Current (86 ) (90 ) 7 (10 ) — 6 2 3 17 Deferred 208 49 45 20 39 24 1 5 32 Total $ 1,073 $ 502 $ 280 $ 143 $ 189 $ 102 $ 49 $ 33 $ 163 For the Year Ended December 31, 2014 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Included in operations: Federal Current $ 121 $ 360 $ (171 ) $ 28 $ 24 $ (79 ) $ (45 ) $ (6 ) $ (153 ) Deferred 576 (35 ) 395 87 90 150 98 31 261 Investment tax credit amortization (20 ) (16 ) (2 ) — (1 ) — (1 ) (1 ) (1 ) State Current 42 35 7 (2 ) — (2 ) — (1 ) (10 ) Deferred (53 ) (137 ) 39 1 27 24 13 7 41 Total $ 666 $ 207 $ 268 $ 114 $ 140 $ 93 $ 65 $ 30 $ 138 following tables represent the net interest and penalties receivable (payable), including interest and penalties related to tax positions reflected in the Registrants’ Consolidated Balance Sheets. Net interest receivable (payable) as of Exelon Generation ComEd PECO BGE Pepco DPL ACE December 31, 2016 $ (507 ) $ 46 $ (384 ) $ 8 $ (1 ) $ 1 $ — $ 1 December 31, 2015 (288 ) 80 (210 ) 3 (1 ) 20 3 24 Net penalties receivable (payable) as of Exelon Generation ComEd PECO BGE Pepco DPL ACE December 31, 2016 $ (106 ) $ — $ (86 ) $ — $ — $ — $ — $ — December 31, 2015 — — — — — — — — Successor Predecessor PHI December 31, 2016 December 31, 2015 Net interest receivable (payable) $ 2 $ (34 ) Net penalties receivable (payable) — — Th
Effective Income Tax Rate Reconciliation	The effective income tax rate from continuing operations varies from the U.S. Federal statutory rate principally due to the following: Successor Predecessor For the Year Ended December 31, 2016 March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL (a) ACE (a) PHI (a) PHI U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit (b) 3.3 3.3 5.6 1.3 5.0 15.7 52.7 6.2 5.8 11.9 Qualified nuclear decommissioning trust fund loss 3.4 7.8 — — — — — — — — Domestic production activities deduction — — — — — — — — — — Health care reform legislation — — — — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.2 ) (2.3 ) (0.3 ) (0.1 ) (0.1 ) (0.2 ) (3.7 ) 0.8 1.4 (0.9 ) Plant basis differences (4.8 ) — (0.6 ) (9.6 ) (2.7 ) (22.8 ) (25.5 ) 10.3 39.0 (13.5 ) Production tax credits and other credits (3.6 ) (8.2 ) — — — — — — — — Noncontrolling interests (0.2 ) (0.3 ) — — — — — — — — Statute of limitations expiration (0.4 ) (1.7 ) — — — — — — — — Penalties 1.9 — 4.5 — — — — — (0.7 ) — Merger Expenses 5.5 1.1 — — — 23.5 112.9 (44.9 ) (89.0 ) 11.1 Other (c) (0.6 ) (1.5 ) 0.1 (1.2 ) — (1.8 ) (2.2 ) 1.3 3.3 3.6 Effective income tax rate 38.3 % 33.2 % 44.3 % 25.4 % 37.2 % 49.4 % 169.2 % 8.7 % (5.2 )% 47.2 % For the Year Ended December 31, 2015 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 3.7 1.0 4.9 1.0 5.3 6.7 1.7 5.7 6.6 Qualified nuclear decommissioning trust fund income (0.4 ) (0.8 ) — — — — — — — Domestic production activities deduction (0.7 ) (1.3 ) — — — — — — — Health care reform legislation — — — — 0.1 — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.9 ) (1.5 ) (0.3 ) (0.1 ) (0.1 ) (0.1 ) (0.4 ) (0.6 ) (0.2 ) Plant basis differences (1.5 ) — (0.1 ) (8.7 ) (0.7 ) (5.8 ) (2.3 ) (1.3 ) (4.3 ) Production tax credits and other credits (1.9 ) (3.4 ) — — — — — — — Noncontrolling interests 0.3 0.5 — — — — — — — Statute of limitations expiration (1.4 ) (2.4 ) — — — — — — — Other (d) — — 0.2 0.2 — (0.5 ) 5.2 6.4 (3.2 ) Effective income tax rate 32.2 % 27.1 % 39.7 % 27.4 % 39.6 % 35.3 % 39.2 % 45.2 % 33.9 % For the Year Ended December 31, 2014 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 1.3 (1.9 ) 4.5 (0.1 ) 5.0 5.4 4.8 5.8 5.3 Qualified nuclear decommissioning trust fund income 2.4 4.8 — — — — — — — Domestic production activities deduction (2.0 ) (4.1 ) — — — — — — — Health care reform legislation 0.1 — 0.2 — 0.2 — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.1 ) (2.0 ) (0.3 ) (0.1 ) (0.3 ) (0.1 ) (0.3 ) (0.6 ) (0.3 ) Plant basis differences (1.9 ) — (0.1 ) (10.4 ) 0.2 (4.9 ) (2.4 ) (0.5 ) (4.5 ) Production tax credits and other credits (2.4 ) (4.8 ) — — — — — — — Noncontrolling interests (1.8 ) (3.7 ) — — — — — — — Statute of limitations expiration (2.6 ) (5.3 ) — — — — — — — Other (0.2 ) (1.1 ) 0.3 0.1 (0.2 ) (0.2 ) 1.4 (0.2 ) 0.8 Effective income tax rate 26.8 % 16.9 % 39.6 % 24.5 % 39.9 % 35.2 % 38.5 % 39.5 % 36.3 % _____________________ (a) DPL and ACE recognized a loss before income taxes for the year ended December 31, 2016 , and PHI recognized a loss before income taxes for the period of March 24, 2016, through December 31, 2016 . As a result, positive percentages represent an income tax benefit for the periods presented. (b) Includes a remeasurement of uncertain state income tax positions for Pepco and DPL. (c) At PECO, includes a cumulative adjustment related to an anticipated gas repairs tax return accounting method change. (d) Includes impacts of the PHI Global Settlement for Pepco, DPL, ACE, and PHI
Tax Effects of Temporary Differences	The tax effects of temporary differences and carryforwards, which give rise to significant portions of the deferred tax assets (liabilities), as of December 31, 2016 and 2015 are presented below: As of December 31, 2016 Successor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Plant basis differences $ (17,966 ) $ (4,192 ) $ (5,034 ) $ (3,095 ) $ (1,977 ) $ (1,678 ) $ (973 ) $ (869 ) $ (3,586 ) Accrual based contracts 434 (115 ) — — — — — — 548 Derivatives and other financial instruments (179 ) (162 ) (3 ) — — — — — (1 ) Deferred pension and postretirement obligation 2,287 (316 ) (453 ) (18 ) (43 ) (122 ) (74 ) (21 ) (111 ) Nuclear decommissioning activities (509 ) (509 ) — — — — — — — Deferred debt refinancing costs 325 44 (13 ) (1 ) (3 ) (7 ) (4 ) (2 ) 293 Regulatory assets and liabilities (3,319 ) — (226 ) 10 (240 ) (194 ) (75 ) (69 ) (1,205 ) Tax loss carryforward 189 61 29 — 22 27 39 14 77 Tax credit carryforward 446 493 — — — — — — — Investment in CENG (650 ) (650 ) — — — — — — — Other, net 1,485 403 351 99 27 66 34 34 225 Deferred income tax liabilities (net) $ (17,457 ) $ (4,943 ) $ (5,349 ) $ (3,005 ) $ (2,214 ) $ (1,908 ) $ (1,053 ) $ (913 ) $ (3,760 ) Unamortized investment tax credits (658 ) (626 ) (15 ) (1 ) (5 ) (2 ) (3 ) (4 ) (9 ) Total deferred income tax liabilities (net) and unamortized investment tax credits $ (18,115 ) $ (5,569 ) $ (5,364 ) $ (3,006 ) $ (2,219 ) $ (1,910 ) $ (1,056 ) $ (917 ) $ (3,769 ) As of December 31, 2015 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Plant basis differences $ (13,393 ) $ (4,269 ) $ (4,424 ) $ (2,901 ) $ (1,821 ) $ (1,599 ) $ (915 ) $ (791 ) $ (3,342 ) Accrual based contracts (136 ) (136 ) — — — — — — — Derivatives and other financial instruments (203 ) (181 ) (4 ) — — — — — (1 ) Deferred pension and postretirement obligation 1,801 (371 ) (505 ) (9 ) (47 ) (95 ) (82 ) (20 ) (92 ) Nuclear decommissioning activities (592 ) (592 ) — — — — — — — Deferred debt refinancing costs 133 48 (15 ) (1 ) (4 ) (8 ) (4 ) (3 ) (15 ) Regulatory assets and liabilities (1,706 ) — (219 ) 16 (264 ) (202 ) (91 ) (93 ) (414 ) Tax loss carryforward 103 56 — — 33 141 122 8 378 Tax credit carryforward 327 374 — — — — — — 6 Investment in CENG (595 ) (595 ) — — — — — — — Other, net 1,112 425 270 105 27 42 29 18 103 Deferred income tax liabilities (net) $ (13,149 ) $ (5,241 ) $ (4,897 ) $ (2,790 ) $ (2,076 ) $ (1,721 ) $ (941 ) $ (881 ) $ (3,377 ) Unamortized investment tax credits (622 ) (598 ) (17 ) (2 ) (5 ) (2 ) (4 ) (4 ) (15 ) Total deferred income tax liabilities (net) and unamortized investment tax credits $ (13,771 ) $ (5,839 ) $ (4,914 ) $ (2,792 ) $ (2,081 ) $ (1,723 ) $ (945 ) $ (885 ) $ (3,392 )
Summary of Loss Carryforwards	The following table provides the Registrants’ carryforwards and any corresponding valuation allowances as of December 31, 2016 . Successor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Federal Federal net operating loss $ 282 (a) $ 11 $ 82 $ — $ — $ 44 $ 38 $ 18 $ 121 Deferred taxes on Federal net operating loss 99 4 29 — — 15 13 6 42 Federal general business credits carryforwards 511 (b) 509 1 — 1 — — — — State State net operating losses and credit carryforwards 3,501 (c) 1,245 (c) — — 425 (d) 360 (e) 639 (f) 272 (g) 1,522 (h) Deferred taxes on state tax attributes (net) 186 65 — — 23 20 36 16 86 Valuation allowance on state tax attributes 20 9 — — 1 — — — 10 _____________________ (a) Exelon's federal net operating loss will begin expiring in 2032. (b) Exelon’s federal general business credit carryforwards will begin expiring in 2033. (c) Exelon’s and Generation's state net operating losses and credit carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2017. (d) BGE's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2026. (e) Pepco's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2028. (f) DPL's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2023. (g) ACE's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2032. (h) PHI's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2023.
Reconciliation of Unrecognized Tax Benefits Excluding Amounts Pertaining to Examined Tax Returns Foll Forward	following tables provide a reconciliation of the Registrants’ unrecognized tax benefits as of December 31, 2016 , 2015 and 2014 : Successor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Unrecognized tax benefits at January 1, 2016 $ 1,078 $ 534 $ 142 $ — $ 120 $ 8 $ 3 $ — $ 22 Merger balance transfer 22 5 — — — — — — (5 ) Increases based on tax positions related to 2016 108 10 — — — 21 16 22 59 Change to positions that only affect timing (332 ) (12 ) (154 ) — — — — — — Increases based on tax positions prior to 2016 88 — — — — 51 18 — 96 Decreases based on tax positions prior to 2016 (21 ) (20 ) — — — — — — — Decrease from settlements with taxing authorities (27 ) (27 ) — — — — — — — Decreases from expiration of statute of limitations — — — — — — — — — Unrecognized tax benefits at December 31, 2016 $ 916 $ 490 $ (12 ) $ — $ 120 $ 80 $ 37 $ 22 $ 172 Predecessor Generation ComEd PECO BGE Pepco DPL ACE PHI Unrecognized tax benefits at January 1, 2015 $ 1,829 $ 1,357 $ 149 $ 44 $ — $ — $ — $ — $ 702 Increases based on tax positions related to 2015 108 — — — 106 — — — — Change to positions that only affect timing (705 ) (659 ) (7 ) (44 ) — — — — (688 ) Increases based on tax positions prior to 2015 79 65 — — 14 8 3 — 11 Decreases based on tax positions prior to 2015 (116 ) (112 ) — — — — — — — Decrease from settlements with taxing authorities (31 ) (31 ) — — — — — — — Decreases from expiration of statute of limitations (86 ) (86 ) — — — — — — (3 ) Unrecognized tax benefits at December 31, 2015 $ 1,078 $ 534 $ 142 $ — $ 120 $ 8 $ 3 $ — $ 22 Predecessor Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Unrecognized tax benefits at January 1, 2014 $ 2,175 $ 1,415 $ 324 $ 44 $ — $ 45 $ 3 $ 3 $ 743 Increases based on tax positions related to 2014 15 15 — — — — — — — Change to positions that only affect timing (255 ) 33 (175 ) — — (45 ) (3 ) (3 ) (41 ) Increases based on tax positions prior to 2014 18 18 — — — — — — — Decreases based on tax positions prior to 2014 (1 ) (2 ) — — — — — — — Decreases from settlements with taxing authorities (35 ) (34 ) — — — — — — — Decreases from expiration of statute of limitations (88 ) (88 ) — — — — — — — Unrecognized tax benefits at December 31, 2014 $ 1,829 $ 1,357 $ 149 $ 44 $ — $ — $ — $ — $ 702
Interest Income and Interest Expense Disclosure [Table Text Block]	following tables set forth the net interest and penalty expense, including interest and penalties related to tax positions, recognized in Interest expense, net and Other, net in Other income and deductions in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Net interest expense (income) for the years ended Exelon Generation ComEd PECO BGE Pepco DPL ACE December 31, 2016 $ 165 $ (13 ) $ 117 $ — $ — $ 6 $ — $ (1 ) December 31, 2015 (13 ) (31 ) 7 — — (4 ) — — December 31, 2014 (36 ) (50 ) 6 — 1 (1 ) — (1 ) Net penalty expense (income) for the years ended Exelon Generation ComEd PECO BGE Pepco DPL ACE December 31, 2016 $ 106 $ — $ 86 — $ — $ — $ — $ — $ — December 31, 2015 — — — — — — — — December 31, 2014 — — — — — — — — Successor Predecessor PHI March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 December 31, 2015 December 31, 2014 Net interest expense (income) $ (2 ) $ — $ (34 ) $ — Net penalty expense (income) — — — — D
Summary of Open Tax Years by Jurisdiction	ription of tax years that remain open to assessment by major jurisdiction Taxpayer Open Years Exelon (and predecessors) and subsidiaries consolidated Federal income tax returns 1999, 2001-2015 PHI Holdings and subsidiaries consolidated Federal income tax returns 2013-2015 Exelon and subsidiaries Illinois unitary income tax returns 2010-2015 Constellation combined New York corporate income tax returns 2010-March 2012 Exelon combined New York corporate income tax returns 2011-2015 Various separate company (excluding PECO) Pennsylvania corporate net income tax returns 2011-2015 PECO Pennsylvania separate company returns 2010-2015 DPL Delaware separate company returns Same as Federal ACE New Jersey separate company returns 2012-2015 Various separate company Maryland corporate net income tax returns Same as Federal Washington D.C. corporate income tax returns 2013-2015 O

Asset Retirement Obligations (T

Asset Retirement Obligations (Tables)	12 Months Ended
	Dec. 31, 2016
Asset Retirement Obligation Disclosure [Abstract]
Nuclear Decommissioning Asset Retirement Obligation Rollforward	The following table provides a rollforward of the nuclear decommissioning ARO reflected on Exelon’s and Generation’s Consolidated Balance Sheets, from January 1, 2015 to December 31, 2016 : Exelon and Generation Nuclear decommissioning ARO at January 1, 2015 $ 6,961 Accretion expense 387 Net increase for changes in and timing of estimated future cash flows 901 Costs incurred related to decommissioning plants (3 ) Nuclear decommissioning ARO at December 31, 2015 (a) 8,246 Accretion expense 436 Net increase for changes in and timing of estimated future cash flows 61 Costs incurred related to decommissioning plants (9 ) Nuclear decommissioning ARO at December 31, 2016 (a) $ 8,734 _________________________ (a) Includes $ 10 million and $ 7 million as the current portion of the ARO at December 31, 2016 and 2015 , respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets.
Unrealized Gains Losses On Nuclear Decommissioning Trust Funds	The following table provides unrealized gains on NDT funds for 2016 , 2015 and 2014 : Exelon and Generation For the Years Ended December 31, 2016 2015 2014 Net unrealized gains (losses) on decommissioning trust funds—Regulatory Agreement Units (a) $ 216 $ (282 ) $ 180 Net unrealized gains (losses) on decommissioning trust funds—Non-Regulatory Agreement Units (b)(c) 194 (197 ) 134 _______________________ (a) Net unrealized gains (losses) related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets. (b) Excludes $ (1) million , $7 million and $ 29 million of net unrealized gains (losses) related to the Zion Station pledged assets in 2016 , 2015 and 2014 , respectively. Net unrealized gains related to Zion Station pledged assets are included in the Payable for Zion Station decommissioning on Exelon’s and Generation’s Consolidated Balance Sheets. (c) Net unrealized gains (losses) related to Generation’s NDT funds with Non-Regulatory Agreement Units are included within Other, net in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income.
Nuclear Decommissioning Pledged Assets	The following table provides the pledged assets and payables to ZionSolutions, and withdrawals by ZionSolutions at December 31, 2016 and 2015 : Exelon and Generation 2016 2015 Carrying value of Zion Station pledged assets $ 113 $ 206 Payable to Zion Solutions (a) 104 189 Current portion of payable to Zion Solutions (b) 90 99 Cumulative withdrawals by Zion Solutions to pay decommissioning costs (c) 878 786 ___________________ (a) Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT Funds. The NDT Funds will be utilized to satisfy the tax obligations as gains and losses are realized. (b) Included in Other current liabilities within Exelon’s and Generation’s Consolidated Balance Sheets. (c) Includes project expenses to decommission Zion Station and estimated tax payments on Zion Station NDT fund earnings.
Non Nuclear Decommissioning Asset Retirement Obligation Rollforward	The following table provides a rollforward of the non-nuclear AROs reflected on the Registrants’ Consolidated Balance Sheets from January 1, 2015 to December 31, 2016 : Successor Exelon Generation ComEd PECO BGE PHI (f) Pepco DPL ACE Non-nuclear AROs at January 1, 2015 $ 346 $ 194 $ 104 $ 30 $ 18 $ — $ — $ — $ — Net (decrease) increase due to changes in, and timing of, estimated future cash flows (a) (10 ) (12 ) 6 (4 ) — — — — — Development projects (b) 10 10 — — — — — — — Accretion expense (c) 16 10 5 1 — — — — — Sale of generating assets (d) (2 ) (2 ) — — — — — — — Payments (5 ) (3 ) (2 ) — — — — — — Non-nuclear AROs at December 31, 2015 (e) 355 197 113 27 18 — — — — Merger with PHI (g) 8 1 — — — — — — — Net increase (decrease) due to changes in, and timing of, estimated future cash flows (a) 34 8 4 1 7 14 2 9 3 Development projects (b) 11 11 — — — — — — — Accretion expense (c) 18 10 7 1 — — — — — Sale of generating assets (d) (22 ) (22 ) — — — — — — — Payments (11 ) (6 ) (3 ) (1 ) (1 ) — — — — Non-nuclear AROs at December 31, 2016 (e) $ 393 $ 199 $ 121 $ 28 $ 24 $ 14 $ 2 $ 9 $ 3 Predecessor PHI (f) Non-nuclear AROs at January 1, 2015 $ 7 Accretion expense (c) 1 Non-nuclear AROs at December 31, 2015 $ 8 Non-nuclear AROs at March 23, 2016 $ 8 ________________________ (a) During the year ended December 31, 2016 , Generation recorded an increase of $1 million in Operating and maintenance expense. ComEd, PECO and BGE did not record any adjustments in Operating and maintenance expense for the year ended December 31, 2016 . During the year ended December 31, 2015 , Generation recorded a decrease of $(2) million in Operating and maintenance expense. ComEd, PECO and BGE did not record any adjustments in Operating and maintenance expense for the year ended December 31, 2015 . (b) Relates to new AROs recorded due to the construction of solar, wind and other non-nuclear generating sites. (c) For ComEd, PECO, and BGE, the majority of the accretion is recorded as an increase to a regulatory asset due to the associated regulatory treatment. (d) Reflects a reduction to the ARO resulting primarily from the sales of the New Boston generating site and Upstream business in 2016 and Schuylkill generating station in 2015. See Note 4 — Mergers, Acquisitions, and Dispositions for further information. (e) Excludes $1 million , $2 million and $3 million as the current portion of the ARO at December 31, 2016 for Generation, ComEd and BGE, respectively. Excludes $5 million , $2 million and $1 million as the current portion of the ARO at December 31, 2015 for Generation, ComEd and BGE, respectively. This is included in Other current liabilities on the Registrants' respective Consolidated Balance Sheets. (f) For PHI, the successor period includes activity for the period of March 24, 2016 through December 31, 2016. The PHI predecessor periods include activity for the year ended December 31, 2015 and the period January 1, 2016 through March 23, 2016. (g) Following the completion of the PHI merger on March 23, 2016, PHI's AROs related to its unregulated business interests were transferred to Exelon and Generation.

Retirement Benefits (Tables)

Retirement Benefits (Tables)	12 Months Ended
	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Schedule Of Pension And Other Postretirement Participation	The table below shows the pension and other postretirement benefit plans in which employees of each operating company participated at December 31, 2016 . Operating Company (e) Name of Plan: Generation ComEd PECO BGE BSC PHI Pepco DPL ACE Qualified Pension Plans: Exelon Corporation Retirement Program (a) X X X X X Exelon Corporation Cash Balance Pension Plan (a) X X X X X Exelon Corporation Pension Plan for Bargaining Unit Employees (a) X X X Exelon New England Union Employees Pension Plan (a) X Exelon Employee Pension Plan for Clinton, TMI and Oyster Creek (a) X X X X Pension Plan of Constellation Energy Group, Inc. (b) X X X X X Pension Plan of Constellation Energy Nuclear Group, LLC (c) X X X Nine Mile Point Pension Plan (c) X X Constellation Mystic Power, LLC Union Employees Pension Plan Including Plan A and Plan B (b) X Pepco Holdings LLC Retirement Plan (d) X X X X X Non-Qualified Pension Plans: Exelon Corporation Supplemental Pension Benefit Plan and 2000 Excess Benefit Plan (a) X X X X Exelon Corporation Supplemental Management Retirement Plan (a) X X X X X Constellation Energy Group, Inc. Senior Executive Supplemental Plan (b) X X X Constellation Energy Group, Inc. Supplemental Pension Plan (b) X X X Constellation Energy Group, Inc. Benefits Restoration Plan (b) X X X X Constellation Energy Nuclear Plan, LLC Executive Retirement Plan (c) X X Constellation Energy Nuclear Plan, LLC Benefits Restoration Plan (c) X X Baltimore Gas & Electric Company Executive Benefit Plan (b) X X X Baltimore Gas & Electric Company Manager Benefit Plan (b) X X X X Pepco Holdings LLC 2011 Supplemental Executive Retirement Plan (d) X X X X X Conectiv Supplemental Executive Retirement Plan (d) X X X X Pepco Holdings LLC Combined Executive Retirement Plan (d) X X X Atlantic City Electric Director Retirement Plan (d) X X Operating Company (e) Name of Plan: Generation ComEd PECO BGE BSC PHI Pepco DPL ACE Other Postretirement Benefit Plans: PECO Energy Company Retiree Medical Plan (a) X X X X X Exelon Corporation Health Care Program (a) X X X X X Exelon Corporation Employees’ Life Insurance Plan (a) X X X X X Exelon Corporation Health Reimbursement (a) X X X X X Constellation Energy Group, Inc. Retiree Medical Plan (b) X X X X X Constellation Energy Group, Inc. Retiree Dental Plan (b) X X X Constellation Energy Group, Inc. Employee Life Insurance Plan and Family Life Insurance Plan (b) X X X X X Constellation Mystic Power, LLC Post-Employment Medical Account Savings Plan (b) X Exelon New England Union Post-Employment Medical Savings Account Plan (a) X Retiree Medical Plan of Constellation Energy Nuclear Group LLC (c) X X X Retiree Dental Plan of Constellation Energy Nuclear Group LLC (c) X X X Nine Mile Point Nuclear Station, LLC Medical Care and Prescription Drug Plan for Retired Employees (c) X X Pepco Holdings LLC Welfare Plan for Retirees (d) X X X X X ______________________ (a) These plans are collectively referred to as the legacy Exelon plans. (b) These plans are collectively referred to as the legacy Constellation Energy Group (CEG) Plans. (c) These plans are collectively referred to as the legacy CENG plans. (d) These plans are collectively referred to as the legacy PHI plans. (e) Employees generally remain in their legacy benefit plans when transferring between operating companies.
Defined Benefit Plan Change In Benefit Obligation RollForward	The following tables provide a rollforward of the changes in the benefit obligations and plan assets for the most recent two years for all plans combined: Pension Benefits Other Postretirement Benefits Exelon 2016(b) 2015 2016(b) 2015 Change in benefit obligation: Net benefit obligation at beginning of year $ 17,753 $ 18,256 $ 3,938 $ 4,197 Service cost 354 326 107 119 Interest cost 830 710 185 167 Plan participants’ contributions — — 54 42 Actuarial (gain) loss 567 (582 ) (136 ) (341 ) Plan amendments (60 ) — — (23 ) Acquisitions/divestitures (a) 2,667 — 589 — Settlements — (34 ) — — Gross benefits paid (1,051 ) (923 ) (280 ) (223 ) Net benefit obligation at end of year $ 21,060 $ 17,753 $ 4,457 $ 3,938 Pension Benefits Other Postretirement Benefits Exelon 2016(b) 2015 2016(b) 2015 Change in plan assets: Fair value of net plan assets at beginning of year $ 14,347 $ 14,874 $ 2,293 $ 2,430 Actual return on plan assets 1,061 (32 ) 128 4 Employer contributions 347 462 50 40 Plan participants’ contributions — — 54 42 Gross benefits paid (1,051 ) (923 ) (280 ) (223 ) Acquisitions/divestitures (a) 2,087 — 333 — Settlements — (34 ) — — Fair value of net plan assets at end of year $ 16,791 $ 14,347 $ 2,578 $ 2,293 Predecessor Pension Benefits Other Postretirement Benefits PHI January 1, 2016 to March 23, 2016 2015 January 1, 2016 to March 23, 2016 2015 Change in benefit obligation: Net benefit obligation at beginning of the period $ 2,490 $ 2,638 $ 563 $ 632 Service cost 12 57 1 7 Interest cost 26 109 6 24 Actuarial (gain) loss (30 ) (151 ) (5 ) (61 ) Gross benefits paid (2 ) (163 ) (1 ) (39 ) Net benefit obligation at end of the period $ 2,496 $ 2,490 $ 564 $ 563 Predecessor Pension Benefits Other Postretirement Benefits PHI January 1, 2016 to March 23, 2016 2015 January 1, 2016 to March 23, 2016 2015 Change in plan assets: Fair value of net plan assets at beginning of the period $ 2,018 $ 2,236 $ 348 $ 367 Actual return on plan assets — (61 ) — 1 Employer and plan participant contributions 4 6 1 5 Gross benefits paid by plan (2 ) (163 ) (1 ) (25 ) Fair value of net plan assets at end of the period $ 2,020 $ 2,018 $ 348 $ 348 ____________________ (a) Effective March 23, 2016 , Exelon became the sponsor of PHI's defined benefit pension and other postretirement benefit plans. (b) 2016 amounts include PHI for the period of March 24, 2016 through December 31, 2016.
Schedule of Amounts Recognized in Balance Sheet	Exelon and PHI present their benefit obligations and plan assets net on their balance sheet within the following line items: Pension Benefits Other Postretirement Benefits Exelon 2016(a) 2015 2016(a) 2015 Other current liabilities $ 21 $ 21 $ 31 $ 27 Pension obligations 4,248 3,385 — — Non-pension postretirement benefit obligations — — 1,848 1,618 Unfunded status (net benefit obligation less plan assets) $ 4,269 $ 3,406 $ 1,879 $ 1,645 Pension Benefits Other Predecessor Predecessor PHI 2015 2015 Other current liabilities $ 6 $ — Pension obligations 466 — Non-pension postretirement benefit obligations — 215 Unfunded status (net benefit obligation less plan assets) $ 472 $ 215
Schedule of Defined Benefit Plans Disclosures	The following tables present the components of Exelon’s net periodic benefit costs, prior to any capitalization, for the years ended December 31, 2016 , 2015 and 2014 and the components of PHI's predecessor net periodic benefit costs, prior to any capitalization, for the years ended December 31, 2015 and 2014 , and the period January 1, 2016 to March 23, 2016 . Pension Benefits Other Postretirement Benefits Exelon 2016(a) 2015 2014 2016(a) 2015 2014 Components of net periodic benefit cost: Service cost $ 354 $ 326 $ 293 $ 107 $ 119 $ 117 Interest cost 830 710 749 185 167 186 Expected return on assets (1,141 ) (1,026 ) (994 ) (162 ) (151 ) (154 ) Amortization of: Prior service cost (credit) 14 13 14 (185 ) (174 ) (122 ) Actuarial loss 554 571 420 63 80 50 Settlement and other charges (b) 2 2 2 — — — Net periodic benefit cost $ 613 $ 596 $ 484 $ 8 $ 41 $ 77 _______________________ (a) 2016 amounts include PHI for the period of March 24, 2016 through December 31, 2016. (b) 2016 amount includes an additional termination benefit for PHI. Predecessor Pension Benefits Other PHI January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 Components of net periodic benefit cost: Service cost $ 12 $ 57 $ 44 $ 1 $ 7 $ 7 Interest cost 26 109 109 6 24 26 Expected return on assets (30 ) (140 ) (141 ) (5 ) (22 ) (24 ) Amortization of: Prior service cost (credit) — 2 2 (3 ) (13 ) (13 ) Actuarial loss 14 65 45 2 8 3 Net periodic benefit cost $ 22 $ 93 $ 59 $ 1 $ 4 $ (1 )
Changes In Plan Assets And Benefit Obligations Recognized In OCI And Regulatory Assets	The following tables provide the components of AOCI and regulatory assets (liabilities) for the years ended December 31, 2016 , 2015 and 2014 for all plans combined and the components of PHI's predecessor AOCI and regulatory assets (liabilities) for the years ended December 31, 2015 and 2014 , and the period January 1, 2016 to March 23, 2016 . Pension Benefits Other Postretirement Benefits Exelon 2016(a) 2015 2014 2016(a) 2015 2014 Changes in plan assets and benefit obligations recognized in AOCI and regulatory assets (liabilities): Current year actuarial loss (gain) $ 644 $ 476 $ 1,639 $ (101 ) $ (194 ) $ 561 Amortization of actuarial loss (554 ) (571 ) (420 ) (63 ) (80 ) (50 ) Current year prior service (credit) cost (60 ) — — — (23 ) (1,012 ) Amortization of prior service (cost) credit (14 ) (13 ) (14 ) 185 174 122 Settlements — (2 ) (2 ) — — — Acquisitions 994 — — 94 — — Total recognized in AOCI and regulatory assets (liabilities) $ 1,010 $ (110 ) $ 1,203 $ 115 $ (123 ) $ (379 ) Total recognized in AOCI $ 51 $ (64 ) $ 788 $ 20 $ (63 ) $ (162 ) Total recognized in regulatory assets (liabilities) $ 959 $ (46 ) $ 415 $ 95 $ (60 ) $ (217 ) Predecessor Pension Benefits Other PHI January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 Changes in plan assets and benefit Current year actuarial loss (gain) $ — $ 50 $ 276 $ — $ (39 ) $ 62 Amortization of actuarial loss (14 ) (65 ) (45 ) (2 ) (8 ) (3 ) Amortization of prior service (cost) credit — (2 ) (2 ) 3 13 13 Total recognized in AOCI and regulatory assets (liabilities) $ (14 ) $ (17 ) $ 229 $ 1 $ (34 ) $ 72 Total recognized in AOCI $ (1 ) $ (11 ) $ 17 $ — $ — $ — Total recognized in regulatory assets (liabilities) $ (13 ) $ (6 ) $ 212 $ 1 $ (34 ) $ 72
Changes In Plan Assets And Benefit Obligations Not Recognized In OCI And Regulatory Assets	The following table provides the components of gross accumulated other comprehensive loss and regulatory assets (liabilities) that have not been recognized as components of periodic benefit cost at December 31, 2016 and 2015 , respectively, for all plans combined: Predecessor Predecessor Exelon PHI Exelon PHI Pension Benefits Other Postretirement Benefits 2016(a) 2015 2015 2016(a) 2015 2015 Prior service cost (credit) $ (31 ) $ 36 $ 6 $ (710 ) $ (812 ) $ (88 ) Actuarial loss 8,387 7,310 910 724 711 128 Total (a) $ 8,356 $ 7,346 $ 916 $ 14 $ (101 ) $ 40 Total included in AOCI $ 4,297 $ 4,246 $ 46 $ (42 ) $ (63 ) $ — Total included in regulatory assets (liabilities) $ 4,059 $ 3,100 $ 870 $ 56 $ (38 ) $ 40 ______________________ (a) Effective March 23, 2016 , Exelon became the sponsor of PHI's defined benefit pension and other postretirement benefit plans, and assumed PHI's benefit plan obligations and related assets. The following table provides the impact to Exelon’s AOCI and regulatory assets (liabilities) at December 31, 2016 as a result of the components of periodic benefit costs that are expected to be amortized in 2017 . These estimates are subject to the completion of an actuarial valuation of Exelon’s pension and other postretirement benefit obligations, which will reflect actual census data as of January 1, 2017 and actual claims activity as of December 31, 2016 . The valuation is expected to be completed in the first quarter of 2017 for the majority of the benefit plans. Pension Benefits Other Postretirement Benefits Prior service cost (credit) $ 1 $ (188 ) Actuarial loss 605 55 Total (a) $ 606 $ (133 ) ___________________ (a) Of the $606 million related to pension benefits at December 31, 2016 , $297 million and $309 million are expected to be amortized from AOCI and regulatory assets in 2017 , respectively. Of the $(133) million related to other postretirement benefits at December 31, 2016 , $(70) million and $(63) million are expected to be amortized from AOCI and regulatory assets (liabilities) in 2017 , respectively. Assumptions The measurement of the plan obligation
Defined Benefit Plan Amounts That Will Be Amortized From Accumulated Other Comprehensive Income Loss And Regulatory Assets In Next Fiscal Year	The following table provides the impact to Exelon’s AOCI and regulatory assets (liabilities) at December 31, 2016 as a result of the components of periodic benefit costs that are expected to be amortized in 2017 . These estimates are subject to the completion of an actuarial valuation of Exelon’s pension and other postretirement benefit obligations, which will reflect actual census data as of January 1, 2017 and actual claims activity as of December 31, 2016 . The valuation is expected to be completed in the first quarter of 2017 for the majority of the benefit plans. Pension Benefits Other Postretirement Benefits Prior service cost (credit) $ 1 $ (188 ) Actuarial loss 605 55 Total (a) $ 606 $ (133 ) ___________________ (a) Of the $606 million related to pension benefits at December 31, 2016 , $297 million and $309 million are expected to be amortized from AOCI and regulatory assets in 2017 , respectively. Of the $(133) million related to other postretirement benefits at December 31, 2016 , $(70) million and $(63) million are expected to be amortized from AOCI and regulatory assets (liabilities) in 2017 , respectively.
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Benefit Obligation	The following assumptions were used to determine the benefit obligations for the plans at December 31, 2016 , 2015 and 2014 . Assumptions used to determine year-end benefit obligations are the assumptions used to estimate the subsequent year’s net periodic benefit costs. Pension Benefits Other Postretirement Benefits Exelon 2016 2015 2014 2016 2015 2014 Discount rate 4.04 % (a) 4.29 % (b) 3.94 % (c) 4.04 % (a) 4.29 % (b) 3.92 % (c) Rate of compensation increase (d) (d) (d) (d) (d) (d) Mortality table RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) Health care cost trend on covered charges N/A N/A N/A 5.50% with ultimate trend of 5.00% in 2017 5.50% 6.00% decreasing to ultimate trend of 5.00% in 2017 Predecessor Predecessor Pension Benefits Other Postretirement Benefits PHI January 1, 2016 to March 23, 2016 (e) 2015 2014 January 1, 2016 to March 23, 2016 (e) 2015 2014 Discount rate 4.65%/4.55% (f) 4.20 % 4.55 % 4.15 % Rate of compensation 5.00 % 5.00 % 5.00 % 5.00 % Mortality table RP-2014 table with improvement scale MP-2015 RP-2014 table with improvement scale MP-2014 RP-2014 table with improvement scale MP-2015 RP-2014 table with improvement scale MP-2014 Health care cost trend on covered charges N/A N/A 6.33% pre-65 and 5.40% post-65 6.67% pre-65 and 5.50% post-65 _____________________________ (a) The discount rates above represent the blended rates used to determine the majority of Exelon’s pension and other postretirement benefits obligations as of December 31, 2016. Certain benefit plans used individual rates ranging from 3.66% - 4.11% and 4.00% - 4.17% for pension and other postretirement plans, respectively. (b) The discount rates above represent the blended rates used to determine the majority of Exelon’s pension and other postretirement benefits obligations as of December 31, 2015. Certain benefit plans used individual rates ranging from 3.68% - 4.14% and 4.32% - 4.43% for pension and other postretirement plans, respectively. (c) The discount rates above represent the blended rates used to determine the majority of Exelon’s pension and other postretirement benefits obligations as of December 31, 2014. Certain benefit plans used individual rates ranging from 3.29% - 3.82% and 3.99% - 4.06% for pension and other postretirement plans, respectively. (d) The legacy Exelon, CEG and CENG pension and other postretirement plans used a rate of compensation increase of 3.25% through 2019 and 3.75% thereafter, while the legacy PHI pension and other postretirement plans used a weighted-average rate of compensation increase of 5% for all periods. (e) Obligation was not remeasured during this period. (f) The discount rate for the qualified and nonqualified pension plans was 4.65% and 4.55%, respectively.
Defined Benefit Plan Weighted Average Assumptions Used In Calculating Net Periodic Benefit Cost	The following assumptions were used to determine the net periodic benefit costs for the plans for the years ended December 31, 2016 , 2015 and 2014 , as well as for the PHI predecessor period January 1, 2016 to March 23, 2016 : Pension Benefits Other Postretirement Benefits Exelon 2016 2015 2014 2016 2015 2014 Discount rate 4.29 % (a) 3.94 % (b) 4.80 % (c) 4.29 % (a) 3.92 % (b) 4.90 % (c) Expected return on plan assets 7.00 % (d) 7.00 % (d) 7.00 % (d) 6.71 % (d) 6.50 % (d) 6.59 % (d) Rate of compensation increase (e) (e) Mortality table RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table with Scale AA improvements RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table projected to 2012 with improvement scale AA, with Scale BB-2D improvements (adjusted) RP-2000 table with Scale AA improvements Health care cost trend on covered charges N/A N/A N/A 5.50% decreasing to ultimate trend of 5.00% in 2017 6.00% 6.00% decreasing to ultimate trend of 5.00% in 2017 Predecessor Predecessor Pension Benefits Other Postretirement Benefits PHI January 1, 2016 to March 23, 2016 2015 2014 January 1, 2016 to March 23, 2016 2015 2014 Discount rate 4.65%/4.55% (h) 4.20 % 5.05 % 4.55 % 4.15 % 5.00 % Expected return on plan assets (g) 6.50 % 6.50 % 7.00 % 6.75 % 6.75 % 7.25 % Rate of compensation 5.00 % 5.00 % 5.00 % 5.00 % 5.00 % 5.00 % Mortality table RP-2014 table with improvement scale MP-2015 RP-2014 table with improvement scale MP-2014 2014 Mortality tables prescribed by the Pension Protection Act of 2006 RP-2014 table with improvement scale MP-2015 RP-2014 table with improvement scale MP-2014 2014 Mortality tables prescribed by the Pension Protection Act of 2006 Health care cost trend on covered charges N/A N/A N/A 6.33% pre-65 and 5.40% post-65 6.67% pre-65 and 5.50% post-65 7.00% pre-65 and 5.60% post-65 ___________________________ (a) The discount rates above represent the blended rates used to establish the majority of Exelon’s pension and other postretirement benefits costs for the year ended December 31, 2016 . Certain benefit plans used individual rates ranging from 3.68% - 4.14% and 4.32% - 4.43% for pension and other postretirement plans, respectively. (b) The discount rates above represent the blended rates used to establish the majority of Exelon's pension and other postretirement benefits costs for the year ended December 31, 2015 . Certain benefit plans used individual rates ranging from 3.29% - 3.82% and 3.99% - 4.06% for pension and other postretirement plans, respectively. (c) The discount rates above represent the blended rates used to establish the majority of Exelon’s pension and other postretirement benefits costs for the year ended December 31, 2014 . Certain of the other postretirement benefit plans were remeasured as of April 30, 2014 using an expected long-term rate of return on plan assets of 6.59% and a discount rate of 4.30% . Costs for the year ended December 31, 2014 reflect the impact of this remeasurement. On April 1, 2014, Generation assumed operational control of CENG’s nuclear fleet. As a result, Exelon became the sponsor of CENG’s legacy pension and OPEB plans effective July 14, 2014; discount rates for those plans, impacting 2014 costs, ranged from 3.60% - 4.30% and 4.09% - 4.55% , respectively. See Note 5 - Investment in Constellation Energy Nuclear Group, LLC for further information. (d) Not applicable to pension and other postretirement benefit plans that do not have plan assets. (e) 3.25% through 2019 and 3.75% thereafter. (f) 3.25% through 2018 and 3.75% thereafter. (g) Expected return on other postretirement benefit plan assets is pre-tax. (h) The discount rate for the qualified and nonqualified pension plans was 4.65% and 4.55%, respectively.
Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates	A one percentage point change in assumed health care cost trend rates would have the following effects: Effect of a one percentage point increase in assumed health care cost trend: on 2016 total service and interest cost components $ 9 on postretirement benefit obligation at December 31, 2016 105 Effect of a one percentage point decrease in assumed health care cost trend: on 2016 total service and interest cost components (8 ) on postretirement benefit obligation at December 31, 2016 (95 )
Pension And Other Postretirement Benefit Contributions	The following table provides all registrants' planned contributions to the qualified pension plans, planned benefit payments to non-qualified pension plans, and planned contributions to other postretirement plans in 2017: Qualified Pension Plans (a) Non-Qualified Pension Plans (b) Other Postretirement Benefits (c) Exelon $ 310 $ 23 $ 44 Generation 127 6 12 ComEd 33 1 2 PECO 23 1 — BGE 38 2 16 PHI 60 8 12 Pepco 60 1 10 DPL — — — ACE — — — _____________________ (a) Exelon's and Generation's expected qualified pension plan contributions above include $21 million related to the legacy CENG plans that will be funded by CENG as provided in an EMA between Exelon and CENG. (b) Unlike the qualified pension plans, Exelon’s non-qualified pension plans are not funded. (c) Unlike the qualified pension plans, other postretirement plans are not subject to statutory minimum contribution requirements. OPEB funding generally follows accounting costs however, Exelon’s management has historically considered several factors in determining the level of contributions to its other postretirement benefit plans, including liabilities management, levels of benefit claims paid and regulatory implications (amounts deemed prudent to meet regulatory expectations and best assure continued rate recovery). These amounts include benefit payments related to unfunded plans. The following tables provide contributions to the pension and other postretirement benefit plans: Pension Benefits Other Postretirement Benefits 2016 (a) 2015 (a) 2014 (a) 2016 2015 2014 Exelon $ 347 $ 462 $ 332 $ 50 $ 40 $ 291 Generation 140 231 173 12 14 124 ComEd 33 143 122 5 7 125 PECO 30 40 11 — — 5 BGE 31 1 — 18 16 17 BSC (b) 39 47 26 3 3 20 Pepco 24 — — 8 2 1 DPL 22 — — — — — ACE 15 — — 2 3 3 PHISCO (c) 17 — — 2 — — Pension Benefits Other Postretirement Benefits Successor Predecessor Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 PHI $ 74 $ 4 $ — $ — $ 12 $ — $ 5 $ 4 _________________________ (a) Exelon's and Generation's pension contributions include $25 million , $36 million and $43 million related to the legacy CENG plans that was funded by CENG as provided in an Employee Matters Agreement (EMA) between Exelon and CENG for the years ended December 31, 2016 , 2015 and 2014 , respectively. (b) Includes $6 million , $5 million , and $9 million of pension contributions funded by Exelon Corporate, for the years ended December 31, 2016 , 2015 , and 2014 , respectively. (c)
Defined Benefit Plan Estimated Future Benefit Payments	Estimated Future Benefit Payments Estimated future benefit payments to participants in all of the pension plans and postretirement benefit plans at December 31, 2016 were: Pension Benefits Other Postretirement Benefits 2017 $ 1,360 $ 244 2018 1,170 250 2019 1,191 256 2020 1,223 263 2021 1,275 272 2022 through 2026 6,791 1,456 Total estimated future benefit payments through 2026 $ 13,010 $ 2,741
Schedule Of Pension And Other Postretirement Benefit Costs	an costs. These amounts include the recognized contractual termination benefit charges, curtailment gains, and settlement charges: For the Year Ended December 31, Exelon Generation ComEd PECO BGE BSC (a) Pepco DPL ACE PHISCO (a) 2016(b) $ 621 $ 218 $ 166 $ 33 $ 68 $ 48 $ 31 $ 18 $ 15 $ 47 2015 637 269 206 39 66 57 30 15 15 37 2014 561 250 162 36 67 46 22 7 13 16 Successor Predecessor PHI March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 Pension and Other Postretirement Benefit Costs $ 88 $ 23 $ 97 $ 58 _____________________ (a) These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO, BGE, Pepco, DPL or ACE amounts
Defined Benefit Plan Weighted Average Asset Allocations And Target Allocations	vely. Exelon’s pension and other postretirement benefit plan target asset allocations at December 31, 2016 and 2015 asset allocations were as follows: Pension Plans Predecessor Exelon PHI Percentage of Plan Assets at December 31, Asset Category Target Allocation 2016 2015 2015 Equity securities 33 % 33 % 35 % 28 % Fixed income securities 39 % 39 34 66 Alternative investments (a) 28 % 28 31 6 Total 100 % 100 % 100 % Other Postretirement Benefit Plans Predecessor Exelon PHI Percentage of Plan Assets at December 31, Asset Category Target Allocation 2016 2015 2015 Equity securities 43 % 47 % 43 % 63 % Fixed income securities 28 % 29 27 34 Alternative investments (a) 29 % 24 30 3 Total 100 % 100 % 100 % ___________________ (a) Alternative investments include private equity, hedge funds, real estate, and private credit.
Defined Benefit Plan Fair Value Of Plan Assets	Fair Value Measurements The following tables present pension and other postretirement benefit plan assets measured and recorded at fair value on the Registrants' Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy at December 31, 2016 and 2015 : Exelon At December 31, 2016(a)(d) Level 1 Level 2 Level 3 Not subject to leveling Total Pension plan assets Cash equivalents $ 325 $ — $ — $ — $ 325 Equities (b) 3,144 — 2 2,535 5,681 Fixed income: U.S. Treasury and agencies 1,008 192 — — 1,200 State and municipal debt — 64 — — 64 Corporate debt — 3,641 206 — 3,847 Other (b) — 340 — 748 1,088 Fixed income subtotal 1,008 4,237 206 748 6,199 Private equity — — — 991 991 Hedge funds — — — 1,962 1,962 Real estate — — — 828 828 Private credit — — — 833 833 Pension plan assets subtotal $ 4,477 $ 4,237 $ 208 $ 7,897 $ 16,819 At December 31, 2016(a)(d) Level 1 Level 2 Level 3 Not subject to leveling Total Other postretirement benefit plan assets Cash equivalents $ 24 $ — $ — $ — $ 24 Equities 547 2 — 644 1,193 Fixed income: U.S. Treasury and agencies 9 59 — — 68 State and municipal debt — 134 — — 134 Corporate debt — 43 — — 43 Other 256 60 — 131 447 Fixed income subtotal 265 296 — — 131 692 Hedge funds — — — 445 445 Real estate — — — 117 117 Private credit — — — 107 107 Other postretirement benefit plan assets subtotal $ 836 $ 298 $ — $ 1,444 $ 2,578 Total pension and other postretirement benefit plan assets (c) $ 5,313 $ 4,535 $ 208 $ 9,341 $ 19,397 At December 31, 2015(a) Level 1 Level 2 Level 3 Not subject to leveling Total Pension plan assets Cash equivalents $ 210 $ — $ — $ — $ 210 Equities (b) 3,571 — 2 1,462 5,035 Fixed income: U.S. Treasury and agencies 1,001 79 — — 1,080 State and municipal debt — 61 — — 61 Corporate debt — 2,901 165 — 3,066 Other (b) — 146 — 452 598 Fixed income subtotal 1,001 3,187 165 452 4,805 Private equity — — — 924 924 Hedge funds — — — 1,924 1,924 Real estate — — — 725 725 Private credit — — — 699 699 Pension plan assets subtotal $ 4,782 $ 3,187 $ 167 $ 6,186 $ 14,322 At December 31, 2015(a) Level 1 Level 2 Level 3 Not subject to leveling Total Other postretirement benefit plan assets Cash equivalents $ 15 $ — $ — $ — $ 15 Equities 510 2 — 480 992 Fixed income: U.S. Treasury and agencies 11 53 — — 64 State and municipal debt — 131 — — 131 Corporate debt — 44 — — 44 Other 155 59 — 146 360 Fixed income subtotal 166 287 — 146 599 Hedge funds — — — 451 451 Real estate — — — 131 131 Private credit — — — 103 103 Other postretirement benefit plan assets subtotal $ 691 $ 289 $ — $ 1,311 $ 2,291 Total pension and other postretirement benefit plan assets (c) $ 5,473 $ 3,476 $ 167 $ 7,497 $ 16,613 Predecessor December 31, 2015(a) PHI Level 1 Level 2 Level 3 Not subject to leveling Total Pension plan assets Cash equivalents $ 50 $ — $ — $ — $ 50 Equities 335 — — 224 559 Fixed income: U.S. Treasury and agencies 114 15 — — 129 State and municipal debt — 18 — — 18 Corporate debt securities — 625 — — 625 Other — 40 — 504 544 Fixed income subtotal 114 698 — 504 1,316 Private equity — — — 38 38 Real estate — — — 46 46 Pension plan assets subtotal $ 499 $ 698 $ — $ 812 $ 2,009 Predecessor December 31, 2015(a) PHI Level 1 Level 2 Level 3 Not subject to leveling Total Other postretirement benefit plan assets Cash equivalents $ 8 $ — $ — $ — $ 8 Equities 197 — — 22 219 Fixed income - other 121 — — — 121 Other postretirement benefit plan assets subtotal $ 326 $ — $ — $ 22 $ 348 Total pension and other postretirement benefit plan assets (e) $ 825 $ 698 $ — $ 834 $ 2,357 ____________________ (a) See Note 12 — Fair Value of Financial Assets and Liabilities for a description of levels within the fair value hierarchy. (b) Includes derivative instruments of $1 million and $5 million , which have a total notional amount of $2,918 million and $1,774 million at December 31, 2016 and 2015 , respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the fiscal years ended and do not represent the amount of the company’s exposure to credit or market loss. (c) Excludes net liabilities of $28 million and net assets of $27 million at December 31, 2016 and 2015 , respectively, which are required to reconcile to the fair value of net plan assets. These items consist primarily of receivables related to pending securities sales, interest and dividends receivable, and payables related to pending securities purchases. (d) Effective March 23, 2016, Exelon became sponsor of PHI's defined benefit pension and other postretirement benefit plans, and assumed PHI's benefit plan obligations and related assets. (e) Excludes net assets of $9 million at December 31, 2015 , which are required to reconcile to the fair value of net plan assets. These items consist primarily of receivables related to pending securities sales, interest and dividends receivable, and payables related to pending securities purchased.
Defined Benefit Plan Fair Value Of Plan Assets Unobservable Input Reconciliation	rchases. (d) Effective March 23, 2016, Exelon became sponsor of PHI's defined benefit pension and other postretirement benefit plans, and assumed PHI's benefit plan obligations and related assets. (e) Excludes net assets of $9 million at December 31, 2015 , which are required to reconcile to the fair value of net plan assets. These items consist primarily of receivables related to pending securities sales, interest and dividends receivable, and payables related to pending securities purchased. The following table presents the reconciliation of Level 3 assets and liabilities measured at fair value for pension and other postretirement benefit plans for the years ended December 31, 2016 and 2015 : Exelon Fixed income Equities Total Pension Assets Balance as of January 1, 2016 $ 165 $ 2 $ 167 Actual return on plan assets: Relating to assets still held at the reporting date (2 ) — (2 ) Purchases, sales and settlements: Purchases 69 — 69 Sales (14 ) — (14 ) Settlements (a) (12 ) — (12 ) Balance as of December 31, 2016 $ 206 $ 2 $ 208 Fixed income Equities Total Pension Assets Balance as of January 1, 2015 $ 120 $ 2 $ 122 Actual return on plan assets: Relating to assets still held at the reporting date (8 ) — (8 ) Purchases, sales and settlements: Purchases 61 — 61 Settlements (a) (8 ) — (8 ) Balance as of December 31, 2015 $ 165 $ 2 $ 167 ________________________ (a) Represents cash settlements only.
Schedule Of Defined Contributions	n limits. The following table presents matching contributions to the savings plan for the years ended December 31, 2016 , 2015 and 2014 : For the Year Ended December 31, Exelon (a) Generation (a) ComEd PECO BGE BSC (b) Pepco (c) DPL (c) ACE PHISCO (c) 2016 $ 164 $ 79 $ 34 $ 10 $ 12 $ 19 $ 3 $ 2 $ 2 $ 6 2015 148 80 32 11 14 11 3 2 2 6 2014 103 51 26 8 8 10 3 2 1 6 Successor Predecessor PHI March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 Saving Plan Matching Contributions $ 10 $ 3 $ 14 $ 13 _________________________ (a) Includes $13 million , $9 million and $5 million related to CENG for the years ended December 31, 2016 , December 31, 2015 and for the period from April 1, 2014 to December 31, 2014, respectively. (b) These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These costs are not included in the Generation, ComEd, PECO, or BGE amounts above. (c) Pepco's, DPL's and PHISCO's matching contributions include $1 million , $1 million and $1 million , respectively, of costs incurred prior to the closing of Exelon's merger with PHI on March 23, 2016, which is not included in Exelon's matching contributions at December 31, 2016.

Severance (Tables)

Severance (Tables)	12 Months Ended
	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Schedule of Restructuring and Related Costs	For the Year Ended December 31, Acquisition, Integration and Financing Costs (a) 2016 2015 Exelon (b) $ 143 $ 87 Generation 37 24 ComEd (c) (6 ) 9 PECO 5 4 BGE (c) (1 ) 5 Pepco (c) 28 3 DPL (c) 20 2 ACE 19 1 Successor Predecessor Acquisition, Integration and Financing Costs (a) March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 PHI (c) $ 69 $ 29 $ 19 ______________ (a) The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statements of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. Costs do not include merger commitments discussed above. (b) Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps. (c) For the year ended December 31, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million , $6 million , $11 million , $4 million , and $16 million incurred at ComEd, BGE, Pepco, DPL and PHI, respectively, that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 3 - Regulatory Matters for more information. Successor Exelon Generation ComEd PECO BGE PHI Pepco (b) DPL (c) ACE Severance benefits (a) $ 57 $ 9 $ 2 $ 1 $ 1 $ 44 $ 21 $ 13 $ 10 ______________ (a) The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $8 million , $2 million , $1 million , $1 million , $20 million , $12 million and $10 million , respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the year ended December 31, 2016 . (b) Pepco established a regulatory asset of $11 million as of December 31, 2016 , primarily for severance benefit costs related to the PHI merger. (c) DPL established a regulatory asset of $4 million as of December 31, 2016 , primarily for severance benefit costs related to the PHI merger. and 2015 , the Registrants recorded the following severance costs associated with ongoing severance benefits within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income: Exelon Generation (a) ComEd (a) PECO (a) BGE (a) Year ended December 31, 2016 $ 19 $ 13 $ 3 $ 1 $ 1 2015 18 15 2 — 1 Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 PHI (a) Severance Benefits $ 1 $ — $ — _______ (a) The amounts above for Generation, ComEd, PECO, BGE and PHI include immaterial amounts billed by BSC for the years ended December 31, 2016 and 2015 . Amounts included in the table below represent the severance liability recorded for employees of each Registrant and exclude amounts included at Exelon and billed through intercompany allocations: Successor Severance Liability Exelon Generation ComEd PECO BGE PHI (b) Pepco DPL ACE Balance at December 31, 2014 $ 50 $ 34 $ 2 $ — $ 2 $ — $ 1 $ — $ — Severance charges 16 10 2 — — — — — — Payments (31 ) (21 ) (1 ) — (1 ) — (1 ) — — Balance at December 31, 2015 $ 35 $ 23 $ 3 $ — $ 1 $ — $ — $ — $ — Severance charges (a) 99 22 2 — — 56 1 1 — Payments (46 ) (9 ) (2 ) — (1 ) (27 ) (1 ) (1 ) — Balance at December 31, 2016 $ 88 $ 36 $ 3 $ — $ — $ 29 $ — $ — $ — Predecessor Severance Liability PHI (b) Balance at December 31, 2014 $ 3 Severance charges — Payments (3 ) Balance at December 31, 2015 $ — ______________ (a) Includes salary continuance and health and welfare severance benefits. Amounts primarily represent benefits provided for the PHI post-merger integration and the cost management program. (b) For PHI, the successor period includes activity for the period from March 24, 2016 through December 31, 2016 . The PHI predecessor periods include activity for the year ended December 31, 2015 and the period January 1, 2016 through March 23, 2016 . There was no activity in the 2016 PHI predecessor period. , the Registrants recorded the following severance costs related to the cost management program within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income, pursuant to the authoritative guidance for ongoing severance plans: Exelon Generation ComEd PECO BGE Severance benefits (a) $ 23 $ 18 $ 3 $ 1 $ 1 _______ (a) The amounts above for Generation, ComEd, PECO and BGE include $7 million , $3 million , $1 million , and $1 million , respectively, for amounts billed by BSC through intercompany allocations for the year ended December 31, 2016 .

Mezzanine Equity Contingently

Mezzanine Equity Contingently Redeemable Noncontrolling Interest (Table)	12 Months Ended
	Dec. 31, 2016
Noncontrolling Interest Disclosure [Abstract]
Noncontrolling Interest Disclosure [Text Block]	19 . Mezzanine Equity (Exelon, Generation and PHI) Contingently Redeemable Noncontrolling Interests (Exelon and Generation) In November 2015, 2015 ESA Investco, LLC, a wholly owned subsidiary of Generation, entered into an arrangement to sell a portion of its equity to a tax equity investor. Pursuant to the operating agreement, in certain circumstances the equity contributed by the noncontrolling interests holder could be contingently redeemable. These circumstances are outside of the control of Generation and the noncontrolling interests holder resulting in a portion of the noncontrolling interests being considered contingently redeemable and thus presented in mezzanine equity on the consolidated balance sheet. The following table summarizes the changes in the contingently redeemable noncontrolling interests for the years ended December 31, 2016 and 2015 : Contingently Redeemable NCI Balance at December 31, 2014 $ — Cash received from noncontrolling interests 32 Release of contingency (4 ) Balance at December 31, 2015 $ 28 Cash received from noncontrolling interests 129 Release of contingency (157 ) Balance at December 31, 2016 $ — Preferred Stock (PHI) In connection with the PHI Merger Agreement, Exelon purchased 18,000 originally issued shares of PHI preferred stock for a purchase price of $180 million . PHI excluded the preferred stock from equity at December 31, 2015 since the preferred stock contained conditions for redemption that were not solely within the control of PHI. Management determined that the preferred stock contained embedded features requiring separate accounting consideration to reflect the potential value to PHI that any issued and outstanding preferred stock could be called and redeemed at a nominal par value upon a termination of the merger agreement under certain circumstances due to the failure to obtain required regulatory approvals. The embedded call and redemption features on the shares of the preferred stock in the event of such a termination were separately accounted for as derivatives. As of December 31, 2015, the fair value of the derivative related to the preferred stock was estimated to be $18 million based on PHI’s updated assessment and was included in current assets with a corresponding increase in preferred stock on the Consolidated Balance Sheet. Immediately prior to the merger date, PHI updated its assessment of the fair value of the derivative and reduced the fair value to zero, recording the $18 million decrease in fair value as a reduction of Other, within PHI's predecessor period, January 1, 2016 to March 23, 2016 , Statements of Operations and Comprehensive Income. On March 23, 2016 , the preferred stock was cancelled and the $180 million cash consideration previously received by PHI to issue the preferred stock was treated as additional merger purchase price consideration.
Redeemable Noncontrolling Interest [Table Text Block]	The following table summarizes the changes in the contingently redeemable noncontrolling interests for the years ended December 31, 2016 and 2015 : Contingently Redeemable NCI Balance at December 31, 2014 $ — Cash received from noncontrolling interests 32 Release of contingency (4 ) Balance at December 31, 2015 $ 28 Cash received from noncontrolling interests 129 Release of contingency (157 ) Balance at December 31, 2016 $ —

Shareholder Equity Shareholder

Shareholder Equity Shareholder Equity (Tables)	12 Months Ended
	Dec. 31, 2016
Shareholder [Abstract]
Schedule of Common Stock Outstanding Roll Forward [Table Text Block]	The following table presents common stock authorized and outstanding as of December 31, 2016 and 2015 : December 31, 2016 2015 Par Value Shares Authorized Shares Outstanding Common Stock Exelon no par value 2,000,000,000 924,035,059 919,924,742 ComEd $ 12.50 250,000,000 127,017,157 127,016,973 PECO no par value 500,000,000 170,478,507 170,478,507 BGE no par value 175,000,000 1,000 1,000 PHI Predecessor $ 0.01 400,000,000 n/a 254,289,261 Pepco $ 0.01 200,000,000 100 100 DPL $ 2.25 1,000 1,000 1,000 ACE $ 3.00 25,000,000 8,546,017 8,546,017
Schedule of Auction Market Preferred Securities by Stock Series [Table Text Block]	December 31, Redemption (a) 2016 2015 2016 2015 Shares Outstanding Dollar Amount Series (without mandatory redemption) 7.125%, 1993 Series $ 100.00 — 400,000 $ — $ 40 6.97%, 1993 Series 100.00 — 500,000 — 50 6.70%, 1993 Series 100.00 — 400,000 — 40 6.99%, 1995 Series 100.00 — 600,000 — 60 Total preference stock — 1,900,000 $ — $ 190 ______________________ (a) Redeemable, at the option of BGE, at the indicated dollar amounts per share, plus accrued and unpaid dividends.

Stock-Based Compensation Plan58

Stock-Based Compensation Plans (All Registrants) (Tables)	12 Months Ended
	Dec. 31, 2016
Common Stock [Abstract]
Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block]	The following tables present the stock-based compensation expense included in Exelon's and PHI’s Consolidated Statements of Operations and Comprehensive Income for the years ended December 31, 2016 , 2015 and 2014 , as well as for the PHI predecessor period January 1, 2016 to March 23, 2016 : Exelon Year Ended December 31, Components of Stock-Based Compensation Expense 2016(a) 2015 2014 Performance share awards $ 93 $ 41 $ 59 Restricted stock units 75 71 61 Stock options — 1 2 Other stock-based awards 7 6 5 Total stock-based compensation expense included in operating and maintenance expense 175 119 127 Income tax benefit (68 ) (46 ) (47 ) Total after-tax stock-based compensation expense $ 107 $ 73 $ 80 ____________________ (a) 2016 amounts include expense related to stock-based compensation granted to eligible PHI employees since the merger date of March 23, 2016 . PHI Predecessor January 1 to March 23, Years Ended December 31, Components of Stock-Based Compensation Expense 2016 2015 2014 Time-based restricted stock units $ 2 $ 7 $ 5 Performance-based restricted stock units 1 5 8 Time-based restricted stock awards — 1 5 Total stock-based compensation expense included in operating and maintenance expense 3 13 18 Income tax benefit (1 ) (5 ) (7 ) Total after-tax stock-based compensation expense $ 2 $ 8 $ 11
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]	The following tables present the Registrants' stock-based compensation expense (pre-tax) for the years ended December 31, 2016 , 2015 and 2014 , as well as for the PHI predecessor period January 1, 2016 to March 23, 2016 : Years Ended December 31, Subsidiaries 2016 2015 2014 Exelon $ 175 $ 119 $ 127 Generation 78 64 52 ComEd 8 6 7 PECO 3 3 3 BGE 1 3 5 BSC (a) 81 43 60 PHI (a)(b) 7 13 18 Successor Predecessor March 24 to January 1 to Years Ended 2016 2016 2015 2014 PHI $ 4 $ 3 $ 13 $ 18 ____________________ (a) These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO, BGE or PHI amounts above. (b) Pepco's, DPL's and ACE's stock-based compensation expense for the year ended December 31, 2016 and for the period January 1, 2016 through March 23, 2016 was not material. PHI's stock-based compensation expense for the year ended December 31, 2016 includes $3 million of costs incurred prior to the closing of Exelon’s merger with PHI on March 23, 2016 .
Stock Based Compensation Tax Benefit	The following tables present information regarding Exelon’s and PHI's tax benefits for the years ended December 31, 2016 , 2015 and 2014 and PHI's predecessor period January 1, 2016 to March 23, 2016 : Exelon Years Ended December 31, 2016 2015 2014 Realized tax benefit when exercised/distributed: Restricted stock units $ 27 $ 30 $ 17 Performance share awards 18 18 11 PHI Predecessor January 1 to Years Ended December 31, 2016 2015 2014 Realized tax benefit when exercised/distributed: Time-based restricted stock units $ — $ 2 $ 3 Performance-based restricted stock units — 5 4 Time-based restricted stock awards — — 1
Schedule of Assumptions Used
Schedule of Share-based Compensation, Stock Options, Activity	The following table presents information with respect to stock option activity for the year ended December 31, 2016 : Shares Weighted Average Exercise Price (per share) Weighted Average Remaining Contractual Life (years) Aggregate Intrinsic Value Balance of shares outstanding at December 31, 2015 15,572,757 $ 46.68 Options exercised (840,672 ) 22.12 Options forfeited — — Options expired (2,200,494 ) 58.60 Balance of shares outstanding at December 31, 2016 12,531,591 $ 46.23 3.50 $ 13 Exercisable at December 31, 2016 (a) 12,531,591 $ 46.23 3.50 $ 13 ____________________ (a) Includes stock options issued to retirement eligible employees.
Stock Options Exercised	The following table summarizes additional information regarding stock options exercised for the years ended December 31, 2016 , 2015 and 2014 : Years Ended December 31, 2016 2015 2014 Intrinsic value (a) $ 11 $ — $ 3 Cash received for exercise price 19 — 7 ______________________ (a) The difference between the market value on the date of exercise and the option exercise price.
Schedule of Nonvested Share Activity	The following table summarizes Exelon’s nonvested stock option activity for the year ended December 31, 2016 : Shares Weighted Average Exercise Price (per share) Nonvested at December 31, 2015 (a) 82,250 $ 39.81 Vested (82,250 ) 39.81 Nonvested at December 31, 2016 (a) — $ — _____________________ (a) Excludes 279,000 of stock options issued to retirement-eligible employees as of December 31, 2015 as they are fully vested.
Schedule of Nonvested Restricted Stock Units Activity	The following tables summarize Exelon’s and PHI's nonvested restricted stock unit activity for the year ended December 31, 2016 and PHI's for the predecessor period January 1, 2016 to March 23, 2016 : Exelon Shares Weighted Average Grant Date Fair Value (per share) Nonvested at December 31, 2015 (a) 3,563,254 $ 32.92 Granted 3,042,184 28.14 Vested (1,797,536 ) 32.44 Forfeited (85,940 ) 30.08 Undistributed vested awards (b) (897,546 ) 28.35 Nonvested at December 31, 2016 (a)(c) 3,824,416 $ 30.49 PHI Time-based Shares Weighted Average Grant Date Fair Value (per share) Performance-based Shares Weighted Average Nonvested at December 31, 2015 628,514 $ 24.71 $ 408,638 $ 18.56 Granted 152,928 26.01 305,856 25.41 Vested — — (4,950 ) 26.08 Forfeited — — (1,238 ) 26.08 Nonvested at March 23, 2016 781,442 $ 24.96 $ 708,306 $ 21.45 ______________________ (a) Excludes 1,319,372 and 975,116 of restricted stock units issued to retirement-eligible employees as of December 31, 2016 and 2015 , respectively, as they are fully vested. (b) Represents restricted stock units that vested but were not distributed to retirement-eligible employees during 2016 .
Schedule of Nonvested Performance-based Units Activity	The following tables summarize Exelon’s and PHI's nonvested performance share awards activity for the year ended December 31, 2016 and PHI's for the predecessor period January 1, 2016 to March 23, 2016 : Exelon Shares (c) Weighted Average Grant Date Fair Value (per share) Nonvested at December 31, 2015 (a) 2,557,159 $ 31.88 Granted 2,319,407 28.85 Change in performance 627,303 30.04 Vested (949,315 ) 31.31 Forfeited (70,876 ) 30.90 Undistributed vested awards (b) (1,367,417 ) 28.33 Nonvested at December 31, 2016 (a) 3,116,261 $ 30.77 PHI Time-based Shares Weighted Average Grant Date Fair Value (per share) Performance-based Shares Weighted Average Nonvested at December 31, 2015 54,165 $ 26.80 24,717 $ 26.10 Vested — — (24,717 ) 26.10 Nonvested at March 23, 2016 54,165 $ 26.80 — $ — ________________ (a) Excludes 2,443,409 and 1,817,883 of performance share awards issued to retirement-eligible employees as of December 31, 2016 and 2015 , respectively, as they are fully vested. (b) Represents performance share awards that vested but were not distributed to retirement-eligible employees during 2016 .
Not Settled Performance Share Awards Balance Sheet Presentation	The following table presents the balance sheet classification of obligations related to outstanding performance share awards not yet settled: December 31, 2016 2015 (c) Current liabilities (a) $ 49 $ 28 Deferred credits and other liabilities (b) 52 32 Common stock 40 35 Total $ 141 $ 95 __________________________ (a) Represents the current liability related to performance share awards expected to be settled in cash. (b) Represents the long-term liability related to performance share awards expected to be settled in cash. (c) Excludes $8 million of common stock for PHI at December 31, 2015 .

Earnings Per Share and Equity59

Earnings Per Share and Equity (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Reconciliation of basic and diluted earnings per share	The following table sets forth the components of basic and diluted earnings per share and shows the effect of the stock options, performance share awards and restricted stock on the weighted average number of shares outstanding used in calculating diluted earnings per share: Years Ended December 31, 2016 2015 2014 Net income attributable to common shareholders $ 1,134 $ 2,269 $ 1,623 Weighted average common shares outstanding—basic 924 890 860 Assumed exercise and/or distributions of stock-based awards 3 3 4 Weighted average common shares outstanding—diluted 927 893 864

Changes in Accumulated Other 60

Changes in Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Schedule Of Accumulated Other Comprehensive Income (Loss)	The following tables present changes in accumulated other comprehensive income (loss) (AOCI) by component for the years ended December 31, 2016 and 2015 : For the Year Ended December 31, 2016 Gains and (Losses) on Cash Flow Hedges Unrealized Pension and Gains and (Losses) on Foreign AOCI of Equity Investments Total Exelon (a) Beginning balance $ (19 ) $ 3 $ (2,565 ) $ (40 ) $ (3 ) $ (2,624 ) OCI before reclassifications (6 ) 1 (182 ) 5 (4 ) (186 ) Amounts reclassified from AOCI (b) 8 — 137 5 — 150 Net current-period OCI 2 1 (45 ) 10 (4 ) (36 ) Ending balance $ (17 ) $ 4 $ (2,610 ) $ (30 ) $ (7 ) $ (2,660 ) Generation (a) Beginning balance $ (21 ) $ 1 $ — $ (40 ) $ (3 ) $ (63 ) OCI before reclassifications (6 ) 1 — 5 (4 ) (4 ) Amounts reclassified from AOCI (b) 8 — — 5 — 13 Net current-period OCI 2 1 — 10 (4 ) 9 Ending balance $ (19 ) $ 2 $ — $ (30 ) $ (7 ) $ (54 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 PHI Predecessor (a) Beginning balance January 1, 2016 $ (8 ) $ — $ (28 ) $ — $ — $ (36 ) OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — 1 — — 1 Net current-period OCI — — 1 — — 1 Ending balance March 23, 2016 (c) $ (8 ) $ — $ (27 ) $ — $ — $ (35 ) For the Year Ended December 31, 2015 Gains and Unrealized Pension and Gains and (Losses) on Foreign AOCI of Total Exelon (a) Beginning balance $ (28 ) $ 3 $ (2,640 ) $ (19 ) $ — $ (2,684 ) OCI before reclassifications (12 ) — (100 ) (21 ) (3 ) (136 ) Amounts reclassified from AOCI (b) 21 — 175 — — 196 Net current-period OCI 9 — 75 (21 ) (3 ) 60 Ending balance $ (19 ) $ 3 $ (2,565 ) $ (40 ) $ (3 ) $ (2,624 ) Generation (a) Beginning balance $ (18 ) $ 1 $ — $ (19 ) $ — (36 ) OCI before reclassifications (8 ) — — (21 ) (3 ) (32 ) Amounts reclassified from AOCI (b) 5 — — — — 5 Net current-period OCI (3 ) — — (21 ) (3 ) (27 ) Ending balance $ (21 ) $ 1 $ — $ (40 ) $ (3 ) $ (63 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 PHI Predecessor (a) Beginning balance $ (9 ) $ — $ (37 ) $ — $ — $ (46 ) OCI before reclassifications — — 5 — — 5 Amounts reclassified from AOCI (b) 1 — 4 — — 5 Net current-period OCI 1 — 9 — — 10 Ending balance $ (8 ) $ — $ (28 ) $ — $ — $ (36 ) _______________________ (a) All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in accumulated other comprehensive income. (b) See next tables for details about these reclassifications.
Reclassification Out Of Accumulated Other Comprehensive Income	The following tables present amounts reclassified out of AOCI to Net income for Exelon, Generation and PHI during the years ended December 31, 2016 and 2015 : For the Year Ended December 31, 2016 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Predecessor January 1, 2016 to March 23, 2016 Exelon Generation PHI Gains and (losses) on cash flow hedges Other cash flow hedges $ (13 ) $ (13 ) $ — Interest expense Total before tax (13 ) (13 ) — Tax benefit 5 5 — Net of tax $ (8 ) $ (8 ) $ — Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 78 $ — $ — Actuarial losses (b) (302 ) — (1 ) Total before tax (224 ) — (1 ) Tax benefit 87 — — Net of tax $ (137 ) $ — $ (1 ) Gains and (losses) of FX Gains $ (5 ) $ (5 ) $ — Other — — — Total before tax (5 ) (5 ) — Tax benefit — — — Net of tax $ (5 ) $ (5 ) $ — Total Reclassifications $ (150 ) $ (13 ) $ (1 ) Comprehensive income For the Year Ended December 31, 2015 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Predecessor Exelon Generation PHI Gains and (losses) on cash flow hedges Terminated interest rate swaps $ (26 ) $ — $ — Other, net Energy related hedges 2 2 — Operating revenues Other cash flow hedges (11 ) (11 ) (1 ) Interest expense Total before tax (35 ) (9 ) (1 ) Tax benefit 14 4 — Net of tax $ (21 ) $ (5 ) $ (1 ) Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 74 $ — $ — Actuarial losses (b) (361 ) — (6 ) Total before tax (287 ) — (6 ) Tax benefit 112 — 2 Net of tax $ (175 ) $ — $ (4 ) Total Reclassifications $ (196 ) $ (5 ) $ (5 ) Comprehensive income _____________________ (a) Amounts in parenthesis represent a decrease in net income. (b) This accumulated other comprehensive income component is included in the computation of net periodic pension and OPEB cost (see Note 17 — Retirement Benefits for additional details). (c) Amortization of the deferred compensation unit plan is allocated to capital and operating and maintenance expense.
Schedule of Components of Income Tax Expense (Benefit)	The following table presents income tax expense (benefit) allocated to each component of other comprehensive income (loss) during the years ended December 31, 2016 and 2015 : For the Years Ended December 31, 2016 2015 2014 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 30 $ 30 $ 19 Actuarial loss reclassified to periodic cost (118 ) (140 ) (93 ) Pension and non-pension postretirement benefit plan valuation adjustment 115 62 317 Change in unrealized (gain) loss on cash flow hedges — (6 ) 96 Change in unrealized (gain) loss on equity investments 3 1 73 Total $ 30 $ (53 ) $ 412 Generation Change in unrealized loss on cash flow hedges $ (2 ) $ 2 $ 84 Change in unrealized (gain) loss on equity investments 3 1 73 Total $ 1 $ 3 $ 157 Predecessor January 1 to For the Years Ended December 31, PHI 2016 2015 2014 Pension and non-pension postretirement benefit plans: Actuarial loss reclassified to periodic cost $ — $ 6 $ 5

Commitments and Contingencies61

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies [Line Items]
Schedule of Government Settlement Agreements [Table Text Block]	As of December 31, 2016, and 2015, the amount of SNF storage costs for which reimbursement has been or will be requested from the DOE under the DOE settlement agreements is as follows: December 31, 2016 December 31, 2015 DOE receivable - current (a) $ 109 $ 76 DOE receivable - noncurrent (b) 15 14 Amounts owed to co-owners (a)(c) (13 ) (5 ) _____________________________ (a) Recorded in Accounts receivable, other. (b) Recorded in Deferred debits and other assets, other (c) Non-CENG amounts owed to co-owners are recorded in Accounts receivable, other. CENG amounts owed to co-owners are recorded in Accounts payable. Represents amounts owed to the co-owners of Peach Bottom, Quad Cities, and Nine Mile Point Unit 2 generating facilities.
Commercial Commitments	Exelon’s commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 1,614 $ 1,355 $ 246 $ — $ 13 $ — $ — Surety bonds (b) 1,035 978 33 2 16 6 — Financing trust guarantees (c) 628 — — — — — 628 Guaranteed lease residual values (d) 20 — — — — — 20 Total commercial commitments $ 3,297 $ 2,333 $ 279 $ 2 $ 29 $ 6 $ 648 ___________________________ (a) Letters of credit (non-debt)—Exelon and certain of its subsidiaries maintain non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (c) Includes $ 200 million of Trust Preferred Securities of ComEd Financing III, $ 178 million of Trust Preferred Securities of PECO Trust III and IV and $ 250 million of Trust Preferred Securities of BGE Capital Trust II. (d) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $50 million , $14 million of which is a guarantee by Pepco, $17 million by DPL and $13 million by ACE. The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote.
Other Commitments	As of December 31, 2016 , Generation’s estimated commitment relating to its equity purchase agreements, including in-kind services contributions, is anticipated to be as follows: Total 2017 $ 34 2018 5 Total $ 39
Operating Leases Of Lessee Disclosure	Minimum future operating lease payments, including lease payments for contracted generation, vehicles, real estate, computers, rail cars, operating equipment and office equipment, as of December 31, 2016 were: Exelon (a) Generation (a) ComEd (b) PECO (b) BGE (b)(c)(d) PHI Pepco DPL (b) ACE 2017 $ 183 $ 70 $ 11 $ 3 $ 32 $ 50 $ 7 $ 13 $ 8 2018 179 75 6 3 34 49 6 17 8 2019 123 30 6 4 34 36 5 7 7 2020 140 48 3 4 34 38 4 10 6 2021 133 47 3 4 32 34 3 9 5 Remaining years 968 644 — — 33 211 7 54 20 Total minimum future lease payments $ 1,726 $ 914 $ 29 $ 18 $ 199 $ 418 $ 32 $ 110 $ 54 ______________________ (a) Excludes Generation’s contingent operating lease payments associated with contracted generation agreements. (b) Amounts related to certain real estate leases and railroad licenses effectively have indefinite payment periods. As a result, ComEd, PECO, BGE and DPL have excluded these payments from the remaining years, as such amounts would not be meaningful. ComEd’s, PECO’s, BGE’s and DPL's average annual obligation for these arrangements, included in each of the years 2017—2021, was $ 2 million , $ 4 million , $ 2 million and $2 million , respectively. (c) Includes all future lease payments on a 99 year real estate lease that expires in 2106 . (d) The BGE column above includes minimum future lease payments associated with a 6-year lease for the Baltimore City conduit system that became effective during the fourth quarter of 2016. BGE's total commitments under the lease agreement are $ 21 million $ 25 million , $ 26 million , $ 27 million , $ 28 million , and $ 14 million related to years 2017, 2018, 2019, 2020, 2021 and thereafter, respectively.
Operating Leases Rent Expense	The following table presents the Registrants’ rental expense under operating leases for the years ended December 31, 2016, 2015 and 2014: For the Year Ended December 31, Exelon Generation (a) ComEd PECO BGE Pepco DPL ACE 2016 $ 777 $ 667 $ 15 $ 7 $ 22 $ 8 $ 15 $ 13 2015 922 851 12 9 32 7 14 13 2014 865 806 15 14 12 8 14 12 Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014 PHI Rental expense under operating leases $ 49 12 60 59 ________________________ (a) Includes contingent operating lease payments associated with contracted generation agreements that are not included in the minimum future operating lease payments table above. Payments made under Generation’s contracted generation lease agreements totaled $604 million , $798 million and $755 million during 2016 , 2015 and 2014 , respectively. Excludes contract amortization associated with purchase accounting and contract acquisitions.
Accrued environmental liabilities	As of December 31, 2016 and 2015, the Registrants had accrued the following undiscounted amounts for environmental liabilities in Other current liabilities and Other deferred credits and other liabilities within their respective Consolidated Balance Sheets: December 31, 2016 Total environmental investigation and remediation reserve Portion of total related to MGP investigation and remediation (a) Exelon $ 429 $ 325 Generation 72 — ComEd 292 291 PECO 33 31 BGE (a) 2 2 PHI 30 1 Pepco 27 — DPL 2 1 ACE 1 — December 31, 2015 Total environmental investigation and remediation reserve Portion of total related to MGP investigation and remediation Exelon $ 369 $ 301 Generation 63 — ComEd 266 264 PECO 37 35 BGE 3 2 PHI (Predecessor) 33 1 Pepco 24 — DPL 3 1 ACE 1 —
Exelon Generation Co L L C [Member]
Commitments and Contingencies [Line Items]
Commercial Commitments	Generation’s commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 1,546 $ 1,287 $ 246 $ — $ 13 $ — $ — Surety bonds 945 918 27 — — — — Total commercial commitments $ 2,491 $ 2,205 $ 273 $ — $ 13 $ — $ — ________________________ (a) Letters of credit (non-debt)—Non-debt letters of credit maintained to provide credit support for certain transactions as requested by third parties.
Commonwealth Edison Co [Member]
Commitments and Contingencies [Line Items]
Commercial Commitments	ComEd’s commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 14 $ 14 $ — $ — $ — $ — $ — Surety bonds (b) 11 9 2 — — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 225 $ 23 $ 2 $ — $ — $ — $ 200 _________________________ (a) Letters of credit (non-debt)—ComEd maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.
PECO Energy Co [Member]
Commitments and Contingencies [Line Items]
Commercial Commitments	PECO’s commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 23 $ 23 $ — $ — $ — $ — $ — Surety bonds (b) 9 9 — — — — — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 210 $ 32 $ — $ — $ — $ — $ 178 ________________________ (a) Letters of credit (non-debt)—PECO maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.
Baltimore Gas and Electric Company [Member]
Commitments and Contingencies [Line Items]
Commercial Commitments	BGE’s commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 2 $ 2 $ — $ — $ — $ — $ — Surety bonds (b) 11 10 1 — — — — Financing trust guarantees 250 — — — — — 250 Total commercial commitments $ 263 $ 12 $ 1 $ — $ — $ — $ 250 ________________________ (a) Letters of credit (non-debt)—BGE maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.
Pepco Holdings LLC [Member]
Commitments and Contingencies [Line Items]
Commercial Commitments	PHI commercial commitments (Successor) as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 1 $ 1 $ — $ — $ — $ — $ — Surety bonds (b) 16 14 2 — — — — Guaranteed lease residual values (c) 20 — — — — — 20 Total commercial commitments $ 37 $ 15 $ 2 $ — $ — $ — $ 20 ________________________ (a) Letters of credit (non-debt)—PHI and certain of its subsidiaries maintain non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (c) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $50 million . The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote.
Potomac Electric Power Company [Member]
Commitments and Contingencies [Line Items]
Commercial Commitments	Pepco commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Surety bonds (a) 9 9 — — — — — Guaranteed lease residual values (b) 6 — — — — — 6 Total commercial commitments $ 15 $ 9 $ — $ — $ — $ — $ 6 ________________________
Delmarva Power and Light Company [Member]
Commitments and Contingencies [Line Items]
Commercial Commitments	DPL commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Surety bonds (a) 4 3 1 — — — — Guaranteed lease residual values (b) 7 — — — — — 7 Total commercial commitments $ 11 $ 3 $ 1 $ — $ — $ — $ 7 ________________________
Atlantic City Electric Company [Member]
Commitments and Contingencies [Line Items]
Commercial Commitments	ACE commercial commitments as of December 31, 2016 , representing commitments potentially triggered by future events, were as follows: Expiration within Total 2017 2018 2019 2020 2021 2022 and beyond Letters of credit (non-debt) (a) $ 1 $ 1 $ — $ — $ — $ — $ — Surety bonds (b) 3 2 1 — — — — Guaranteed lease residual values (c) 5 — — — — — 5 Total commercial commitments $ 9 $ 3 $ 1 $ — $ — $ — $ 5 ________________________ (a) Letters of credit (non-debt)—ACE maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties. (b) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (c) R epresents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The maximum lease term associated with these assets ranges from 3 to 8 years. The maximum potential obligation at the end of the minimum lease term would be $ 13 million . The minimum lease term associated with these assets ranges from 1 to 4 years. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote.

Supplemental Financial Inform62

Supplemental Financial Information (Tables)	12 Months Ended
	Dec. 31, 2016
Supplemental Financial Information [Abstract]
Components of taxes other than income	The following tables provide additional information about the Registrants’ Consolidated Statements of Operations and Comprehensive Income for the years ended December 31, 2016 , 2015 and 2014 . Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the year ended December 31, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Taxes other than income Utility (a) $ 753 $ 122 $ 242 $ 136 $ 85 $ 312 $ 18 $ — $ 253 $ 78 Property 483 246 27 13 123 53 31 3 73 18 Payroll 226 117 28 15 17 8 5 3 23 8 Other 114 21 (4 ) — 4 4 1 1 5 1 Total taxes other than income $ 1,576 $ 506 $ 293 $ 164 $ 229 $ 377 $ 55 $ 7 $ 354 $ 105 Predecessor For the year ended December 31, 2015 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Taxes other than income Utility (a) $ 474 $ 105 $ 236 $ 133 $ 85 $ 326 $ 308 $ 18 $ — Property 407 250 27 11 119 94 57 28 3 Payroll 201 118 28 14 16 27 6 4 2 Other 118 16 5 2 4 8 5 1 2 Total taxes other than income $ 1,200 $ 489 $ 296 $ 160 $ 224 $ 455 $ 376 $ 51 $ 7 Predecessor For the year ended December 31, 2014 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Taxes other than income Utility (a) $ 456 $ 89 $ 238 $ 128 $ 86 $ 324 $ 307 $ 17 $ — Property 396 240 25 15 114 85 51 24 3 Payroll 200 118 28 14 18 23 6 4 2 Other 102 18 2 2 3 5 5 1 (1 ) Total taxes other than income $ 1,154 $ 465 $ 293 $ 159 $ 221 $ 437 $ 369 $ 46 $ 4 _____________________ (a) Generation’s utility tax represents gross receipts tax related to its retail operations and ComEd’s, PECO’s, BGE’s, Pepco's, DPL's and ACE's utility taxes represent municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
Components of non-operating income and expenses	Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the year ended December 31, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 237 $ 237 $ — $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 126 126 — — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 216 216 — — — — — — — — Non-regulatory agreement units 194 194 — — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (1 ) (1 ) — — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (372 ) (372 ) — — — — — — — — Total decommissioning-related activities 400 400 — — — — — — — — Investment income (loss) 17 8 — (1 ) 2 (f) 1 — 1 1 — Long-term lease income 4 — — — — — — — — — Interest income related to uncertain income tax positions 13 — — — — 1 — — (1 ) — Penalty related to uncertain income tax positions (c) (106 ) — (86 ) — — — — — — — AFUDC—Equity 64 — 14 8 19 19 5 6 23 7 Loss on debt extinguishment (3 ) (2 ) — — — — — — — — Other 24 (5 ) 7 1 — 15 8 2 21 (11 ) Other, net $ 413 $ 401 $ (65 ) $ 8 $ 21 $ 36 $ 13 $ 9 $ 44 $ (4 ) Predecessor For the year ended December 31, 2015 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 232 $ 232 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 156 156 — — — — — — — Net unrealized losses on decommissioning trust funds— Regulatory agreement units (282 ) (282 ) — — — — — — — Non-regulatory agreement units (197 ) (197 ) — — — — — — — Net unrealized gains on pledged assets Zion Station decommissioning 7 7 — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) 21 21 — — — — — — — Total decommissioning-related activities (63 ) (63 ) — — — — — — — Investment income (loss) 8 3 — (2 ) 4 (f) — — — — Long-term lease income 15 — — — — — — — — Interest income related to uncertain income tax positions 1 1 — — — 34 5 — — AFUDC—Equity 24 — 5 5 14 14 12 1 1 Terminated interest rate swaps (d) (26 ) — — — — — — — — PHI merger related debt exchange (e) (22 ) — — — — — — — — Other 17 (1 ) 16 2 — 40 11 9 2 Other, net $ (46 ) $ (60 ) $ 21 $ 5 $ 18 $ 88 $ 28 $ 10 $ 3 Predecessor For the year ended December 31, 2014 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 216 $ 216 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 159 159 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 180 180 — — — Non-regulatory agreement units 134 134 — — — — — — — Net unrealized gains on pledged assets Zion Station decommissioning 29 29 — — — — Regulatory offset to decommissioning trust fund-related activities (b) (358 ) (358 ) — — — — — — Total decommissioning-related activities 360 360 — — — — — — — Investment income (loss) 1 1 — (1 ) 7 (f) 1 — — — Long-term lease income 24 — — — — — — — — Interest income related to uncertain income tax positions 40 54 — — — — 1 — 1 AFUDC—Equity 21 — 3 6 12 13 10 2 1 Other 9 (9 ) 14 2 (1 ) 30 19 8 1 Other, net $ 455 $ 406 $ 17 $ 7 $ 18 $ 44 $ 30 $ 10 $ 3 _________________________ (a) Includes investment income and realized gains and losses on sales of investments within the nuclear decommissioning trust funds. (b) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of net income taxes related to all NDT fund activity for those units. See Note 16 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning. (c) See Note 15 — Income Taxes for discussion of the penalty related to the Tax Court’s decision on Exelon’s like-kind exchange tax position. (d) In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated certain floating-to-fixed interest rate swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from AOCI to Other, net in Exelon's Consolidated Statements of Operations and Comprehensive Income. (e) See Note 14 — Debt and Credit Agreements and Note 4 — Mergers, Acquisitions, and Dispositions for additional information on the PHI merger related debt exchange. (f) Relates to the cash return on BGE’s rate stabilization deferral. See Note 3 — Regulatory Matters for additional information regarding the rate stabilization deferral.
Components of depreciation, amortization and accretion, and other, net	The following tables provide additional information regarding the Registrants’ Consolidated Statements of Cash Flows for the years ended December 31, 2016 , 2015 and 2014 . Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the year ended December 31, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Depreciation, amortization and accretion Property, plant and equipment $ 3,477 $ 1,835 $ 708 $ 244 $ 299 $ 175 $ 110 $ 82 $ 325 $ 94 Regulatory assets 407 — 67 26 124 120 47 83 190 58 Amortization of intangible assets, net 52 44 — — — — — — — — Amortization of energy contract assets and liabilities (a) 35 35 — — — — — — — — Nuclear fuel (b) 1,159 1,159 — — — — — — — — ARO accretion (c) 446 446 — — — — — — — — Total depreciation, amortization and accretion $ 5,576 $ 3,519 $ 775 $ 270 $ 423 $ 295 $ 157 $ 165 $ 515 $ 152 Predecessor For the year ended December 31, 2015 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Depreciation, amortization and accretion Property, plant and equipment $ 2,227 $ 1,007 $ 635 $ 240 $ 289 $ 164 $ 103 $ 76 $ 392 Regulatory assets 170 — 72 20 77 92 45 99 232 Amortization of intangible assets, net 54 47 — — — — — — — Amortization of energy contract assets and liabilities (a) 22 22 — — — — — — — Nuclear fuel (b) 1,116 1,116 — — — — — — — ARO accretion (c) 398 397 — — — — — — — Total depreciation, amortization and accretion $ 3,987 $ 2,589 $ 707 $ 260 $ 366 $ 256 $ 148 $ 175 $ 624 Predecessor For the year ended December 31, 2014 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Depreciation, amortization and accretion Property, plant and equipment $ 2,080 $ 922 $ 588 $ 227 $ 288 $ 155 $ 94 $ 72 $ 363 Regulatory assets 191 — 99 9 83 57 28 83 163 Amortization of intangible assets, net 44 44 — — — — — — — Amortization of energy contract assets and liabilities (a) 135 135 — — — — — — — Nuclear fuel (b) 1,073 1,073 — — — — — — — ARO accretion (c) 345 345 — — — — — — — Total depreciation, amortization and accretion $ 3,868 $ 2,519 $ 687 $ 236 $ 371 $ 212 $ 122 $ 155 $ 526 ________________________ (a) Included in Operating revenues or Purchased power and fuel on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (b) Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
Schedule of Cash Flow, Supplemental Disclosure	Successor Predecessor March 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the year ended December 31, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Cash paid (refunded) during the year: Interest (net of amount capitalized) $ 1,340 $ 339 $ 298 $ 104 $ 92 $ 118 $ 47 $ 62 $ 209 $ 43 Income taxes (net of refunds) (441 ) 435 (444 ) 64 31 216 115 200 258 11 Pension and non-pension postretirement benefit costs $ 619 $ 218 $ 166 $ 33 $ 67 $ 31 $ 18 $ 15 $ 86 $ 23 Loss from equity method investments 24 25 — — — — — — — — Provision for uncollectible accounts 155 19 41 30 1 29 23 32 65 16 Provision for excess and obsolete inventory 12 6 4 — — 3 1 1 1 1 Stock-based compensation costs 111 — — — — — — — — 3 Other decommissioning-related activity (a) (384 ) (384 ) — — — — — — — — Energy-related options (b) (11 ) (11 ) — — — — — — — — Amortization of regulatory asset related to debt costs 9 — 4 1 — 2 1 1 3 1 Amortization of rate stabilization deferral 76 — — — 81 (12 ) 2 — (5 ) 5 Amortization of debt fair value adjustment (11 ) (11 ) — — — — — — — — Merger-related commitments (c)(d) 558 53 — — — 125 82 110 317 — Severance costs 99 22 — — — — — — 56 — Asset retirement costs 2 — — — — — 1 2 2 — Amortization of debt costs 35 17 4 3 1 — — — 1 — Discrete impacts from EIMA (e) 8 — 8 — — — — — — — Lower of cost or market inventory adjustment 37 36 — 1 — — — — — — Baltimore City Conduit Lease Settlement (28 ) — — — (28 ) — — — — — Cash Working Capital Order (13 ) — — — (13 ) — — — — — Other 35 25 (12 ) (3 ) (21 ) 5 (14 ) (6 ) (12 ) (3 ) Total other non-cash operating activities $ 1,333 $ 15 $ 215 $ 65 $ 88 $ 183 $ 114 $ 155 $ 514 $ 46 Non-cash investing and financing activities: Change in capital expenditures not paid $ (128 ) $ 50 $ (91 ) $ (11 ) $ (86 ) $ 27 $ (12 ) $ 11 $ 21 $ 11 Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash — 119 — — — — — — — — Fair value of net assets distributed to Exelon in connection with the PHI Merger, net of cash (c)(f) — — — — — — — — 127 — Fair value of pension obligation transferred in connection with the PHI Merger (c)(f) — — — — — — — — 53 — Assumption of member purchase liability — — — — — — — — 29 — Assumption of merger commitment liability — — — — — 33 — — 33 — Change in PPE related to ARO update 191 191 — — — — — — — — Non-cash financing of capital projects 95 95 — — — — — — — — Indemnification of like-kind exchange position (h) — — 158 — — — — — — — Sale of Upstream assets (c) 37 37 — — — — — — — — Pending FitzPatrick Acquisition (i) (54 ) (54 ) — — — — — — — — ____________________________ (a) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 16 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) See Note 4 - Mergers, Acquisitions, and Dispositions for more information. (d) Excludes $5 million of forgiveness of Accounts receivable related to merger commitments recorded in connection with the PHI Merger, the balance is included within Provision for uncollectible accounts. (e) Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate. See Note 3 — Regulatory Matters for more information. (f) Immediately following closing of the PHI Merger, the net assets associated with PHI’s unregulated business interests were distributed by PHI to Exelon. Exelon contributed a portion of such net assets to Generation. (g) Relates to the nuclear fuel procurement contract for the purchase of fixed quantities of converted uranium, which was delivered to Generation in 2015. Generation is required to make payments starting September 28, 2018, with the final payment being due no later than September 30, 2020. (h) See Note 15 — Income Taxes for discussion of the like-kind exchange tax position. (i) Reflects the transfer of nuclear fuel to Entergy under the cost reimbursement provisions of the FitzPatrick acquisition agreements. See Note 4 - Mergers, Acquisitions, and Dispositions for more information. Predecessor For the year ended December 31, 2015 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Cash paid (refunded) during the year: Interest (net of amount capitalized) $ 930 $ 348 $ 308 $ 94 $ 120 $ 116 $ 47 $ 63 $ 268 Income taxes (net of refunds) 342 476 (265 ) 64 73 (6 ) (5 ) — (13 ) Pension and non-pension postretirement benefit costs $ 637 $ 269 $ 206 $ 39 $ 65 $ 30 $ 15 $ 15 $ 97 Loss from equity method investments 7 8 — — — — — — — Provision for uncollectible accounts 120 22 53 30 15 21 20 20 61 Stock-based compensation costs 97 — — — — — — — 13 Other decommissioning-related activity (a) (82 ) (82 ) — — — — — — — Energy-related options (b) 21 21 — — — — — — — Amortization of regulatory asset related to debt costs 7 — 5 2 — 2 1 1 5 Amortization of rate stabilization deferral 73 — — — 73 1 (3 ) — (2 ) Amortization of debt fair value adjustment (17 ) (17 ) — — — — — — — Discrete impacts from EIMA (c) 144 — 144 — — — — — — Amortization of debt costs 58 15 4 2 2 — — — 2 Provision for excess and obsolete inventory 10 9 1 — — — — — 1 Lower of cost or market inventory adjustment 23 23 — — — — — — — Other 11 — 3 (3 ) (18 ) — — 1 (10 ) Total other non-cash operating activities $ 1,109 $ 268 $ 416 $ 70 $ 137 $ 54 $ 33 $ 37 $ 167 Non-cash investing and financing activities: Change in capital expenditures not paid $ 96 $ 82 $ 34 $ (13 ) $ (9 ) $ (1 ) $ 3 $ 3 $ 6 Nuclear fuel procurement (d) 57 57 — — — — — — — Change in PPE related to ARO update 885 885 — — — — — — — Indemnification of like-kind exchange position (e) — — 7 — — — — — — Non-cash financing of capital projects 77 77 — — — — — — — Long-term software licensing agreement (f) 95 — — — — — — — — ______________________ (a) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 16 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate. See Note 3 — Regulatory Matters for more information. (d) Relates to the nuclear fuel procurement contract for the purchase of fixed quantities of converted uranium, which was delivered to Generation in 2015. Generation is required to make payments starting September 28, 2018, with the final payment being due no later than September 30, 2020. (e) See Note 15 — Income Taxes for discussion of the like-kind exchange tax position. (f) Relates to a long-term software license agreement entered into on May 30, 2015. Exelon is required to make payments starting August of 2015 through May of 2024. See Note 14 — Debt and Credit Agreements for additional information. Predecessor For the year ended December 31, 2014 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI Cash paid (refunded) during the year: Interest (net of amount capitalized) $ 940 $ 322 $ 292 $ 94 $ 111 $ 111 $ 45 $ 61 $ 257 Income taxes (net of refunds) 314 227 (6 ) 85 (21 ) (58 ) (43 ) (3 ) (2 ) Pension and non-pension postretirement benefit costs $ 560 $ 249 $ 162 $ 36 $ 64 $ 22 $ 7 $ 13 $ 58 Loss from equity method investments 22 20 — — — — — — — Provision for uncollectible accounts 156 14 26 52 64 17 14 13 49 Provision for excess and obsolete inventory 5 5 — — — — — — — Stock-based compensation costs 91 — — — — — — — 18 Other decommissioning-related activity (a) (132 ) (132 ) — — — — — — — Energy-related options (b) 122 122 — — — — — — — Amortization of regulatory asset related to debt costs 11 — 8 3 — 3 2 — 5 Amortization of rate stabilization deferral 65 — — — 65 3 (1 ) — 2 Amortization of debt fair value adjustment (23 ) (23 ) — — — — — — — Merger-related commitments 44 44 — — — — — — — Discrete impacts from EIMA (c) 53 — 53 — — — — — — Amortization of debt costs 53 12 4 2 2 — — — 1 Lower of cost or market inventory adjustment 29 29 — — — — — — — Other (2 ) 6 2 (1 ) (15 ) (8 ) — — (6 ) Total other non-cash operating activities $ 1,054 $ 346 $ 255 $ 92 $ 180 $ 37 $ 22 $ 26 $ 127 Non-cash investing and financing activities: Change in PPE related to ARO update $ 72 $ 72 $ — $ — $ — $ — $ — $ — $ — Change in capital expenditures not paid 220 (61 ) (d) 78 — 25 10 8 9 28 Fair value of net assets recorded upon CENG consolidation (e) 3,400 3,400 — — — — — — — Issuance of equity units (f) 131 — — — — — — — — Nuclear fuel procurement (g) 70 70 — — — — — — — Indemnification of like-kind exchange position (h) — — 5 — — — — — — _________________________ (a) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 16 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate. See Note 3 — Regulatory Matters for more information. (d) Includes $170 million of changes in capital expenditures not paid between December 31, 2014 and 2013 related to Antelope Valley. (e) See Note 5 — Investment in Constellation Energy Nuclear Group, LLC for additional information. (f) Relates to the present value of the contract payments for the equity units issued by Exelon. See Note 21 — Stock-Based Compensation Plans for additional information. (g) Relates to the nuclear fuel procurement contracts for the purchase of fixed quantities of uranium, which was delivered to Generation in 2014. Generation is required to make payments starting June 30, 2016, with the final payment being due no later than June 30, 2018. (h) See Note 15 — Income Taxes for discussion of the like-kind exchange tax position.
Investments	The following tables provide additional information about assets and liabilities of the Registrants at December 31, 2016 and 2015 . Successor December 31, 2016 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Investments Equity method investments: Financing trusts (a) $ 22 $ — $ 6 $ 8 $ 8 $ — $ — $ — $ — Bloom 216 216 — — — — — — — Net Power 57 57 — — — — — — — Other equity method investments 16 15 — — — — — — — Total equity method investments 311 288 6 8 8 — — — — Other investments: Employee benefit trusts and investments (c) 232 44 — 17 4 133 102 — — Other cost method investments 52 52 — — — — — — — Other available for sale investments 34 34 — — — — — — — Total investments $ 629 $ 418 $ 6 $ 25 $ 12 $ 133 $ 102 $ — $ — Predecessor December 31, 2015 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Investments Equity method investments: Financing trusts (a) $ 22 $ — $ 6 $ 8 $ 8 $ — $ — $ — $ — Bloom 63 63 — — — — — — — Net Power 23 23 — — — — — — — Other equity method investments 4 3 — — — — — — — Total equity method investments 112 89 6 8 8 — — — — Other investments: Net investment in leases (b) 358 6 — — — — — — — Employee benefit trusts and investments(c) 85 31 — 20 4 80 68 — — Other cost method investments 55 55 — — — — — — — Other available for sale investments 29 29 — — — — — — — Total investments $ 639 $ 210 $ 6 $ 28 $ 12 $ 80 $ 68 $ — $ — _________________________ (a) Includes investments in affiliated financing trusts, which were not consolidated within the financial statements of Exelon and are shown as investments on the Consolidated Balance Sheets. See Note 1 — Significant Accounting Policies for additional information. (b) Represents direct financing lease investments. See Note 8 — Impairment of Long-Lived Assets for additional information. (c) The Registrants’ investments in these marketable securities are recorded at fair market value.
Accrued Liabilities Current	The following tables provide additional information about liabilities of the Registrants at December 31, 2016 and 2015 . Successor December 31, 2016 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Accrued expenses Compensation-related accruals (a) $ 1,199 $ 557 $ 199 $ 67 $ 64 $ 112 $ 30 $ 17 $ 11 Taxes accrued 723 239 330 4 78 65 48 4 9 Interest accrued 1,234 82 609 30 31 49 21 8 12 Severance accrued 44 15 2 — — 19 — — — Other accrued expenses 260 96 110 3 2 27 14 7 6 Total accrued expenses $ 3,460 $ 989 $ 1,250 $ 104 $ 175 $ 272 $ 113 $ 36 $ 38 Predecessor December 31, 2015 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Accrued expenses Compensation-related accruals (a) $ 1,014 $ 547 $ 183 $ 66 $ 57 $ 88 $ 26 $ 14 $ 8 Taxes accrued 293 186 63 4 23 77 56 3 23 Interest accrued 915 77 443 35 27 54 23 8 13 Severance accrued 21 11 3 — 1 — — — — Other accrued expenses 133 114 14 4 2 47 14 6 26 Total accrued expenses $ 2,376 $ 935 $ 706 $ 109 $ 110 $ 266 $ 119 $ 31 $ 70 _______________________ (a) Primarily includes accrued payroll, bonuses and other incentives, vacation and benefits.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Reconciliation of revenues from segments to consolidated	Generation total revenues net of purchased power and fuel expense: 2016 2015 2014 RNF from external (b) Intersegment Total RNF RNF from external (b) Intersegment RNF Total RNF RNF from external (b)(d) Intersegment (d) Total RNF Mid-Atlantic (a) $ 3,282 $ 35 $ 3,317 $ 3,556 $ 15 $ 3,571 $ 3,544 $ (113 ) $ 3,431 Midwest 2,969 2 2,971 2,912 (20 ) 2,892 2,607 (8 ) 2,599 New England 467 (29 ) 438 519 (58 ) 461 450 (99 ) 351 New York (a) 761 (19 ) 742 584 50 634 439 44 483 ERCOT 412 (131 ) 281 425 (132 ) 293 573 (256 ) 317 Other Power Regions 483 (147 ) 336 440 (190 ) 250 517 (190 ) 327 Total Revenues net of purchased power and fuel expense for Reportable Segments $ 8,374 $ (289 ) $ 8,085 $ 8,436 $ (335 ) $ 8,101 $ 8,130 $ (622 ) $ 7,508 Other (c) 547 289 836 678 335 1,013 (662 ) 622 (40 ) Total Generation Revenues net of purchased power and fuel expense $ 8,921 $ — $ 8,921 $ 9,114 $ — $ 9,114 $ 7,468 $ — $ 7,468 ____________________________ (a) On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, beginning on April 1, 2014, CENG's revenues net of purchased power and fuel expense are included on a fully consolidated basis. (b) Includes purchases and sales from third parties and affiliated sales to the Utility Registrants. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $57 million decrease in RNF, a $ 8 million increase in RNF, and a $ 124 million decrease in RNF for the amortization of intangible assets related to commodity contracts recorded at fair value for the years ended December 31, 2016 , 2015 , and 2014 , respectively, unrealized mark-to-market losses of $41 million , gains of $257 million , and losses of $591 million for the years ended December 31, 2016 , 2015 , and 2014 , respectively, accelerated nuclear fuel amortization associated with the initial early retirement decision for Clinton and Quad Cities as discussed in Note 9 - Early Nuclear Plant Retirements of $60 million for the year ended December 31, 2016, and the elimination of intersegment revenues net of purchased power and fuel expense. (d) Exelon corrected an error in the December 31, 2014 balances within Intersegment RNF and RNF from external customers for an understatement of $8 million of Intersegment RNF for Reportable Segments for the year ended December 31, 2014, an understatement of RNF from external customers for Reportable Segments of $11 million for the year ended December 31, 2014, an overstatement of $8 million of Intersegment RNF for Other for the year ended December 31, 2014, and an overstatement of RNF from external customers for Other of $11 million for the year ended December 31, 2014. This also included an understatement of total RNF for Reportable Segments and an overstatement of total RNF for Other of $19 million for the year ended December 31, 2014. The error is not considered material to any prior period, and there is no net impact to Generation Total RNF for 2014.
Analysis and reconciliation of reportable segment revenues for Generation	2016 2015 2014 Revenues from external customers (b) Intersegment revenues Total revenues Revenues from external customers (b) Intersegment revenues Total revenues Revenues from external customers (b)(d) Intersegment revenues (d) Total revenues Mid-Atlantic (a) $ 6,212 $ (33 ) $ 6,179 $ 5,974 $ (74 ) $ 5,900 $ 5,414 $ (155 ) $ 5,259 Midwest 4,402 10 4,412 4,712 (2 ) 4,710 4,488 (13 ) 4,475 New England 1,778 (9 ) 1,769 2,217 (5 ) 2,212 1,468 (46 ) 1,422 New York (a) 1,198 (42 ) 1,156 996 (11 ) 985 846 (3 ) 843 ERCOT 831 6 837 863 (6 ) 857 938 (3 ) 935 Other Power Regions 969 (62 ) 907 1,182 (80 ) 1,102 1,379 (70 ) 1,309 Total Revenues for Reportable Segments $ 15,390 $ (130 ) $ 15,260 $ 15,944 $ (178 ) $ 15,766 $ 14,533 $ (290 ) $ 14,243 Other (c) 2,361 130 2,491 3,191 178 3,369 2,860 290 3,150 Total Generation Consolidated Operating Revenues $ 17,751 $ — $ 17,751 $ 19,135 $ — $ 19,135 $ 17,393 $ — $ 17,393 _______________________ (a) On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, beginning on April 1, 2014, CENG's revenues are included on a fully consolidated basis. (b) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $52 million decrease to revenues, a $ 7 million increase to revenues, and a $ 289 million decrease to revenues for the amortization of intangible assets related to commodity contracts recorded at fair value for the years ended December 31, 2016 , 2015 , and 2014 , respectively, unrealized mark-to-market losses of $500 million , gains of $203 million , and losses of $174 million for the years ended December 31, 2016 , 2015 , and 2014 , respectively, and elimination of intersegment revenues. (d) Exelon corrected an error in the December 31, 2014 balances within Intersegment revenues and Revenues from external customers for an overstatement of Intersegment revenues for Reportable Segments of $284 million for the year ended December 31, 2014, an understatement of Revenues from external customers for Reportable Segments of $284 million for the year ended December 31, 2014, an understatement of Intersegment revenues for Other of $284 million for the year ended December 31, 2014, and an overstatement of Revenues from external customers for Other of $284 million for the year ended December 31, 2014. The error is not considered material to any prior period, and there is no net impact to Total Revenues.
Analysis and reconciliation of reportable segment information	An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements for the years ended December 31, 2016 , 2015 , and 2014 is as follows: Successor Generation (a) ComEd PECO BGE PHI (e) Other (b) Intersegment Eliminations Exelon Operating revenues (c) : 2016 Competitive businesses electric revenues $ 15,390 $ — $ — $ — $ — $ — $ (1,430 ) $ 13,960 Competitive businesses natural gas revenues 2,146 — — — — — — 2,146 Competitive businesses other revenues 215 — — — — — (4 ) 211 Rate-regulated electric revenues — 5,254 2,531 2,609 3,506 — (31 ) 13,869 Rate-regulated natural gas revenues — — 463 624 92 — (13 ) 1,166 Shared service and other revenues — — — — 45 1,648 (1,686 ) 7 2015 Competitive businesses electric revenues $ 15,944 $ — $ — $ — $ — $ — $ (744 ) $ 15,200 Competitive businesses natural gas revenues 2,433 — — — — — — 2,433 Competitive businesses other revenues 758 — — — — — (1 ) 757 Rate-regulated electric revenues — 4,905 2,486 2,490 — — (5 ) 9,876 Rate-regulated natural gas revenues — — 546 645 — — (15 ) 1,176 Shared service and other revenues — — — — — 1,372 (1,367 ) 5 2014 Competitive businesses electric revenues $ 14,533 $ — $ — $ — $ — $ — $ (760 ) $ 13,773 Competitive businesses natural gas revenues 2,705 — — — — — (1 ) 2,704 Competitive businesses other revenues 155 — — — — — (1 ) 154 Rate-regulated electric revenues — 4,564 2,448 2,460 — — (5 ) 9,467 Rate-regulated natural gas revenues — — 646 705 — — (26 ) 1,325 Shared service and other revenues — — — — — 1,285 (1,279 ) 6 Intersegment revenues (d) : 2016 $ 1,428 $ 15 $ 8 $ 21 $ 45 $ 1,647 $ (3,159 ) $ 5 2015 745 4 2 14 — 1,367 (2,127 ) 5 2014 762 4 2 25 — 1,280 (2,067 ) 6 Depreciation and amortization: 2016 $ 1,879 $ 775 $ 270 $ 423 $ 515 $ 74 $ — $ 3,936 2015 1,054 707 260 366 — 63 — 2,450 2014 967 687 236 371 — 53 — 2,314 Operating expenses (c) : 2016 $ 16,856 $ 4,056 $ 2,292 $ 2,683 $ 3,549 $ 1,928 $ (3,164 ) $ 28,200 2015 16,872 3,889 2,404 2,578 — 1,444 (2,131 ) 25,056 2014 16,923 3,586 2,522 2,726 — 1,353 (2,071 ) 25,039 Equity in earnings (losses) of unconsolidated affiliates: 2016 $ (25 ) $ — $ — $ — $ — $ 1 $ — $ (24 ) 2015 (8 ) — — — — 1 — (7 ) 2014 (20 ) — — — — — — (20 ) Interest expense, net: 2016 $ 364 $ 461 $ 123 $ 103 $ 195 $ 290 $ — $ 1,536 2015 365 332 114 99 — 123 — 1,033 2014 356 321 113 106 — 169 — 1,065 Income (loss) before income taxes: 2016 $ 873 $ 679 $ 587 $ 468 $ (58 ) $ (555 ) $ (5 ) $ 1,989 2015 1,850 706 521 477 — (219 ) (5 ) 3,330 2014 1,226 676 466 351 — (227 ) (6 ) 2,486 Income taxes: 2016 $ 290 $ 301 $ 149 $ 174 $ 3 $ (156 ) $ — $ 761 2015 502 280 143 189 — (41 ) — 1,073 2014 207 268 114 140 — (63 ) — 666 Net income (loss): 2016 $ 558 $ 378 $ 438 $ 294 $ (61 ) $ (398 ) $ (5 ) $ 1,204 2015 1,340 426 378 288 — (177 ) (5 ) 2,250 2014 1,019 408 352 211 — (164 ) (6 ) 1,820 Capital expenditures: 2016 $ 3,078 $ 2,734 $ 686 $ 934 $ 1,008 $ 113 $ — $ 8,553 2015 3,841 2,398 601 719 — 65 — 7,624 2014 3,012 1,689 661 620 — 95 — 6,077 Total assets: 2016 $ 46,974 $ 28,335 $ 10,831 $ 8,704 $ 21,025 $ 10,369 $ (11,334 ) $ 114,904 2015 46,529 26,532 10,367 8,295 — 15,389 (11,728 ) 95,384 __________________________ (a) Generation includes the six reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. For the year ended December 31, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $ 290 million , sales to BGE of $ 608 million , sales to Pepco of $295 million , sales to DPL of $154 million and sales to ACE of $37 million in the Mid-Atlantic region, and sales to ComEd of $ 47 million in the Midwest region, which eliminate upon consolidation. For the year ended December 31, 2015 , intersegment revenues for Generation include revenue from sales to PECO of $ 224 million and sales to BGE of $ 502 million in the Mid-Atlantic region, and sales to ComEd of $ 18 million in the Midwest region, which eliminate upon consolidation. For the year ended December 31, 2014 , intersegment revenues for Generation include revenue from sales to PECO of $ 198 million and sales to BGE of $ 387 million in the Mid-Atlantic region, and sales to ComEd of $ 176 million in the Midwest region, net of $ 7 million related to the unrealized mark-to-market losses related to the ComEd swap, which eliminate upon consolidation. (b) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (c) For the years ended December 31, 2016 , 2015 and 2014 , utility taxes of $122 million , $105 million and $89 million , respectively, are included in revenues and expenses for Generation. For the years ended December 31, 2016 , 2015 and 2014 , utility taxes of $242 million , $236 million and $238 million , respectively, are included in revenues and expenses for ComEd. For the years ended December 31, 2016 , 2015 and 2014 , utility taxes of $136 million , $133 million and $128 million , respectively, are included in revenues and expenses for PECO. For the years ended December 31, 2016 , 2015 and 2014 , utility taxes of $85 million , $85 million and $86 million are included in revenues and expenses for BGE, respectively. (d) Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in operating revenues in the Consolidated Statements of Operations and Comprehensive Income. (e) Amounts included represent activity for PHI's successor period, March 24, 2016 through December 31, 2016 . PHI includes the three reportable segments: Pepco, DPL and ACE. See tables below for PHI's predecessor periods, including Pepco, DPL and ACE, for January 1, 2016 to March 23, 2016 and for the years ended December 31, 2015 and December 31, 2014 . Successor and Predecessor PHI: Pepco DPL ACE Other (b) Intersegment PHI Operating revenues (a) : March 24, 2016 to December 31, 2016 - Successor Rate-regulated electric revenues $ 1,675 $ 850 $ 989 $ 5 $ (13 ) $ 3,506 Rate-regulated natural gas revenues — 92 — — — 92 Shared service and other revenues — — — 45 — 45 January 1, 2016 to March 23, 2016 - Predecessor Rate-regulated electric revenues $ 511 $ 279 $ 268 $ 42 $ (4 ) $ 1,096 Rate-regulated natural gas revenues — 56 — 1 — 57 Shared service and other revenues — — — — — — December 31, 2015 - Predecessor Rate-regulated electric revenues $ 2,129 $ 1,138 $ 1,295 $ 210 $ (2 ) $ 4,770 Rate-regulated natural gas revenues — 164 — 1 — 165 Shared service and other revenues — — — — — — December 31, 2014 - Predecessor Rate-regulated electric revenues $ 2,055 $ 1,088 $ 1,210 $ 264 $ (3 ) $ 4,614 Rate-regulated natural gas revenues — 194 — — — 194 Shared service and other revenues — — — — — — Intersegment revenues: March 24, 2016 to December 31, 2016 - Successor $ 4 $ 5 $ 2 $ 47 $ (13 ) $ 45 January 1, 2016 to March 23, 2016 - Predecessor 1 2 1 — (4 ) — December 31, 2015 - Predecessor 5 6 4 — (15 ) — December 31, 2014 - Predecessor 5 7 4 — (16 ) — Depreciation and amortization: March 24, 2016 to December 31, 2016 - Successor $ 224 $ 120 $ 128 $ 43 $ — $ 515 January 1, 2016 to March 23, 2016 - Predecessor 71 37 37 11 (4 ) 152 December 31, 2015 - Predecessor 256 148 175 45 — 624 December 31, 2014 - Predecessor 212 122 155 38 (1 ) 526 Operating expenses: March 24, 2016 to December 31, 2016 - Successor $ 1,577 $ 952 $ 1,000 $ 33 $ (13 ) $ 3,549 January 1, 2016 to March 23, 2016 - Predecessor 443 284 251 73 (3 ) 1,048 December 31, 2015 - Predecessor 1,790 1,137 1,161 220 — 4,308 December 31, 2014 - Predecessor 1,706 1,075 1,073 350 (1 ) 4,203 Interest expense, net: March 24, 2016 to December 31, 2016 - Successor $ 98 $ 38 $ 47 $ 12 $ — $ 195 January 1, 2016 to March 23, 2016 - Predecessor 29 12 15 11 (2 ) 65 December 31, 2015 - Predecessor 124 50 64 43 (1 ) 280 December 31, 2014 - Predecessor 115 48 64 42 — 269 Income (loss) before income taxes: March 24, 2016 to December 31, 2016 - Successor $ 36 $ (30 ) $ (51 ) $ (84 ) $ 71 $ (58 ) January 1, 2016 to March 23, 2016 - Predecessor 47 43 5 59 (118 ) 36 December 31, 2015 - Predecessor 289 125 73 23 (29 ) 481 December 31, 2014 - Predecessor 264 169 76 306 (435 ) 380 Income taxes: March 24, 2016 to December 31, 2016 - Successor $ 26 $ 5 $ (5 ) $ (23 ) $ — $ 3 January 1, 2016 to March 23, 2016 - Predecessor 15 17 1 (16 ) — 17 December 31, 2015 - Predecessor 102 49 33 (48 ) 27 163 December 31, 2014 - Predecessor 93 65 30 (228 ) 178 138 Net income (loss): March 24, 2016 to December 31, 2016 - Successor $ 10 $ (35 ) $ (47 ) $ (34 ) $ 45 $ (61 ) January 1, 2016 to March 23, 2016 - Predecessor 32 26 5 (44 ) — 19 December 31, 2015 - Predecessor 187 76 40 25 (1 ) 327 December 31, 2014 - Predecessor 171 104 46 (78 ) (1 ) 242 Capital Expenditures: March 24, 2016 to December 31, 2016 - Successor $ 489 $ 277 $ 218 $ 24 $ — $ 1,008 January 1, 2016 to March 23, 2016 - Predecessor 97 72 93 11 — 273 December 31, 2015 - Predecessor 544 352 300 34 — 1,230 December 31, 2014 - Predecessor 567 352 225 79 — 1,223 Total assets: December 31, 2016 - Successor $ 7,335 $ 4,153 $ 3,457 $ 10,804 $ (4,724 ) $ 21,025 December 31, 2015 - Predecessor 6,908 3,969 3,387 7,162 (5,238 ) 16,188 _________ (a) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 25 — Supplemental Financial Information for total utility taxes for the year ended December 31, 2016 and 2015 (b) Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities. For the predecessor periods presented, Other includes the activity of PHI’s unregulated businesses which were distributed to Exelon and Generation as a result of the PHI Merger.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2016
Related Party Transactions [Abstract]
Schedule of Related Party Transactions [Table Text Block]	PHI The financial statements of PHI include related party transactions as presented in the tables below: Successor March 24, 2016 to December 31, 2016 Operating revenues from affiliates: BSC $ 44 Generation 1 Total operating revenues from affiliates $ 45 Purchased power from affiliate Generation $ 486 Operating and maintenance from affiliates: BSC $ 86 PCI 3 Total operating and maintenance from affiliates $ 89 Cash dividends paid to parent $ 273 Contribution from member $ 1,251 ACE The financial statements of ACE include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: PHISCO $ 2 $ 2 $ 1 Other 1 2 3 Total operating revenues from affiliates $ 3 $ 4 $ 4 Purchased power from affiliate Generation (a) $ 37 $ — $ — Operating and maintenance: PHISCO (b) $ 155 $ 143 $ 124 Operating and maintenance from affiliates: BSC (b) $ 15 $ — $ — Other 3 3 3 Total operating and maintenance from affiliates $ 18 $ 3 $ 3 Cash dividends paid to parent $ 63 $ 12 $ 26 Contribution from parent $ 139 $ 95 $ — The financial statements of ComEd include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates Generation $ 7 $ 4 $ 4 BSC 6 — — PECO 1 — — BGE 1 — — Total operating revenues from affiliates $ 15 $ 4 $ 4 Purchased power from affiliate Generation (a) $ 47 $ 18 $ 176 Operating and maintenance from affiliates BSC (b) $ 225 $ 195 $ 166 PECO 1 — — BGE 1 — — Total operating and maintenance from affiliates 227 195 166 Interest expense to affiliates, net: ComEd Financing III $ 13 $ 13 $ 13 Capitalized costs BSC (b) $ 112 $ 103 $ 77 Cash dividends paid to parent $ 369 $ 299 $ 307 Contribution from parent $ 315 $ 202 $ 273 December 31, 2016 2015 Payables to affiliates (current): Generation (a) $ 9 $ — BSC (b) 2 — DPL 2 — PHISCO (b) 16 15 Other — 1 Total payables to affiliates (current) $ 29 $ 16 ______________________ (a) ACE purchases electric supply from Generation under contracts executed through its competitive procurement process. See Note 3 — Regulatory Matters for additional information. (b) ACE receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. December 31, 2016 2015 Receivables from affiliates (current): Pepco $ 1 $ — ACE 2 — Total receivable from affiliates (current) $ 3 $ — Payables to affiliates (current): Generation (a) $ 16 $ — BSC (b) 3 — PHISCO (b) 19 19 Other — 1 Total payables to affiliates (current) $ 38 $ 20 ______________________ The financial statements of PECO include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: Generation (a) $ 3 $ 2 $ 2 BSC 3 — — ComEd 1 — — BGE 1 — — Total operating revenues from affiliates $ 8 $ 2 $ 2 Purchased power from affiliate Generation (b) $ 287 $ 220 $ 194 Operating and maintenance from affiliates: BSC (c) $ 142 $ 107 $ 96 Generation 2 3 3 ComEd 1 — — BGE 1 — $ — Total operating and maintenance from affiliates $ 146 $ 110 $ 99 Interest expense to affiliates, net: PECO Trust III $ 6 $ 6 $ 6 PECO Trust IV 6 6 6 Total interest expense to affiliates, net $ 12 $ 12 $ 12 Capitalized costs BSC (c) $ 57 $ 40 $ 39 Cash dividends paid to parent $ 277 $ 279 $ 320 Contribution from parent $ 18 $ 16 $ 24 December 31, 2016 2015 Payables to affiliates (current): ComEd Financing III $ 4 $ 4 PECO Trust III 1 1 BGE Capital Trust II 3 3 Total payables to affiliates (current) $ 8 $ 8 Long-term debt due to financing trusts: ComEd Financing III $ 205 $ 205 PECO Trust III 81 81 PECO Trust IV 103 103 BGE Capital Trust II 252 252 Total long-term debt due to financing trusts $ 641 $ 641 ____________________________ (a) The intersegment profit associated with the sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in operating revenues in the Consolidated Statements of Operations. See Note 3 — Regulatory Matters for additional information. (b) Beginning in 2012, Generation entered into a power services agency agreement (PSAA) with the CENG plants, which as of April 1, 2014, was amended and extended until the permanent cessation of power generation by the CENG generation plants. The PSAA is an agreement under which Generation provides scheduling, asset management and billing services to the CENG plants for a specified monthly fee. The charges for services reflect the cost of the services. On April 1, 2014, Generation and CENG entered into a Nuclear Operating Services Agreement (NOSA) pursuant to which Generation will operate the CENG nuclear generation fleet owned by CENG subsidiaries and provide corporate and administrative services for the remaining life of the CENG nuclear plants as if they were part of the Generation nuclear fleet. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . (c) CENG owns 100% of four nuclear units in Maryland and New York and 82% of Nine Mile Point Unit 2 in New York. Beginning in 2012, Generation had a PPA under which it purchased 85% of the nuclear plant output owned by CENG that was not sold to third parties under pre-existing unit-contingent PPAs through 2014. Beginning on January 1, 2015 and continuing to the end of the life of the respective plants, Generation will purchase on a unit-contingent basis 50.01% of the nuclear plant output owned by CENG and a subsidiary of EDF will purchase on a unit-contingent basis 49.99% of the nuclear plant output owned by CENG (EDF PPA) not sold to third parties. Beginning April 1, 2014, sales to Generation are eliminated in consolidation. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . (d) During 2014, Generation closed the sale of Safe Harbor Water Power Corporation, Keystone Fuels, LLC, and Conemaugh Fuels LLC. Generation recorded purchase power and fuel costs from affiliates related to these generating assets during the time these assets were still partially owned by Generation. See Note 4 — Mergers, Acquisitions, and Dispositions for more information. (e) Prior to April 1, 2014, Generation’s total gain (loss) in equity method investments includes equity investment income (loss) and amortization of the basis difference established as a result of purchase accounting applied upon Constellation merger in 2012. CENG was fully consolidated on April 1, 2014. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . December 31, 2016 2015 Prepaid voluntary employee beneficiary association trust (c) $ 5 $ 11 Receivable from affiliates (current): Voluntary employee beneficiary association trust $ 2 $ 2 Generation 9 9 Exelon Corporate (e) 345 188 Total receivable from affiliates (current) $ 356 $ 199 Receivable from affiliates (noncurrent): Generation (d) $ 2,169 $ 2,172 Other 1 — Total receivable from affiliates (noncurrent) $ 2,170 $ 2,172 Payables to affiliates (current): Generation (a) $ 14 $ 15 BSC (b) 42 39 ComEd Financing III 4 4 PECO 2 2 Exelon Corporate 3 2 Total payables to affiliates (current) $ 65 $ 62 Long-term debt to ComEd financing trust ComEd Financing III $ 205 $ 205 _______________________ (a) ComEd procures a portion of its electricity supply requirements from Generation under an ICC-approved RFP contract. ComEd also purchases RECs from Generation. In addition, purchased power expense includes the settled portion of the financial swap contract with Generation, which expired in 2013. See Note 3 — Regulatory Matters and Note 13 — Derivative Financial Instruments for additional information. (b) ComEd receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. (c) The voluntary employee benefit association trusts covering active employees are included in corporate operations and are funded by the Registrants. A prepayment to the active welfare plans has accumulated due to actuarially determined contribution rates, which are the basis for ComEd’s contributions to the plans, being higher than actual claim expense incurred by the plans over time. The prepayment is included in other current assets. (d) ComEd has a long-term receivable from Generation as a result of the nuclear decommissioning contractual construct for generating facilities previously owned by ComEd. To the extent the assets associated with decommissioning are greater than the applicable ARO at the end of decommissioning, such amounts are due back to ComEd for payment to ComEd’s customers. (e) Represents indemnification from Exelon Corporate related to the like-kind exchange. The financial statements of Pepco include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: Generation (a) $ 1 $ — $ — PHISCO 4 5 5 Total operating revenues from affiliates $ 5 $ 5 $ 5 Purchased power from affiliate Generation (b) $ 295 $ — $ — Operating and maintenance: PHISCO (c) $ 263 $ 240 $ 220 PES (d) 39 26 30 Total operating and maintenance $ 302 $ 266 $ 250 Operating and maintenance from affiliates: BSC (c) $ 31 $ — $ — PHISCO (c) 4 4 4 Total operating and maintenance from affiliates $ 35 $ 4 $ 4 Cash dividends paid to parent $ 136 $ 146 $ 86 Contribution from parent $ 187 $ 112 $ 80 December 31, 2016 2015 Receivables from affiliates (current): ComEd (a) $ 14 $ 15 PECO (b) 33 36 BGE (c) 26 31 Pepco (d) 44 — DPL (e) 16 — ACE (f) 9 — PHISCO (j) 5 — PCI 8 — Other 1 1 Total receivables from affiliates (current) $ 156 $ 83 Intercompany money pool (current): Exelon Corporate $ — $ 1,252 PCI 55 — Total intercompany money pool (current) $ 55 $ 1,252 Payables to affiliates (current): Exelon Corporate (m) $ 22 $ 16 BSC (j) 99 78 ComEd 9 9 Other 7 1 Total payables to affiliates (current) $ 137 $ 104 Long-term debt due to affiliates (noncurrent): Exelon Corporate (o) $ 922 $ 933 Payables to affiliates (noncurrent): BSC (g) $ 1 $ — ComEd (n) 2,169 2,172 PECO (n) 438 405 Total payables to affiliates (noncurrent) $ 2,608 $ 2,577 _______________________ (a) Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs to ComEd. In addition, Generation had revenue from ComEd associated with the settled portion of the financial swap contract established as part of the Illinois Settlement. See Note 3 — Regulatory Matters for additional information. (b) Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has a ten-year agreement with PECO to sell solar AECs. See Note 3 — Regulatory Matters for additional information. (c) Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs. See Note 3 — Regulatory Matters for additional information. (d) Generation provides electric supply to Pepco under contracts executed through Pepco's competitive procurement process approved by the MDPSC and DCPSC. See Note 3 — Regulatory Matters for additional information. (e) Generation provides a portion of DPL's energy requirements under its MDPSC and DPSC approved market based SOS and gas commodity programs. See Note 3 — Regulatory Matters for additional information. (f) Generation provides electric supply to ACE under contracts executed through ACE's competitive procurement process. See Note 3 — Regulatory Matters for additional information. (g) Beginning in 2012, Generation entered into a power services agency agreement (PSAA) with the CENG plants, which as of April 1, 2014, was amended and extended until the permanent cessation of power generation by the CENG generation plants. The PSAA is an agreement under which Generation provides scheduling, asset management and billing services to the CENG plants for a specified monthly fee. The charges for services reflect the cost of the services. On April 1, 2014, Generation and CENG entered into a Nuclear Operating Services Agreement (NOSA) pursuant to which Generation will operate the CENG nuclear generation fleet owned by CENG subsidiaries and provide corporate and administrative services for the remaining life of the CENG nuclear plants as if they were part of the Generation nuclear fleet. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . (h) CENG owns 100% of four nuclear units in Maryland and New York and 82% of Nine Mile Point Unit 2 in New York. Beginning in 2012, Generation had a PPA under which it purchased 85% of the nuclear plant output owned by CENG that was not sold to third parties under pre-existing unit-contingent PPAs through 2014. Beginning on January 1, 2015 and continuing to the end of the life of the respective plants, Generation will purchase on a unit-contingent basis 50.01% of the nuclear plant output owned by CENG and a subsidiary of EDF will purchase on a unit-contingent basis 49.99% of the nuclear plant output owned by CENG (EDF PPA) not sold to third parties. Beginning April 1, 2014, sales to Generation are eliminated in consolidation. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . (i) Generation requires electricity for its own use at its generating stations. Generation purchases electricity and distribution and transmission services from PECO and BGE and only distribution and transmission services from ComEd for the delivery of electricity to its generating stations. (j) Generation receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. (k) Prior to April 1, 2014, Generation’s total gain (loss) in equity method investments includes equity income (loss) and amortization of the basis difference established as a result of purchase accounting applied upon Constellation merger in 2012. CENG was fully consolidated on April 1, 2014. For further information regarding the Investment in CENG, see Note 5 — Investment in Constellation Energy Nuclear Group, LLC . (l) During 2014, Generation closed the sale of Safe Harbor Water Power Corporation, Keystone Fuels, LLC, and Conemaugh Fuels LLC. Generation recorded purchase power and fuel costs from affiliates related to these generating assets during the time these assets were still partially owned by Generation. See Note 4 — Mergers, Acquisitions, and Dispositions for more information. (m) The balance consists of interest owed to Exelon Corporation related to the senior unsecured notes, as well as, expense related to certain invoices Exelon Corporation processed on behalf of Generation. (n) Generation has long-term payables to ComEd and PECO as a result of the nuclear decommissioning contractual construct whereby, to the extent NDT funds are greater than the underlying ARO at the end of decommissioning, such amounts are due back to ComEd and PECO, as applicable, for payment to their respective customers. See Note 16 — Asset Retirement Obligations . (o) In connection with the debt obligations assumed by Exelon as part of the Constellation merger, Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable included in Long-term Debt to affiliate on Generation’s Consolidated Balance Sheets and intercompany notes receivable at Exelon Corporate, which are eliminated in consolidation on Exelon’s Consolidated Balance Sheets. December 31, 2016 2015 Payables to affiliates (current): Generation (b) $ 26 $ 31 BSC (c) 22 17 Exelon Corporate 1 1 PECO 2 — BGE Capital Trust II 3 3 Other 1 — Total payables to affiliates (current) $ 55 $ 52 Long-term debt to BGE financing trust BGE Capital Trust II $ 252 $ 252 ______________________ (a) BGE provides energy to Generation for Generation’s own use. (b) BGE procures a portion of its electricity and gas supply requirements from Generation under its MDPSC-approved market-based SOS and gas commodity programs. See Note 3 — Regulatory Matters for additional information. (c) BGE receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. The financial statements of Exelon include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: PECO (a) $ 1 $ 1 $ 1 CENG (b) — — 17 BGE (a) 4 4 5 Other 5 4 — Total operating revenues from affiliates $ 10 $ 9 $ 23 Purchase power and fuel from affiliates: CENG (c) $ — $ — $ 282 Keystone Fuels, LLC (d) — — 138 Conemaugh Fuels, LLC (d) — — 99 Safe Harbor Water Power Corp (d) — — 12 Total purchase power and fuel from affiliates $ — $ — $ 531 Interest expense to affiliates, net: ComEd Financing III $ 13 $ 13 $ 13 PECO Trust III 6 6 6 PECO Trust IV 6 6 6 BGE Capital Trust II 16 16 16 Total interest expense to affiliates, net $ 41 $ 41 $ 41 Earnings (losses) in equity method investments: CENG (e) $ — $ — $ (19 ) Qualifying facilities and domestic power projects (25 ) (8 ) (1 ) Other 1 1 — Total losses in equity method investments $ (24 ) $ (7 ) $ (20 ) December 31, 2016 Successor Payables to affiliates (current): Generation $ 74 BSC 10 Exelon Corporate 6 PHI Corporate 4 Total payables to affiliates (current) $ 94 The financial statements of DPL include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: PHISCO $ 5 $ 5 $ 6 Other 2 1 1 Total operating revenues from affiliates $ 7 $ 6 $ 7 Purchased power from affiliate Generation (a) $ 154 $ — $ — Operating and maintenance: PHISCO (b) $ 194 $ 179 $ 163 PES (c) 8 3 — Total operating and maintenance $ 202 $ 182 $ 163 Operating and maintenance from affiliates: BSC (b) $ 18 $ — $ — Other 1 1 1 Total operating and maintenance from affiliates $ 19 $ 1 $ 1 Cash dividends paid to parent $ 54 $ 92 $ 100 Contribution from parent $ 152 $ 75 $ 130 The financial statements of Generation include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: ComEd (a) $ 47 $ 18 $ 176 PECO (b) 290 224 198 BGE (c) 608 502 387 Pepco (d) 295 — — DPL (e) 154 — — ACE (f) 37 — — CENG (g) — — 17 BSC 2 1 1 Other 6 4 — Total operating revenues from affiliates $ 1,439 $ 749 $ 779 Purchase power and fuel from affiliates: ComEd $ — $ — $ 1 BGE 12 14 25 CENG (h) — — 282 Keystone Fuels, LLC (l) — — 138 Conemaugh Fuels, LLC (l) — — 99 Safe Harbor Water Power Corporation (l) — — 12 Total purchase power and fuel from affiliates $ 12 $ 14 $ 557 Operating and maintenance from affiliates: ComEd (i) $ 7 $ 4 $ 3 PECO (i) 3 2 2 BGE (i) 1 — — PHI 1 — — Pepco 1 — — BSC (j) 650 614 618 Total operating and maintenance from affiliates $ 663 $ 620 $ 623 Interest expense to affiliates, net: Exelon Corporate (m) $ 39 $ 43 $ 53 Earnings (losses) in equity method investments CENG (k) $ — $ — $ (19 ) Qualifying facilities and domestic power projects (25 ) (8 ) (1 ) Total losses in equity method investments $ (25 ) $ (8 ) $ (20 ) Capitalized costs BSC (j) $ 98 $ 76 $ 91 Cash distribution paid to member $ 922 $ 2,474 $ 645 Contribution from member $ 142 $ 47 $ 53 The financial statements of BGE include related party transactions as presented in the tables below: For the Years Ended December 31, 2016 2015 2014 Operating revenues from affiliates: Generation (a) $ 13 $ 14 $ 25 BSC 6 — — ComEd 1 — — PECO 1 — — Total operating revenues from affiliates $ 21 $ 14 $ 25 Purchased power from affiliate Generation (b) $ 604 $ 498 $ 382 Operating and maintenance from affiliates: BSC (c) $ 130 $ 118 $ 103 ComEd 1 — — PECO 1 — — Total operating and maintenance from affiliates $ 132 $ 118 $ 103 Interest expense to affiliates, net: BGE Capital Trust II $ 16 $ 16 $ 16 Capitalized costs BSC (c) $ 36 $ 28 $ 19 Cash dividends paid to parent $ 179 $ 158 $ — Contribution from parent $ 61 $ 7 $ — December 31, 2016 2015 Prepaid voluntary employee beneficiary association trust (d) $ 1 $ 2 Receivable from affiliate (current): ComEd $ 2 $ 2 BGE 2 — Total receivable from affiliates (current) $ 4 $ 2 Receivable from affiliate (noncurrent): Generation (e) $ 438 $ 405 Payables to affiliates (current): Generation (b) $ 33 $ 36 BSC (c) 28 17 Exelon Corporate 1 1 PECO Trust III 1 1 Total payables to affiliates (current) $ 63 $ 55 Long-term debt to financing trusts: PECO Trust III $ 81 $ 81 PECO Trust IV 103 103 Total long-term debt to financing trusts $ 184 $ 184 ________________________ (a) PECO provides energy to Generation for Generation’s own use. (b) PECO purchases electric supply from Generation under contracts executed through its competitive procurement process. In addition, PECO has five-year and ten-year agreements with Generation to purchase non-solar and solar AECs, respectively. See Note 3 — Regulatory Matters for additional information on AECs. (c) PECO receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized. (d) The voluntary employee beneficiary association trusts covering active employees are included in corporate operations and are funded by the Registrants. A prepayment to the active welfare plans has accumulated due to actuarially determined contribution rates, which are the basis for PECO’s contributions to the plans, being higher than actual claim expense incurred by the plans over time. (e) PECO has a long-term receivable from Generation as a result of the nuclear decommissioning contractual construct, whereby, to the extent the assets associated with decommissioning are greater than the applicable ARO at the end of decommissioning, such amounts are due back to PECO for payment to PECO’s customers. December 31, 2016 2015 Payables to affiliates (current): Generation (b) $ 44 $ — BSC (c) 4 — DPL 1 — PHISCO (c) 25 25 PES (e) — 4 Other — 1 Total payables to affiliates (current) $ 74 $ 30 ______________________

Quarterly Data (Unaudited) (Tab

Quarterly Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Quarterly Financial Information	The data shown below includes all adjustments that ACE considers necessary for a fair presentation of such amounts: Operating Revenues Operating (Loss) Income Net (Loss) Income 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 291 $ 334 $ (121 ) $ 29 $ (100 ) $ 9 June 30 270 285 19 25 3 6 September 30 421 386 83 51 47 22 December 31 275 291 26 29 8 3 The data shown below includes all adjustments that Pepco considers necessary for a fair presentation of such amounts: Operating Revenues Operating (Loss) Income Net (Loss) Income Common Shareholders 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 551 $ 545 $ (105 ) $ 63 $ (108 ) $ 26 June 30 509 504 97 83 49 42 September 30 635 592 132 115 79 60 December 31 491 488 51 123 23 59 The data shown below includes all adjustments that PHI considers necessary for a fair presentation of such amounts: Successor Predecessor Successor Predecessor Successor Predecessor Operating Revenues Operating (Loss) Income Net (Loss) Income Membership Interest 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 105 (a) $ 1,354 $ (411 ) (a) $ 142 $ (309 ) (a) $ 53 June 30 1,066 1,119 136 139 52 53 September 30 1,394 1,336 279 184 166 91 December 31 1,078 1,126 90 208 30 130 The data shown below includes all adjustments that PECO considers necessary for a fair presentation of such amounts: Operating Revenues Operating Income Net Income Attributable to Common Shareholders 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 841 $ 985 $ 196 $ 223 $ 124 $ 139 June 30 664 661 152 124 100 70 September 30 788 740 204 154 122 90 December 31 701 645 150 128 92 79 The data shown below includes all adjustments that Generation considers necessary for a fair presentation of such amounts: Operating Revenues Operating (Loss) Income Net (Loss) Income 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 4,739 $ 5,840 $ 415 $ 719 $ 310 $ 443 June 30 3,589 4,232 (13 ) 703 (8 ) 398 September 30 5,035 4,768 342 622 236 377 December 31 4,388 4,294 94 230 (41 ) 154 The data shown below includes all adjustments that DPL considers necessary for a fair presentation of such amounts: Operating Revenues Operating (Loss) Income Net (Loss) Income 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 362 $ 421 $ (72 ) $ 63 $ (72 ) $ 32 June 30 281 271 30 24 12 8 September 30 331 314 72 32 44 15 December 31 303 296 20 46 7 21 ACE The data shown below, which may not equal the total for the year due to the effects of rounding and dilution, includes all adjustments that Exelon considers necessary for a fair presentation of such amounts: Operating Revenues Operating Income Net Income 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 7,573 $ 8,830 $ 483 $ 1,366 $ 173 $ 693 June 30 6,910 6,514 647 1,134 267 638 September 30 9,002 7,401 1,267 1,200 490 629 December 31 7,875 6,702 714 707 204 309 The data shown below includes all adjustments that BGE considers necessary for a fair presentation of such amounts: Operating Revenues Operating Income Net Income Attributable to Common Shareholders 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 929 $ 1,036 $ 187 $ 204 $ 98 $ 106 June 30 680 628 59 99 31 44 September 30 812 725 115 110 54 51 December 31 812 746 190 144 103 74 The data shown below includes all adjustments that ComEd considers necessary for a fair presentation of such amounts: Operating Revenues Operating Income Net Income 2016 2015 2016 2015 2016 2015 Quarter ended: March 31 $ 1,249 $ 1,185 $ 274 $ 230 $ 115 $ 90 June 30 1,286 1,148 324 243 145 99 September 30 1,497 1,376 389 327 37 149 December 31 1,223 1,196 217 217 80 87
Average Basic And Diluted Shares And Net Income Per Basic And Diluted Share	Average Basic Shares Outstanding (in millions) Net Income 2016 2015 2016 2015 Quarter ended: March 31 923 862 $ 0.19 $ 0.80 June 30 924 863 0.29 0.74 September 30 925 913 0.53 0.69 December 31 925 921 0.22 0.34 Average Diluted Shares Outstanding (in millions) Net Income 2016 2015 2016 2015 Quarter ended: March 31 925 867 $ 0.19 $ 0.80 June 30 926 866 0.29 0.74 September 30 927 915 0.53 0.69 December 31 928 924 0.22 0.33
Per Share Information	The following table presents the New York Stock Exchange—Composite Common Stock Prices and dividends by quarter on a per share basis: 2016 2015 Fourth Quarter Third Quarter Second Quarter First Quarter Fourth Quarter Third Quarter Second Quarter First Quarter High price $ 36.36 $ 37.70 $ 36.37 $ 35.95 $ 31.37 $ 34.44 $ 34.98 $ 38.25 Low price 29.82 32.86 33.18 26.26 25.09 28.41 31.28 31.71 Close 35.49 33.29 36.36 35.86 27.77 29.70 31.42 33.61 Dividends 0.318 0.318 0.318 0.310 0.310 0.310 0.310 0.310

Significant Accounting Polici66

Significant Accounting Policies - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Significant Accounting Policies Additional Narrative Information [Line Items]
Percentage ownership of consolidated subsidiaries	100.00%
Third Party interest in ComEd (less than $1 million)	$ 1,775,000,000	$ 1,308,000,000
Minimum expectation of tax position to be realized	50.00%
Commonwealth Edison Company [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Percentage ownership of consolidated subsidiaries	99.00%
Third Party interest in ComEd (less than $1 million)	$ 1,000,000	1,000,000
CENG [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Ownership interest	50.01%
Exelon Generation Co L L C [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Cost of spent nuclear fuel disposal per kWh of net nuclear generation	$ (0.001)
Development Costs, Period Cost	1,700,000,000	1,300,000,000
Utilities Operating Expense, Other	$ 13,000,000
Potomac Electric Power Company [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income		4,000,000	$ 1,000,000
Delmarva Power and Light Company [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income		1,000,000
Atlantic City Electric Company [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				$ 12,000,000
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results		2,000,000	$ 1,000,000
Pepco Holdings LLC [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income		$ 34,000,000
Minimum [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Ownership interest	20.00%
Maximum [Member]
Significant Accounting Policies Additional Narrative Information [Line Items]
Ownership interest	50.00%

Significant Accounting Polici67

Significant Accounting Policies - Summary of Capitalized Software Costs (Details) - USD ($)		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Capitalized Software [Line Items]
Net unamortized software costs	[1]		$ 808,000,000	$ 808,000,000	$ 633,000,000
Amortization of capitalized software costs	[1]			255,000,000	208,000,000	$ 186,000,000
Pepco Holdings LLC [Member]
Capitalized Software [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income					34,000,000
Exelon Generation Co L L C [Member]
Capitalized Software [Line Items]
Net unamortized software costs	[1]		173,000,000	173,000,000	180,000,000
Amortization of capitalized software costs	[1]			72,000,000	73,000,000	59,000,000
Commonwealth Edison Co [Member]
Capitalized Software [Line Items]
Net unamortized software costs			213,000,000	213,000,000	172,000,000
Amortization of capitalized software costs				62,000,000	47,000,000	45,000,000
PECO Energy Co [Member]
Capitalized Software [Line Items]
Net unamortized software costs			91,000,000	91,000,000	86,000,000
Amortization of capitalized software costs				33,000,000	33,000,000	28,000,000
Baltimore Gas and Electric Company [Member]
Capitalized Software [Line Items]
Net unamortized software costs			164,000,000	164,000,000	178,000,000
Amortization of capitalized software costs				44,000,000	46,000,000	43,000,000
Potomac Electric Power Company [Member]
Capitalized Software [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income					4,000,000	1,000,000
Net unamortized software costs			1,000,000	1,000,000	0
Amortization of capitalized software costs				0	(2,000,000)	2,000,000
Delmarva Power and Light Company [Member]
Capitalized Software [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income					1,000,000
Net unamortized software costs			1,000,000	1,000,000	1,000,000
Amortization of capitalized software costs				0	0	0
Atlantic City Electric Company [Member]
Capitalized Software [Line Items]
Net unamortized software costs			1,000,000	1,000,000	1,000,000
Amortization of capitalized software costs				0	0	0
Successor [Member] | Pepco Holdings LLC [Member]
Capitalized Software [Line Items]
Net unamortized software costs			153,000,000	$ 153,000,000
Amortization of capitalized software costs			$ 29,000,000
Predecessor [Member] | Pepco Holdings LLC [Member]
Capitalized Software [Line Items]
Net unamortized software costs					172,000,000
Amortization of capitalized software costs		$ 8,000,000			$ 36,000,000	$ 30,000,000
[1]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246RUU4RjBGOTk5MkM0QUIyMzlBMTQ5RjkyNUQxRkRBNjIM}

Significant Accounting Polici68

Significant Accounting Policies - Summary of Total Interest Incurred, Capitalized and Credits to AFUDC (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Capitalized Interest And AFUDC [Line Items]
Total interest incurred	[1],[2]			$ 1,678	$ 1,170	$ 1,144
Capitalized interest	[2]			108	79	63
Credits to AFUDC debt and equity	[2]			98	44	37
Exelon Generation Co L L C [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred	[1],[2]			472	445	419
Capitalized interest	[2]			107	79	63
Credits to AFUDC debt and equity	[2]			0	0	0
Commonwealth Edison Co [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred	[1]			469	336	323
Capitalized interest				0	0	0
Credits to AFUDC debt and equity				22	9	5
PECO Energy Co [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred	[1]			127	116	115
Capitalized interest				0	0	0
Credits to AFUDC debt and equity				11	7	8
Baltimore Gas and Electric Company [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred	[1]			114	113	118
Capitalized interest				0	0	0
Credits to AFUDC debt and equity				30	28	24
Potomac Electric Power Company [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred				137	131	121
Capitalized interest				0	0	0
Credits to AFUDC debt and equity				29	19	16
Delmarva Power and Light Company [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred				52	51	49
Capitalized interest				0	0	0
Credits to AFUDC debt and equity				7	2	3
Atlantic City Electric Company [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred				65	65	65
Capitalized interest				0	0	0
Credits to AFUDC debt and equity				$ 9	2	2
Predecessor [Member] | Pepco Holdings LLC [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred		$ 68			289	277
Credits to AFUDC debt and equity		$ 10			$ 23	$ 21
Successor [Member] | Pepco Holdings LLC [Member]
Capitalized Interest And AFUDC [Line Items]
Total interest incurred			$ 207
Credits to AFUDC debt and equity			$ 35
[1]	Successor PredecessorPHIMarch 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014Total incurred interest(b)$207 $68 $289 $277Credits to AFUDC debt and equity35 10 23 21
[2]	Successor PredecessorPHIMarch 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014Total incurred interest(b)$207 $68 $289 $277Credits to AFUDC debt and equity35 10 23 21

Significant Accounting Polici69

Significant Accounting Policies Balance Sheet Classification of Deferred Taxes (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Other noncurrent assets	$ 1,472	$ 1,445
Other noncurrent liabilities	1,827	1,491
Commonwealth Edison Co [Member]
Other noncurrent assets	325	324
Other noncurrent liabilities	529	507
Exelon Generation Co L L C [Member]
Other noncurrent assets	688	627
Other noncurrent liabilities	595	602
PECO Energy Co [Member]
Other noncurrent assets	20	21
Other noncurrent liabilities	85	90
Baltimore Gas and Electric Company [Member]
Other noncurrent assets	9	8
Other noncurrent liabilities	$ 61	$ 61

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details) $ in Millions		Apr. 01, 2014USD ($)	Mar. 23, 2016USD ($)	Dec. 31, 2016USD ($)projectVIE	Dec. 31, 2016USD ($)projectVIEMW	Dec. 31, 2015USD ($)VIE	Dec. 31, 2014USD ($)	Sep. 30, 2016USD ($)	Jun. 09, 2015USD ($)	Jul. 18, 2014USD ($)
Variable Interest Entity [Line Items]
Note Receivable					$ 27
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Number of variable interest entities not consolidated by equity holders | VIE				8	8
Number of variable interest entities consolidated | VIE				9	9	7
Investments In Nonconsolidated Variable Interest Entities				$ 248	$ 248	$ 11
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided				75	75
Severance Costs					19	18
Guarantee obligations maximum exposure				50	50
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount				18	18
Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Investments In Nonconsolidated Variable Interest Entities				248	248	$ 11
Constellation Energy Nuclear Group [Member] | Financial Guarantee [Member]
Consolidated Variable Interest Entity [Abstract]
Guarantee obligations maximum exposure		$ 165
Constellation Energy Nuclear Group [Member] | Payment Guarantee [Member]
Consolidated Variable Interest Entity [Abstract]
Guarantee obligations maximum exposure		245
Distributed Energy Company [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests				250	250					$ 85
Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests				$ 172	$ 172
Electricite De France LLC [Member] | Constellation Energy Nuclear Group [Member] | Financial Guarantee [Member]
Consolidated Variable Interest Entity [Abstract]
Guarantee obligations maximum exposure		145
Electricite De France LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Consolidated Variable Interest Entity [Abstract]
Ownership interest				49.99%	49.99%
Pepco Holdings LLC [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Number of variable interest entities consolidated | VIE						1
Pepco Holdings LLC [Member] | Predecessor [Member]
Consolidated Variable Interest Entity [Abstract]
Severance Costs	[1]		$ 0			$ 0
Pepco Holdings LLC [Member] | Successor [Member]
Consolidated Variable Interest Entity [Abstract]
Severance Costs	[1]			$ 1
Atlantic City Electric Company [Member]
Consolidated Variable Interest Entity [Abstract]
Guarantee obligations maximum exposure								$ 13
Atlantic City Electric Company [Member] | ATF [Member]
Consolidated Variable Interest Entity [Abstract]
Cash Remitted To VIE					$ 60	61	$ 55
Exelon Generation Co L L C [Member]
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Investments In Nonconsolidated Variable Interest Entities				18	18
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided				$ 21	$ 21
Wind project entities with noncontrolling equity interests | project				6	6
Noncontrolling equity interest ownership percentage held by third parties				1.00%	1.00%
Number of projects with significant economic power | project				5	5
Ownership interests in project entities				99.00%	99.00%
Severance Costs	[1]				$ 13	15
Exelon Generation Co L L C [Member] | Other Severance Charges [Member]
Consolidated Variable Interest Entity [Abstract]
Severance Costs					6
Severance Obligation				$ 0	0
Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group [Member]
Consolidated Variable Interest Entity [Abstract]
Due from Affiliates		400		316	$ 316
Exelon Generation Co L L C [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
equity interest percentage sold					69.00%
Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests				78	$ 78
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided				275	$ 275
Exelon Generation Co L L C [Member] | Solar Project Limited Liability Companies [Member]
Consolidated Variable Interest Entity [Abstract]
Business Acquisitions, Megawatts Acquired | MW					242
Debt and Capital Lease Obligations				$ 568	$ 568
Exelon Generation Co L L C [Member] | AGE Biomass project [Member]
Consolidated Variable Interest Entity [Abstract]
Ownership interests in project entities				90.00%	90.00%
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided		7		$ 7	$ 7				$ 275
Remeasurement gain from derecognition of equity method investment		$ 261
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Equity Method Investment Variable Interest Entities [Member]
Consolidated Variable Interest Entity [Abstract]
Parental guarantee provided				$ 637	$ 637
Exelon Generation Co L L C [Member] | CENG [Member]
Consolidated Variable Interest Entity [Abstract]
Ownership interest				50.01%	50.01%
Exelon Generation Co L L C [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
equity interest percentage sold					71.00%
Consolidated Variable Interest Entity [Abstract]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage					100.00%
Ownership Percentage Of Consolidated Variable Interest Entities					100.00%
Baltimore Gas and Electric Company [Member]
Consolidated Variable Interest Entity [Abstract]
Severance Costs	[1]				$ 1	1
Baltimore Gas and Electric Company [Member] | RSB Bond Co LLC [Member]
Consolidated Variable Interest Entity [Abstract]
Remittance of payments received from customers for rate stabilization to BondCo.					$ 86	$ 86	$ 85
[1]	The amounts above for Generation, ComEd, PECO, BGE and PHI include immaterial amounts billed by BSC for the years ended December 31, 2016 and 2015.

Variable Interest Entities - Ca

Variable Interest Entities - Carrying Amounts and Classification of Consolidated VIE Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$ 9,517	$ 8,918
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	3,598	3,400
CurrentAssetsMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	954	909
NoncurrentAssetMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	8,563	8,009
CurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	885	473
NoncurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	2,713	2,927
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	9,441	8,885
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	3,414	3,271
Exelon Generation Co L L C [Member] | CurrentAssetsMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	916	881
Exelon Generation Co L L C [Member] | NoncurrentAssetMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	8,525	8,004
Exelon Generation Co L L C [Member] | CurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	802	387
Exelon Generation Co L L C [Member] | NoncurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	2,612	2,884
Pepco Holdings LLC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	49	30
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	143	172
Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets		30
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities		172
Pepco Holdings LLC [Member] | Predecessor [Member] | CurrentAssetsMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets		12
Pepco Holdings LLC [Member] | Predecessor [Member] | NoncurrentAssetMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets		18
Pepco Holdings LLC [Member] | Predecessor [Member] | CurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities		48
Pepco Holdings LLC [Member] | Predecessor [Member] | NoncurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities		124
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	49
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	143
Pepco Holdings LLC [Member] | Successor [Member] | CurrentAssetsMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	14
Pepco Holdings LLC [Member] | Successor [Member] | NoncurrentAssetMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	35
Pepco Holdings LLC [Member] | Successor [Member] | CurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	42
Pepco Holdings LLC [Member] | Successor [Member] | NoncurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	101
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	32	30
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	126	172
Atlantic City Electric Company [Member] | CurrentAssetsMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	9	12
Atlantic City Electric Company [Member] | NoncurrentAssetMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	23	18
Atlantic City Electric Company [Member] | CurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	37	48
Atlantic City Electric Company [Member] | NoncurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	89	124
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	26	26
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	42	122
Baltimore Gas and Electric Company [Member] | CurrentAssetsMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	23	23
Baltimore Gas and Electric Company [Member] | NoncurrentAssetMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets	3	3
Baltimore Gas and Electric Company [Member] | CurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	42	81
Baltimore Gas and Electric Company [Member] | NoncurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$ 0	$ 41

Variable Interest Entities - As

Variable Interest Entities - Assets and Liabilities of VIEs which Creditors or Beneficiaries have No Recourse (Details) - USD ($) $ in Millions		Dec. 31, 2016	Mar. 23, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 635		$ 6,502	$ 1,878	$ 1,609
Customer		4,158		3,187
Other		1,201		912
Mark-to-market derivative assets		917		1,365
Materials and supplies		1,274		1,104
Other current assets		930		752
Total current assets		12,412		15,334
Property, plant and equipment, net		71,555		57,439
Nuclear decommissioning trust funds		11,061		10,342
Goodwill		6,677		2,672	2,672
Mark-to-market derivative assets		492		758
Other noncurrent assets		1,472		1,445
Deferred Costs and Other Assets		30,937		22,611
Total assets (a)	[1]	114,904		95,384
Long-term debt due within one year		2,430		1,500
Accounts payable		3,441		2,883
Accrued expenses		3,460		2,376
Mark-to-market derivative liabilities		282		205
Energy Marketing Contract Liabilities, Current		407		100
Other current liabilities		981		842
Total current liabilities		13,457		9,118
Long-term debt		31,575		23,645
Asset retirement obligations		9,111		8,585
Pension obligations		4,248		3,385
Energy Marketing Contract Liabilities, Noncurrent		830		117
Other noncurrent liabilities		1,827		1,491
Total liabilities	[1]	87,292		68,062
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		150		164
Restricted cash		59		100
Customer		371		219
Other		48		43
Mark-to-market derivative assets		31		140
Materials and supplies		199		181
Other current assets		50		35
Total current assets		908		882
Property, plant and equipment, net		5,415		5,160
Nuclear decommissioning trust funds		2,185		2,036
Goodwill		47		47
Mark-to-market derivative assets		23		53
Other noncurrent assets		315		90
Deferred Costs and Other Assets		7,985		7,386
Total assets (a)		8,893		8,268
Long-term debt due within one year		181		111
Accounts payable		269		216
Accrued expenses		119		115
Mark-to-market derivative liabilities		60		5
Energy Marketing Contract Liabilities, Current		15		12
Other current liabilities		30		13
Total current liabilities		674		472
Long-term debt		641		666
Asset retirement obligations		1,904		1,999
Pension obligations		9		9
Energy Marketing Contract Liabilities, Noncurrent		22		39
Other noncurrent liabilities		106		79
Deferred Credits and Other Liabilities, Noncurrent		2,682		2,792
Total liabilities		3,356		3,264
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		290		431	780	1,258
Restricted cash		158		123
Customer		2,433		2,095
Other		558		360
Mark-to-market derivative assets		917		1,365
Materials and supplies		935		880
Other current assets		701		535
Total current assets		6,528		6,342
Property, plant and equipment, net		25,585		25,843
Nuclear decommissioning trust funds		11,061		10,342
Goodwill		47		47	47
Mark-to-market derivative assets		476		733
Other noncurrent assets		688		627
Deferred Costs and Other Assets		14,861		14,344
Total assets (a)	[2]	46,974		46,529
Long-term debt due within one year		1,117		90
Accounts payable		1,610		1,583
Accrued expenses		989		935
Mark-to-market derivative liabilities		263		182
Energy Marketing Contract Liabilities, Current		72		100
Other current liabilities		313		356
Total current liabilities		5,683		4,933
Long-term debt		7,202		7,936
Asset retirement obligations		8,922		8,431
Energy Marketing Contract Liabilities, Noncurrent		80		117
Other noncurrent liabilities		595		602
Total liabilities	[2]	33,718		33,559
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		150		164
Restricted cash		27		77
Customer		371		219
Other		48		43
Mark-to-market derivative assets		31		140
Materials and supplies		199		181
Other current assets		44		30
Total current assets		870		854
Property, plant and equipment, net		5,415		5,160
Nuclear decommissioning trust funds		2,185		2,036
Goodwill		47		47
Mark-to-market derivative assets		23		53
Other noncurrent assets		277		85
Deferred Costs and Other Assets		7,947		7,381
Total assets (a)		8,817		8,235
Long-term debt due within one year		99		27
Accounts payable		269		216
Accrued expenses		116		113
Mark-to-market derivative liabilities		60		5
Energy Marketing Contract Liabilities, Current		15		12
Other current liabilities		30		13
Total current liabilities		589		386
Long-term debt		540		623
Asset retirement obligations		1,904		1,999
Pension obligations		9		9
Energy Marketing Contract Liabilities, Noncurrent		22		39
Other noncurrent liabilities		106		79
Deferred Credits and Other Liabilities, Noncurrent		2,581		2,749
Total liabilities		3,170		3,135
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		23		9	64	31
Restricted cash		24		24
Customer		395		300
Other		102		112
Materials and supplies		38		33
Other current assets		7		3
Total current assets		842		845
Property, plant and equipment, net		7,040		6,597
Other noncurrent assets		9		8
Deferred Costs and Other Assets		822		853
Total assets (a)	[3]	8,704		8,295
Long-term debt due within one year		41		378
Accounts payable		205		209
Accrued expenses		175		110
Other current liabilities		26		35
Total current liabilities		707		1,134
Long-term debt		2,281		1,480
Asset retirement obligations		21		17
Other noncurrent liabilities		61		61
Total liabilities	[3]	5,856		5,418
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0		0
Restricted cash		23		23
Customer		0		0
Other		0		0
Mark-to-market derivative assets		0		0
Materials and supplies		0		0
Other current assets		0		0
Total current assets		23		23
Property, plant and equipment, net		0		0
Nuclear decommissioning trust funds		0		0
Goodwill		0		0
Mark-to-market derivative assets		0		0
Other noncurrent assets		3		3
Deferred Costs and Other Assets		3		3
Total assets (a)		26		26
Long-term debt due within one year		41		79
Accounts payable		0		0
Accrued expenses		1		2
Mark-to-market derivative liabilities		0		0
Energy Marketing Contract Liabilities, Current		0		0
Other current liabilities		0		0
Total current liabilities		42		81
Long-term debt		0		41
Asset retirement obligations		0		0
Pension obligations		0		0
Energy Marketing Contract Liabilities, Noncurrent		0		0
Other noncurrent liabilities		0		0
Deferred Credits and Other Liabilities, Noncurrent		0		41
Total liabilities		42		122
Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents			$ 319	26	15	24
Restricted cash				14
Customer				581
Other				319
Mark-to-market derivative assets				18
Materials and supplies				122
Other current assets				80
Total current assets				1,474
Property, plant and equipment, net				10,864
Goodwill			1,406	1,406	1,407
Mark-to-market derivative assets				0
Other noncurrent assets				69
Deferred Costs and Other Assets				3,850
Total assets (a)	[4]			16,188
Long-term debt due within one year				456
Accounts payable				404
Accrued expenses				266
Mark-to-market derivative liabilities				0
Energy Marketing Contract Liabilities, Current				0
Other current liabilities				70
Total current liabilities				2,327
Long-term debt				4,823
Asset retirement obligations				8
Pension obligations				466
Energy Marketing Contract Liabilities, Noncurrent				0
Other noncurrent liabilities				200
Total liabilities	[4]			11,592
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		170	319
Restricted cash		43
Customer		496
Other		283
Mark-to-market derivative assets		0
Materials and supplies		116
Other current assets		71
Total current assets		1,838
Property, plant and equipment, net		11,598
Goodwill		4,005	$ 0
Other noncurrent assets		81
Deferred Costs and Other Assets		7,589
Total assets (a)	[4]	21,025
Long-term debt due within one year		253
Accounts payable		458
Accrued expenses		272
Energy Marketing Contract Liabilities, Current		335
Other current liabilities		47
Total current liabilities		2,284
Long-term debt		5,645
Asset retirement obligations		14
Pension obligations		0
Energy Marketing Contract Liabilities, Noncurrent		750
Other noncurrent liabilities		249
Total liabilities	[4]	13,009
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Restricted cash				12
Other current assets				0
Total current assets				12
Other noncurrent assets				18
Deferred Costs and Other Assets				18
Total assets (a)				30
Long-term debt due within one year				46
Accounts payable				0
Accrued expenses				2
Mark-to-market derivative liabilities				0
Energy Marketing Contract Liabilities, Current				0
Other current liabilities				0
Total current liabilities				48
Long-term debt				124
Asset retirement obligations				0
Pension obligations				0
Energy Marketing Contract Liabilities, Noncurrent				0
Other noncurrent liabilities				0
Deferred Credits and Other Liabilities, Noncurrent				124
Total liabilities				172
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Restricted cash		9
Other current assets		5
Total current assets		14
Other noncurrent assets		35
Deferred Costs and Other Assets		35
Total assets (a)		49
Long-term debt due within one year		40
Accounts payable		0
Accrued expenses		2
Mark-to-market derivative liabilities		0
Energy Marketing Contract Liabilities, Current		0
Other current liabilities		0
Total current liabilities		42
Long-term debt		101
Asset retirement obligations		0
Pension obligations		0
Energy Marketing Contract Liabilities, Noncurrent		0
Other noncurrent liabilities		0
Deferred Credits and Other Liabilities, Noncurrent		101
Total liabilities		143
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		101		3	$ 2	$ 3
Restricted cash		9		12
Customer		125		156
Other		44		242
Other current assets		2		12
Total current assets		399		546
Property, plant and equipment, net		2,521		2,322
Other noncurrent assets		44		19
Deferred Costs and Other Assets		537		519
Total assets (a)	[5]	3,457		3,387
Long-term debt due within one year		35		48
Accounts payable		132		96
Accrued expenses		38		70
Other current liabilities		8		14
Total current liabilities		320		297
Long-term debt		1,120		1,153
Other noncurrent liabilities		32		12
Total liabilities	[5]	2,423		2,387
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Restricted cash		9		12
Total current assets		9		12
Other noncurrent assets		23		18
Deferred Costs and Other Assets		23		18
Total assets (a)		32		30
Long-term debt due within one year		35		46
Accounts payable		0		0
Accrued expenses		2		2
Mark-to-market derivative liabilities		0		0
Energy Marketing Contract Liabilities, Current		0		0
Other current liabilities		0		0
Total current liabilities		37		48
Long-term debt		89		124
Asset retirement obligations		0		0
Pension obligations		0		0
Energy Marketing Contract Liabilities, Noncurrent		0		0
Other noncurrent liabilities		0		0
Deferred Credits and Other Liabilities, Noncurrent		89		124
Total liabilities		$ 126		$ 172
[1]	Exelon’s consolidated assets include $8,893 million and $8,268 million at December 31, 2016 and December 31, 2015, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,356 million and $3,264 million at December 31, 2016 and December 31, 2015, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2–Variable Interest Entities.
[2]	Generation’s consolidated assets include $8,817 million and $8,235 million at December 31, 2016 and 2015, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,170 million and $3,135 million at December 31, 2016 and 2015, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 2–Variable Interest Entities.
[3]	BGE’s consolidated assets include $26 million and $26 million at December 31, 2016 and December 31, 2015, respectively, of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $42 million and $122 million at December 31, 2016 and December 31, 2015, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 2 - Variable Interest Entities.
[4]	PHI’s consolidated total assets include $49 million and $30 million at December 31, 2016 and 2015, respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $143 million and $172 million at December 31, 2016 and 2015, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 2 - Variable Interest Entities.
[5]	ACE’s consolidated assets include $32 million and $30 million at December 31, 2016 and 2015, respectively, of ACE’s consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated liabilities include $126 million and $172 million at December 31, 2016 and 2015, respectively, of ACE’s consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 2 - Variable Interest Entities.

Variable Interest Entities - Su

Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Total assets		$ 1,205	$ 427
Total liabilities		502	147
Our ownership interest		248	11
Other ownership interests		455	269
Our maximum exposure to loss		18
Pledged assets for Zion Station decommissioning		113	206
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Our ownership interest		18
Pledged assets for Zion Station decommissioning		113	206
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets		638	263
Total liabilities		215	22
Our ownership interest		0	0
Other ownership interests		423	241
Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets		567	164
Total liabilities		287	125
Our ownership interest		248	11
Other ownership interests		32	28
Investments [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		264	21
Investments [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		0	0
Investments [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		264	21
Contract Intangible Asset [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		9	9
Contract Intangible Asset [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		9	9
Contract Intangible Asset [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		0	0
Payment Guarantee [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		3	3
Payment Guarantee [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		0	0
Payment Guarantee [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		3	3
Asset Held In Trust Noncurrent [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		9	17
Asset Held In Trust Noncurrent [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		9	17
Asset Held In Trust Noncurrent [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		0	0
Nuclear Decommissioning Asset Retirement Obligation [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Pledged assets for Zion Station decommissioning		113	206
Asset Retirement Obligations, Noncurrent	[1]	$ 104	$ 189
[1]	Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT Funds. The NDT Funds will be utilized to satisfy the tax obligations as gains and losses are realized.

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details) GWh in Millions		Dec. 31, 2030	Jan. 02, 2018GWh	Jul. 29, 2016USD ($)	Nov. 30, 2015MWh	Nov. 06, 2015USD ($)	Sep. 10, 2015USD ($)	May 27, 2015USD ($)	May 07, 2015USD ($)	Mar. 27, 2015USD ($)	Sep. 15, 2014USD ($)	Aug. 21, 2014USD ($)	Mar. 15, 2013USD ($)	Dec. 05, 2012	Nov. 01, 2012MWh	Jul. 31, 2012USD ($)	Apr. 30, 2012MW	Mar. 31, 2013USD ($)	Aug. 31, 2010USD ($)smart_meter	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)smart_meter	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Mar. 23, 2016USD ($)	Dec. 31, 2014USD ($)	Sep. 30, 2014USD ($)	Jun. 30, 2014USD ($)	Dec. 31, 2008USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2016USD ($)smart_meter	Dec. 31, 2017	Dec. 31, 2016USD ($)smart_meter	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Dec. 31, 2013	Dec. 31, 2007USD ($)	Nov. 30, 2010USD ($)	Nov. 30, 2005USD ($)	Jun. 01, 2019	Jun. 01, 2018	Jun. 01, 2017	Jun. 03, 2016USD ($)	Mar. 31, 2015USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent																					$ 14,000,000										$ 14,000,000		$ 14,000,000	$ 90,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount																																	138	(50)	$ 269
Regulatory Assets																					11,388,000,000										11,388,000,000		11,388,000,000	6,824,000,000
Noncurrent regulatory assets																					10,046,000,000										10,046,000,000		10,046,000,000	6,065,000,000
Regulatory liabilities																					602,000,000										602,000,000		602,000,000	369,000,000
Business Combination, Integration Related Costs	[1],[2]																																143,000,000	87,000,000
Regulatory Liabilities																					4,789,000,000										4,789,000,000		4,789,000,000	4,570,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	128,000,000	96,000,000	220,000,000
Other Commitment																					513,000,000		$ 137,000,000							$ 137,000,000	513,000,000		513,000,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					72,000,000										72,000,000		72,000,000	55,000,000
Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					185,000,000										185,000,000		185,000,000	92,000,000
Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					134,000,000										134,000,000		$ 134,000,000	131,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Subsequent contribution to technology innovation trust																$ 4,000,000
Utility annual customer assistance																$ 10,000,000
Term of contract																																	20 years
Low income sector consumption reduction targets Act 129 Phase II																																	0.10%
Renewable energy resources cumulatively increase																																	1.50%
Public Utilities, Requested Rate Increase (Decrease), Amount																																	$ 90,000,000	68,000,000	36,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																	(4,000,000)	(18,000,000)	14,000,000
Regulatory Assets																					1,167,000,000										1,167,000,000		1,167,000,000	1,113,000,000
Noncurrent regulatory assets																					977,000,000										977,000,000		$ 977,000,000	895,000,000
Rate of return on common equity in federal energy regulatory committee complaint																																	11.50%
Regulatory liabilities																					329,000,000										329,000,000		$ 329,000,000	155,000,000
Business Combination, Integration Related Costs	[2],[3]																																(6,000,000)	9,000,000
Regulatory Liabilities																					3,698,000,000										3,698,000,000		3,698,000,000	3,614,000,000
Customer refundable fees, interest																																		1,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	(94,000,000)	(86,000,000)	(22,000,000)
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	$ 91,000,000	$ 34,000,000	$ 78,000,000
Public Utilities, Requested Equity Capital Structure, Percentage																																	8.47%	8.61%	8.62%
Public Utilities, Requested Return on Equity, Percentage																																		11.50%	11.50%
Public Utilities, Interim Rate Increase (Decrease), Amount																																	$ (8,000,000)
SocialCarbonCost																																	16.50
NuclearFacilityPurchaseAmount																																	0.16
LowIncomeEnergyAssistanceContributionAnnual																																	$ 10,000,000
LowIncomeEnergyAssistanceContributionLength																																	5
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					5,000,000										5,000,000		$ 5,000,000	$ 6,000,000
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					141,000,000										141,000,000		141,000,000	52,000,000
Commonwealth Edison Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					60,000,000										60,000,000		60,000,000	53,000,000
Commonwealth Edison Co [Member] | Renewable energy Requirements [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					30,000,000										30,000,000		30,000,000	24,000,000
Commonwealth Edison Co [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					30,000,000										$ 30,000,000		30,000,000	29,000,000
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																	134	85	$ 160
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																					$ 18,000,000												$ (127)	$ 67	$ (232)
Public Utilities, Approved Return on Equity, Percentage																																	8.59%	9.09%	9.20%
Public Utilities, Approved Rate Increase (Decrease), Amount																																	$ 7	$ 152	$ (72)
Public Utilities, Requested Equity Capital Structure, Percentage																																	6.71%	7.05%	7.06%
Public Utilities, Requested Return on Equity, Percentage																																	8.64%	9.14%	9.25%
Commonwealth Edison Co [Member] | Energy Related Derivative [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Term of contract																																	20 years
Commonwealth Edison Co [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
EnergyEfficiencyAnnualCumulativeSavings		21.50%																														6.60%
RenewableEnergyRetailLoad																																								100.00%	100.00%	100.00%
Commonwealth Edison Co [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Renewable energy resources cumulatively increase																																	11.50%
FutureEnergyEfficiencySpending																																	$ 250,000,000
EnergyEfficiencyROEAdjustment																																	20000.00%
Commonwealth Edison Co [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Renewable energy resources cumulatively increase																																	25.00%
FutureEnergyEfficiencySpending																																	$ 400,000,000
ResidentialCustomerRateIncrease																																	25.00%
CommercialAndIndustrialCustomerRateIncrease																																	1.30%
Commonwealth Edison Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
CumulativeAnnualEnergyEfficiencyGoal | GWh			88
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Low income sector consumption reduction targets Act 129 Phase II														4.50%
Smart meters initial phase deployment | smart_meter																					1,600,000										1,600,000		1,600,000
Estimated number of smart meters to be installed | smart_meter																					1,700,000										1,700,000		1,700,000
Total smart grid smart meter investment grant awarded																					$ 200,000,000										$ 200,000,000		$ 200,000,000
Total smart meter spend on investment																					578,000,000										578,000,000		578,000,000
Total smart grid spend on investment																					155,000,000										155,000,000		155,000,000
Smart grid investment grant awarded								$ 275,000,000	$ 534,000,000
Cumulative consumption reduction targets | MWh															1,125,852
Public sector maximum consumption reduction targets Act 129 Phase II														10.00%
Proposed funding Of direct load control program costs													$ 10,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount							$ 127,000,000			$ 190,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										10.95%
Regulatory Assets																					1,710,000,000										1,710,000,000		1,710,000,000	$ 1,617,000,000
Noncurrent regulatory assets																					1,681,000,000										1,681,000,000		1,681,000,000	1,583,000,000
Regulatory liabilities																					127,000,000										127,000,000		127,000,000	112,000,000
Business Combination, Integration Related Costs	[2]																																5,000,000	4,000,000
Regulatory Liabilities																					644,000,000										644,000,000		644,000,000	639,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	11,000,000	13,000,000	$ 0
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					0										0		0	0
PECO Energy Co [Member] | Over Recovered NonBypassable Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					10,000,000										10,000,000		10,000,000
PECO Energy Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					41,000,000										41,000,000		41,000,000	40,000,000
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					56,000,000										56,000,000		56,000,000	60,000,000
PECO Energy Co [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Percentage Tier I alternative energy resources																																				3.50%
Percentage Tier II alternative energy resources																																				6.20%
PECO Energy Co [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Low income sector consumption reduction targets Act 129 Phase II														2.00%
Cumulative consumption reduction targets | MWh					2,100,875
Percentage Tier I alternative energy resources																																				8.00%
Percentage Tier II alternative energy resources																																				10.00%
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase in electric delivery service revenue resulting from rate case settlement or order.																																		22,000,000
Increase in gas delivery service revenue resulting from rate case settlement or order.																																		38,000,000
Estimated number of smart meters to be installed | smart_meter																			2,000,000
Projected investment in smart meters						$ 104,000,000															37,000,000										37,000,000		37,000,000
Annual depreciation expense decrease regulated property												$ 20,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount																																	12,000,000	0	9,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount											$ (68,000,000)															$ (99,000,000)							(3,000,000)	3,000,000	(5,000,000)
Regulatory Assets																					712,000,000										712,000,000		712,000,000	781,000,000
Total projected smart meter smart grid spend																			$ 480,000,000
Reimbursements received from the DOE																			$ 200,000,000
Noncurrent regulatory assets																					504,000,000										504,000,000		504,000,000	514,000,000
Customer Refund Liability, Noncurrent																																											$ 30,000,000
Regulatory liabilities																					50,000,000										50,000,000		50,000,000	38,000,000
Business Combination, Integration Related Costs	[2],[3]																																(1,000,000)	5,000,000
Site contingency, recovery from third party of environmental remediation cost																																						$ 1,000,000	$ 5,000,000
Regulatory Liabilities																					160,000,000										160,000,000		$ 160,000,000	222,000,000
Deferred costs, noncurrent																		$ 16,000,000																										$ 8,000,000
Rate cap imposed on public utility subsidiary																																	15.00%
Deferred purchased power costs																																					$ 306,000,000
Environmental costs recognized, recovery credited to expense																																	$ 81,000,000	73,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	(28,000,000)	(10,000,000)	(17,000,000)
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	$ 86,000,000	$ 9,000,000	$ 25,000,000
Public Utilities, Requested Equity Capital Structure, Percentage																																	8.09%	8.46%	8.53%
Public Utilities, Requested Return on Equity, Percentage																																	10.50%	11.30%	11.30%
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					57,000,000										57,000,000		$ 57,000,000	$ 49,000,000
Baltimore Gas and Electric Company [Member] | Abandonment costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		1,000,000
Baltimore Gas and Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					0										0		0	0
Baltimore Gas and Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					9,000,000										9,000,000		9,000,000	19,000,000
Regulatory Liabilities																					0										0		0	18,000,000
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					2,000,000										2,000,000		2,000,000
Baltimore Gas and Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		14,000,000
Baltimore Gas and Electric Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		5,000,000
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Gas Revenue [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		1,000,000
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Electric Revenue [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		30,000,000
Baltimore Gas and Electric Company [Member] | Under-Recovered Electric Revenue Decoupling [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					1,000,000										1,000,000		1,000,000
Baltimore Gas and Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																	116,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount				$ (44,000,000)
Public Utilities, Requested Return on Equity, Percentage						9.80%
Baltimore Gas and Electric Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																	78,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount				$ (48,000,000)
Public Utilities, Requested Return on Equity, Percentage						9.70%
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent																					14,000,000										14,000,000		14,000,000	90,000,000
Customer Refund Liability, Noncurrent																					20,000,000										20,000,000		20,000,000
Business Combination, Integration Related Costs	[2]																																37,000,000	24,000,000
Unregulated Operating Revenue																																	101,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	50,000,000	82,000,000	$ 61,000,000
Exelon Generation Co L L C [Member] | Conowingo [Member]
Regulatory Matters Additional Narrative Information [Line Items]
License costs																																	28,000,000
Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Business Combination, Integration Related Costs	[2],[3]																																28,000,000	3,000,000
Other Commitment																								$ 444,000,000
Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		2,582,000,000
Noncurrent regulatory assets																																		2,277,000,000
Regulatory liabilities																																		66,000,000
Business Combination, Integration Related Costs	[3]																								$ 29,000,000								19,000,000
Regulatory Liabilities																																		213,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																									$ 11,000,000									6,000,000	28,000,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																																		4,000,000
Pepco Holdings LLC [Member] | Predecessor [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		1,000,000
Pepco Holdings LLC [Member] | Predecessor [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																																		27,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					3,504,000,000										3,504,000,000		3,504,000,000
Noncurrent regulatory assets																					2,851,000,000										2,851,000,000		2,851,000,000
Regulatory liabilities																					79,000,000										79,000,000		79,000,000
Business Combination, Integration Related Costs	[3]																														69,000,000
Regulatory Liabilities																					237,000,000										237,000,000		237,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																															21,000,000
Other Commitment																					323,000,000										323,000,000		323,000,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					10,000,000										10,000,000		10,000,000
Pepco Holdings LLC [Member] | Successor [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					3,000,000										3,000,000		3,000,000
Pepco Holdings LLC [Member] | Successor [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					18,000,000										18,000,000		18,000,000
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Rate of return on common equity																						10.60%
Public Utilities, Requested Rate Increase (Decrease), Amount																						$ 66,000,000											8,000,000	15,000,000	4,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																						(57,000,000)											10,000,000	1,000,000	(6,000,000)
Regulatory Assets																					348,000,000										348,000,000		348,000,000	371,000,000
Noncurrent regulatory assets																					289,000,000										289,000,000		289,000,000	299,000,000
Public Utilities, Approved Return on Equity, Percentage																							0.00%
Regulatory liabilities																					43,000,000										43,000,000		43,000,000	49,000,000
Business Combination, Integration Related Costs	[2]																																20,000,000	2,000,000
Regulatory Liabilities																					140,000,000										140,000,000		140,000,000	160,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	14,000,000	(12,000,000)	(25,000,000)
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	$ 12,000,000	$ 3,000,000	$ 8,000,000
Public Utilities, Requested Return on Equity, Percentage																																	10.50%	11.30%	11.30%
Other Commitment																					86,000,000										86,000,000		$ 86,000,000
Public Utilities, Interim Rate Increase (Decrease), Amount																							$ 2,500,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					4,000,000										4,000,000		4,000,000	$ 3,000,000
Delmarva Power and Light Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					0										0		0	0
Delmarva Power and Light Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					5,000,000										5,000,000		5,000,000	19,000,000
Delmarva Power and Light Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					3,000,000										3,000,000		3,000,000	11,000,000
Delmarva Power and Light Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																																		4,000,000
Delmarva Power and Light Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					2,000,000										2,000,000		2,000,000	4,000,000
Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																		$ 39,000,000					63,000,000				$ 15,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																											9.70%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																							(30,000,000)
Delmarva Power and Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase in gas delivery service revenue resulting from rate case settlement or order.																						0.14
Public Utilities, Requested Rate Increase (Decrease), Amount																							22,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																							(10,000,000)
Delmarva Power and Light Company [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Projected investment in smart grid infrastructure																						5,000,000
Delmarva Power and Light Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Projected investment in smart grid infrastructure																						$ 9,000,000
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																	2,000,000	10,000,000	$ (9,000,000)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																														9.55%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																	10,000,000	3,000,000	1,000,000
Regulatory Assets																					852,000,000										852,000,000		852,000,000	801,000,000
Noncurrent regulatory assets																					690,000,000										690,000,000		690,000,000	661,000,000
Regulatory liabilities																					11,000,000										11,000,000		11,000,000	15,000,000
Regulatory Liabilities																					31,000,000										31,000,000		31,000,000	44,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	23,000,000	(5,000,000)	(7,000,000)
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	$ 27,000,000	$ 1,000,000	$ 10,000,000
Public Utilities, Requested Return on Equity, Percentage																																	10.50%	11.30%	11.30%
Power Plant Output | MW																	661
Capital ProjectFundedByBonds																												$ 375,000,000
CapitalProjectFundedByEntity																												500,000,000
CapitalProjectFundedByAgency																												$ 125,000,000
Other Commitment																					126,000,000										126,000,000		$ 126,000,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					6,000,000										6,000,000		6,000,000	$ 1,000,000
Potomac Electric Power Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					3,000,000										3,000,000		3,000,000	0
Potomac Electric Power Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					8,000,000										8,000,000		8,000,000	16,000,000
Potomac Electric Power Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					5,000,000										5,000,000		5,000,000	14,000,000
Potomac Electric Power Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					3,000,000										3,000,000		3,000,000	2,000,000
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																					53,000,000		86,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																					$ (82,000,000)
Public Utilities, Approved Return on Equity, Percentage																					10.60%
Potomac Electric Power Company [Member] | Subsequent Event [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																				$ (77,000,000)
Potomac Electric Power Company [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Power Plant Output | MW																	650
Potomac Electric Power Company [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Power Plant Output | MW																	700
Proposed Capital Expenditure																														$ 0.105
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount																																	8,000,000	10,000,000	$ 4,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																	14,000,000	(2,000,000)	(3,000,000)
Regulatory Assets																					$ 501,000,000										501,000,000		501,000,000	512,000,000
Noncurrent regulatory assets																					405,000,000										405,000,000		405,000,000	414,000,000
Regulatory liabilities																					25,000,000										25,000,000		25,000,000	18,000,000
Business Combination, Integration Related Costs	[2]																																19,000,000	1,000,000
Regulatory Liabilities																					25,000,000										25,000,000		25,000,000	25,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount																																	6,000,000	(12,000,000)	(7,000,000)
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash																																	$ 11,000,000	$ 3,000,000	$ 9,000,000
Public Utilities, Requested Return on Equity, Percentage																																	10.50%	11.30%	11.30%
Other Commitment																					111,000,000										111,000,000		$ 111,000,000
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes																					0										0		0	$ 0
Atlantic City Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					0										0		0	1,000,000
Atlantic City Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																					5,000,000										5,000,000		5,000,000	8,000,000
Atlantic City Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					4,000,000										4,000,000		4,000,000
Atlantic City Electric Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory liabilities																					1,000,000										1,000,000		1,000,000
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount																																	(45,000,000)
Public Utilities, Interim Rate Increase (Decrease), Amount																					1,000,000		19,000,000	$ 9,000,000
Atlantic City Electric Company [Member] | Subsequent Event [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Interim Rate Increase (Decrease), Amount																				$ 29,000,000
Deferred Project Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					8,000,000										8,000,000		8,000,000	0
Deferred Project Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Deferred Project Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Deferred Project Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Deferred Project Costs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0
Deferred Project Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					8,000,000										8,000,000		8,000,000
Deferred Project Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Rate of return on common equity																													12.95%
Regulatory Assets																					8,000,000								$ 41,000,000		8,000,000		8,000,000	13,000,000
Deferred Project Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Deferred Project Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Under-Recovered Non-Bypassable Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		1,000,000
Smart Meter Related Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					23,000,000										23,000,000		23,000,000
Advanced Metering Infrastructure Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					144,000,000										144,000,000		144,000,000
Advanced Metering Infrastructure Costs [Member] | Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																					3,000,000										3,000,000		3,000,000
Regulatory Assets																					13,000,000										13,000,000		13,000,000
Other Income																					10,000,000
Over-Recovered Natural Gas Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					3,000,000										3,000,000		3,000,000
Abandonment costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					3,000,000										3,000,000		3,000,000
Abandonment costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		3,000,000
Abandonment costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		4,000,000
UnderRecoveredElectricEnergyCosts [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					28,000,000										28,000,000		28,000,000	28,000,000
UnderRecoveredElectricEnergyCosts [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					4,000,000										4,000,000		4,000,000	1,000,000
UnderRecoveredElectricEnergyCosts [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					11,000,000										11,000,000		11,000,000	11,000,000
TransmissionCost [Member] | Commonwealth Edison Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					15,000,000										15,000,000		15,000,000	31,000,000
TransmissionCost [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					4,000,000										4,000,000		4,000,000	12,000,000
TransmissionCost [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					1,000,000										1,000,000		1,000,000	7,000,000
TransmissionCost [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		5,000,000
TransmissionCost [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					6,000,000										6,000,000		6,000,000	2,000,000
Under Recovered Distribution Service Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					188,000,000										188,000,000		188,000,000	189,000,000
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Net regulatory assets																					188,000,000										188,000,000		188,000,000	189,000,000
Regulatory Assets																					188,000,000										188,000,000		188,000,000	189,000,000
Business Combination, Integration Related Costs																																	11,000,000	11,000,000
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					134,000,000										134,000,000		134,000,000	142,000,000
Under Recovered Distribution Service Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Under Recovered Distribution Service Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Under Recovered Distribution Service Costs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0
Under Recovered Distribution Service Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0
Under Recovered Distribution Service Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Under Recovered Distribution Service Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Under Recovered Distribution Service Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Energy Efficiency And Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					621,000,000										621,000,000		621,000,000	279,000,000
Energy Efficiency And Demand Response Programs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Energy Efficiency And Demand Response Programs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					1,000,000										1,000,000		1,000,000	1,000,000
Energy Efficiency And Demand Response Programs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					285,000,000										285,000,000		285,000,000	278,000,000
Energy Efficiency And Demand Response Programs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		401,000,000
Energy Efficiency And Demand Response Programs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					335,000,000										335,000,000		335,000,000
Energy Efficiency And Demand Response Programs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					85,000,000										85,000,000		85,000,000	111,000,000
Energy Efficiency And Demand Response Programs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					250,000,000										250,000,000		250,000,000	289,000,000
Energy Efficiency And Demand Response Programs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		$ 0	1,000,000
Non-severance Merger Integration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		4,000,000
Regulatory Asset, Amortization Period																																	5 years
Pension and Other Postretirement Benefits [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Asset, Amortization Period																																	12 years
Environmental Restoration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					305,000,000										305,000,000		$ 305,000,000	286,000,000
Environmental Restoration Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					278,000,000										278,000,000		278,000,000	255,000,000
Environmental Restoration Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					26,000,000										26,000,000		26,000,000	30,000,000
Environmental Restoration Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					1,000,000										1,000,000		1,000,000	1,000,000
Environmental Restoration Costs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0
Environmental Restoration Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0
Environmental Restoration Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Environmental Restoration Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Environmental Restoration Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Under Recovered Electric Energy And Transmission Costs [Member] | Commonwealth Edison Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		5,000,000
AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					701,000,000										701,000,000		701,000,000	399,000,000
AMI Expenses [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					164,000,000										164,000,000		164,000,000	140,000,000
AMI Expenses [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					49,000,000										49,000,000		$ 49,000,000	63,000,000
Regulatory Asset, Amortization Period																																	10 years
AMI Expenses [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets																					52,000,000										52,000,000		$ 52,000,000
Regulatory Assets																					230,000,000										230,000,000		230,000,000	196,000,000
Noncurrent regulatory assets																					230,000,000										230,000,000		230,000,000
AMI Expenses [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		267,000,000
AMI Expenses [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					258,000,000										258,000,000		258,000,000
AMI Expenses [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					84,000,000										84,000,000		84,000,000	87,000,000
AMI Expenses [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					174,000,000										174,000,000		174,000,000	180,000,000
AMI Expenses [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Merger Integration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					25,000,000										25,000,000		$ 25,000,000	6,000,000
Regulatory Asset, Amortization Period																																	5 years
Merger Integration Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		$ 0	0
Merger Integration Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Merger Integration Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					10,000,000		$ 6,000,000							$ 6,000,000	10,000,000		10,000,000	6,000,000										$ 4,000,000
Merger Integration Costs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		0
Merger Integration Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					15,000,000										15,000,000		15,000,000
Merger Integration Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					4,000,000										4,000,000		4,000,000	0
Merger Integration Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					11,000,000										11,000,000		11,000,000	0
Merger Integration Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	0
Under Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					89,000,000										89,000,000		89,000,000	84,000,000
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					23,000,000										23,000,000		23,000,000	43,000,000
Business Combination, Integration Related Costs																																	8,000,000	7,000,000
Under Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					0										0		0	1,000,000
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					38,000,000										38,000,000		38,000,000	40,000,000
Under Recovered Energy And Transmission Costs [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																																		33,000,000
Under Recovered Energy And Transmission Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					28,000,000										28,000,000		28,000,000
Under Recovered Energy And Transmission Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					5,000,000										5,000,000		5,000,000	11,000,000
Under Recovered Energy And Transmission Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					6,000,000										6,000,000		6,000,000	9,000,000
Under Recovered Energy And Transmission Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					17,000,000										17,000,000		17,000,000	13,000,000
Legacy AMI [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					54,000,000										54,000,000		54,000,000
Legacy AMI [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					14,000,000										14,000,000		14,000,000
Recoverable Smart Meter Related Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					32,000,000										32,000,000		32,000,000
Recoverable Smart Meter Related Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					41,000,000										41,000,000		41,000,000
Recoverable Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					54,000,000										54,000,000		54,000,000	47,000,000
Storm Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					20,000,000										20,000,000		20,000,000	36,000,000
Deferred Income Tax Transmission Related [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					22,000,000										22,000,000		22,000,000	15,000,000
Deferred Income Tax Transmission Related [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					38,000,000										38,000,000		38,000,000	16,000,000
Deferred Income Tax Transmission Related [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					20,000,000										20,000,000		20,000,000	18,000,000
Deferred Income Tax Transmission Related [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					31,000,000										31,000,000		31,000,000	26,000,000
Deferred Income Tax Transmission Related [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					19,000,000										19,000,000		19,000,000	15,000,000
Accelerated Depreciation Costs of Non AMI Meters [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																					162,000,000										$ 162,000,000		$ 162,000,000	$ 137,000,000
Non Utility Deferral [Member] | Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Other Regulatory Assets																					10,000,000
Uncollectible deferral Balance [Member] | Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Other Regulatory Assets																					$ 7,000,000
[1]	Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps.
[2]	The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statements of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. Costs do not include merger commitments discussed above.
[3]	, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, $6 million, $11 million, $4 million, and $16 million incurred at ComEd, BGE, Pepco, DPL and PHI, respectively, that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 3 - Regulatory Matters for more information.

Regulatory Matters - Estimated

Regulatory Matters - Estimated Commitments related to PJM Agreements (Details) - USD ($) $ in Millions	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016
Other Commitments [Line Items]
Total	$ 513	$ 137
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Total			$ 444
Pepco Holdings LLC [Member] | Successor [Member]
Other Commitments [Line Items]
Total	323
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Total	126
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Total	86
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Total	111
Construction Expansion Plans [Member] | Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Total	97
2,015	64
2,016	28
2,017	5
2,018	0
2,019	0
Construction Expansion Plans [Member] | PECO Energy Co [Member]
Other Commitments [Line Items]
Total	34
2,015	14
2,016	10
2,017	7
2,018	2
2,019	1
Construction Expansion Plans [Member] | Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Total	226
2,015	113
2,016	55
2,017	44
2,018	14
2,019	0
Construction Expansion Plans [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Total	104
2,015	6
2,016	39
2,017	40
2,018	19
2,019	0
Construction Expansion Plans [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Total	63
2,015	47
2,016	16
2,017	0
2,018	0
2,019	0
Construction Expansion Plans [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Total	93
2,015	36
2,016	39
2,017	18
2,018	0
2,019	$ 0

Regulatory Matters - Schedule o

Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2016	Mar. 31, 2015	Dec. 31, 2008
Regulated Operations [Abstract]
Regulatory Liability, Current			$ 602	$ 602	$ 369
Regulatory Assets [Line Items]
Current regulatory assets			1,342	1,342	759
Noncurrent regulatory assets			10,046	10,046	6,065
Regulatory Assets			11,388	11,388	6,824
Business Combination, Integration Related Costs	[1],[2]			143	87
AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			477	477	0
UnderFundedStatusDefinedBenefitPostretirement [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1,087	1,087
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4,162	4,162	3,156
Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets			2,016	2,016	1,616
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			701	701	399
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			188	188	189
Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			124	124	47
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			812	812	162
Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1,085	1,085
Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			5	5	9
Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets			111	111	108
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			305	305	286
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			56	56	52
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			260	260	247
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			89	89	84
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			36	36	2
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			10	10	20
Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7	7	87
Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			621	$ 621	279
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period				5 years
Regulatory Assets			25	$ 25	6
Conservation Voltage Reductio [Member]
Regulatory Assets [Line Items]
Regulatory Assets					3
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			27	27	30
Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			49	49	29
CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets			11	11	7
Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			8	8	0
Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			34	34	0
Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			31	31	6
Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			138	138	0
PECO Energy Co [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			127	127	112
Regulatory Assets [Line Items]
Current regulatory assets			29	29	34
Noncurrent regulatory assets			1,681	1,681	1,583
Regulatory Assets			1,710	1,710	1,617
Business Combination, Integration Related Costs	[2]			5	4
PECO Energy Co [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1,583	$ 1,583	1,473
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period				10 years
Regulatory Assets			49	$ 49	63
PECO Energy Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1	1	1
PECO Energy Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets			23	23	22
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			26	26	30
PECO Energy Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	1
PECO Energy Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1	1	1
PECO Energy Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Conservation Voltage Reductio [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
PECO Energy Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			9	9	13
PECO Energy Co [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets			11	11	7
PECO Energy Co [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
PECO Energy Co [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7	7	6
PECO Energy Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Baltimore Gas and Electric Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			50	50	38
Regulatory Assets [Line Items]
Current regulatory assets			208	208	267
Noncurrent regulatory assets			504	504	514
Regulatory Assets			712	712	781
Business Combination, Integration Related Costs	[2],[3]			(1)	5
Baltimore Gas and Electric Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Baltimore Gas and Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4	4	12
Baltimore Gas and Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			28	28	28
Baltimore Gas and Electric Company [Member] | Legacy AMI [Member]
Regulatory Assets [Line Items]
Regulatory Assets			54	54
Baltimore Gas and Electric Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			32	32
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Baltimore Gas and Electric Company [Member] | Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets			98	98	79
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Noncurrent regulatory assets			230	230
Regulatory Assets			230	230	196
Baltimore Gas and Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Baltimore Gas and Electric Company [Member] | Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7	7	8
Baltimore Gas and Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Baltimore Gas and Electric Company [Member] | Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			5	5	9
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets			12	12	19
Baltimore Gas and Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1	1	1
Baltimore Gas and Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Baltimore Gas and Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Baltimore Gas and Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			38	38	40
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1	1	2
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			10	10	20
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7	7	87
Baltimore Gas and Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			285	285	278
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			10	10	6	$ 6	$ 4
Baltimore Gas and Electric Company [Member] | Conservation Voltage Reductio [Member]
Regulatory Assets [Line Items]
Regulatory Assets					3
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			3	3	30
Baltimore Gas and Electric Company [Member] | Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			5	5	3
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs				6
Baltimore Gas and Electric Company [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			38	38	16
Baltimore Gas and Electric Company [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			144	144
Baltimore Gas and Electric Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			3	3
Baltimore Gas and Electric Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Baltimore Gas and Electric Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Baltimore Gas and Electric Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Baltimore Gas and Electric Company [Member] | Abandonment costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			3	3
Baltimore Gas and Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Pepco Holdings LLC [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs	[2],[3]			28	3
Pepco Holdings LLC [Member] | Predecessor [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current					66
Regulatory Assets [Line Items]
Current regulatory assets					305
Noncurrent regulatory assets					2,277
Regulatory Assets					2,582
Business Combination, Integration Related Costs	[3]	$ 29		19
Pepco Holdings LLC [Member] | Successor [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			79	79
Regulatory Assets [Line Items]
Current regulatory assets			653	653
Noncurrent regulatory assets			2,851	2,851
Regulatory Assets			3,504	3,504
Business Combination, Integration Related Costs	[3]		69
Pepco Holdings LLC [Member] | AssetRemovalCosts [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					369
Pepco Holdings LLC [Member] | AssetRemovalCosts [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			477	477
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					910
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Pepco Holdings LLC [Member] | Deferred Income Taxes [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					214
Pepco Holdings LLC [Member] | Deferred Income Taxes [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			260	260
Pepco Holdings LLC [Member] | AMI Expenses [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					267
Pepco Holdings LLC [Member] | AMI Expenses [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			258	258
Pepco Holdings LLC [Member] | Under Recovered Distribution Service Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Pepco Holdings LLC [Member] | Under Recovered Distribution Service Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Pepco Holdings LLC [Member] | Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			81	81
Pepco Holdings LLC [Member] | Debt Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					36
Pepco Holdings LLC [Member] | Fair Value Of Long Term Debt [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Pepco Holdings LLC [Member] | Fair Value Of Long Term Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			671	671
Pepco Holdings LLC [Member] | Fair Value Of Supply Contract [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1,085	1,085
Pepco Holdings LLC [Member] | Severance [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Pepco Holdings LLC [Member] | Severance [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Pepco Holdings LLC [Member] | Asset Retirement Obligations [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					1
Pepco Holdings LLC [Member] | Asset Retirement Obligations [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Pepco Holdings LLC [Member] | Environmental Restoration Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Pepco Holdings LLC [Member] | Environmental Restoration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Pepco Holdings LLC [Member] | Under Recovered Uncollectible Accounts Expense [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Pepco Holdings LLC [Member] | Under Recovered Uncollectible Accounts Expense [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Pepco Holdings LLC [Member] | Renewable Energy And Associated REC [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					6
Pepco Holdings LLC [Member] | Renewable Energy And Associated REC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			2	2
Pepco Holdings LLC [Member] | Under Recovered Energy And Transmission Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					33
Pepco Holdings LLC [Member] | Under Recovered Energy And Transmission Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			28	28
Pepco Holdings LLC [Member] | Deferred Storm Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					43
Pepco Holdings LLC [Member] | Deferred Storm Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			35	35
Pepco Holdings LLC [Member] | Electric Generation Related Regulatory Asset [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Pepco Holdings LLC [Member] | Electric Generation Related Regulatory Asset [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Pepco Holdings LLC [Member] | Rate Stabilization Deferral [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Pepco Holdings LLC [Member] | Rate Stabilization Deferral [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Pepco Holdings LLC [Member] | Energy Efficiency And Demand Response Programs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					401
Pepco Holdings LLC [Member] | Energy Efficiency And Demand Response Programs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			335	335
Pepco Holdings LLC [Member] | Merger Integration Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Pepco Holdings LLC [Member] | Merger Integration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			15	15
Pepco Holdings LLC [Member] | Conservation Voltage Reductio [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Pepco Holdings LLC [Member] | Under Recovered Decoupling Revenue [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					14
Pepco Holdings LLC [Member] | Under Recovered Decoupling Revenue [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			24	24
Pepco Holdings LLC [Member] | Other Assets [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					32
Pepco Holdings LLC [Member] | Other Assets [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			29	29
Pepco Holdings LLC [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs				16
Pepco Holdings LLC [Member] | CAP Arrearage [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Pepco Holdings LLC [Member] | Deferred Project Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Pepco Holdings LLC [Member] | Deferred Project Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			8	8
Pepco Holdings LLC [Member] | Workers Compensation and Long-Term Disability [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					31
Pepco Holdings LLC [Member] | Workers Compensation and Long-Term Disability [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			34	34
Pepco Holdings LLC [Member] | Recoverable Vacation Pay [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					23
Pepco Holdings LLC [Member] | Recoverable Vacation Pay [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			24	24
Pepco Holdings LLC [Member] | Stranded Costs [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Regulatory Assets					202
Pepco Holdings LLC [Member] | Stranded Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			138	138
Potomac Electric Power Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			11	11	15
Regulatory Assets [Line Items]
Current regulatory assets			162	162	140
Noncurrent regulatory assets			690	690	661
Regulatory Assets			852	852	801
Potomac Electric Power Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			134	134	92
Potomac Electric Power Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets					5
Potomac Electric Power Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets			171	171	137
Potomac Electric Power Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			174	174	180
Potomac Electric Power Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			17	17	19
Potomac Electric Power Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Potomac Electric Power Company [Member] | Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	1
Potomac Electric Power Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			6	6	9
Potomac Electric Power Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			12	12	19
Potomac Electric Power Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			250	250	289
Potomac Electric Power Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			11	11	0
Potomac Electric Power Company [Member] | Conservation Voltage Reductio [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Potomac Electric Power Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			21	21	10
Potomac Electric Power Company [Member] | Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			22	22	14
Potomac Electric Power Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs				11
Potomac Electric Power Company [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			31	31	26
Potomac Electric Power Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			34	34	31
Potomac Electric Power Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Potomac Electric Power Company [Member] | Abandonment costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets					4
Potomac Electric Power Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			43	43	49
Regulatory Assets [Line Items]
Current regulatory assets			59	59	72
Noncurrent regulatory assets			289	289	299
Regulatory Assets			348	348	371
Business Combination, Integration Related Costs	[2]			20	2
Delmarva Power and Light Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			88	88	69
Delmarva Power and Light Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1	1	7
Delmarva Power and Light Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4	4	1
Delmarva Power and Light Company [Member] | Legacy AMI [Member]
Regulatory Assets [Line Items]
Regulatory Assets			14	14
Delmarva Power and Light Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			41	41
Delmarva Power and Light Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member] | Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets			38	38	36
Delmarva Power and Light Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			84	84	87
Delmarva Power and Light Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member] | Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			9	9	10
Delmarva Power and Light Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Delmarva Power and Light Company [Member] | Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member] | Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	1
Delmarva Power and Light Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			5	5	11
Delmarva Power and Light Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			5	5	6
Delmarva Power and Light Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			85	85	111
Delmarva Power and Light Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4	4	0
Delmarva Power and Light Company [Member] | Conservation Voltage Reductio [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Delmarva Power and Light Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			3	3	4
Delmarva Power and Light Company [Member] | Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			5	5	9
Delmarva Power and Light Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs				4
Delmarva Power and Light Company [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			20	20	18
Delmarva Power and Light Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			8	8	13			$ 41
Delmarva Power and Light Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Delmarva Power and Light Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			14	14	14
Delmarva Power and Light Company [Member] | Abandonment costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets					3
Delmarva Power and Light Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			25	25	18
Regulatory Assets [Line Items]
Current regulatory assets			96	96	98
Noncurrent regulatory assets			405	405	414
Regulatory Assets			501	501	512
Business Combination, Integration Related Costs	[2]			19	1
Atlantic City Electric Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			255	255	208
Atlantic City Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets			6	6	2
Atlantic City Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			11	11	11
Atlantic City Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets			51	51	41
Atlantic City Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			6	6	7
Atlantic City Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Atlantic City Electric Company [Member] | Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			2	2	5
Atlantic City Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			17	17	13
Atlantic City Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			18	18	18
Atlantic City Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	1
Atlantic City Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Conservation Voltage Reductio [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Atlantic City Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4	4	8
Atlantic City Electric Company [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			19	19	15
Atlantic City Electric Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Atlantic City Electric Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			10	10	9
Atlantic City Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			138	138	202
Commonwealth Edison Co [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			329	329	155
Regulatory Assets [Line Items]
Current regulatory assets			190	190	218
Noncurrent regulatory assets			977	977	895
Regulatory Assets			1,167	1,167	1,113
Business Combination, Integration Related Costs	[2],[3]			(6)	9
Commonwealth Edison Co [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Deferred Income Taxes [Member]
Regulatory Assets [Line Items]
Regulatory Assets			75	75	64
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			164	164	140
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			188	188	189
Business Combination, Integration Related Costs				11	11
Commonwealth Edison Co [Member] | Debt Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			42	42	46
Commonwealth Edison Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Asset Retirement Obligations [Member]
Regulatory Assets [Line Items]
Regulatory Assets			76	76	67
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			278	278	255
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			56	56	52
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			258	258	247
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			23	23	43
Business Combination, Integration Related Costs				8	7
Commonwealth Edison Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Conservation Voltage Reductio [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0
Commonwealth Edison Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Other Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7	7	10
Commonwealth Edison Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs				8
Commonwealth Edison Co [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			22	22	15
Commonwealth Edison Co [Member] | Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			20	20	36
Commonwealth Edison Co [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	0	0
Commonwealth Edison Co [Member] | Recoverable Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			54	54	47
Over Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets			9	9	19
Over Recovered Transmission Costs [Member] | Potomac Electric Power Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			5	5	14
Over Recovered Transmission Costs [Member] | Delmarva Power and Light Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			3	3	11
Over Recovered Transmission Costs [Member] | Atlantic City Electric Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			4	4
Over Recovered Electric Supply Cost [Member] | Potomac Electric Power Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			3	3	2
Over Recovered Electric Supply Cost [Member] | Delmarva Power and Light Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			2	2	4
Over Recovered Electric Supply Cost [Member] | Atlantic City Electric Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			1	1
Over Recovered Electric Supply Cost [Member] | Commonwealth Edison Co [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current			$ 30	$ 30	29
Over-Recovered Natural Gas Costs [Member] | Delmarva Power and Light Company [Member]
Regulated Operations [Abstract]
Regulatory Liability, Current					$ 4
[1]	Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps.
[2]	The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statements of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. Costs do not include merger commitments discussed above.
[3]	, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, $6 million, $11 million, $4 million, and $16 million incurred at ComEd, BGE, Pepco, DPL and PHI, respectively, that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 3 - Regulatory Matters for more information.

Regulatory Matters - Schedule77

Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 4,789	$ 4,570
Regulatory liabilities	602	369
Noncurrent regulatory liabilities	4,187	4,201
Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	47	94
Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	2,607	2,577
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,601	1,527
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	185	92
Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	8	9
Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	76	95
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	20	28
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	134	131
Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	72	16
Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	39
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	644	639
Regulatory liabilities	127	112
Noncurrent regulatory liabilities	517	527
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
PECO Energy Co [Member] | Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	438	405
PECO Energy Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
PECO Energy Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	41	40
PECO Energy Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	8	9
PECO Energy Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	76	95
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	20	28
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	56	60
PECO Energy Co [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
PECO Energy Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	5	2
PECO Energy Co [Member] | Over Recovered NonBypassable Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	10
PECO Energy Co [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	160	222
Regulatory liabilities	50	38
Noncurrent regulatory liabilities	110	184
Baltimore Gas and Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		14
Baltimore Gas and Electric Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		5
Baltimore Gas and Electric Company [Member] | Abandonment costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Baltimore Gas and Electric Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	141	195
Baltimore Gas and Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Baltimore Gas and Electric Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Baltimore Gas and Electric Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Baltimore Gas and Electric Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Baltimore Gas and Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	18
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	19	8
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Gas Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Electric Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		30
Baltimore Gas and Electric Company [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		213
Regulatory liabilities		66
Noncurrent regulatory liabilities		147
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	237
Regulatory liabilities	79
Noncurrent regulatory liabilities	158
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Pepco Holdings LLC [Member] | Asset Retirement Obligations [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Pepco Holdings LLC [Member] | Asset Retirement Obligations [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Pepco Holdings LLC [Member] | Removal Costs [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		150
Pepco Holdings LLC [Member] | Removal Costs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	136
Pepco Holdings LLC [Member] | Energy Efficiency Demand Response Programs [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1
Pepco Holdings LLC [Member] | Energy Efficiency Demand Response Programs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	3
Pepco Holdings LLC [Member] | Dlc Program Cost [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Pepco Holdings LLC [Member] | Dlc Program Cost [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Pepco Holdings LLC [Member] | Electric Transmission And Distribution Tax Repairs [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Pepco Holdings LLC [Member] | Electric Transmission And Distribution Tax Repairs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Pepco Holdings LLC [Member] | Gas Distribution Tax Repairs [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Pepco Holdings LLC [Member] | Gas Distribution Tax Repairs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Pepco Holdings LLC [Member] | Over Recovered Energy And Transmission Costs [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		27
Pepco Holdings LLC [Member] | Over Recovered Energy And Transmission Costs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	18
Pepco Holdings LLC [Member] | Over Recovered Decoupling Revenue [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Pepco Holdings LLC [Member] | Regulatory Liabilities Other [Member] | Predecessor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		35
Pepco Holdings LLC [Member] | Regulatory Liabilities Other [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	41
Pepco Holdings LLC [Member] | Deferred Lease Revenue [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	39
Potomac Electric Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	31	44
Regulatory liabilities	11	15
Noncurrent regulatory liabilities	20	29
Potomac Electric Power Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	5	14
Potomac Electric Power Company [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Potomac Electric Power Company [Member] | Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Potomac Electric Power Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	18	21
Potomac Electric Power Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	3	0
Potomac Electric Power Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Potomac Electric Power Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Potomac Electric Power Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Potomac Electric Power Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	8	16
Potomac Electric Power Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Potomac Electric Power Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	2	7
Potomac Electric Power Company [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Delmarva Power and Light Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	140	160
Regulatory liabilities	43	49
Noncurrent regulatory liabilities	97	111
Delmarva Power and Light Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	3	11
Delmarva Power and Light Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities		4
Delmarva Power and Light Company [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Delmarva Power and Light Company [Member] | Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Delmarva Power and Light Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	118	129
Delmarva Power and Light Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Delmarva Power and Light Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Delmarva Power and Light Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Delmarva Power and Light Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Delmarva Power and Light Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	5	19
Delmarva Power and Light Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Delmarva Power and Light Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	17	12
Delmarva Power and Light Company [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Atlantic City Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	25	25
Regulatory liabilities	25	18
Noncurrent regulatory liabilities	0	7
Atlantic City Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	4
Atlantic City Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Atlantic City Electric Company [Member] | Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Atlantic City Electric Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Atlantic City Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	1
Atlantic City Electric Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Atlantic City Electric Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Atlantic City Electric Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Atlantic City Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	5	8
Atlantic City Electric Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Atlantic City Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	20	16
Atlantic City Electric Company [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	3,698	3,614
Regulatory liabilities	329	155
Noncurrent regulatory liabilities	3,369	3,459
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Commonwealth Edison Co [Member] | Asset Retirement Obligations [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	2,169	2,172
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	1,324	1,332
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	141	52
Commonwealth Edison Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Commonwealth Edison Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Commonwealth Edison Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0	0
Commonwealth Edison Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	60	53
Commonwealth Edison Co [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0
Commonwealth Edison Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	4	5
Commonwealth Edison Co [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	0
Commonwealth Edison Co [Member] | Renewable energy Requirements [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	$ 30	$ 24

Regulatory Matters - Purchase o

Regulatory Matters - Purchase of Receivables Programs (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 313	$ 229
Allowance for Doubtful Accounts Receivable		(37)	(31)	$ (37)
Payments to Acquire Other Receivables, Net		276	198	276
Commonwealth Edison Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		87	103
Allowance for Doubtful Accounts Receivable		(14)	(16)	(14)
Payments to Acquire Other Receivables, Net		73	87	$ 73
PECO Energy Co [Member]
Purchase Of Receivables [Line Items]
Purchase of Receivables, Discount Rate related to Implementation Costs				1.00%
Payments to Acquire Other Receivables	[1]	72	67
Allowance for Doubtful Accounts Receivable		(6)	(7)	$ (6)
Payments to Acquire Other Receivables, Net		66	60	66
Baltimore Gas and Electric Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables	[1]	59	59
Allowance for Doubtful Accounts Receivable	[2]	(4)	(8)	(4)
Payments to Acquire Other Receivables, Net		55	51	55
Pepco Holdings LLC [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		95	100
Allowance for Doubtful Accounts Receivable		(13)	(6)	(13)
Payments to Acquire Other Receivables, Net		82	94	82
Potomac Electric Power Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		63	70
Allowance for Doubtful Accounts Receivable		(7)	(4)	(7)
Payments to Acquire Other Receivables, Net		56	66	56
Delmarva Power and Light Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		10	11
Allowance for Doubtful Accounts Receivable		(2)	0	(2)
Payments to Acquire Other Receivables, Net		8	11	8
Atlantic City Electric Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		22	19
Allowance for Doubtful Accounts Receivable		(4)	(2)	(4)
Payments to Acquire Other Receivables, Net		$ 18	$ 17	$ 18
[1]	(a)For ComEd, BGE, Pepco and DPL, reflects the incremental allowance for uncollectible accounts recorded, which is in addition to the purchase discount. For ComEd, the incremental uncollectible accounts expense is recovered through its Purchase of Receivables with Consolidated Billing tariff.
[2]	PECO’s natural gas POR program became effective on January 1, 2012 and included a 1% discount on purchased receivables in order to recover the implementation costs of the program. The implementation costs were fully recovered and the 1% discount was reset to 0%, effective July 2015.

Regulatory Matters Annual Elect

Regulatory Matters Annual Electric Distribution Filings (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 138	$ (50)	$ 269
Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 90,000,000	$ 68,000,000	$ 36,000,000
Public Utilities, Requested Equity Capital Structure, Percentage		8.47%	8.61%	8.62%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount		$ 4,000,000	$ 18,000,000	$ (14,000,000)
Public Utilities, Approved Rate Increase (Decrease), Amount		94,000,000	$ 86,000,000	$ 22,000,000
Public Utilities, Requested Return on Equity, Percentage			11.50%	11.50%
Electric Distribution [Member] | Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 134	$ 85	$ 160
Public Utilities, Requested Equity Capital Structure, Percentage		6.71%	7.05%	7.06%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ (18,000,000)	$ 127	$ (67)	$ 232
Public Utilities, Approved Equity Capital Structure, Percentage		6.69%	7.02%	7.04%
Public Utilities, Approved Rate Increase (Decrease), Amount		$ (7)	$ (152)	$ 72
Public Utilities, Approved Return on Equity, Percentage		8.59%	9.09%	9.20%
Public Utilities, Requested Return on Equity, Percentage		8.64%	9.14%	9.25%

Regulatory Matters Annual Ele80

Regulatory Matters Annual Electric Transmission Filings (Details) - USD ($)	Jul. 29, 2016	Nov. 06, 2015	Sep. 15, 2014	Mar. 31, 2013	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount											$ 138	$ (50)	$ 269
Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount											$ 90,000,000	$ 68,000,000	$ 36,000,000
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint											11.50%
Public Utilities, Requested Equity Capital Structure, Percentage											8.47%	8.61%	8.62%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount											$ 4,000,000	$ 18,000,000	$ (14,000,000)
Public Utilities, Approved Rate Increase (Decrease), Amount											$ 94,000,000	$ 86,000,000	$ 22,000,000
Public Utilities, Requested Return on Equity, Percentage												11.50%	11.50%
Cap on Equity Component of Rate of Return on Common Equity in Federal Energy Regulatory Committee Complaint											55.00%
Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount											$ 12,000,000	$ 0	$ 9,000,000
Public Utilities, Requested Equity Capital Structure, Percentage											8.09%	8.46%	8.53%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 68,000,000					$ 99,000,000			$ 3,000,000	$ (3,000,000)	$ 5,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount											$ 28,000,000	$ 10,000,000	$ 17,000,000
Public Utilities, Requested Return on Equity, Percentage											10.50%	11.30%	11.30%
Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount											$ 2,000,000	$ 10,000,000	$ (9,000,000)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										9.55%
Public Utilities, Approved Equity Capital Structure, Percentage											7.88%	8.36%	8.60%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount											$ (10,000,000)	$ (3,000,000)	$ (1,000,000)
Public Utilities, Approved Rate Increase (Decrease), Amount											(23,000,000)	5,000,000	7,000,000
Current Year Revenue Adjustment											$ (15,000,000)	$ (2,000,000)	$ 17,000,000
Public Utilities, Requested Return on Equity, Percentage											10.50%	11.30%	11.30%
Delmarva Power and Light Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount						$ 66,000,000					$ 8,000,000	$ 15,000,000	$ 4,000,000
Public Utilities, Approved Return on Equity, Percentage							0.00%
Public Utilities, Approved Equity Capital Structure, Percentage											7.21%	7.80%	8.05%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount						$ 57,000,000					$ (10,000,000)	$ (1,000,000)	$ 6,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount											(14,000,000)	12,000,000	25,000,000
Current Year Revenue Adjustment											$ (12,000,000)	$ (2,000,000)	$ 15,000,000
Public Utilities, Requested Return on Equity, Percentage											10.50%	11.30%	11.30%
Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount											$ 8,000,000	$ 10,000,000	$ 4,000,000
Public Utilities, Approved Equity Capital Structure, Percentage											7.83%	8.51%	8.66%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount											$ (14,000,000)	$ 2,000,000	$ 3,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount											(6,000,000)	12,000,000	7,000,000
Current Year Revenue Adjustment											$ 0	$ 0	$ 0
Public Utilities, Requested Return on Equity, Percentage											10.50%	11.30%	11.30%
Electric Distribution [Member] | Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount											$ 134	$ 85	$ 160
Public Utilities, Approved Return on Equity, Percentage											8.59%	9.09%	9.20%
Public Utilities, Requested Equity Capital Structure, Percentage											6.71%	7.05%	7.06%
Public Utilities, Approved Equity Capital Structure, Percentage											6.69%	7.02%	7.04%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount					$ (18,000,000)						$ 127	$ (67)	$ 232
Public Utilities, Approved Rate Increase (Decrease), Amount											$ (7)	$ (152)	$ 72
Public Utilities, Requested Return on Equity, Percentage											8.64%	9.14%	9.25%
Electric Distribution [Member] | Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount											$ 116,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount	$ 44,000,000
Public Utilities, Requested Return on Equity, Percentage		9.80%
Electric Distribution [Member] | Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 53,000,000		$ 86,000,000
Public Utilities, Approved Return on Equity, Percentage					10.60%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount					$ 82,000,000
Electric Distribution [Member] | Delmarva Power and Light Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 39,000,000			63,000,000		$ 15,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount									9.70%
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount							$ 30,000,000
Electric Distribution [Member] | Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount											$ 45,000,000

Mergers, Acquisitions and Dis81

Mergers, Acquisitions and Dispositions - Narrative (Details) - USD ($)		Jun. 16, 2016	Dec. 31, 2014	Dec. 31, 2017	Dec. 31, 2016		Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016		Mar. 23, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Dec. 31, 2016		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014	Sep. 01, 2016	Mar. 24, 2016
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Asset																									$ 235,000,000
Payments to Acquire Businesses, Gross																				$ 6,934,000,000		$ 40,000,000	$ 386,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets											$ 1,441,000,000
Business Combination, Integration Related Costs	[1],[2]																			143,000,000		87,000,000
Share price											$ 27.25
Other Commitment					$ 513,000,000			$ 137,000,000								$ 137,000,000	$ 513,000,000			513,000,000
Revenues					7,875,000,000		$ 9,002,000,000	6,910,000,000	$ 7,573,000,000			$ 6,702,000,000	$ 7,401,000,000	$ 6,514,000,000	$ 8,830,000,000					31,360,000,000		29,447,000,000	27,429,000,000
Net income																				1,204,000,000		2,250,000,000	1,820,000,000
Merger and integration related costs																				558,000,000			44,000,000
Payments of Debt Restructuring Costs																						22,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent											$ 3,447,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets											248,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets																									4,005,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities											1,515,000,000
Total net assets											7,142,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt											5,636,000,000
Other Intangible Assets [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired																				1,500,000,000
Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Asset																									163,000,000
Payments to Acquire Businesses, Gross																				293,000,000		40,000,000	386,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets			$ 390,000,000																				390,000,000
Business Combination, Integration Related Costs	[2]																			37,000,000		24,000,000
Gain (Loss) on Disposition of Property Plant Equipment					69,000,000			10,000,000								32,000,000
Proceeds from Sale of Productive Assets		$ 37,000,000
Revenues					4,388,000,000		5,035,000,000	3,589,000,000	4,739,000,000			4,294,000,000	4,768,000,000	4,232,000,000	5,840,000,000					17,751,000,000		19,135,000,000	17,393,000,000
Net income																				558,000,000		1,340,000,000	1,019,000,000
Merger and integration related costs																				53,000,000			44,000,000
Payments of Debt Restructuring Costs																						0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent			(16,000,000)																				(16,000,000)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets			50,000,000																				50,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities			(110,000,000)																				(110,000,000)
Asset Impairment Charges					23,000,000
Baltimore Gas and Electric Company [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs	[2],[3]																			(1,000,000)		5,000,000
Revenues					812,000,000		812,000,000	680,000,000	929,000,000			746,000,000	725,000,000	628,000,000	1,036,000,000					3,233,000,000		3,135,000,000	3,165,000,000
Net income																				294,000,000		288,000,000	211,000,000
Merger and integration related costs																				0			0
Payments of Debt Restructuring Costs																						0
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs																				6,000,000
Commonwealth Edison Co [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs	[2],[3]																			(6,000,000)		9,000,000
Other Additional Capital			5,000,000		158,000,000							7,000,000					158,000,000			158,000,000		7,000,000	5,000,000
Revenues					1,223,000,000		1,497,000,000	1,286,000,000	1,249,000,000			1,196,000,000	1,376,000,000	1,148,000,000	1,185,000,000					5,254,000,000		4,905,000,000	4,564,000,000
Net income					80,000,000		37,000,000	145,000,000	115,000,000			87,000,000	149,000,000	99,000,000	90,000,000					378,000,000		426,000,000	408,000,000
Merger and integration related costs																				0			0
Payments of Debt Restructuring Costs																						0
Commonwealth Edison Co [Member] | Regulatory Assets [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs																				8,000,000
PECO Energy Co [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs	[2]																			5,000,000		4,000,000
Revenues					701,000,000		788,000,000	664,000,000	841,000,000			645,000,000	740,000,000	661,000,000	985,000,000					2,994,000,000		3,032,000,000	3,094,000,000
Net income																				438,000,000		378,000,000	352,000,000
Merger and integration related costs																				0			0
Payments of Debt Restructuring Costs																						0
Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs	[2],[3]																			28,000,000		3,000,000
Other Commitment									444,000,000
Pepco Holdings LLC [Member] | Regulatory Assets [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs																				16,000,000
Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross																				33,000,000
Gain (Loss) on Disposition of Property Plant Equipment												37,000,000				$ 8,000,000						9,000,000
Other Commitment					126,000,000												126,000,000			126,000,000
Revenues					491,000,000		635,000,000	509,000,000	551,000,000			488,000,000	592,000,000	504,000,000	545,000,000					2,186,000,000		2,129,000,000	2,055,000,000
Net income																				42,000,000		187,000,000	171,000,000
Merger and integration related costs																				125,000,000			0
Payments of Debt Restructuring Costs																						0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets																									1,700,000,000
Potomac Electric Power Company [Member] | Regulatory Assets [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs																				11,000,000
Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs	[2]																			20,000,000		2,000,000
Gain (Loss) on Disposition of Property Plant Equipment					5,000,000		4,000,000
Other Commitment					86,000,000												86,000,000			86,000,000
Revenues					303,000,000		331,000,000	281,000,000	362,000,000			296,000,000	314,000,000	271,000,000	421,000,000					1,277,000,000		1,302,000,000	1,282,000,000
Net income																				(9,000,000)		76,000,000	104,000,000
Merger and integration related costs																				82,000,000			0
Payments of Debt Restructuring Costs																						0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets																									1,100,000,000
Delmarva Power and Light Company [Member] | Regulatory Assets [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs																				4,000,000
Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs	[2]																			19,000,000		1,000,000
Other Commitment					111,000,000												$ 111,000,000			111,000,000
Revenues					$ 275,000,000		421,000,000	270,000,000	291,000,000			291,000,000	386,000,000	285,000,000	334,000,000					1,257,000,000		1,295,000,000	1,210,000,000
Net income																				(42,000,000)		40,000,000	46,000,000
Merger and integration related costs																				110,000,000			0
Payments of Debt Restructuring Costs																						0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets																									1,200,000,000
Preferred Stock [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross																				180,000,000
Deferred Compensation, Share-based Payments [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	[4]																			$ 29,000,000
Minimum [Member]
Business Acquisition [Line Items]
Ownership interest					20.00%												20.00%			20.00%
Maximum [Member]
Business Acquisition [Line Items]
Ownership interest					50.00%												50.00%			50.00%
Predecessor [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs	[3]										29,000,000									$ 19,000,000
Revenues											1,153,000,000	$ 1,126,000,000	$ 1,336,000,000	$ 1,119,000,000	$ 1,354,000,000							4,935,000,000	4,808,000,000
Net income											19,000,000											327,000,000	242,000,000
Merger and integration related costs											$ 0												0
Payments of Debt Restructuring Costs																						0
Successor [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Asset					$ 400,000,000	[5]											$ 400,000,000	[5]		400,000,000	[5]				$ 235,000,000
Business Combination, Integration Related Costs	[3]																69,000,000
Other Commitment					323,000,000												323,000,000			323,000,000
Fresh-Start Adjustment, Increase (Decrease), Deferred Income Tax Liabilities, Noncurrent					35,000,000												35,000,000			35,000,000
Revenues					1,078,000,000		1,394,000,000	$ 1,066,000,000	$ 105,000,000	[6]							3,643,000,000
Net income																	(61,000,000)
Merger and integration related costs																	317,000,000
Workforce Development [Member]
Business Acquisition [Line Items]
Other Commitment					24,000,000												24,000,000			24,000,000
Workforce Development [Member] | Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Workforce Development [Member] | Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Workforce Development [Member] | Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Workforce Development [Member] | Successor [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Charitable Contributions [Member]
Business Acquisition [Line Items]
Other Commitment					50,000,000												50,000,000			50,000,000
Charitable Contributions [Member] | Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Other Commitment					28,000,000												28,000,000			28,000,000
Charitable Contributions [Member] | Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Other Commitment					12,000,000												12,000,000			12,000,000
Charitable Contributions [Member] | Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Other Commitment					10,000,000												10,000,000			10,000,000
Charitable Contributions [Member] | Successor [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					50,000,000												50,000,000			50,000,000
Energy Efficiency Program [Member]
Business Acquisition [Line Items]
Other Commitment					111,000,000												111,000,000			111,000,000
Energy Efficiency Program [Member] | Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Energy Efficiency Program [Member] | Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Energy Efficiency Program [Member] | Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Energy Efficiency Program [Member] | Successor [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Rate Bill Credits [Member]
Business Acquisition [Line Items]
Other Commitment					259,000,000												259,000,000			259,000,000
Rate Bill Credits [Member] | Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Other Commitment					91,000,000												91,000,000			91,000,000
Rate Bill Credits [Member] | Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Other Commitment					67,000,000												67,000,000			67,000,000
Rate Bill Credits [Member] | Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Other Commitment					101,000,000												101,000,000			101,000,000
Rate Bill Credits [Member] | Successor [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					259,000,000												259,000,000			259,000,000
Commitments [Member] | Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Other Additional Capital					73,000,000												73,000,000			73,000,000
Commitments [Member] | Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Other Additional Capital					46,000,000												46,000,000			46,000,000
Commitments [Member] | Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Other Additional Capital					49,000,000												49,000,000			49,000,000
Delivery System Modernization [Member]
Business Acquisition [Line Items]
Other Commitment					22,000,000												22,000,000			22,000,000
Delivery System Modernization [Member] | Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Delivery System Modernization [Member] | Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Delivery System Modernization [Member] | Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Delivery System Modernization [Member] | Successor [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Green Sustainability Fund [Member]
Business Acquisition [Line Items]
Other Commitment					14,000,000												14,000,000			14,000,000
Green Sustainability Fund [Member] | Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Green Sustainability Fund [Member] | Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Green Sustainability Fund [Member] | Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Green Sustainability Fund [Member] | Successor [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Other1 [Member]
Business Acquisition [Line Items]
Other Commitment					33,000,000												33,000,000			33,000,000
Other1 [Member] | Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Other Commitment					7,000,000												7,000,000			7,000,000
Other1 [Member] | Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Other Commitment					7,000,000												7,000,000			7,000,000
Other1 [Member] | Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Other Commitment					0												0			0
Other1 [Member] | Successor [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					14,000,000												14,000,000			14,000,000
Delmarva Power and Light Company [Member] | Rate Bill Credits [Member]
Business Acquisition [Line Items]
Other Commitment					9,000,000												9,000,000			9,000,000
Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Revenues																				3,785,000,000
Net income																				(66,000,000)
Pepco Holdings LLC [Member] | Preferred Stock [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross																				180,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	[7]																62,000,000
Pepco Holdings LLC [Member] | Successor [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross																	33,000,000
Pepco Holdings LLC [Member] | Successor [Member] | Deferred Compensation, Share-based Payments [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross																	29,000,000
Pepco Holdings LLC [Member] | Commitments [Member]
Business Acquisition [Line Items]
Other Commitment					$ 513,000,000												$ 513,000,000			513,000,000
Pepco Holdings [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross																				7,142,000,000
Intergrys Energy Group Inc [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross			332,000,000
Business Combination, Bargain Purchase, Gain Recognized, Amount			28,000,000
Revenues			386,000,000
Net income			(42,000,000)
Merger and integration related costs																						$ 5,000,000	7,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities			$ 108,000,000																				$ 108,000,000
ConEdision [Member] | Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross																				235,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets																								$ 204,000,000
Payments to Acquire Businesses, Net of Cash Acquired																				22,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets																								1,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets																								9,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities																								65,000,000
Total net assets																								$ 257,000,000
Fitzpatrick [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross							$ 110,000,000
Fitzpatrick [Member] | Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Other Payments to Acquire Businesses																				$ 127,000,000
Fitzpatrick [Member] | Maximum [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs				$ 200,000,000															$ 250,000,000
[1]	Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps.
[2]	The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statements of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. Costs do not include merger commitments discussed above.
[3]	, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, $6 million, $11 million, $4 million, and $16 million incurred at ComEd, BGE, Pepco, DPL and PHI, respectively, that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 3 - Regulatory Matters for more information.
[4]	PHI’s unvested time-based restricted stock units and performance-based restricted stock units issued prior to April 29, 2014 were immediately vested and paid in cash upon the close of the merger. PHI’s remaining unvested time-based restricted stock units as of the close of the merger were cancelled. There were no remaining unvested performance-based restricted stock units as of the close of the merger.
[5]	Distribution to member includes $235 million of net assets associated with PHI's unregulated business interests and $165 million of cash, each of which were distributed by PHI to Exelon.
[6]	Amounts for March 31, 2016 reflect the PHI Successor activity for the period March 24, 2016 to March 31, 2016.
[7]	he liabilities assumed include $29 million for PHI stock-based compensation awards and $33 million for a merger related obligation, each assumed by PHI from Exelon. See Note 4 — Mergers, Acquisitions, and Dispositions.

Mergers, Acquisitions and Dis82

Mergers, Acquisitions and Dispositions - Purchase Price Allocation of Merger with Constellation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2014	Sep. 01, 2016	Mar. 24, 2016	Mar. 23, 2016
Business Acquisition [Line Items]
Current assets				$ 1,441
Property, plant and equipment				11,088
Total assets				21,797
Current liabilities				2,752
Unamortized energy contract liabilities				(1,515)
Other liabilities				(187)
Total liabilities				(14,655)
Total net assets				7,142
_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRetirmentObligations				821
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent				3,447
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets			$ 4,005
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRegulatedAssets				5,015
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets				248
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRegulatedLiabilities				297
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt				$ 5,636
Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Current assets	$ 390
Unamortized energy contracts	115
Current liabilities	(196)
Unamortized energy contract liabilities	110
Other liabilities	(57)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent	(16)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets	50
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRegulatedAssets	184
ConEdision [Member] | Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Current assets		$ 204
Property, plant and equipment		2
Unamortized energy contracts		6
Total assets		322
Unamortized energy contract liabilities		(65)
Total liabilities		(65)
Total net assets		257
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets		9
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRegulatedAssets		100
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets		$ 1
Integrys [Member] | Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Total net assets	360
Business Combination, Bargain Purchase, Gain Recognized, Amount	28
Business Combination, Consideration Transferred	$ 332

Mergers, Acquisitions and Dis83

Mergers, Acquisitions and Dispositions - Summary of Pro-forma Impact of the Merger (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue			$ 32,342	[1]	$ 33,823	[2]
Business Acquisition, Pro Forma Net Income (Loss)			$ 1,562	[1]	$ 2,618	[2]
Business Acquisition, Pro Forma Earnings Per Share, Basic			$ 1.69	[1]	$ 2.85	[2]
Business Acquisition, Pro Forma Earnings Per Share, Diluted			$ 1.69	[1]	$ 2.84	[2]
Merger and integration related costs			$ 558				$ 44
Consolidation, Eliminations [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue			171		$ 559
Merger and integration related costs			680		$ 92
Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Merger and integration related costs			53				44
Pepco Holdings LLC [Member] | Predecessor [Member]
Business Acquisition [Line Items]
Merger and integration related costs	$ 0						0
Pepco Holdings LLC [Member] | Successor [Member]
Business Acquisition [Line Items]
Merger and integration related costs		$ 317
Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Merger and integration related costs			125				0
Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Merger and integration related costs			82				0
Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Merger and integration related costs			$ 110				$ 0
[1]	The amounts above exclude non-recurring costs directly related to the merger of $680 million and intercompany revenue of $171 million for year ended December 31, 2016
[2]	The amounts above exclude non-recurring costs directly related to the merger of $92 million and intercompany revenue of $559 million for the year ended December 31, 2015

Mergers, Acquisitions and Dis84

Mergers, Acquisitions and Dispositions Goodwill Amortization Schedule (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Mar. 24, 2016	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Line Items]
Goodwill, Gross		$ 8,660		$ 4,655	$ 4,655
Goodwill		6,677		$ 2,672	$ 2,672
Goodwill, Acquired During Period		4,016
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets			$ 4,005
Pepco Holdings LLC [Member]
Goodwill [Line Items]
Goodwill, Other Increase (Decrease)	[1]	$ (11)
Atlantic City Electric Company [Member]
Goodwill [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets			$ 1,200
[1]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246NDZFQjI3NUEyQkZDMDk5MDI0QzM5QTYwQjcyQUEwRDkM}

Mergers, Acquisitions and Dis85

Mergers, Acquisitions and Dispositions Merger Integration Related Costs Table (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Business Combination, Integration Related Costs	[1],[2]			$ 143	$ 87
Exelon Generation Co L L C [Member]
Business Combination, Integration Related Costs	[2]			37	24
Commonwealth Edison Co [Member]
Business Combination, Integration Related Costs	[2],[3]			(6)	9
PECO Energy Co [Member]
Business Combination, Integration Related Costs	[2]			5	4
Baltimore Gas and Electric Company [Member]
Business Combination, Integration Related Costs	[2],[3]			(1)	5
Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs	[2],[3]			28	3
Delmarva Power and Light Company [Member]
Business Combination, Integration Related Costs	[2]			20	2
Atlantic City Electric Company [Member]
Business Combination, Integration Related Costs	[2]			19	$ 1
Predecessor [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs	[3]	$ 29		19
Successor [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs	[3]		$ 69
Regulatory Assets [Member] | Commonwealth Edison Co [Member]
Business Combination, Integration Related Costs				8
Regulatory Assets [Member] | Baltimore Gas and Electric Company [Member]
Business Combination, Integration Related Costs				6
Regulatory Assets [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs				16
Regulatory Assets [Member] | Potomac Electric Power Company [Member]
Business Combination, Integration Related Costs				11
Regulatory Assets [Member] | Delmarva Power and Light Company [Member]
Business Combination, Integration Related Costs				$ 4
[1]	Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps.
[2]	The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statements of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. Costs do not include merger commitments discussed above.
[3]	, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, $6 million, $11 million, $4 million, and $16 million incurred at ComEd, BGE, Pepco, DPL and PHI, respectively, that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 3 - Regulatory Matters for more information.

Mergers, Acquisitions and Dis86

Mergers, Acquisitions and Dispositions Merger Transaction Table (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 23, 2016	Dec. 31, 2013
Business Acquisition, Share Price				$ 27.25
Investments	$ 629	$ 639
Shares, Issued	958,778	954,668	894,568		892,034
Payments to Acquire Businesses, Gross	$ 6,934	$ 40	$ 386
Pepco Holdings LLC [Member] | Predecessor [Member]
Investments		80
Goodwill, Other Increase (Decrease)		$ (6)
Pepco Holdings LLC [Member] | Successor [Member]
Investments	133
Pepco Holdings LLC [Member] | Common Stock [Member]
Payments to Acquire Businesses, Gross	$ 6,933

Mergers, Acquisitions and Dis87

Mergers, Acquisitions and Dispositions Commitment and Contingencies Table (Details) - USD ($) $ in Millions	Dec. 31, 2016	Jun. 30, 2016	Mar. 31, 2016
Other Commitments [Line Items]
Other Commitment	$ 513	$ 137
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment			$ 444
Pepco Holdings LLC [Member] | Successor [Member]
Other Commitments [Line Items]
Other Commitment	323
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	126
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	86
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	111
Rate Bill Credits [Member]
Other Commitments [Line Items]
Other Commitment	259
Rate Bill Credits [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Other Commitments [Line Items]
Other Commitment	259
Rate Bill Credits [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	91
Rate Bill Credits [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	67
Rate Bill Credits [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	101
Energy Efficiency Program [Member]
Other Commitments [Line Items]
Other Commitment	111
Energy Efficiency Program [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Other Commitments [Line Items]
Other Commitment	0
Energy Efficiency Program [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Energy Efficiency Program [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Energy Efficiency Program [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Charitable Contributions [Member]
Other Commitments [Line Items]
Other Commitment	50
Charitable Contributions [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Other Commitments [Line Items]
Other Commitment	50
Charitable Contributions [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	28
Charitable Contributions [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	12
Charitable Contributions [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	10
Delivery System Modernization [Member]
Other Commitments [Line Items]
Other Commitment	22
Delivery System Modernization [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Other Commitments [Line Items]
Other Commitment	0
Delivery System Modernization [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Delivery System Modernization [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Delivery System Modernization [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Green Sustainability Fund [Member]
Other Commitments [Line Items]
Other Commitment	14
Green Sustainability Fund [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Other Commitments [Line Items]
Other Commitment	0
Green Sustainability Fund [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Green Sustainability Fund [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Green Sustainability Fund [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Workforce Development [Member]
Other Commitments [Line Items]
Other Commitment	24
Workforce Development [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Other Commitments [Line Items]
Other Commitment	0
Workforce Development [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Workforce Development [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Workforce Development [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Other1 [Member]
Other Commitments [Line Items]
Other Commitment	33
Other1 [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Other Commitments [Line Items]
Other Commitment	14
Other1 [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	7
Other1 [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	7
Other1 [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	$ 0

Investment in Constellation E88

Investment in Constellation Energy Nuclear Group, LLC - Narrative (Details) - USD ($) $ in Millions		Apr. 01, 2014	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jun. 09, 2015
Schedule of Equity Method Investments [Line Items]
Guarantee obligations maximum exposure			$ 50									$ 50
Income (Loss) from Equity Method Investments												(24)	$ (7)	$ 0
Revenues			7,875	$ 9,002	$ 6,910	$ 7,573	$ 6,702	$ 7,401	$ 6,514	$ 8,830		31,360	29,447	27,429
Accumulated other comprehensive loss, net			(2,660)				(2,624)					(2,660)	(2,624)
Operating revenues from affiliates												10	9	23
Parental guarantee provided			75									75
Business Combination, Integration Related Costs	[1],[2]											143	87
Constellation Energy Nuclear Group [Member]
Schedule of Equity Method Investments [Line Items]
Accumulated other comprehensive loss, net		$ 1,500
Constellation Energy Nuclear Group [Member] | Payment Guarantee [Member]
Schedule of Equity Method Investments [Line Items]
Guarantee obligations maximum exposure		245
Constellation Energy Nuclear Group [Member] | Financial Guarantee [Member]
Schedule of Equity Method Investments [Line Items]
Guarantee obligations maximum exposure		165
Exelon Generation Co L L C [Member]
Schedule of Equity Method Investments [Line Items]
Cash distribution paid to member												922	2,474	645
Income (Loss) from Equity Method Investments										19		0	0	(20)
Revenues			4,388	$ 5,035	$ 3,589	$ 4,739	4,294	$ 4,768	$ 4,232	5,840		17,751	19,135	17,393
Accumulated other comprehensive loss, net			(54)				(63)					(54)	(63)
AOCI Tax, Attributable to Parent										77
Allocation of federal tax benefit under tax sharing agreement			94				$ 57				$ 55	94	57	55
Operating revenues from affiliates												1,439	749	779
Parental guarantee provided			21									21
Business Combination, Integration Related Costs	[2]											37	24
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Schedule of Equity Method Investments [Line Items]
Remeasurement gain from derecognition of equity method investment		261
Business combination, step acquisition, equity interest in acquiree, fair value		136
Business acquisition, preexisting relationship, gain (loss) recognized		132
Parental guarantee provided		7	7									7			$ 275
Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group [Member]
Schedule of Equity Method Investments [Line Items]
Revenues										17		548	509
Investment in CENG										1,900
Accumulated other comprehensive loss, net										$ 116
Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group [Member]
Schedule of Equity Method Investments [Line Items]
Due from Affiliates		$ 400	$ 316									$ 316
Debt Instrument, Interest Rate, Stated Percentage		5.25%
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased		85.00%										50.00%
Other Intangible Assets, Net		$ 152
Reduction to net income attributable to noncontrolling interest												$ 20	18
Net Income (Loss) Attributable to Parent												201	(11)
Business Combination, Integration Related Costs												2
Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group [Member] | Payment Guarantee [Member]
Schedule of Equity Method Investments [Line Items]
Due to affiliate		$ 205
Exelon Generation Co L L C [Member] | EDFI [Member] | Constellation Energy Nuclear Group [Member]
Schedule of Equity Method Investments [Line Items]
Operating revenues from affiliates												$ 376	$ 488	$ 137
Electricite De France LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest			49.99%									49.99%
Electricite De France LLC [Member] | Constellation Energy Nuclear Group [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased		15.00%										50.00%
Electricite De France LLC [Member] | Constellation Energy Nuclear Group [Member] | Financial Guarantee [Member]
Schedule of Equity Method Investments [Line Items]
Guarantee obligations maximum exposure		$ 145
Constellation Energy Group LLC [Member]
Schedule of Equity Method Investments [Line Items]
Investment Interest Rate											8.50%
Constellation Energy Group LLC [Member] | EDFI [Member]
Schedule of Equity Method Investments [Line Items]
Cash distribution paid to member		$ 400
[1]	Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps.
[2]	The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statements of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. Costs do not include merger commitments discussed above.

Investment in Constellation E89

Investment in Constellation Energy Nuclear Group, LLC - Schedule of Assets and Liabilities of CENG (Details) - USD ($) $ in Millions	Mar. 23, 2016	Dec. 31, 2014	Apr. 01, 2014
Business Acquisition [Line Items]
Current assets	$ 1,441
Property, plant and equipment	11,088
Total assets	21,797
Current liabilities	2,752
Unamortized energy contract liabilities	1,515
Other liabilities	187
Total liabilities	14,655
Total net assets	$ 7,142
Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Current assets		$ 390
Current liabilities		(196)
Unamortized energy contract liabilities		(110)
Other liabilities		$ 57
Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group [Member]
Business Acquisition [Line Items]
Current assets			$ 499
Nuclear decommissioning trust fund			1,955
Property, plant and equipment			3,073
Nuclear fuel			482
Other assets			10
Total assets			6,019
Current liabilities			237
Asset retirement obligation			1,816
Pension and other employee benefit obligations			281
Unamortized energy contract liabilities			171
Other liabilities			114
Total liabilities			2,619
Total net assets			$ 3,400

Accounts Receivable Schedule of

Accounts Receivable Schedule of Estimated Unbilled Revenues (Details) - USD ($)		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		$ 1,673,000,000		$ 1,203,000,000
Allowance for uncollectible accounts	[1]	(334,000,000)		(284,000,000)
Regulatory Assets		11,388,000,000		6,824,000,000
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues	[2]	910,000,000		732,000,000
Allowance for uncollectible accounts	[1]	(91,000,000)		(77,000,000)
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		219,000,000		218,000,000
Allowance for uncollectible accounts	[1]	(70,000,000)		(75,000,000)
Regulatory Assets		1,167,000,000		1,113,000,000
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		140,000,000		105,000,000
Allowance for uncollectible accounts	[1],[3]	(61,000,000)		(83,000,000)
Allowance for Doubtful Accounts Receivable, Noncurrent		23,000,000		8,000,000
Regulatory Assets		1,710,000,000		1,617,000,000
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		182,000,000		148,000,000
Allowance for uncollectible accounts	[1]	(32,000,000)		(49,000,000)
Regulatory Assets		712,000,000		781,000,000
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Charged to Costs and Expenses		10,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		222,000,000
Allowance for uncollectible accounts	[1],[4]	(80,000,000)
Regulatory Assets		3,504,000,000
Pepco Holdings LLC [Member] | Predecessor [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues				177,000,000
Allowance for uncollectible accounts	[1]			(56,000,000)
Regulatory Assets				2,582,000,000
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		123,000,000		93,000,000
Allowance for uncollectible accounts	[1]	(29,000,000)	[4]	(17,000,000)
Regulatory Assets		852,000,000		801,000,000
Charged to Costs and Expenses		6,000,000
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		58,000,000		45,000,000
Allowance for uncollectible accounts	[1]	(24,000,000)	[4]	(17,000,000)
Regulatory Assets		348,000,000		371,000,000
Charged to Costs and Expenses		4,000,000
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenues		41,000,000		39,000,000
Allowance for uncollectible accounts	[1]	(27,000,000)	[4]	(17,000,000)
Regulatory Assets		501,000,000		$ 512,000,000
PHI Merger [Member] | Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for uncollectible accounts		(30,000,000)
Regulatory Assets		20,000,000
PHI Merger [Member] | Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for uncollectible accounts		(14,000,000)
Regulatory Assets		8,000,000
PHI Merger [Member] | Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for uncollectible accounts		(8,000,000)
Regulatory Assets		4,000,000
PHI Merger [Member] | Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for uncollectible accounts		(8,000,000)
Regulatory Assets		$ 8,000,000
[1]	Includes the allowance for uncollectible accounts on customer and other accounts receivable.
[2]	Represents unbilled portion of retail receivables estimated under Exelon’s unbilled critical accounting policy.
[3]	Excludes the non-current allowance for uncollectible accounts of $23 million and $8 million at December 31, 2016 and 2015, respectively, related to PECO’s current installment plan receivables described below.
[4]	At December 31, 2016, as explained in Note 1—Significant Accounting Policies, PHI, Pepco, DPL and ACE estimated the allowance for uncollectible accounts on customer receivables by applying loss rates to the outstanding receivable balance by risk segment. The change in estimate resulted in an overall increase of $30 million, $14 million, $8 million, and $8 million in the allowance for uncollectible accounts with $20 million, $8 million, $4 million, and $8 million deferred as a regulatory asset on PHI's, Pepco's, DPL's and ACE's Consolidated Balance Sheets at December 31, 2016, respectively. This also resulted in a $10 million, $6 million, and $4 million pre-tax charge to provision for uncollectible accounts expense for the year ended December 31, 2016, which is included in Operating and maintenance expense on PHI's, Pepco's, and DPL's Consolidated Statements of Operations and Comprehensive Income, respectively.

Accounts Receivable Narrative (

Accounts Receivable Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Installment plan receivables	$ 9	$ 15
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Installment plan receivables uncollectible accounts reserve	13	15
Risk Level, Low [Member] | PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Installment plan receivables uncollectible accounts reserve	1	1
Risk Level, Medium [Member] | PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Installment plan receivables uncollectible accounts reserve	3	3
Risk Level, High [Member] | PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Installment plan receivables uncollectible accounts reserve	$ 9	$ 11

Property, Plant and Equipment S

Property, Plant and Equipment Summary of Property, Plant and Equipment (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 90,724	$ 73,814
Less: accumulated depreciation	[1]	19,169	16,375
Property, plant and equipment, net		71,555	57,439
Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 45,698	32,546
Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		90 years
Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 27,193	25,615
Electric—generation | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		3 years
Electric—generation | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		56 years
Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 4,642	3,864
Gas Distribution Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Gas Distribution Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		90 years
Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 1,312	1,149
Common—electric and gas | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		4 years
Common—electric and gas | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		50 years
Nuclear Fuel
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[2]	$ 6,546	6,384
Nuclear Fuel | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		1 year
Nuclear Fuel | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		8 years
Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 4,306	3,075
Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[3]	$ 1,027	1,181
Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		3 years
Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		50 years
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 36,147	34,482
Less: accumulated depreciation	[4]	10,562	8,639
Property, plant and equipment, net		25,585	25,843
Nuclear fuel - work in progress		1,326	1,266
Capital Leases, Balance Sheet, Assets by Major Class, Net		10	13
Capital Leased Assets, Gross		52
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation		42	39
Capitalized Costs, Oil and Gas Producing Activities, Net			266
Property, Plant, and Equipment, Fair Value Disclosure		17	146
Exelon Generation Co L L C [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 27,193	25,615
Exelon Generation Co L L C [Member] | Electric—generation | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		3 years
Exelon Generation Co L L C [Member] | Electric—generation | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		56 years
Exelon Generation Co L L C [Member] | Nuclear Fuel
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[5]	$ 6,546	6,384
Less: accumulated depreciation		$ 3,186	2,861
Exelon Generation Co L L C [Member] | Nuclear Fuel | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		1 year
Exelon Generation Co L L C [Member] | Nuclear Fuel | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		8 years
Exelon Generation Co L L C [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 2,332	2,017
Exelon Generation Co L L C [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[6]	$ 76	466
Average Service Life (years)		4 years
Commonwealth Edison Co [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 23,272	21,212
Less: accumulated depreciation		3,937	3,710
Property, plant and equipment, net		19,335	17,502
Capital Leases, Balance Sheet, Assets by Major Class, Net		7
Capital Leased Assets, Gross		8
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation		1
Plant Held for Future Use Amount		60
Commonwealth Edison Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 22,636	20,576
Commonwealth Edison Co [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Commonwealth Edison Co [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		80 years
Commonwealth Edison Co [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 569	572
Commonwealth Edison Co [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[7],[8]	$ 67	64
Commonwealth Edison Co [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		37 years
Commonwealth Edison Co [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		50 years
PECO Energy Co [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 10,818	10,242
Less: accumulated depreciation		3,253	3,101
Property, plant and equipment, net		7,565	7,141
Plant Held for Future Use Amount		21
PECO Energy Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 7,591	7,230
PECO Energy Co [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
PECO Energy Co [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		65 years
PECO Energy Co [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 2,348	2,206
PECO Energy Co [Member] | Gas Distribution Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
PECO Energy Co [Member] | Gas Distribution Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		70 years
PECO Energy Co [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 670	631
PECO Energy Co [Member] | Common—electric and gas | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
PECO Energy Co [Member] | Common—electric and gas | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		50 years
PECO Energy Co [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 188	154
PECO Energy Co [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[9]	$ 21	21
Average Service Life (years)		50 years
Baltimore Gas and Electric Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 10,294	9,613
Less: accumulated depreciation		3,254	3,016
Property, plant and equipment, net		7,040	6,597
Plant Held for Future Use Amount		32
Baltimore Gas and Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 7,067	6,663
Baltimore Gas and Electric Company [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Baltimore Gas and Electric Company [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		90 years
Baltimore Gas and Electric Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 2,170	1,951
Baltimore Gas and Electric Company [Member] | Gas Distribution Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Baltimore Gas and Electric Company [Member] | Gas Distribution Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		90 years
Baltimore Gas and Electric Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 707	655
Baltimore Gas and Electric Company [Member] | Common—electric and gas | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Baltimore Gas and Electric Company [Member] | Common—electric and gas | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		40 years
Baltimore Gas and Electric Company [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 318	312
Baltimore Gas and Electric Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[10]	$ 32	32
Average Service Life (years)		20 years
Pepco Holdings LLC [Member] | Successor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 11,793
Less: accumulated depreciation		195
Property, plant and equipment, net		11,598
Pepco Holdings LLC [Member] | Predecessor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment			16,204
Less: accumulated depreciation			5,340
Property, plant and equipment, net			10,864
Pepco Holdings LLC [Member] | Electric—transmission and distribution | Successor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 10,315
Pepco Holdings LLC [Member] | Electric—transmission and distribution | Predecessor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment			14,563
Pepco Holdings LLC [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Pepco Holdings LLC [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		86 years
Pepco Holdings LLC [Member] | Gas Distribution Equipment | Successor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 414
Pepco Holdings LLC [Member] | Gas Distribution Equipment | Predecessor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment			547
Pepco Holdings LLC [Member] | Gas Distribution Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Pepco Holdings LLC [Member] | Gas Distribution Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		75 years
Pepco Holdings LLC [Member] | Common—electric and gas | Successor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 65
Pepco Holdings LLC [Member] | Common—electric and gas | Predecessor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment			164
Pepco Holdings LLC [Member] | Common—electric and gas | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		4 years
Pepco Holdings LLC [Member] | Common—electric and gas | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		40 years
Pepco Holdings LLC [Member] | Construction work in progress | Successor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 892
Pepco Holdings LLC [Member] | Construction work in progress | Predecessor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment			591
Pepco Holdings LLC [Member] | Other Property Plant and Equipment | Successor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[11]	$ 107
Pepco Holdings LLC [Member] | Other Property Plant and Equipment | Predecessor [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[11]		339
Pepco Holdings LLC [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		3 years
Pepco Holdings LLC [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		43 years
Potomac Electric Power Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 8,621	8,091
Less: accumulated depreciation		3,050	2,929
Property, plant and equipment, net		5,571	5,162
Plant Held for Future Use Amount		66
Potomac Electric Power Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 8,018	7,682
Potomac Electric Power Company [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Potomac Electric Power Company [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		86 years
Potomac Electric Power Company [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 537	318
Potomac Electric Power Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[12]	$ 66	91
Potomac Electric Power Company [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		10 years
Potomac Electric Power Company [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		33 years
Delmarva Power and Light Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 4,448	4,209
Less: accumulated depreciation		1,175	1,139
Property, plant and equipment, net		3,273	3,070
Plant Held for Future Use Amount		16
Delmarva Power and Light Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 3,574	3,431
Delmarva Power and Light Company [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Delmarva Power and Light Company [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		68 years
Delmarva Power and Light Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 580	547
Delmarva Power and Light Company [Member] | Gas Distribution Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Delmarva Power and Light Company [Member] | Gas Distribution Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		75 years
Delmarva Power and Light Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 115	108
Delmarva Power and Light Company [Member] | Common—electric and gas | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		4 years
Delmarva Power and Light Company [Member] | Common—electric and gas | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		40 years
Delmarva Power and Light Company [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 163	107
Delmarva Power and Light Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[13]	$ 16	16
Delmarva Power and Light Company [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		10 years
Delmarva Power and Light Company [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		43 years
Atlantic City Electric Company [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 3,537	3,291
Less: accumulated depreciation		1,016	969
Property, plant and equipment, net		2,521	2,322
Plant Held for Future Use Amount		27
Atlantic City Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 3,341	3,105
Atlantic City Electric Company [Member] | Electric—transmission and distribution | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		5 years
Atlantic City Electric Company [Member] | Electric—transmission and distribution | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		55 years
Atlantic City Electric Company [Member] | Construction work in progress
Property, Plant and Equipment [Line Items]
Total property, plant and equipment		$ 169	158
Atlantic City Electric Company [Member] | Other Property Plant and Equipment
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	[14]	$ 27	$ 28
Atlantic City Electric Company [Member] | Other Property Plant and Equipment | Minimum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		13 years
Atlantic City Electric Company [Member] | Other Property Plant and Equipment | Maximum [Member]
Property, Plant and Equipment [Line Items]
Average Service Life (years)		15 years
[1]	Includes accumulated amortization of nuclear fuel in the reactor core at Generation of $3,186 million and $2,861 million as of December 31, 2016 and 2015, respectively
[2]	Includes nuclear fuel that is in the fabrication and installation phase of $1,326 million and $1,266 million at December 31, 2016 and 2015, respectively.
[3]	Includes Generation’s buildings under capital lease with a net carrying value of $10 million and $13 million at December 31, 2016 and 2015, respectively. The original cost basis of the buildings was $52 million, and total accumulated amortization was $42 million and $39 million, as of December 31, 2016 and 2015, respectively. Also includes ComEd’s buildings under capital lease with a net carrying value at both December 31, 2016 and 2015, of $7 million. The original cost basis of the buildings was $8 million and total accumulated amortization was $1 million as of both December 31, 2016 and 2015. Includes land held for future use and non utility property at ComEd, PECO, BGE, Pepco, DPL, and ACE of $60 million, $21 million, $32 million, $66 million, $16 million, and $27 million, respectively, at December 31, 2016. At December 31, 2015 these balances also include capitalized acquisition, development and exploration costs of $266 million related to oil and gas production activities at Generation, see Note 4—Mergers, Acquisitions, and Dispositions for additional information regarding the sale of upstream assets. Includes the original cost and progress payments associated with Generation’s turbine equipment held for future use with a carrying value of $17 million and $146 million at December 31, 2016 and 2015, respectively.
[4]	Includes accumulated amortization of nuclear fuel in the reactor core of $3,186 million and $2,861 million as of December 31, 2016 and 2015, respectively
[5]	Includes nuclear fuel that is in the fabrication and installation phase of $1,326 million and $1,266 million at December 31, 2016 and 2015, respectively
[6]	Includes buildings under capital lease with a net carrying value of $10 million and $13 million at December 31, 2016 and 2015, respectively. The original cost basis of the buildings was $52 million, and total accumulated amortization was $42 million and $39 million, as of December 31, 2016 and 2015, respectively. At December 31, 2015 these balances also include capitalized acquisition, development and exploration costs of $266 million related to oil and gas production activities at Generation, see Note 4—Mergers, Acquisitions, and Dispositions for additional information regarding the sale of upstream assets. Includes the original cost and progress payments associated with Generation’s turbine equipment held for future use with a carrying value of $17 million and $146 million at December 31, 2016 and 2015, respectively.
[7]	Includes buildings under capital lease with a net carrying value at both December 31, 2016 and 2015 of $7 million. The original cost basis of the buildings was $8 million and total accumulated amortization was $1 million as of both December 31, 2016 and 2015
[8]	Includes land held for future use and non-utility property.
[9]	Represents land held for future use and non-utility property.
[10]	Represents land held for future use and non-utility property
[11]	Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien.
[12]	Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien.
[13]	Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien.
[14]	Represents plant held for future use and non-utility property. Utility plant is generally subject to a first mortgage lien.

Property, Plant and Equipment A

Property, Plant and Equipment Annual Depreciation Provisions as Percentage of Average Service Life (Details)	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.73%		2.83%	2.93%
Electric—generation
Property, Plant and Equipment [Line Items]
Annual depreciation rate	5.94%	[1]	3.47%	3.50%
Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.17%		2.17%	2.13%
Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	7.41%		7.79%	7.32%
PECO Energy Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.32%		2.39%	2.55%
PECO Energy Co [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	1.82%		1.87%	1.84%
PECO Energy Co [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	5.11%		5.16%	5.16%
Baltimore Gas and Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.56%		2.62%	2.96%
Baltimore Gas and Electric Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.45%		2.50%	2.47%
Baltimore Gas and Electric Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	9.45%		10.35%	9.49%
Pepco Holdings LLC [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.52%		2.48%	2.42%
Pepco Holdings LLC [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.57%		2.55%	2.48%
Pepco Holdings LLC [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	8.12%		5.19%	4.55%
Delmarva Power and Light Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.49%		2.44%	2.41%
Delmarva Power and Light Company [Member] | Gas Distribution Equipment
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.57%		2.55%	2.48%
Delmarva Power and Light Company [Member] | Common—electric and gas
Property, Plant and Equipment [Line Items]
Annual depreciation rate	4.99%		4.24%	4.08%
[1]	See Note 9—Early Nuclear Plant Retirements for additional information on the accelerated net depreciation and amortization of Clinton and Quad Cities.

Property, Plant and Equipment -

Property, Plant and Equipment - Narrative (Details)	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Electric—generation
Property, Plant and Equipment [Line Items]
Annual depreciation rate	5.94%	[1]	3.47%	3.50%
Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.73%		2.83%	2.93%
Exelon Generation Co L L C [Member] | Electric—generation
Property, Plant and Equipment [Line Items]
Annual depreciation rate	5.94%		3.47%	3.50%
Commonwealth Edison Co [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	3.03%		3.03%	3.05%
Potomac Electric Power Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.17%		2.13%	2.10%
Atlantic City Electric Company [Member] | Electric—transmission and distribution
Property, Plant and Equipment [Line Items]
Annual depreciation rate	2.45%		2.46%	2.48%
[1]	See Note 9—Early Nuclear Plant Retirements for additional information on the accelerated net depreciation and amortization of Clinton and Quad Cities.

Impairment of Long-lived Asse95

Impairment of Long-lived Assets - Narrative (Details) - USD ($) $ in Millions		May 31, 2014	Feb. 26, 2014	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Capital Leases Net Investment In Direct Financing Leases [Line Items]
Impairment charges					$ 24
Interest costs incurred	[1],[2]				1,678	$ 1,170	$ 1,144
Estimated residual value of leased assets					356	639
Proceeds From Lease Termination			$ 335		360
Capital leases net investment in direct financing leases writeoff			$ 336			352
Pre Tax Loss						1
Exelon Generation Co L L C [Member]
Capital Leases Net Investment In Direct Financing Leases [Line Items]
Carrying amount of long lived assets to be written down		$ 151			60	1,000
Assets held for sale		65			24		556
Impairment charges		$ 86		$ 119	36	450	15
Interest costs incurred	[1],[2]				472	445	419
Baltimore Gas and Electric Company [Member]
Capital Leases Net Investment In Direct Financing Leases [Line Items]
Interest costs incurred	[1]				$ 114	113	118
Constellation Energy Group LLC [Member]
Capital Leases Net Investment In Direct Financing Leases [Line Items]
Impairment charges						$ 5	$ 124
[1]	Successor PredecessorPHIMarch 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014Total incurred interest(b)$207 $68 $289 $277Credits to AFUDC debt and equity35 10 23 21
[2]	Successor PredecessorPHIMarch 24, 2016 to December 31, 2016 January 1, 2016 to March 23, 2016 For the Year Ended December 31, 2015 For the Year Ended December 31, 2014Total incurred interest(b)$207 $68 $289 $277Credits to AFUDC debt and equity35 10 23 21

Impairment of Long-lived Asse96

Impairment of Long-lived Assets - Components of Net Investment in Long-term Leases (Details) - USD ($) $ in Millions		May 31, 2014	Feb. 26, 2014	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Impairment or Disposal of Tangible Assets Disclosure [Abstract]
Capital Leases, Net Investment in Direct Financing Leases, Unguaranteed Residual Values of Leased Property					$ 356			$ 356	$ 639
Less: unearned income									287
Net investment in long-term leases	[1]								358
Capital Leases Net Investment In Direct Financing Leases [Line Items]
Tangible Asset Impairment Charges								24
Capital Leases, Net Investment in Direct Financing Leases, Unguaranteed Residual Values of Leased Property					356			356	639
Proceeds From Lease Termination			$ 335					360
Gain (Loss) on Contract Termination								4
Exelon Generation Co L L C [Member]
Impairment or Disposal of Tangible Assets Disclosure [Abstract]
Net investment in long-term leases	[1]								6
Capital Leases Net Investment In Direct Financing Leases [Line Items]
Tangible Asset Impairment Charges		$ 86		$ 119				36	450	$ 15
Assets held for sale		$ 65			24			$ 24		556
Gain (Loss) on Disposition of Property Plant Equipment					$ 69	$ 10	$ 32
Constellation Energy Group LLC [Member]
Capital Leases Net Investment In Direct Financing Leases [Line Items]
Tangible Asset Impairment Charges									$ 5	$ 124
[1]	Represents direct financing lease investments.

Early Nuclear Plant Retiremen97

Early Nuclear Plant Retirements Early Nuclear Plant Retirements (Details) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross			$ 1,274	$ 1,104
Property, plant and equipment, net			71,555	57,439
Nuclear Fuel Amortization	[1]		1,159	1,116	$ 1,073
Asset Retirement Obligation, Accretion Expense	[2]		446	398	345
Property, plant and equipment			3,477	2,227	2,080
Other Nonoperating Income (Expense)			413	(46)	455
Facility Closing [Member]
Property, Plant and Equipment [Line Items]
Other Expenses			688
Quad Cities [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross			39
Nuclear Fuel, Net of Amortization			83
Construction work in progress			37
Asset Retirement Obligation			(565)
Property, plant and equipment, net			1,015
Nuclear Plant [Member]
Property, Plant and Equipment [Line Items]
Other Expenses			688
Nuclear Fuel Amortization			60
Asset Retirement Obligation, Accretion Expense			2
Property, plant and equipment		$ 146	712
Other Nonoperating Income (Expense)			(86)
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross			935	880
Property, plant and equipment, net			25,585	25,843
Nuclear Fuel Amortization	[1]		1,159	1,116	1,073
Asset Retirement Obligation, Accretion Expense	[2]		446	397	345
Property, plant and equipment			1,835	1,007	922
Other Nonoperating Income (Expense)			$ 401	$ (60)	$ 406
[1]	Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[2]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.

Early Nuclear Plant Retiremen98

Early Nuclear Plant Retirements Early Nuclear Plant Retirements table (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Regulatory Assets		$ 11,388	$ 6,824
Asset Retirement Obligation, Accretion Expense	[1]	446	398	$ 345
Property, plant and equipment		3,477	2,227	2,080
Nuclear Fuel Amortization	[2]	1,159	1,116	1,073
Quad Cities [Member]
Property, Plant and Equipment [Line Items]
Asset Retirement Obligation		565
Facility Closing [Member]
Property, Plant and Equipment [Line Items]
Other Expenses		688
Delmarva Power and Light Company [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets		348	371
Asset Retirement Obligation, Accretion Expense	[1]	0	0	0
Property, plant and equipment		110	103	94
Nuclear Fuel Amortization	[2]	0	0	0
Commonwealth Edison Co [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets		1,167	1,113
Asset Retirement Obligation, Accretion Expense	[1]	0	0	0
Property, plant and equipment		708	635	588
Nuclear Fuel Amortization	[2]	0	0	$ 0
Accelerated Depreciation Costs of Non AMI Meters [Member] | Commonwealth Edison Co [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets		162	137
Deferred Income Tax Transmission Related [Member] | Delmarva Power and Light Company [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets		20	18
Deferred Income Tax Transmission Related [Member] | Commonwealth Edison Co [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets		22	$ 15
Recoverable Smart Meter Related Costs [Member] | Delmarva Power and Light Company [Member]
Property, Plant and Equipment [Line Items]
Regulatory Assets		$ 41
[1]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[2]	Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.

Jointly Owned Electric Utilit99

Jointly Owned Electric Utility Plant - Ownership Interests in Jointly Owned Electric Plants and Transmission Facilities (Details) $ in Millions		12 Months Ended
		Dec. 31, 2016USD ($)Vmi	Dec. 31, 2015USD ($)
Quad Cities [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Construction work in progress		$ 37
Conemaugh [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Substation capacity | V		500
Pennsylvania [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Miles of transmission voltage lines | mi		127
Transmission line capacity | V		500
Delaware And New Jersey [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Miles of transmission voltage lines | mi		151.3
Transmission line capacity | V		500
Delaware River Crossing [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Miles of transmission voltage lines | mi		2.5
Transmission line capacity | V		500
New Freedom Switching [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Transmission line capacity | V		500
Electric Transmission [Member] | Pennsylvania [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Plant	[1],[2]	$ 27	$ 27
Accumulated depreciation	[1],[2]	15	15
Construction work in progress	[2]	0	0
Electric Transmission [Member] | Delaware And New Jersey [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Plant	[1],[3]	97	93
Accumulated depreciation	[1],[3]	52	52
Construction work in progress	[3]	0	0
Other Service [Member] | Other Locations [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Plant	[1],[4]	15	15
Accumulated depreciation	[1],[4]	13	13
Construction work in progress	[4]	$ 0	0
Exelon Generation Co L L C [Member] | Merrill Creek [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		44.24%
Exelon Generation Co L L C [Member] | Nuclear Plant [Member] | Quad Cities [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		75.00%
Plant	[1]	$ 1,054	1,035
Accumulated depreciation	[1]	515	309
Construction work in progress		$ 0	11
Exelon Generation Co L L C [Member] | Nuclear Plant [Member] | Peach Bottom [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		50.00%
Plant	[1]	$ 1,384	1,345
Accumulated depreciation	[1]	407	368
Construction work in progress		$ 16	18
Exelon Generation Co L L C [Member] | Nuclear Plant [Member] | Salem [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest	[5]	42.59%
Plant	[1],[5]	$ 596	566
Accumulated depreciation	[1],[5]	186	167
Construction work in progress	[5]	$ 41	40
Exelon Generation Co L L C [Member] | Nuclear Plant [Member] | Nine Mile Point [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		82.00%
Plant	[1]	$ 830	756
Accumulated depreciation	[1]	68	42
Construction work in progress		37	56
Exelon Generation Co L L C [Member] | Fossil Fuel Generation [Member] | Salem [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Plant		$ 3
Exelon Generation Co L L C [Member] | Fossil Fuel Generation [Member] | Wyman [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		5.89%
Plant	[1]	$ 3	3
Accumulated depreciation	[1]	3	3
Construction work in progress		$ 0	$ 0
PECO Energy Co [Member] | Conemaugh [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		20.70%
PECO Energy Co [Member] | Pennsylvania [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		22.00%
PECO Energy Co [Member] | Delaware And New Jersey [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		42.55%
PECO Energy Co [Member] | Delaware River Crossing [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		42.55%
Baltimore Gas and Electric Company [Member] | Conemaugh [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		10.56%
Baltimore Gas and Electric Company [Member] | Pennsylvania [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		7.00%
Potomac Electric Power Company [Member] | Conemaugh [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		9.72%
Potomac Electric Power Company [Member] | Pennsylvania [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		27.00%
Potomac Electric Power Company [Member] | Valley Forge [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		11.90%
Delmarva Power and Light Company [Member] | Conemaugh [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		3.72%
Delmarva Power and Light Company [Member] | Pennsylvania [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		9.00%
Delmarva Power and Light Company [Member] | Delaware And New Jersey [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		1.00%
Delmarva Power and Light Company [Member] | Delaware River Crossing [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		7.45%
Delmarva Power and Light Company [Member] | Merrill Creek [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		4.83%
Delmarva Power and Light Company [Member] | Valley Forge [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		7.40%
Atlantic City Electric Company [Member] | Conemaugh [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		3.83%
Atlantic City Electric Company [Member] | Pennsylvania [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		8.00%
Atlantic City Electric Company [Member] | Delaware And New Jersey [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		13.90%
Atlantic City Electric Company [Member] | Delaware River Crossing [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		7.45%
Atlantic City Electric Company [Member] | Merrill Creek [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		11.91%
Atlantic City Electric Company [Member] | Valley Forge [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		6.60%
Atlantic City Electric Company [Member] | New Freedom Switching [Member]
Schedule Of Jointly Owned Utility Plant Net Ownership [Abstract]
Ownership interest		21.78%
[1]	Excludes asset retirement costs.
[2]	PECO, BGE, Pepco, DPL and ACE own a 22%, 7%, 27%, 9% and 8% share, respectively, in 127 miles of 500kV lines located in Pennsylvania as well as a 20.72%, 10.56%, 9.72%, 3.72% and 3.83% share, respectively, of a 500kV substation immediately outside of the Conemaugh fossil generating station which supplies power to the 500kV lines including, but not limited to, the lines noted above.
[3]	PECO, DPL and ACE own a 42.55%, 1% and 13.9% share, respectively in 151.3 miles of 500kV lines located in New Jersey and Delaware Station. PECO, DPL and ACE also own a 42.55%, 7.45% and 7.45% share, respectively, in 2.5 miles of 500kV line located over the Delaware River. ACE also has a 21.78% share in a 500kV New Freedom Switching
[4]	Generation, DPL and ACE own a 44.24%, 4.83% and 11.91% share, respectively in assets located at Merrill Creek Reservoir located in New Jersey. Pepco, DPL and ACE own a 11.9%, 7.4% and 6.6% share, respectively, in Valley Forge Corporate Center.
[5]	Generation also owns a proportionate share in the fossil fuel combustion turbine at Salem, which is fully depreciated. The gross book value was $3 million at December 31, 2016 and 2015.

Intangible Assets - Schedule of

Intangible Assets - Schedule of Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Mar. 24, 2016	Dec. 31, 2014
Goodwill [Roll Forward]
Goodwill, Gross		$ 8,660	$ 8,660	$ 4,655		$ 4,655
Accumulated impairment loss		1,983	1,983	1,983		1,983
Goodwill, beginning balance	$ 2,672		2,672	2,672
Goodwill from business combination			4,016
Impairment losses			0	0
Goodwill, Purchase Accounting Adjustments			(11)
Goodwill, ending balance		6,677	6,677	2,672
Exelon Generation Co L L C [Member]
Goodwill [Roll Forward]
Goodwill, Gross		47	47	47		47
Goodwill, beginning balance	47		47	47
Goodwill from business combination			0
Impairment losses			0	0
Goodwill, ending balance		47	47	47
Commonwealth Edison Co [Member]
Goodwill [Roll Forward]
Goodwill, Gross		4,608	4,608	4,608		4,608
Accumulated impairment loss		1,983	1,983	1,983		1,983
Goodwill, beginning balance	2,625		2,625	2,625
Goodwill from business combination			0
Impairment losses			0	0
Goodwill, ending balance		2,625	2,625	2,625
Delmarva Power and Light Company [Member]
Goodwill [Roll Forward]
Goodwill, Gross		8	8	8		8
Goodwill, beginning balance	8		8	8
Goodwill from business combination			0
Impairment losses			0	0
Goodwill, ending balance		8	8	8
Pepco Holdings LLC [Member] | Predecessor [Member]
Goodwill [Roll Forward]
Goodwill, Gross	1,418			1,418		1,425
Accumulated impairment loss	12			12		$ 18
Goodwill, beginning balance	1,406	1,406	1,406	1,407
Goodwill from business combination	0		0
Impairment losses	0			(7)
Goodwill, Impairment Loss, Net of Tax				(1)
Goodwill, Other Increase (Decrease)				(6)
Goodwill, ending balance	1,406			$ 1,406
Pepco Holdings LLC [Member] | Successor [Member]
Goodwill [Roll Forward]
Goodwill, Gross	0	4,005	4,005
Accumulated impairment loss		0	0		$ 0
Goodwill, beginning balance		0
Goodwill from business combination		4,016
Impairment losses		0
Goodwill, Purchase Accounting Adjustments		(11)
Goodwill, ending balance	$ 0	$ 4,005	$ 4,005

Intangible Assets - Narrative (

Intangible Assets - Narrative (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 30, 2016	Mar. 24, 2016	Dec. 31, 2008
Goodwill [Line Items]
Goodwill			$ 6,677	$ 6,677	$ 2,672	$ 2,672
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets								$ 4,005
Goodwill, Purchase Accounting Adjustments				(11)
Amortization of Intangible Assets				87	76	179
Finite lived intangible assets gross			1,225	1,225
Commonwealth Edison Co [Member]
Goodwill [Line Items]
Goodwill			2,625	2,625	2,625	2,625
Amortization of Intangible Assets				7	7	7
Current alternative or renewable energy credits			0	0	5
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount							30.00%
Exelon Generation Co L L C [Member]
Goodwill [Line Items]
Goodwill			47	47	47	47
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets						50
Amortization of Intangible Assets				79	69	179
Current alternative or renewable energy credits			317	317	251
Alternative Or Renewable Energy Credits Noncurrent			29	29	56
PECO Energy Co [Member]
Goodwill [Line Items]
Current alternative or renewable energy credits			1	1	2
Pepco Holdings LLC [Member] | Predecessor [Member]
Goodwill [Line Items]
Goodwill		$ 1,406			1,406	1,407
Pepco Holdings LLC [Member] | Successor [Member]
Goodwill [Line Items]
Goodwill		0	4,005	4,005
Goodwill, Purchase Accounting Adjustments			(11)
Potomac Electric Power Company [Member]
Goodwill [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets								1,700
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount							10.00%
Delmarva Power and Light Company [Member]
Goodwill [Line Items]
Goodwill			8	8	8	8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets								1,100
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount							10.00%		50.00%
Atlantic City Electric Company [Member]
Goodwill [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets								$ 1,200
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount							10.00%
Unamortized Energy Contracts [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]			35	22	135
Unamortized Energy Contracts [Member] | Commonwealth Edison Co [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]			0	0	0
Unamortized Energy Contracts [Member] | Exelon Generation Co L L C [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]			35	22	135
Unamortized Energy Contracts [Member] | PECO Energy Co [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]			0	0	0
Unamortized Energy Contracts [Member] | Pepco Holdings LLC [Member]
Goodwill [Line Items]
Finite lived intangible assets gross			(1,515)	(1,515)
Unamortized Energy Contracts [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]	$ 0
Unamortized Energy Contracts [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]		0
Unamortized Energy Contracts [Member] | Potomac Electric Power Company [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]			0	0	0
Unamortized Energy Contracts [Member] | Potomac Electric Power Company [Member] | Predecessor [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]				0	0
Unamortized Energy Contracts [Member] | Delmarva Power and Light Company [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]			0	0	0
Unamortized Energy Contracts [Member] | Atlantic City Electric Company [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]			0
Unamortized Energy Contracts [Member] | Atlantic City Electric Company [Member] | Predecessor [Member]
Goodwill [Line Items]
Amortization of Intangible Assets	[1]				$ 0	$ 0
Constellation Energy Group LLC [Member] | Unamortized Energy Contracts [Member] | Exelon Generation Co L L C [Member]
Goodwill [Line Items]
Finite lived intangible assets gross	[2],[3]		1,499	$ 1,499
Constellation Energy Group LLC [Member] | Trade Names [Member]
Goodwill [Line Items]
Useful life				10 years
Constellation Energy Group LLC [Member] | Trade Names [Member] | Exelon Generation Co L L C [Member]
Goodwill [Line Items]
Finite lived intangible assets gross	[3]		$ 243	$ 243
[1]	Included in Operating revenues or Purchased power and fuel on the Registrants’ Consolidated Statements of Operations and Comprehensive Income
[2]	Includes unamortized energy contract assets and liabilities on Exelon's and Generation's Consolidated Balance Sheets. Excludes $10 million of other miscellaneous unamortized energy contracts that have been acquired at various points in time. The estimated amortization for these miscellaneous unamortized energy contracts is $(9) million, $(7) million, $(6) million, $(2) million and $4 million for 2017, 2018, 2019, 2020 and 2021, respectively.
[3]	On March 12, 2012, Constellation merged into Exelon with Exelon continuing as the surviving corporation pursuant to the transactions contemplated by the Agreement and Plan of Merger. Since the merger transaction, Generation includes the former Constellation generation and customer supply operations.

Intangible Assets - Schedule102

Intangible Assets - Schedule of Other Intangible Assets (Details) $ in Millions		1 Months Ended			12 Months Ended
		Sep. 30, 2011MW	Dec. 31, 2010MW	Feb. 28, 2003USD ($)	Dec. 31, 2016USD ($)
Finite-Lived Intangible Assets [Line Items]
Gross					$ 1,225
Accumulated Amortization					(1,504)
Net					(279)
2,017					244
2,018					(101)
2,019					38
2,020					30
2,021					$ (11)
Licensing Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[1],[2]				10 years
Gross	[1]				$ 95
Accumulated Amortization	[1]				(15)
Net	[1]				80
2,017	[1]				(10)
2,018	[1]				10
2,019	[1]				(10)
2,020	[1]				(10)
2,021	[1]				10
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Net	[3],[4]				11
2,017					$ (1)
Commonwealth Edison Co [Member]
Finite-Lived Intangible Assets [Line Items]
Chicago payment made to city				$ 60
Period for payment				10 years
City of Chicago payment made to 3rd party				$ (2)
City of Chicago payment received				32
Reduction of amortization expense				$ (2)
Commonwealth Edison Co [Member] | Intangible Asset Nineteen Ninety Nine Chicago Settlement Agreement [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[5]				21 years 9 months 18 days
Gross	[5]				$ 100
Accumulated Amortization	[5]				(86)
Net	[5]				14
2,017	[5]				(3)
2,018	[5]				3
2,019	[5]				(3)
2,020	[5]				(3)
2,021	[5]				$ 0
Commonwealth Edison Co [Member] | Intangible Asset Two Thousand Three Chicago Settlement Agreement [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[6]				17 years 10 months 24 days
Gross	[6]				$ 62
Accumulated Amortization	[6]				(47)
Net	[6]				15
2,017	[6]				(4)
2,018	[6]				4
2,019	[6]				(4)
2,020	[6]				(4)
2,021	[6]				$ 0
Pepco Holdings LLC [Member] | Unamortized Energy Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period					6 years 9 months 18 days
Gross					$ (1,515)
Accumulated Amortization					430
Net					(1,085)
2,017					(335)
2,018					(189)
2,019					119
2,020					(115)
2,021					(92)
Pepco Holdings LLC [Member] | Utility Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Gross					25
Accumulated Amortization					0
Net					25
2,017					0
2,018					0
2,019					0
2,020					0
2,021					0
Exelon Generation Co L L C [Member]
Finite-Lived Intangible Assets [Line Items]
2,017					(9)
2,018					(7)
2,019					(6)
2,020					2
2,021					$ 4
Exelon Wind Acquisition [Member] | Exelon Generation Co L L C [Member]
Finite-Lived Intangible Assets [Line Items]
Wind turbine supply megawatt | MW			735
Exelon Wind Acquisition [Member] | Exelon Generation Co L L C [Member] | Unamortized Energy Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[7],[8]				18 years
Gross	[7],[8]				$ 224
Accumulated Amortization	[7],[8]				(83)
Net	[7],[8]				141
2,017	[7],[8]				(14)
2,018	[7],[8]				14
2,019	[7],[8]				(14)
2,020	[7],[8]				(10)
2,021	[7],[8]				$ 10
Antelope Valley Acquisition [Member] | Exelon Generation Co L L C [Member]
Finite-Lived Intangible Assets [Line Items]
Wind turbine supply megawatt | MW		242
Antelope Valley Acquisition [Member] | Exelon Generation Co L L C [Member] | Unamortized Energy Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[8],[9]				25 years
Gross	[8],[9]				$ 190
Accumulated Amortization	[8],[9]				(28)
Net	[8],[9]				162
2,017	[8],[9]				(8)
2,018	[8],[9]				8
2,019	[8],[9]				(8)
2,020	[8],[9]				(8)
2,021	[8],[9]				$ 8
Constellation Energy Group LLC [Member] | Exelon Generation Co L L C [Member] | Unamortized Energy Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[4],[8]				1 year 6 months
Gross	[4],[8]				$ 1,499
Accumulated Amortization	[4],[8]				(1,440)
Net	[4],[8]				59
2,017	[4],[8]				(21)
2,018	[4],[8]				(11)
2,019	[4],[8]				(8)
2,020	[4],[8]				(10)
2,021	[4],[8]				$ 10
Constellation Energy Group LLC [Member] | Exelon Generation Co L L C [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[3],[4]				12 years 4 months 24 days
Gross	[3],[4]				$ 214
Accumulated Amortization	[3],[4]				(94)
Net	[3],[4]				120
2,017	[3],[4]				(18)
2,018	[3],[4]				18
2,019	[3],[4]				(17)
2,020	[3],[4]				(17)
2,021	[3],[4]				$ 17
Constellation Energy Group LLC [Member] | Exelon Generation Co L L C [Member] | Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[4]				10 years
Gross	[4]				$ 243
Accumulated Amortization	[4]				(125)
Net	[4]				118
2,017	[4]				(23)
2,018	[4]				23
2,019	[4]				(23)
2,020	[4]				(23)
2,021	[4]				$ 23
CENG [Member] | Exelon Generation Co L L C [Member] | Unamortized Energy Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[8],[10]				1 year 8 months 12 days
Gross	[8],[10]				$ (97)
Accumulated Amortization	[8],[10]				59
Net	[8],[10]				(38)
2,017	[8],[10]				(15)
2,018	[8],[10]				18
2,019	[8],[10]				(15)
2,020	[8],[10]				(8)
2,021	[8],[10]				$ 4
Integrys [Member] | Exelon Generation Co L L C [Member] | Unamortized Energy Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[8],[10]				2 years 4 months 24 days
Gross	[8],[11]				$ 5
Accumulated Amortization	[8],[11]				(3)
Net	[8],[11]				2
2,017	[8],[11]				(1)
2,018	[8],[11]				1
2,019	[8],[11]				0
2,020	[8],[11]				0
2,021	[8],[11]				$ 0
Integrys [Member] | Exelon Generation Co L L C [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[3],[11]				10 years
Gross	[3],[11]				$ 50
Accumulated Amortization	[3],[11]				(11)
Net	[3],[11]				39
2,017	[3],[11]				(5)
2,018	[3],[11]				5
2,019	[3],[11]				(5)
2,020	[3],[11]				(5)
2,021	[3],[11]				$ 5
PES [Member] | Exelon Generation Co L L C [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period					15 years
Gross					$ 12
Accumulated Amortization					(1)
Net	[3],[11]				11
2,017					(1)
2,018					1
2,019					(1)
2,020					(1)
2,021					$ 1
PES [Member] | Exelon Generation Co L L C [Member] | Customer Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[4]				1 year
Gross	[4]				$ 9
Accumulated Amortization	[4]				(7)
Net	[4]				2
2,017	[4]				(2)
2,018	[4]				0
2,019	[4]				0
2,020	[4]				0
2,021	[4]				$ 0
ConEdison Solutions [Member] | Exelon Generation Co L L C [Member] | Unamortized Energy Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period					1 year 6 months
Gross	[8],[11]				$ 100
Accumulated Amortization					(53)
Net	[8],[11]				47
2,017					(37)
2,018					7
2,019					(2)
2,020					$ (1)
ConEdison Solutions [Member] | Exelon Generation Co L L C [Member] | Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average amortization period	[2],[3],[11]				10 years
Gross	[3],[11]				$ 9
Accumulated Amortization	[3],[11]				0
Net	[3],[11]				9
2,017	[3],[11]				(1)
2,018	[3],[11]				1
2,019	[3],[11]				(1)
2,020	[3],[11]				(1)
2,021	[3],[11]				$ 1
[1]	(a)On May 31, 2015, Exelon entered into a long-term software license agreement. Exelon is required to make payments starting August 2015 through May 2024. The intangible asset recognized as a result of these payments is being amortized on a straight-line basis over the contract term.
[2]	Weighted-average amortization period was calculated at the date of a) acquisition for acquired assets or b) settlement agreement.
[3]	Excludes $11 million of other miscellaneous customer relationships that have been acquired. The estimated amortization for these miscellaneous customer relationships is $1 million in each of the years from 2017 to 2021.
[4]	On March 12, 2012, Constellation merged into Exelon with Exelon continuing as the surviving corporation pursuant to the transactions contemplated by the Agreement and Plan of Merger. Since the merger transaction, Generation includes the former Constellation generation and customer supply operations.
[5]	In March 1999, ComEd entered into a settlement agreement with the City of Chicago associated with ComEd’s franchise agreement. Under the terms of the settlement, ComEd agreed to make payments to the City of Chicago each year from 1999 to 2002. The intangible asset recognized as a result of these payments is being amortized ratably over the remaining term of the franchise agreement, which ends in 2020.
[6]	In February 2003, ComEd entered into separate agreements with the City of Chicago and with Midwest Generation, LLC (Midwest Generation). Under the terms of the settlement agreement with the City of Chicago, ComEd agreed to pay the City of Chicago a total of $60 million over a ten-year period, beginning in 2003. The intangible asset recognized as a result of the settlement agreement is being amortized ratably over the remaining term of the City of Chicago franchise agreement, which ends in 2020. As required by the settlement, ComEd also made a payment of $2 million to a third-party on the City of Chicago’s behalf. Under the terms of the agreement with Midwest Generation, ComEd received payments of $32 million from Midwest Generation to relieve Midwest Generation’s obligation under the 1999 fossil sale agreement with ComEd to build the generation facility in the City of Chicago. The payments received by ComEd, which have been recorded in Other deferred credits and other liabilities, and other long-term liabilities on Exelon's and ComEd's Consolidated Balance Sheets are being recognized ratably (approximately $2 million annually) as an offset to amortization expense over the remaining term of the franchise agreement.
[7]	In December 2010, Generation acquired all of the equity interests of John Deere Renewables, LLC (later named Exelon Wind), adding 735 MWs of installed, operating wind capacity located in eight states.
[8]	Includes unamortized energy contract assets and liabilities on Exelon's and Generation's Consolidated Balance Sheets. Excludes $10 million of other miscellaneous unamortized energy contracts that have been acquired at various points in time. The estimated amortization for these miscellaneous unamortized energy contracts is $(9) million, $(7) million, $(6) million, $(2) million and $4 million for 2017, 2018, 2019, 2020 and 2021, respectively.
[9]	In September 2011, Generation acquired all of the interest in Antelope Valley Solar Ranch One, a 242 MW solar project in northern Los Angeles County, CA from First Solar, Inc.
[10]	See Note 5—Investment in Constellation Energy Nuclear Group, LLC for additional information.
[11]	See Note 4—Mergers, Acquisitions, and Dispositions for additional information.

Intangible Assets - Summary of

Intangible Assets - Summary of Amortization Expense (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Intangible asset amortization expense			$ 87	$ 76	$ 179
Exelon Generation Co L L C [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset amortization expense			79	69	179
Commonwealth Edison Co [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset amortization expense			7	7	7
Unamortized Energy Contracts [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset amortization expense	[1]		35	22	135
Unamortized Energy Contracts [Member] | Exelon Generation Co L L C [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset amortization expense	[1]		35	22	135
Unamortized Energy Contracts [Member] | Commonwealth Edison Co [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset amortization expense	[1]		$ 0	$ 0	$ 0
Unamortized Energy Contracts [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset amortization expense	[1]	$ 0
[1]	Included in Operating revenues or Purchased power and fuel on the Registrants’ Consolidated Statements of Operations and Comprehensive Income

Fair Value of Financial Asse104

Fair Value of Financial Assets and Liabilities - Fair Value of Financial Liabilities Recorded at the Carrying Amount (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt (including amounts due within one year) (a)		$ 962	$ 275
Due to Related Parties, Noncurrent		641	641
Spent Nuclear Fuel Obligation, Noncurrent		1,024	1,021
Debt Issuance Costs, Net		200	180
Preferred stock(b)		0	193
Financing Trust Member [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Issuance Costs, Net		7
Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		1,267	536
Long-term debt (including amounts due within one year) (a)	[1]	34,005	25,145
Due to Related Parties, Noncurrent	[2]	641	641
Spent Nuclear Fuel Obligation, Noncurrent		1,024	1,021
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		1,267	536
Long-term debt (including amounts due within one year) (a)	[1]	34,813	25,924
Due to Related Parties, Noncurrent	[2]	667	673
Spent Nuclear Fuel Obligation, Noncurrent		732	818
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		0	3
Long-term debt (including amounts due within one year) (a)	[1]	1,113	931
Due to Related Parties, Noncurrent	[2]	0	0
Spent Nuclear Fuel Obligation, Noncurrent		0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		1,267	533
Long-term debt (including amounts due within one year) (a)	[1]	31,741	23,644
Due to Related Parties, Noncurrent	[2]	0	0
Spent Nuclear Fuel Obligation, Noncurrent		732	818
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year) (a)	[1]	1,959	1,349
Due to Related Parties, Noncurrent	[2]	667	673
Spent Nuclear Fuel Obligation, Noncurrent		0	0
Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt (including amounts due within one year) (a)		115	127
Due to Related Parties, Noncurrent		922	933
Spent Nuclear Fuel Obligation, Noncurrent		1,024	1,021
Debt Issuance Costs, Net		64	70
Exelon Generation Co L L C [Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		699	29
Long-term debt (including amounts due within one year) (a)	[1]	9,241	8,959
Spent Nuclear Fuel Obligation, Noncurrent		1,024	1,021
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		699	29
Long-term debt (including amounts due within one year) (a)	[1]	9,152	9,116
Spent Nuclear Fuel Obligation, Noncurrent		732	818
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year) (a)	[1]	0	0
Spent Nuclear Fuel Obligation, Noncurrent		0	0
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		699	29
Long-term debt (including amounts due within one year) (a)	[1]	7,482	7,767
Spent Nuclear Fuel Obligation, Noncurrent		732	818
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year) (a)	[1]	1,670	1,349
Spent Nuclear Fuel Obligation, Noncurrent		0	0
Commonwealth Edison Co [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Due to Related Parties, Noncurrent		205	205
Debt Issuance Costs, Net		46	38
Commonwealth Edison Co [Member] | Financing Trust Member [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Issuance Costs, Net		1
Commonwealth Edison Co [Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			294
Long-term debt (including amounts due within one year) (a)	[1]	7,033	6,509
Due to Related Parties, Noncurrent	[2]	205	205
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			294
Long-term debt (including amounts due within one year) (a)	[1]	7,585	7,069
Due to Related Parties, Noncurrent	[2]	215	213
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			0
Long-term debt (including amounts due within one year) (a)	[1]	0	0
Due to Related Parties, Noncurrent	[2]	0	0
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			294
Long-term debt (including amounts due within one year) (a)	[1]	7,585	7,069
Due to Related Parties, Noncurrent	[2]	0	0
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			0
Long-term debt (including amounts due within one year) (a)	[1]	0	0
Due to Related Parties, Noncurrent	[2]	215	213
PECO Energy Co [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Due to Related Parties, Noncurrent		184	184
Debt Issuance Costs, Net		15	15
PECO Energy Co [Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt (including amounts due within one year) (a)	[1]	2,580	2,580
Due to Related Parties, Noncurrent		184	184
PECO Energy Co [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt (including amounts due within one year) (a)	[1]	2,794	2,786
Due to Related Parties, Noncurrent		192	195
PECO Energy Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt (including amounts due within one year) (a)	[1]	0	0
Due to Related Parties, Noncurrent		0	0
PECO Energy Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt (including amounts due within one year) (a)	[1]	2,794	2,786
Due to Related Parties, Noncurrent		0	0
PECO Energy Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt (including amounts due within one year) (a)	[1]	0	0
Due to Related Parties, Noncurrent		192	195
Baltimore Gas and Electric Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Due to Related Parties, Noncurrent		252	252
Debt Issuance Costs, Net		15	9
Preferred stock(b)		0	190
Baltimore Gas and Electric Company [Member] | Financing Trust Member [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Issuance Costs, Net		6
Baltimore Gas and Electric Company [Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		45	213
Long-term debt (including amounts due within one year) (a)	[1]	2,322	1,858
Due to Related Parties, Noncurrent	[2]	252	252
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		45	213
Long-term debt (including amounts due within one year) (a)	[1]	2,467	2,044
Due to Related Parties, Noncurrent	[2]	260	264
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		0	3
Long-term debt (including amounts due within one year) (a)	[1]	0	0
Due to Related Parties, Noncurrent	[2]	0	0
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		45	210
Long-term debt (including amounts due within one year) (a)	[1]	2,467	2,044
Due to Related Parties, Noncurrent	[2]	0	0
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year) (a)	[1]	0	0
Due to Related Parties, Noncurrent	[2]	260	264
Pepco Holdings LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt (including amounts due within one year) (a)		742	0
Debt Issuance Costs, Net			49
Pepco Holdings LLC [Member] | Successor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock(b)		0
Pepco Holdings LLC [Member] | Predecessor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Preferred stock(b)	[3]		183
Pepco Holdings LLC [Member] | Reported Value Measurement [Member] | Successor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		522
Long-term debt (including amounts due within one year) (a)	[1]	5,898
Spent Nuclear Fuel Obligation, Noncurrent			183
Pepco Holdings LLC [Member] | Reported Value Measurement [Member] | Predecessor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			958
Long-term debt (including amounts due within one year) (a)	[1]		5,279
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Successor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		522
Long-term debt (including amounts due within one year) (a)	[1]	5,809
Spent Nuclear Fuel Obligation, Noncurrent			183
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Predecessor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			958
Long-term debt (including amounts due within one year) (a)	[1]		5,817
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Successor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		0
Long-term debt (including amounts due within one year) (a)	[1]	0
Spent Nuclear Fuel Obligation, Noncurrent			0
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Predecessor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			0
Long-term debt (including amounts due within one year) (a)	[1]		0
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Successor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		522
Long-term debt (including amounts due within one year) (a)	[1]	5,520
Spent Nuclear Fuel Obligation, Noncurrent			0
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Predecessor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			958
Long-term debt (including amounts due within one year) (a)	[1]		5,231
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Successor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		0
Long-term debt (including amounts due within one year) (a)	[1]	289
Spent Nuclear Fuel Obligation, Noncurrent			183
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Predecessor [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			0
Long-term debt (including amounts due within one year) (a)	[1]		586
Potomac Electric Power Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Issuance Costs, Net		30	31
Potomac Electric Power Company [Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		23	64
Long-term debt (including amounts due within one year) (a)	[1]	2,349	2,351
Potomac Electric Power Company [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		23	64
Long-term debt (including amounts due within one year) (a)	[1]	2,796	2,673
Potomac Electric Power Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year) (a)	[1]	0	0
Potomac Electric Power Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		23	64
Long-term debt (including amounts due within one year) (a)	[1]	2,788	2,673
Potomac Electric Power Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year) (a)	[1]	8	0
Delmarva Power and Light Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Issuance Costs, Net		11	10
Delmarva Power and Light Company [Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			105
Long-term debt (including amounts due within one year) (a)	[1]	1,340	1,265
Delmarva Power and Light Company [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			105
Long-term debt (including amounts due within one year) (a)	[1]	1,383	1,288
Delmarva Power and Light Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			0
Long-term debt (including amounts due within one year) (a)	[1]	0	0
Delmarva Power and Light Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			105
Long-term debt (including amounts due within one year) (a)	[1]	1,383	1,185
Delmarva Power and Light Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			0
Long-term debt (including amounts due within one year) (a)	[1]	0	103
Atlantic City Electric Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Issuance Costs, Net		6	6
Atlantic City Electric Company [Member] | Reported Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			5
Long-term debt (including amounts due within one year) (a)	[1]	1,155	1,201
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			5
Long-term debt (including amounts due within one year) (a)	[1]	1,287	1,324
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			0
Long-term debt (including amounts due within one year) (a)	[1]	0	0
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			5
Long-term debt (including amounts due within one year) (a)	[1]	1,007	1,044
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term Debt, Fair Value			0
Long-term debt (including amounts due within one year) (a)	[1]	$ 280	$ 280
[1]	Includes unamortized debt issuance costs, which are not fair valued, of $200 million, $64 million, $46 million, $15 million, $15 million, $2 million, $30 million, $11 million, and $6 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE respectively, as of December 31, 2016. Includes unamortized debt issuance costs, which are not fair valued, of $180 million, $70 million, $38 million, $15 million, $9 million, $49 million, $31 million, $10 million, and $6 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE respectively, as of December 31, 2015.
[2]	Includes unamortized debt issuance costs which are not fair valued of $7 million, $1 million and $6 million for Exelon, ComEd and BGE, respectively, as of December 31, 2016 and December 31, 2015.
[3]	At December 31, 2015, PHI had 18,000 shares of Series A preferred stock authorized and outstanding, par value $0.01 per share.

Fair Value of Financial Asse105

Fair Value of Financial Assets and Liabilities - Fair Value Measurement of Assets and Liabilities, Recurring and Nonrecurring (Details) - USD ($)		Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		$ (392,000,000)	$ (374,000,000)
Derivative Liability, Current		282,000,000	205,000,000
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		(2,000,000)	(8,000,000)
Derivative Asset, Notional Amount		933,000,000	1,236,000,000
Derivative, collateral, right to reclaim cash		29,000,000	52,000,000
Nuclear Decommissioning Trust Fund Investments [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Fair Value Net Assets Liabilities Excluded From Nuclear Decommissioning Trust Fund Investments		(31,000,000)	(3,000,000)
Pledged Assets For Zion Station Decommissioning [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Fair Value Net Assets Liabilities Excluded From Nuclear Decommissioning Trust Fund Investments			1,000,000
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		12,443,000,000	17,878,000,000
FinancialAssetsFairValueDisclosure1		13,253,000,000	18,556,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[1]	373,000,000
Alternative Investments, Fair Value Disclosure		3,113,000,000	2,765,000,000
Deferred Compensation Liability, Current and Noncurrent		(136,000,000)	(99,000,000)
Financial Liabilities Fair Value Disclosure		(810,000,000)	(678,000,000)
Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(662,000,000)	(563,000,000)
Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(79,000,000)	(127,000,000)
Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[2]	4,114,000,000	6,391,000,000
Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(12,000,000)	(16,000,000)
Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(4,697,000,000)	(6,827,000,000)
Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(4,000,000)	(12,000,000)
Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		23,000,000	15,000,000
Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(10,000,000)	(16,000,000)
Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(21,000,000)	(3,000,000)
Fair Value, Measurements, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	129,000,000	311,000,000
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		2,011,000,000	1,894,000,000
Investments, Fair Value Disclosure		6,014,000,000	4,902,000,000
Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		28,000,000	20,000,000
Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		264,000,000	326,000,000
Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[4]	3,049,000,000	2,660,000,000
Investments, Fair Value Disclosure	[4]	11,092,000,000	10,345,000,000
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,804,000,000	2,066,000,000
Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			46,000,000
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,320,000,000	1,338,000,000
Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		17,000,000	8,000,000
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		37,000,000	61,000,000
Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[5]	493,000,000	390,000,000
Investments, Fair Value Disclosure	[5]	552,000,000	537,000,000
Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			1,000,000
Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			55,000,000
Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		71,000,000	0
Investments, Fair Value Disclosure		498,000,000	428,000,000
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		326,000,000	35,000,000
Investments, Fair Value Disclosure		326,000,000	35,000,000
Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure			216,000,000
Investments, Fair Value Disclosure			216,000,000
Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[6]	64,000,000	105,000,000
Investments, Fair Value Disclosure	[6]	113,000,000	205,000,000
Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		11,000,000	17,000,000
Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		2,000,000	6,000,000
Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		493,000,000	390,000,000
Investments, Fair Value Disclosure		3,977,000,000	4,328,000,000
Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		64,000,000	105,000,000
Investments, Fair Value Disclosure		83,000,000	127,000,000
Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		50,000,000	48,000,000
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		148,000,000	125,000,000
Investments, Fair Value Disclosure		148,000,000	125,000,000
Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,381,000,000	2,069,000,000
Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		5,092,000,000	7,096,000,000
Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		76,000,000	130,000,000
Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	[2]	(3,787,000,000)	(5,157,000,000)
Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		5,000,000	15,000,000
Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		(21,000,000)	(6,000,000)
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		16,000,000	25,000,000
Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		28,000,000	54,000,000
Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		42,000,000	33,000,000
Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		224,000,000	84,000,000
Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		74,000,000
Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16,000,000
Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		84,000,000	36,000,000
Fair Value, Inputs, Level 1 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative, Fair Value, Amount Offset Against Collateral, Net		71,000,000	476,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		5,637,000,000	10,397,000,000
FinancialAssetsFairValueDisclosure1		5,674,000,000	10,372,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[1]	373,000,000	5,766,000,000
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(37,000,000)	25,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(37,000,000)	25,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(3,000,000)	(33,000,000)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[2]	1,233,000,000	2,440,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(1,267,000,000)	(2,382,000,000)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(4,000,000)	(12,000,000)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		4,000,000	12,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	110,000,000	219,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		3,551,000,000	3,008,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	4,952,000,000	4,550,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,291,000,000	1,323,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16,000,000	6,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[5]	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			6,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	27,000,000	7,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		11,000,000	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	1,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,291,000,000	1,323,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		50,000,000	48,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		197,000,000	(6,000,000)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,358,000,000	1,922,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		3,000,000	36,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	[2]	(1,164,000,000)	(1,964,000,000)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		3,000,000	10,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		(2,000,000)	(3,000,000)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,000,000	7,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		124,000,000	48,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		74,000,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative, Fair Value, Amount Offset Against Collateral, Net		197,000,000	557,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		2,700,000,000	3,187,000,000
FinancialAssetsFairValueDisclosure1		2,937,000,000	3,521,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[1]	0	0
Investments, Fair Value Disclosure
Deferred Compensation Liability, Current and Noncurrent		(136,000,000)	(99,000,000)
Financial Liabilities Fair Value Disclosure		(237,000,000)	(334,000,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(89,000,000)	(219,000,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(50,000,000)	(57,000,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[2]	2,339,000,000	3,186,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(12,000,000)	(16,000,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(2,378,000,000)	(3,348,000,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		19,000,000	3,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(10,000,000)	(16,000,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(21,000,000)	(3,000,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	19,000,000	92,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		452,000,000	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		28,000,000	20,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		264,000,000	326,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	2,414,000,000	2,465,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,554,000,000	1,824,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			46,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		29,000,000	15,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,000,000	2,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		37,000,000	61,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[5]	59,000,000	147,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			1,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			49,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	3,000,000	71,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0	17,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		2,000,000	5,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,943,000,000	2,373,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		413,000,000	902,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		2,505,000,000	3,467,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		50,000,000	64,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	[2]	(2,142,000,000)	(2,629,000,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		2,000,000	5,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		(19,000,000)	(3,000,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		16,000,000	25,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		27,000,000	47,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		80,000,000	36,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16,000,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		64,000,000	36,000,000
Fair Value, Inputs, Level 3 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative, Fair Value, Amount Offset Against Collateral, Net		61,000,000	201,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		993,000,000	1,529,000,000
FinancialAssetsFairValueDisclosure1		1,529,000,000	1,898,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[1]	0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(536,000,000)	(369,000,000)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(536,000,000)	(369,000,000)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(26,000,000)	(37,000,000)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[2]	542,000,000	765,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(1,052,000,000)	(1,097,000,000)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	677,000,000	670,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		250,000,000	242,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[5]	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		427,000,000	428,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	19,000,000	22,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		250,000,000	242,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		19,000,000	22,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		771,000,000	1,173,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,229,000,000	1,707,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		23,000,000	30,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	[2]	(481,000,000)	(564,000,000)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		42,000,000	33,000,000
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20,000,000	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20,000,000	0
Exelon Generation Co L L C [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(153,000,000)	(150,000,000)
Derivative Liability, Current		263,000,000	182,000,000
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative, collateral, right to reclaim cash		8,000,000	3,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		12,268,000,000	12,453,000,000
FinancialAssetsFairValueDisclosure1		12,718,000,000	12,815,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[1]	39,000,000
Alternative Investments, Fair Value Disclosure		3,113,000,000	2,765,000,000
Deferred Compensation Liability, Current and Noncurrent		(34,000,000)	(30,000,000)
Financial Liabilities Fair Value Disclosure		(450,000,000)	(362,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(404,000,000)	(316,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(79,000,000)	(127,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[2]	4,114,000,000	6,391,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(12,000,000)	(16,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(4,439,000,000)	(6,580,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(4,000,000)	(12,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		23,000,000	15,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(10,000,000)	(16,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(21,000,000)	(3,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	129,000,000	311,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		2,011,000,000	1,894,000,000
Investments, Fair Value Disclosure		6,014,000,000	4,902,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		28,000,000	20,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		264,000,000	326,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[4]	3,049,000,000	2,660,000,000
Investments, Fair Value Disclosure	[4]	11,092,000,000	10,345,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,804,000,000	2,066,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			46,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,320,000,000	1,338,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		17,000,000	8,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		37,000,000	61,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[5]	493,000,000	390,000,000
Investments, Fair Value Disclosure	[5]	552,000,000	537,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			1,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			55,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		71,000,000	0
Investments, Fair Value Disclosure		498,000,000	428,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		326,000,000	35,000,000
Investments, Fair Value Disclosure		326,000,000	35,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure			216,000,000
Investments, Fair Value Disclosure			216,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[6]	64,000,000	105,000,000
Investments, Fair Value Disclosure	[6]	113,000,000	205,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		11,000,000	17,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		2,000,000	6,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		493,000,000	390,000,000
Investments, Fair Value Disclosure		3,977,000,000	4,328,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		64,000,000	105,000,000
Investments, Fair Value Disclosure		83,000,000	127,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		19,000,000	17,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		148,000,000	125,000,000
Investments, Fair Value Disclosure		148,000,000	125,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,381,000,000	2,069,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		5,090,000,000	7,096,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		76,000,000	130,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	[2]	(3,785,000,000)	(5,157,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		5,000,000	15,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		(21,000,000)	(6,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		12,000,000	29,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		42,000,000	33,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		39,000,000	30,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		2,000,000
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		18,000,000	13,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		5,200,000,000	4,704,000,000
FinancialAssetsFairValueDisclosure1		5,237,000,000	4,679,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[1]	39,000,000	104,000,000
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(37,000,000)	25,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(37,000,000)	25,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(3,000,000)	(33,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[2]	1,233,000,000	2,440,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(1,267,000,000)	(2,382,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(4,000,000)	(12,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		4,000,000	12,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	110,000,000	219,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		3,551,000,000	3,008,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	4,952,000,000	4,550,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,291,000,000	1,323,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16,000,000	6,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[5]	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			6,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	27,000,000	7,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		11,000,000	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	1,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,291,000,000	1,323,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		19,000,000	17,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		197,000,000	(6,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,356,000,000	1,922,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		3,000,000	36,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	[2]	(1,162,000,000)	(1,964,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		3,000,000	10,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		(2,000,000)	(3,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,000,000	7,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		21,000,000	17,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		2,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		2,724,000,000	3,208,000,000
FinancialAssetsFairValueDisclosure1		2,859,000,000	3,473,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[1]	0	0
Deferred Compensation Liability, Current and Noncurrent		(34,000,000)	(30,000,000)
Financial Liabilities Fair Value Disclosure		(135,000,000)	(265,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(89,000,000)	(219,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(50,000,000)	(57,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[2]	2,339,000,000	3,186,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(12,000,000)	(16,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(2,378,000,000)	(3,348,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		19,000,000	3,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(10,000,000)	(16,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(21,000,000)	(3,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	19,000,000	92,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		452,000,000	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		28,000,000	20,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		264,000,000	326,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	2,414,000,000	2,465,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,554,000,000	1,824,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			46,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		29,000,000	15,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,000,000	2,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		37,000,000	61,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[5]	59,000,000	147,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			1,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			49,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	3,000,000	71,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0	17,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		2,000,000	5,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,943,000,000	2,373,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		413,000,000	902,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		2,505,000,000	3,467,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		50,000,000	64,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	[2]	(2,142,000,000)	(2,629,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		2,000,000	5,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		(19,000,000)	(3,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		11,000,000	22,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		18,000,000	13,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		18,000,000	13,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		1,231,000,000	1,776,000,000
FinancialAssetsFairValueDisclosure1		1,509,000,000	1,898,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[1]	0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(278,000,000)	(122,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(278,000,000)	(122,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(26,000,000)	(37,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[2]	542,000,000	765,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(794,000,000)	(850,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	677,000,000	670,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		250,000,000	242,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[5]	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		427,000,000	428,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	19,000,000	22,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		250,000,000	242,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		19,000,000	22,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		771,000,000	1,173,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,229,000,000	1,707,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		23,000,000	30,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	[2]	(481,000,000)	(564,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		42,000,000	33,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		239,000,000	(224,000,000)
Derivative Liability, Current		19,000,000	23,000,000
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		(246,000,000)	(226,000,000)
FinancialAssetsFairValueDisclosure1		20,000,000	29,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	20,000,000	29,000,000
Derivative Liability, Noncurrent	[8]	(258,000,000)	(247,000,000)
Deferred Compensation Liability, Current and Noncurrent		(8,000,000)	(8,000,000)
Financial Liabilities Fair Value Disclosure		(266,000,000)	(255,000,000)
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		20,000,000	29,000,000
FinancialAssetsFairValueDisclosure1		20,000,000	29,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	20,000,000	29,000,000
Derivative Liability, Noncurrent	[8]	0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		(8,000,000)	(8,000,000)
FinancialAssetsFairValueDisclosure1		0	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
Derivative Liability, Noncurrent	[8]	0	0
Deferred Compensation Liability, Current and Noncurrent		(8,000,000)	(8,000,000)
Financial Liabilities Fair Value Disclosure		(8,000,000)	(8,000,000)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			224,000,000
Derivative Liability, Current			(23,000,000)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		(258,000,000)	(247,000,000)
FinancialAssetsFairValueDisclosure1		0	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
Derivative Liability, Noncurrent	[8]	(258,000,000)	(247,000,000)
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(258,000,000)	(247,000,000)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		51,000,000	279,000,000
FinancialAssetsFairValueDisclosure1		62,000,000	291,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	45,000,000	271,000,000
Derivative Liability, Noncurrent		0	0
Deferred Compensation Liability, Current and Noncurrent		(11,000,000)	(12,000,000)
Financial Liabilities Fair Value Disclosure		(11,000,000)	(12,000,000)
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7,000,000	8,000,000
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		17,000,000	20,000,000
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		10,000,000	12,000,000
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		52,000,000	279,000,000
FinancialAssetsFairValueDisclosure1		52,000,000	279,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	45,000,000	271,000,000
Derivative Liability, Noncurrent		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7,000,000	8,000,000
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7,000,000	8,000,000
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		(1,000,000)	0
FinancialAssetsFairValueDisclosure1		10,000,000	12,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
Derivative Liability, Noncurrent		0	0
Deferred Compensation Liability, Current and Noncurrent		(11,000,000)	(12,000,000)
Financial Liabilities Fair Value Disclosure		(11,000,000)	(12,000,000)
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		10,000,000	12,000,000
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		10,000,000	12,000,000
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	0
FinancialAssetsFairValueDisclosure1		0	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
Derivative Liability, Noncurrent		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		36,000,000	25,000,000
FinancialAssetsFairValueDisclosure1		40,000,000	29,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	36,000,000	25,000,000
Derivative Liability, Noncurrent		0	0
Deferred Compensation Liability, Current and Noncurrent		(4,000,000)	(4,000,000)
Financial Liabilities Fair Value Disclosure		(4,000,000)	(4,000,000)
Baltimore Gas and Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		4,000,000	4,000,000
Baltimore Gas and Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		4,000,000	4,000,000
Baltimore Gas and Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		40,000,000	29,000,000
FinancialAssetsFairValueDisclosure1		40,000,000	29,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	36,000,000	25,000,000
Derivative Liability, Noncurrent		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		4,000,000	4,000,000
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		4,000,000	4,000,000
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		(4,000,000)	(4,000,000)
FinancialAssetsFairValueDisclosure1		0	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
Derivative Liability, Noncurrent		0	0
Deferred Compensation Liability, Current and Noncurrent		(4,000,000)	(4,000,000)
Financial Liabilities Fair Value Disclosure		(4,000,000)	(4,000,000)
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	0
FinancialAssetsFairValueDisclosure1		0	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
Derivative Liability, Noncurrent		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Pepco Holdings LLC [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset			18,000,000
Derivative Liability, Noncurrent			0
Derivative Liability, Current			0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1			103,000,000
FinancialAssetsFairValueDisclosure1			133,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]		42,000,000
Alternative Investments, Fair Value Disclosure	[10],[11]		834,000,000
Derivative Asset	[12],[13]		18,000,000
Deferred Compensation Liability, Current and Noncurrent			(30,000,000)
Financial Liabilities Fair Value Disclosure			(30,000,000)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset			0
Derivative assets, fair value			18,000,000
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		320,000,000
FinancialAssetsFairValueDisclosure1		348,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	217,000,000
Derivative Asset	[12],[13]	2,000,000
Deferred Compensation Liability, Current and Noncurrent		(28,000,000)
Financial Liabilities Fair Value Disclosure		(28,000,000)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability		0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		(2,000,000)
Derivative assets, fair value		0
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			2,000,000
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]		(2,000,000)
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]	0
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			73,000,000
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		131,000,000
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			12,000,000
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		73,000,000
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			15,000,000
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16,000,000
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			46,000,000
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		42,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1			54,000,000
FinancialAssetsFairValueDisclosure1			54,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]		42,000,000
Derivative Asset	[12],[13]		0
Deferred Compensation Liability, Current and Noncurrent			0
Financial Liabilities Fair Value Disclosure			0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset			0
Derivative assets, fair value			0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		290,000,000
FinancialAssetsFairValueDisclosure1		290,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	217,000,000
Derivative Asset	[12],[13]	2,000,000
Deferred Compensation Liability, Current and Noncurrent		0
Financial Liabilities Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability		0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		(2,000,000)
Derivative assets, fair value		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			2,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]		(2,000,000)
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			12,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		73,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			12,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		73,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1			12,000,000
FinancialAssetsFairValueDisclosure1			42,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]		0
Derivative Asset	[12],[13]		0
Deferred Compensation Liability, Current and Noncurrent			(30,000,000)
Financial Liabilities Fair Value Disclosure			(30,000,000)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset			0
Derivative assets, fair value			0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		10,000,000
FinancialAssetsFairValueDisclosure1		38,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	0
Derivative Asset	[12],[13]	0
Deferred Compensation Liability, Current and Noncurrent		(28,000,000)
Financial Liabilities Fair Value Disclosure		(28,000,000)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability		0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			42,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		38,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			15,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			27,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		22,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1			37,000,000
FinancialAssetsFairValueDisclosure1			37,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]		0
Derivative Asset	[12],[13]		18,000,000
Deferred Compensation Liability, Current and Noncurrent			0
Financial Liabilities Fair Value Disclosure			0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset			0
Derivative assets, fair value			18,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		20,000,000
FinancialAssetsFairValueDisclosure1		20,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	0
Derivative Asset	[12],[13]	0
Deferred Compensation Liability, Current and Noncurrent		0
Financial Liabilities Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability		0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			19,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			19,000,000
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20,000,000
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		128,000,000	64,000,000
FinancialAssetsFairValueDisclosure1		133,000,000	70,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	33,000,000	2,000,000
Derivative Asset		0
Deferred Compensation Liability, Current and Noncurrent		(5,000,000)	(6,000,000)
Financial Liabilities Fair Value Disclosure		(5,000,000)	(6,000,000)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		100,000,000	68,000,000
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		43,000,000	11,000,000
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16,000,000	15,000,000
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		41,000,000	42,000,000
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		76,000,000	13,000,000
FinancialAssetsFairValueDisclosure1		76,000,000	13,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	33,000,000	2,000,000
Derivative Asset		0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		43,000,000	11,000,000
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		43,000,000	11,000,000
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		33,000,000	32,000,000
FinancialAssetsFairValueDisclosure1		38,000,000	38,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	0	0
Derivative Asset		0
Deferred Compensation Liability, Current and Noncurrent		(5,000,000)	(6,000,000)
Financial Liabilities Fair Value Disclosure		(5,000,000)	(6,000,000)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		38,000,000	38,000,000
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16,000,000	15,000,000
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		22,000,000	23,000,000
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		19,000,000	19,000,000
FinancialAssetsFairValueDisclosure1		19,000,000	19,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	0	0
Derivative Asset		0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		19,000,000	19,000,000
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		19,000,000	19,000,000
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		41,000,000	(1,000,000)
FinancialAssetsFairValueDisclosure1		42,000,000	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	42,000,000	0
Derivative Asset	[13]	2,000,000
Deferred Compensation Liability, Current and Noncurrent		(1,000,000)	(1,000,000)
Financial Liabilities Fair Value Disclosure		(1,000,000)	(1,000,000)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		(2,000,000)
Derivative assets, fair value		0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			2,000,000
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]		(2,000,000)
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		42,000,000	0
FinancialAssetsFairValueDisclosure1		42,000,000	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	42,000,000	0
Derivative Asset	[13]	2,000,000
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		(2,000,000)
Derivative assets, fair value		0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			2,000,000
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]		(2,000,000)
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		(1,000,000)	(1,000,000)
FinancialAssetsFairValueDisclosure1		0	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	0	0
Derivative Asset	[13]	0
Deferred Compensation Liability, Current and Noncurrent		(1,000,000)	(1,000,000)
Financial Liabilities Fair Value Disclosure		(1,000,000)	(1,000,000)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]		0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	0
FinancialAssetsFairValueDisclosure1		0	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	0	0
Derivative Asset	[13]	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[13]		0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		130,000,000	30,000,000
FinancialAssetsFairValueDisclosure1		130,000,000	30,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	130,000,000	30,000,000
Derivative Asset		0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		130,000,000	30,000,000
FinancialAssetsFairValueDisclosure1		130,000,000	30,000,000
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	130,000,000	30,000,000
Derivative Asset		0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	0
FinancialAssetsFairValueDisclosure1		0	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	0	0
Derivative Asset		0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	0
FinancialAssetsFairValueDisclosure1		0	0
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	[9]	0	0
Derivative Asset		0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability			0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0
Derivative assets, fair value		0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		360,000,000	763,000,000
Cash and Cash Equivalents [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		252,000,000	329,000,000
Cash and Cash Equivalents [Member] | Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		36,000,000	38,000,000
Cash and Cash Equivalents [Member] | PECO Energy Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		22,000,000	27,000,000
Cash and Cash Equivalents [Member] | Baltimore Gas and Electric Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		13,000,000	6,000,000
Cash and Cash Equivalents [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure			16,000,000
Cash and Cash Equivalents [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		19,000,000
Cash and Cash Equivalents [Member] | Potomac Electric Power Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		9,000,000	5,000,000
Cash and Cash Equivalents [Member] | Delmarva Power and Light Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		4,000,000	5,000,000
Cash and Cash Equivalents [Member] | Atlantic City Electric Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		3,000,000	3,000,000
Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		180,000,000	178,000,000
Restricted cash member [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		157,000,000	121,000,000
Restricted cash member [Member] | Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		2,000,000	2,000,000
Restricted cash member [Member] | Baltimore Gas and Electric Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure			2,000,000
Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		25,000,000
Other Assets [Member] | Baltimore Gas and Electric Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		2,000,000
Other Assets [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure			18,000,000
Other Assets [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		23,000,000
Other Assets [Member] | Atlantic City Electric Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		$ 23,000,000	$ 18,000,000
[1]	Generation excludes cash of $252 million and $329 million at December 31, 2016 and 2015 and restricted cash of $157 million and $121 million at December 31, 2016 and 2015. Exelon excludes cash of $360 million and $763 million at December 31, 2016 and 2015 and restricted cash of $180 million and $178 million at December 31, 2016 and 2015 and includes long term restricted cash of $25 million at December 31, 2016, which is reported in other deferred debits on the balance sheet.
[2]	Collateral posted to/(received from) counterparties totaled $71 million, $197 million and $61 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2016. Collateral posted to/(received from) counterparties totaled $476 million, $557 million and $201 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2015.
[3]	Includes $29 million and $52 million of cash received from outstanding repurchase agreements at December 31, 2016 and 2015, respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (d) below.
[4]	Excludes net liabilities of $(31) million and $(3) million at December 31, 2016 and 2015, respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, repurchase agreement obligations, and payables related to pending securities purchases.
[5]	Includes derivative instruments of $(2) million and $(8) million, which have a total notional amount of $933 million and $1,236 million at December 31, 2016 and 2015, respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the fiscal years ended and do not represent the amount of the company's exposure to credit or market loss.
[6]	Excludes net assets of less than $1 million and $1 million at December 31, 2016 and 2015, respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases
[7]	ComEd excludes cash of $36 million and $38 million at December 31, 2016 and 2015 and restricted cash of $2 million and $2 million at December 31, 2016 and 2015. PECO excludes cash of $22 million and $27 million at December 31, 2016 and 2015. BGE excludes cash of $13 million and $6 million at December 31, 2016 and 2015 and restricted cash of less than $1 million and $2 million at December 31, 2016 and 2015 and includes long term restricted cash of $2 million at December 31, 2016, which is reported in other deferred debits on the balance sheet.
[8]	The Level 3 balance consists of the current and noncurrent liability of $19 million and $239 million, respectively, at December 31, 2016, and $23 million and $224 million, respectively, at December 31, 2015, related to floating-to-fixed energy swap contracts with unaffiliated suppliers.
[9]	(a)PHI excludes cash of $19 million and $16 million at December 31, 2016 and 2015 and includes long term restricted cash of $23 million and $18 million at December 31, 2016 and 2015 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $9 million and $5 million at December 31, 2016 and 2015. DPL excludes cash of $4 million and $5 million at December 31, 2016 and 2015. ACE excludes cash of $3 million and $3 million at December 31, 2016 and 2015 and includes long term restricted cash of $23 million and $18 million at December 31, 2016 and 2015 which is reported in other deferred debits on the balance sheet.
[10]	___(a)See Note 12—Fair Value of Financial Assets and Liabilities for a description of levels within the fair value hi
[11]	ss.(c)Excludes net liabilities of $28 million and net assets of $27 million at December 31, 2016 and 2015, respectively, which are required to reconcile to the fair value of net plan assets. These items consist primarily of receivables related to pending securities sales, interest and dividends receivable, and payables related to pending securities pur
[12]	Prior to the PHI Merger, PHI recorded derivative assets for the embedded call and redemption features on the shares of Preferred Stock outstanding as of December 31, 2015. See Note 19 - Mezzanine Equity for additional information. As a result of the PHI Merger, the PHI preferred stock derivative was reduced to zero as of March 23, 2016.
[13]	Represents natural gas futures purchased by DPL as part of a natural gas hedging program approved by the DPSC.

Fair Value of Financial Asse106

Fair Value of Financial Assets and Liabilities - Fair Value Reconciliation of Level 3 Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended		12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016		Dec. 31, 2016		Dec. 31, 2015	Mar. 24, 2016	Dec. 31, 2014
Exelon Generation Co L L C [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings					$ 677		$ 834
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					18		(15)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					116		858
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			$ 993		$ 993		$ 1,529		$ 1,501
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					(557)		27
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Change in collateral					$ (141)		$ 29
Purchases					494		322
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					(144)		(95)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Included in payable for Zion Station decommissioning							(2)
Included in regulatory assets/liabilities					5		(22)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					(15)		(61)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					2		84
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					(197)		(254)
Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances					(3)
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Consolidation, Eliminations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					(16)		(18)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			0		$ 0		$ 0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					0		0
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Change in collateral					$ 0		$ 0
Purchases					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Included in payable for Zion Station decommissioning							0
Included in regulatory assets/liabilities					16		18
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					0		0
Fair Value, Inputs, Level 3 [Member] | Potomac Electric Power Company [Member] | 6311 Life Insurance [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			19		$ 19		$ 19		18
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					3		5
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Purchases					$ (3)		$ (3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		1
The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities					3		3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses					3		3
Fair Value, Inputs, Level 3 [Member] | Delmarva Power and Light Company [Member] | 6311 Life Insurance [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			0		$ 0		$ 0		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					0		0
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Purchases					$ 0		$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		1
The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses					0		0
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					114		858
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					16		18
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			1,231		$ 1,231		$ 1,776		1,708
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					(560)		27
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Change in collateral					$ (141)		$ 29
Purchases					494		322
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					(144)		(95)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Period Increase (Decrease)					29		55
Included in payable for Zion Station decommissioning							(2)
Included in regulatory assets/liabilities					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					(15)		(61)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					2		84
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					(197)		(254)
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					5		2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					16		18
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			677		$ 677		$ 670		605
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					7		4
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Change in collateral					$ 0		$ 0
Purchases					143		146
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					(144)		(95)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Included in payable for Zion Station decommissioning							0
Included in regulatory assets/liabilities					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					(1)		(8)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					0		4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					(14)		(4)
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			19		$ 19		$ 22		50
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					0		0
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Change in collateral					$ 0		$ 0
Purchases					2		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Included in payable for Zion Station decommissioning							(2)
Included in regulatory assets/liabilities					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					(5)		(28)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					0		0
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member] | Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					109		856
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			493		$ 493		$ 1,051		1,050
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	[1]				(568)		22
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Change in collateral					$ (141)		$ 29
Purchases					342	[2]	144
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Included in payable for Zion Station decommissioning							0
Included in regulatory assets/liabilities					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					(9)		(25)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					1		80
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					(183)		(249)
Indefinite-lived Intangible Assets Acquired					168
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member] | Other Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			42		$ 42		$ 33		3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					1		1
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Change in collateral					$ 0		$ 0
Purchases					7		30
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Included in payable for Zion Station decommissioning							0
Included in regulatory assets/liabilities					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					1		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					0		(1)
Fair Value, Inputs, Level 3 [Member] | Commonwealth Edison Co [Member] | Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[3]				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	[3]		(258)		(258)		(247)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	[3]				$ 0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	[3]						$ (247)		(207)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	[3]				0		0
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Change in collateral	[3]				$ 0		$ 0
Purchases	[3]				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[3]				0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Included in payable for Zion Station decommissioning	[3]						0
Included in regulatory assets/liabilities	[3]				(11)		(40)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[3]				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	[3]				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	[3]				0		0
Fair Value, Inputs, Level 3 [Member] | Commonwealth Edison Co [Member] | Derivative [Member]
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[3]						0
Successor [Member] | Fair Value, Inputs, Level 3 [Member] | Pepco Holdings LLC [Member] | 6311 Life Insurance [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[4]		2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	[4]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	[4]		$ 20		20		0	$ 20
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	[4]		3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances			$ (3)	[4]			(3)
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Change in collateral	[4]		0
Purchases	[4]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[4]		0
The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities			2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses			2
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Included in regulatory assets/liabilities	[4]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[4]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	[4]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	[4]		0
Predecessor [Member] | Fair Value, Inputs, Level 3 [Member] | Pepco Holdings LLC [Member] | Preferred Stock [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		$ 0	18		18		$ 18		3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description		(18)					15
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances		$ 0					$ 0
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0					0
The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities		0					15
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses		0					15
Predecessor [Member] | Fair Value, Inputs, Level 3 [Member] | Pepco Holdings LLC [Member] | 6311 Life Insurance [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		$ 20	$ 19		$ 19		$ 19		$ 19
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description		1					5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances		$ 0
Fair Value Measurement With Unobservable inputs reconciliation Recurring Asset Liability Gain Loss Abstract [Abstract]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0					$ 2
The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities		1					3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, (Sales), Issuances, (Settlements) [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses		$ 1					$ 3
[1]	Includes a reduction for the reclassification of $677 million and $834 million of realized gains due to the settlement of derivative contracts for the years ended December 31, 2016 and 2015, respectively.
[2]	Includes $168 million of fair value from contracts acquired as a result of portfolio acquisitions.
[3]	Includes $29 million of decreases in fair value and an increase for realized losses due to settlements of $18 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the year ended December 31, 2016. Includes $55 million of decreases in fair value and a reduction for realized losses due to settlements of $(15) million for the year ended December 31, 2015.
[4]	Successor period represents activity from March 24, 2016 to December 31, 2016. See tables below for PHI's predecessor periods, as well as activity for Pepco and DPL for the year ended December 31, 2016.

Fair Value of Financial Asse107

Fair Value of Financial Assets and Liabilities - Narrative (Details)	Dec. 31, 2016USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward Power Basis	$ 2.65
Forward Gas Basis	0.34
Middle market lending [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	284,000,000
Private Equity Funds [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	65,000,000
Real Estate Funds [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 205,000,000

Fair Value of Financial Asse108

Fair Value of Financial Assets and Liabilities - Fair Value Assets and Liabilities Measure on Recurring Basis Gain Loss Included in Earnings (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended		12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016		Dec. 31, 2016		Dec. 31, 2015	Mar. 24, 2016	Dec. 31, 2014
Operating Revenue [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings					$ (477)		$ 67
Included in other comprehensive income					154		858
Purchased Fuel and Electric [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings					(91)		(45)
Included in other comprehensive income					(45)		(2)
Other, net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	[1]				10		4
Included in other comprehensive income	[1]				7		2
Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					18		(15)
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings					(677)		(834)
Exelon Generation Co L L C [Member] | Operating Revenue [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings					(477)		67
Included in other comprehensive income					154		858
Exelon Generation Co L L C [Member] | Purchased Fuel and Electric [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings					(91)		(45)
Included in other comprehensive income					(45)		(2)
Exelon Generation Co L L C [Member] | Other, net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	[1]				7		4
Included in other comprehensive income	[1]				5		2
Potomac Electric Power Company [Member] | Other, net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings					3		5
Included in other comprehensive income					3		3
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			$ 993		993		1,529		$ 1,501
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					$ (15)		$ (61)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					(557)		27
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					$ 0		$ 0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable							2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities					5		(22)
Change in collateral					(141)		29
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases					494		322
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					(144)		(95)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					2		84
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					(197)		(254)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					116		858
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			1,231		1,231		1,776		1,708
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					$ (15)		$ (61)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					(560)		27
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					$ 16		$ 18
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable							2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities					0		0
Change in collateral					(141)		29
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases					494		322
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					(144)		(95)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					2		84
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					(197)		(254)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					114		858
6311 Life Insurance [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances					(3)
6311 Life Insurance [Member] | Fair Value, Inputs, Level 3 [Member] | Potomac Electric Power Company [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			19		$ 19		$ 19		18
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					3		5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases					$ (3)		$ (3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		1
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses					3		3
Other Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			42		42		33		3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					$ 0		$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					1		1
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					$ 0		$ 0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable							0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities					0		0
Change in collateral					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases					7		30
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					1		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					0		(1)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0		0
Nuclear Decommissioning Trust Fund Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			677		677		670		605
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					$ (1)		$ (8)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					7		4
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					$ 16		$ 18
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable							0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities					0		0
Change in collateral					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases					143		146
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					(144)		(95)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					0		4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					(14)		(4)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					5		2
Derivative [Member] | Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			493		493		1,051		1,050
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					$ (9)		$ (25)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	[2]				(568)		22
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					$ 0		$ 0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable							0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities					0		0
Change in collateral					(141)		29
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases					342	[3]	144
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					1		80
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					(183)		(249)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					109		856
Derivative [Member] | Fair Value, Inputs, Level 3 [Member] | Commonwealth Edison Co [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	[4]						(247)		(207)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[4]				$ 0		$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	[4]				0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	[4]				$ 0		$ 0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	[4]						0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	[4]				(11)		(40)
Change in collateral	[4]				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[4]				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[4]				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	[4]				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	[4]				0		0
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	[4]		(258)		(258)		(247)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[4]				0		0
Pledged Assets For Zion Station Decommissioning [Member] | Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			19		19		22		50
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					$ (5)		$ (28)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					$ 0		$ 0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable							2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities					0		0
Change in collateral					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases					2		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0		0
Derivative [Member] | Fair Value, Inputs, Level 3 [Member] | Commonwealth Edison Co [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[4]						0
Derivative [Member] | Fair Value, Inputs, Level 3 [Member] | Consolidation, Eliminations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			0		0		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales					$ 0		$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates					$ (16)		$ (18)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable							0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities					16		18
Change in collateral					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3					0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)					0		0
Successor [Member] | Pepco Holdings LLC [Member] | Other, net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			3
Included in other comprehensive income			2
Successor [Member] | 6311 Life Insurance [Member] | Fair Value, Inputs, Level 3 [Member] | Pepco Holdings LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	[5]		20		20		0	$ 20
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	[5]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances			$ (3)	[5]			(3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	[5]		3
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	[5]		$ 0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	[5]		0
Change in collateral	[5]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	[5]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	[5]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	[5]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	[5]		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses			2
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[5]		2
Predecessor [Member] | Pepco Holdings LLC [Member] | Other, net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		$ (17)					20
Included in other comprehensive income		1					18
Predecessor [Member] | 6311 Life Insurance [Member] | Fair Value, Inputs, Level 3 [Member] | Pepco Holdings LLC [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		20	$ 19		$ 19		$ 19		$ 19
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances		$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description		1					5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		$ 0					$ 2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses		$ 1					$ 3
[1]	Other, net activity consists of realized and unrealized gains (losses) included in income for the NDT funds held by Generation and the life insurance contracts held by Pepco.
[2]	Includes a reduction for the reclassification of $677 million and $834 million of realized gains due to the settlement of derivative contracts for the years ended December 31, 2016 and 2015, respectively.
[3]	Includes $168 million of fair value from contracts acquired as a result of portfolio acquisitions.
[4]	Includes $29 million of decreases in fair value and an increase for realized losses due to settlements of $18 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the year ended December 31, 2016. Includes $55 million of decreases in fair value and a reduction for realized losses due to settlements of $(15) million for the year ended December 31, 2015.
[5]	Successor period represents activity from March 24, 2016 to December 31, 2016. See tables below for PHI's predecessor periods, as well as activity for Pepco and DPL for the year ended December 31, 2016.

Fair Value of Financial Asse109

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details) - USD ($)		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash collateral excluded		$ 61,000,000		$ 201,000,000
Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities, fair value	[1]	333,000,000		248,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets, fair value		435,000,000	[2],[3]	857,000,000	[4],[5]
Exelon Generation Co L L C [Member] | Not Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities, fair value		(3,000,000)	[2],[3]	(7,000,000)	[4],[5]
Exelon Generation Co L L C [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward power price assets		11	[3]	11	[5]
Forward gas price assets		1.72	[3]	1.18	[5]
Exelon Generation Co L L C [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] | Not Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward power price assets		19	[3]	13	[5]
Exelon Generation Co L L C [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward power price assets		130	[3]	88	[5]
Forward gas price assets		9.2	[3]	8.95	[5]
Exelon Generation Co L L C [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] | Not Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward power price assets		$ 79	[3]	$ 78	[5]
Exelon Generation Co L L C [Member] | Option Model Valuation Technique [Member] | Minimum [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Volatility percentage		8.00%	[3]	5.00%	[5]
Exelon Generation Co L L C [Member] | Option Model Valuation Technique [Member] | Maximum [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Volatility percentage		173.00%	[3]	152.00%	[5]
Commonwealth Edison Co [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities, fair value		$ (258,000,000)		$ (247,000,000)
Commonwealth Edison Co [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketability Reserve		3.00%		3.50%
Renewable factor		89.00%		87.00%
Commonwealth Edison Co [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward heat rate	[6]	8.00%
Commonwealth Edison Co [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] | Not Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward heat rate	[7]			9.00%
Commonwealth Edison Co [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward heat rate	[7]			10.00%
Marketability Reserve		8.00%		7.00%
Renewable factor		121.00%		128.00%
Commonwealth Edison Co [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] | Designated as Hedging Instrument [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward heat rate	[6]	9.00%
[1]	(c)Amount represents the net fair value of out-of-the-money derivative contracts containing credit-risk related contingent features after considering the mitigating effects of offsetting positions under master netting arrangements and reflects the actual net liability upon which any potential contingent collateral obligations would be based.
[2]	The fair values do not include cash collateral posted on level three positions of $61 million as of December 31, 2016.
[3]	The valuation techniques, unobservable inputs and ranges are the same for the asset and liability positions.
[4]	The fair values do not include cash collateral posted on level three positions of $201 million as of December 31, 2015
[5]	The valuation techniques, unobservable inputs and ranges are the same for the asset and liability positions.
[6]	Quoted forward natural gas rates are utilized to project the forward power curve for the delivery of energy at specified future dates. The natural gas curve is extrapolated beyond its observable period to the end of the contract’s delivery.
[7]	Quoted forward natural gas rates are utilized to project the forward power curve for the delivery of energy at specified future dates. The natural gas curve is extrapolated beyond its observable period to the end of the contract’s delivery.

Derivative Financial Instrum110

Derivative Financial Instruments - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Jun. 30, 2016USD ($)	Jun. 30, 2015USD ($)	Dec. 31, 2016USD ($)GWh		Dec. 31, 2015USD ($)GWh		Dec. 31, 2014USD ($)GWh	Mar. 31, 2016USD ($)
Derivative [Line Items]
Proprietary trading activities volume | GWh			6,179		7,310		10,571
Derivative, notional amount			$ 2,918,000		$ 1,774,000
Pre-tax net income impact associated with a hypothetical 10% increase in interest rates - exclusive upper bound			7,000
Ineffective portion recognized in income			14,000		17,000
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	$ 3,000
Derivative, Gain (Loss) on Derivative, Net	3,000
Mark-to-market derivative liabilities			392,000		374,000
Mark-to-market derivative liabilities			282,000		205,000
Derivative, collateral, right to reclaim cash			29,000		52,000
Cash collateral held			(9,000)
Letters of credit held			16,000
Interest Rate Fair Value Hedge Asset at Fair Value			16,000
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amount of preissuance interest rate cash flow hedge derivatives			659,000
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, notional amount	100,000		800,000					$ 600,000
Derivative Asset			28,000		54,000
Mark-to-market derivative liabilities			4,000		8,000
Mark-to-market derivative liabilities			8,000		8,000
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative, notional amount	90,000							100,000
Interest Rate Swap [Member] | PHI Merger [Member]
Derivative [Line Items]
Derivative, notional amount		$ 2,400,000
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset			16,000
Mark-to-market derivative liabilities			0
Mark-to-market derivative liabilities			0
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative, notional amount			800,000		800,000
Derivative Asset			16,000		25,000
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | ExGen Texas Power [Member]
Derivative [Line Items]
Derivative, notional amount			495,000
Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | ExGen Texas Power [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities			9,000
Derivative [Member]
Derivative [Line Items]
Derivative Asset			1,381,000		2,069,000
Mark-to-market derivative liabilities			388,000		366,000
Mark-to-market derivative liabilities			274,000		197,000
Designated as Hedging Instrument [Member] | PHI Merger [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net		$ (64,000)
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Net receivable from electric utility			26,000
Credit exposure under off system sales			8,000
Incremental collateral for loss of investment grade credit rating			62,000
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities			153,000		150,000
Mark-to-market derivative liabilities			263,000		182,000
Derivative, collateral, right to reclaim cash			8,000		3,000
Letters of credit posted			284,000		497,000
Cash collateral held			(24,000)		(21,000)
Letters of credit held			28,000		78,000
Cash collateral posted			347,000		1,267,000
Incremental collateral for loss of investment grade credit rating			1,900,000		2,000,000
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Other Solar Projects [Member]
Derivative [Line Items]
Notional amount of interest rate swaps acquired from merger								24,000
Exelon Generation Co L L C [Member] | Total Cash Flow Hedges [Member]
Derivative [Line Items]
Cash flow hedge activity impact on pre-tax net income based on reclassification adjustment from accumulated other comprehensive income					2,000		$ 195,000
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Asset			12,000		29,000
Mark-to-market derivative liabilities			4,000		8,000
Mark-to-market derivative liabilities			8,000		8,000
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Other Solar Projects [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Notional amount of interest rate swaps acquired from merger								$ 25,000
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset			0		0
Mark-to-market derivative liabilities			3,000		8,000
Mark-to-market derivative liabilities			7,000		8,000
Exelon Generation Co L L C [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, notional amount			164,000
Exelon Generation Co L L C [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities			1,000
Exelon Generation Co L L C [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Derivative, notional amount			85,000
Exelon Generation Co L L C [Member] | Derivative [Member]
Derivative [Line Items]
Derivative Asset			1,381,000	[1]	2,069,000	[2]
Mark-to-market derivative liabilities			149,000	[1]	142,000	[2]
Mark-to-market derivative liabilities			$ 255,000	[1]	174,000	[2]
Commonwealth Edison Co [Member]
Derivative [Line Items]
Term of contract			20 years
Mark-to-market derivative liabilities			$ (239,000)		224,000
Mark-to-market derivative liabilities			19,000		23,000
Net receivable from electric utility			14,000
Credit exposure under off system sales			1,000
Cash collateral held			(3,000)
Letters of credit held			19,000
Incremental collateral for loss of investment grade credit rating			19,000
PECO Energy Co [Member]
Derivative [Line Items]
Net receivable from electric utility			33,000
Incremental collateral for loss of investment grade credit rating			31,000
Pepco Holdings LLC [Member] | Predecessor [Member]
Derivative [Line Items]
Derivative Asset					18,000
Mark-to-market derivative liabilities					0
Mark-to-market derivative liabilities					0
Pepco Holdings LLC [Member] | Derivative [Member] | Successor [Member]
Derivative [Line Items]
Derivative Asset			0
Mark-to-market derivative liabilities			0
Mark-to-market derivative liabilities			0
Potomac Electric Power Company [Member]
Derivative [Line Items]
Net receivable from electric utility			44,000
Delmarva Power and Light Company [Member]
Derivative [Line Items]
Net receivable from electric utility			16,000
Incremental collateral for loss of investment grade credit rating			10,000
Delmarva Power and Light Company [Member] | Energy Related Derivative [Member]
Derivative [Line Items]
Brokered Natural Gas Margin Revenue			2,750
Delmarva Power and Light Company [Member] | Derivative [Member]
Derivative [Line Items]
Derivative Asset			0		0	[2]
Mark-to-market derivative liabilities			0		0	[2]
Mark-to-market derivative liabilities			0		$ 0	[2]
Atlantic City Electric Company [Member]
Derivative [Line Items]
Net receivable from electric utility			$ 9,000
Minimum [Member]
Derivative [Line Items]
Expected generation hedged in next twelve months			91.00%
Expected generation hedged in year two			56.00%
Expected generation hedged in year three			28.00%
Minimum [Member] | Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Estimated percentage of natural gas purchases hedged			10.00%
Maximum [Member]
Derivative [Line Items]
Expected generation hedged in next twelve months			94.00%
Expected generation hedged in year two			59.00%
Expected generation hedged in year three			31.00%
Maximum [Member] | Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Estimated percentage of natural gas purchases hedged			20.00%
Senior Notes [Member]
Derivative [Line Items]
Debt Instrument, Face Amount	$ 4,200,000
Senior Notes [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Debt Instrument, Face Amount			$ 750,000
[1]	Current and noncurrent assets are shown net of collateral of $100 million and $72 million, respectively, and current and noncurrent liabilities are shown net of collateral of $95 million and $62 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $329 million at December 31, 2016.
[2]	Current and noncurrent assets are shown net of collateral of $352 million and $180 million, respectively, and current and noncurrent liabilities are shown net of collateral of $480 million and $222 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,234 million at December 31, 2015.

Derivative Financial Instrum111

Derivative Financial Instruments - Summary of Interest Rate and Foreign Currency Hedges (Details) - USD ($) $ in Millions		Dec. 31, 2016		Dec. 31, 2015
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		$ 917		$ 1,365
Mark-to-market derivative assets (noncurrent assets)		492		758
Derivative Liability, Current		282		205
Derivative Liability, Noncurrent		392		374
Total mark-to-market derivative net assets (liabilities)		1		5
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		917		1,365
Mark-to-market derivative assets (noncurrent assets)		476		733
Derivative Liability, Current		263		182
Derivative Liability, Noncurrent		153		150
Interest Rate Swap [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		8		15
Mark-to-market derivative assets (noncurrent assets)		20		39
Total mark-to-market derivative assets		28		54
Derivative Liability, Current		8		8
Derivative Liability, Noncurrent		4		8
Derivative Liability		12		16
Total mark-to-market derivative net assets (liabilities)		16		38
Interest Rate Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		8		15
Mark-to-market derivative assets (noncurrent assets)		4		14
Total mark-to-market derivative assets		12		29
Derivative Liability, Current		8		8
Derivative Liability, Noncurrent		4		8
Derivative Liability		12		16
Total mark-to-market derivative net assets (liabilities)		0		13
Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		909		1,350
Mark-to-market derivative assets (noncurrent assets)		472		719
Total mark-to-market derivative assets		1,381		2,069
Derivative Liability, Current		274		197
Derivative Liability, Noncurrent		388		366
Derivative Liability		662		563
Total mark-to-market derivative net assets (liabilities)		719		1,506
Derivative [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		909	[1]	1,350	[2]
Mark-to-market derivative assets (noncurrent assets)		472	[1]	719	[2]
Total mark-to-market derivative assets		1,381	[1]	2,069	[2]
Derivative Liability, Current		255	[1]	174	[2]
Derivative Liability, Noncurrent		149	[1]	142	[2]
Derivative Liability		404	[1]	316	[2]
Total mark-to-market derivative net assets (liabilities)		977	[1]	1,753	[2]
Proprietary Trading [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		55		108
Mark-to-market derivative assets (noncurrent assets)		21		22
Total mark-to-market derivative assets		76		130
Derivative Liability, Current		54		94
Derivative Liability, Noncurrent		25		33
Derivative Liability		79		127
Total mark-to-market derivative net assets (liabilities)		(3)		3
Collateral and Netting | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		(2,769)	[3]	(3,994)
Mark-to-market derivative assets (noncurrent assets)		(1,016)	[3]	(1,163)
Total mark-to-market derivative assets		(3,785)	[3]	(5,157)
Derivative Liability, Current		(2,964)	[3]	(4,827)
Derivative Liability, Noncurrent		(1,150)	[3]	(1,564)
Derivative Liability		(4,114)	[3]	(6,391)
Total mark-to-market derivative net assets (liabilities)		329	[3]	1,234
Collateral and Netting | Interest Rate Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		(13)		(5)	[4]
Mark-to-market derivative assets (noncurrent assets)		(8)		(1)	[4]
Total mark-to-market derivative assets		(21)		(6)	[4]
Derivative Liability, Current		(14)		(11)	[4]
Derivative Liability, Noncurrent		(9)		(4)	[4]
Derivative Liability		(23)		(15)	[4]
Total mark-to-market derivative net assets (liabilities)		2		9	[4]
Other Segments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)				0
Mark-to-market derivative assets (noncurrent assets)				25
Total mark-to-market derivative assets				25
Derivative Liability, Current				0
Derivative Liability, Noncurrent				0
Derivative Liability				0
Total mark-to-market derivative net assets (liabilities)				25
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		0
Mark-to-market derivative assets (noncurrent assets)		16
Total mark-to-market derivative assets		16
Derivative Liability, Current		0
Derivative Liability, Noncurrent		0
Derivative Liability		0
Total mark-to-market derivative net assets (liabilities)		16
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		0		0
Mark-to-market derivative assets (noncurrent assets)		0		0
Total mark-to-market derivative assets		0		0
Derivative Liability, Current		7		8
Derivative Liability, Noncurrent		3		8
Derivative Liability		10		16
Total mark-to-market derivative net assets (liabilities)		(10)		(16)
Designated as Hedging Instrument [Member] | Currency Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		17		10
Mark-to-market derivative assets (noncurrent assets)		11		10
Total mark-to-market derivative assets		28		20
Derivative Liability, Current		13		2
Derivative Liability, Noncurrent		8		1
Derivative Liability		21		3
Total mark-to-market derivative net assets (liabilities)		7		17
Designated as Hedging Instrument [Member] | Other Segments [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)				0
Mark-to-market derivative assets (noncurrent assets)				25
Total mark-to-market derivative assets				25
Derivative Liability, Current				0
Derivative Liability, Noncurrent				0
Derivative Liability				0
Total mark-to-market derivative net assets (liabilities)				25
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	[5]	4		10
Mark-to-market derivative assets (noncurrent assets)	[5]	1		5
Total mark-to-market derivative assets	[5]	5		15
Derivative Liability, Current	[5]	2		9
Derivative Liability, Noncurrent	[5]	2		3
Derivative Liability	[5]	4		12
Total mark-to-market derivative net assets (liabilities)	[5]	$ 1		$ 3
[1]	Current and noncurrent assets are shown net of collateral of $100 million and $72 million, respectively, and current and noncurrent liabilities are shown net of collateral of $95 million and $62 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $329 million at December 31, 2016.
[2]	Current and noncurrent assets are shown net of collateral of $352 million and $180 million, respectively, and current and noncurrent liabilities are shown net of collateral of $480 million and $222 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,234 million at December 31, 2015.
[3]	Exelon, Generation, PHI and DPL net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above.
[4]	Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures subject to a master netting or similar agreement, such as accrued interest, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above.
[5]	Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts between the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates.

Derivative Financial Instrum112

Derivative Financial Instruments - Summary of Gains and Losses on Hedges (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Gain (Loss) on Swaps/Borrowings		$ (3)
Interest Expense [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Gain (Loss) on Swaps/Borrowings			$ 23	$ 14	$ (1)
Interest Expense [Member] | Fair Value Hedging [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Gain (Loss) on Swaps/Borrowings			(9)	3	14
Interest Expense [Member] | Fair Value Hedging [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Gain (Loss) on Swaps/Borrowings	[1]		0	0	2
Interest Expense [Member] | Fair Value Hedging [Member] | Exelon Generation Co L L C [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Gain (Loss) on Swaps/Borrowings	[1]		$ 0	(1)	(16)
Gain (Loss) on Fair Value Hedges Recognized in Earnings				$ (1)	(17)
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net					$ 4
[1]	For the years ended December 31, 2015 and 2014, the loss on Generation swaps included $(1) million and $(17) million realized in earnings, respectively, with an immaterial amount and $4 million excluded from hedge effectiveness testing, respectively.

Derivative Financial Instrum113

Derivative Financial Instruments - Summary of Derivative Fair Value Balances (Details) - USD ($) $ in Millions	Dec. 31, 2016		Dec. 31, 2015
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	$ 917		$ 1,365
Mark-to-market derivative assets (noncurrent assets)	492		758
Derivative Liability, Current	(282)		(205)
Derivative Liability, Noncurrent	(392)		(374)
Total mark-to-market derivative net assets (liabilities)	1		5
Accumulated other comprehensive loss, net	(2,660)		(2,624)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	917		1,365
Mark-to-market derivative assets (noncurrent assets)	476		733
Derivative Liability, Current	(263)		(182)
Derivative Liability, Noncurrent	(153)		(150)
Accumulated other comprehensive loss, net	(54)		(63)
Commonwealth Edison Co [Member]
Derivative [Line Items]
Derivative Liability, Current	(19)		(23)
Derivative Liability, Noncurrent	239		(224)
Pepco Holdings LLC [Member] | Predecessor [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			18
Mark-to-market derivative assets (noncurrent assets)			0
Total mark-to-market derivative assets			18
Derivative Liability, Current			0
Derivative Liability, Noncurrent			0
Total mark-to-market derivative liabilities			0
Total mark-to-market derivative net assets (liabilities)			18
Accumulated other comprehensive loss, net			(36)
Pepco Holdings LLC [Member] | Successor [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	0
Accumulated other comprehensive loss, net	0
Proprietary Trading [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	55		108
Mark-to-market derivative assets (noncurrent assets)	21		22
Total mark-to-market derivative assets	76		130
Derivative Liability, Current	(54)		(94)
Derivative Liability, Noncurrent	(25)		(33)
Total mark-to-market derivative liabilities	(79)		(127)
Total mark-to-market derivative net assets (liabilities)	(3)		3
Collateral and Netting | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	(2,769)	[1]	(3,994)
Mark-to-market derivative assets (noncurrent assets)	(1,016)	[1]	(1,163)
Total mark-to-market derivative assets	(3,785)	[1]	(5,157)
Derivative Liability, Current	2,964	[1]	4,827
Derivative Liability, Noncurrent	1,150	[1]	1,564
Total mark-to-market derivative liabilities	4,114	[1]	6,391
Total mark-to-market derivative net assets (liabilities)	329	[1]	1,234
Collateral and Netting | Delmarva Power and Light Company [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	(2)	[1]	0
Mark-to-market derivative assets (noncurrent assets)	0	[1]	0
Total mark-to-market derivative assets	(2)	[1]	0
Derivative Liability, Current	0	[1]	2
Derivative Liability, Noncurrent	0	[1]	0
Total mark-to-market derivative liabilities	0	[1]	2
Total mark-to-market derivative net assets (liabilities)	(2)	[1]	2
Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	909		1,350
Mark-to-market derivative assets (noncurrent assets)	472		719
Total mark-to-market derivative assets	1,381		2,069
Derivative Liability, Current	(274)		(197)
Derivative Liability, Noncurrent	(388)		(366)
Total mark-to-market derivative liabilities	(662)		(563)
Total mark-to-market derivative net assets (liabilities)	719		1,506
Derivative [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	909	[2]	1,350	[3]
Mark-to-market derivative assets (noncurrent assets)	472	[2]	719	[3]
Total mark-to-market derivative assets	1,381	[2]	2,069	[3]
Derivative Liability, Current	(255)	[2]	(174)	[3]
Derivative Liability, Noncurrent	(149)	[2]	(142)	[3]
Total mark-to-market derivative liabilities	(404)	[2]	(316)	[3]
Total mark-to-market derivative net assets (liabilities)	977	[2]	1,753	[3]
Derivative [Member] | Delmarva Power and Light Company [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	0		0	[3]
Mark-to-market derivative assets (noncurrent assets)	0		0	[3]
Total mark-to-market derivative assets	0		0	[3]
Derivative Liability, Current	0		0	[3]
Derivative Liability, Noncurrent	0		0	[3]
Total mark-to-market derivative liabilities	0		0	[3]
Total mark-to-market derivative net assets (liabilities)	0		0	[3]
Derivative [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	0
Mark-to-market derivative assets (noncurrent assets)	0
Total mark-to-market derivative assets	0
Derivative Liability, Current	0
Derivative Liability, Noncurrent	0
Total mark-to-market derivative liabilities	0
Total mark-to-market derivative net assets (liabilities)	0
Interest Rate Swap [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	8		15
Mark-to-market derivative assets (noncurrent assets)	20		39
Total mark-to-market derivative assets	28		54
Derivative Liability, Current	(8)		(8)
Derivative Liability, Noncurrent	(4)		(8)
Total mark-to-market derivative liabilities	(12)		(16)
Total mark-to-market derivative net assets (liabilities)	16		38
Interest Rate Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	8		15
Mark-to-market derivative assets (noncurrent assets)	4		14
Total mark-to-market derivative assets	12		29
Derivative Liability, Current	(8)		(8)
Derivative Liability, Noncurrent	(4)		(8)
Total mark-to-market derivative liabilities	(12)		(16)
Total mark-to-market derivative net assets (liabilities)	0		13
Economic Hedges [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	3,623		5,236
Mark-to-market derivative assets (noncurrent assets)	1,467		1,860
Total mark-to-market derivative assets	5,090		7,096
Derivative Liability, Current	(3,165)		(4,907)
Derivative Liability, Noncurrent	(1,274)		(1,673)
Total mark-to-market derivative liabilities	(4,439)		(6,580)
Total mark-to-market derivative net assets (liabilities)	651		516
Economic Hedges [Member] | Commonwealth Edison Co [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	0		0
Mark-to-market derivative assets (noncurrent assets)	0		0	[4]
Total mark-to-market derivative assets	0		0
Derivative Liability, Current	(19)		(23)	[4]
Derivative Liability, Noncurrent	(239)		(224)	[4]
Total mark-to-market derivative liabilities	(258)		(247)	[4]
Total mark-to-market derivative net assets (liabilities)	(258)		(247)	[4]
Economic Hedges [Member] | Delmarva Power and Light Company [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	2		0	[4]
Mark-to-market derivative assets (noncurrent assets)	0		0	[4]
Total mark-to-market derivative assets	2		0	[4]
Derivative Liability, Current	0		(2)	[4]
Derivative Liability, Noncurrent	0		0	[4]
Total mark-to-market derivative liabilities	0		(2)	[4]
Total mark-to-market derivative net assets (liabilities)	2		(2)	[4]
Corporate, Non-Segment [Member] | Derivative [Member] | Pepco Holdings LLC [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			18
Mark-to-market derivative assets (noncurrent assets)			0
Total mark-to-market derivative assets			18
Derivative Liability, Current			0
Derivative Liability, Noncurrent			0
Total mark-to-market derivative liabilities			0
Total mark-to-market derivative net assets (liabilities)			18
Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Current assets collateral offset	(100)		352
Noncurrent assets collateral offset	(72)		180
Current liabilities collateral offset	(95)		480
Collateral Amount Offset Against Fair Value Of Derivative Current Noncurrent Liability	62		(222)
Total cash collateral received net of cash collateral posted	329		(1,234)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	0
Mark-to-market derivative assets (noncurrent assets)	16
Total mark-to-market derivative assets	16
Derivative Liability, Current	0
Derivative Liability, Noncurrent	0
Total mark-to-market derivative liabilities	0
Total mark-to-market derivative net assets (liabilities)	16
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	0		0
Mark-to-market derivative assets (noncurrent assets)	0		0
Total mark-to-market derivative assets	0		0
Derivative Liability, Current	(7)		(8)
Derivative Liability, Noncurrent	(3)		(8)
Total mark-to-market derivative liabilities	(10)		(16)
Total mark-to-market derivative net assets (liabilities)	(10)		(16)
Designated as Hedging Instrument [Member] | Currency Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)	17		10
Mark-to-market derivative assets (noncurrent assets)	11		10
Total mark-to-market derivative assets	28		20
Derivative Liability, Current	(13)		(2)
Derivative Liability, Noncurrent	(8)		(1)
Total mark-to-market derivative liabilities	(21)		(3)
Total mark-to-market derivative net assets (liabilities)	$ 7		$ 17
[1]	Exelon, Generation, PHI and DPL net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above.
[2]	Current and noncurrent assets are shown net of collateral of $100 million and $72 million, respectively, and current and noncurrent liabilities are shown net of collateral of $95 million and $62 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $329 million at December 31, 2016.
[3]	Current and noncurrent assets are shown net of collateral of $352 million and $180 million, respectively, and current and noncurrent liabilities are shown net of collateral of $480 million and $222 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,234 million at December 31, 2015.
[4]	Includes current and noncurrent liabilities relating to floating-to-fixed energy swap contracts with unaffiliated suppliers.

Derivative Financial Instrum114

Derivative Financial Instruments - Summary of AOCI related to Cash Flow Hedges (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss, net		$ (2,660)	$ (2,624)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(150)	(196)	[2],[3]
Other, net [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax			10
Interest Expense [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax		5	4
Exelon Generation Co L L C [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss, net		(54)	(63)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(13)	(5)	[2],[3]
Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss, net		(17)	(19)		$ (28)
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		(6)	(12)
Cash Flow Hedging [Member] | Other, net [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			16
Cash Flow Hedging [Member] | Interest Expense [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		8	7
Cash Flow Hedging [Member] | Operating Revenue [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			(2)
Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Accumulated other comprehensive loss, net		(19)	(21)		$ (18)
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		(6)	(8)
Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member] | Other, net [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			0
Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member] | Interest Expense [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		$ 8	7
Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member] | Operating Revenue [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax			$ (2)
[1]	Amounts in parenthesis represent a decrease in net income.
[2]	All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.
[3]	See next tables for details about these reclassifications.

Derivative Financial Instrum115

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ (24,000,000)	$ 367,000,000	$ (716,000,000)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(41,000,000)	357,000,000	(693,000,000)
Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	1,000,000	(8,000,000)	(26,000,000)
Interest Expense [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts		100,000,000	(100,000,000)
Commodity Contract [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	213,000,000	404,000,000	(607,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(244,000,000)	(154,000,000)	8,000,000
Unrealized Gain (Loss) on Commodity Contracts	(31,000,000)	250,000,000	(599,000,000)
Commodity Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	23,000,000	8,000,000	(1,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(21,000,000)	(14,000,000)	(29,000,000)
Unrealized Gain (Loss) on Commodity Contracts	2,000,000	(6,000,000)	(30,000,000)
Commodity Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge		0	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		0	0
Unrealized Gain (Loss) on Commodity Contracts		0	0
Foreign Exchange Contract [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(2,000,000)	49,000,000	(92,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(8,000,000)	58,000,000	(2,000,000)
Unrealized Gain (Loss) on Derivatives	(10,000,000)	107,000,000	(94,000,000)
Foreign Exchange Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(1,000,000)	8,000,000	1,000,000
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	(10,000,000)	3,000,000
Unrealized Gain (Loss) on Derivatives	(1,000,000)	(2,000,000)	4,000,000
Foreign Exchange Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge		36,000,000	(100,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		64,000,000	0
Unrealized Gain (Loss) on Derivatives		100,000,000	(100,000,000)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(40,000,000)	249,000,000	(635,000,000)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(41,000,000)	257,000,000	(593,000,000)
Exelon Generation Co L L C [Member] | Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(500,000,000)	203,000,000	(174,000,000)
Exelon Generation Co L L C [Member] | Purchased Power And Fuel [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	459,000,000	54,000,000	(417,000,000)
Exelon Generation Co L L C [Member] | Interest Expense [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts			(2,000,000)
Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	213,000,000	404,000,000	(607,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(244,000,000)	(154,000,000)	8,000,000
Unrealized Gain (Loss) on Commodity Contracts	(31,000,000)	250,000,000	(599,000,000)
Exelon Generation Co L L C [Member] | Commodity Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	5,000,000	759,000,000	(413,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(495,000,000)	(563,000,000)	231,000,000
Unrealized Gain (Loss) on Commodity Contracts	(490,000,000)	196,000,000	(182,000,000)
Exelon Generation Co L L C [Member] | Commodity Contract [Member] | Purchased Power And Fuel [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	208,000,000	(355,000,000)	(194,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	251,000,000	409,000,000	(223,000,000)
Unrealized Gain (Loss) on Commodity Contracts	459,000,000	54,000,000	(417,000,000)
Exelon Generation Co L L C [Member] | Commodity Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge			0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net			0
Unrealized Gain (Loss) on Commodity Contracts			0
Exelon Generation Co L L C [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(2,000,000)	13,000,000	8,000,000
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(8,000,000)	(6,000,000)	(2,000,000)
Unrealized Gain (Loss) on Derivatives	(10,000,000)	7,000,000	6,000,000
Exelon Generation Co L L C [Member] | Foreign Exchange Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(2,000,000)	13,000,000	10,000,000
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(8,000,000)	(6,000,000)	(2,000,000)
Unrealized Gain (Loss) on Derivatives	(10,000,000)	7,000,000	8,000,000
Exelon Generation Co L L C [Member] | Foreign Exchange Contract [Member] | Purchased Power And Fuel [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	0	0	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0
Unrealized Gain (Loss) on Derivatives	$ 0	$ 0	0
Exelon Generation Co L L C [Member] | Foreign Exchange Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge			(2,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net			0
Unrealized Gain (Loss) on Derivatives			$ (2,000,000)

Derivative Financial Instrum116

Derivative Financial Instruments - Summary of Proprietary Trading Activities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ (24,000,000)	$ 367,000,000	$ (716,000,000)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(41,000,000)	357,000,000	(693,000,000)
Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	1,000,000	(8,000,000)	(26,000,000)
Interest Expense [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts		100,000,000	(100,000,000)
Commodity Contract [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	213,000,000	404,000,000	(607,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(244,000,000)	(154,000,000)	8,000,000
Unrealized Gain (Loss) on Commodity Contracts	(31,000,000)	250,000,000	(599,000,000)
Commodity Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	23,000,000	8,000,000	(1,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(21,000,000)	(14,000,000)	(29,000,000)
Unrealized Gain (Loss) on Commodity Contracts	2,000,000	(6,000,000)	(30,000,000)
Commodity Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge		0	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		0	0
Unrealized Gain (Loss) on Commodity Contracts		0	0
Foreign Exchange Contract [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(2,000,000)	49,000,000	(92,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(8,000,000)	58,000,000	(2,000,000)
Unrealized Gain (Loss) on Derivatives	(10,000,000)	107,000,000	(94,000,000)
Foreign Exchange Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(1,000,000)	8,000,000	1,000,000
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	(10,000,000)	3,000,000
Unrealized Gain (Loss) on Derivatives	(1,000,000)	(2,000,000)	4,000,000
Foreign Exchange Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge		36,000,000	(100,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		64,000,000	0
Unrealized Gain (Loss) on Derivatives		100,000,000	(100,000,000)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(40,000,000)	249,000,000	(635,000,000)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(41,000,000)	257,000,000	(593,000,000)
Exelon Generation Co L L C [Member] | Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(500,000,000)	203,000,000	(174,000,000)
Exelon Generation Co L L C [Member] | Purchased Power And Fuel [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	459,000,000	54,000,000	(417,000,000)
Exelon Generation Co L L C [Member] | Interest Expense [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts			(2,000,000)
Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	213,000,000	404,000,000	(607,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(244,000,000)	(154,000,000)	8,000,000
Unrealized Gain (Loss) on Commodity Contracts	(31,000,000)	250,000,000	(599,000,000)
Exelon Generation Co L L C [Member] | Commodity Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	5,000,000	759,000,000	(413,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(495,000,000)	(563,000,000)	231,000,000
Unrealized Gain (Loss) on Commodity Contracts	(490,000,000)	196,000,000	(182,000,000)
Exelon Generation Co L L C [Member] | Commodity Contract [Member] | Purchased Power And Fuel [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	208,000,000	(355,000,000)	(194,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	251,000,000	409,000,000	(223,000,000)
Unrealized Gain (Loss) on Commodity Contracts	459,000,000	54,000,000	(417,000,000)
Exelon Generation Co L L C [Member] | Commodity Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge			0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net			0
Unrealized Gain (Loss) on Commodity Contracts			0
Exelon Generation Co L L C [Member] | Foreign Exchange Contract [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(2,000,000)	13,000,000	8,000,000
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(8,000,000)	(6,000,000)	(2,000,000)
Unrealized Gain (Loss) on Derivatives	(10,000,000)	7,000,000	6,000,000
Exelon Generation Co L L C [Member] | Foreign Exchange Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(2,000,000)	13,000,000	10,000,000
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(8,000,000)	(6,000,000)	(2,000,000)
Unrealized Gain (Loss) on Derivatives	(10,000,000)	7,000,000	8,000,000
Exelon Generation Co L L C [Member] | Foreign Exchange Contract [Member] | Purchased Power And Fuel [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	0	0	0
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0
Unrealized Gain (Loss) on Derivatives	$ 0	$ 0	0
Exelon Generation Co L L C [Member] | Foreign Exchange Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge			(2,000,000)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net			0
Unrealized Gain (Loss) on Derivatives			$ (2,000,000)

Derivative Financial Instrum117

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) - Exelon Generation Co L L C [Member] $ in Millions	Dec. 31, 2016USD ($)
Total Exposure Before Credit Collateral [Member]
Derivative [Line Items]
Investment grade	$ 995
Non-investment grade	118
Internally rated — investment grade	352
Internally rated — non-investment grade	72
Total	1,537
Credit Collateral [Member]
Derivative [Line Items]
Investment grade	0
Non-investment grade	16
Internally rated — investment grade	1
Internally rated — non-investment grade	8
Total	25
Net Exposure [Member]
Derivative [Line Items]
Investment grade	995
Non-investment grade	102
Internally rated — investment grade	351
Internally rated — non-investment grade	64
Total	1,512
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Investment grade	1
Non-investment grade	0
Internally rated — investment grade	0
Internally rated — non-investment grade	0
Total	1
Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Investment grade	328
Non-investment grade	0
Internally rated — investment grade	0
Internally rated — non-investment grade	0
Total	$ 328

Derivative Financial Instrum118

Derivative Financial Instruments - Net Credit Exposure by Type of Counterparty (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Cash collateral held	$ 9
Letters of credit held	16
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Cash collateral held	24	$ 21
Letters of credit held	28	$ 78
Exelon Generation Co L L C [Member] | Net Exposure [Member]
Derivative [Line Items]
Financial institutions	116
Investor-owned utilities, marketers, power producers	689
Energy cooperatives and municipalities	636
Other	71
Total	$ 1,512

Derivative Financial Instrum119

Derivative Financial Instruments - Summary of Credit Risk Related Contingent Features (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Liability	[1]	$ (960)	$ (932)
Offsetting Fair Value of In-the-Money Contracts Under Master Netting Arrangements	[2]	627	684
Derivative liabilities, fair value	[3]	$ (333)	$ (248)
[1]	(a)Amount represents the gross fair value of out-of-the-money derivative contracts containing credit-risk-related contingent features ignoring the effects of master netting agreements.
[2]	(b)Amount represents the offsetting fair value of in-the-money derivative contracts under legally enforceable master netting agreements with the same counterparty, which reduces the amount of any liability for which a Registrant could potentially be required to post collateral.
[3]	(c)Amount represents the net fair value of out-of-the-money derivative contracts containing credit-risk related contingent features after considering the mitigating effects of offsetting positions under master netting arrangements and reflects the actual net liability upon which any potential contingent collateral obligations would be based.

Debt and Credit Agreements - Co

Debt and Credit Agreements - Commercial Paper Borrowings Outstanding (Details) - USD ($)		Dec. 31, 2016	Sep. 30, 2016	May 26, 2016		Dec. 31, 2015	Dec. 31, 2014	Aug. 10, 2013	Aug. 01, 2011
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount	[1]	$ 1,510,000,000
Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	9,450,000,000				$ 10,375,000,000
Outstanding commercial paper		$ 688,000,000				$ 1,162,000,000
Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size				$ 600,000,000	[4]			$ 500,000,000
Exelon Corporate [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		1.12%				0.88%	0.53%
Letters of Credit Outstanding, Amount	[1]	$ 29,000,000
Exelon Corporate [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]					$ 500,000,000
Outstanding commercial paper		$ 0				0
Average Interest Rate on Commercial Paper Borrowings		0.70%
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		1.14%
Letters of Credit Outstanding, Amount		$ 1,170,000,000
Line of Credit Facility, Current Borrowing Capacity		50,000,000
Exelon Generation Co L L C [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	5,300,000,000				5,450,000,000
Outstanding commercial paper		$ 620,000,000				$ 0
Average Interest Rate on Commercial Paper Borrowings		0.94%				0.49%
Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		$ 500,000,000				$ 275,000,000
Exelon Generation Co L L C [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		7,000,000
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings						0.89%	0.50%
Letters of Credit Outstanding, Amount	[1]	2,000,000
Line of Credit Facility, Current Borrowing Capacity		34,000,000
Commonwealth Edison Co [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]					$ 1,000,000,000
Outstanding commercial paper		$ 0				$ 294,000,000
Average Interest Rate on Commercial Paper Borrowings		0.77%				0.53%
Commonwealth Edison Co [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		$ 12,000,000
PECO Energy Co [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount	[1]	2,000,000
Line of Credit Facility, Current Borrowing Capacity		34,000,000
PECO Energy Co [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]					$ 600,000,000
Outstanding commercial paper		0				$ 0
PECO Energy Co [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		$ 21,000,000
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		0.95%				0.87%	0.61%
Letters of Credit Outstanding, Amount	[1]	$ 0
Line of Credit Facility, Current Borrowing Capacity		5,000,000
Baltimore Gas and Electric Company [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	600,000,000				$ 600,000,000
Outstanding commercial paper		$ 45,000,000				$ 210,000,000
Average Interest Rate on Commercial Paper Borrowings		0.77%				0.48%
Baltimore Gas and Electric Company [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Letters of Credit Outstanding, Amount		$ 2,000,000
Pepco Energy Services [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Current Borrowing Capacity		2,000,000
Pepco Holdings LLC [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings						1.22%	0.78%
Pepco Holdings LLC [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	0				$ 875,000,000
Outstanding commercial paper		$ 0				$ 484,000,000
Average Interest Rate on Commercial Paper Borrowings		1.03%				0.80%
Pepco Holdings LLC [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size				$ 900,000,000					$ 1,500,000,000
Line of Credit Facility, Current Borrowing Capacity			$ 900,000,000
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings		0.90%				0.68%	0.46%
Letters of Credit Outstanding, Amount	[1]	$ 0
Potomac Electric Power Company [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	500,000,000				$ 500,000,000
Outstanding commercial paper		$ 23,000,000				$ 64,000,000
Average Interest Rate on Commercial Paper Borrowings		0.71%				0.44%
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings						0.79%	0.42%
Letters of Credit Outstanding, Amount	[1]	$ 0
Line of Credit Facility, Current Borrowing Capacity		2,000,000
Delmarva Power and Light Company [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	500,000,000				$ 500,000,000
Outstanding commercial paper		$ 0				$ 105,000,000
Average Interest Rate on Commercial Paper Borrowings		0.68%				0.47%
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Average Interest Rate on Commercial Paper Borrowings						0.65%	0.52%
Letters of Credit Outstanding, Amount	[1]	$ 1,000,000
Line of Credit Facility, Current Borrowing Capacity		2,000,000
Atlantic City Electric Company [Member] | Commercial Paper [Member]
Short-term Debt [Line Items]
Maximum Program Size	[2],[3]	350,000,000				$ 350,000,000
Outstanding commercial paper		$ 0				$ 5,000,000
Average Interest Rate on Commercial Paper Borrowings		0.65%				0.46%
[1]	Excludes nonrecourse debt letters of credit, see discussion below on Continental Wind.
[2]	Excludes $500 million and $275 million in bilateral credit facilities that do not back Generation's commercial paper program at December 31, 2016 and 2015, respectively
[3]	Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million, $5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.
[4]	Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million ,$5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.

Debt and Credit Agreements - Su

Debt and Credit Agreements - Summary of Bank Commitments, Credit Facility Borrowings and Available Capacity (Details) - USD ($) $ in Millions		Dec. 31, 2016	Sep. 30, 2016	May 26, 2016		Apr. 01, 2016	Jan. 05, 2016	Dec. 31, 2015	Oct. 23, 2015	Aug. 10, 2013	Aug. 01, 2011
Short-term Debt [Line Items]
Facility draws		$ 75
Outstanding letters of credit	[1]	1,510
Actual available capacity		7,915
To Support Additional Commercial Paper	[2]	7,108
Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size				$ 600	[3]					$ 500
Exelon Corporate [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	29
Actual available capacity		571
To Support Additional Commercial Paper	[2]	571
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit		1,170
Actual available capacity		4,130
To Support Additional Commercial Paper		3,510
Credit facility agreements with minority and community banks		50
Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Outstanding letters of credit		500						$ 275
Exelon Generation Co L L C [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Outstanding letters of credit		7
Exelon Generation Co L L C [Member] | Line of Credit [Member]
Short-term Debt [Line Items]
Maximum Program Size						$ 200	$ 150		$ 100
Actual available capacity		119
To Support Additional Commercial Paper	[2]	0
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	2
Actual available capacity		998
To Support Additional Commercial Paper	[2]	998
Credit facility agreements with minority and community banks		34
Commonwealth Edison Co [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Outstanding letters of credit		12
PECO Energy Co [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	2
Actual available capacity		598
To Support Additional Commercial Paper	[2]	598
Credit facility agreements with minority and community banks		34
PECO Energy Co [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Outstanding letters of credit		21
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	0
Actual available capacity		600
To Support Additional Commercial Paper	[2]	555
Credit facility agreements with minority and community banks		5
Baltimore Gas and Electric Company [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Outstanding letters of credit		2
Pepco Holdings LLC [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size				$ 900							$ 1,500
Credit facility agreements with minority and community banks			$ 900
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	0
Actual available capacity		300
To Support Additional Commercial Paper	[2]	277
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	0
Actual available capacity		300
To Support Additional Commercial Paper	[2]	300
Credit facility agreements with minority and community banks		2
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	1
Actual available capacity		299
To Support Additional Commercial Paper	[2]	299
Credit facility agreements with minority and community banks		$ 2
[1]	Excludes nonrecourse debt letters of credit, see discussion below on Continental Wind.
[2]	Pepco, DPL and ACE's revolving credit facility is subject to available borrowing capacity. The borrowing capacity may be increased or decreased during the term of the facility, except that (i) the sum of the borrowing capacity must equal the total amount of the facility, and (ii) the aggregate amount of credit used at any given time by each of Pepco, DPL or ACE may not exceed $900 million or the maximum amount of short-term debt the company is permitted to have outstanding by its regulatory authorities. The total number of the borrowing reallocations may not exceed eight per year during the term of the facility.
[3]	Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million ,$5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.

Debt and Credit Agreements -122

Debt and Credit Agreements - Summary of Short-term Borrowing Activities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Exelon Corporate [Member]
Short-term Debt [Line Items]
Average borrowings	$ 1,125	$ 499	$ 571
Maximum borrowings outstanding	$ 3,076	$ 739	$ 1,164
Average interest rates, computed on a daily basis	0.88%	0.53%	0.32%
Average interest rates at year end	1.12%	0.88%	0.53%
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Average borrowings	$ 536	$ 1	$ 93
Maximum borrowings outstanding	$ 1,735	$ 50	$ 552
Average interest rates, computed on a daily basis	0.94%	0.49%	0.32%
Average interest rates at year end	1.14%
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Average borrowings	$ 256	$ 461	$ 415
Maximum borrowings outstanding	$ 755	$ 684	$ 597
Average interest rates, computed on a daily basis	0.77%	0.53%	0.33%
Average interest rates at year end		0.89%	0.50%
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Average borrowings	$ 143	$ 37	$ 64
Maximum borrowings outstanding	$ 369	$ 210	$ 180
Average interest rates, computed on a daily basis	0.77%	0.48%	0.29%
Average interest rates at year end	0.95%	0.87%	0.61%
Pepco Holdings LLC [Member]
Short-term Debt [Line Items]
Average borrowings	$ 153	$ 444	$ 153
Maximum borrowings outstanding	$ 559	$ 784	$ 369
Average interest rates, computed on a daily basis	1.03%	0.90%	0.56%
Average interest rates at year end		1.22%	0.78%
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Average borrowings	$ 4	$ 34	$ 37
Maximum borrowings outstanding	$ 73	$ 190	$ 209
Average interest rates, computed on a daily basis	0.71%	0.44%	0.28%
Average interest rates at year end	0.90%	0.68%	0.46%
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Average borrowings	$ 33	$ 81	$ 69
Maximum borrowings outstanding	$ 116	$ 179	$ 177
Average interest rates, computed on a daily basis	0.68%	0.47%	0.26%
Average interest rates at year end		0.79%	0.42%
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Average borrowings	$ 0	$ 175	$ 112
Maximum borrowings outstanding	$ 5	$ 253	$ 259
Average interest rates, computed on a daily basis	0.65%	0.46%	0.27%
Average interest rates at year end		0.65%	0.52%

Debt and Credit Agreements -123

Debt and Credit Agreements - Summary of Credit Facility Thresholds (Details)	12 Months Ended
	Dec. 31, 2016
Line of Credit Facility [Line Items]
Basis Points For Prime Based Borrowings	27.50%
Basis Points For Libor Based Borrowings	127.5
Credit agreement threshold	2.50
Exelon Generation Co L L C [Member]
Line of Credit Facility [Line Items]
Basis Points For Prime Based Borrowings	27.50%
Basis Points For Libor Based Borrowings	127.5
Credit agreement threshold	3
Commonwealth Edison Co [Member]
Line of Credit Facility [Line Items]
Basis Points For Prime Based Borrowings	7.50%
Basis Points For Libor Based Borrowings	107.5
Credit agreement threshold	2
PECO Energy Co [Member]
Line of Credit Facility [Line Items]
Basis Points For Prime Based Borrowings	0.00%
Basis Points For Libor Based Borrowings	90
Credit agreement threshold	2
Baltimore Gas and Electric Company [Member]
Line of Credit Facility [Line Items]
Basis Points For Prime Based Borrowings	0.00%
Basis Points For Libor Based Borrowings	100
Credit agreement threshold	2
Potomac Electric Power Company [Member]
Line of Credit Facility [Line Items]
Basis Points For Prime Based Borrowings	7.50%
Basis Points For Libor Based Borrowings	107.5
Credit agreement threshold	2
Delmarva Power and Light Company [Member]
Line of Credit Facility [Line Items]
Basis Points For Prime Based Borrowings	7.50%
Basis Points For Libor Based Borrowings	107.5
Credit agreement threshold	2
Atlantic City Electric Company [Member]
Line of Credit Facility [Line Items]
Basis Points For Prime Based Borrowings	7.50%
Basis Points For Libor Based Borrowings	107.5
Credit agreement threshold	2

Debt and Credit Agreements -124

Debt and Credit Agreements - Summary of Interest Coverage Ratios (Details)	12 Months Ended
	Dec. 31, 2016
Debt Instrument [Line Items]
Debt Instrument, Covenant Compliance	7.03
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Compliance	11.81
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Compliance	6.89
PECO Energy Co [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Compliance	8.77
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Compliance	10.47
Potomac Electric Power Company [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Compliance	6.24
Delmarva Power and Light Company [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Compliance	8.42
Atlantic City Electric Company [Member]
Debt Instrument [Line Items]
Debt Instrument, Covenant Compliance	5.84

Debt and Credit Agreements -125

Debt and Credit Agreements - Summary of Outstanding Long-term Debt (Details) - USD ($)		Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2015
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 33,311,000,000	$ 25,113,000,000
Unamortized debt discount and premium, net		(68,000,000)	(63,000,000)
Long-term debt (including amounts due within one year) (a)		962,000,000	275,000,000
Long-term debt due within one year		(2,430,000,000)	(1,500,000,000)
Long-term debt		31,575,000,000	23,645,000,000
Long-term debt to financing trusts		641,000,000	641,000,000
Total long-term debt to financing trusts		648,000,000	648,000,000
Unamortized Debt Issuance Expense	[1]	(200,000,000)	(180,000,000)
ComEd Financing Three Affiliate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		206,000,000	206,000,000
Long-term debt to financing trusts		$ 205,000,000	205,000,000
ComEd Financing Three Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.35%
Interest rate on long-term debt		6.35%
PECO Trust Three Affiliate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 81,000,000	81,000,000
Long-term debt to financing trusts		$ 81,000,000	81,000,000
PECO Trust Three Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.38%
Interest rate on long-term debt		7.38%
PECO Trust Four Affiliate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 103,000,000	103,000,000
Long-term debt to financing trusts		$ 103,000,000	103,000,000
PECO Trust Four Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.75%
Interest rate on long-term debt		5.75%
BGE Trust Member [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 258,000,000	258,000,000
BGE Trust Member [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.20%
Interest rate on long-term debt		6.20%
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 2,300,000,000	1,750,000,000
Unsecured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.40%
Interest rate on long-term debt		2.40%
Unsecured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.35%
Interest rate on long-term debt		6.35%
Rate Stabilization Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 41,000,000	120,000,000
Rate Stabilization Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.82%
Interest rate on long-term debt		5.82%
Rate Stabilization Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.82%
Interest rate on long-term debt		5.82%
Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[2]	$ 14,123,000,000	9,019,000,000
Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[2]	1.70%
Interest rate on long-term debt	[2]	1.70%
Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[2]	7.90%
Interest rate on long-term debt	[2]	7.90%
Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 11,868,000,000	9,803,000,000
Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.55%
Interest rate on long-term debt		1.55%
Senior Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.60%
Interest rate on long-term debt		7.60%
Pollution Control Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 435,000,000	435,000,000
Pollution Control Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.70%
Interest rate on long-term debt		2.70%
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 105,000,000	127,000,000
Notes Payable to Banks [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.15%
Interest rate on long-term debt		3.15%
Notes Payable to Banks [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.35%
Interest rate on long-term debt		3.35%
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[3],[4]	$ 576,000,000	314,000,000
Unamortized Debt Issuance Expense	[1]	$ (7,000,000)	(7,000,000)
Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3]	1.43%
Interest rate on long-term debt	[3]	1.43%
Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[3]	7.83%
Interest rate on long-term debt	[3]	7.83%
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 1,150,000,000	1,150,000,000	$ 1,150,000,000
Junior Subordinated Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.50%
Interest rate on long-term debt		6.50%
contract Payments Junior Subordinate Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 19,000,000	64,000,000
contract Payments Junior Subordinate Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.50%
Interest rate on long-term debt		2.50%
Software License Arrangement [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 103,000,000	111,000,000
Software License Arrangement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.95%
Interest rate on long-term debt		3.95%
Tax-exempt Money Market Funds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 112,000,000	0
Tax-exempt Money Market Funds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.40%
Interest rate on long-term debt		5.40%
Medium-term Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 40,000,000	0
Medium-term Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.81%
Interest rate on long-term debt		6.81%
Medium-term Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.72%
Interest rate on long-term debt		7.72%
Transition Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 124,000,000	0
Transition Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.05%
Interest rate on long-term debt		5.05%
Transition Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.55%
Interest rate on long-term debt		5.55%
Non Recourse Fixed Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 1,400,000,000	1,162,000,000
Non Recourse Variable Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		915,000,000	1,058,000,000
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations, noncurrent		69,000,000	29,000,000
Due in 2015		17,000,000
Due in 2016		18,000,000
Due in 2017		20,000,000
Due in 2018		5,000,000
Due in 2019		1,000,000
Due in 2020		8,000,000
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		9,208,000,000	8,919,000,000
Unamortized debt discount and premium, net		(17,000,000)	(17,000,000)
Long-term debt (including amounts due within one year) (a)		115,000,000	127,000,000
Long-term debt due within one year		(1,117,000,000)	(90,000,000)
Long-term debt		7,202,000,000	7,936,000,000
Long-term debt to financing trusts		922,000,000	933,000,000
Debt and Capital Lease Obligations		8,124,000,000	8,869,000,000
Unamortized Debt Issuance Expense		(65,000,000)	(70,000,000)
Capital lease obligations, noncurrent		22,000,000	21,000,000
Due in 2016		5,000,000
Due in 2017		6,000,000
Due in 2018		5,000,000
Exelon Generation Co L L C [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 5,971,000,000	5,971,000,000
Exelon Generation Co L L C [Member] | Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.00%
Interest rate on long-term debt		2.00%
Exelon Generation Co L L C [Member] | Senior Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.60%
Interest rate on long-term debt		7.60%
Exelon Generation Co L L C [Member] | Pollution Control Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 435,000,000	435,000,000
Exelon Generation Co L L C [Member] | Pollution Control Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.50%
Interest rate on long-term debt		2.50%
Exelon Generation Co L L C [Member] | Pollution Control Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.70%
Interest rate on long-term debt		2.70%
Exelon Generation Co L L C [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 105,000,000	127,000,000
Exelon Generation Co L L C [Member] | Notes Payable to Banks [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.20%
Interest rate on long-term debt		3.20%
Exelon Generation Co L L C [Member] | Notes Payable to Banks [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.40%
Interest rate on long-term debt		3.40%
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[5],[6]	$ 382,000,000	166,000,000
Long-term debt		$ 198,000,000
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.40%
Interest rate on long-term debt		1.40%
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.80%
Interest rate on long-term debt		7.80%
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 1,400,000,000	1,162,000,000
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.30%
Interest rate on long-term debt		2.30%
Exelon Generation Co L L C [Member] | Non Recourse Fixed Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.00%
Interest rate on long-term debt		6.00%
Exelon Generation Co L L C [Member] | Non Recourse Variable Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 915,000,000	1,058,000,000
Exelon Generation Co L L C [Member] | Non Recourse Variable Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.20%
Interest rate on long-term debt		3.20%
Exelon Generation Co L L C [Member] | Non Recourse Variable Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.00%
Interest rate on long-term debt		5.00%
Potomac Electric Power Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 2,381,000,000	2,385,000,000
Unamortized debt discount and premium, net		(2,000,000)	(3,000,000)
Long-term debt		2,333,000,000	2,340,000,000
Long-term debt due within one year		(16,000,000)	(11,000,000)
Long-term debt		2,333,000,000	2,340,000,000
Unamortized Debt Issuance Expense	[7]	(30,000,000)	(31,000,000)
Potomac Electric Power Company [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 2,335,000,000	2,335,000,000
Potomac Electric Power Company [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.05%
Interest rate on long-term debt		3.05%
Potomac Electric Power Company [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.90%
Interest rate on long-term debt		7.90%
Potomac Electric Power Company [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 46,000,000	50,000,000
Potomac Electric Power Company [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.20%
Interest rate on long-term debt		6.20%
Potomac Electric Power Company [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		8.88%
Interest rate on long-term debt		8.88%
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 7,101,000,000	6,567,000,000
Unamortized debt discount and premium, net		(22,000,000)	(20,000,000)
Long-term debt due within one year		(425,000,000)	(665,000,000)
Long-term debt		6,608,000,000	5,844,000,000
Long-term debt to financing trusts		205,000,000	205,000,000
Total long-term debt to financing trusts		206,000,000	206,000,000
Debt and Capital Lease Obligations		6,608,000,000	5,844,000,000
Unamortized Debt Issuance Expense	[8]	(46,000,000)	(38,000,000)
Commonwealth Edison Co [Member] | ComEd Financing Three Affiliate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		206,000,000	206,000,000
Long-term debt to financing trusts		205,000,000	205,000,000
Unamortized Debt Issuance Expense	[8]	$ (1,000,000)	(1,000,000)
Commonwealth Edison Co [Member] | ComEd Financing Three Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.35%
Interest rate on long-term debt		6.35%
Commonwealth Edison Co [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[9]	$ 6,954,000,000	6,419,000,000
Commonwealth Edison Co [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[9]	2.15%
Interest rate on long-term debt	[9]	2.15%
Commonwealth Edison Co [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[9]	6.45%
Interest rate on long-term debt	[9]	6.45%
Commonwealth Edison Co [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[10]	$ 147,000,000	148,000,000
Commonwealth Edison Co [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[10]	6.95%
Interest rate on long-term debt	[10]	6.95%
Commonwealth Edison Co [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[10]	7.49%
Interest rate on long-term debt	[10]	7.49%
Commonwealth Edison Co [Member] | Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Capital lease obligations, noncurrent		$ 8,000,000
Due in 2020		1,000,000
PECO Energy Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		2,600,000,000	2,600,000,000
Unamortized debt discount and premium, net		(5,000,000)	(5,000,000)
Long-term debt		2,580,000,000	2,280,000,000
Long-term debt to financing trusts		184,000,000	184,000,000
Long-term debt due within one year		0	(300,000,000)
Debt and Capital Lease Obligations		2,580,000,000	2,280,000,000
Unamortized Debt Issuance Expense	[7]	(15,000,000)	(15,000,000)
PECO Energy Co [Member] | PECO Trust Three Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts		$ 81,000,000	81,000,000
PECO Energy Co [Member] | PECO Trust Three Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.38%
Interest rate on long-term debt		7.38%
PECO Energy Co [Member] | PECO Trust Four Affiliate [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts		$ 103,000,000	103,000,000
PECO Energy Co [Member] | PECO Trust Four Affiliate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.75%
Interest rate on long-term debt		5.75%
PECO Energy Co [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[11]	$ 2,600,000,000	2,600,000,000
PECO Energy Co [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[11]	1.70%
Interest rate on long-term debt	[11]	1.70%
PECO Energy Co [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[11]	5.95%
Interest rate on long-term debt	[11]	5.95%
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 2,341,000,000	1,870,000,000
Unamortized debt discount and premium, net		(4,000,000)	(3,000,000)
Long-term debt		2,281,000,000	1,480,000,000
Long-term debt to financing trusts		252,000,000	252,000,000
Total long-term debt to financing trusts		258,000,000	258,000,000
Long-term debt due within one year		(41,000,000)	(378,000,000)
Long-term debt		2,281,000,000	1,480,000,000
Unamortized Debt Issuance Expense	[12]	(15,000,000)	(9,000,000)
Baltimore Gas and Electric Company [Member] | BGE Trust Member [Member]
Debt Instrument [Line Items]
Long-term debt to financing trusts			252,000,000
Total long-term debt to financing trusts		258,000,000	258,000,000
Unamortized Debt Issuance Expense	[12]	$ (6,000,000)	(6,000,000)
Baltimore Gas and Electric Company [Member] | BGE Trust Member [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.20%
Interest rate on long-term debt		6.20%
Baltimore Gas and Electric Company [Member] | Rate Stabilization Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 41,000,000	120,000,000
Baltimore Gas and Electric Company [Member] | Rate Stabilization Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.82%
Interest rate on long-term debt		5.82%
Baltimore Gas and Electric Company [Member] | Rate Stabilization Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.82%
Interest rate on long-term debt		5.82%
Baltimore Gas and Electric Company [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 2,300,000,000	1,750,000,000
Baltimore Gas and Electric Company [Member] | Senior Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.40%
Interest rate on long-term debt		2.40%
Baltimore Gas and Electric Company [Member] | Senior Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.35%
Interest rate on long-term debt		6.35%
Pepco Holdings LLC [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 5,157,000,000	5,331,000,000
Unamortized debt discount and premium, net		1,000,000	(2,000,000)
Long-term debt (including amounts due within one year) (a)		742,000,000	0
Long-term debt due within one year		(253,000,000)	(456,000,000)
Long-term debt		5,645,000,000	4,823,000,000
Unamortized Debt Issuance Expense	[7]	(2,000,000)	(50,000,000)
Pepco Holdings LLC [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 266,000,000	456,000,000
Pepco Holdings LLC [Member] | Unsecured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.13%
Interest rate on long-term debt		6.13%
Pepco Holdings LLC [Member] | Unsecured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.45%
Interest rate on long-term debt		7.45%
Pepco Holdings LLC [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 4,569,000,000	4,495,000,000
Pepco Holdings LLC [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.05%
Interest rate on long-term debt		3.05%
Pepco Holdings LLC [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.90%
Interest rate on long-term debt		7.90%
Pepco Holdings LLC [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 46,000,000	57,000,000
Pepco Holdings LLC [Member] | Notes Payable, Other Payables [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.20%
Interest rate on long-term debt		6.20%
Pepco Holdings LLC [Member] | Notes Payable, Other Payables [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		8.88%
Interest rate on long-term debt		8.88%
Pepco Holdings LLC [Member] | Tax-exempt Money Market Funds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 112,000,000	112,000,000
Pepco Holdings LLC [Member] | Tax-exempt Money Market Funds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.40%
Interest rate on long-term debt		5.40%
Pepco Holdings LLC [Member] | Medium-term Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 40,000,000	40,000,000
Pepco Holdings LLC [Member] | Medium-term Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.81%
Interest rate on long-term debt		6.81%
Pepco Holdings LLC [Member] | Medium-term Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.72%
Interest rate on long-term debt		7.72%
Pepco Holdings LLC [Member] | Transition Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[13]	$ 124,000,000	171,000,000
Pepco Holdings LLC [Member] | Transition Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.05%
Interest rate on long-term debt		5.05%
Pepco Holdings LLC [Member] | Transition Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.55%
Interest rate on long-term debt		5.55%
Delmarva Power and Light Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 1,348,000,000	1,273,000,000
Unamortized debt discount and premium, net		2,000,000	2,000,000
Long-term debt due within one year		(105,000,000)
Long-term debt		1,221,000,000	1,061,000,000
Long-term debt due within one year		(119,000,000)	(204,000,000)
Long-term debt		1,221,000,000	1,061,000,000
Unamortized Debt Issuance Expense	[7]	(10,000,000)	(10,000,000)
Delmarva Power and Light Company [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 1,196,000,000	1,121,000,000
Delmarva Power and Light Company [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.50%
Interest rate on long-term debt		3.50%
Delmarva Power and Light Company [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		4.15%
Interest rate on long-term debt		4.15%
Delmarva Power and Light Company [Member] | Tax-exempt Money Market Funds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 112,000,000	112,000,000
Delmarva Power and Light Company [Member] | Tax-exempt Money Market Funds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.40%
Interest rate on long-term debt		5.40%
Delmarva Power and Light Company [Member] | Medium-term Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 40,000,000	40,000,000
Delmarva Power and Light Company [Member] | Medium-term Notes [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.81%
Interest rate on long-term debt		6.81%
Delmarva Power and Light Company [Member] | Medium-term Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.72%
Interest rate on long-term debt		7.72%
Atlantic City Electric Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 1,162,000,000	1,210,000,000
Unamortized debt discount and premium, net		(1,000,000)	(1,000,000)
Long-term debt		1,120,000,000	1,153,000,000
Long-term debt due within one year		(35,000,000)	(48,000,000)
Long-term debt		1,120,000,000	1,153,000,000
Unamortized Debt Issuance Expense	[7]	(6,000,000)	(8,000,000)
Atlantic City Electric Company [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 1,038,000,000	1,039,000,000
Atlantic City Electric Company [Member] | Secured Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		3.38%
Interest rate on long-term debt		3.38%
Atlantic City Electric Company [Member] | Secured Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.75%
Interest rate on long-term debt		7.75%
Atlantic City Electric Company [Member] | Transition Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[14]	$ 124,000,000	$ 171,000,000
Atlantic City Electric Company [Member] | Transition Bonds [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.05%
Interest rate on long-term debt		5.05%
Atlantic City Electric Company [Member] | Transition Bonds [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		5.55%
Interest rate on long-term debt		5.55%
[1]	Amounts owed to these financing trusts are recorded as Long-term debt to financing trusts within Exelon’s Consolidated Balance Sheets.
[2]	Substantially all of ComEd’s assets other than expressly excepted property and substantially all of PECO’s, Pepco's, DPL's and ACE's assets are subject to the liens of their respective mortgage indentures.
[3]	Includes capital lease obligations of $69 million and $29 million at December 31, 2016 and 2015, respectively. Lease payments of $17 million, $18 million, $20 million, $5 million, $1 million, and $8 million will be made in 2017, 2018, 2019, 2020, 2021 and thereafter, respectively.
[4]	Includes financing related to Albany Green Energy, LLC (AGE), which is a consolidated variable interest entity (see Note 2 - Variable Interest Entities for additional information). The agreement is scheduled to expire on November 17, 2017, at a variable rate equal to LIBOR plus 1.25%. As of December 31, 2016, $198 million was outstanding.
[5]	Includes Generation’s capital lease obligations of $22 million and $21 million at December 31, 2016 and 2015, respectively. Generation will make lease payments of $5 million, $5 million, $6 million and $5 million and $1 million in 2017, 2018, 2019, 2020 and 2021 respectively. The capital lease matures in 2020.
[6]	Includes financing related to Albany Green Energy, LLC (AGE), which is a consolidated variable interest entity (see Note 2 - Variable Interest Entities for additional information). The agreement is scheduled to expire on November 17, 2017, at a variable rate equal to LIBOR plus 1.25%. As of December 31, 2016, $198 million was outstanding.
[7]	Amounts owed to this financing trust are recorded as Long-term debt to financing trusts within PECO’s Consolidated Balance Sheets.
[8]	Amount owed to this financing trust is recorded as Long-term debt to financing trust within ComEd’s Consolidated Balance Sheets.
[9]	Substantially all of ComEd’s assets other than expressly excepted property are subject to the lien of its mortgage indenture.
[10]	Includes ComEd’s capital lease obligations of $8 million at both December 31, 2016 and 2015, respectively. Lease payments of less than $1 million will be made from 2017 through expiration at 2053.
[11]	Substantially all of PECO’s assets are subject to the lien of its mortgage indenture
[12]	Amount owed to this financing trust is recorded as Long-term debt to financing trust within BGE’s Consolidated Balance Sheets.
[13]	Transition bonds are recorded as part of Long-term debt within ACE's Consolidated Balance Sheets.
[14]	Substantially all of ACE's assets are subject to the lien of its respective mortgage indenture.

Debt and Credit Agreements - Sc

Debt and Credit Agreements - Schedule of Long-term Debt Maturities (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
2,017		$ 2,430
2,018		1,742
2,019		1,060
2,020		3,331
2,021		2,400
Thereafter	[1]	22,996
Total		33,959
Total long-term debt to financing trusts		648	$ 648
Long-term Debt, Gross		33,311	25,113
BGE Trust Member [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		258	258
ComEd Financing Three Affiliate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		206	206
PECO Financing Trusts [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		184
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
2,017		1,117
2,018		104
2,019		606
2,020		1,912
2,021		888
Thereafter		4,581
Total		9,208
Long-term Debt, Gross		9,208	8,919
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
2,017		425
2,018		840
2,019		300
2,020		500
2,021		350
Thereafter	[2]	4,892
Total		7,307
Total long-term debt to financing trusts		206	206
Long-term Debt, Gross		7,101	6,567
Commonwealth Edison Co [Member] | ComEd Financing Three Affiliate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		206	206
PECO Energy Co [Member]
Debt Instrument [Line Items]
2,017		0
2,018		500
2,019		0
2,020		0
2,021		300
Thereafter	[3]	1,984
Total		2,784
Long-term Debt, Gross		2,600	2,600
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
2,017		41
2,018		0
2,019		0
2,020		0
2,021		300
Thereafter	[4]	2,258
Total		2,599
Total long-term debt to financing trusts		258	258
Long-term Debt, Gross		2,341	1,870
Baltimore Gas and Electric Company [Member] | BGE Trust Member [Member]
Debt Instrument [Line Items]
Total long-term debt to financing trusts		258	258
Pepco Holdings LLC [Member]
Debt Instrument [Line Items]
2,017		253
2,018		298
2,019		154
2,020		19
2,021		262
Thereafter		4,171
Total		5,157
Long-term Debt, Gross		5,157	5,331
Potomac Electric Power Company [Member]
Debt Instrument [Line Items]
2,017		16
2,018		13
2,019		124
2,020		0
2,021		2
Thereafter		2,226
Total		2,381
Long-term Debt, Gross		2,381	2,385
Delmarva Power and Light Company [Member]
Debt Instrument [Line Items]
2,017		119
2,018		4
2,019		12
2,020		0
2,021		0
Thereafter		1,213
Total		1,348
Long-term Debt, Gross		1,348	1,273
Atlantic City Electric Company [Member]
Debt Instrument [Line Items]
2,017		35
2,018		281
2,019		18
2,020		19
2,021		260
Thereafter		549
Total		1,162
Long-term Debt, Gross		1,162	1,210
Medium-term Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		40	0
Medium-term Notes [Member] | Pepco Holdings LLC [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		40	40
Medium-term Notes [Member] | Delmarva Power and Light Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		40	40
Unsecured Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		2,300	1,750
Unsecured Debt [Member] | Pepco Holdings LLC [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		266	456
Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		11,868	9,803
Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		5,971	5,971
Senior Notes [Member] | Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		2,300	1,750
Transition Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		124	0
Transition Bonds [Member] | Pepco Holdings LLC [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[5]	124	171
Transition Bonds [Member] | Atlantic City Electric Company [Member]
Debt Instrument [Line Items]
2,017		35
2,018		31
2,019		18
2,020		19
2,021		21
Long-term Debt, Gross	[6]	124	171
Rate Stabilization Bonds [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		41	120
Rate Stabilization Bonds [Member] | Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		41	120
Pollution Control Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		435	435
Pollution Control Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		435	435
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		105	127
Notes Payable to Banks [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		105	127
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[7],[8]	576	314
Notes Payable, Other Payables [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[9],[10]	382	166
Notes Payable, Other Payables [Member] | Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	[11]	147	148
Notes Payable, Other Payables [Member] | Pepco Holdings LLC [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		46	57
Notes Payable, Other Payables [Member] | Potomac Electric Power Company [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		46	50
Non Recourse Fixed Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		1,400	1,162
Non Recourse Fixed Rate [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		1,400	1,162
Non Recourse Variable Rate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		915	1,058
Non Recourse Variable Rate [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 915	$ 1,058
[1]	Includes $648 million due to ComEd, PECO and BGE financing trusts.
[2]	Includes $206 million due to ComEd financing trust.
[3]	Includes $184 million due to PECO financing trusts.
[4]	Includes $258 million due to BGE financing trust.
[5]	Transition bonds are recorded as part of Long-term debt within ACE's Consolidated Balance Sheets.
[6]	Substantially all of ACE's assets are subject to the lien of its respective mortgage indenture.
[7]	Includes capital lease obligations of $69 million and $29 million at December 31, 2016 and 2015, respectively. Lease payments of $17 million, $18 million, $20 million, $5 million, $1 million, and $8 million will be made in 2017, 2018, 2019, 2020, 2021 and thereafter, respectively.
[8]	Includes financing related to Albany Green Energy, LLC (AGE), which is a consolidated variable interest entity (see Note 2 - Variable Interest Entities for additional information). The agreement is scheduled to expire on November 17, 2017, at a variable rate equal to LIBOR plus 1.25%. As of December 31, 2016, $198 million was outstanding.
[9]	Includes Generation’s capital lease obligations of $22 million and $21 million at December 31, 2016 and 2015, respectively. Generation will make lease payments of $5 million, $5 million, $6 million and $5 million and $1 million in 2017, 2018, 2019, 2020 and 2021 respectively. The capital lease matures in 2020.
[10]	Includes financing related to Albany Green Energy, LLC (AGE), which is a consolidated variable interest entity (see Note 2 - Variable Interest Entities for additional information). The agreement is scheduled to expire on November 17, 2017, at a variable rate equal to LIBOR plus 1.25%. As of December 31, 2016, $198 million was outstanding.
[11]	Includes ComEd’s capital lease obligations of $8 million at both December 31, 2016 and 2015, respectively. Lease payments of less than $1 million will be made from 2017 through expiration at 2053.

Debt and Credit Agreements - Na

Debt and Credit Agreements - Narrative (Details) $ / shares in Units, shares in Millions

Feb. 29, 2016USD ($)

Dec. 02, 2015USD ($)

Sep. 30, 2013MW

Jun. 30, 2014USD ($)shares

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Dec. 31, 2014USD ($)

Jun. 30, 2016USD ($)

May 26, 2016USD ($)

Apr. 01, 2016USD ($)

Mar. 31, 2016USD ($)

Jan. 13, 2016USD ($)

Jan. 05, 2016USD ($)

Oct. 23, 2015USD ($)

Sep. 30, 2015USD ($)

Jul. 30, 2015

Jun. 30, 2015USD ($)$ / shares

Sep. 30, 2014USD ($)

Sep. 18, 2014USD ($)

May 31, 2014USD ($)

Feb. 06, 2014USD ($)

Aug. 10, 2013USD ($)

Dec. 31, 2012USD ($)

Jun. 30, 2012USD ($)

Oct. 31, 2011USD ($)

Aug. 01, 2011USD ($)

Jul. 31, 2011USD ($)

Debt Instrument [Line Items]

Long-term Debt, Current Maturities

$ 2,430,000,000

$ 1,500,000,000

Repayments of Long-term Debt

1,936,000,000

2,687,000,000

$ 1,545,000,000

Escrow Deposit

6,000,000

Gain (Loss) on Sale of Debt Investments

$ 37,000,000

Credit agreement threshold

2.50

Outstanding letters of credit

[1]

$ 1,510,000,000

Basis points adders for prime-based borrowings

27.50%

Basis points adders for LIBOR-based borrowings

127.5

Bridge loan

$ 3,200,000,000

$ 7,200,000,000

Long-term debt, gross

$ 33,311,000,000

25,113,000,000

Long-term debt

33,959,000,000

Redemption of debt

45,000,000

44,000,000

Collateral amount of debt

2,800,000,000

Line of Credit Facility, Increase (Decrease), Other, Net

$ 45,000,000

Secured Demand Note Deficiency

$ 23,000,000

Outstanding borrowings/facility draws

75,000,000

Debt Instrument, Fee Amount

$ 5,000,000

Payments of Debt Issuance Costs

4,000,000

Write off of Deferred Debt Issuance Cost

9,000,000

Redemption Premium

9,000,000

Designated as Hedging Instrument [Member]

Debt Instrument [Line Items]

Notional amount of preissuance interest rate cash flow hedge derivatives

659,000,000

Upstream Gas Property [Member]

Debt Instrument [Line Items]

Repayments of Long-term Debt

15,000,000

Senior Notes [Member]

Debt Instrument [Line Items]

Long-term debt, gross

11,868,000,000

9,803,000,000

Debt Instrument, Face Amount

$ 4,200,000,000

Redemption of debt

868,000,000

Junior Subordinated Debt [Member]

Debt Instrument [Line Items]

Long-term debt, gross

$ 1,150,000,000

1,150,000,000

$ 1,150,000,000

Equity units issued | shares

23

Conversion price | $ / shares

$ 50

Proceeds from issuance of subordinated long-term debt

$ 1,110,000,000

Underwriting fee

$ 35,000,000

Long-term debt

$ 131,000,000

Maximum [Member]

Debt Instrument [Line Items]

Basis points adders for prime-based borrowings

9000.00%

Basis points adders for LIBOR-based borrowings

165

Maximum [Member] | Senior Notes [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

7.60%

Maximum [Member] | Junior Subordinated Debt [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

6.50%

Minimum [Member] | Senior Notes [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

1.55%

Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

[2]

$ 9,500,000,000

Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 600,000,000

[2]

$ 500,000,000

Line of Credit Facility, Maximum Amount Outstanding During Period

$ 250,000,000

Credit agreement threshold

500

Exelon Corporate [Member]

Debt Instrument [Line Items]

Repayments of Long-term Debt

$ 46,000,000

2,263,000,000

23,000,000

Outstanding letters of credit

[1]

29,000,000

Long-term debt, gross

7,608,000,000

5,853,000,000

Long-term debt

7,608,000,000

Debt Instrument, Face Amount

$ 1,900,000,000

Outstanding borrowings/facility draws

0

Exelon Corporate [Member] | Junior Subordinated Debt [Member]

Debt Instrument [Line Items]

Long-term debt, gross

$ 1,150,000,000

1,150,000,000

Interest rate on long-term debt

6.50%

Exelon Corporate [Member] | Maximum [Member] | Senior Notes [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

[3]

7.60%

Exelon Corporate [Member] | Minimum [Member] | Senior Notes [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

[3]

1.60%

Exelon Corporate [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

[4],[5]

$ 600,000,000

Exelon Generation Co L L C [Member]

Debt Instrument [Line Items]

Long-term Debt, Current Maturities

1,117,000,000

90,000,000

Repayments of Long-term Debt

$ 202,000,000

89,000,000

586,000,000

Credit agreement threshold

3

Outstanding letters of credit

$ 1,170,000,000

Basis points adders for prime-based borrowings

27.50%

Basis points adders for LIBOR-based borrowings

127.5

Long-term debt, gross

$ 9,208,000,000

8,919,000,000

Long-term debt

9,208,000,000

Outstanding borrowings/facility draws

$ 0

Line of Credit Facility, Description

100

Exelon Generation Co L L C [Member] | ExGen Texas Power [Member] | Interest Rate Swap [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

2.34%

Non-recourse debt, interest rate swap

$ 505,000,000

Exelon Generation Co L L C [Member] | ExgenRenewablesI425June62021[Member] | Interest Rate Swap [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

2.03%

Non-recourse debt, interest rate swap

$ 240,000,000

Exelon Generation Co L L C [Member] | Senior Notes [Member]

Debt Instrument [Line Items]

Long-term debt, gross

$ 5,971,000,000

5,971,000,000

Debt Instrument, Face Amount

750,000,000

Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | ExGen Texas Power [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

4.75%

Debt Instrument, Face Amount

$ 675,000,000

Non-recourse debt

660,000,000

Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | ExgenRenewablesI425June62021[Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

4.25%

Long-term debt

$ 300,000,000

Non-recourse debt

234,000,000

Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | DOE Project Financing, 3.092% January 2, 2037 [Member]

Debt Instrument [Line Items]

Outstanding letters of credit

106,000,000

Non-recourse debt, commitment

$ 646,000,000

Non-recourse debt

552,000,000

Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | Denver International Airport [Member]

Debt Instrument [Line Items]

Outstanding borrowings/facility draws

$ 7,000,000

Non-recourse debt

6,000,000

Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | Holyoke [Member]

Debt Instrument [Line Items]

Outstanding borrowings/facility draws

$ 11,000,000

Non-recourse debt

9,000,000

Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | Upstream Gas Property [Member]

Debt Instrument [Line Items]

Non-recourse debt, commitment

$ 85,000,000

Non-recourse debt, commitment increase available

$ 500,000,000

Outstanding borrowings/facility draws

22,000,000

Non-recourse debt

68,000,000

Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | SolGen [Member]

Debt Instrument [Line Items]

Debt Instrument, Face Amount

$ 150,000,000

Non-recourse debt

148,000,000

Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | Renewable Power Generation [Member]

Debt Instrument [Line Items]

Debt Instrument, Face Amount

$ 150,000,000

Non-recourse debt

141,000,000

Exelon Generation Co L L C [Member] | Non Recourse Debt [Member] | Continetal Wind [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 131,000,000

Outstanding letters of credit

108,000,000

Interest rate on long-term debt

6.00%

Debt Instrument, Face Amount

$ 613,000,000

Generation capacity of portfolio | MW

667

Aggregate bank commitments under unsecured revolving credit facilities

$ 10,000,000

Non-recourse debt

$ 543,000,000

Exelon Generation Co L L C [Member] | Maximum [Member] | Senior Notes [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

7.60%

Exelon Generation Co L L C [Member] | Minimum [Member] | Senior Notes [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

2.00%

Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 5,300,000,000

Exelon Generation Co L L C [Member] | Line of Credit [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

[2]

500,000,000

Outstanding letters of credit

[1]

306,000,000

Outstanding borrowings/facility draws

75,000,000

Exelon Generation Co L L C [Member] | Line of Credit [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 200,000,000

$ 150,000,000

$ 100,000,000

Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Outstanding letters of credit

500,000,000

275,000,000

Commonwealth Edison Co [Member]

Debt Instrument [Line Items]

Long-term Debt, Current Maturities

425,000,000

665,000,000

Repayments of Long-term Debt

$ 665,000,000

260,000,000

617,000,000

Credit agreement threshold

2

Outstanding letters of credit

[1]

$ 2,000,000

Basis points adders for prime-based borrowings

7.50%

Basis points adders for LIBOR-based borrowings

107.5

Long-term debt, gross

$ 7,101,000,000

6,567,000,000

Long-term debt

7,307,000,000

Outstanding borrowings/facility draws

0

Commonwealth Edison Co [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

[2],[4],[5]

1,000,000,000

PECO Energy Co [Member]

Debt Instrument [Line Items]

Repayments of Long-term Debt

$ 300,000,000

0

250,000,000

Credit agreement threshold

2

Outstanding letters of credit

[1]

$ 2,000,000

Basis points adders for prime-based borrowings

0.00%

Basis points adders for LIBOR-based borrowings

90

Long-term debt, gross

$ 2,600,000,000

2,600,000,000

Long-term debt

2,784,000,000

Outstanding borrowings/facility draws

0

PECO Energy Co [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

[2],[4],[5]

600,000,000

Baltimore Gas and Electric Company [Member]

Debt Instrument [Line Items]

Repayments of Long-term Debt

$ 379,000,000

75,000,000

70,000,000

Credit agreement threshold

2

Outstanding letters of credit

[1]

$ 0

Basis points adders for prime-based borrowings

0.00%

Basis points adders for LIBOR-based borrowings

100

Long-term debt, gross

$ 2,341,000,000

1,870,000,000

Long-term debt

2,599,000,000

Outstanding borrowings/facility draws

0

Baltimore Gas and Electric Company [Member] | Senior Notes [Member]

Debt Instrument [Line Items]

Long-term debt, gross

$ 2,300,000,000

1,750,000,000

Baltimore Gas and Electric Company [Member] | Maximum [Member] | Senior Notes [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

6.35%

Baltimore Gas and Electric Company [Member] | Minimum [Member] | Senior Notes [Member]

Debt Instrument [Line Items]

Interest rate on long-term debt

2.40%

Baltimore Gas and Electric Company [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

[2]

$ 600,000,000

Pepco Holdings LLC [Member]

Debt Instrument [Line Items]

Long-term debt, gross

5,157,000,000

5,331,000,000

Long-term debt

5,157,000,000

Repayments of Bank Debt

300,000,000

Short-term Bank Loans and Notes Payable

$ 500,000,000

Short-term Debt, Percentage Bearing Variable Interest Rate

1.00%

950000.00%

Pepco Holdings LLC [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

$ 900,000,000

$ 1,500,000,000

Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases

$ 500,000,000

Line of Credit Facility, Maximum Amount Outstanding During Period

$ 750,000,000

Credit agreement threshold

1.25

Potomac Electric Power Company [Member]

Debt Instrument [Line Items]

Repayments of Long-term Debt

$ 11,000,000

22,000,000

184,000,000

Credit agreement threshold

2

Outstanding letters of credit

[1]

$ 0

Basis points adders for prime-based borrowings

7.50%

Basis points adders for LIBOR-based borrowings

107.5

Long-term debt, gross

$ 2,381,000,000

2,385,000,000

Long-term debt

2,381,000,000

Outstanding borrowings/facility draws

0

Potomac Electric Power Company [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

[2]

300,000,000

Delmarva Power and Light Company [Member]

Debt Instrument [Line Items]

Long-term Debt, Current Maturities

105,000,000

Repayments of Long-term Debt

$ 100,000,000

100,000,000

100,000,000

Credit agreement threshold

2

Outstanding letters of credit

[1]

$ 0

Basis points adders for prime-based borrowings

7.50%

Basis points adders for LIBOR-based borrowings

107.5

Long-term debt, gross

$ 1,348,000,000

1,273,000,000

Long-term debt

1,348,000,000

Outstanding borrowings/facility draws

0

Delmarva Power and Light Company [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

[2]

300,000,000

Atlantic City Electric Company [Member]

Debt Instrument [Line Items]

Repayments of Long-term Debt

$ 48,000,000

58,000,000

$ 66,000,000

Credit agreement threshold

2

Outstanding letters of credit

[1]

$ 1,000,000

Basis points adders for prime-based borrowings

7.50%

Basis points adders for LIBOR-based borrowings

107.5

Long-term debt, gross

$ 1,162,000,000

$ 1,210,000,000

Long-term debt

1,162,000,000

Outstanding borrowings/facility draws

0

Atlantic City Electric Company [Member] | Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of credit facility, maximum borrowing capacity

[2]

$ 300,000,000

[1]

Excludes nonrecourse debt letters of credit, see discussion below on Continental Wind.

[2]

Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million ,$5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.

[3]

{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246QjFDN0Q4OTA0OTQyMUZCQTgxMDE5RjkyNUQyN0VERjAM}

[4]

Excludes $500 million and $275 million in bilateral credit facilities that do not back Generation's commercial paper program at December 31, 2016 and 2015, respectively

[5]

Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million, $5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Benefit) from Continuing Operations (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Income taxes			$ 761	$ 1,073	$ 666
Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Income taxes			290	502	207
Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Income taxes			301	280	268
PECO Energy Co [Member]
Income Taxes [Line Items]
Income taxes			149	143	114
Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Income taxes			174	189	140
Potomac Electric Power Company [Member]
Income Taxes [Line Items]
Income taxes			41	102	93
Delmarva Power and Light Company [Member]
Income Taxes [Line Items]
Income taxes			22	49	65
Atlantic City Electric Company [Member]
Income Taxes [Line Items]
Income taxes			(4)	33	30
Pepco Holdings LLC [Member] | Successor [Member]
Income Taxes [Line Items]
Income taxes		$ 3
Pepco Holdings LLC [Member] | Predecessor [Member]
Income Taxes [Line Items]
Income taxes	$ 17			163	138
Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Current			60	407	121
Deferred			607	566	576
Investment Tax Credit			(24)	(22)	(20)
Internal Revenue Service (IRS) [Member] | Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Current			513	546	360
Deferred			(247)	16	(35)
Investment Tax Credit			(20)	(19)	(16)
Internal Revenue Service (IRS) [Member] | Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Current			(135)	(80)	(171)
Deferred			379	310	395
Investment Tax Credit			(2)	(2)	(2)
Internal Revenue Service (IRS) [Member] | PECO Energy Co [Member]
Income Taxes [Line Items]
Current			63	64	28
Deferred			72	69	87
Investment Tax Credit			0	0	0
Internal Revenue Service (IRS) [Member] | Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Current			51	25	24
Deferred			88	126	90
Investment Tax Credit			(1)	(1)	(1)
Internal Revenue Service (IRS) [Member] | Potomac Electric Power Company [Member]
Income Taxes [Line Items]
Current			(118)	(54)	(79)
Deferred			136	126	150
Investment Tax Credit			0	0	0
Internal Revenue Service (IRS) [Member] | Delmarva Power and Light Company [Member]
Income Taxes [Line Items]
Current			(88)	(27)	(45)
Deferred			97	73	98
Investment Tax Credit			0	0	(1)
Internal Revenue Service (IRS) [Member] | Atlantic City Electric Company [Member]
Income Taxes [Line Items]
Current			(26)	(2)	(6)
Deferred			22	27	31
Investment Tax Credit			0	0	(1)
Internal Revenue Service (IRS) [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Income Taxes [Line Items]
Current		(281)
Deferred		283
Investment Tax Credit		(1)
Internal Revenue Service (IRS) [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Income Taxes [Line Items]
Current	0			12	(153)
Deferred	10			103	261
Investment Tax Credit	0			(1)	(1)
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Current			39	(86)	42
Deferred			79	208	(53)
State and Local Jurisdiction [Member] | Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Current			45	(90)	35
Deferred			(1)	49	(137)
State and Local Jurisdiction [Member] | Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Current			(4)	7	7
Deferred			63	45	39
State and Local Jurisdiction [Member] | PECO Energy Co [Member]
Income Taxes [Line Items]
Current			9	(10)	(2)
Deferred			5	20	1
State and Local Jurisdiction [Member] | Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Current			5	0	0
Deferred			31	39	27
State and Local Jurisdiction [Member] | Potomac Electric Power Company [Member]
Income Taxes [Line Items]
Current			7	6	(2)
Deferred			16	24	24
State and Local Jurisdiction [Member] | Delmarva Power and Light Company [Member]
Income Taxes [Line Items]
Current			1	2	0
Deferred			12	1	13
State and Local Jurisdiction [Member] | Atlantic City Electric Company [Member]
Income Taxes [Line Items]
Current			0	3	(1)
Deferred			$ 0	5	7
State and Local Jurisdiction [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Income Taxes [Line Items]
Current		(11)
Deferred		$ 13
State and Local Jurisdiction [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Income Taxes [Line Items]
Current	0			17	(10)
Deferred	$ 7			$ 32	$ 41

Income Taxes - Reconciliation t

Income Taxes - Reconciliation to Effective Tax Rate (Details)		3 Months Ended		9 Months Ended	12 Months Ended
		Mar. 23, 2016		Dec. 31, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Income Taxes [Line Items]
U.S. Federal statutory rate					35.00%		35.00%		35.00%
State income taxes, net of Federal income tax benefit (b)					3.30%	[1]	3.70%		1.30%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent					3.40%		(0.40%)		2.40%
Domestic production activities deduction					(0.00%)		(0.70%)		(2.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent					0.00%		0.00%		0.10%
Amortization of investment tax credit, including deferred taxes on basis difference					(1.20%)		(0.90%)		(1.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent					(4.80%)		(1.50%)		(1.90%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent					(3.60%)		(1.90%)		(2.40%)
Noncontrolling interests					(0.20%)		(0.30%)		(1.80%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent					(0.40%)		(1.40%)		(2.60%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent					1.90%
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent					5.50%
Other (c)					(0.60%)		0.00%		(0.20%)
Effective income tax rate					38.30%		32.20%		26.80%
Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
U.S. Federal statutory rate					35.00%		35.00%		35.00%
State income taxes, net of Federal income tax benefit (b)					3.30%		1.00%		(1.90%)
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent					7.80%		(0.80%)		4.80%
Domestic production activities deduction					(0.00%)		(1.30%)		(4.10%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent					0.00%		0.00%		0.00%
Amortization of investment tax credit, including deferred taxes on basis difference					(2.30%)		(1.50%)		(2.00%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent					(8.20%)		(3.40%)		(4.80%)
Noncontrolling interests					(0.30%)		(0.50%)		(3.70%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent					(1.70%)		(2.40%)		(5.30%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent					(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent					1.10%
Other (c)					(1.50%)		0.00%		(1.10%)
Effective income tax rate					33.20%		27.10%		16.90%
Commonwealth Edison Co [Member]
Income Taxes [Line Items]
U.S. Federal statutory rate					35.00%		35.00%		35.00%
State income taxes, net of Federal income tax benefit (b)					5.60%		4.90%		4.50%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent					0.00%		0.00%		0.00%
Domestic production activities deduction					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent					0.00%		0.00%		0.20%
Amortization of investment tax credit, including deferred taxes on basis difference					(0.30%)		(0.30%)		(0.30%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent					(0.60%)		(0.10%)		(0.10%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent					(0.00%)		(0.00%)		(0.00%)
Noncontrolling interests					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent					4.50%
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent					0.00%
Other (c)					0.10%		0.20%		0.30%
Effective income tax rate					44.30%		39.70%		39.60%
PECO Energy Co [Member]
Income Taxes [Line Items]
U.S. Federal statutory rate					35.00%		35.00%		35.00%
State income taxes, net of Federal income tax benefit (b)					1.30%		1.00%		(0.10%)
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent					0.00%		0.00%		0.00%
Domestic production activities deduction					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent					0.00%		0.00%		0.00%
Amortization of investment tax credit, including deferred taxes on basis difference					(0.10%)		(0.10%)		(0.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent					(9.60%)		(8.70%)		(10.40%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent					(0.00%)		(0.00%)		(0.00%)
Noncontrolling interests					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent					(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent					0.00%
Other (c)					(1.20%)	[2]	0.20%		0.10%
Effective income tax rate					25.40%		27.40%		24.50%
Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
U.S. Federal statutory rate					35.00%		35.00%		35.00%
State income taxes, net of Federal income tax benefit (b)					5.00%		5.30%		5.00%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent					0.00%		0.00%		0.00%
Domestic production activities deduction					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent					0.00%		0.10%		0.20%
Amortization of investment tax credit, including deferred taxes on basis difference					(0.10%)		(0.10%)		(0.30%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent					(2.70%)		(0.70%)		0.20%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent					(0.00%)		(0.00%)		(0.00%)
Noncontrolling interests					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent					(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent					0.00%
Other (c)					0.00%		0.00%		(0.20%)
Effective income tax rate					37.20%		39.60%		39.90%
Potomac Electric Power Company [Member]
Income Taxes [Line Items]
U.S. Federal statutory rate					35.00%		35.00%		35.00%
State income taxes, net of Federal income tax benefit (b)					15.70%	[1]	6.70%		5.40%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent					0.00%		0.00%		0.00%
Domestic production activities deduction					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent					0.00%		0.00%		0.00%
Amortization of investment tax credit, including deferred taxes on basis difference					(0.20%)		(0.10%)		(0.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent					(22.80%)		(5.80%)		(4.90%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent					(0.00%)		(0.00%)		(0.00%)
Noncontrolling interests					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent					(0.00%)		(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent					(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent					23.50%
Other (c)					(1.80%)		(0.50%)	[3]	(0.20%)
Effective income tax rate					49.40%		35.30%		35.20%
Delmarva Power and Light Company [Member]
Income Taxes [Line Items]
U.S. Federal statutory rate					35.00%	[4]	35.00%		35.00%
State income taxes, net of Federal income tax benefit (b)					52.70%	[1],[4]	1.70%		4.80%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent					0.00%	[4]	0.00%		0.00%
Domestic production activities deduction					(0.00%)	[4]	(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent					0.00%	[4]	0.00%		0.00%
Amortization of investment tax credit, including deferred taxes on basis difference					(3.70%)	[4]	(0.40%)		(0.30%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent					(25.50%)	[4]	(2.30%)		(2.40%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent					(0.00%)	[4]	(0.00%)		(0.00%)
Noncontrolling interests					(0.00%)	[4]	(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent					(0.00%)	[4]	(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	[4]				(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent	[4]				112.90%
Other (c)					(2.20%)	[4]	5.20%	[3]	1.40%
Effective income tax rate					169.20%	[4]	39.20%		38.50%
Atlantic City Electric Company [Member]
Income Taxes [Line Items]
U.S. Federal statutory rate					35.00%	[4]	35.00%		35.00%
State income taxes, net of Federal income tax benefit (b)					6.20%	[4]	5.70%		5.80%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent					0.00%	[4]	0.00%		0.00%
Domestic production activities deduction					(0.00%)	[4]	(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent					0.00%	[4]	0.00%		0.00%
Amortization of investment tax credit, including deferred taxes on basis difference					0.80%	[4]	(0.60%)		(0.60%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent					10.30%	[4]	(1.30%)		(0.50%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent					(0.00%)	[4]	(0.00%)		(0.00%)
Noncontrolling interests					(0.00%)	[4]	(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent					(0.00%)	[4]	(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	[4]				(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent	[4]				(44.90%)
Other (c)					1.30%	[4]	6.40%	[3]	(0.20%)
Effective income tax rate					8.70%	[4]	45.20%		39.50%
Pepco Holdings LLC [Member] | Successor [Member]
Income Taxes [Line Items]
U.S. Federal statutory rate	[4]				35.00%
State income taxes, net of Federal income tax benefit (b)	[1],[4]			5.80%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	[4]			0.00%
Domestic production activities deduction	[4]			(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent	[4]			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	[4]			1.40%
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent	[4]			39.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	[4]			(0.00%)
Noncontrolling interests	[4]			(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	[4]			(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	[4]			(0.70%)
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent	[4]			(89.00%)
Other (c)	[4]			3.30%
Effective income tax rate	[4]			(5.20%)
Pepco Holdings LLC [Member] | Predecessor [Member]
Income Taxes [Line Items]
U.S. Federal statutory rate					35.00%	[4]	35.00%		35.00%
State income taxes, net of Federal income tax benefit (b)		11.90%	[1],[4]				6.60%		5.30%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent		0.00%	[4]				0.00%		0.00%
Domestic production activities deduction		(0.00%)	[4]				(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Medicare Prescription Drug Benefit, Percent		0.00%	[4]				0.00%		0.00%
Amortization of investment tax credit, including deferred taxes on basis difference		(0.90%)	[4]				(0.20%)		(0.30%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		(13.50%)	[4]				(4.30%)		(4.50%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent		(0.00%)	[4]				(0.00%)		(0.00%)
Noncontrolling interests		(0.00%)	[4]				(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent		(0.00%)	[4]				(0.00%)		(0.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent	[4]	(0.00%)
Effective Income Tax Rate Reconciliation, Deduction, Other, Percent	[4]	11.10%
Other (c)		3.60%	[4]				(3.20%)	[3]	0.80%
Effective income tax rate		47.20%	[4]				33.90%		36.30%
[1]	Includes a remeasurement of uncertain state income tax positions for Pepco and DPL.
[2]	At PECO, includes a cumulative adjustment related to an anticipated gas repairs tax return accounting method change.
[3]	Includes impacts of the PHI Global Settlement for Pepco, DPL, ACE, and PHI
[4]	DPL and ACE recognized a loss before income taxes for the year ended December 31, 2016, and PHI recognized a loss before income taxes for the period of March 24, 2016, through December 31, 2016. As a result, positive percentages represent an income tax benefit for the periods presented.

Income Taxes - Tax Effects of T

Income Taxes - Tax Effects of Temporary Differences and Carryforwards (Details) - USD ($) $ in Millions	Dec. 31, 2016	Mar. 24, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Plant basis differences	$ (17,966)		$ (13,393)
Accrual based contracts	434		(136)
Derivatives and other financial instruments	(179)		(203)
Deferred pension and postretirement obligation	2,287		1,801
Nuclear decommissioning activities	(509)		(592)
Deferred debt refinancing costs	325		133
Deferred Tax Liabilities, Regulatory Assets and Liabilities	3,319		1,706
Tax loss carryforward	189		103
Tax credit carryforward	446		327
Investment in CENG	(650)		(595)
Other, net	1,485	$ (59)	1,112
Deferred income tax liabilities (net)	(17,457)		(13,149)
Unamortized investment tax credits	(658)		(622)
Total deferred income tax liabilities (net) and unamortized investment tax credits	(18,115)		(13,771)
Exelon Generation Co L L C [Member]
Operating Loss Carryforwards [Line Items]
Plant basis differences	(4,192)		(4,269)
Accrual based contracts	(115)		(136)
Derivatives and other financial instruments	(162)		(181)
Deferred pension and postretirement obligation	(316)		(371)
Nuclear decommissioning activities	(509)		(592)
Deferred debt refinancing costs	44		48
Regulatory assets and liabilities			0
Deferred Tax Liabilities, Regulatory Assets and Liabilities	0
Tax loss carryforward	61		56
Tax credit carryforward	493		374
Investment in CENG	(650)		(595)
Other, net	403		425
Deferred income tax liabilities (net)	(4,943)		(5,241)
Unamortized investment tax credits	(626)		(598)
Total deferred income tax liabilities (net) and unamortized investment tax credits	(5,569)		(5,839)
Commonwealth Edison Co [Member]
Operating Loss Carryforwards [Line Items]
Plant basis differences	(5,034)		(4,424)
Accrual based contracts	0		0
Derivatives and other financial instruments	(3)		(4)
Deferred pension and postretirement obligation	(453)		(505)
Nuclear decommissioning activities	0		0
Deferred debt refinancing costs	13		15
Deferred Tax Liabilities, Regulatory Assets and Liabilities	226		219
Tax loss carryforward	29		0
Tax credit carryforward	0		0
Investment in CENG	0		0
Other, net	351		270
Deferred income tax liabilities (net)	(5,349)		(4,897)
Unamortized investment tax credits	(15)		(17)
Total deferred income tax liabilities (net) and unamortized investment tax credits	(5,364)		(4,914)
PECO Energy Co [Member]
Operating Loss Carryforwards [Line Items]
Plant basis differences	(3,095)		(2,901)
Accrual based contracts	0		0
Derivatives and other financial instruments	0		0
Deferred pension and postretirement obligation	(18)		(9)
Nuclear decommissioning activities	0		0
Deferred debt refinancing costs	1		1
Deferred Tax Liabilities, Regulatory Assets and Liabilities	10		(16)
Tax loss carryforward	0		0
Tax credit carryforward	0		0
Investment in CENG	0		0
Other, net	99		105
Deferred income tax liabilities (net)	(3,005)		(2,790)
Unamortized investment tax credits	(1)		(2)
Total deferred income tax liabilities (net) and unamortized investment tax credits	(3,006)		(2,792)
Baltimore Gas and Electric Company [Member]
Operating Loss Carryforwards [Line Items]
Plant basis differences	(1,977)		(1,821)
Accrual based contracts	0		0
Derivatives and other financial instruments	0		0
Deferred pension and postretirement obligation	(43)		(47)
Nuclear decommissioning activities	0		0
Deferred debt refinancing costs	3		4
Deferred Tax Liabilities, Regulatory Assets and Liabilities	240		264
Tax loss carryforward	22		33
Tax credit carryforward	0		0
Investment in CENG	0		0
Other, net	27		27
Deferred income tax liabilities (net)	(2,214)		(2,076)
Unamortized investment tax credits	(5)		(5)
Total deferred income tax liabilities (net) and unamortized investment tax credits	(2,219)		(2,081)
Potomac Electric Power Company [Member]
Operating Loss Carryforwards [Line Items]
Plant basis differences	(1,678)		(1,599)
Accrual based contracts	0		0
Derivatives and other financial instruments	0		0
Deferred pension and postretirement obligation	(122)		(95)
Nuclear decommissioning activities	0		0
Deferred debt refinancing costs	7		8
Deferred Tax Liabilities, Regulatory Assets and Liabilities	194		202
Tax loss carryforward	27		141
Tax credit carryforward	0		0
Investment in CENG	0		0
Other, net	66		42
Deferred income tax liabilities (net)	(1,908)		(1,721)
Unamortized investment tax credits	(2)		(2)
Total deferred income tax liabilities (net) and unamortized investment tax credits	(1,910)		(1,723)
Delmarva Power and Light Company [Member]
Operating Loss Carryforwards [Line Items]
Plant basis differences	(973)		(915)
Accrual based contracts	0		0
Derivatives and other financial instruments	0		0
Deferred pension and postretirement obligation	(74)		(82)
Nuclear decommissioning activities	0		0
Deferred debt refinancing costs	4		4
Deferred Tax Liabilities, Regulatory Assets and Liabilities	75		91
Tax loss carryforward	39		122
Tax credit carryforward	0		0
Investment in CENG	0		0
Other, net	34		29
Deferred income tax liabilities (net)	(1,053)		(941)
Unamortized investment tax credits	(3)		(4)
Total deferred income tax liabilities (net) and unamortized investment tax credits	(1,056)		(945)
Atlantic City Electric Company [Member]
Operating Loss Carryforwards [Line Items]
Plant basis differences	(869)		(791)
Accrual based contracts	0		0
Derivatives and other financial instruments	0		0
Deferred pension and postretirement obligation	(21)		(20)
Nuclear decommissioning activities	0		0
Deferred debt refinancing costs	2		3
Deferred Tax Liabilities, Regulatory Assets and Liabilities	69		93
Tax loss carryforward	14		8
Tax credit carryforward	0		0
Investment in CENG	0		0
Other, net	34		18
Deferred income tax liabilities (net)	(913)		(881)
Unamortized investment tax credits	(4)		(4)
Total deferred income tax liabilities (net) and unamortized investment tax credits	(917)		(885)
Pepco Holdings LLC [Member] | Successor [Member]
Operating Loss Carryforwards [Line Items]
Plant basis differences	(3,586)
Accrual based contracts	548
Derivatives and other financial instruments	(1)
Deferred pension and postretirement obligation	(111)
Nuclear decommissioning activities	0
Deferred debt refinancing costs	293
Deferred Tax Liabilities, Regulatory Assets and Liabilities	1,205
Tax loss carryforward	77
Tax credit carryforward	0
Investment in CENG	0
Other, net	225
Deferred income tax liabilities (net)	(3,760)
Unamortized investment tax credits	(9)
Total deferred income tax liabilities (net) and unamortized investment tax credits	$ (3,769)
Pepco Holdings LLC [Member] | Predecessor [Member]
Operating Loss Carryforwards [Line Items]
Plant basis differences			(3,342)
Accrual based contracts			0
Derivatives and other financial instruments			(1)
Deferred pension and postretirement obligation			(92)
Nuclear decommissioning activities			0
Deferred debt refinancing costs			15
Deferred Tax Liabilities, Regulatory Assets and Liabilities			414
Tax loss carryforward			378
Tax credit carryforward			6
Investment in CENG			0
Other, net		$ (8)	103
Deferred income tax liabilities (net)			(3,377)
Unamortized investment tax credits			(15)
Total deferred income tax liabilities (net) and unamortized investment tax credits			$ (3,392)

Income Taxes - Schedule of Carr

Income Taxes - Schedule of Carryforwards and Corresponding Valuation Allowances (Details) $ in Millions	Dec. 31, 2016USD ($)
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	$ 99
State net operating losses and credit carryforwards	282	[1]
Internal Revenue Service (IRS) [Member] | Exelon Generation Co L L C [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	4
State net operating losses and credit carryforwards	11
Internal Revenue Service (IRS) [Member] | Commonwealth Edison Co [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	29
State net operating losses and credit carryforwards	82
Internal Revenue Service (IRS) [Member] | PECO Energy Co [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	0
State net operating losses and credit carryforwards	0
Internal Revenue Service (IRS) [Member] | Baltimore Gas and Electric Company [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	0
State net operating losses and credit carryforwards	0
Internal Revenue Service (IRS) [Member] | Potomac Electric Power Company [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	15
State net operating losses and credit carryforwards	44
Internal Revenue Service (IRS) [Member] | Delmarva Power and Light Company [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	13
State net operating losses and credit carryforwards	38
Internal Revenue Service (IRS) [Member] | Atlantic City Electric Company [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	6
State net operating losses and credit carryforwards	18
Internal Revenue Service (IRS) [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	42
State net operating losses and credit carryforwards	121
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	511	[2]
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Exelon Generation Co L L C [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	509
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Commonwealth Edison Co [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	1
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | PECO Energy Co [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	0
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Baltimore Gas and Electric Company [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	1
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Potomac Electric Power Company [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	0
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Delmarva Power and Light Company [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	0
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Atlantic City Electric Company [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	0
Internal Revenue Service (IRS) [Member] | General Business Tax Credit Carryforward [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Operating Loss Carryforwards [Line Items]
Federal general business credits carryforwards	0
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	3,501	[3]
Deferred taxes on state tax attributes (net)	186
Valuation allowance on state tax attributes	20
State and Local Jurisdiction [Member] | Exelon Generation Co L L C [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	1,245	[3]
Deferred taxes on state tax attributes (net)	65
Valuation allowance on state tax attributes	9
State and Local Jurisdiction [Member] | Commonwealth Edison Co [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	0
Deferred taxes on state tax attributes (net)	0
Valuation allowance on state tax attributes	0
State and Local Jurisdiction [Member] | PECO Energy Co [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	0
Deferred taxes on state tax attributes (net)	0
Valuation allowance on state tax attributes	0
State and Local Jurisdiction [Member] | Baltimore Gas and Electric Company [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	425	[4]
Deferred taxes on state tax attributes (net)	23
Valuation allowance on state tax attributes	1
State and Local Jurisdiction [Member] | Potomac Electric Power Company [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	360	[5]
Deferred taxes on state tax attributes (net)	20
Valuation allowance on state tax attributes	0
State and Local Jurisdiction [Member] | Delmarva Power and Light Company [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	639	[6]
Deferred taxes on state tax attributes (net)	36
Valuation allowance on state tax attributes	0
State and Local Jurisdiction [Member] | Atlantic City Electric Company [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	272	[7]
Deferred taxes on state tax attributes (net)	16
Valuation allowance on state tax attributes	0
State and Local Jurisdiction [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Operating Loss Carryforwards [Line Items]
State net operating losses and credit carryforwards	1,522	[8]
Deferred taxes on state tax attributes (net)	86
Valuation allowance on state tax attributes	$ 10
[1]	Exelon's federal net operating loss will begin expiring in 2032.
[2]	Exelon’s federal general business credit carryforwards will begin expiring in 2033.
[3]	Exelon’s and Generation's state net operating losses and credit carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2017.
[4]	BGE's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2026
[5]	Pepco's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2028
[6]	DPL's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2023.
[7]	ACE's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2032.
[8]	PHI's state net operating loss carryforwards, which are presented on a post-apportioned basis, will begin expiring in 2023.

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance	$ 1,078	$ 1,829	$ 2,175
Increases based on tax positions related to current year	108	108	15
Unrecognized Tax Benefits, Increase Resulting from Acquisition	22
Unrecognized Tax Benefits, Period Increase (Decrease)	(332)	(705)	(255)
Increases based on tax positions prior to current year	88	79	18
Decreases based on tax positions prior to current year	(21)	(116)	(1)
Decrease from settlements with taxing authorities	(27)	(31)	(35)
Unrecognized tax benefits - ending balance	916	1,078	1,829
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	(86)	(88)
Exelon Generation Co L L C [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance	534	1,357	1,415
Increases based on tax positions related to current year	10	0	15
Unrecognized Tax Benefits, Increase Resulting from Acquisition	5
Unrecognized Tax Benefits, Period Increase (Decrease)	(12)	(659)	33
Increases based on tax positions prior to current year	0	65	18
Decreases based on tax positions prior to current year	(20)	(112)	(2)
Decrease from settlements with taxing authorities	(27)	(31)	(34)
Unrecognized tax benefits - ending balance	490	534	1,357
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	(86)	(88)
Commonwealth Edison Co [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance	142	149	324
Increases based on tax positions related to current year	0	0	0
Unrecognized Tax Benefits, Period Increase (Decrease)	(154)	(7)	(175)
Increases based on tax positions prior to current year	0	0	0
Decreases based on tax positions prior to current year	0	0	0
Decrease from settlements with taxing authorities	0	0	0
Unrecognized tax benefits - ending balance	(12)	142	149
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	0	0
PECO Energy Co [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance	0	44	44
Increases based on tax positions related to current year	0	0	0
Unrecognized Tax Benefits, Period Increase (Decrease)	0	(44)	0
Increases based on tax positions prior to current year	0	0	0
Decreases based on tax positions prior to current year	0	0	0
Decrease from settlements with taxing authorities	0	0	0
Unrecognized tax benefits - ending balance	0	0	44
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	0	0
Baltimore Gas and Electric Company [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance	120	0	0
Increases based on tax positions related to current year	0	106	0
Unrecognized Tax Benefits, Period Increase (Decrease)	0	0	0
Increases based on tax positions prior to current year	0	14	0
Decreases based on tax positions prior to current year	0	0	0
Decrease from settlements with taxing authorities	0	0	0
Unrecognized tax benefits - ending balance	120	120	0
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	0	0
Potomac Electric Power Company [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance	8	0	45
Increases based on tax positions related to current year	21	0	0
Unrecognized Tax Benefits, Period Increase (Decrease)	0	0	(45)
Increases based on tax positions prior to current year	51	8	0
Decreases based on tax positions prior to current year	0	0	0
Decrease from settlements with taxing authorities	0	0	0
Unrecognized tax benefits - ending balance	80	8	0
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	0	0
Delmarva Power and Light Company [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance	3	0	3
Increases based on tax positions related to current year	16	0	0
Unrecognized Tax Benefits, Period Increase (Decrease)	0	0	(3)
Increases based on tax positions prior to current year	18	3	0
Decreases based on tax positions prior to current year	0	0	0
Decrease from settlements with taxing authorities	0	0	0
Unrecognized tax benefits - ending balance	37	3	0
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	0	0
Atlantic City Electric Company [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance	0	0	3
Increases based on tax positions related to current year	22	0	0
Unrecognized Tax Benefits, Period Increase (Decrease)	0	0	(3)
Increases based on tax positions prior to current year	0	0	0
Decreases based on tax positions prior to current year	0	0	0
Decrease from settlements with taxing authorities	0	0	0
Unrecognized tax benefits - ending balance	22	0	0
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0	0	0
Pepco Holdings LLC [Member] | Successor [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance	22
Increases based on tax positions related to current year	59
Unrecognized Tax Benefits, Increase Resulting from Acquisition	(5)
Unrecognized Tax Benefits, Period Increase (Decrease)	0
Increases based on tax positions prior to current year	96
Decreases based on tax positions prior to current year	0
Decrease from settlements with taxing authorities	0
Unrecognized tax benefits - ending balance	172	22
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations	0
Pepco Holdings LLC [Member] | Predecessor [Member]
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits - beginning balance	$ 22	702	743
Increases based on tax positions related to current year		0	0
Unrecognized Tax Benefits, Period Increase (Decrease)		(688)	(41)
Increases based on tax positions prior to current year		11	0
Decreases based on tax positions prior to current year		0	0
Decrease from settlements with taxing authorities		0	0
Unrecognized tax benefits - ending balance		22	702
Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations		$ (3)	$ 0

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Mar. 23, 2016	Dec. 31, 2015	Mar. 31, 2013	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 15, 2016	Mar. 31, 2016	Mar. 24, 2016	Dec. 15, 2015	Dec. 31, 2013	Dec. 31, 1999
Income Taxes [Line Items]
Tax positions for which there is uncertainty about the timing of tax benefits		$ 415		$ 83		$ 83	$ 415	$ 1,122
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		538		633		633	538	701
Unrecognized Tax Benefits		1,078		916		916	1,078	1,829					$ 2,175
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities						8
Common Stock, Value, Issued		(1,112)		(1,485)		(1,485)	(1,112)				$ 59
Deferred Tax Assets, State Taxes				1		1
Unrecognized Tax Benefits						21	116	1
IRS asserted penalties for understatement of tax						106
Taxes accrued		293		723		723	293
Unrecognized Tax Benefits, Income Tax Penalties Accrued				106		106
Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Tax positions for which there is uncertainty about the timing of tax benefits		20		7		7	20	680
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		509		483		483	509	672
Unrecognized Tax Benefits		534		490		490	534	1,357					1,415
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities						14
Common Stock, Value, Issued		(425)		(403)		(403)	(425)
Deferred Tax Assets, State Taxes				6		6
Allocation of federal tax benefit under tax sharing agreement		57		94		94	57	55
Unrecognized Tax Benefits						20	112	2
Taxes accrued		186		239		239	186
Unrecognized Tax Benefits, Income Tax Penalties Accrued				0		0
Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Unrecognized Tax Benefits		120		120		120	120	0	$ 120			$ 120	0
Common Stock, Value, Issued		(27)		(27)		(27)	(27)
Proceeds from Contributions from Parent						61	7	0
Allocation of federal tax benefit under tax sharing agreement		7		8		8	7
Unrecognized Tax Benefits						0	0	0
Taxes accrued		23		78		78	23
Unrecognized Tax Benefits, Income Tax Penalties Accrued				0		0
Potomac Electric Power Company [Member]
Income Taxes [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate				21		21
Unrecognized Tax Benefits		8		80		80	8	0	59			8	45
Common Stock, Value, Issued		(42)		(66)		(66)	(42)
Tax Adjustments, Settlements, and Unusual Provisions		6
Unrecognized Tax Benefits, Interest on Income Taxes Expense		3
Proceeds from Contributions from Parent						187	112	80
Unrecognized Tax Benefits						0	0	0
Taxes accrued		56		48		48	56
Unrecognized Tax Benefits, Income Tax Penalties Accrued				0		0
Delmarva Power and Light Company [Member]
Income Taxes [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate				16		16
Unrecognized Tax Benefits		3		37		37	3	0	21			3	3
Common Stock, Value, Issued		(29)		(34)		(34)	(29)
Tax Adjustments, Settlements, and Unusual Provisions		3
Proceeds from Contributions from Parent						152	75	130
Unrecognized Tax Benefits						0	0	0
Taxes accrued		3		4		4	3
Unrecognized Tax Benefits, Income Tax Penalties Accrued				0		0
Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Tax positions for which there is uncertainty about the timing of tax benefits		142		(12)		(12)	142	149
Unrecognized Tax Benefits		142		(12)		(12)	142	149					324
Common Stock, Value, Issued		(270)		(351)		(351)	(270)
Proceeds from Contributions from Parent						315	202	273
Unrecognized Tax Benefits						0	0	0
IRS asserted penalties for understatement of tax						86
Taxes accrued		63		330		330	63
Unrecognized Tax Benefits, Income Tax Penalties Accrued				86		86
PECO Energy Co [Member]
Income Taxes [Line Items]
Tax positions for which there is uncertainty about the timing of tax benefits								43
Unrecognized Tax Benefits		0		0		0	0	44					44
Common Stock, Value, Issued		(105)		(99)		(99)	(105)
Proceeds from Contributions from Parent						18	16	24
Allocation of federal tax benefit under tax sharing agreement		16		18		18	16	25
Unrecognized Tax Benefits						0	0	0
Taxes accrued		4		4		4	4
Unrecognized Tax Benefits, Income Tax Penalties Accrued				0		0
Pepco Holdings LLC [Member] | Successor [Member]
Income Taxes [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate				93		93
Unrecognized Tax Benefits		22		172		172	22		$ 80
Common Stock, Value, Issued				(225)		(225)
Proceeds from Contributions from Parent				1,251
Fresh-Start Adjustment, Increase (Decrease), Deferred Income Tax Liabilities, Noncurrent				35		35
Unrecognized Tax Benefits						0
Taxes accrued				65		65
Pepco Holdings LLC [Member] | Predecessor [Member]
Income Taxes [Line Items]
Tax positions for which there is uncertainty about the timing of tax benefits								686
Unrecognized Tax Benefits that Would Impact Effective Tax Rate		11					11	15
Unrecognized Tax Benefits		22					22	702				$ 11	743
Common Stock, Value, Issued		(103)					(103)				$ 8
Tax Adjustments, Settlements, and Unusual Provisions		35
Federal Income Tax Expense (Benefit), Continuing Operations		26
Discontinued Operation, Tax Effect of Discontinued Operation		9
Unrecognized Tax Benefits, Interest on Income Taxes Expense		21
Unrecognized Tax Benefits							0	0
Taxes accrued		77					77
Atlantic City Electric Company [Member]
Income Taxes [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate				22		22
Unrecognized Tax Benefits		0		22		22	0	0					$ 3
Common Stock, Value, Issued		(18)		(34)		(34)	(18)
Tax Adjustments, Settlements, and Unusual Provisions		3
Proceeds from Contributions from Parent						139	95	0
Unrecognized Tax Benefits						0	0	0
Taxes accrued		$ 23		9		9	23
Unrecognized Tax Benefits, Income Tax Penalties Accrued				0		0
Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				146		146
Deferred						607	566	576
Internal Revenue Service (IRS) [Member] | Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				19		19
Deferred						(247)	16	(35)
Internal Revenue Service (IRS) [Member] | Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Deferred						88	126	90
Internal Revenue Service (IRS) [Member] | Potomac Electric Power Company [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				21		21
Deferred						136	126	150
Internal Revenue Service (IRS) [Member] | Delmarva Power and Light Company [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				16		16
Deferred						97	73	98
Internal Revenue Service (IRS) [Member] | Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Deferred						379	310	395
Internal Revenue Service (IRS) [Member] | PECO Energy Co [Member]
Income Taxes [Line Items]
Deferred						72	69	87
Internal Revenue Service (IRS) [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				59		59
Deferred				283
Internal Revenue Service (IRS) [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Income Taxes [Line Items]
Deferred	$ 10						103	261
Internal Revenue Service (IRS) [Member] | Atlantic City Electric Company [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				22		22
Deferred						22	27	31
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				244		244
Unrecognized Tax Benefits that Would Impact Effective Tax Rate				44		44
Deferred						79	208	(53)
State and Local Jurisdiction [Member] | Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				44		44
Deferred						(1)	49	(137)
State and Local Jurisdiction [Member] | Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				120		120
Deferred						31	39	27
State and Local Jurisdiction [Member] | Potomac Electric Power Company [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				59		59
Deferred						16	24	24
State and Local Jurisdiction [Member] | Delmarva Power and Light Company [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				21		21
Deferred						12	1	13
State and Local Jurisdiction [Member] | Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Deferred						63	45	39
State and Local Jurisdiction [Member] | PECO Energy Co [Member]
Income Taxes [Line Items]
Deferred						5	20	1
State and Local Jurisdiction [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Income Taxes [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit				80		80
Deferred				13
State and Local Jurisdiction [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Income Taxes [Line Items]
Deferred	$ 7						32	41
State and Local Jurisdiction [Member] | Atlantic City Electric Company [Member]
Income Taxes [Line Items]
Deferred						0	$ 5	$ 7
Like kind exchange [Member]
Income Taxes [Line Items]
Tax Adjustments, Settlements, and Unusual Provisions					$ 106
Income Tax Examination, Interest Expense					94
Deferred						400
Payments for Other Taxes						1,000
Income Taxes Receivable				80		80
Investment Agreement, Early Termination Fee						1,250
Deferred gain on sale of property														$ 1,200
IRS asserted penalties for understatement of tax						90
Expected non-cash charge to earnings			$ 265
Taxes accrued				335		335				$ 360
Unrecognized Tax Benefits, Income Tax Penalties Accrued				1,400		1,400
Like kind exchange [Member] | Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Tax Adjustments, Settlements, and Unusual Provisions					86
Income Tax Examination, Interest Expense					64
Proceeds from Contributions from Parent					$ 150
Payments for Other Taxes						0
Income Taxes Receivable				345		345
Expected non-cash charge to earnings			172
Noncash contributions from parent			$ 172
Unrecognized Tax Benefits, Income Tax Penalties Accrued				$ 300		$ 300

Income Taxes - Summary of Inter

Income Taxes - Summary of Interest Receivable (Payable) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Net Interest Receivable Payable Related To Uncertain Tax Positions	$ (507)	$ (288)
Unrecognized Tax Benefits, Income Tax Penalties Accrued	(106)
Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Net Interest Receivable Payable Related To Uncertain Tax Positions	46	80
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0
Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Net Interest Receivable Payable Related To Uncertain Tax Positions	(384)	(210)
Unrecognized Tax Benefits, Income Tax Penalties Accrued	(86)
PECO Energy Co [Member]
Income Taxes [Line Items]
Net Interest Receivable Payable Related To Uncertain Tax Positions	8	3
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0
Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Net Interest Receivable Payable Related To Uncertain Tax Positions	(1)	(1)
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0
Potomac Electric Power Company [Member]
Income Taxes [Line Items]
Net Interest Receivable Payable Related To Uncertain Tax Positions	1	20
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0
Delmarva Power and Light Company [Member]
Income Taxes [Line Items]
Net Interest Receivable Payable Related To Uncertain Tax Positions	0	3
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0
Atlantic City Electric Company [Member]
Income Taxes [Line Items]
Net Interest Receivable Payable Related To Uncertain Tax Positions	1	24
Unrecognized Tax Benefits, Income Tax Penalties Accrued	0
Pepco Holdings LLC [Member] | Successor [Member]
Income Taxes [Line Items]
Net Interest Receivable Payable Related To Uncertain Tax Positions	$ 2
Pepco Holdings LLC [Member] | Predecessor [Member]
Income Taxes [Line Items]
Net Interest Receivable Payable Related To Uncertain Tax Positions		$ (34)

Income Taxes - Summary of In135

Income Taxes - Summary of Interest Expense (Income) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Taxes [Line Items]
Unrecognized Tax Benefits, Income Tax Penalties Expense			$ 106
Net interest (income) expense recognized related to uncertain tax positions			165	$ (13)	$ (36)
Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Net interest (income) expense recognized related to uncertain tax positions			(13)	(31)	(50)
Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Unrecognized Tax Benefits, Income Tax Penalties Expense			86
Net interest (income) expense recognized related to uncertain tax positions			117	7	6
PECO Energy Co [Member]
Income Taxes [Line Items]
Net interest (income) expense recognized related to uncertain tax positions			0	0	0
Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Net interest (income) expense recognized related to uncertain tax positions			0	0	1
Potomac Electric Power Company [Member]
Income Taxes [Line Items]
Net interest (income) expense recognized related to uncertain tax positions			6	(4)	(1)
Delmarva Power and Light Company [Member]
Income Taxes [Line Items]
Net interest (income) expense recognized related to uncertain tax positions			0	0	0
Atlantic City Electric Company [Member]
Income Taxes [Line Items]
Net interest (income) expense recognized related to uncertain tax positions			$ (1)	0	(1)
Pepco Holdings LLC [Member] | Successor [Member]
Income Taxes [Line Items]
Net interest (income) expense recognized related to uncertain tax positions		$ (2)
Pepco Holdings LLC [Member] | Predecessor [Member]
Income Taxes [Line Items]
Net interest (income) expense recognized related to uncertain tax positions	$ 0			$ (34)	$ 0

Asset Retirement Obligations -

Asset Retirement Obligations - Nuclear Decommissioning Asset Retirement Obligation Rollforward (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]			$ 446	$ 398	$ 345
Asset Retirement Obligation, Revision of Estimate				2
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]			446	397	345
Asset Retirement Obligation, Revision of Estimate			$ 285		1,300
Asset Retirement Obligation, Current		$ 10		10	7
Exelon Generation Co L L C [Member] | Nuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance			$ 8,246	8,246	6,961
Asset Retirement Obligation, Accretion Expense				436	387
Asset Retirement Obligation, Revision of Estimate		89		61	901
Costs incurred to decommission retired plants				(9)	(3)
ARO ending balance		8,734		8,734	8,246	$ 6,961
Asset Retirement Obligation, Current	[2]	$ 90		$ 90	$ 99
[1]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[2]	Included in Other current liabilities within Exelon’s and Generation’s Consolidated Balance Sheets.

Asset Retirement Obligations137

Asset Retirement Obligations - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Asset Retirement Obligations [Line Items]
Asset Retirement Obligations, Noncurrent	$ 9,111,000,000		$ 9,111,000,000	$ 8,585,000,000
Asset Retirement Obligation, Revision of Estimate			$ 2,000,000
Percent of additional decommissioning shortfall with recourse	50.00%		50.00%
Nuclear decommissioning trust funds	$ 11,061,000,000		$ 11,061,000,000	10,342,000,000
Spent Nuclear Fuel Obligation, Noncurrent	1,024,000,000		1,024,000,000	1,021,000,000
Decommissioning Liability, Noncurrent	14,000,000		14,000,000	90,000,000
Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)	165,000,000		288,000,000
Asset Retirement Obligations, Noncurrent	8,922,000,000		8,922,000,000	8,431,000,000
Asset Retirement Obligation, Revision of Estimate		$ 285,000,000		1,300,000,000
Shortfall of decommissioning funds with recourse	$ 50,000,000		$ 50,000,000
Percent of additional decommissioning shortfall with recourse	5.00%		5.00%
Nuclear decommissioning trust funds	$ 11,061,000,000		$ 11,061,000,000	10,342,000,000
Spent Nuclear Fuel Obligation, Noncurrent	1,024,000,000		1,024,000,000	1,021,000,000
ZionSolutions rent payable	1		1
EnergySolutions letter of credit	200,000,000		$ 200,000,000
Annual average accretion of the ARO			5.00%
Number of years used in present value measurement			30 years
Historical five-year annual average after-tax return on NDT funds			8.00%
Decommissioning Liability, Noncurrent	$ 14,000,000		$ 14,000,000	90,000,000
Exelon Generation Co L L C [Member] | Minimum [Member]
Asset Retirement Obligations [Line Items]
Investment Interest Rate			2.00%
Years after cessation of plant operations			10 years
Estimated annual after tax return on nuclear decommissioning funds	5.30%		5.30%
Exelon Generation Co L L C [Member] | Maximum [Member]
Asset Retirement Obligations [Line Items]
Investment Interest Rate			3.00%
Years after cessation of plant operations			70 years
Estimated annual after tax return on nuclear decommissioning funds	5.90%		5.90%
Nuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligations [Line Items]
Proceeds from Customers			$ 24,000,000
Nuclear Decommissioning Asset Retirement Obligation [Member] | Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Asset Retirement Obligation, Revision of Estimate	$ 89,000,000		61,000,000	901,000,000
Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)			488,000,000	$ 630,000,000
Zion Station [Member] | Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Decommissioning Liability, Noncurrent	$ 111,000,000		$ 111,000,000

Asset Retirement Obligations138

Asset Retirement Obligations - Unrealized Gain on NDT Funds (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligations [Line Items]
Net unrealized gains (losses) on decommissioning trust funds - Regulatory Agreement Units	[1]	$ 216	$ (282)	$ 180
Net unrealized gains (losses) on decommissioning trust funds - Non-Regulatory Agreement Units	[2],[3]	194	(197)	134
Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Unrealized Gain Loss Investment Income Pledged Assets		$ (1)	$ 7	$ 29
[1]	Net unrealized gains (losses) related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets.
[2]	Excludes $(1) million, $7 million and $29 million of net unrealized gains (losses) related to the Zion Station pledged assets in 2016, 2015 and 2014, respectively. Net unrealized gains related to Zion Station pledged assets are included in the Payable for Zion Station decommissioning on Exelon’s and Generation’s Consolidated Balance Sheets.
[3]	Net unrealized gains (losses) related to Generation’s NDT funds with Non-Regulatory Agreement Units are included within Other, net in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income.

Asset Retirement Obligations139

Asset Retirement Obligations - Pledged Assets and Payables to ZionSolutions (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Asset Retirement Obligations [Line Items]
Carrying value of Zion Station pledged assets		$ 113	$ 206
Decommissioning Liability, Noncurrent		14	90
Asset Retirement Obligations, Noncurrent		9,111	8,585
Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Carrying value of Zion Station pledged assets		113	206
Decommissioning Liability, Noncurrent		14	90
Asset Retirement Obligation, Current		10	7
Asset Retirement Obligations, Noncurrent		8,922	8,431
Decommissioning Funds Withdrawal	[1]	878	786
Exelon Generation Co L L C [Member] | Nuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligations [Line Items]
Carrying value of Zion Station pledged assets		113	206
Payable to Zion Solutions	[2]	104	189
Asset Retirement Obligation, Current	[3]	$ 90	$ 99
[1]	(c)Includes project expenses to decommission Zion Station and estimated tax payments on Zion Station NDT fund earnings.
[2]	Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT Funds. The NDT Funds will be utilized to satisfy the tax obligations as gains and losses are realized.
[3]	Included in Other current liabilities within Exelon’s and Generation’s Consolidated Balance Sheets.

Asset Retirement Obligations140

Asset Retirement Obligations - Non-Nuclear Asset Retirement Obligations Rollforward (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended				12 Months Ended
		Dec. 31, 2016		Mar. 23, 2016		Dec. 31, 2016		Sep. 30, 2016		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate										$ 2
Asset Retirement Obligation, Accretion Expense	[1]									446		$ 398		$ 345
Asset Retirement Obligation, Revision of Estimate										2
Nonnuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance				$ 355	[2]			$ 355	[2]	355	[2]	346
Asset Retirement Obligation, Revision of Estimate	[3]					$ 8				34		(10)
Development projects	[4]									11		10
Asset Retirement Obligation, Accretion Expense	[5]									18		16
Payments										(11)		(5)
ARO ending balance		$ 393	[2]			393	[2]			393	[2]	355	[2]	346
Asset Retirement Obligation, Revision of Estimate	[3]					8				34		(10)
Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Period Increase (Decrease)	[6]									22		2
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate								285				1,300
Asset Retirement Obligation, Accretion Expense	[1]									446		397		345
Asset Retirement Obligation, Period Increase (Decrease)		165								288
Asset Retirement Obligation, Revision of Estimate								285				1,300
Asset Retirement Obligation, Current		10				10				10		7
Exelon Generation Co L L C [Member] | Operating Expense [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate										1		(2)
Asset Retirement Obligation, Revision of Estimate										1		(2)
Exelon Generation Co L L C [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance				197	[2]			197	[2]	197	[2]	194
Asset Retirement Obligation, Revision of Estimate	[3]					1				8		(12)
Development projects	[4]									11		10
Asset Retirement Obligation, Accretion Expense	[5]									10		10
Payments										(6)		(3)
ARO ending balance		199	[2]			199	[2]			199	[2]	197	[2]	194
Asset Retirement Obligation, Revision of Estimate	[3]					1				8		(12)
Asset Retirement Obligation, Current		1				1				1		5
Exelon Generation Co L L C [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Period Increase (Decrease)	[6]									22		2
PECO Energy Co [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]									0		0		0
PECO Energy Co [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance				27	[2]			27	[2]	27	[2]	30
Asset Retirement Obligation, Revision of Estimate	[3]									1		(4)
Development projects	[4]									0		0
Asset Retirement Obligation, Accretion Expense	[5]									1		1
Payments										(1)		0
ARO ending balance		28	[2]			28	[2]			28	[2]	27	[2]	30
Asset Retirement Obligation, Revision of Estimate	[3]									1		(4)
PECO Energy Co [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Period Increase (Decrease)	[6]									0		0
Baltimore Gas and Electric Company [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]									0		0		0
Baltimore Gas and Electric Company [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance				18	[2]			18	[2]	18	[2]	18
Asset Retirement Obligation, Revision of Estimate	[3]									7		0
Development projects	[4]									0		0
Asset Retirement Obligation, Accretion Expense	[5]									0		0
Payments										(1)		0
ARO ending balance		24	[2]			24	[2]			24	[2]	18	[2]	18
Asset Retirement Obligation, Revision of Estimate	[3]									7		0
Asset Retirement Obligation, Current		3				3				3		1
Baltimore Gas and Electric Company [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Period Increase (Decrease)	[6]									0		0
Pepco Holdings LLC [Member] | Successor [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate						2
Asset Retirement Obligation, Accretion Expense	[1]					0
Asset Retirement Obligation, Revision of Estimate						2
Pepco Holdings LLC [Member] | Predecessor [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]			0
Pepco Holdings LLC [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Successor [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance				0	[2]			0	[2]	0	[2]	0
Asset Retirement Obligation, Revision of Estimate										14	[3]	0
Development projects										0	[4]	0
Asset Retirement Obligation, Accretion Expense										0	[5]	0
Payments										0		0
ARO ending balance		14	[2]			14	[2]			14	[2]	0	[2]	0
Asset Retirement Obligation, Revision of Estimate										14	[3]	0
Pepco Holdings LLC [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Successor [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Period Increase (Decrease)										0	[6]	0
Pepco Holdings LLC [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Predecessor [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance				8	[2]	8	[2]	8	[2]	8	[2]	7
Asset Retirement Obligation, Accretion Expense	[5]											1
ARO ending balance				8	[2]							8	[2]	7
Potomac Electric Power Company [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]									0		0		0
Potomac Electric Power Company [Member] | Predecessor [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]											0		0
Potomac Electric Power Company [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance				0	[2]			0	[2]	0	[2]	0
Asset Retirement Obligation, Revision of Estimate	[3]									2		0
Development projects	[4]									0		0
Asset Retirement Obligation, Accretion Expense	[5]									0		0
Payments										0		0
ARO ending balance		2	[2]			2	[2]			2	[2]	0	[2]	0
Asset Retirement Obligation, Revision of Estimate	[3]									2		0
Potomac Electric Power Company [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Period Increase (Decrease)	[6]									0		0
Delmarva Power and Light Company [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate										1
Asset Retirement Obligation, Accretion Expense	[1]									0		0		0
Asset Retirement Obligation, Revision of Estimate										1
Delmarva Power and Light Company [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance				0	[2]			0	[2]	0	[2]	0
Asset Retirement Obligation, Revision of Estimate	[3]									9		0
Development projects	[4]									0		0
Asset Retirement Obligation, Accretion Expense	[5]									0		0
Payments										0		0
ARO ending balance		9	[2]			9	[2]			9	[2]	0	[2]	0
Asset Retirement Obligation, Revision of Estimate	[3]									9		0
Delmarva Power and Light Company [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Period Increase (Decrease)	[6]									0		0
Atlantic City Electric Company [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate										2
Asset Retirement Obligation, Accretion Expense	[1]									0
Asset Retirement Obligation, Revision of Estimate										2
Atlantic City Electric Company [Member] | Predecessor [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]											0		0
Atlantic City Electric Company [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance				0	[2]			0	[2]	0	[2]	0
Asset Retirement Obligation, Revision of Estimate	[3]									3		0
Development projects	[4]									0		0
Asset Retirement Obligation, Accretion Expense	[5]									0		0
Payments										0		0
ARO ending balance		3	[2]			3	[2]			3	[2]	0	[2]	0
Asset Retirement Obligation, Revision of Estimate	[3]									3		0
Atlantic City Electric Company [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Period Increase (Decrease)	[6]									0		0
Commonwealth Edison Co [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]									0		0		0
Commonwealth Edison Co [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance				$ 113	[2]			$ 113	[2]	113	[2]	104
Asset Retirement Obligation, Revision of Estimate	[3]									4		6
Development projects	[4]									0		0
Asset Retirement Obligation, Accretion Expense	[5]									7		5
Payments										(3)		(2)
ARO ending balance		121	[2]			121	[2]			121	[2]	113	[2]	$ 104
Asset Retirement Obligation, Revision of Estimate	[3]									4		6
Asset Retirement Obligation, Current		$ 2				$ 2				2		2
Commonwealth Edison Co [Member] | Nonnuclear Decommissioning Asset Retirement Obligation [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Period Increase (Decrease)	[6]									$ 0		$ 0
[1]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[2]	Excludes $1 million, $2 million and $3 million as the current portion of the ARO at December 31, 2016 for Generation, ComEd and BGE, respectively. Excludes $5 million, $2 million and $1 million as the current portion of the ARO at December 31, 2015 for Generation, ComEd and BGE, respectively. This is included in Other current liabilities on the Registrants' respective Consolidated Balance Sheets.
[3]	During the year ended December 31, 2016, Generation recorded an increase of $1 million in Operating and maintenance expense. ComEd, PECO and BGE did not record any adjustments in Operating and maintenance expense for the year ended December 31, 2016. During the year ended December 31, 2015, Generation recorded a decrease of $(2) million in Operating and maintenance expense. ComEd, PECO and BGE did not record any adjustments in Operating and maintenance expense for the year ended December 31, 2015.
[4]	Relates to new AROs recorded due to the construction of solar, wind and other non-nuclear generating sites.
[5]	For ComEd, PECO, and BGE, the majority of the accretion is recorded as an increase to a regulatory asset due to the associated regulatory treatment.
[6]	Reflects a reduction to the ARO resulting primarily from the sales of the New Boston generating site and Upstream business in 2016 and Schuylkill generating station in 2015. See Note 4 — Mergers, Acquisitions, and Dispositions for further information.

Retirement Benefits - Narrative

Retirement Benefits - Narrative (Details) - USD ($) $ in Millions		Dec. 31, 2016	Jan. 01, 2016	Dec. 31, 2014	Jun. 30, 2016	Mar. 31, 2016	Mar. 23, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Increase (Decrease) in Pension Plan Obligations						$ 35
Benefit obligation increase (decrease) reflecting actual census data						8
AOCI valuation adjustment						2
Regulatory asset increase (decrease) due to updated valuation adjustment						27
Defined benefit plan, amounts recognized In regulatory liabilities, before tax						$ 3
Expected qualified pension plan contributions		$ 310						$ 310
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		23						23
Expected other postretirement benefit plan contributions		$ 44						$ 44
Projected Benefit Obligation In Excess Of Plan Assets [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Funded Percentage		80.00%						80.00%		81.00%
Accumulated Benefit Obligation In Excess Of Plan Assets [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Funded Percentage		84.00%						84.00%		85.00%
Exelon Generation Co L L C [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected qualified pension plan contributions		$ 127						$ 127
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		6						6
Expected other postretirement benefit plan contributions		12						12
Commonwealth Edison Co [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected qualified pension plan contributions		33						33
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		1						1
Expected other postretirement benefit plan contributions		2						2
PECO Energy Co [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected qualified pension plan contributions		23						23
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		1						1
Expected other postretirement benefit plan contributions		0						0
Baltimore Gas and Electric Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected qualified pension plan contributions		38						38
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		2						2
Expected other postretirement benefit plan contributions		16						16
Pepco Holdings LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected qualified pension plan contributions		60						60
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		8						8
Expected other postretirement benefit plan contributions		12						12
Pepco Holdings LLC [Member] | Successor [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Increase (decrease) in pension obligation					$ 25
Pepco Holdings LLC [Member] | Projected Benefit Obligation In Excess Of Plan Assets [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Funded Percentage										81.00%
Pepco Holdings LLC [Member] | Accumulated Benefit Obligation In Excess Of Plan Assets [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Funded Percentage										89.00%
Potomac Electric Power Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected qualified pension plan contributions		60						60
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		1						1
Expected other postretirement benefit plan contributions		10						10
Delmarva Power and Light Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected qualified pension plan contributions		0						0
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		0						0
Expected other postretirement benefit plan contributions		0						0
Atlantic City Electric Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected qualified pension plan contributions		0						0
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		0						0
Expected other postretirement benefit plan contributions		0						0
Constellation Legacy Benefit Plans [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected qualified pension plan contributions		$ 21						$ 21
Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		4.04%		3.94%				4.04%		4.29%		3.94%
Current year actuarial loss (gain)								$ 644		$ 476		$ 1,639
Regulatory asset increase (decrease) due to updated valuation adjustment								$ 959		$ (46)		$ 415
Expected return on plan assets		7.00%						7.00%	[1]	7.00%	[1]	7.00%	[1]
Discount rate								4.29%	[2]	3.94%	[3]	4.80%	[4]
Increase (decrease) in pension obligation				$ 361
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		$ 1,360						$ 1,360
Amortization of actuarial loss								(554)		$ (571)		$ (420)
Current year prior service (credit) cost								(60)		0		0
Amortization of prior service (cost) credit								(14)		(13)		(14)
Settlements								0		(2)		(2)
Defined Benefit Plan Accumulated Other Comprehensive Income And Regulatory Assets Before Tax	[5]							$ 1,010		(110)		$ 1,203
Pension Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				4.20%								4.20%
Current year actuarial loss (gain)							$ 0			50		$ 276
Regulatory asset increase (decrease) due to updated valuation adjustment							$ (13)			$ (6)		$ 212
Expected return on plan assets	[1]						6.50%			6.50%		7.00%
Discount rate	[2]									4.20%		5.05%
Amortization of actuarial loss							$ (14)			$ (65)		$ (45)
Amortization of prior service (cost) credit							0			(2)		(2)
Defined Benefit Plan Accumulated Other Comprehensive Income And Regulatory Assets Before Tax	[5]						$ (14)			$ (17)		$ 229
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	[1]						5.00%			5.00%		5.00%
Pension Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets								6.50%
Discount rate								3.96%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		4.04%		3.92%				4.04%		4.29%		3.92%
Current year actuarial loss (gain)								$ (101)		$ (194)		$ 561
Regulatory asset increase (decrease) due to updated valuation adjustment								$ 95		$ (60)		$ (217)
Expected return on plan assets		6.60%	6.71%					6.71%	[1]	6.50%	[1]	6.59%	[1]
Discount rate								4.29%	[2]	3.92%	[3]	4.90%	[4]
Increase (decrease) in pension obligation				$ 117
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months		$ 244						$ 244
Amortization of actuarial loss								(63)		$ (80)		$ (50)
Current year prior service (credit) cost								0		(23)		(1,012)
Amortization of prior service (cost) credit								185		174		122
Settlements								0		0		0
Defined Benefit Plan Accumulated Other Comprehensive Income And Regulatory Assets Before Tax	[5]							$ 115		$ (123)		$ (379)
Other Postretirement Benefit Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				4.15%						4.55%		4.15%
Current year actuarial loss (gain)							$ 0			$ (39)		$ 62
Regulatory asset increase (decrease) due to updated valuation adjustment							$ 1			$ (34)		$ 72
Expected return on plan assets	[1]						6.75%			6.75%		7.25%
Discount rate	[2]						4.55%			4.15%		5.00%
Amortization of actuarial loss							$ (2)			$ (8)		$ (3)
Amortization of prior service (cost) credit							3			13		13
Defined Benefit Plan Accumulated Other Comprehensive Income And Regulatory Assets Before Tax	[5]						$ 1			$ (34)		$ 72
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Rate of Compensation Increase	[1]						5.00%			5.00%		5.00%
Other Postretirement Benefit Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Expected return on plan assets								6.75%
Discount rate								3.80%
[1]	Not applicable to pension and other postretirement benefit plans that do not have plan asset
[2]	)The discount rates above represent the blended rates used to establish the majority of Exelon’s pension and other postretirement benefits costs for the year ended December 31, 2016. Certain benefit plans used individual rates ranging from 3.68%-4.14% and 4.32%-4.43% for pension and other postretirement plans, respectivel
[3]	The discount rates above represent the blended rates used to establish the majority of Exelon's pension and other postretirement benefits costs for the year ended December 31, 2015. Certain benefit plans used individual rates ranging from 3.29%-3.82% and 3.99%-4.06% for pension and other postretirement plans, respectively.
[4]	The discount rates above represent the blended rates used to establish the majority of Exelon’s pension and other postretirement benefits costs for the year ended December 31, 2014. Certain of the other postretirement benefit plans were remeasured as of April 30, 2014 using an expected long-term rate of return on plan assets of 6.59% and a discount rate of 4.30%. Costs for the year ended December 31, 2014 reflect the impact of this remeasurement. On April 1, 2014, Generation assumed operational control of CENG’s nuclear fleet. As a result, Exelon became the sponsor of CENG’s legacy pension and OPEB plans effective July 14, 2014; discount rates for those plans, impacting 2014 costs, ranged from 3.60%-4.30% and 4.09%-4.55%, respectively. See Note 5 - Investment in Constellation Energy Nuclear Group, LLC for further information.
[5]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246QjAwMzBCMDJERTBGRUQzOTAyOTc5RjkyNUQyMzhDMUEM}

Retirement Benefits - Summary o

Retirement Benefits - Summary of Changes in Benefit Obligations (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation at beginning of year		$ 17,753	$ 17,753	$ 18,256
Service cost			354	326	$ 293
Interest cost			830	710	749
Plan participants’ contributions			0	0
Actuarial (gain) loss			567	(582)
Plan amendments			(60)	0
Acquisitions/divestitures(a)			2,667	0
Settlements	[1]		0	(34)
Gross benefits paid			(1,051)	(923)
Net benefit obligation at end of year			21,060	17,753	18,256
Pension Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation at beginning of year		2,490	2,490	2,638
Service cost		12		57	44
Interest cost		26		109	109
Actuarial (gain) loss		(30)		(151)
Gross benefits paid		(2)		(163)
Net benefit obligation at end of year		2,496		2,490	2,638
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation at beginning of year		3,938	3,938	4,197
Service cost			107	119	117
Interest cost			185	167	186
Plan participants’ contributions			54	42
Actuarial (gain) loss			(136)	(341)
Plan amendments			0	(23)
Acquisitions/divestitures(a)			589	0
Settlements	[1]		0	0
Gross benefits paid			(280)	(223)
Net benefit obligation at end of year			4,457	3,938	4,197
Other Postretirement Benefit Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Net benefit obligation at beginning of year		563	$ 563	632
Service cost		1		7	7
Interest cost		6		24	26
Actuarial (gain) loss		(5)		(61)
Gross benefits paid		(1)		(39)
Net benefit obligation at end of year		$ 564		$ 563	$ 632
[1]	____________________ (a)

Retirement Benefits - Summar143

Retirement Benefits - Summary of Changes in Plan Assets (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2015
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		$ 14,347	$ 14,347	$ 14,874
Actual return on plan assets			1,061	(32)
Employer contributions			347	462
Plan participants’ contributions			0	0
Gross benefits paid			(1,051)	(923)
Acquisitions/divestitures(a)			2,087	0
Settlements	[1]		0	(34)
Fair value of net plan assets at end of year			16,791	14,347
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		2,293	2,293	2,430
Actual return on plan assets			128	4
Employer contributions			50	40
Plan participants’ contributions			54	42
Gross benefits paid			(280)	(223)
Acquisitions/divestitures(a)			333	0
Settlements	[1]		0	0
Fair value of net plan assets at end of year			2,578	2,293
Predecessor [Member] | Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		2,018	2,018	2,236
Actual return on plan assets		0		(61)
Employer contributions		4		6
Gross benefits paid		(2)		(163)
Fair value of net plan assets at end of year		2,020		2,018
Predecessor [Member] | Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		348	$ 348	367
Actual return on plan assets		0		1
Employer contributions		1		5
Gross benefits paid		(1)		(39)
Defined Benefit Plan, Other Changes				25
Fair value of net plan assets at end of year		$ 348		$ 348
[1]	____________________ (a)

Retirement Benefits - Balance S

Retirement Benefits - Balance Sheet locations of Benefit Obligations and Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities	$ 21	$ 21
Pension obligations	4,248	3,385
Non-pension postretirement benefit obligations	0	0
Unfunded status (net benefit obligation less plan assets)	4,269	3,406
Pension Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities		6
Pension obligations		466
Non-pension postretirement benefit obligations		0
Unfunded status (net benefit obligation less plan assets)		472
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities	31	27
Pension obligations	0	0
Non-pension postretirement benefit obligations	1,848	1,618
Unfunded status (net benefit obligation less plan assets)	$ 1,879	1,645
Other Postretirement Benefit Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Other current liabilities		0
Pension obligations		0
Non-pension postretirement benefit obligations		215
Unfunded status (net benefit obligation less plan assets)		$ 215

Retirement Benefits - Projected

Retirement Benefits - Projected Benefit Obligations and Accumulated Benefit Obligations in Excess of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Projected Benefit Obligation In Excess Of Plan Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 21,060	$ 17,753
Fair value of net plan assets	16,791	14,347
Accumulated Benefit Obligation In Excess Of Plan Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation	$ 19,930	16,792
Predecessor [Member] | Pepco Holdings LLC [Member] | Projected Benefit Obligation In Excess Of Plan Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation		2,490
Fair value of net plan assets		2,018
Predecessor [Member] | Pepco Holdings LLC [Member] | Accumulated Benefit Obligation In Excess Of Plan Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation		$ 2,275

Retirement Benefits - Component

Retirement Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		$ 354	$ 326	$ 293
Interest cost		830	710	749
Expected return on assets		(1,141)	(1,026)	(994)
Prior service cost (credit)		14	13	14
Actuarial loss		554	571	420
Settlement and other charges(b)		2	2	2
Net periodic benefit cost		613	596	484
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		107	119	117
Interest cost		185	167	186
Expected return on assets		(162)	(151)	(154)
Prior service cost (credit)		(185)	(174)	(122)
Actuarial loss		63	80	50
Settlement and other charges(b)		0	0	0
Net periodic benefit cost		$ 8	41	77
Predecessor [Member] | Pension Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 12		57	44
Interest cost	26		109	109
Expected return on assets	(30)		(140)	(141)
Prior service cost (credit)	0		2	2
Actuarial loss	14		65	45
Net periodic benefit cost	22		93	59
Predecessor [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1		7	7
Interest cost	6		24	26
Expected return on assets	(5)		(22)	(24)
Prior service cost (credit)	(3)		(13)	(13)
Actuarial loss	2		8	3
Net periodic benefit cost	$ 1		$ 4	$ (1)

Retirement Benefits - Compon147

Retirement Benefits - Components of Accumulated Other Comprehensive Income and Regulatory Assets (Liabilities) related to Retirement Plans (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2016	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, amounts recognized in regulatory assets, before tax		$ 27
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				4.04%	4.29%	3.94%
Current year actuarial loss (gain)				$ 644	$ 476	$ 1,639
Amortization of actuarial loss				(554)	(571)	(420)
Current year prior service (credit) cost				(60)	0	0
Amortization of prior service (cost) credit				(14)	(13)	(14)
DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeAndRegulatoryAssetsAcqusition				994	0	0
Settlements				0	(2)	(2)
Total recognized in AOCI and regulatory assets (liabilities)	[1]			1,010	(110)	1,203
Defined benefit plan, amounts recognized in OCI, before tax				51	(64)	788
Defined benefit plan, amounts recognized in regulatory assets, before tax				$ 959	$ (46)	$ 415
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate				4.04%	4.29%	3.92%
Current year actuarial loss (gain)				$ (101)	$ (194)	$ 561
Amortization of actuarial loss				(63)	(80)	(50)
Current year prior service (credit) cost				0	(23)	(1,012)
Amortization of prior service (cost) credit				185	174	122
DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeAndRegulatoryAssetsAcqusition				94	0	0
Settlements				0	0	0
Total recognized in AOCI and regulatory assets (liabilities)	[1]			115	(123)	(379)
Defined benefit plan, amounts recognized in OCI, before tax				20	(63)	(162)
Defined benefit plan, amounts recognized in regulatory assets, before tax				$ 95	(60)	$ (217)
Predecessor [Member] | Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate						4.20%
Current year actuarial loss (gain)			$ 0		50	$ 276
Amortization of actuarial loss			(14)		(65)	(45)
Amortization of prior service (cost) credit			0		(2)	(2)
Total recognized in AOCI and regulatory assets (liabilities)	[1]		(14)		(17)	229
Defined benefit plan, amounts recognized in OCI, before tax			(1)		(11)	17
Defined benefit plan, amounts recognized in regulatory assets, before tax			(13)		$ (6)	$ 212
Predecessor [Member] | Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate					4.55%	4.15%
Current year actuarial loss (gain)			0		$ (39)	$ 62
Amortization of actuarial loss			(2)		(8)	(3)
Amortization of prior service (cost) credit			3		13	13
Total recognized in AOCI and regulatory assets (liabilities)	[1]		1		(34)	72
Defined benefit plan, amounts recognized in OCI, before tax			0		0	0
Defined benefit plan, amounts recognized in regulatory assets, before tax			$ 1		$ (34)	$ 72
[1]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246QjAwMzBCMDJERTBGRUQzOTAyOTc5RjkyNUQyMzhDMUEM}

Retirement Benefits - Gross Acc

Retirement Benefits - Gross Accumulated Other Comprehensive Loss and Regulatory Assets (Liabilities) not Recognized as Components of Periodic Benefit Cost (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)		$ (31)	$ 36
Actuarial loss		8,387	7,310
Total	[1]	8,356	7,346
Benefits included in accumulated other comprehensive income		4,297	4,246
Benefits included in regulatory assets		4,059	3,100
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)		(710)	(812)
Actuarial loss		724	711
Total	[1]	14	(101)
Benefits included in accumulated other comprehensive income		(42)	(63)
Benefits included in regulatory assets		$ 56	(38)
Predecessor [Member] | Pepco Holdings [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)			6
Actuarial loss			910
Total	[1]		916
Benefits included in accumulated other comprehensive income			46
Benefits included in regulatory assets			870
Predecessor [Member] | Pepco Holdings [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Prior service cost (credit)			(88)
Actuarial loss			128
Total	[1]		40
Benefits included in accumulated other comprehensive income			0
Benefits included in regulatory assets			$ 40
[1]	. Retirement Benefits (All Registrants) As of December 31, 2016, Exelon sponsored defined benefit pension plans and other postretirement benefit plans for essentially all employees. Effective March 23, 2016, Exelon became the sponsor of all of PHI's defined benefit pension and other postretirement benefit plans, and assumed PHI's benefit plan obligations and related assets. As a result, PHI's benefit plan net obligation and related regulatory assets were transferred to Exelon and remeasured at the merger date using current assumptions, including discount rates. The table below shows the pension and other postretirement benefit plans in which employees of each operating company participated at December 31, 2016. Operating Company(e)Name of Plan: Generation ComEd PECO BGE BSC PHI Pepco DPL ACEQualified Pension Plans: Exelon Corporation Retirement Program(a) X X X X X Exelon Corporation Cash Balance Pension Plan(a) X X X X X Exelon Corporation Pension Plan for Bargaining Unit Employees(a) X X X Exelon New England Union Employees Pension Plan(a) X Exelon Employee Pension Plan for Clinton, TMI and Oyster Creek(a) X X X X Pension Plan of Constellation Energy Group, Inc.(b) X X X X X Pension Plan of Constellation Energy Nuclear Group, LLC(c) X X X Nine Mile Point Pension Plan(c) X X Constellation Mystic Power, LLC Union Employees Pension Plan Including Plan A and Plan B(b) X Pepco Holdings LLC Retirement Plan(d) X X X X XNon-Qualified Pension Plans: Exelon Corporation Supplemental Pension Benefit Plan and 2000 Excess Benefit Plan(a) X X X X Exelon Corporation Supplemental Management Retirement Plan(a) X X X X X Constellation Energy Group, Inc. Senior Executive Supplemental Plan(b) X X X Constellation Energy Group, Inc. Supplemental Pension Plan(b) X X X Constellation Energy Group, Inc. Benefits Restoration Plan(b) X X X X Constellation Energy Nuclear Plan, LLC Executive Retirement Plan(c) X X Constellation Energy Nuclear Plan, LLC Benefits Restoration Plan(c) X X Baltimore Gas & Electric Company Executive Benefit Plan(b) X X X Baltimore Gas & Electric Company Manager Benefit Plan(b) X X X X Pepco Holdings LLC 2011 Supplemental Executive Retirement Plan(d) X X X X XConectiv Supplemental Executive Retirement Plan (d) X X X XPepco Holdings LLC Combined Executive Retirement Plan (d) X X X Atlantic City Electric Director Retirement Plan (d) X X Operating Company(e)Name of Plan: Generation ComEd PECO BGE BSC PHI Pepco DPL ACEOther Postretirement Benefit Plans: PECO Energy Company Retiree Medical Plan(a) X X X X X Exelon Corporation Health Care Program(a) X X X X X Exelon Corporation Employees’ Life Insurance Plan(a) X X X X X Exelon Corporation Health Reimbursement Arrangement Plan (a) X X X X X Constellation Energy Group, Inc. Retiree Medical Plan(b) X X X X X Constellation Energy Group, Inc. Retiree Dental Plan(b) X X X Constellation Energy Group, Inc. Employee Life Insurance Plan and Family Life Insurance Plan(b) X X X X X Constellation Mystic Power, LLC Post-Employment Medical Account Savings Plan(b) X Exelon New England Union Post-Employment Medical Savings Account Plan(a) X Retiree Medical Plan of Constellation Energy Nuclear Group LLC(c) X X X Retiree Dental Plan of Constellation Energy Nuclear Group LLC(c) X X X Nine Mile Point Nuclear Station, LLC Medical Care and Prescription Drug Plan for Retired Employees(c) X X Pepco Holdings LLC Welfare Plan for Retirees(d) X X X X X______________________(a)These plans are collectively referred to as the legacy Exelon plans.(b)These plans are collectively referred to as the legacy Constellation Energy Group (CEG) Plans.(c)These plans are collectively referred to as the legacy CENG plans.(d)These plans are collectively referred to as the legacy PHI plans.(e)Employees generally remain in their legacy benefit plans when transferring betwe

Retirement Benefits - Compon149

Retirement Benefits - Components of Accumulated Other Comprehensive Income and Regulatory Assets expected to be Amortized as Components of Periodic Benefit Cost (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Future Amortization of Prior Service Cost (Credit)	$ 1
Defined Benefit Plan, Future Amortization of Gain (Loss)	605
Benefits included in accumulated other comprehensive income	606	[1]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax	297
Pension Plan, Defined Benefit [Member] | Regulatory Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax	309
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Future Amortization of Prior Service Cost (Credit)	(188)
Defined Benefit Plan, Future Amortization of Gain (Loss)	55
Benefits included in accumulated other comprehensive income	(133)	[1]
Benefits included in regulatory assets	(63)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Net of Tax	$ (70)
[1]	___________________ (a)Of the $606 million related to pension benefits at December 31, 2016, $297 million and $309 million are expected to be amortized from AOCI and regulatory assets in 2017, respectively. Of the $(133) million related to other postretirement benefits at December 31, 2016, $(70) million and $(63) million are expected to be amortized from AOCI and regulatory assets (liabilities) in 2017, respectively.

Retirement Benefits - Assumptio

Retirement Benefits - Assumptions Used in Calculations (Details)		Dec. 31, 2016	Jan. 01, 2016	Mar. 23, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate		4.04%			4.04%		4.29%		3.94%
Discount rate					4.29%	[1]	3.94%	[2]	4.80%	[3]
Expected return on plan assets		7.00%			7.00%	[4]	7.00%	[4]	7.00%	[4]
Pension Plan, Defined Benefit [Member] | Remeasurement [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate used for remeasurement due to design changes							6.59%
Pension Plan, Defined Benefit [Member] | First Five Years [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Rate of compensation increase					3.25%
Pension Plan, Defined Benefit [Member] | Thereafter [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Rate of compensation increase					3.75%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate		4.04%			4.04%		4.29%		3.92%
Discount rate					4.29%	[1]	3.92%	[2]	4.90%	[3]
Expected return on plan assets		6.60%	6.71%		6.71%	[4]	6.50%	[4]	6.59%	[4]
Health care cost trend rate					5.50%		5.50%		6.00%
Ultimate health care cost trend rate					5.00%		5.00%		5.00%
Other Postretirement Benefit Plan, Defined Benefit [Member] | Remeasurement [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate used for remeasurement due to design changes							4.30%
Other Postretirement Benefit Plan, Defined Benefit [Member] | Remeasurement [Member] | Minimum [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate used for remeasurement due to design changes					4.32%		3.99%		4.09%
Other Postretirement Benefit Plan, Defined Benefit [Member] | Remeasurement [Member] | Maximum [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate used for remeasurement due to design changes					4.43%		4.06%		4.55%
CENG Legacy Benefit Plans [Member] | Minimum [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate used for remeasurement due to design changes					3.68%		3.29%
CENG Legacy Benefit Plans [Member] | Maximum [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate used for remeasurement due to design changes					4.14%		3.82%
CENG Legacy Benefit Plans [Member] | Remeasurement [Member] | Minimum [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate used for remeasurement due to design changes									3.60%
CENG Legacy Benefit Plans [Member] | Remeasurement [Member] | Maximum [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate used for remeasurement due to design changes									4.30%
Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Health care cost trend rate					5.40%		5.40%		5.50%
DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYearAge					0.0633		0.0633		0.0667
Ultimate health care cost trend rate					5.00%		5.00%		5.00%
Predecessor [Member] | Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate									4.20%
Discount rate	[1]						4.20%		5.05%
Expected return on plan assets	[4]			6.50%			6.50%		7.00%
Rate of compensation increase							5.00%		5.00%
Rate of compensation increase	[4]			5.00%			5.00%		5.00%
Predecessor [Member] | Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Assumptions Used In Calculations [Line Items]
Discount rate							4.55%		4.15%
Discount rate	[1]			4.55%			4.15%		5.00%
Expected return on plan assets	[4]			6.75%			6.75%		7.25%
Rate of compensation increase							5.00%		5.00%
Rate of compensation increase	[4]			5.00%			5.00%		5.00%
[1]	)The discount rates above represent the blended rates used to establish the majority of Exelon’s pension and other postretirement benefits costs for the year ended December 31, 2016. Certain benefit plans used individual rates ranging from 3.68%-4.14% and 4.32%-4.43% for pension and other postretirement plans, respectivel
[2]	The discount rates above represent the blended rates used to establish the majority of Exelon's pension and other postretirement benefits costs for the year ended December 31, 2015. Certain benefit plans used individual rates ranging from 3.29%-3.82% and 3.99%-4.06% for pension and other postretirement plans, respectively.
[3]	The discount rates above represent the blended rates used to establish the majority of Exelon’s pension and other postretirement benefits costs for the year ended December 31, 2014. Certain of the other postretirement benefit plans were remeasured as of April 30, 2014 using an expected long-term rate of return on plan assets of 6.59% and a discount rate of 4.30%. Costs for the year ended December 31, 2014 reflect the impact of this remeasurement. On April 1, 2014, Generation assumed operational control of CENG’s nuclear fleet. As a result, Exelon became the sponsor of CENG’s legacy pension and OPEB plans effective July 14, 2014; discount rates for those plans, impacting 2014 costs, ranged from 3.60%-4.30% and 4.09%-4.55%, respectively. See Note 5 - Investment in Constellation Energy Nuclear Group, LLC for further information.
[4]	Not applicable to pension and other postretirement benefit plans that do not have plan asset

Retirement Benefits - Effects o

Retirement Benefits - Effects of One Percentage Point Change in Assumed Health Care Cost Trend Rates (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Compensation and Retirement Disclosure [Abstract]
Effect of a one percentage point increase in assumed healthcare cost trend on 2010 total service and interest cost components	$ 9
Effect of a one percentage point increase in assumed healthcare cost trend on postretirement benefit obligation at December 31, 2010	105
Effect of a one percentage point decrease in assumed healthcare cost trend on 2010 total service and interest cost components	(8)
Effect of a one percentage point decrease in assumed healthcare cost trend on postretirement benefit obligation at December 31, 2010	$ (95)

Retirement Benefits - Contribut

Retirement Benefits - Contributions made to Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended	12 Months Ended
		Mar. 23, 2016		Dec. 31, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense					$ 621		$ 637		$ 561
Pension and non-pension postretirement benefit contributions					397		502		617
Expected qualified pension plan contributions				$ 310	310
Service cost					164		148		103
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year				44	44
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				23	23
Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense	[1]				48		57		46
Service cost	[2]				19		11		10
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions							462		332
Service cost					250
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				1,360	1,360
Pension Plan, Defined Benefit [Member] | Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					39	[3]	47		26
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					50		40	[4]	291	[4]
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				244	244
Other Postretirement Benefit Plan, Defined Benefit [Member] | Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					3		3	[4]	20	[4]
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense					218		269		250
Pension and non-pension postretirement benefit contributions					152		245		297
Expected qualified pension plan contributions				127	127
Service cost					79		80		51
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year				12	12
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				6	6
Exelon Generation Co L L C [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					140	[3]	231		173
Exelon Generation Co L L C [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					12		14	[4]	124	[4]
Exelon Corporate [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					6	[3]	5		9
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense					166		206		162
Pension and non-pension postretirement benefit contributions					38		150		248
Expected qualified pension plan contributions				33	33
Service cost					34		32		26
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year				2	2
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				1	1
Commonwealth Edison Co [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					33	[3]	143		122
Commonwealth Edison Co [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					5		7	[4]	125	[4]
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense					33		39		36
Pension and non-pension postretirement benefit contributions					30		40		16
Expected qualified pension plan contributions				23	23
Service cost					10		11		8
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year				0	0
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				1	1
PECO Energy Co [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					30	[3]	40		11
PECO Energy Co [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					0		0	[4]	5	[4]
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense					68		66		67
Pension and non-pension postretirement benefit contributions					49		17		16
Expected qualified pension plan contributions				38	38
Service cost	[5]				12		14		8
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year				16	16
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				2	2
Baltimore Gas and Electric Company [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					31	[3]	1		0
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					18		16	[4]	17	[4]
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected qualified pension plan contributions				60	60
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year				12	12
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				8	8
Pepco Holdings LLC [Member] | Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		$ 9			47		37		16
Service cost		1			6		6		6
Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		23					97		58
Pension and non-pension postretirement benefit contributions		4					21		18
Service cost		3					14		13
Pepco Holdings LLC [Member] | Successor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense				88
Pension and non-pension postretirement benefit contributions				86
Service cost				10
Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost					60
Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member] | Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions		4	[3]		17	[3]	0		0
Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions	[3]	4					0		0
Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member] | Successor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions	[3]			74
Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member] | Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					2		0	[4]	0	[4]
Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions	[3]	0					5		4
Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member] | Successor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions	[3]			12
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		7			31		30		22
Pension and non-pension postretirement benefit contributions					32		14		11
Expected qualified pension plan contributions				60	60
Service cost		1			3		3		3
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year				10	10
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				1	1
Potomac Electric Power Company [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					24	[3]	0		0
Potomac Electric Power Company [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					8		2	[4]	1	[4]
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		4			18		15		7
Pension and non-pension postretirement benefit contributions					22		0		0
Expected qualified pension plan contributions				0	0
Service cost		1			2		2		2
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year				0	0
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				0	0
Delmarva Power and Light Company [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					22	[3]	0		0
Delmarva Power and Light Company [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					0		0	[4]	0	[4]
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		$ 3			15		15		13
Pension and non-pension postretirement benefit contributions					17		2		3
Expected qualified pension plan contributions				0	0
Service cost					2		2		1
Defined Other Postretirement Benefit Plan Estimated Future Employer Contributions In Next Fiscal Year				0	0
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months				0	0
Atlantic City Electric Company [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					15	[3]	0		0
Atlantic City Electric Company [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions					2		3	[4]	$ 3	[4]
Constellation Legacy Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and non-pension postretirement benefit contributions	[3]				36		$ 43
Expected qualified pension plan contributions				$ 21	$ 21
Remeasurement [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Design Changes							6.59%
Remeasurement [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Design Changes							4.30%
Remeasurement [Member] | Maximum [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Assumptions Used Calculating Net Periodic Benefit Cost Discount Rate Design Changes					4.43%		4.06%		4.55%
[1]	___(a)These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO, BGE, Pepco, DPL or ACE amounts
[2]	(b)These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These costs are not included in the Generation, ComEd, PECO, or BGE amount
[3]	Includes $6 million, $5 million, and $9 million of pension contributions funded by Exelon Corporate, for the years ended December 31, 2016, 2015, and 2014, respectively.
[4]	_________________________(a)Exelon's and Generation's pension contributions include $25 million, $36 million and $43 million related to the legacy CENG plans that was funded by CENG as provided in an Employee Matters Agreement (EMA) between Exelon and CENG for the years ended December 31, 2016, 2015 and 2014, respectively.
[5]	____(a)Includes $13 million, $9 million and $5 million related to CENG for the years ended December 31, 2016, December 31, 2015 and for the period from April 1, 2014 to December 31, 2014, respe

Retirement Benefits - Estimated

Retirement Benefits - Estimated Future Benefit Payments (Details) $ in Millions	Dec. 31, 2016USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,015	$ 23
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	23
Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,015	1,360
2,016	1,170
2,017	1,191
2,018	1,223
2,019	1,275
2020 through 2024	6,791
Total estimated future benefit payments through 2026	13,010
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	1,360
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,015	244
2,016	250
2,017	256
2,018	263
2,019	272
2020 through 2024	1,456
Total estimated future benefit payments through 2026	2,741
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	$ 244

Retirement Benefits - Allocated

Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense				$ 621	$ 637	$ 561
Exelon Generation Co L L C [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense				218	269	250
Commonwealth Edison Co [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense				166	206	162
PECO Energy Co [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense				33	39	36
Baltimore Gas and Electric Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense				68	66	67
Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense		$ 23			97	58
Pepco Holdings LLC [Member] | Successor [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense			$ 88
Potomac Electric Power Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense		7		31	30	22
Delmarva Power and Light Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense		4		18	15	7
Atlantic City Electric Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense		3		15	15	13
Corporate, Non-Segment [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense	[1]			48	57	46
Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Amount included in capital and operating & maintenance expense		$ 9		$ 47	$ 37	$ 16
[1]	___(a)These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO, BGE, Pepco, DPL or ACE amounts

Retirement Benefits - Pension a

Retirement Benefits - Pension and Other Postretirement Benefit Plan Target Asset Allocations (Details)		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of Plan Assets		100.00%	100.00%
Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of Plan Assets		100.00%	100.00%
Equity Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocation percentage		43.00%
Percentage of Plan Assets		47.00%	43.00%
Equity Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocation percentage		33.00%
Percentage of Plan Assets		33.00%	35.00%
Fixed Income Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocation percentage		28.00%
Percentage of Plan Assets		29.00%	27.00%
Fixed Income Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocation percentage		39.00%
Percentage of Plan Assets		39.00%	34.00%
Alternative Investments [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocation percentage	[1]	29.00%
Percentage of Plan Assets	[1]	24.00%	30.00%
Alternative Investments [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target asset allocation percentage	[1]	28.00%
Percentage of Plan Assets	[1]	28.00%	31.00%
Predecessor [Member] | Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of Plan Assets			100.00%
Predecessor [Member] | Pepco Holdings LLC [Member] | Equity Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of Plan Assets			63.00%
Predecessor [Member] | Pepco Holdings LLC [Member] | Equity Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of Plan Assets			28.00%
Predecessor [Member] | Pepco Holdings LLC [Member] | Fixed Income Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of Plan Assets			34.00%
Predecessor [Member] | Pepco Holdings LLC [Member] | Fixed Income Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of Plan Assets			66.00%
Predecessor [Member] | Pepco Holdings LLC [Member] | Alternative Investments [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of Plan Assets	[1]		3.00%
Predecessor [Member] | Pepco Holdings LLC [Member] | Alternative Investments [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of Plan Assets	[1]		6.00%
[1]	___(a)Alternative investments include private equity, hedge funds, real estate, and private

Retirement Benefits - Fair Valu

Retirement Benefits - Fair Value Measurements of Pension and Postretirement Benefit Plan Assets (Details) - USD ($) $ in Millions		Dec. 31, 2016		Mar. 23, 2016	Dec. 31, 2015		Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Derivative, Fair Value, Net		$ 1			$ 5
Derivative, notional amount		2,918			1,774
Net assets pending transactions excluded		28			(27)
Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		2,578			2,293		$ 2,430
Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		16,791			14,347		14,874
Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		208			167		122
Equity Security Individually Held [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		2			2		2
Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		206			165		120
Fair Value, Measurements, Recurring [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1],[2]	19,397			16,613
Alternative Investments, Fair Value Disclosure		3,113			2,765
Fair Value, Measurements, Recurring [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	2,578			2,291
Alternative Investments, Fair Value Disclosure	[1]	1,444			1,311
Fair Value, Measurements, Recurring [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	16,819			14,322
Alternative Investments, Fair Value Disclosure	[1]	7,897			6,186
Fair Value, Measurements, Recurring [Member] | PensionAndOPEB [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[1],[2]	9,341			7,497
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1],[2]	5,313			5,473
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	836			691
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	4,477			4,782
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1],[2]	4,535			3,476
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	298			289
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	4,237			3,187
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1],[2]	208			167
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	208			167
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	24			15
Alternative Investments, Fair Value Disclosure		0			0	[1]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	325			210
Alternative Investments, Fair Value Disclosure		0	[1]		0
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		24			15	[1]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		325	[1]		210
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		0			0	[1]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		0	[1]		0
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		0			0	[1]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		0	[1]		0
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	1,193			992
Alternative Investments, Fair Value Disclosure		644			480
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	5,681			5,035
Alternative Investments, Fair Value Disclosure		2,535			1,462
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		547			510
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		3,144			3,571
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		2			2
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		0			0
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		0			0
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		2			2
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	68			64
Alternative Investments, Fair Value Disclosure	[1]	0			0
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	1,200			1,080
Alternative Investments, Fair Value Disclosure	[1]	0			0
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	9			11
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	1,008			1,001
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	59			53
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	192			79
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	134			131
Alternative Investments, Fair Value Disclosure	[1]	0			0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	64			61
Alternative Investments, Fair Value Disclosure	[1]	0			0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	134			131
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	64			61
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	43			44
Alternative Investments, Fair Value Disclosure	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	3,847			3,066
Alternative Investments, Fair Value Disclosure	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	43			44
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	3,641			2,901
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	206			165
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	447			360
Alternative Investments, Fair Value Disclosure		131			146	[1]
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	1,088			598
Alternative Investments, Fair Value Disclosure		748	[1]		452
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		256			155	[1]
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		60			59	[1]
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	340			146
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		0			0	[1]
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	692			599
Alternative Investments, Fair Value Disclosure	[1]	131			146
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	6,199			4,805
Alternative Investments, Fair Value Disclosure	[1]	748			452
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	265			166
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	1,008			1,001
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	296			287
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	4,237			3,187
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	206			165
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	991			924
Alternative Investments, Fair Value Disclosure	[1]	991			924
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	445			451
Alternative Investments, Fair Value Disclosure	[1]	445			451
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	1,962			1,924
Alternative Investments, Fair Value Disclosure	[1]	1,962			1,924
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	117			131
Alternative Investments, Fair Value Disclosure		117			131	[1]
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	828			725
Alternative Investments, Fair Value Disclosure	[1]	828			725
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		0			0	[1]
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		0			0	[1]
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets		0			0	[1]
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	107			103
Alternative Investments, Fair Value Disclosure	[1]	107			103
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	833			699
Alternative Investments, Fair Value Disclosure	[1]	833			699
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	0			0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]	$ 0			0
Pepco Holdings LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net assets pending transactions excluded					(9)
Predecessor [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Derivative, Fair Value, Net					18
Predecessor [Member] | Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets				$ 348	348		367
Predecessor [Member] | Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets				$ 2,020	2,018		$ 2,236
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1],[2]				2,357
Alternative Investments, Fair Value Disclosure	[1],[2]				834
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				348
Alternative Investments, Fair Value Disclosure	[1]				22
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				2,009
Alternative Investments, Fair Value Disclosure	[1]				812
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1],[2]				825
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				326
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				499
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1],[2]				698
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				698
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1],[2]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				8
Alternative Investments, Fair Value Disclosure					0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				50
Alternative Investments, Fair Value Disclosure					0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets					8
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets					50
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets					0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets					0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets					0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets					0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				219
Alternative Investments, Fair Value Disclosure					22
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				559
Alternative Investments, Fair Value Disclosure					224
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				121
Alternative Investments, Fair Value Disclosure	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				129
Alternative Investments, Fair Value Disclosure	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				121
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				114
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				15
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				18
Alternative Investments, Fair Value Disclosure	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				18
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				625
Alternative Investments, Fair Value Disclosure	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				625
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				544
Alternative Investments, Fair Value Disclosure	[1]				504
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				40
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				1,316
Alternative Investments, Fair Value Disclosure	[1]				504
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				114
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				698
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				38
Alternative Investments, Fair Value Disclosure	[1]				38
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				46
Alternative Investments, Fair Value Disclosure	[1]				46
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				0
Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Fair Value of Plan Assets	[1]				$ 0
[1]	___(a)See Note 12—Fair Value of Financial Assets and Liabilities for a description of levels within the fair value hi
[2]	ss.(c)Excludes net liabilities of $28 million and net assets of $27 million at December 31, 2016 and 2015, respectively, which are required to reconcile to the fair value of net plan assets. These items consist primarily of receivables related to pending securities sales, interest and dividends receivable, and payables related to pending securities pur

Retirement Benefits - Reconcili

Retirement Benefits - Reconciliation of Level 3 Assets and Liabilities measured at Fair Value for Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		$ 14,347		$ 14,874
Fair value of net plan assets at end of year		16,791		14,347
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		2,293		2,430
Fair value of net plan assets at end of year		2,578		2,293
Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		167		122
Relating to assets still held at the reporting date		(2)		(8)
Defined Benefit Plan Purchases		69		61
Defined Benefit Plan Sales		14
Settlements	[1]	(12)		(8)
Fair value of net plan assets at end of year		208		167
Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		165		120
Relating to assets still held at the reporting date		(2)		(8)
Defined Benefit Plan Purchases		69		61
Defined Benefit Plan Sales		14
Settlements	[1]	(12)		(8)
Fair value of net plan assets at end of year		206		165
Equity Security Individually Held [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		2		2
Relating to assets still held at the reporting date		0		0
Defined Benefit Plan Purchases		0		0
Defined Benefit Plan Sales		0
Settlements	[1]	0		0
Fair value of net plan assets at end of year		2		2
Predecessor [Member] | Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		2,018		2,236
Fair value of net plan assets at end of year				2,018
Predecessor [Member] | Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		348		367
Fair value of net plan assets at end of year				348
Fair Value, Measurements, Recurring [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure		3,113		2,765
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2],[3]	16,613
Fair value of net plan assets at end of year	[2],[3]	19,397		16,613
Fair Value, Measurements, Recurring [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	7,897		6,186
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	14,322
Fair value of net plan assets at end of year	[2]	16,819		14,322
Fair Value, Measurements, Recurring [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	1,444		1,311
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	2,291
Fair value of net plan assets at end of year	[2]	2,578		2,291
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2],[3]	5,473
Fair value of net plan assets at end of year	[2],[3]	5,313		5,473
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	4,782
Fair value of net plan assets at end of year	[2]	4,477		4,782
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	691
Fair value of net plan assets at end of year	[2]	836		691
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2],[3]	3,476
Fair value of net plan assets at end of year	[2],[3]	4,535		3,476
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	3,187
Fair value of net plan assets at end of year	[2]	4,237		3,187
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	289
Fair value of net plan assets at end of year	[2]	298		289
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2],[3]	167
Fair value of net plan assets at end of year	[2],[3]	208		167
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	167
Fair value of net plan assets at end of year	[2]	208		167
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure		0	[2]	0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	210
Fair value of net plan assets at end of year	[2]	325		210
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure		0		0	[2]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	15
Fair value of net plan assets at end of year	[2]	24		15
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		210
Fair value of net plan assets at end of year		325	[2]	210
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	15
Fair value of net plan assets at end of year		24		15	[2]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		0
Fair value of net plan assets at end of year		0	[2]	0
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year		0		0	[2]
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		0
Fair value of net plan assets at end of year		0	[2]	0
Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year		0		0	[2]
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	1,962		1,924
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	1,924
Fair value of net plan assets at end of year	[2]	1,962		1,924
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	445		451
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	451
Fair value of net plan assets at end of year	[2]	445		451
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Hedge Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	991		924
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	924
Fair value of net plan assets at end of year	[2]	991		924
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	828		725
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	725
Fair value of net plan assets at end of year	[2]	828		725
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure		117		131	[2]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	131
Fair value of net plan assets at end of year	[2]	117		131
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year		0		0	[2]
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year		0		0	[2]
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year		0		0	[2]
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	748		452
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	4,805
Fair value of net plan assets at end of year	[2]	6,199		4,805
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	131		146
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	599
Fair value of net plan assets at end of year	[2]	692		599
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	1,001
Fair value of net plan assets at end of year	[2]	1,008		1,001
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	166
Fair value of net plan assets at end of year	[2]	265		166
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	3,187
Fair value of net plan assets at end of year	[2]	4,237		3,187
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	287
Fair value of net plan assets at end of year	[2]	296		287
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	165
Fair value of net plan assets at end of year	[2]	206		165
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	833		699
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	699
Fair value of net plan assets at end of year	[2]	833		699
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	107		103
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	103
Fair value of net plan assets at end of year	[2]	107		103
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Private Placement [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure		2,535		1,462
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	5,035
Fair value of net plan assets at end of year	[2]	5,681		5,035
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure		644		480
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	992
Fair value of net plan assets at end of year	[2]	1,193		992
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		3,571
Fair value of net plan assets at end of year		3,144		3,571
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		510
Fair value of net plan assets at end of year		547		510
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		0
Fair value of net plan assets at end of year		0		0
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		2
Fair value of net plan assets at end of year		2		2
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		2
Fair value of net plan assets at end of year		2		2
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		0
Fair value of net plan assets at end of year		0		0
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	0		0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	1,080
Fair value of net plan assets at end of year	[2]	1,200		1,080
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	0		0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	64
Fair value of net plan assets at end of year	[2]	68		64
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	1,001
Fair value of net plan assets at end of year	[2]	1,008		1,001
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	11
Fair value of net plan assets at end of year	[2]	9		11
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	79
Fair value of net plan assets at end of year	[2]	192		79
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	53
Fair value of net plan assets at end of year	[2]	59		53
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	0		0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	61
Fair value of net plan assets at end of year	[2]	64		61
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	0		0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	131
Fair value of net plan assets at end of year	[2]	134		131
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	61
Fair value of net plan assets at end of year	[2]	64		61
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	131
Fair value of net plan assets at end of year	[2]	134		131
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	0		0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	3,066
Fair value of net plan assets at end of year	[2]	3,847		3,066
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]	0		0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	44
Fair value of net plan assets at end of year	[2]	43		44
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	2,901
Fair value of net plan assets at end of year	[2]	3,641		2,901
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	44
Fair value of net plan assets at end of year	[2]	43		44
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	165
Fair value of net plan assets at end of year	[2]	206		165
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure		748	[2]	452
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	598
Fair value of net plan assets at end of year	[2]	1,088		598
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure		131		146	[2]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	360
Fair value of net plan assets at end of year	[2]	447		360
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	155
Fair value of net plan assets at end of year		256		155	[2]
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	146
Fair value of net plan assets at end of year	[2]	340		146
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	59
Fair value of net plan assets at end of year		60		59	[2]
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]	0		0
Fair Value, Measurements, Recurring [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year		0		0	[2]
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2],[3]			834
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2],[3]	2,357
Fair value of net plan assets at end of year	[2],[3]			2,357
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]			812
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	2,009
Fair value of net plan assets at end of year	[2]			2,009
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]			22
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	348
Fair value of net plan assets at end of year	[2]			348
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2],[3]	825
Fair value of net plan assets at end of year	[2],[3]			825
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	499
Fair value of net plan assets at end of year	[2]			499
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	326
Fair value of net plan assets at end of year	[2]			326
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2],[3]	698
Fair value of net plan assets at end of year	[2],[3]			698
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	698
Fair value of net plan assets at end of year	[2]			698
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2],[3]	0
Fair value of net plan assets at end of year	[2],[3]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure				0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	50
Fair value of net plan assets at end of year	[2]			50
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure				0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	8
Fair value of net plan assets at end of year	[2]			8
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		50
Fair value of net plan assets at end of year				50
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		8
Fair value of net plan assets at end of year				8
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		0
Fair value of net plan assets at end of year				0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		0
Fair value of net plan assets at end of year				0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		0
Fair value of net plan assets at end of year				0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year		0
Fair value of net plan assets at end of year				0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Private Equity Funds [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]			38
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	38
Fair value of net plan assets at end of year	[2]			38
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Private Equity Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Real Estate Funds [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]			46
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	46
Fair value of net plan assets at end of year	[2]			46
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Real Estate Funds [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]			504
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	1,316
Fair value of net plan assets at end of year	[2]			1,316
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	114
Fair value of net plan assets at end of year	[2]			114
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	698
Fair value of net plan assets at end of year	[2]			698
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Equity Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure				224
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	559
Fair value of net plan assets at end of year	[2]			559
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Equity Securities [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure				22
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	219
Fair value of net plan assets at end of year	[2]			219
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Treasury and Government [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]			0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	129
Fair value of net plan assets at end of year	[2]			129
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Treasury and Government [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]			0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	121
Fair value of net plan assets at end of year	[2]			121
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	114
Fair value of net plan assets at end of year	[2]			114
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 1 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	121
Fair value of net plan assets at end of year	[2]			121
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	15
Fair value of net plan assets at end of year	[2]			15
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 2 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Treasury and Government [Member] | Fair Value, Inputs, Level 3 [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Government Agencies Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]			0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	18
Fair value of net plan assets at end of year	[2]			18
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	18
Fair value of net plan assets at end of year	[2]			18
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Corporate Debt Securities [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]			0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	625
Fair value of net plan assets at end of year	[2]			625
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	625
Fair value of net plan assets at end of year	[2]			625
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Other Debt Obligations [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Alternative Investments, Fair Value Disclosure	[2]			504
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	544
Fair value of net plan assets at end of year	[2]			544
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 1 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	0
Fair value of net plan assets at end of year	[2]			0
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 2 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	40
Fair value of net plan assets at end of year	[2]			40
Fair Value, Measurements, Recurring [Member] | Predecessor [Member] | Pepco Holdings LLC [Member] | Other Debt Obligations [Member] | Fair Value, Inputs, Level 3 [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of net plan assets at beginning of year	[2]	$ 0
Fair value of net plan assets at end of year	[2]			$ 0
[1]	___(a)Represents cash settlemen
[2]	___(a)See Note 12—Fair Value of Financial Assets and Liabilities for a description of levels within the fair value hi
[3]	ss.(c)Excludes net liabilities of $28 million and net assets of $27 million at December 31, 2016 and 2015, respectively, which are required to reconcile to the fair value of net plan assets. These items consist primarily of receivables related to pending securities sales, interest and dividends receivable, and payables related to pending securities pur

Retirement Benefits - Summar158

Retirement Benefits - Summary of Defined Contribution Savings Plan (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions				$ 164	$ 148	$ 103
Corporate, Non-Segment [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions	[1]			19	11	10
Exelon Generation Co L L C [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions				79	80	51
Commonwealth Edison Co [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions				34	32	26
PECO Energy Co [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions				10	11	8
Baltimore Gas and Electric Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions	[2]			12	14	8
Pepco Holdings LLC [Member] | Corporate, Non-Segment [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions		$ 1		6	6	6
Potomac Electric Power Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions		1		3	3	3
Delmarva Power and Light Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions		1		2	2	2
Atlantic City Electric Company [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions				$ 2	2	1
CENG [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions					9	5
Successor [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions			$ 10
Predecessor [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Savings plan matching contributions		$ 3			$ 14	$ 13
[1]	(b)These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These costs are not included in the Generation, ComEd, PECO, or BGE amount
[2]	____(a)Includes $13 million, $9 million and $5 million related to CENG for the years ended December 31, 2016, December 31, 2015 and for the period from April 1, 2014 to December 31, 2014, respe

Severance - Narrative (Details)

Severance - Narrative (Details) $ in Millions		1 Months Ended	3 Months Ended	12 Months Ended
		Aug. 31, 2015	Dec. 31, 2016USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 19	$ 18
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			13	$ 15
Exelon Generation Co L L C [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			$ 44
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]			23
Restructuring and Related Cost, Expected Number of Positions Eliminated		500
Cost Management Project [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated		250
Cost Management Project [Member] | Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]			18
Restructuring and Related Cost, Expected Number of Positions Eliminated		250
Cost Management Project [Member] | Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 7
[1]	The amounts above for Generation, ComEd, PECO, BGE and PHI include immaterial amounts billed by BSC for the years ended December 31, 2016 and 2015.
[2]	The amounts above for Generation, ComEd, PECO and BGE include $7 million, $3 million, $1 million, and $1 million, respectively, for amounts billed by BSC through intercompany allocations for the year ended December 31, 2016.

Severance - Ongoing Severance P

Severance - Ongoing Severance Plans (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 19	$ 18
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			13	15
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			3	2
PECO Energy Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			1	0
Baltimore Gas and Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			$ 1	1
Pepco Holdings LLC [Member] | Successor [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		$ 1
Pepco Holdings LLC [Member] | Predecessor [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	$ 0			$ 0
[1]	The amounts above for Generation, ComEd, PECO, BGE and PHI include immaterial amounts billed by BSC for the years ended December 31, 2016 and 2015.

Severance - Cost Management Pro

Severance - Cost Management Program-Related Severance (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 19	$ 18
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	23
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	13	15
Exelon Generation Co L L C [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	18
Exelon Generation Co L L C [Member] | Cost Management Project [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		7
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	3	2
Commonwealth Edison Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	3
Commonwealth Edison Co [Member] | Cost Management Project [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		3
PECO Energy Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1	0
PECO Energy Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1
PECO Energy Co [Member] | Cost Management Project [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1
Baltimore Gas and Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1	$ 1
Baltimore Gas and Electric Company [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1
Baltimore Gas and Electric Company [Member] | Cost Management Project [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 1
[1]	The amounts above for Generation, ComEd, PECO and BGE include $7 million, $3 million, $1 million, and $1 million, respectively, for amounts billed by BSC through intercompany allocations for the year ended December 31, 2016.
[2]	The amounts above for Generation, ComEd, PECO, BGE and PHI include immaterial amounts billed by BSC for the years ended December 31, 2016 and 2015.

Severance - Severance Benefit R

Severance - Severance Benefit Related to the PHI Merger (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Severance Costs			$ 19	$ 18
Regulatory Assets		$ 11,388	11,388	6,824
PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		57
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]		13	15
Exelon Generation Co L L C [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		9
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			8
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]		3	2
Regulatory Assets		1,167	1,167	1,113
Commonwealth Edison Co [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		2
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			2
PECO Energy Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]		1	0
Regulatory Assets		1,710	1,710	1,617
PECO Energy Co [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		1
PECO Energy Co [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1
Baltimore Gas and Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]		1	1
Regulatory Assets		712	712	781
Baltimore Gas and Electric Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		1
Baltimore Gas and Electric Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1
Pepco Holdings LLC [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		20	20
Pepco Holdings LLC [Member] | Successor [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1
Regulatory Assets		3,504	3,504
Pepco Holdings LLC [Member] | Successor [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		44
Potomac Electric Power Company [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		852	852	801
Potomac Electric Power Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1],[3]		21
Regulatory Assets		8	8
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			20
Delmarva Power and Light Company [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		348	348	371
Delmarva Power and Light Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1],[4]		13
Regulatory Assets		4	4
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			12
Atlantic City Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		501	501	$ 512
Atlantic City Electric Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		10
Regulatory Assets		8	8
Atlantic City Electric Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			10
Severance Costs [Member] | Potomac Electric Power Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		11	11
Severance Costs [Member] | Delmarva Power and Light Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		$ 4	$ 4
[1]	The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $8 million, $2 million, $1 million, $1 million, $20 million, $12 million and $10 million, respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the year ended December 31, 2016.
[2]	The amounts above for Generation, ComEd, PECO, BGE and PHI include immaterial amounts billed by BSC for the years ended December 31, 2016 and 2015.
[3]	Pepco established a regulatory asset of $11 million as of December 31, 2016, primarily for severance benefit costs related to the PHI merger.
[4]	DPL established a regulatory asset of $4 million as of December 31, 2016, primarily for severance benefit costs related to the PHI merger.

Severance - Severance Liabiliti

Severance - Severance Liabilities Rollforward (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Beginning Balance		$ 35		$ 35	$ 50
Severance Costs				19	18
Payments				(46)	(31)
Ending Balance			$ 88	88	35
Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			99	16
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance		23		23	34
Severance Costs	[2]			13	15
Payments				(9)	(21)
Ending Balance			36	36	23
Exelon Generation Co L L C [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			22	10
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance		3		3	2
Severance Costs	[2]			3	2
Payments				(2)	(1)
Ending Balance			3	3	3
Commonwealth Edison Co [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			2	2
PECO Energy Co [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance		0		0	0
Severance Costs	[2]			1	0
Payments				0	0
Ending Balance			0	0	0
PECO Energy Co [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			0	0
Baltimore Gas and Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance		1		1	2
Severance Costs	[2]			1	1
Payments				(1)	(1)
Ending Balance			0	0	1
Baltimore Gas and Electric Company [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			0	0
Pepco Holdings LLC [Member] | Successor [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	[3]	0		0	0
Severance Costs	[2]		1
Payments	[3]			(27)	0
Ending Balance	[3]		29	29	0
Pepco Holdings LLC [Member] | Successor [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1],[3]			56	0
Pepco Holdings LLC [Member] | Predecessor [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance	[3]	0		0	3
Severance Costs	[2]	0			0
Payments	[3]				(3)
Ending Balance	[3]				0
Pepco Holdings LLC [Member] | Predecessor [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1],[3]				0
Potomac Electric Power Company [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance		0		0	1
Payments				(1)	(1)
Ending Balance			0	0	0
Potomac Electric Power Company [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			1	0
Delmarva Power and Light Company [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance		0		0	0
Payments				(1)	0
Ending Balance			0	0	0
Delmarva Power and Light Company [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			1	0
Atlantic City Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Beginning Balance		$ 0		0	0
Payments				0	0
Ending Balance			$ 0	0	0
Atlantic City Electric Company [Member] | Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			$ 0	$ 0
[1]	Includes salary continuance and health and welfare severance benefits. Amounts primarily represent benefits provided for the PHI post-merger integration and the cost management program.
[2]	The amounts above for Generation, ComEd, PECO, BGE and PHI include immaterial amounts billed by BSC for the years ended December 31, 2016 and 2015.
[3]	For PHI, the successor period includes activity for the period from March 24, 2016 through December 31, 2016. The PHI predecessor periods include activity for the year ended December 31, 2015 and the period January 1, 2016 through March 23, 2016. There was no activity in the 2016 PHI predecessor period.

Mezzanine Equity Contingent164

Mezzanine Equity Contingently Redeemable Noncontrolling Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Noncontrolling Interest [Line Items]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	18,000
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	$ 396		$ 1,548
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	0	$ 28
Temporary Equity, Other Changes		4	(528)
Payments to Acquire Businesses, Gross	6,934	40	386
Pepco Holdings LLC [Member]
Noncontrolling Interest [Line Items]
Derivative Asset, Not Subject to Master Netting Arrangement	18
Exelon Generation Co L L C [Member]
Noncontrolling Interest [Line Items]
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	396	1	5
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount	0	28	0
Temporary Equity, Accretion to Redemption Value	129	32
Temporary Equity, Other Changes	(157)		(4)
Payments to Acquire Businesses, Gross	$ 293	$ 40	$ 386

Shareholder Equity Schedule of

Shareholder Equity Schedule of Common Stock Authorized and Outstanding (Details) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, shares authorized	2,000,000,000	2,000,000,000
Common Stock, Shares, Outstanding	924,035,059	919,924,742
Commonwealth Edison Co [Member]
Class of Stock [Line Items]
Common Stock, Par or Stated Value Per Share	$ 12.50
Common stock, shares authorized	250,000,000
Common Stock, Shares, Outstanding	127,017,157	127,016,973
PECO Energy Co [Member]
Class of Stock [Line Items]
Common stock, shares authorized	500,000,000
Common Stock, Shares, Outstanding	170,478,507	170,478,507
Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Common stock, shares authorized	175,000,000
Common Stock, Shares, Outstanding	1,000	1,000
Pepco Holdings LLC [Member] | Predecessor [Member]
Class of Stock [Line Items]
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000
Common Stock, Shares, Outstanding		254,289,261
Potomac Electric Power Company [Member]
Class of Stock [Line Items]
Common Stock, Par or Stated Value Per Share	$ 0.01
Common stock, shares authorized	200,000,000
Common Stock, Shares, Outstanding	100	100
Delmarva Power and Light Company [Member]
Class of Stock [Line Items]
Common Stock, Par or Stated Value Per Share	$ 2.25
Common stock, shares authorized	1,000
Common Stock, Shares, Outstanding	1,000	1,000
Atlantic City Electric Company [Member]
Class of Stock [Line Items]
Common Stock, Par or Stated Value Per Share	$ 3
Common stock, shares authorized	25,000,000
Common Stock, Shares, Outstanding	8,546,017	8,546,017

Shareholder Equity Shareholder

Shareholder Equity Shareholder Narrative (Details) $ / shares in Units, $ in Millions	Sep. 18, 2016shares	Jul. 03, 2016shares	Sep. 30, 2016USD ($)shares	Sep. 30, 2016USD ($)shares	Dec. 31, 2016USD ($)warrant$ / sharesshares	Dec. 31, 2015USD ($)warrantshares	Jul. 30, 2015USD ($)$ / sharesshares	Jun. 30, 2014USD ($)$ / sharesshares
Schedule of Capitalization, Equity [Line Items]
Shares Issued, Price Per Share | $ / shares								$ 35
Junior Subordinated Notes, Noncurrent | $								$ 1,150
Treasury stock, at cost | $					$ 2,327	$ 2,327
Treasury Stock, Number of Shares Held					35,000,000	35,000,000
Forward Contract Indexed to Issuer's Equity, Indexed Shares								23,000,000
Sale of Stock, Price Per Share | $ / shares							$ 32.48
Temporary Equity, Share Subscriptions							57,500,000	57,500,000
Preferred Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Preferred Stock, Shares Authorized					100,000,000
Minimum [Member]
Schedule of Capitalization, Equity [Line Items]
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value | $							$ 1,870
Commonwealth Edison Co [Member]
Schedule of Capitalization, Equity [Line Items]
Number Of Warrants Outstanding | warrant					72,859	73,434
Common Stock Shares Reserved For Warrant Conversion					24,286	24,478
Commonwealth Edison Co [Member] | Preferred Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Preferred Stock, Shares Authorized					850,000	6,810,451
Baltimore Gas and Electric Company [Member]
Schedule of Capitalization, Equity [Line Items]
Preferred Stock, Shares Authorized					6,500,000
Stock Redeemed or Called During Period, Shares	500,000	400,000	600,000	400,000
Stock Redeemed or Called During Period, Value | $			$ 100	$ 90
Preferred Stock, Dividend Rate, Percentage	6.97%	7.125%	6.99%	6.70%
Baltimore Gas and Electric Company [Member] | Preferred Stock [Member]
Schedule of Capitalization, Equity [Line Items]
Preferred Stock, Par or Stated Value Per Share | $ / shares					$ 100

Shareholder Equity Preferred an

Shareholder Equity Preferred and Preference Securities (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 0	$ 190
Preferred Stock, Shares Outstanding	0	1,900,000
Pepco Holdings LLC [Member] | Predecessor [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Outstanding		18,000
Series 6.97% Preferred Stock [Member] | Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 0	$ 50
Preferred Stock, Redemption Price Per Share	$ 100
Preferred Stock, Shares Outstanding	0	500,000
Series 6.7% Preferred Stock [Member] | Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 0	$ 40
Preferred Stock, Redemption Price Per Share	$ 100
Preferred Stock, Shares Outstanding	0	400,000
Series 6.99% Preferred Stock [Member] | Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 0	$ 60
Preferred Stock, Redemption Price Per Share	$ 100
Preferred Stock, Shares Outstanding	0	600,000
Series 7.125% Preferred Stock [Member] | Baltimore Gas and Electric Company [Member]
Class of Stock [Line Items]
Preferred Stock, Value, Outstanding	$ 0	$ 40
Preferred Stock, Redemption Price Per Share	$ 100
Preferred Stock, Shares Outstanding	0	400,000

Stock-Based Compensation Pla168

Stock-Based Compensation Plans - Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Common Stock Narrative Information [Line Items]
Classification Of Obligations Related To Outstanding Performance Share Awards Not Yet Settled Deferred Credits And Other Liabilities	[1]		$ 52	$ 32	[2]
Expiration period			10 years
Obligations of outstanding restricted stock not settled			$ 101	97
Settlement of restricted stock			68	75		$ 43
Settlement of performance shares			45	46		27
Settlement of performance shares in cash			28	29		13
Unrecognized compensation costs of performance based shares			$ 51
Weighted-average period of recognition of unrecognized compensation costs of performance based shares			2 years
Pepco Holdings LLC [Member]
Common Stock Narrative Information [Line Items]
Obligations of outstanding restricted stock not settled			$ 1
Settlement of restricted stock				$ 6		8
Settlement of performance shares						$ 3
Performance Shares [Member]
Common Stock Narrative Information [Line Items]
Percentage to be settled as common stock			50.00%
Percentage to be settled as cash			50.00%
Percentage to be settled as cash if ownership requirements are met			100.00%
Weighted average grant date fair value (in usd per share)			$ 28.85	$ 35.88		$ 28.75
Performance Shares [Member] | Pepco Holdings LLC [Member]
Common Stock Narrative Information [Line Items]
Weighted average grant date fair value (in usd per share)				26.10		27.01
Employee Stock Option [Member]
Common Stock Narrative Information [Line Items]
Requisite service period			4 years
Restricted Stock [Member]
Common Stock Narrative Information [Line Items]
Weighted-average period of recognition of unrecognized compensation costs			2 years
Restricted Stock [Member] | Pepco Holdings LLC [Member]
Common Stock Narrative Information [Line Items]
Weighted average grant date fair value (in usd per share)						26.80
Restricted Stock Units (RSUs) [Member]
Common Stock Narrative Information [Line Items]
Weighted average grant date fair value (in usd per share)			$ 28.14	36.55		28.71
Unrecognized compensation costs of performance based shares			$ 58
Restricted Stock Units (RSUs) [Member] | Pepco Holdings LLC [Member]
Common Stock Narrative Information [Line Items]
Weighted average grant date fair value (in usd per share)				27.40		19.77
Restricted Stock Units (RSUs) [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Common Stock Narrative Information [Line Items]
Weighted average grant date fair value (in usd per share)		$ 26.01
Performance based RSU [Member] | Pepco Holdings LLC [Member]
Common Stock Narrative Information [Line Items]
Weighted average grant date fair value (in usd per share)				$ 26.08		$ 18.53
Settlement of restricted stock				$ 15		$ 9
Minimum [Member] | Restricted Stock [Member]
Common Stock Narrative Information [Line Items]
Requisite service period			3 years
Maximum [Member] | Restricted Stock [Member]
Common Stock Narrative Information [Line Items]
Requisite service period			5 years
LTIP [Member]
Common Stock Narrative Information [Line Items]
Shares authorized			14
[1]	Represents the long-term liability related to performance share awards expected to be settled in cash.
[2]	Excludes $8 million of common stock for PHI at December 31, 2015

Stock-Based Compensation Pla169

Stock-Based Compensation Plans - Schedule of Stock-based Compensation Expense (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				$ 175		$ 119		$ 127
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense				(68)		(46)		(47)
Allocated Share-based Compensation Expense, Net of Tax				107		73		80
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				93		41		59
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense				(18)		(18)		(11)
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				75		71		61
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense				(27)		(30)		(17)
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				0		1		2
Stock Compensation Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				7		6		5
Successor [Member] | Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense			$ 4
Predecessor [Member] | Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		$ 3				13		18
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		(1)				(5)		(7)
Allocated Share-based Compensation Expense, Net of Tax		2				8		11
Predecessor [Member] | Pepco Holdings LLC [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		1				5		8
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		0				(5)		(4)
Predecessor [Member] | Pepco Holdings LLC [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		2				7		5
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense		0				(2)		(3)
Predecessor [Member] | Pepco Holdings LLC [Member] | Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		0				1		5
Corporate, Non-Segment [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	[2]			81	[1]	43		60
Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		$ 3		$ 7	[1],[2]	$ 13	[2]	$ 18	[2]
[1]	's stock-based compensation expense for the year ended December 31, 2016 and for the period January 1, 2016 through March 23, 2016 was not material. PHI's stock-based compensation expense for the year ended December 31, 2016 includes $3 million of costs incurred prior to the closing of Exelon’s merger with PHI on March 23, 2016.
[2]	These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO, BGE or PHI amounts above.

Stock-Based Compensation Pla170

Stock-Based Compensation Plans - Schedule of Pre-Tax Stock-based Compensation Expense (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				$ 175		$ 119		$ 127
Exelon Generation Co L L C [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				78		64		52
Commonwealth Edison Co [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				8		6		7
PECO Energy Co [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				3		3		3
Baltimore Gas and Electric Company [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense				1		3		5
Pepco Holdings LLC [Member] | Successor [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense			$ 4
Pepco Holdings LLC [Member] | Predecessor [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		$ 3				13		18
Corporate, Non-Segment [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	[2]			81	[1]	43		60
Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense		$ 3		$ 7	[1],[2]	$ 13	[2]	$ 18	[2]
[1]	's stock-based compensation expense for the year ended December 31, 2016 and for the period January 1, 2016 through March 23, 2016 was not material. PHI's stock-based compensation expense for the year ended December 31, 2016 includes $3 million of costs incurred prior to the closing of Exelon’s merger with PHI on March 23, 2016.
[2]	These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO, BGE or PHI amounts above.

Stock-Based Compensation Pla171

Stock-Based Compensation Plans - Components of Tax Benefits from Stock-based Compensation (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Tax benefit on stock compensation		$ 68	$ 46	$ 47
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options		18	3	(8)
Restricted Stock Units (RSUs) [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Tax benefit on stock compensation		27	30	17
Performance Shares [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Tax benefit on stock compensation		$ 18	18	11
Pepco Holdings LLC [Member] | Predecessor [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Tax benefit on stock compensation	$ 1		5	7
Pepco Holdings LLC [Member] | Predecessor [Member] | Restricted Stock Units (RSUs) [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Tax benefit on stock compensation	0		2	3
Pepco Holdings LLC [Member] | Predecessor [Member] | Performance Shares [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Tax benefit on stock compensation	0		5	4
Pepco Holdings LLC [Member] | Predecessor [Member] | Employee Stock Option [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	$ 0		$ 0	$ 1

Stock-Based Compensation Pla172

Stock-Based Compensation Plans - Summary of Stock Option Activity (Details) - Employee Stock Option [Member] - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
December 31, 2015		15,572,757
Options exercised		(840,672)
Options forfeited		0
Options expired		(2,200,494)
December 31, 2016		12,531,591
Weighted Average Exercise Price (in usd per share)		$ 46.23	$ 46.68
Options Reinstated, Weighted Average Exercise Price (in usd per share)		22.12
Options Forfeited, Weighted Average Exercise Price (in usd per share)		0
Options Expired, Weighted Average Exercise Price (in usd per share)		$ 58.60
Shares Outstanding, Weighted Average Remaining Contractual Life		3 years 6 months
Exercisable at December 31, 2014	[1]	12,531,591
Shares Exercisable, Weighted Average Exercise Price (in usd per share)	[1]	$ 46.23
Shares Exercisable, Weighted Average Remaining Contractual Life	[1]	3 years 6 months
Shares Exercisable, Aggregate Intrinsic Value	[1]	$ 13
[1]	Includes stock options issued to retirement eligible employees.

Stock-Based Compensation Pla173

Stock-Based Compensation Plans - Summary of Information of Stock Options Exercised (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock [Abstract]
Aggregate value	[1]	$ 11	$ 0	$ 3
Cash received for exercise price		$ 19	$ 0	$ 7
[1]	Includes stock options issued to retirement eligible employees.

Stock-Based Compensation Pla174

Stock-Based Compensation Plans - Summary of Nonvested Stock Option Activity (Details) - $ / shares		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Fully Vested Stock Based Compensation Issued To Retirement Eligible Employees		1,319,372	975,116
Nonvested Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance	[1]	82,250
Vested		(82,250)
Ending Balance	[1]	0
Nonvested, Weighted Average Exercise Price (in usd per share)	[1]	$ 0	$ 39.81
Vested, Weighted Average Exercise Price (in usd per share)		$ 39.81
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number			279,000
[1]	Excludes 279,000 of stock options issued to retirement-eligible employees as of December 31, 2015 as they are fully vested.

Stock-Based Compensation Pla175

Stock-Based Compensation Plans - Summary of Nonvested Restrict Stock Unit Activity (Details) - $ / shares		3 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance	[1]	3,563,254	3,563,254
Granted			3,042,184
Vested			(1,797,536)
Forfeited			(85,940)
Undistributed vested awards			(897,546)
Ending Balance	[1]		3,824,416	3,563,254
Nonvested, Weighted Average Exercise Price (in usd per share)	[1]	$ 32.92	$ 32.92
Granted, Weighted Average Grant Date Fair Value (in usd per share)			28.14	$ 36.55	$ 28.71
Vested, Weighted Average Exercise Price (in usd per share)			32.44
Forfeited, Weighted Average Exercise Price (in usd per share)			30.08
Undistributed Vested Awards, Weighted Average Grant Date Fair Value (in usd per share)			28.35
Nonvested, Weighted Average Exercise Price (in usd per share)	[1]		$ 30.49	$ 32.92
Restricted Stock Units (RSUs) [Member] | Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance		628,514	628,514
Ending Balance				628,514
Nonvested, Weighted Average Exercise Price (in usd per share)		$ 24.71	$ 24.71
Granted, Weighted Average Grant Date Fair Value (in usd per share)				$ 27.40	19.77
Nonvested, Weighted Average Exercise Price (in usd per share)		$ 24.96		$ 24.71
Restricted Stock Units (RSUs) [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted		152,928
Vested		0
Forfeited		0
Ending Balance		781,442
Granted, Weighted Average Grant Date Fair Value (in usd per share)		$ 26.01
Vested, Weighted Average Exercise Price (in usd per share)		0
Forfeited, Weighted Average Exercise Price (in usd per share)		$ 0
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Fully Vested Stock Based Compensation Issued To Retirement Eligible Employees			1,319,372	975,116
Restricted Stock [Member] | Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted, Weighted Average Grant Date Fair Value (in usd per share)					$ 26.80
Restricted Stock [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance	[2]	54,165	54,165
Vested		0
Ending Balance	[2]	54,165		54,165
Nonvested, Weighted Average Exercise Price (in usd per share)	[2]	$ 26.80	$ 26.80
Vested, Weighted Average Exercise Price (in usd per share)		0
Nonvested, Weighted Average Exercise Price (in usd per share)	[2]	$ 26.80		$ 26.80
PerformancebasedRSU1 [Member] | Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance		408,638	408,638
Ending Balance				408,638
Nonvested, Weighted Average Exercise Price (in usd per share)		$ 18.56	$ 18.56
Nonvested, Weighted Average Exercise Price (in usd per share)		$ 21.45		$ 18.56
PerformancebasedRSU1 [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted		305,856
Vested		4,950
Forfeited		1,238
Ending Balance		708,306
Granted, Weighted Average Grant Date Fair Value (in usd per share)		$ 25.41
Vested, Weighted Average Exercise Price (in usd per share)		26.08
Forfeited, Weighted Average Exercise Price (in usd per share)		$ 26.08
[1]	Excludes 1,319,372 and 975,116 of restricted stock units issued to retirement-eligible employees as of December 31, 2016 and 2015, respectively, as they are fully vested.
[2]	Excludes 2,443,409 and 1,817,883 of performance share awards issued to retirement-eligible employees as of December 31, 2016 and 2015, respectively, as they are fully vested.

Stock-Based Compensation Pla176

Stock-Based Compensation Plans - Summary of Nonvested Performance Share Awards Activity (Details) - $ / shares		3 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance	[1]	2,557,159	2,557,159
Granted			2,319,407
Vested			(949,315)
Forfeited			(70,876)
Undistributed vested awards	[2]		(1,367,417)
Ending Balance	[1]		3,116,261	2,557,159
Nonvested, Weighted Average Exercise Price (in usd per share)	[1]		$ 30.77	$ 31.88
Granted, Weighted Average Grant Date Fair Value (in usd per share)			$ 28.85	$ 35.88	$ 28.75
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Period Increase (Decrease)			627,303
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Change in Performance, Weighted Average Grant Date Fair Value			$ 30.04
Vested, Weighted Average Exercise Price (in usd per share)			31.31
Forfeited, Weighted Average Exercise Price (in usd per share)			30.90
Undistributed Vested Awards, Weighted Average Grant Date Fair Value (in usd per share)	[2]		$ 28.33
Fully Vested Stock Based Compensation Issued To Retirement Eligible Employees			2,443,409	1,817,883
Performance Shares [Member] | Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted, Weighted Average Grant Date Fair Value (in usd per share)				$ 26.10	27.01
Performance Shares [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance	[1]	24,717	24,717
Vested		(24,717)
Ending Balance	[1]	0		24,717
Nonvested, Weighted Average Exercise Price (in usd per share)	[1]	$ 0		$ 26.10
Vested, Weighted Average Exercise Price (in usd per share)		$ 26.10
PerformancebasedRSU1 [Member] | Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance		408,638	408,638
Ending Balance				408,638
Nonvested, Weighted Average Exercise Price (in usd per share)		$ 21.45		$ 18.56
PerformancebasedRSU1 [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted		305,856
Vested		4,950
Forfeited		1,238
Ending Balance		708,306
Granted, Weighted Average Grant Date Fair Value (in usd per share)		$ 25.41
Vested, Weighted Average Exercise Price (in usd per share)		26.08
Forfeited, Weighted Average Exercise Price (in usd per share)		$ 26.08
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Fully Vested Stock Based Compensation Issued To Retirement Eligible Employees			1,319,372	975,116
Restricted Stock [Member] | Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Granted, Weighted Average Grant Date Fair Value (in usd per share)					$ 26.80
Restricted Stock [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning Balance	[1]	54,165	54,165
Vested		0
Ending Balance	[1]	54,165		54,165
Nonvested, Weighted Average Exercise Price (in usd per share)	[1]	$ 26.80		$ 26.80
Vested, Weighted Average Exercise Price (in usd per share)		$ 0
[1]	Excludes 2,443,409 and 1,817,883 of performance share awards issued to retirement-eligible employees as of December 31, 2016 and 2015, respectively, as they are fully vested.
[2]	Represents performance share awards that vested but were not distributed to retirement-eligible employees during 2016.

Stock-Based Compensation Pla177

Stock-Based Compensation Plans - Balance Sheet Classification of Obligations related to Outstanding Performance Share Awards Not Yet Settled (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Current liabilities	[1]	$ 49	$ 28	[2]
Deferred credits and other liabilities	[3]	52	32	[2]
Common stock		40	35	[2]
Total		$ 141	95	[2]
Pepco Holdings LLC [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock			$ 8
[1]	Represents the current liability related to performance share awards expected to be settled in cash.
[2]	Excludes $8 million of common stock for PHI at December 31, 2015
[3]	Represents the long-term liability related to performance share awards expected to be settled in cash.

Earnings Per Share and Equity -

Earnings Per Share and Equity - Schedule of Earnings per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 204	$ 490	$ 267	$ 173	$ 309	$ 629	$ 638	$ 693	$ 1,134	$ 2,269	$ 1,623
Weighted average common shares outstanding—basic	925	925	924	923	921	913	863	862	924	890	860
Assumed exercise and/or distributions of stock-based awards									3	3	4
Weighted average common shares outstanding—diluted	928	927	926	925	924	915	866	867	927	893	864

Earnings Per Share and Equit179

Earnings Per Share and Equity - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock options not included in the calculation of diluted common shares outstanding (less than 1 million related to PHI merger)	12,000,000	16,000,000	17,000,000
Treasury Stock, Shares held	35,000,000	35,000,000
Treasury stock, at cost	$ 2,327	$ 2,327
Pepco Holdings [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock options not included in the calculation of diluted common shares outstanding (less than 1 million related to PHI merger)		3,000,000	1,000,000

Changes in Accumulated Other180

Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			$ 27,612	$ 27,294		$ 24,133		$ 22,940
OCI before reclassifications			186	136	[1]
Amounts reclassified from AOCI	[2]		150	196	[1],[3]
Other comprehensive income (loss)			(36)	60	[1]	(644)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(17)	(19)	[1]	(28)	[1]
OCI before reclassifications			6	12	[1]
Amounts reclassified from AOCI			8	21	[1],[3]
Other comprehensive income (loss)			2	9	[1]
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			4	3	[1]	3
OCI before reclassifications			(1)
Other comprehensive income (loss)			1
Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(2,610)	(2,565)	[1]	(2,640)
OCI before reclassifications			182	100	[1]
Amounts reclassified from AOCI			137	175	[1],[2],[3]
Other comprehensive income (loss)			(45)	75	[1]
Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(30)	(40)	[1]	(19)
OCI before reclassifications			(5)	21
Amounts reclassified from AOCI			5
Other comprehensive income (loss)			10	(21)	[1]
Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(7)	(3)	[1]
OCI before reclassifications			4	3	[1]
Other comprehensive income (loss)			(4)	(3)	[1]
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(2,660)	(2,624)		(2,684)
Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications			4	32	[1]
Amounts reclassified from AOCI	[2]		13	5	[1],[3]
Other comprehensive income (loss)			9	(27)	[1]	(250)
Exelon Generation Co L L C [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(19)	(21)	[1]	(18)	[1]
OCI before reclassifications			6	8	[1]
Amounts reclassified from AOCI			8	5	[1],[3]
Other comprehensive income (loss)			2	(3)	[1]
Exelon Generation Co L L C [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			2	1	[1]	1	[1]
OCI before reclassifications			(1)
Other comprehensive income (loss)			1
Exelon Generation Co L L C [Member] | Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(30)	(40)	[1]	(19)
OCI before reclassifications			(5)	21	[1]
Amounts reclassified from AOCI			5
Other comprehensive income (loss)			10	(21)	[1]
Exelon Generation Co L L C [Member] | Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(7)	(3)	[1]
OCI before reclassifications			4	3	[1]
Other comprehensive income (loss)			(4)	(3)	[1]
Exelon Generation Co L L C [Member] | AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			(54)	(63)		(36)
PECO Energy Co [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			1	1	[1]	1	[1]
PECO Energy Co [Member] | AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest			$ 1	1		1
Predecessor [Member] | Pepco Holdings LLC [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1],[3]			(5)
Amounts reclassified from AOCI	[2]	$ 1		5	[1],[3]
Other comprehensive income (loss)		1		10	[1]	(12)
Predecessor [Member] | Pepco Holdings LLC [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(8)		(8)	[1]	(9)	[1]
Amounts reclassified from AOCI	[1]			1
Other comprehensive income (loss)	[1]			1
Predecessor [Member] | Pepco Holdings LLC [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(27)		(28)	[1]	(37)	[1]
OCI before reclassifications	[1]			(5)
Amounts reclassified from AOCI		1		4	[1],[2],[3]
Other comprehensive income (loss)		1		9	[1]
Predecessor [Member] | Pepco Holdings LLC [Member] | AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		$ (35)		$ (36)		$ (46)
[1]	All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.
[2]	Amounts in parenthesis represent a decrease in net income.
[3]	See next tables for details about these reclassifications.

Changes in Accumulated Other181

Changes in Accumulated Other Comprehensive Income - Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended										12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Mar. 23, 2016		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues		$ 7,875	$ 9,002	$ 6,910	$ 7,573			$ 6,702	$ 7,401	$ 6,514	$ 8,830	$ 31,360		$ 29,447		$ 27,429
Interest expense												(1,123)		(1,079)		(610)
Other Nonoperating Income (Expense)												413		(46)		455
Income before income taxes												1,989		3,330		2,486
Income tax benefit (expense)												(761)		(1,073)		(666)
Net income												1,204		2,250		1,820
Net Income (Loss) Available to Common Stockholders, Basic		204	490	267	173			309	629	638	693	1,134		2,269		1,623
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]											(150)		(196)	[2],[3]
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax												(8)		(21)	[2],[3]
Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax												(137)		(175)	[1],[2],[3]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]											(224)		(287)
Reclassification from AOCI, Current Period, Tax	[1]											(87)		(112)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1],[4]											78		74
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]											(302)	[4]	(361)	[5]
Accumulated Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax												(5)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before income taxes	[1]											(13)		(35)
Income tax benefit (expense)	[1]											5		14
Net income	[1]											(8)		(21)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues	[1]													2
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense	[1]											(13)		(11)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Interest Rate Swap [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense	[1]													(26)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues	[1]											(5)
Interest expense	[1]					$ 0						0
Income tax benefit (expense)	[1]											0
Net income	[1]											(5)
Exelon Generation Co L L C [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues		$ 4,388	$ 5,035	$ 3,589	$ 4,739			4,294	4,768	4,232	5,840	17,751		19,135		17,393
Interest expense												37		(425)		50
Other Nonoperating Income (Expense)												401		(60)		406
Income tax benefit (expense)												(290)		(502)		(207)
Net income												558		1,340		1,019
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]											(13)		(5)	[2],[3]
Exelon Generation Co L L C [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax												(8)		(5)	[2],[3]
Exelon Generation Co L L C [Member] | Accumulated Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax												(5)
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before income taxes	[1]											(13)		(9)
Income tax benefit (expense)												5	[1]	(4)
Net income	[1]											(8)		(5)
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues	[1]													2
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense												(13)	[1]	(11)
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues	[1]											(5)
Income before income taxes	[1]											(5)
Income tax benefit (expense)	[1]											0
Net income	[1]											(5)
Pension Plan, Defined Benefit [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net income	[1]											$ (137)
Predecessor [Member] | Pepco Holdings LLC [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues						1,153		$ 1,126	$ 1,336	$ 1,119	$ 1,354			4,935		4,808
Interest expense						(69)								(192)		(225)
Other Nonoperating Income (Expense)						(4)								88		44
Income tax benefit (expense)						(17)								(163)		(138)
Net income						19								327		$ 242
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]					(1)								(5)	[2],[3]
Predecessor [Member] | Pepco Holdings LLC [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[2]													(1)
Predecessor [Member] | Pepco Holdings LLC [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax						(1)								(4)	[1],[2],[3]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]					(1)								(6)
Reclassification from AOCI, Current Period, Tax	[1]					0								(2)
Predecessor [Member] | Pepco Holdings LLC [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1],[4]					0								0
Predecessor [Member] | Pepco Holdings LLC [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1],[4]					(1)								(6)
Predecessor [Member] | Pepco Holdings LLC [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income before income taxes	[1]					0								(1)
Income tax benefit (expense)	[1]					0								0
Net income	[1]					0								(1)
Predecessor [Member] | Pepco Holdings LLC [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues	[1]													0
Predecessor [Member] | Pepco Holdings LLC [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest expense						0	[1]							$ (1)
Predecessor [Member] | Pepco Holdings LLC [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Translation Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenues	[1]					0
Interest expense	[1]					0
Income before income taxes	[1]					0
Income tax benefit (expense)	[1]					0
Net income	[1]					0
Predecessor [Member] | Pension Plan, Defined Benefit [Member] | Pepco Holdings LLC [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net income	[1]					$ (1)
[1]	Amounts in parenthesis represent a decrease in net income.
[2]	All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.
[3]	See next tables for details about these reclassifications.
[4]	This accumulated other comprehensive income component is included in the computation of net periodic pension and OPEB cost (see Note 17 — Retirement Benefits for additional details).
[5]	Amortization of the deferred compensation unit plan is allocated to capital and operating and maintenance expense.

Changes in Accumulated Other182

Changes in Accumulated Other Comprehensive Income - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in unrealized gain (loss) on cash flow hedges, taxes		$ 0	$ (6)	$ 96
Change in unrealized gain (loss) on equity investments taxes		3	1	73
Other comprehensive income, income taxes		30	(53)	412
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income, income taxes		30	30	19
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income, income taxes		118	140	93
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income, income taxes		115	62	317
Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in unrealized gain (loss) on cash flow hedges, taxes		(2)	2	84
Change in unrealized gain (loss) on equity investments taxes		3	1	73
Other comprehensive income, income taxes		$ 1	3	157
Predecessor [Member] | Pepco Holdings LLC [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income, income taxes	$ 0		$ 6	$ 5

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	3 Months Ended			12 Months Ended
	Dec. 31, 2016USD ($)aMGPSiteOpen_claimMW	Sep. 30, 2016USD ($)	Sep. 30, 2015gal	Dec. 31, 2016USD ($)aMGPSiteOpen_claimCustomerMW	Dec. 31, 2015USD ($)	Dec. 31, 1999Principle_responsible_party	Dec. 31, 2014USD ($)	May 30, 2012USD ($)
Commitments and Contingencies [Line Items]
Power Volume | MW				220
Loss Contingency Accrual, Payments	$ 44,000,000
Litigation Settlement, Amount				$ (28,000,000)
Nuclear insurance liability limit per incident					$ 21,000,000
BusinessAcquisitionResidualcommitment | MW	55
Loss Contingency, Loss in Period	$ 50,000,000
Guarantee obligations maximum exposure	50,000,000			50,000,000
Asbestos liability reserve	83,000,000			83,000,000	95,000,000
Probable contingency (liability)	$ 22,000,000			$ 22,000,000
Open asbestos liability claims | Open_claim	230			230
Asbestos liability reserve related to anticipated claims	$ 61,000,000			$ 61,000,000
Rossville ash site [Member]
Commitments and Contingencies [Line Items]
Area of property | a	32			32
Exelon Generation Co L L C [Member]
Commitments and Contingencies [Line Items]
Loss Contingency Accrual	$ 0			$ 0
Loss Contingency, Damages Sought, Value				14,000,000
Nuclear financial protection pool value	450,000,000			450,000,000
Maximum recovery limit from a nuclear industry mutual insurance company in the event of multiple losses	13,000,000,000			13,000,000,000
Maximum annual assessment payment mandated by Price-Anderson Act for a nuclear incident	2,700,000,000			2,700,000,000
Total retrospective premium obligation under insurance from a nuclear industry mutual insurance company	353,000,000			353,000,000
Mutual Replacement Power Cost Insurance Maximum Retrospective Premium Obligation	3,200,000,000			3,200,000,000
Cost of spent nuclear fuel disposal per kWh of net nuclear generation	0.001			0.001
Net nuclear fuel disposal fees					49,000,000
Department of Energy SNF one-time fee applicable to nuclear generation	277,000,000			277,000,000
DOE SNF one-time fee with interest	1,024,000,000			$ 1,024,000,000
13-week Treasury Rate used to calculate DOE SNF one-time fee				0.355%
Environmental loss contingencies					$ 90,000,000
Total cost of remediation to be shared by PRPs				$ 90,000,000
Estimate of possible loss	$ 4,000,000			$ 4,000,000
Open asbestos liability claims | Open_claim	300			300
Costs Incurred, Development Costs				$ 454,000,000
Exelon Generation Co L L C [Member] | Minimum [Member]
Commitments and Contingencies [Line Items]
Total cost of remediation to be shared by PRPs	$ 225
Business Acquisition, Development Of New Generation Cost	450,000,000			$ 450,000,000
Business Acquisition, Expected New Generation Mwh | MW				285
Exelon Generation Co L L C [Member] | Maximum [Member]
Commitments and Contingencies [Line Items]
Total cost of remediation to be shared by PRPs	650
Business Acquisition, Development Of New Generation Cost	500,000,000			$ 500,000,000
Business Acquisition, Expected New Generation Mwh | MW				300
Exelon Generation Co L L C [Member] | Equity Method Investments [Member]
Commitments and Contingencies [Line Items]
Purchase obligations, due within two years	5,000,000			$ 5,000,000
Unrecorded Unconditional Purchase Obligation	39,000,000			39,000,000
Unrecorded unconditional purchase obligation, due in next 12 months	34,000,000			34,000,000
Other unrecorded amounts	20,000,000			20,000,000
Exelon Generation Co L L C [Member] | Nuclear Insurance Premiums [Member]
Commitments and Contingencies [Line Items]
Nuclear insurance liability limit per incident	13,400,000,000			13,400,000,000
Exelon Generation Co L L C [Member] | Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]
Commitments and Contingencies [Line Items]
Mutual Property Insurance Distribution To Members	$ 21,000,000			$ 21,000,000			$ 18,000,000
Commonwealth Edison Co [Member]
Commitments and Contingencies [Line Items]
Total number of MGP sites | MGPSite	42			42
Sites approved for clean-up | MGPSite	18			18
Sites under study/remediation | MGPSite	24			24
Increase (decrease) in accrual for environmental loss contingencies		$ 7,000,000
Minimum number of customers ComEd can be held liable to for power interruption | Customer				30,000
PECO Energy Co [Member]
Commitments and Contingencies [Line Items]
Total number of MGP sites | MGPSite	26			26
Sites approved for clean-up | MGPSite	17			17
Sites under study/remediation | MGPSite	9			9
Increase (decrease) in accrual for environmental loss contingencies		0
Baltimore Gas and Electric Company [Member]
Commitments and Contingencies [Line Items]
Litigation Settlement, Amount				$ (28,000,000)
Total number of MGP sites | MGPSite	13			13
Sites under study/remediation | MGPSite	2			2
Number of parties jointly and severally liable In environmental protection agency action | Principle_responsible_party						19
Baltimore Gas and Electric Company [Member] | Deferrable Interest Subordinated Debentures [Member]
Commitments and Contingencies [Line Items]
Interest rate on long-term debt	6.20%			6.20%
Baltimore Gas and Electric Company [Member] | Minimum [Member]
Commitments and Contingencies [Line Items]
Estimate of possible loss	$ 50,000,000			$ 50,000,000
Baltimore Gas and Electric Company [Member] | Maximum [Member]
Commitments and Contingencies [Line Items]
Estimate of possible loss	64,000,000			64,000,000				$ 1,700,000
Calpine Corporation [Member] | Maximum [Member]
Commitments and Contingencies [Line Items]
Estimate of possible loss	$ 10,000,000			10,000,000
Pepco Holdings LLC [Member]
Commitments and Contingencies [Line Items]
Litigation Settlement, Amount				$ 1,600,000
Number of Real Estate Properties | MGPSite	9			9
Pepco Holdings LLC [Member] | Minimum [Member]
Commitments and Contingencies [Line Items]
Estimate of possible loss	$ 7,000,000			$ 7,000,000
Pepco Holdings LLC [Member] | Maximum [Member]
Commitments and Contingencies [Line Items]
Estimate of possible loss	$ 18,000,000			18,000,000
Potomac Electric Power Company [Member]
Commitments and Contingencies [Line Items]
Guarantee obligations maximum exposure		14,000,000
QuantityOfMineralOilSPill | gal			6,100
Quantity of Mineral Oil Spill Recovered			80.00%
Potomac Electric Power Company [Member] | Minimum [Member]
Commitments and Contingencies [Line Items]
Environmental Exit Costs, Anticipated Cost				3,000,000
Potomac Electric Power Company [Member] | Maximum [Member]
Commitments and Contingencies [Line Items]
Environmental Exit Costs, Anticipated Cost				$ 6,000,000
Delmarva Power and Light Company [Member]
Commitments and Contingencies [Line Items]
Total number of MGP sites | MGPSite	2			2
Guarantee obligations maximum exposure		17,000,000
Atlantic City Electric Company [Member]
Commitments and Contingencies [Line Items]
Guarantee obligations maximum exposure		$ 13,000,000
Merger Commitment [Member]
Commitments and Contingencies [Line Items]
Investments	$ 0			$ 0
Merger Commitment [Member] | Minimum [Member]
Commitments and Contingencies [Line Items]
Investments	0			0
Merger Commitment [Member] | Maximum [Member]
Commitments and Contingencies [Line Items]
Investments	$ 0			$ 0

Commitments and Contingencie184

Commitments and Contingencies - Schedule of Government Agreement Settlements (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Schedule of Government Agreements [Line Items]
Nontrade Receivables, Current		$ 109	$ 76
Nontrade Receivables, Noncurrent		15	14
Accounts Payable, Other, Current		(13)	$ (5)
Exelon Generation Co L L C [Member]
Schedule of Government Agreements [Line Items]
Spent Nuclear Fuel Storage Reimbursement		1,038
Spent Nuclear Fuel Storage Reimbursement Net Co Owners		$ 887
Department of Energy [Member] | Exelon Generation Co L L C [Member]
Schedule of Government Agreements [Line Items]
Spent Nuclear Fuel Storage Reimbursement	$ 53
Spent Nuclear Fuel Storage Reimbursement Net Co Owners	$ 49

Commitments and Contingencie185

Commitments and Contingencies - Schedule of Energy Supply Procurement, Curtailment Services, REC and AEC Purchase Commitments (Details)	12 Months Ended
	Dec. 31, 2016
Commonwealth Edison Co [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Term of contract	20 years

Commitments and Contingencie186

Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions		12 Months Ended
		Dec. 31, 2016USD ($)MW	Sep. 30, 2016USD ($)
Guarantor Obligations [Line Items]
Contractual Obligation		$ 3,297
Contractual Obligation, Due in Next Fiscal Year		2,333
Contractual Obligation, Due after Fifth Year		648
Contractual Obligation, Due in Fifth Year		6
Contractual Obligation, Due in Fourth Year		29
Contractual Obligation, Due in Third Year		2
Contractual Obligation, Due in Second Year		279
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		263
Contractual Obligation, Due in Next Fiscal Year		12
Contractual Obligation, Due after Fifth Year		250
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		1
PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		210
Contractual Obligation, Due in Next Fiscal Year		32
Contractual Obligation, Due after Fifth Year		178
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		0
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		225
Contractual Obligation, Due in Next Fiscal Year		23
Contractual Obligation, Due after Fifth Year		200
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		2
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[1]	2,491
Contractual Obligation, Due in Next Fiscal Year	[1]	2,205
Contractual Obligation, Due after Fifth Year	[1]	0
Contractual Obligation, Due in Fifth Year	[1]	0
Contractual Obligation, Due in Fourth Year	[1]	13
Contractual Obligation, Due in Third Year	[1]	0
Contractual Obligation, Due in Second Year	[1]	273
Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		37
Contractual Obligation, Due in Next Fiscal Year		15
Contractual Obligation, Due after Fifth Year		20
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		2
Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		15
Contractual Obligation, Due in Next Fiscal Year		9
Contractual Obligation, Due after Fifth Year		6
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		0
Delmarva Power and Light Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		11
Contractual Obligation, Due in Next Fiscal Year		3
Contractual Obligation, Due after Fifth Year		7
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		1
Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation		9
Contractual Obligation, Due in Next Fiscal Year		3
Contractual Obligation, Due after Fifth Year		5
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		1
Surety Bond [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[2]	1,035
Contractual Obligation, Due in Next Fiscal Year	[2]	978
Contractual Obligation, Due after Fifth Year	[2]	0
Contractual Obligation, Due in Fifth Year	[2]	6
Contractual Obligation, Due in Fourth Year	[2]	16
Contractual Obligation, Due in Third Year	[2]	2
Contractual Obligation, Due in Second Year	[2]	33
Surety Bond [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[3]	11
Contractual Obligation, Due in Next Fiscal Year	[3]	10
Contractual Obligation, Due after Fifth Year	[3]	0
Contractual Obligation, Due in Fifth Year	[3]	0
Contractual Obligation, Due in Fourth Year	[3]	0
Contractual Obligation, Due in Third Year	[3]	0
Contractual Obligation, Due in Second Year	[3]	1
Surety Bond [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[4]	9
Contractual Obligation, Due in Next Fiscal Year	[4]	9
Contractual Obligation, Due after Fifth Year	[4]	0
Contractual Obligation, Due in Fifth Year	[4]	0
Contractual Obligation, Due in Fourth Year	[4]	0
Contractual Obligation, Due in Third Year	[4]	0
Contractual Obligation, Due in Second Year	[4]	0
Surety Bond [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[5]	11
Contractual Obligation, Due in Next Fiscal Year	[5]	9
Contractual Obligation, Due after Fifth Year	[5]	0
Contractual Obligation, Due in Fifth Year	[5]	0
Contractual Obligation, Due in Fourth Year	[5]	0
Contractual Obligation, Due in Third Year	[5]
Contractual Obligation, Due in Second Year	[5]	2
Surety Bond [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[1]	945
Contractual Obligation, Due in Next Fiscal Year	[1]	918
Contractual Obligation, Due after Fifth Year	[1]	0
Contractual Obligation, Due in Fifth Year	[1]	0
Contractual Obligation, Due in Fourth Year	[1]	0
Contractual Obligation, Due in Third Year	[1]	0
Contractual Obligation, Due in Second Year	[1]	27
Surety Bond [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[6]	16
Contractual Obligation, Due in Next Fiscal Year	[6]	14
Contractual Obligation, Due after Fifth Year	[6]	0
Contractual Obligation, Due in Fifth Year	[6]	0
Contractual Obligation, Due in Fourth Year	[6]	0
Contractual Obligation, Due in Third Year	[6]	0
Contractual Obligation, Due in Second Year	[6]	2
Surety Bond [Member] | Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[7]	9
Contractual Obligation, Due in Next Fiscal Year	[7]	9
Contractual Obligation, Due after Fifth Year	[7]	0
Contractual Obligation, Due in Fifth Year	[7]	0
Contractual Obligation, Due in Fourth Year	[7]	0
Contractual Obligation, Due in Third Year	[7]	0
Contractual Obligation, Due in Second Year	[7]	0
Surety Bond [Member] | Delmarva Power and Light Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[8]	4
Contractual Obligation, Due in Next Fiscal Year	[8]	3
Contractual Obligation, Due after Fifth Year	[8]	0
Contractual Obligation, Due in Fifth Year	[8]	0
Contractual Obligation, Due in Fourth Year	[8]	0
Contractual Obligation, Due in Third Year	[8]	0
Contractual Obligation, Due in Second Year	[8]	1
Surety Bond [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[9]	3
Contractual Obligation, Due in Next Fiscal Year	[9]	2
Contractual Obligation, Due after Fifth Year	[9]	0
Contractual Obligation, Due in Fifth Year	[9]	0
Contractual Obligation, Due in Fourth Year	[9]	0
Contractual Obligation, Due in Third Year	[9]	0
Contractual Obligation, Due in Second Year	[9]	1
Trust Preferred Securities [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[10]	628
Contractual Obligation, Due in Next Fiscal Year	[2]	0
Contractual Obligation, Due after Fifth Year	[2]	628
Contractual Obligation, Due in Fifth Year	[2]	0
Contractual Obligation, Due in Fourth Year	[2]	0
Contractual Obligation, Due in Third Year	[2]	0
Contractual Obligation, Due in Second Year	[2]	0
Trust Preferred Securities [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[11]	250
Contractual Obligation, Due in Next Fiscal Year	[11]	0
Contractual Obligation, Due after Fifth Year	[11]	250
Contractual Obligation, Due in Fifth Year	[11]	0
Contractual Obligation, Due in Fourth Year	[11]	0
Contractual Obligation, Due in Third Year	[11]	0
Contractual Obligation, Due in Second Year	[11]	0
Trust Preferred Securities [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[12]	178
Contractual Obligation, Due in Next Fiscal Year	[12]	0
Contractual Obligation, Due after Fifth Year	[12]	178
Contractual Obligation, Due in Fifth Year	[12]	0
Contractual Obligation, Due in Fourth Year	[12]	0
Contractual Obligation, Due in Third Year	[12]	0
Contractual Obligation, Due in Second Year	[12]	0
Trust Preferred Securities [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[13]	200
Contractual Obligation, Due in Next Fiscal Year	[13]	0
Contractual Obligation, Due after Fifth Year	[13]	200
Contractual Obligation, Due in Fifth Year	[13]	0
Contractual Obligation, Due in Fourth Year	[13]	0
Contractual Obligation, Due in Third Year	[13]	0
Contractual Obligation, Due in Second Year	[13]	0
Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[1]	1,614
Contractual Obligation, Due in Next Fiscal Year	[1]	1,355
Contractual Obligation, Due after Fifth Year	[1]	0
Contractual Obligation, Due in Fifth Year	[1]	0
Contractual Obligation, Due in Fourth Year	[1]	13
Contractual Obligation, Due in Third Year	[1]	0
Contractual Obligation, Due in Second Year	[1]	246
Financial Standby Letter of Credit [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[14]	2
Contractual Obligation, Due in Next Fiscal Year	[14]	2
Contractual Obligation, Due after Fifth Year	[14]	0
Contractual Obligation, Due in Fifth Year	[14]	0
Contractual Obligation, Due in Fourth Year	[14]	0
Contractual Obligation, Due in Third Year	[14]	0
Contractual Obligation, Due in Second Year	[14]	0
Financial Standby Letter of Credit [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[15]	23
Contractual Obligation, Due in Next Fiscal Year	[15]	23
Contractual Obligation, Due after Fifth Year	[15]	0
Contractual Obligation, Due in Fifth Year	[15]	0
Contractual Obligation, Due in Fourth Year	[15]	0
Contractual Obligation, Due in Third Year	[15]	0
Contractual Obligation, Due in Second Year	[15]	0
Financial Standby Letter of Credit [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[16]	14
Contractual Obligation, Due in Next Fiscal Year	[16]	14
Contractual Obligation, Due after Fifth Year	[16]	0
Contractual Obligation, Due in Fifth Year	[16]	0
Contractual Obligation, Due in Fourth Year	[16]	0
Contractual Obligation, Due in Third Year	[16]	0
Contractual Obligation, Due in Second Year	[16]	0
Financial Standby Letter of Credit [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[1]	1,546
Contractual Obligation, Due in Next Fiscal Year	[1]	1,287
Contractual Obligation, Due after Fifth Year	[1]	0
Contractual Obligation, Due in Fifth Year	[1]	0
Contractual Obligation, Due in Fourth Year	[1]	13
Contractual Obligation, Due in Third Year	[1]	0
Contractual Obligation, Due in Second Year	[1]	246
Financial Standby Letter of Credit [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[17]	1
Contractual Obligation, Due in Next Fiscal Year	[17]	1
Contractual Obligation, Due after Fifth Year	[17]	0
Contractual Obligation, Due in Fifth Year	[17]	0
Contractual Obligation, Due in Fourth Year	[17]	0
Contractual Obligation, Due in Third Year	[17]	0
Contractual Obligation, Due in Second Year	[17]	0
Financial Standby Letter of Credit [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[18]	1
Contractual Obligation, Due in Next Fiscal Year	[18]	1
Contractual Obligation, Due after Fifth Year	[18]	0
Contractual Obligation, Due in Fifth Year	[18]	0
Contractual Obligation, Due in Fourth Year	[18]	0
Contractual Obligation, Due in Third Year	[18]	0
Contractual Obligation, Due in Second Year	[18]	0
GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Contractual Obligation			$ 20
Contractual Obligation, Due in Next Fiscal Year		0
Contractual Obligation, Due after Fifth Year			$ 20
Contractual Obligation, Due in Fifth Year		0
Contractual Obligation, Due in Fourth Year		0
Contractual Obligation, Due in Third Year		0
Contractual Obligation, Due in Second Year		0
GuaranteedLeaseResidualValues [Member] | Pepco Holdings LLC [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[19]	20
Contractual Obligation, Due in Next Fiscal Year	[19]	0
Contractual Obligation, Due after Fifth Year	[19]	20
Contractual Obligation, Due in Fifth Year	[19]	0
Contractual Obligation, Due in Fourth Year	[19]	0
Contractual Obligation, Due in Third Year	[19]	0
Contractual Obligation, Due in Second Year	[19]	0
GuaranteedLeaseResidualValues [Member] | Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[20]	6
Contractual Obligation, Due in Next Fiscal Year	[20]	0
Contractual Obligation, Due after Fifth Year	[20]	6
Contractual Obligation, Due in Fifth Year	[20]	0
Contractual Obligation, Due in Fourth Year	[20]	0
Contractual Obligation, Due in Third Year	[20]	0
Contractual Obligation, Due in Second Year	[20]	0
GuaranteedLeaseResidualValues [Member] | Delmarva Power and Light Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[21]	7
Contractual Obligation, Due in Next Fiscal Year	[21]	0
Contractual Obligation, Due after Fifth Year	[21]	7
Contractual Obligation, Due in Fifth Year	[21]	0
Contractual Obligation, Due in Fourth Year	[21]	0
Contractual Obligation, Due in Third Year	[21]	0
Contractual Obligation, Due in Second Year	[21]	0
GuaranteedLeaseResidualValues [Member] | Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Contractual Obligation	[22]	5
Contractual Obligation, Due in Next Fiscal Year	[22]	0
Contractual Obligation, Due after Fifth Year	[22]	5
Contractual Obligation, Due in Fifth Year	[22]	0
Contractual Obligation, Due in Fourth Year	[22]	0
Contractual Obligation, Due in Third Year	[22]	0
Contractual Obligation, Due in Second Year	[22]	$ 0
Maximum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Business Acquisition, Expected New Generation Mwh | MW		300
[1]	Letters of credit (non-debt)—Exelon and certain of its subsidiaries maintain non-debt letters of credit to provide credit support for certain transactions as requested by third parties.
[2]	Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.
[3]	Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.
[4]	Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.
[5]	Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.
[6]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246NEU0NTM4RjY2RDg5Q0NDMzBBRDQ4MTMyN0M0QjQ3RTQM}
[7]	_
[8]	_
[9]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246RUU4QUM2NTgyMUMwMjIzMjBDNUE4MTNDQTYxNzQzQ0QM}
[10]	Includes $200 million of Trust Preferred Securities of ComEd Financing III, $178 million of Trust Preferred Securities of PECO Trust III and IV and $250 million of Trust Preferred Securities of BGE Capital Trust II.
[11]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246N0E5NzcxMDgwMEM1RjEwQzcxMzk5RjkyNUQyNTk1QTIM}
[12]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246NDlFNDNFOEEzNDdGRkJFODIxM0Q5RjkyNUQyNTY4NUIM}
[13]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246MjkyMjMzMEMzNjIzOTc1NjY5NjA5RjkyNUQyNTczQjIM}
[14]	Letters of credit (non-debt)—BGE maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties.
[15]	Letters of credit (non-debt)—PECO maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties.
[16]	Letters of credit (non-debt)—ComEd maintains non-debt letters of credit to provide credit support for certain transactions as requested by third parties.
[17]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246NDI3QUMyNzExNTcwRUUzMTc2QjM4MTMyMURFRkI1MjUM}
[18]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246Njc3QzlCQzdEQjY1NDZDOTYyNDM4MTNDNDY1OEVBQkUM}
[19]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246RUI3QjVENUVBNUUxMEEwQUI3ODU4MTMyRTczMjg1RDQM}
[20]	_
[21]	_
[22]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246QzEyOUM0NEQ3Rjc2MzAwMUNEOTM4MTNDRkEzNzExMDcM}

Commitments and Contingencie187

Commitments and Contingencies - Schedule of Equity Investment Commitments (Details) - Equity Method Investments [Member] - Exelon Generation Co L L C [Member] $ in Millions	Dec. 31, 2016USD ($)
Guarantor Obligations [Line Items]
2,016	$ 34
2,017	5
Total	$ 39

Commitments and Contingencie188

Commitments and Contingencies - Schedule of Minimum Future Operating Lease Payments (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 30, 2016
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				$ 777	$ 922	$ 865
2,015			$ 183	183
2,016			179	179
2,017			123	123
2,018			140	140
2,019			133	133
Remaining years			968	968
Total minimum future lease payments			1,726	1,726
Exelon Generation Co L L C [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense	[1]			667	851	806
2,015			70	70
2,016			75	75
2,017			30	30
2,018			48	48
2,019			47	47
Remaining years			644	644
Total minimum future lease payments			914	914
Commonwealth Edison Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				15	12	15
2,015			11	11
2,016			6	6
2,017			6	6
2,018			3	3
2,019			3	3
Remaining years			0	0
Total minimum future lease payments			29	29
Commonwealth Edison Co [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments			2	2
PECO Energy Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				7	9	14
2,015			3	3
2,016			3	3
2,017			4	4
2,018			4	4
2,019			4	4
Remaining years			0	0
Total minimum future lease payments			18	18
PECO Energy Co [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments			4	4
Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				22	32	12
2,015			32	32			$ 21
2,016			34	34			25
2,017			34	34			26
2,018			34	34			27
2,019			32	32			28
Operating Leases, Future Minimum Payments, Due Thereafter							$ 14
Remaining years			33	33
Total minimum future lease payments			199	199
Baltimore Gas and Electric Company [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments			2	2
Pepco Holdings LLC [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2,015			50	50
2,016			49	49
2,017			36	36
2,018			38	38
2,019			34	34
Remaining years			211	211
Total minimum future lease payments			418	418
Pepco Holdings LLC [Member] | Predecessor [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense					0	0
Pepco Holdings LLC [Member] | Successor [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense		$ 0	49
Potomac Electric Power Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				8	7	8
2,015			7	7
2,016			6	6
2,017			5	5
2,018			4	4
2,019			3	3
Remaining years			7	7
Total minimum future lease payments			32	32
Delmarva Power and Light Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				15	14	14
2,015			13	13
2,016			17	17
2,017			7	7
2,018			10	10
2,019			9	9
Remaining years			54	54
Total minimum future lease payments			110	110
Delmarva Power and Light Company [Member] | Real Estate Leases and Railroad Licenses [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total minimum future lease payments			2	2
Atlantic City Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				13	$ 13	$ 12
2,015			8	8
2,016			8	8
2,017			7	7
2,018			6	6
2,019			5	5
Remaining years			20	20
Total minimum future lease payments			$ 54	$ 54
[1]	Includes contingent operating lease payments associated with contracted generation agreements that are not included in the minimum future operating lease payments table above. Payments made under Generation’s contracted generation lease agreements totaled $604 million, $798 million and $755 million during 2016, 2015 and 2014, respectively. Excludes contract amortization associated with purchase accounting and contract acquisitions.

Commitments and Contingencie189

Commitments and Contingencies - Schedule of Future Rental Expense under Operating Leases (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				$ 777	$ 922	$ 865
Exelon Generation Co L L C [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense	[1]			667	851	806
Long Term Contract For Purchase Of Electric Power Capacity			$ 604	604	798	755
Commonwealth Edison Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				15	12	15
PECO Energy Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				7	9	14
Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				22	32	12
Pepco Holdings LLC [Member] | Predecessor [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense					0	0
Pepco Holdings LLC [Member] | Successor [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense		$ 0	$ 49
Potomac Electric Power Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				8	7	8
Delmarva Power and Light Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				15	14	14
Atlantic City Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Lease and rental expense				$ 13	$ 13	$ 12
[1]	Includes contingent operating lease payments associated with contracted generation agreements that are not included in the minimum future operating lease payments table above. Payments made under Generation’s contracted generation lease agreements totaled $604 million, $798 million and $755 million during 2016, 2015 and 2014, respectively. Excludes contract amortization associated with purchase accounting and contract acquisitions.

Commitments and Contingencie190

Commitments and Contingencies - Schedule of Environmental Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	$ 429	$ 369
Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	325	301
Exelon Generation Co L L C [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	72	63
Exelon Generation Co L L C [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	0	0
Commonwealth Edison Co [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	292	266
Commonwealth Edison Co [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	291	264
PECO Energy Co [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	33	37
PECO Energy Co [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	31	35
Baltimore Gas and Electric Company [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	2	3
Baltimore Gas and Electric Company [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	2	2
Pepco Holdings LLC [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	30	33
Pepco Holdings LLC [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	1	1
Potomac Electric Power Company [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	27	24
Potomac Electric Power Company [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	0	0
Delmarva Power and Light Company [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	2	3
Delmarva Power and Light Company [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	1	1
Atlantic City Electric Company [Member] | Total Accrual For Environmental Loss Contingencies [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	1	1
Atlantic City Electric Company [Member] | Accrual For MGP Investigation And Remediation [Member]
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies	$ 0	$ 0

Supplemental Financial Infor191

Supplemental Financial Information - Summary of Taxes other than Income (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Financial Information Tables [Line Items]
Utilities Operating Expense, Taxes	[1]			$ 753	$ 474	$ 456
Property				483	407	396
Payroll				226	201	200
Other				114	118	102
Total taxes other than income				1,576	1,200	1,154
Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Utilities Operating Expense, Taxes	[1]			122	105	89
Property				246	250	240
Payroll				117	118	118
Other				21	16	18
Total taxes other than income				506	489	465
Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Utilities Operating Expense, Taxes	[1]			242	236	238
Property				27	27	25
Payroll				28	28	28
Other				(4)	5	2
Total taxes other than income				293	296	293
PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Utilities Operating Expense, Taxes	[1]			136	133	128
Property				13	11	15
Payroll				15	14	14
Other				0	2	2
Total taxes other than income				164	160	159
Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Utilities Operating Expense, Taxes	[1]			85	85	86
Property				123	119	114
Payroll				17	16	18
Other				4	4	3
Total taxes other than income				229	224	221
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Financial Information Tables [Line Items]
Utilities Operating Expense, Taxes	[1]		$ 253
Property			73
Payroll			23
Other			5
Total taxes other than income			$ 354
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Utilities Operating Expense, Taxes	[1]	$ 78			326	324
Property		18			94	85
Payroll		8			27	23
Other		1			8	5
Total taxes other than income		$ 105			455	437
Potomac Electric Power Company [Member]
Supplemental Financial Information Tables [Line Items]
Utilities Operating Expense, Taxes	[1]			312	308	307
Property				53	57	51
Payroll				8	6	6
Other				4	5	5
Total taxes other than income				377	376	369
Delmarva Power and Light Company [Member]
Supplemental Financial Information Tables [Line Items]
Utilities Operating Expense, Taxes	[1]			18	18	17
Property				31	28	24
Payroll				5	4	4
Other				1	1	1
Total taxes other than income				55	51	46
Atlantic City Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Utilities Operating Expense, Taxes	[1]			0	0	0
Property				3	3	3
Payroll				3	2	2
Other				1	2	(1)
Total taxes other than income				$ 7	$ 7	$ 4
[1]	Generation’s utility tax represents gross receipts tax related to its retail operations and ComEd’s, PECO’s, BGE’s, Pepco's, DPL's and ACE's utility taxes represent municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.

Supplemental Financial Infor192

Supplemental Financial Information - Summary of Other Income (Expense) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended	12 Months Ended
		Mar. 23, 2016		Dec. 31, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014		Jun. 30, 2016
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]				$ 237		$ 232		$ 216
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]				126		156		159
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units					216		(282)		180
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement					194		(197)		134
Net unrealized income (losses) on pledged assets					(1)		7		29
Regulatory offset to decommissioning trust fund-related activities	[2]				(372)		21		(358)
Total decommissioning-related activities					400		(63)		360
Investment income (loss)					17		8		1
Long-term lease income					4		15		24
Interest income related to uncertain income tax positions					13		1		40
Income Tax Examination, Penalties and Interest Expense					(106)
AFUDC—Equity					64		24		21
Terminated interest rate swaps(d)					(3)	[3]	(26)
Payments of Debt Restructuring Costs							(22)
Gain (Loss) on Disposition of Assets					(48)		18		437
Other					24		17		9
Other, net					413		(46)		455
Reclassification out of Accumulated Other Comprehensive Income [Member]
Supplemental Financial Information Tables [Line Items]
Gain (Loss) on Sale of Derivatives					26
Senior Notes [Member]
Supplemental Financial Information Tables [Line Items]
Debt Instrument, Face Amount											$ 4,200
Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Gain (Loss) on Disposition of Assets		$ 0							0
Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]				237		232		216
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]				126		156		159
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units					216		(282)		180
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement					194		(197)		134
Net unrealized income (losses) on pledged assets					(1)		7		29
Regulatory offset to decommissioning trust fund-related activities	[2]				(372)		21		(358)
Total decommissioning-related activities					400		(63)		360
Investment income (loss)					8		3		1
Long-term lease income					0		0		0
Interest income related to uncertain income tax positions					0		1		54
AFUDC—Equity					0		0		0
Terminated interest rate swaps(d)					2		0
Payments of Debt Restructuring Costs							0
Gain (Loss) on Disposition of Assets					(59)		12		437
Other					(5)		(1)		(9)
Other, net					401		(60)		406
Exelon Generation Co L L C [Member] | Senior Notes [Member]
Supplemental Financial Information Tables [Line Items]
Debt Instrument, Face Amount				$ 750	750
Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]				0		0		0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]				0		0		0
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units					0		0		0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement					0		0		0
Net unrealized income (losses) on pledged assets					0		0		0
Regulatory offset to decommissioning trust fund-related activities	[2]				0		0		0
Total decommissioning-related activities					0		0		0
Investment income (loss)					0		0		0
Long-term lease income					0		0		0
Interest income related to uncertain income tax positions					0		0		0
Income Tax Examination, Penalties and Interest Expense					(86)
AFUDC—Equity					14		5		3
Terminated interest rate swaps(d)					0		0
Payments of Debt Restructuring Costs							0
Other					7		16		14
Other, net					(65)		21		17
PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]				0		0		0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]				0		0		0
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units					0		0		0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement					0		0		0
Net unrealized income (losses) on pledged assets					0		0		0
Regulatory offset to decommissioning trust fund-related activities	[2]				0		0
Total decommissioning-related activities					0		0		0
Investment income (loss)					(1)		(2)		(1)
Long-term lease income					0		0		0
Interest income related to uncertain income tax positions					0		0		0
AFUDC—Equity					8		5		6
Terminated interest rate swaps(d)					0		0
Payments of Debt Restructuring Costs							0
Other					1		2		2
Other, net					8		5		7
Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]				0		0		0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]				0		0		0
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units					0		0		0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement					0		0		0
Net unrealized income (losses) on pledged assets					0		0		0
Regulatory offset to decommissioning trust fund-related activities	[2]				0		0		0
Total decommissioning-related activities					0		0		0
Investment income (loss)					2	[4]	4		7
Long-term lease income					0		0		0
Interest income related to uncertain income tax positions					0		0		0
AFUDC—Equity					19		14		12
Terminated interest rate swaps(d)					0		0
Payments of Debt Restructuring Costs							0
Other					0		0		(1)
Other, net					21		18		18
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]			0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]			0
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units				0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement				0
Net unrealized income (losses) on pledged assets				0
Regulatory offset to decommissioning trust fund-related activities	[2]			0
Total decommissioning-related activities				0
Investment income (loss)				1
Long-term lease income				0
Interest income related to uncertain income tax positions				(1)
AFUDC—Equity				23
Gain (Loss) on Disposition of Assets				(1)
Other				21
Other, net				$ 44
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]	0					0		0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units		0	[1]				0		0	[1]
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		0					0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		0					0		0
Net unrealized income (losses) on pledged assets		0					0	[2]	0
Regulatory offset to decommissioning trust fund-related activities		0	[2]				0		0	[2]
Total decommissioning-related activities		0					0		0
Investment income (loss)		0					0		1
Long-term lease income		0					0		0
Interest income related to uncertain income tax positions		0					34		0
AFUDC—Equity		7					14		13
Terminated interest rate swaps(d)		0					0
Payments of Debt Restructuring Costs							0
Gain (Loss) on Disposition of Assets							46
Other		(11)					40		30
Other, net		$ (4)					88		44
Potomac Electric Power Company [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]				0		0		0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units					0	[1]	0		0	[1]
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units					0		0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement					0		0		0
Net unrealized income (losses) on pledged assets					0		0	[2]
Regulatory offset to decommissioning trust fund-related activities					0	[2]	0		0	[2]
Total decommissioning-related activities					0		0		0
Investment income (loss)					1		0		0
Long-term lease income					0		0		0
Interest income related to uncertain income tax positions					1		5		1
AFUDC—Equity					19		12		10
Terminated interest rate swaps(d)					0		0
Payments of Debt Restructuring Costs							0
Gain (Loss) on Disposition of Assets					8		46		0
Other					15		11		19
Other, net					36		28		30
Delmarva Power and Light Company [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]				0		0		0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units					0	[1]	0		0	[1]
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units					0		0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement					0		0		0
Net unrealized income (losses) on pledged assets					0		0	[2]
Regulatory offset to decommissioning trust fund-related activities					0	[2]	0		0	[2]
Total decommissioning-related activities					0		0		0
Investment income (loss)					0		0		0
Long-term lease income					0		0		0
Interest income related to uncertain income tax positions					0		0		0
AFUDC—Equity					5		1		2
Terminated interest rate swaps(d)					0		0
Payments of Debt Restructuring Costs							0
Other					8		9		8
Other, net					13		10		10
Atlantic City Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]				0		0		0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units					0	[1]	0		0	[1]
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units					0		0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement					0		0		0
Net unrealized income (losses) on pledged assets					0		0	[2]
Regulatory offset to decommissioning trust fund-related activities					0	[2]	0		0	[2]
Total decommissioning-related activities					0		0		0
Investment income (loss)					1		0	[4]	0	[4]
Long-term lease income					0		0		0
Interest income related to uncertain income tax positions					0		0		1
AFUDC—Equity					6		1		1
Terminated interest rate swaps(d)					0		0
Payments of Debt Restructuring Costs							0
Other					2		2		1
Other, net					$ 9		$ 3		$ 3
[1]	Includes investment income and realized gains and losses on sales of investments within the nuclear decommissioning trust funds.
[2]	Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of net income taxes related to all NDT fund activity for those units. See Note 16 — Asset Retirement Obligations for additional information regarding the accounting for nuclear decommissioning.
[3]	In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated certain floating-to-fixed interest rate swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from AOCI to Other, net in Exelon's Consolidated Statements of Operations and Comprehensive Income.
[4]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246MkMyOTM5MEM5NEQyN0U2MTAwODM5RjkyNUQyNTcxNzkM}

Supplemental Financial Infor193

Supplemental Financial Information - Summary of Depreciation, Amortization, Accretion and Depletion (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				$ 3,477	$ 2,227	$ 2,080
Regulatory assets				407	170	191
Amortization of Intangible Assets				87	76	179
Nuclear fuel	[1]			1,159	1,116	1,073
ARO accretion	[2]			446	398	345
Total depreciation, amortization and accretion				5,576	3,987	3,868
Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				1,835	1,007	922
Regulatory assets				0	0	0
Amortization of Intangible Assets				79	69	179
Nuclear fuel	[1]			1,159	1,116	1,073
ARO accretion	[2]			446	397	345
Total depreciation, amortization and accretion				3,519	2,589	2,519
Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				708	635	588
Regulatory assets				67	72	99
Amortization of Intangible Assets				7	7	7
Nuclear fuel	[1]			0	0	0
ARO accretion	[2]			0	0	0
Total depreciation, amortization and accretion				775	707	687
PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				244	240	227
Regulatory assets				26	20	9
Nuclear fuel	[1]			0	0	0
ARO accretion	[2]			0	0	0
Total depreciation, amortization and accretion				270	260	236
Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				299	289	288
Regulatory assets				124	77	83
Nuclear fuel	[1]			0	0	0
ARO accretion	[2]			0	0	0
Total depreciation, amortization and accretion				423	366	371
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment			$ 325
Regulatory assets			190
Nuclear fuel	[1]		0
ARO accretion	[2]		0
Total depreciation, amortization and accretion			515
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment		$ 94
Regulatory assets		58
Nuclear fuel	[1]	0
ARO accretion	[2]	0
Total depreciation, amortization and accretion		152			624	526
Potomac Electric Power Company [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				175	164	155
Regulatory assets				120	92	57
Nuclear fuel	[1]			0	0	0
ARO accretion	[2]			0	0	0
Total depreciation, amortization and accretion				295	256	212
Potomac Electric Power Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment					392	363
Regulatory assets					232	163
Nuclear fuel	[1]				0	0
ARO accretion	[2]				0	0
Delmarva Power and Light Company [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				110	103	94
Regulatory assets				47	45	28
Nuclear fuel	[1]			0	0	0
ARO accretion	[2]			0	0	0
Total depreciation, amortization and accretion				157	148	122
Atlantic City Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment				82
Regulatory assets				83
Nuclear fuel	[1]			0
ARO accretion	[2]			0
Total depreciation, amortization and accretion				165	175	155
Atlantic City Electric Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Property, plant and equipment					76	72
Regulatory assets					99	83
Nuclear fuel	[1]				0	0
ARO accretion	[2]				0	0
Unamortized Energy Contracts [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			35	22	135
Unamortized Energy Contracts [Member] | Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			35	22	135
Unamortized Energy Contracts [Member] | Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0	0	0
Unamortized Energy Contracts [Member] | PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0	0	0
Unamortized Energy Contracts [Member] | Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0	0	0
Unamortized Energy Contracts [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]		0
Unamortized Energy Contracts [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]	0
Unamortized Energy Contracts [Member] | Potomac Electric Power Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0	0	0
Unamortized Energy Contracts [Member] | Potomac Electric Power Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]				0	0
Unamortized Energy Contracts [Member] | Delmarva Power and Light Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0	0	0
Unamortized Energy Contracts [Member] | Atlantic City Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]			0
Unamortized Energy Contracts [Member] | Atlantic City Electric Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets	[3]				0	0
Other Intangible Assets [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				52	54	44
Other Intangible Assets [Member] | Exelon Generation Co L L C [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				44	47	44
Other Intangible Assets [Member] | Commonwealth Edison Co [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				0	0	0
Other Intangible Assets [Member] | PECO Energy Co [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				0	0	0
Other Intangible Assets [Member] | Baltimore Gas and Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				0	0	0
Other Intangible Assets [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets			$ 0
Other Intangible Assets [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets		$ 0
Other Intangible Assets [Member] | Potomac Electric Power Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				0	0	0
Other Intangible Assets [Member] | Potomac Electric Power Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets					0	0
Other Intangible Assets [Member] | Delmarva Power and Light Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				0	0	0
Other Intangible Assets [Member] | Atlantic City Electric Company [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets				$ 0
Other Intangible Assets [Member] | Atlantic City Electric Company [Member] | Predecessor [Member]
Supplemental Financial Information Tables [Line Items]
Amortization of Intangible Assets					$ 0	$ 0
[1]	Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[2]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[3]	Included in Operating revenues or Purchased power and fuel on the Registrants’ Consolidated Statements of Operations and Comprehensive Income

Supplemental Financial Infor194

Supplemental Financial Information - Supplemental Cash Flow Information (Details) - USD ($)		3 Months Ended		9 Months Ended		12 Months Ended
		Mar. 23, 2016	Mar. 31, 2015	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 24, 2016
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)						$ 1,340,000,000	$ 930,000,000	$ 940,000,000
Income taxes (net of refunds)						(441,000,000)	342,000,000	314,000,000
Pension and non-pension postretirement benefit costs						619,000,000	637,000,000	560,000,000
Income (Loss) from Equity Method Investments						24,000,000	7,000,000	0
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions						0	0	20,000,000
IncomeLossFromEquityMethodInvestmentsNonCash								22,000,000
Provision for uncollectible accounts						155,000,000	120,000,000	156,000,000
Provision for excess and obsolete inventory						12,000,000	10,000,000	5,000,000
Stock-based compensation costs						111,000,000	97,000,000	91,000,000
Other decommissioning related-activity						(384,000,000)	(82,000,000)	(132,000,000)
Energy-related options						(11,000,000)	21,000,000	122,000,000
Amortization of regulatory asset related to debt costs						9,000,000	7,000,000	11,000,000
Amortization of rate stabilization deferral						76,000,000	73,000,000	65,000,000
Amortization of debt fair value adjustment						(11,000,000)	(17,000,000)	(23,000,000)
Merger-related commitments (c)(d)						558,000,000		44,000,000
Restructuring Costs						99,000,000
Asset Retirement Obligation, Revision of Estimate						2,000,000
Amortization of Debt Issuance Costs						35,000,000	144,000,000	53,000,000
Discrete impacts from EIMA						8,000,000	58,000,000	53,000,000
Lower of cost or market inventory adjustment						37,000,000	23,000,000	29,000,000
Litigation Settlement, Amount						(28,000,000)
Proceeds from Collection of Other Receivables						(13,000,000)
Other						35,000,000	11,000,000	(2,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities						1,333,000,000	1,109,000,000	1,054,000,000
Other Noncash Expense							77,000,000
Change in PPE related to ARO update				$ 191,000,000		191,000,000	885,000,000	72,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash						(128,000,000)	(96,000,000)	(220,000,000)
Payments to Acquire Businesses, Gross						6,934,000,000	40,000,000	386,000,000
Noncash or Part Noncash Acquisition, Fixed Assets Acquired						(54,000,000)
Consolidated VIE dividend to noncontrolling								4,000,000
Fair value of net assets recorded upon CENG consolidation								3,400,000,000
Issuance of equity units								(131,000,000)
Contribution of Property								0
Non Cash Licensing Agreement							95,000,000
Antelope Valle [Member]
Supplemental Cash Flow Information [Line Items]
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash							(170,000,000)
Capital Project [Member]
Supplemental Cash Flow Information [Line Items]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired						(95,000,000)
Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options								70,000,000
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							(57,000,000)
Contribution of Property						0	0
Exelon Generation Co L L C [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)						339,000,000	348,000,000	322,000,000
Income taxes (net of refunds)						435,000,000	476,000,000	227,000,000
Pension and non-pension postretirement benefit costs						218,000,000	269,000,000	249,000,000
Income (Loss) from Equity Method Investments			$ (19,000,000)			0	0	20,000,000
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions						25,000,000	8,000,000	0
IncomeLossFromEquityMethodInvestmentsNonCash								(20,000,000)
Provision for uncollectible accounts						19,000,000	22,000,000	14,000,000
Provision for excess and obsolete inventory						6,000,000	9,000,000	5,000,000
Stock-based compensation costs						0	0	0
Other decommissioning related-activity						(384,000,000)	(82,000,000)	(132,000,000)
Energy-related options						(11,000,000)	21,000,000	122,000,000
Amortization of regulatory asset related to debt costs						0	0	0
Amortization of rate stabilization deferral						0	0	0
Amortization of debt fair value adjustment						(11,000,000)	(17,000,000)	(23,000,000)
Merger-related commitments (c)(d)						53,000,000		44,000,000
Restructuring Costs						22,000,000
Asset Retirement Obligation, Revision of Estimate					$ 285,000,000		1,300,000,000
Amortization of Debt Issuance Costs						17,000,000	15,000,000	12,000,000
Discrete impacts from EIMA						0	0	0
Lower of cost or market inventory adjustment						36,000,000	23,000,000	29,000,000
Other						25,000,000	0	6,000,000
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities						15,000,000	268,000,000	346,000,000
Other Noncash Expense							77,000,000
Change in PPE related to ARO update				191,000,000		191,000,000	885,000,000	72,000,000
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash						(50,000,000)	(82,000,000)	(61,000,000)
Payments to Acquire Businesses, Gross						293,000,000	40,000,000	386,000,000
Noncash or Part Noncash Acquisition, Fixed Assets Acquired						(54,000,000)
Consolidated VIE dividend to noncontrolling								645,000,000
Fair value of net assets recorded upon CENG consolidation								3,400,000,000
Issuance of equity units								0
Contribution of Property								0
Exelon Generation Co L L C [Member] | Capital Project [Member]
Supplemental Cash Flow Information [Line Items]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired						(95,000,000)
Exelon Generation Co L L C [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options								70,000,000
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							(57,000,000)
Contribution of Property						0	0
Commonwealth Edison Co [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)						298,000,000	308,000,000	292,000,000
Income taxes (net of refunds)						(444,000,000)	(265,000,000)	(6,000,000)
Pension and non-pension postretirement benefit costs						166,000,000	206,000,000	162,000,000
Income (Loss) from Equity Method Investments						0	0
IncomeLossFromEquityMethodInvestmentsNonCash								0
Provision for uncollectible accounts						41,000,000	53,000,000	26,000,000
Provision for excess and obsolete inventory						4,000,000	1,000,000	0
Stock-based compensation costs						0	0	0
Other decommissioning related-activity						0	0	0
Energy-related options						0	0	0
Amortization of regulatory asset related to debt costs						4,000,000	5,000,000	8,000,000
Amortization of rate stabilization deferral						0	0	0
Amortization of debt fair value adjustment						0	0	0
Merger-related commitments (c)(d)						0		0
Restructuring Costs						0
Amortization of Debt Issuance Costs						4,000,000	4,000,000	4,000,000
Discrete impacts from EIMA						8,000,000	144,000,000	53,000,000
Lower of cost or market inventory adjustment						0	0
Other						(12,000,000)	3,000,000	2,000,000
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities						215,000,000	416,000,000	255,000,000
Change in PPE related to ARO update				0		0	0	0
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash						(91,000,000)	(34,000,000)	(78,000,000)
Fair value of net assets recorded upon CENG consolidation								0
Issuance of equity units								0
Contribution of Property								5,000,000
Commonwealth Edison Co [Member] | Capital Project [Member]
Supplemental Cash Flow Information [Line Items]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired						0
Commonwealth Edison Co [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0
Contribution of Property						158,000,000	7,000,000
PECO Energy Co [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)						104,000,000	94,000,000	94,000,000
Income taxes (net of refunds)						64,000,000	64,000,000	85,000,000
Pension and non-pension postretirement benefit costs						33,000,000	39,000,000	36,000,000
Income (Loss) from Equity Method Investments						0	0
IncomeLossFromEquityMethodInvestmentsNonCash								0
Provision for uncollectible accounts						30,000,000	30,000,000	52,000,000
Provision for excess and obsolete inventory						0	0	0
Stock-based compensation costs						0	0	0
Other decommissioning related-activity						0	0	0
Energy-related options						0	0	0
Amortization of regulatory asset related to debt costs						1,000,000	2,000,000	3,000,000
Amortization of rate stabilization deferral						0	0	0
Amortization of debt fair value adjustment						0	0	0
Merger-related commitments (c)(d)						0		0
Amortization of Debt Issuance Costs						3,000,000	2,000,000	2,000,000
Discrete impacts from EIMA						0	0	0
Lower of cost or market inventory adjustment						1,000,000	0
Other						(3,000,000)	(3,000,000)	(1,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities						65,000,000	70,000,000	92,000,000
Change in PPE related to ARO update				0		0	0	0
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash						(11,000,000)	(13,000,000)	0
Fair value of net assets recorded upon CENG consolidation								0
Issuance of equity units								0
Contribution of Property								0
PECO Energy Co [Member] | Capital Project [Member]
Supplemental Cash Flow Information [Line Items]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired						0
PECO Energy Co [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0
Contribution of Property						0	0
Baltimore Gas and Electric Company [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)						92,000,000	120,000,000	111,000,000
Income taxes (net of refunds)						31,000,000	73,000,000	(21,000,000)
Pension and non-pension postretirement benefit costs						67,000,000	65,000,000	64,000,000
Income (Loss) from Equity Method Investments						0	0
IncomeLossFromEquityMethodInvestmentsNonCash								0
Provision for uncollectible accounts						1,000,000	15,000,000	64,000,000
Provision for excess and obsolete inventory						0	0	0
Stock-based compensation costs						0	0	0
Other decommissioning related-activity						0	0	0
Energy-related options						0	0	0
Amortization of regulatory asset related to debt costs						0	0	0
Amortization of rate stabilization deferral						81,000,000	73,000,000	65,000,000
Amortization of debt fair value adjustment						0	0	0
Merger-related commitments (c)(d)						0		0
Amortization of Debt Issuance Costs						1,000,000	2,000,000	2,000,000
Discrete impacts from EIMA						0	0	0
Lower of cost or market inventory adjustment						0	0
Litigation Settlement, Amount						(28,000,000)
Proceeds from Collection of Other Receivables						(13,000,000)
Other						(21,000,000)	(18,000,000)	(15,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities						88,000,000	137,000,000	180,000,000
Change in PPE related to ARO update				0		0	0	0
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash						(86,000,000)	(9,000,000)	(25,000,000)
Fair value of net assets recorded upon CENG consolidation								0
Issuance of equity units								0
Contribution of Property								0
Baltimore Gas and Electric Company [Member] | Capital Project [Member]
Supplemental Cash Flow Information [Line Items]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired						0
Baltimore Gas and Electric Company [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0
Contribution of Property						0	0
Pepco Holdings LLC [Member]
Supplemental Cash Flow Information [Line Items]
Litigation Settlement, Amount						1,600,000
Pepco Holdings LLC [Member] | Deferred Compensation, Share-based Payments [Member]
Supplemental Cash Flow Information [Line Items]
Payments to Acquire Businesses, Gross	[1]					29,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)				209,000,000
Income taxes (net of refunds)				258,000,000
Pension and non-pension postretirement benefit costs				86,000,000
Income (Loss) from Equity Method Investments				0
Provision for uncollectible accounts				65,000,000
Provision for excess and obsolete inventory				1,000,000
Stock-based compensation costs				0
Other decommissioning related-activity				0
Energy-related options				0
Amortization of regulatory asset related to debt costs				3,000,000
Amortization of rate stabilization deferral				(5,000,000)
Amortization of debt fair value adjustment				0
Merger-related commitments (c)(d)				317,000,000
Restructuring Costs				56,000,000
Asset Retirement Obligation, Revision of Estimate				2,000,000
Amortization of Debt Issuance Costs				1,000,000
Discrete impacts from EIMA				0
Lower of cost or market inventory adjustment				0
Other				(12,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities				514,000,000
Change in PPE related to ARO update									$ 0
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash				(21,000,000)
NonCashFairValueAdjustment				127,000,000
Business Combination, Contingent Consideration, Liability, Noncurrent									$ 53,000,000
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)		$ 43,000,000					268,000,000	257,000,000
Income taxes (net of refunds)		11,000,000					(13,000,000)	(2,000,000)
Pension and non-pension postretirement benefit costs		23,000,000					97,000,000	58,000,000
Income (Loss) from Equity Method Investments		0					0
IncomeLossFromEquityMethodInvestmentsNonCash								0
Provision for uncollectible accounts		16,000,000					61,000,000	49,000,000
Provision for excess and obsolete inventory		1,000,000					1,000,000	0
Stock-based compensation costs		3,000,000					13,000,000	18,000,000
Other decommissioning related-activity		0					0	0
Energy-related options		0					0	0
Amortization of regulatory asset related to debt costs		1,000,000					5,000,000	5,000,000
Amortization of rate stabilization deferral		5,000,000					(2,000,000)	2,000,000
Amortization of debt fair value adjustment		0					0	0
Merger-related commitments (c)(d)		0						0
Restructuring Costs		0
Amortization of Debt Issuance Costs		0					2,000,000	1,000,000
Discrete impacts from EIMA		0						0
Lower of cost or market inventory adjustment		0					0
Other		(3,000,000)					(10,000,000)	(6,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities		46,000,000					167,000,000	127,000,000
Change in PPE related to ARO update		0					0	0
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash		(11,000,000)					(6,000,000)	(28,000,000)
Fair value of net assets recorded upon CENG consolidation								0
Issuance of equity units								0
Contribution of Property								0
Pepco Holdings LLC [Member] | Indemnification Agreement [Member] | Successor [Member]
Supplemental Cash Flow Information [Line Items]
Contribution of Property				0
Pepco Holdings LLC [Member] | Indemnification Agreement [Member] | Predecessor [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0
Contribution of Property		$ 0
Potomac Electric Power Company [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)						118,000,000	116,000,000	111,000,000
Income taxes (net of refunds)						216,000,000	(6,000,000)	(58,000,000)
Pension and non-pension postretirement benefit costs						31,000,000	30,000,000	22,000,000
Income (Loss) from Equity Method Investments						0	0
IncomeLossFromEquityMethodInvestmentsNonCash								0
Provision for uncollectible accounts						29,000,000	21,000,000	17,000,000
Provision for excess and obsolete inventory						3,000,000	0	0
Stock-based compensation costs						0	0	0
Other decommissioning related-activity						0	0	0
Energy-related options						0	0	0
Amortization of regulatory asset related to debt costs						2,000,000	2,000,000	3,000,000
Amortization of rate stabilization deferral						(12,000,000)	1,000,000	3,000,000
Amortization of debt fair value adjustment						0	0	0
Merger-related commitments (c)(d)						125,000,000		0
Amortization of Debt Issuance Costs							0	0
Discrete impacts from EIMA							0	0
Lower of cost or market inventory adjustment							0
Other						5,000,000	0	(8,000,000)
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities						183,000,000	54,000,000	37,000,000
Change in PPE related to ARO update				0		0	0
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash						(27,000,000)	(1,000,000)	(10,000,000)
Payments to Acquire Businesses, Gross						33,000,000
Fair value of net assets recorded upon CENG consolidation								0
Issuance of equity units								0
Potomac Electric Power Company [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0
Contribution of Property							0
Delmarva Power and Light Company [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)						47,000,000	47,000,000	45,000,000
Income taxes (net of refunds)						115,000,000	(5,000,000)	(43,000,000)
Pension and non-pension postretirement benefit costs						18,000,000	15,000,000	7,000,000
Income (Loss) from Equity Method Investments						0	0
IncomeLossFromEquityMethodInvestmentsNonCash								0
Provision for uncollectible accounts						23,000,000	20,000,000	14,000,000
Provision for excess and obsolete inventory						1,000,000	0	0
Stock-based compensation costs						0	0	0
Other decommissioning related-activity						0	0	0
Energy-related options						0	0	0
Amortization of regulatory asset related to debt costs						1,000,000	1,000,000	2,000,000
Amortization of rate stabilization deferral						2,000,000	(3,000,000)	(1,000,000)
Amortization of debt fair value adjustment						0	0	0
Merger-related commitments (c)(d)						82,000,000		0
Asset Retirement Obligation, Revision of Estimate						1,000,000
Amortization of Debt Issuance Costs							0	0
Discrete impacts from EIMA							0	0
Lower of cost or market inventory adjustment							0
Other						(14,000,000)	0	0
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities						114,000,000	33,000,000	22,000,000
Change in PPE related to ARO update				0		0	0
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash						(12,000,000)	(3,000,000)	(8,000,000)
Fair value of net assets recorded upon CENG consolidation								0
Issuance of equity units								0
Delmarva Power and Light Company [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0
Contribution of Property							0
Atlantic City Electric Company [Member]
Supplemental Cash Flow Information [Line Items]
Interest (net of amount capitalized)						62,000,000	63,000,000	61,000,000
Income taxes (net of refunds)						200,000,000	0	(3,000,000)
Pension and non-pension postretirement benefit costs						15,000,000	15,000,000	13,000,000
Income (Loss) from Equity Method Investments						0	0
IncomeLossFromEquityMethodInvestmentsNonCash								0
Provision for uncollectible accounts						32,000,000	20,000,000	13,000,000
Provision for excess and obsolete inventory						1,000,000	0	0
Stock-based compensation costs						0	0	0
Other decommissioning related-activity						0	0	0
Energy-related options						0	0	0
Amortization of regulatory asset related to debt costs						1,000,000	1,000,000	0
Amortization of rate stabilization deferral						0	0	0
Amortization of debt fair value adjustment						0	0	0
Merger-related commitments (c)(d)						110,000,000		0
Asset Retirement Obligation, Revision of Estimate						2,000,000
Amortization of Debt Issuance Costs							0	0
Discrete impacts from EIMA							0	0
Lower of cost or market inventory adjustment							0
Other						(6,000,000)	1,000,000	0
Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities						155,000,000	37,000,000	26,000,000
Change in PPE related to ARO update				0		0	0
Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash						(11,000,000)	(3,000,000)	(9,000,000)
Fair value of net assets recorded upon CENG consolidation								0
Issuance of equity units								0
Atlantic City Electric Company [Member] | Indemnification Agreement [Member]
Supplemental Cash Flow Information [Line Items]
Energy-related options								$ 0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired							0
Contribution of Property						$ 0	0
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Cash Flow Information [Line Items]
Payments to Acquire Businesses, Gross	[2]			62,000,000
Pepco Holdings LLC [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Cash Flow Information [Line Items]
Payments to Acquire Businesses, Gross				33,000,000
Pepco Holdings LLC [Member] | Pepco Holdings LLC [Member] | Successor [Member] | Deferred Compensation, Share-based Payments [Member]
Supplemental Cash Flow Information [Line Items]
Payments to Acquire Businesses, Gross				$ 29,000,000
Severance [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Cash Flow Information [Line Items]
Discrete impacts from EIMA							$ 0
[1]	PHI’s unvested time-based restricted stock units and performance-based restricted stock units issued prior to April 29, 2014 were immediately vested and paid in cash upon the close of the merger. PHI’s remaining unvested time-based restricted stock units as of the close of the merger were cancelled. There were no remaining unvested performance-based restricted stock units as of the close of the merger.
[2]	he liabilities assumed include $29 million for PHI stock-based compensation awards and $33 million for a merger related obligation, each assumed by PHI from Exelon. See Note 4 — Mergers, Acquisitions, and Dispositions.

Supplemental Financial Infor195

Supplemental Financial Information - Narrative (Details) - PECO Energy Co [Member] $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
Supplemental Financial Information Tables [Line Items]
Amount included in capital expenditures	$ 2
Smart Grid Grant Reimbursements	$ 5

Supplemental Financial Infor196

Supplemental Financial Information - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Supplemental Balance Sheet Information [Line Items]
Total equity method investments		$ 311	$ 112
Net investment in leases(b)	[1]		358
Investments		629	639
Compensation-related accruals	[2]	1,199	1,014
Taxes accrued		723	293
Interest accrued		1,234	915
Severance accrued		44	21
Other accrued expenses		260	133
Total accrued expenses		3,460	2,376
Financing Trusts [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments	[3]	22	22
Bloom Energy [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		216	63
Net Power [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		57	23
Other Equity Method Investments [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		16	4
Trust for Benefit of Employees [Member]
Supplemental Balance Sheet Information [Line Items]
Employee benefit trusts and investments	[4]	232	85
Other Investments [Member]
Supplemental Balance Sheet Information [Line Items]
Other cost method investments		52	55
Other available for sale investments		34	29
Exelon Generation Co L L C [Member]
Supplemental Balance Sheet Information [Line Items]
Total equity method investments		288	89
Net investment in leases(b)	[1]		6
Investments		418	210
Compensation-related accruals	[2]	557	547
Taxes accrued		239	186
Interest accrued		82	77
Severance accrued		15	11
Other accrued expenses		96	114
Total accrued expenses		989	935
Exelon Generation Co L L C [Member] | Financing Trusts [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments	[3]	0	0
Exelon Generation Co L L C [Member] | Bloom Energy [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		216	63
Exelon Generation Co L L C [Member] | Net Power [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		57	23
Exelon Generation Co L L C [Member] | Other Equity Method Investments [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		15	3
Exelon Generation Co L L C [Member] | Trust for Benefit of Employees [Member]
Supplemental Balance Sheet Information [Line Items]
Employee benefit trusts and investments	[4]	44	31
Exelon Generation Co L L C [Member] | Other Investments [Member]
Supplemental Balance Sheet Information [Line Items]
Other cost method investments		52	55
Other available for sale investments		34	29
Commonwealth Edison Co [Member]
Supplemental Balance Sheet Information [Line Items]
Total equity method investments		6	6
Investments		6	6
Compensation-related accruals	[2]	199	183
Taxes accrued		330	63
Interest accrued		609	443
Severance accrued		2	3
Other accrued expenses		110	14
Total accrued expenses		1,250	706
Commonwealth Edison Co [Member] | Financing Trusts [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments	[3]	6	6
Commonwealth Edison Co [Member] | Malacha [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments			0
PECO Energy Co [Member]
Supplemental Balance Sheet Information [Line Items]
Total equity method investments		8	8
Investments		25	28
Compensation-related accruals	[2]	67	66
Taxes accrued		4	4
Interest accrued		30	35
Severance accrued		0	0
Other accrued expenses		3	4
Total accrued expenses		104	109
PECO Energy Co [Member] | Financing Trusts [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments	[3]	8	8
PECO Energy Co [Member] | Trust for Benefit of Employees [Member]
Supplemental Balance Sheet Information [Line Items]
Employee benefit trusts and investments	[4]	17	20
Baltimore Gas and Electric Company [Member]
Supplemental Balance Sheet Information [Line Items]
Total equity method investments		8	8
Investments		12	12
Compensation-related accruals	[2]	64	57
Taxes accrued		78	23
Interest accrued		31	27
Severance accrued		0	1
Other accrued expenses		2	2
Total accrued expenses		175	110
Baltimore Gas and Electric Company [Member] | Financing Trusts [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments	[3]	8	8
Baltimore Gas and Electric Company [Member] | Trust for Benefit of Employees [Member]
Supplemental Balance Sheet Information [Line Items]
Employee benefit trusts and investments	[4]	4	4
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Balance Sheet Information [Line Items]
Total equity method investments		0
Investments		133
Compensation-related accruals	[2]	112
Taxes accrued		65
Interest accrued		49
Severance accrued		19
Other accrued expenses		27
Total accrued expenses		272
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Balance Sheet Information [Line Items]
Total equity method investments			0
Investments			80
Compensation-related accruals	[2]		88
Taxes accrued			77
Interest accrued			54
Severance accrued			0
Other accrued expenses			47
Total accrued expenses			266
Pepco Holdings LLC [Member] | Financing Trusts [Member] | Successor [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments	[3]	0
Pepco Holdings LLC [Member] | Financing Trusts [Member] | Predecessor [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments	[3]		0
Pepco Holdings LLC [Member] | Bloom Energy [Member] | Successor [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0
Pepco Holdings LLC [Member] | Bloom Energy [Member] | Predecessor [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments			0
Pepco Holdings LLC [Member] | Net Power [Member] | Successor [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0
Pepco Holdings LLC [Member] | Net Power [Member] | Predecessor [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments			0
Pepco Holdings LLC [Member] | Other Equity Method Investments [Member] | Successor [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0
Pepco Holdings LLC [Member] | Other Equity Method Investments [Member] | Predecessor [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments			0
Pepco Holdings LLC [Member] | Trust for Benefit of Employees [Member] | Successor [Member]
Supplemental Balance Sheet Information [Line Items]
Other available for sale investments		133
Pepco Holdings LLC [Member] | Trust for Benefit of Employees [Member] | Predecessor [Member]
Supplemental Balance Sheet Information [Line Items]
Employee benefit trusts and investments			80
Pepco Holdings LLC [Member] | Other Investments [Member] | Predecessor [Member]
Supplemental Balance Sheet Information [Line Items]
Other cost method investments			0
Potomac Electric Power Company [Member]
Supplemental Balance Sheet Information [Line Items]
Total equity method investments		0	0
Investments		102	68
Compensation-related accruals	[2]	30	26
Taxes accrued		48	56
Interest accrued		21	23
Severance accrued		0	0
Other accrued expenses		14	14
Total accrued expenses		113	119
Potomac Electric Power Company [Member] | Financing Trusts [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments	[3]	0	0
Potomac Electric Power Company [Member] | Bloom Energy [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0	0
Potomac Electric Power Company [Member] | Net Power [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0	0
Potomac Electric Power Company [Member] | Other Equity Method Investments [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0	0
Potomac Electric Power Company [Member] | Trust for Benefit of Employees [Member]
Supplemental Balance Sheet Information [Line Items]
Employee benefit trusts and investments			68
Other available for sale investments		102
Potomac Electric Power Company [Member] | Other Investments [Member]
Supplemental Balance Sheet Information [Line Items]
Other cost method investments			0
Delmarva Power and Light Company [Member]
Supplemental Balance Sheet Information [Line Items]
Total equity method investments		0	0
Investments		0	0
Compensation-related accruals	[2]	17	14
Taxes accrued		4	3
Interest accrued		8	8
Severance accrued		0	0
Other accrued expenses		7	6
Total accrued expenses		36	31
Delmarva Power and Light Company [Member] | Financing Trusts [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments	[3]	0	0
Delmarva Power and Light Company [Member] | Bloom Energy [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0	0
Delmarva Power and Light Company [Member] | Net Power [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0	0
Delmarva Power and Light Company [Member] | Other Equity Method Investments [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0	0
Delmarva Power and Light Company [Member] | Trust for Benefit of Employees [Member]
Supplemental Balance Sheet Information [Line Items]
Employee benefit trusts and investments			0
Other available for sale investments		0
Delmarva Power and Light Company [Member] | Other Investments [Member]
Supplemental Balance Sheet Information [Line Items]
Other cost method investments			0
Atlantic City Electric Company [Member]
Supplemental Balance Sheet Information [Line Items]
Total equity method investments		0	0
Investments		0	0
Compensation-related accruals	[2]	11	8
Taxes accrued		9	23
Interest accrued		12	13
Severance accrued		0	0
Other accrued expenses		6	26
Total accrued expenses		38	70
Atlantic City Electric Company [Member] | Financing Trusts [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments	[3]	0	0
Atlantic City Electric Company [Member] | Bloom Energy [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0	0
Atlantic City Electric Company [Member] | Net Power [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0	0
Atlantic City Electric Company [Member] | Other Equity Method Investments [Member]
Supplemental Balance Sheet Information [Line Items]
Equity Method Investments		0	0
Atlantic City Electric Company [Member] | Trust for Benefit of Employees [Member]
Supplemental Balance Sheet Information [Line Items]
Employee benefit trusts and investments			0
Other available for sale investments		$ 0
Atlantic City Electric Company [Member] | Other Investments [Member]
Supplemental Balance Sheet Information [Line Items]
Other cost method investments			$ 0
[1]	Represents direct financing lease investments.
[2]	Primarily includes accrued payroll, bonuses and other incentives, vacation and benefits.
[3]	Includes investments in affiliated financing trusts, which were not consolidated within the financial statements of Exelon and are shown as investments on the Consolidated Balance Sheets. See Note 1 — Significant Accounting Policies for additional information.
[4]	(c)The Registrants’ investments in these marketable securities are recorded at fair market value.

Segment Information - Narrative

Segment Information - Narrative (Details)	12 Months Ended
	Dec. 31, 2016Reportable_segment
Segment Reporting Information [Line Items]
Number of reportable segments	12
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	6
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	3

Segment Information - Analysis

Segment Information - Analysis and Reconciliation to Consolidated Financial Statements (Details) - USD ($) $ in Millions		3 Months Ended									9 Months Ended	12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Mar. 23, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Segment Reporting Information [Line Items]
Competitive Energy Revenue												$ 13,960		$ 15,200		$ 13,773
Electric operating revenues												13,869		9,876		9,467
Natural gas operating revenues												1,166		1,176		1,325
Other Operating Income												211		757		154
Revenue from Purchased Oil and Gas												2,146		2,433		2,704
Operating revenues from affiliates												10		9		23
Depreciation and amortization												3,936		2,450		2,314
Operating Expenses	[1]											28,200		25,056		25,039
Equity in earnings (losses) of unconsolidated affiliates												0		0		(20)
Income (Loss) from Equity Method Investments												(24)		(7)		0
Interest expense, net												1,536		1,033		1,065
Income (loss) from continuing operations before income taxes												1,989		3,330		2,486
Income taxes												761		1,073		666
Net income												1,204		2,250		1,820
Assets	[2]	$ 114,904					$ 95,384				$ 114,904	114,904		95,384
Utilities Operating Expense, Taxes	[3]											753		474		456
Payments to Acquire Property, Plant, and Equipment												8,553		7,624		6,077
Sales Revenue, Services, Other												7		5		6
PECO Energy Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[4]											1		1		1
Pepco Holdings LLC [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5]					$ 1,096								4,770		4,614
Natural gas operating revenues	[5]					57								165		194
Net income						19								327		242
Assets							16,188							16,188
Sales Revenue, Services, Other	[5]					0								0		0
Pepco Holdings LLC [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5]										3,506
Natural gas operating revenues	[5]										92
Net income											(61)
Assets		21,025									21,025	21,025
Sales Revenue, Services, Other	[5]										45
Corporate, Non-Segment [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	[6]											0		0		0
Electric operating revenues	[6]											0		0		0
Natural gas operating revenues	[6]											0		0		0
Other Operating Income	[6]											0		0		0
Revenue from Purchased Oil and Gas	[6]											0		0		0
Depreciation and amortization	[6]											74		63		53
Operating Expenses	[1],[6]											1,928		1,444		1,353
Equity in earnings (losses) of unconsolidated affiliates	[6]															0
Income (Loss) from Equity Method Investments	[6]											1		1
Interest expense, net	[6]											290		123		169
Income (loss) from continuing operations before income taxes	[6]											(555)		(219)		(227)
Income taxes	[6]											(156)		(41)		(63)
Net income	[6]											(398)		(177)		(164)
Assets	[6]	10,369					15,389				10,369	10,369		15,389
Payments to Acquire Property, Plant, and Equipment	[6]											113		65		95
Sales Revenue, Services, Other	[6]											1,648		1,372		1,285
Corporate, Non-Segment [Member] | Corporate and Other [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5],[7]					42								210		264
Natural gas operating revenues	[5],[7]					1								1		0
Depreciation and amortization	[7]					11								45		38
Operating Expenses	[7]					73								220		350
Interest expense, net	[7]					11								43		42
Income (loss) from continuing operations before income taxes	[7]					59								23		306
Income taxes	[7]					(16)								(48)		(228)
Net income	[7]					(44)								25		(78)
Assets	[7]						7,162							7,162
Payments to Acquire Property, Plant, and Equipment	[7]					11								34		79
Sales Revenue, Services, Other	[5],[7]					0								0		0
Corporate, Non-Segment [Member] | Corporate and Other [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5],[7]										5
Natural gas operating revenues	[5],[7]										0
Depreciation and amortization	[7]										43
Operating Expenses	[7]										33
Interest expense, net	[7]										12
Income (loss) from continuing operations before income taxes	[7]										(84)
Income taxes	[7]										(23)
Net income	[7]										(34)
Assets	[7]	10,804									10,804	10,804
Payments to Acquire Property, Plant, and Equipment	[7]										24
Sales Revenue, Services, Other	[5],[7]										45
Operating Segments [Member] | Atlantic City Electric Company [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5]					268								1,295		1,210
Natural gas operating revenues	[5]					0								0		0
Depreciation and amortization						37								175		155
Operating Expenses						251								1,161		1,073
Interest expense, net						15								64		64
Income (loss) from continuing operations before income taxes						5								73		76
Income taxes						1								33		30
Net income						5								40		46
Assets							3,387							3,387
Payments to Acquire Property, Plant, and Equipment						93								300		225
Sales Revenue, Services, Other	[5]					0								0		0
Operating Segments [Member] | Atlantic City Electric Company [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5]										989
Natural gas operating revenues	[5]										0
Depreciation and amortization											128
Operating Expenses											1,000
Interest expense, net											47
Income (loss) from continuing operations before income taxes											(51)
Income taxes											(5)
Net income											(47)
Assets		3,457									3,457	3,457
Payments to Acquire Property, Plant, and Equipment											218
Sales Revenue, Services, Other	[5]										0
Operating Segments [Member] | Delmarva Power and Light Company [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5]					279								1,138		1,088
Natural gas operating revenues	[5]					56								164		194
Depreciation and amortization						37								148		122
Operating Expenses						284								1,137		1,075
Interest expense, net						12								50		48
Income (loss) from continuing operations before income taxes						43								125		169
Income taxes						17								49		65
Net income						26								76		104
Assets							3,969							3,969
Payments to Acquire Property, Plant, and Equipment						72								352		352
Sales Revenue, Services, Other	[5]					0								0		0
Operating Segments [Member] | Delmarva Power and Light Company [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5]										850
Natural gas operating revenues	[5]										92
Depreciation and amortization											120
Operating Expenses											952
Interest expense, net											38
Income (loss) from continuing operations before income taxes											(30)
Income taxes											5
Net income											(35)
Assets		4,153									4,153	4,153
Payments to Acquire Property, Plant, and Equipment											277
Sales Revenue, Services, Other	[5]										0
Operating Segments [Member] | Potomac Electric Power Company [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5]					511								2,129		2,055
Natural gas operating revenues	[5]					0								0		0
Depreciation and amortization						71								256		212
Operating Expenses						443								1,790		1,706
Interest expense, net						29								124		115
Income (loss) from continuing operations before income taxes						47								289		264
Income taxes						15								102		93
Net income						32								187		171
Assets							6,908							6,908
Payments to Acquire Property, Plant, and Equipment						97								544		567
Sales Revenue, Services, Other	[5]					0								0		0
Operating Segments [Member] | Potomac Electric Power Company [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5]										1,675
Natural gas operating revenues	[5]										0
Depreciation and amortization											224
Operating Expenses											1,577
Interest expense, net											98
Income (loss) from continuing operations before income taxes											36
Income taxes											26
Net income											10
Assets		7,335									7,335	7,335
Payments to Acquire Property, Plant, and Equipment											489
Sales Revenue, Services, Other	[5]										0
Operating Segments [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization						152								624		526
Operating Expenses						1,048								4,308		4,203
Interest expense, net						65								280		269
Income (loss) from continuing operations before income taxes						36								481		380
Income taxes						17								163		138
Payments to Acquire Property, Plant, and Equipment						273								1,230		1,223
Operating Segments [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	[6],[8]											0		0		0
Electric operating revenues	[6],[8]											3,506		0		0
Natural gas operating revenues	[6],[8]											92		0		0
Other Operating Income	[6],[8]											0		0		0
Revenue from Purchased Oil and Gas	[6],[8]											0		0		0
Depreciation and amortization											515	515	[8]	0	[8]	0	[8]
Operating Expenses											3,549	3,549	[6],[8]	0	[6],[8]	0	[6],[8]
Equity in earnings (losses) of unconsolidated affiliates	[8]															0
Income (Loss) from Equity Method Investments	[8]											0		0
Interest expense, net											195	195	[8]	0	[8]	0	[8]
Income (loss) from continuing operations before income taxes											(58)	(58)	[8]	0	[8]	0	[8]
Income taxes											3	3	[8]	0	[8]	0	[8]
Net income	[8]											(61)		0		0
Assets	[8]	21,025					0				21,025	21,025		0
Payments to Acquire Property, Plant, and Equipment											1,008	1,008	[8]	0	[8]	0	[8]
Sales Revenue, Services, Other	[6],[8]											45		0		0
Operating Segments [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	[9]											15,390		15,944		14,533
Electric operating revenues	[9]											0		0		0
Natural gas operating revenues	[9]											0		0		0
Other Operating Income	[9]											215		758		155
Revenue from Purchased Oil and Gas	[9]											2,146		2,433		2,705
Depreciation and amortization	[9]											1,879		1,054		967
Operating Expenses	[1],[9]											16,856		16,872		16,923
Equity in earnings (losses) of unconsolidated affiliates	[9]															(20)
Income (Loss) from Equity Method Investments	[9]											(25)		(8)
Interest expense, net	[9]											364		365		356
Income (loss) from continuing operations before income taxes	[9]											873		1,850		1,226
Income taxes	[9]											290		502		207
Net income	[9]											558		1,340		1,019
Assets	[9]	46,974					46,529				46,974	46,974		46,529
Payments to Acquire Property, Plant, and Equipment	[9]											3,078		3,841		3,012
Sales Revenue, Services, Other	[9]											0		0		0
Operating Segments [Member] | Commonwealth Edison Co [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue												0		0		0
Electric operating revenues												5,254		4,905		4,564
Natural gas operating revenues												0		0		0
Other Operating Income												0		0		0
Revenue from Purchased Oil and Gas												0		0		0
Depreciation and amortization												775		707		687
Operating Expenses	[1]											4,056		3,889		3,586
Equity in earnings (losses) of unconsolidated affiliates																0
Income (Loss) from Equity Method Investments												0		0
Interest expense, net												461		332		321
Income (loss) from continuing operations before income taxes												679		706		676
Income taxes												301		280		268
Net income												378		426		408
Assets		28,335					26,532				28,335	28,335		26,532
Payments to Acquire Property, Plant, and Equipment												2,734		2,398		1,689
Sales Revenue, Services, Other												0		0		0
Operating Segments [Member] | PECO Energy Co [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue												0		0		0
Electric operating revenues												2,531		2,486		2,448
Natural gas operating revenues												463		546		646
Other Operating Income												0		0		0
Revenue from Purchased Oil and Gas												0		0		0
Depreciation and amortization												270		260		236
Operating Expenses	[1]											2,292		2,404		2,522
Equity in earnings (losses) of unconsolidated affiliates																0
Income (Loss) from Equity Method Investments												0		0
Interest expense, net												123		114		113
Income (loss) from continuing operations before income taxes												587		521		466
Income taxes												149		143		114
Net income												438		378		352
Assets		10,831					10,367				10,831	10,831		10,367
Payments to Acquire Property, Plant, and Equipment												686		601		661
Sales Revenue, Services, Other												0		0		0
Operating Segments [Member] | Baltimore Gas and Electric Company [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	[10]											0		0		0
Electric operating revenues	[10]											2,609		2,490		2,460
Natural gas operating revenues	[10]											624		645		705
Other Operating Income	[10]											0		0		0
Revenue from Purchased Oil and Gas	[10]											0		0		0
Depreciation and amortization	[10]											423		366		371
Operating Expenses	[1],[10]											2,683		2,578		2,726
Equity in earnings (losses) of unconsolidated affiliates	[10]															0
Income (Loss) from Equity Method Investments	[10]											0		0
Interest expense, net	[10]											103		99		106
Income (loss) from continuing operations before income taxes	[10]											468		477		351
Income taxes	[10]											174		189		140
Net income	[10]											294		288		211
Assets	[10]	8,704					8,295				8,704	8,704		8,295
Payments to Acquire Property, Plant, and Equipment	[10]											934		719		620
Sales Revenue, Services, Other	[10]											0		0		0
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue												(1,430)		(744)		(760)
Electric operating revenues												(31)		(5)		(5)
Natural gas operating revenues												(13)		(15)		(26)
Other Operating Income												(4)		(1)		(1)
Revenue from Purchased Oil and Gas												0		0		(1)
Operating revenues from affiliates	[8]											5		5		6
Depreciation and amortization												0		0		0
Operating Expenses	[1]											(3,164)		(2,131)		(2,071)
Equity in earnings (losses) of unconsolidated affiliates																0
Income (Loss) from Equity Method Investments												0		0
Interest expense, net												0		0		0
Income (loss) from continuing operations before income taxes												(5)		(5)		(6)
Income taxes												0		0		0
Net income												(5)		(5)		(6)
Assets		(11,334)					(11,728)				(11,334)	(11,334)		(11,728)
Payments to Acquire Property, Plant, and Equipment												0		0		0
Sales Revenue, Services, Other												(1,686)		(1,367)		(1,279)
Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5]					(4)								(2)		(3)
Natural gas operating revenues	[5]					0								0		0
Net income						0								(1)		(1)
Assets							(5,238)							(5,238)
Sales Revenue, Services, Other	[5]					0								0		0
Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues	[5]										(13)
Natural gas operating revenues	[5]										0
Net income											45
Assets		(4,724)									(4,724)	(4,724)
Sales Revenue, Services, Other	[5]										0
Intersegment Eliminations [Member] | Atlantic City Electric Company [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates						1								4		4
Intersegment Eliminations [Member] | Atlantic City Electric Company [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates											2
Intersegment Eliminations [Member] | Delmarva Power and Light Company [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates						2								6		7
Intersegment Eliminations [Member] | Delmarva Power and Light Company [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates											5
Intersegment Eliminations [Member] | Potomac Electric Power Company [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates						1								5		5
Intersegment Eliminations [Member] | Potomac Electric Power Company [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates											4
Intersegment Eliminations [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates						0								0		0
Intersegment Eliminations [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates											45	45	[1],[8]	0	[1],[8]	0	[1],[8]
Intersegment Eliminations [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates												1,428		745	[8],[9]	762	[8],[9]
Intersegment Eliminations [Member] | Commonwealth Edison Co [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates												15		4	[8]	4	[8]
Intersegment Eliminations [Member] | PECO Energy Co [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[8]													2		2
Intersegment Eliminations [Member] | Baltimore Gas and Electric Company [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[8],[10]													14		25
Intersegment Eliminations [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[1]											1,647	[10]	1,367	[8]	1,280	[8]
Intersegment Eliminations [Member] | Corporate and Other [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[7]					0								0		0
Intersegment Eliminations [Member] | Corporate and Other [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[7]										47
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates												10		(2)		(13)
Intersegment Eliminations [Member] | Segment Elimination [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[8]											(3,159)		(2,127)		(2,067)
Intersegment Eliminations [Member] | Segment Elimination [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates						(4)								(15)		(16)
Depreciation and amortization						(4)								0		(1)
Operating Expenses						(3)								0		(1)
Interest expense, net						(2)								(1)		0
Income (loss) from continuing operations before income taxes						(118)								(29)		(435)
Income taxes						0								27		178
Payments to Acquire Property, Plant, and Equipment						0								0		0
Intersegment Eliminations [Member] | Segment Elimination [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates											(13)
Depreciation and amortization											0
Operating Expenses											(13)
Interest expense, net											0
Income (loss) from continuing operations before income taxes											71
Income taxes											0
Payments to Acquire Property, Plant, and Equipment											0
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates												1,439		749		779
Equity in earnings (losses) of unconsolidated affiliates												(25)		(8)		0
Income (Loss) from Equity Method Investments										$ 19		0		0		(20)
Income (loss) from continuing operations before income taxes												873		1,850		1,226
Income taxes												290		502		207
Net income												558		1,340		1,019
Assets	[11]	46,974					46,529				46,974	46,974		46,529
Utilities Operating Expense, Taxes	[3]											122		105		89
Payments to Acquire Property, Plant, and Equipment												3,078		3,841		3,012
Exelon Generation Co L L C [Member] | PECO Energy Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[12]											290		224		198
Exelon Generation Co L L C [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[13]											608		502		387
Exelon Generation Co L L C [Member] | Commonwealth Edison Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[14]											47		18		176
Exelon Generation Co L L C [Member] | Potomac Electric Power Company [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[13]											295
Exelon Generation Co L L C [Member] | Delmarva Power and Light Company [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[13]											154
Exelon Generation Co L L C [Member] | Atlantic City Electric Company [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[13]											37
Exelon Generation Co L L C [Member] | Intersegment Eliminations [Member] | Commonwealth Edison Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[14]															7
Commonwealth Edison Co [Member]
Segment Reporting Information [Line Items]
Electric operating revenues												5,239		4,901		4,560
Operating revenues from affiliates												15		4		4
Income (Loss) from Equity Method Investments												0		0
Income taxes												301		280		268
Net income		80	$ 37	$ 145	$ 115		87	$ 149	$ 99	$ 90		378		426		408
Assets		28,335					26,532				28,335	28,335		26,532
Utilities Operating Expense, Taxes	[3]											242		236		238
Payments to Acquire Property, Plant, and Equipment												2,734		2,398		1,689
Commonwealth Edison Co [Member] | PECO Energy Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates												1
PECO Energy Co [Member]
Segment Reporting Information [Line Items]
Electric operating revenues												2,524		2,485		2,446
Natural gas operating revenues												462		545		646
Operating revenues from affiliates												8		2		2
Income (Loss) from Equity Method Investments												0		0
Income (loss) from continuing operations before income taxes												587		521		466
Income taxes												149		143		114
Net income												438		378		352
Assets		10,831					10,367				10,831	10,831		10,367
Utilities Operating Expense, Taxes	[3]											136		133		128
Payments to Acquire Property, Plant, and Equipment												686		601		661
PECO Energy Co [Member] | Commonwealth Edison Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates												1
PECO Energy Co [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates												8
Baltimore Gas and Electric Company [Member]
Segment Reporting Information [Line Items]
Electric operating revenues												2,603		2,490		2,460
Natural gas operating revenues												609		631		680
Operating revenues from affiliates												21		14		25
Income (Loss) from Equity Method Investments												0		0
Income (loss) from continuing operations before income taxes												468		477		351
Income taxes												174		189		140
Net income												294		288		211
Assets	[15]	8,704					8,295				8,704	8,704		8,295
Utilities Operating Expense, Taxes	[3]											85		85		86
Payments to Acquire Property, Plant, and Equipment												934		719		620
Baltimore Gas and Electric Company [Member] | PECO Energy Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates												1
Baltimore Gas and Electric Company [Member] | Commonwealth Edison Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates												1
Pepco Holdings LLC [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues						1,096								4,770		4,614
Natural gas operating revenues						57								165		194
Operating revenues from affiliates						0								0		0
Income (Loss) from Equity Method Investments						0								0
Income (loss) from continuing operations before income taxes						36								481		380
Income taxes						17								163		138
Net income						19								327		242
Assets	[16]						16,188							16,188
Utilities Operating Expense, Taxes	[3]					78								326		324
Payments to Acquire Property, Plant, and Equipment						$ 273								1,230		1,223
Pepco Holdings LLC [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric operating revenues											3,506
Natural gas operating revenues											92
Operating revenues from affiliates											45
Income (Loss) from Equity Method Investments											0
Income (loss) from continuing operations before income taxes											(58)
Income taxes											3
Net income											(61)
Assets	[16]	21,025									21,025	21,025
Utilities Operating Expense, Taxes	[3]										253
Payments to Acquire Property, Plant, and Equipment											1,008
Potomac Electric Power Company [Member]
Segment Reporting Information [Line Items]
Electric operating revenues												2,181		2,124		2,050
Operating revenues from affiliates												5		5		5
Income (Loss) from Equity Method Investments												0		0
Income (loss) from continuing operations before income taxes												83		289		264
Income taxes												41		102		93
Net income												42		187		171
Assets		7,335					6,908				7,335	7,335		6,908
Utilities Operating Expense, Taxes	[3]											312		308		307
Payments to Acquire Property, Plant, and Equipment												586		544		567
Delmarva Power and Light Company [Member]
Segment Reporting Information [Line Items]
Electric operating revenues												1,122		1,132		1,081
Natural gas operating revenues												148		164		194
Operating revenues from affiliates												7		6		7
Income (Loss) from Equity Method Investments												0		0
Income (loss) from continuing operations before income taxes												13		125		169
Income taxes												22		49		65
Net income												(9)		76		104
Assets		4,153					3,969				4,153	4,153		3,969
Utilities Operating Expense, Taxes	[3]											18		18		17
Payments to Acquire Property, Plant, and Equipment												349		352		352
Atlantic City Electric Company [Member]
Segment Reporting Information [Line Items]
Electric operating revenues												1,254		1,291		1,206
Operating revenues from affiliates												3		4		4
Income (Loss) from Equity Method Investments												0		0
Income (loss) from continuing operations before income taxes												(46)		73		76
Income taxes												(4)		33		30
Net income												(42)		40		46
Assets	[17]	$ 3,457					$ 3,387				$ 3,457	3,457		3,387
Utilities Operating Expense, Taxes	[3]											0		0		0
Payments to Acquire Property, Plant, and Equipment												$ 311		$ 300		$ 225
[1]	d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
[2]	Exelon’s consolidated assets include $8,893 million and $8,268 million at December 31, 2016 and December 31, 2015, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,356 million and $3,264 million at December 31, 2016 and December 31, 2015, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2–Variable Interest Entities.
[3]	Generation’s utility tax represents gross receipts tax related to its retail operations and ComEd’s, PECO’s, BGE’s, Pepco's, DPL's and ACE's utility taxes represent municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[4]	The intersegment profit associated with the sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in operating revenues in the Consolidated Statements of Operations. See Note 3—Regulatory Matters for additional information.
[5]	Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 25 — Supplemental Financial Information for total utility taxes for the year ended December 31, 2016 and 2015
[6]	(c)For the years ended December 31, 2016, 2015 and 2014, utility taxes of $122 million, $105 million and $89 million, respectively, are included in revenues and expenses for Generation. For the years ended December 31, 2016, 2015 and 2014, utility taxes of $242 million, $236 million and $238 million, respectively, are included in revenues and expenses for ComEd. For the years ended December 31, 2016, 2015 and 2014, utility taxes of $136 million, $133 million and $128 million, respectively, are included in revenues and expenses for PECO. For the years ended December 31, 2016, 2015 and 2014, utility taxes of $85 million, $85 million and $86 million are included in revenues and expenses for BGE, respectively.
[7]	Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities. For the predecessor periods presented, Other includes the activity of PHI’s unregulated businesses which were distributed to Exelon and Generation as a result of the PHI Merger.
[8]	Amounts included represent activity for PHI's successor period, March 24, 2016 through December 31, 2016. PHI includes the three reportable segments: Pepco, DPL and ACE. See tables below for PHI's predecessor periods, including Pepco, DPL and ACE, for January 1, 2016 to March 23, 2016 and for the years ended December 31, 2015
[9]	Generation includes the six reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. For the year ended December 31, 2016, intersegment revenues for Generation include revenue from sales to PECO of $290 million, sales to BGE of $608 million, sales to Pepco of $295 million, sales to DPL of $154 million and sales to ACE of $37 million in the Mid-Atlantic region, and sales to ComEd of $47 million in the Midwest region, which eliminate upon consolidation. For the year ended December 31, 2015, intersegment revenues for Generation include revenue from sales to PECO of $224 million and sales to BGE of $502 million in the Mid-Atlantic region, and sales to ComEd of $18 million in the Midwest region, which eliminate upon consolidation. For the year ended December 31, 2014, intersegment revenues for Generation include revenue from sales to PECO of $198 million and sales to BGE of $387 million in the Mid-Atlantic region, and sales to ComEd of $176 million in the Midwest region, net of $7 million related to the unrealized mark-to-market losses related to the ComEd swap, which eliminate upon consolidation.
[10]	(b)Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities.
[11]	Generation’s consolidated assets include $8,817 million and $8,235 million at December 31, 2016 and 2015, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,170 million and $3,135 million at December 31, 2016 and 2015, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 2–Variable Interest Entities.
[12]	Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has a ten-year agreement with PECO to sell solar AECs. See Note 3—Regulatory Matters for additional information.
[13]	Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs. See Note 3—Regulatory Matters for additional information.
[14]	Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs to ComEd. In addition, Generation had revenue from ComEd associated with the settled portion of the financial swap contract established as part of the Illinois Settlement. See Note 3—Regulatory Matters for additional information.
[15]	BGE’s consolidated assets include $26 million and $26 million at December 31, 2016 and December 31, 2015, respectively, of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $42 million and $122 million at December 31, 2016 and December 31, 2015, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 2 - Variable Interest Entities.
[16]	PHI’s consolidated total assets include $49 million and $30 million at December 31, 2016 and 2015, respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $143 million and $172 million at December 31, 2016 and 2015, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 2 - Variable Interest Entities.
[17]	ACE’s consolidated assets include $32 million and $30 million at December 31, 2016 and 2015, respectively, of ACE’s consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated liabilities include $126 million and $172 million at December 31, 2016 and 2015, respectively, of ACE’s consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 2 - Variable Interest Entities.

Segment Information - Generatio

Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues		$ 7,875	$ 9,002	$ 6,910	$ 7,573	$ 6,702	$ 7,401	$ 6,514	$ 8,830	$ 31,360	$ 29,447	$ 27,429
Operating revenues from affiliates										10	9	23
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues										6,179	5,900	5,259
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues										4,412	4,710	4,475
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues										1,769	2,212	1,422
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues										1,156	985	843
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues										837	857	935
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	[1]									907	1,102	1,309
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues										15,260	15,766	14,243
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	[2]									2,491	3,369	3,150
Derivative, Loss on Derivative										(41)		(591)
Derivative, Gain on Derivative											257
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues										17,751	19,135	17,393
Scenario, Adjustment [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates											(284)
Scenario, Adjustment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates											284
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	[3]									6,212	5,974	5,414
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	[3]									4,402	4,712	4,488
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	[3]									1,778	2,217	1,468
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	[3]									1,198	996	846
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	[3]									831	863	938
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	[1],[3]									969	1,182	1,379
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	[3]									15,390	15,944	14,533
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	[2],[3]									2,361	3,191	2,860
Amortization of intangible assets related to commodity contracts										52	7	289
Derivative, Loss on Derivative										(500)		(174)
Derivative, Gain on Derivative											203
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	[3]									17,751	19,135	17,393
Operating Segments [Member] | Scenario, Adjustment [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues											284
Operating Segments [Member] | Scenario, Adjustment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues											(284)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[4]									5	5	6
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates										(33)	(74)	(155)
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates										10	(2)	(13)
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates										(9)	(5)	(46)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates										(42)	(11)	(3)
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates										6	(6)	(3)
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[1]									(62)	(80)	(70)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates										(130)	(178)	(290)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[2]									130	178	290
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates										$ 0	$ 0	$ 0
[1]	(b)Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants
[2]	(c)Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $52 million decrease to revenues, a $7 million increase to revenues, and a $289 million decrease to revenues for the amortization of intangible assets related to commodity contracts recorded at fair value for the years ended December 31, 2016, 2015, and 2014, respectively, unrealized mark-to-market losses of $500 million, gains of $203 million, and losses of $174 million for the years ended December 31, 2016, 2015, and 2014, respectively, and elimination of intersegment revenues.
[3]	(a)On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, beginning on April 1, 2014, CENG's revenues are included on a fully consolidated basis.
[4]	Amounts included represent activity for PHI's successor period, March 24, 2016 through December 31, 2016. PHI includes the three reportable segments: Pepco, DPL and ACE. See tables below for PHI's predecessor periods, including Pepco, DPL and ACE, for January 1, 2016 to March 23, 2016 and for the years ended December 31, 2015

Segment Information - Genera200

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Scenario, Adjustment [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense, Total				$ 19
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense, Total		$ 3,317	$ 3,571	3,431
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense, Total		2,971	2,892	2,599
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense, Total		438	461	351
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense, Total		742	634	483
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense, Total		281	293	317
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense, Total	[1]	336	250	327
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense, Total		8,085	8,101	7,508
Generation Reportable Segments Total [Member] | Scenario, Adjustment [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers				11
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity				8
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense, Total	[2]	836	1,013	(40)
Amortization Of Intangible Assets Related To Commodity Contracts For Revenue Net Purchased Power And Fuel		(57)	8	(124)
Derivative, Gain on Derivative			(257)
Derivative, Loss on Derivative		41		591
Generation All Other Segments [Member] | Scenario, Adjustment [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers				(11)
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity				(8)
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense, Total		8,921	9,114	7,468
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers	[3]	3,282	3,556	3,544
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers	[3]	2,969	2,912	2,607
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers	[3]	467	519	450
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers	[3]	761	584	439
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers	[3]	412	425	573
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers	[1],[3]	483	440	517
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers	[3]	8,374	8,436	8,130
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers	[2],[3]	547	678	(662)
Derivative, Gain on Derivative			(203)
Derivative, Loss on Derivative		500		174
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from external customers	[3]	8,921	9,114	7,468
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity		35	15	(113)
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity		2	(20)	(8)
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity		(29)	(58)	(99)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity		(19)	50	44
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity		(131)	(132)	(256)
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity	[1]	(147)	(190)	(190)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity		(289)	(335)	(622)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity	[2]	289	335	622
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue net of purchased power and fuel expense from transactions with other operating segments of the same entity		$ 0	$ 0	$ 0
[1]	(b)Includes purchases and sales from third parties and affiliated sales to the Utility Registrants.
[2]	(c)Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $57 million decrease in RNF, a $8 million increase in RNF, and a $124 million decrease in RNF for the amortization of intangible assets related to commodity contracts recorded at fair value for the years ended December 31, 2016, 2015, and 2014, respectively, unrealized mark-to-market losses of $41 million, gains of $257 million, and losses of $591 million for the years ended December 31, 2016, 2015, and 2014, respectively, accelerated nuclear fuel amortization associated with the initial early retirement decision for Clinton and Quad Cities as discussed in Note 9 - Early Nuclear Plant Retirements of $60 million for the year ended December 31, 2016, and the elimination of intersegment revenues net of purchased power and fuel expense.
[3]	(a)On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, beginning on April 1, 2014, CENG's revenues net of purchased power and fuel expense are included on a fully consolidated basis.

Related Party Transactions - Re

Related Party Transactions - Related Party Transactions included in Consolidated Income Statement (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended	12 Months Ended
		Mar. 23, 2016	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Operating revenues from affiliates					$ 10		$ 9	$ 23
Interest Expense, Related Party					41		41	41
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions					0		0	(20)
Income (Loss) from Equity Method Investments					(24)		(7)	0
Cash dividends paid to parent					1,166		1,105	1,065
Adjustments to Additional Paid in Capital, Other							0
Utilities Operating Expense, Purchased Power					0		0	531
Other Cost and Expense, Operating					10,048		8,322	8,568
PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[1]				1		1	1
Constellation Energy Nuclear Group Llc Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[2]				0		0	17
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	[2]				0		0	(19)
Utilities Operating Expense, Purchased Power	[3]				0		0	282
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[1]				4		4	5
Keystone Fuels LLC Affiliate [Member]
Related Party Transaction [Line Items]
Utilities Operating Expense, Purchased Power	[4]				0		0	138
Conemaugh Fuels LLC Affiliate [Member]
Related Party Transaction [Line Items]
Utilities Operating Expense, Purchased Power	[4]				0		0	99
SafeHarborWaterPowerCorp [Member]
Related Party Transaction [Line Items]
Utilities Operating Expense, Purchased Power	[4]				0		0	12
PECO Trust Three Affiliate [Member]
Related Party Transaction [Line Items]
Interest Expense, Related Party					6		6	6
ComEd Financing Three Affiliate [Member]
Related Party Transaction [Line Items]
Interest Expense, Related Party					13		13	13
PECO Trust Four Affiliate [Member]
Related Party Transaction [Line Items]
Interest Expense, Related Party					6		6	6
BGE Capital Trust II [Member]
Related Party Transaction [Line Items]
Interest Expense, Related Party					16		16	16
Other Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					5		4	0
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions					1		1	0
Qualifying Facilities And Domestic Power Projects Affiliate [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions					(25)		(8)	(1)
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					15		4	4
Operating and maintenance from affiliates					227		195	166
Interest Expense, Related Party					13		13	13
Income (Loss) from Equity Method Investments					0		0
Cash dividends paid to parent					369		299	307
Contributions from parent					315		202	273
Adjustments to Additional Paid in Capital, Other					315		202	273
Utilities Operating Expense, Purchased Power					1,411		1,301	1,001
Other Cost and Expense, Operating					1,303		1,372	1,263
Commonwealth Edison Co [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					7		4	4
Utilities Operating Expense, Purchased Power	[5]				47		18	176
Commonwealth Edison Co [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					1
Operating and maintenance from affiliates	[6]				1
Commonwealth Edison Co [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Cash dividends paid to parent					369		299	307
Adjustments to Additional Paid in Capital, Other					315		202	273
Commonwealth Edison Co [Member] | Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					1
Operating and maintenance from affiliates					1
Commonwealth Edison Co [Member] | ComEd Financing Three Affiliate [Member]
Related Party Transaction [Line Items]
Interest Expense, Related Party					13		13	13
Commonwealth Edison Co [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					6
Operating and maintenance from affiliates	[6]				225		195	166
Related Party Transaction Capitalized Costs Support Services	[6]				112		103	77
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					3		4	4
Operating and maintenance from affiliates					18		3	3
Income (Loss) from Equity Method Investments					0		0
Cash dividends paid to parent					63		12	26
Contributions from parent					139		95	0
Adjustments to Additional Paid in Capital, Other					139		95
Utilities Operating Expense, Purchased Power					614		708	664
Other Cost and Expense, Operating					410		268	247
Atlantic City Electric Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Utilities Operating Expense, Purchased Power	[7]				37		0	0
Atlantic City Electric Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					2		2	1
Other Cost and Expense, Operating					155		143	124
Atlantic City Electric Company [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Contribution from member					139		95	0
Cash dividends paid to parent					63		12	26
Atlantic City Electric Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					1		2	3
Operating and maintenance from affiliates					3		3	3
Atlantic City Electric Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	[8]				15		0	0
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					21		14	25
Operating and maintenance from affiliates					132		118	103
Interest Expense, Related Party					16		16	16
Income (Loss) from Equity Method Investments					0		0
Cash dividends paid to parent					179		158	0
Contributions from parent					61		7	0
Adjustments to Additional Paid in Capital, Other					61		7
Utilities Operating Expense, Purchased Power					528		602	733
Other Cost and Expense, Operating					605		565	614
Baltimore Gas and Electric Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[9]				13		14	25
Utilities Operating Expense, Purchased Power	[10]				604		498	382
Baltimore Gas and Electric Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					1
Operating and maintenance from affiliates					1		0
Baltimore Gas and Electric Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					1
Operating and maintenance from affiliates					1
Baltimore Gas and Electric Company [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Cash dividends paid to parent					179		158	0
Contributions from parent					61		7	0
Baltimore Gas and Electric Company [Member] | BGE Capital Trust II [Member]
Related Party Transaction [Line Items]
Interest Expense, Related Party					16		16	16
Baltimore Gas and Electric Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					6
Operating and maintenance from affiliates	[11]				130		118	103
Related Party Transaction Capitalized Costs Support Services	[11]				36		28	19
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					8		2	2
Operating and maintenance from affiliates					146		110	99
Interest Expense, Related Party					12		12	12
Income (Loss) from Equity Method Investments					0		0
Cash dividends paid to parent					277		279	320
Contributions from parent					18		16	24
Utilities Operating Expense, Purchased Power					598		735	740
Other Cost and Expense, Operating					665		684	767
PECO Energy Co [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[12]				3		2	2
Operating and maintenance from affiliates					2		3	3
Utilities Operating Expense, Purchased Power	[13]				287		220	194
PECO Energy Co [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					1
Operating and maintenance from affiliates					1
PECO Energy Co [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Cash dividends paid to parent					277		279	320
Contributions from parent					18		16	24
PECO Energy Co [Member] | Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					1
Operating and maintenance from affiliates					1
PECO Energy Co [Member] | PECO Trust Three Affiliate [Member]
Related Party Transaction [Line Items]
Interest Expense, Related Party					6		6	6
PECO Energy Co [Member] | PECO Trust Four Affiliate [Member]
Related Party Transaction [Line Items]
Interest Expense, Related Party					6		6	6
PECO Energy Co [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					3
Operating and maintenance from affiliates	[14]				142		107	96
Related Party Transaction Capitalized Costs Support Services	[14]				57		40	39
Pepco Holdings LLC [Member] | Predecessor [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates		$ 0					0	0
Operating and maintenance from affiliates		0					0	0
Income (Loss) from Equity Method Investments		0					0
Cash distribution paid to member		0					0	0
Cash dividends paid to parent		0					275	272
Utilities Operating Expense, Purchased Power		471					1,986	1,940
Other Cost and Expense, Operating		$ 294					1,156	1,183
Pepco Holdings LLC [Member] | Successor [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates				$ 45
Operating and maintenance from affiliates				89
Income (Loss) from Equity Method Investments				0
Cash distribution paid to member				273
Cash dividends paid to parent				0
Contributions from parent				1,251
Utilities Operating Expense, Purchased Power				925
Other Cost and Expense, Operating				1,144
Pepco Holdings LLC [Member] | Exelon Generation Co LLC Affiliate [Member] | Successor [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates				1
Utilities Operating Expense, Purchased Power				486
Pepco Holdings LLC [Member] | PHI Service Co Affiliate [Member] | Successor [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates				3
Contributions from parent				1,251
Pepco Holdings LLC [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Cash dividends paid to parent				273
Pepco Holdings LLC [Member] | Exelon Business Services Co Affiliate [Member] | Successor [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates				44
Operating and maintenance from affiliates				$ 86
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					5		5	5
Operating and maintenance from affiliates					35		4	4
Income (Loss) from Equity Method Investments					0		0
Cash dividends paid to parent					136		146	86
Contributions from parent					187		112	80
Adjustments to Additional Paid in Capital, Other					187		112	80
Utilities Operating Expense, Purchased Power					411		719	735
Other Cost and Expense, Operating					607		435	386
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member]
Related Party Transaction [Line Items]
Other Cost and Expense, Operating					302		266	250
Potomac Electric Power Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					1	[15]	0	0
Utilities Operating Expense, Purchased Power	[16]				295		0	0
Potomac Electric Power Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					4		5	5
Operating and maintenance from affiliates	[17]				4		4	4
Other Cost and Expense, Operating					263		240	220
Potomac Electric Power Company [Member] | Pepco Energy Services Affiliate [Member]
Related Party Transaction [Line Items]
Other Cost and Expense, Operating					39		26	30
Potomac Electric Power Company [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Cash dividends paid to parent					136		146	86
Contributions from parent					187		112	80
Potomac Electric Power Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	[17]				31		0	0
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					7		6	7
Operating and maintenance from affiliates					19		1	1
Income (Loss) from Equity Method Investments					0		0
Cash dividends paid to parent					54		92	100
Contributions from parent					152		75	130
Adjustments to Additional Paid in Capital, Other					152		75	130
Utilities Operating Expense, Purchased Power					369		555	536
Other Cost and Expense, Operating					422		303	266
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member]
Related Party Transaction [Line Items]
Other Cost and Expense, Operating					202		182	163
Delmarva Power and Light Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Utilities Operating Expense, Purchased Power	[18]				154		0	0
Delmarva Power and Light Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					5		5	6
Operating and maintenance from affiliates	[19]				1		1	1
Other Cost and Expense, Operating					194		179	163
Delmarva Power and Light Company [Member] | Pepco Energy Services Affiliate [Member]
Related Party Transaction [Line Items]
Other Cost and Expense, Operating					8		3	0
Delmarva Power and Light Company [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Cash dividends paid to parent					54		92	100
Contributions from parent					152		75	130
Delmarva Power and Light Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					2		1	1
Delmarva Power and Light Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	[19]				18		0	0
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					1,439		749	779
Operating and maintenance from affiliates					663		620	623
Interest Expense, Related Party					39		43	53
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions					(25)		(8)	0
Income (Loss) from Equity Method Investments			$ 19		0		0	(20)
Cash distribution paid to member					922		2,474	645
Contribution from member					142		47	53
Adjustments to Additional Paid in Capital, Other								170
Utilities Operating Expense, Purchased Power					12		14	557
Other Cost and Expense, Operating					4,978		4,688	4,943
Exelon Generation Co L L C [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[20]				47		18	176
Operating and maintenance from affiliates	[21]				7		4	3
Utilities Operating Expense, Purchased Power					0		0	1
Exelon Generation Co L L C [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[22]				290		224	198
Operating and maintenance from affiliates	[21]				3		2	2
Exelon Generation Co L L C [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[23]				608		502	387
Operating and maintenance from affiliates	[21]				1
Utilities Operating Expense, Purchased Power					12		14	25
Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group Llc Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[24]				0		0	17
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	[24]				0		0	(19)
Utilities Operating Expense, Purchased Power	[25]				0		0	282
Exelon Generation Co L L C [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Interest Expense, Related Party					39		43	53
Cash distribution paid to member					922		2,474	645
Contribution from member					142		47	53
Exelon Generation Co L L C [Member] | Keystone Fuels LLC Affiliate [Member]
Related Party Transaction [Line Items]
Utilities Operating Expense, Purchased Power	[26]				0		0	138
Exelon Generation Co L L C [Member] | Conemaugh Fuels LLC Affiliate [Member]
Related Party Transaction [Line Items]
Utilities Operating Expense, Purchased Power	[26]				0		0	99
Exelon Generation Co L L C [Member] | SafeHarborWaterPowerCorp [Member]
Related Party Transaction [Line Items]
Utilities Operating Expense, Purchased Power					0		0	12
Exelon Generation Co L L C [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					6		4	0
Exelon Generation Co L L C [Member] | Qualifying Facilities And Domestic Power Projects Affiliate [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions					(25)		(8)	(1)
Exelon Generation Co L L C [Member] | Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates					1
Exelon Generation Co L L C [Member] | Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[23]				295
Operating and maintenance from affiliates					1
Exelon Generation Co L L C [Member] | Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[23]				154
Exelon Generation Co L L C [Member] | Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates	[23]				37
Exelon Generation Co L L C [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Operating revenues from affiliates					2		1	1
Operating and maintenance from affiliates	[27]				650		614	618
Related Party Transaction Capitalized Costs Support Services	[6]				$ 98		$ 76	$ 91
[1]	The intersegment profit associated with the sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in operating revenues in the Consolidated Statements of Operations. See Note 3—Regulatory Matters for additional information.
[2]	Beginning in 2012, Generation entered into a power services agency agreement (PSAA) with the CENG plants, which as of April 1, 2014, was amended and extended until the permanent cessation of power generation by the CENG generation plants. The PSAA is an agreement under which Generation provides scheduling, asset management and billing services to the CENG plants for a specified monthly fee. The charges for services reflect the cost of the services. On April 1, 2014, Generation and CENG entered into a Nuclear Operating Services Agreement (NOSA) pursuant to which Generation will operate the CENG nuclear generation fleet owned by CENG subsidiaries and provide corporate and administrative services for the remaining life of the CENG nuclear plants as if they were part of the Generation nuclear fleet. For further information regarding the Investment in CENG, see Note 5—Investment in Constellation Energy Nuclear Group, LLC.
[3]	CENG owns 100% of four nuclear units in Maryland and New York and 82% of Nine Mile Point Unit 2 in New York. Beginning in 2012, Generation had a PPA under which it purchased 85% of the nuclear plant output owned by CENG that was not sold to third parties under pre-existing unit-contingent PPAs through 2014. Beginning on January 1, 2015 and continuing to the end of the life of the respective plants, Generation will purchase on a unit-contingent basis 50.01% of the nuclear plant output owned by CENG and a subsidiary of EDF will purchase on a unit-contingent basis 49.99% of the nuclear plant output owned by CENG (EDF PPA) not sold to third parties. Beginning April 1, 2014, sales to Generation are eliminated in consolidation. For further information regarding the Investment in CENG, see Note 5—Investment in Constellation Energy Nuclear Group, LLC.
[4]	During 2014, Generation closed the sale of Safe Harbor Water Power Corporation, Keystone Fuels, LLC, and Conemaugh Fuels LLC. Generation recorded purchase power and fuel costs from affiliates related to these generating assets during the time these assets were still partially owned by Generation. See Note 4—Mergers, Acquisitions, and Dispositions for more information.
[5]	ComEd procures a portion of its electricity supply requirements from Generation under an ICC-approved RFP contract. ComEd also purchases RECs from Generation. In addition, purchased power expense includes the settled portion of the financial swap contract with Generation, which expired in 2013. See Note 3—Regulatory Matters and Note 13—Derivative Financial Instruments for additional information.
[6]	ComEd receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[7]	.
[8]	ACE receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[9]	BGE provides energy to Generation for Generation’s own use.
[10]	BGE procures a portion of its electricity and gas supply requirements from Generation under its MDPSC-approved market-based SOS and gas commodity programs. See Note 3—Regulatory Matters for additional information.
[11]	BGE receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[12]	PECO provides energy to Generation for Generation’s own use.
[13]	PECO purchases electric supply from Generation under contracts executed through its competitive procurement process. In addition, PECO has five-year and ten-year agreements with Generation to purchase non-solar and solar AECs, respectively. See Note 3—Regulatory Matters for additional information on AECs.
[14]	PECO receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[15]	Pepco provides energy to Generation for Generation’s own use.
[16]	Pepco procures a portion of its electricity and gas supply requirements from Generation under its MDPSC and DPSC approved market based SOS and gas commodity programs. See Note 3—Regulatory Matters for additional information.
[17]	Pepco receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[18]	DPL procures a portion of its electricity and gas supply requirements from Generation under its MDPSC and DPSC approved market based SOS and gas commodity programs. See Note 3—Regulatory Matters for additional information.
[19]	DPL receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[20]	Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs to ComEd. In addition, Generation had revenue from ComEd associated with the settled portion of the financial swap contract established as part of the Illinois Settlement. See Note 3—Regulatory Matters for additional information.
[21]	Generation requires electricity for its own use at its generating stations. Generation purchases electricity and distribution and transmission services from PECO and BGE and only distribution and transmission services from ComEd for the delivery of electricity to its generating stations.
[22]	Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has a ten-year agreement with PECO to sell solar AECs. See Note 3—Regulatory Matters for additional information.
[23]	Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs. See Note 3—Regulatory Matters for additional information.
[24]	Beginning in 2012, Generation entered into a power services agency agreement (PSAA) with the CENG plants, which as of April 1, 2014, was amended and extended until the permanent cessation of power generation by the CENG generation plants. The PSAA is an agreement under which Generation provides scheduling, asset management and billing services to the CENG plants for a specified monthly fee. The charges for services reflect the cost of the services. On April 1, 2014, Generation and CENG entered into a Nuclear Operating Services Agreement (NOSA) pursuant to which Generation will operate the CENG nuclear generation fleet owned by CENG subsidiaries and provide corporate and administrative services for the remaining life of the CENG nuclear plants as if they were part of the Generation nuclear fleet. For further information regarding the Investment in CENG, see Note 5—Investment in Constellation Energy Nuclear Group, LLC.
[25]	CENG owns 100% of four nuclear units in Maryland and New York and 82% of Nine Mile Point Unit 2 in New York. Beginning in 2012, Generation had a PPA under which it purchased 85% of the nuclear plant output owned by CENG that was not sold to third parties under pre-existing unit-contingent PPAs through 2014. Beginning on January 1, 2015 and continuing to the end of the life of the respective plants, Generation will purchase on a unit-contingent basis 50.01% of the nuclear plant output owned by CENG and a subsidiary of EDF will purchase on a unit-contingent basis 49.99% of the nuclear plant output owned by CENG (EDF PPA) not sold to third parties. Beginning April 1, 2014, sales to Generation are eliminated in consolidation. For further information regarding the Investment in CENG, see Note 5—Investment in Constellation Energy Nuclear Group, LLC.
[26]	During 2014, Generation closed the sale of Safe Harbor Water Power Corporation, Keystone Fuels, LLC, and Conemaugh Fuels LLC. Generation recorded purchase power and fuel costs from affiliates related to these generating assets during the time these assets were still partially owned by Generation. See Note 4—Mergers, Acquisitions, and Dispositions for more information.
[27]	Generation receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.

Related Party Transactions -202

Related Party Transactions - Related Party Transactions included in Consolidated Balance Sheet (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015		Dec. 31, 2012	Dec. 31, 2016
Related Party Transaction [Line Items]
Total payables to affiliates (current)		$ 0			$ (706)
Due to Related Parties, Noncurrent		641			641
Accounts Payable, Related Parties, Current		8			8
BGE Capital Trust II [Member]
Related Party Transaction [Line Items]
Due to Related Parties, Noncurrent		252			252
Accounts Payable, Related Parties, Current		3			3
ComEd Financing Three Affiliate [Member]
Related Party Transaction [Line Items]
Due to Related Parties, Noncurrent		205			205
Accounts Payable, Related Parties, Current		4			4
PECO Trust Three Affiliate [Member]
Related Party Transaction [Line Items]
Due to Related Parties, Noncurrent		81			81
Accounts Payable, Related Parties, Current		1			1
PECO Trust Four Affiliate [Member]
Related Party Transaction [Line Items]
Due to Related Parties, Noncurrent		103			103
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		30			74
Potomac Electric Power Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[1]	25			25
Potomac Electric Power Company [Member] | Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current					1
Potomac Electric Power Company [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		0
Potomac Electric Power Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		1			0
Potomac Electric Power Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[2]	0			44
Potomac Electric Power Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[1]	0			4
Potomac Electric Power Company [Member] | Pepco Energy Services Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[3]	4			0
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)		0			3
Accounts Payable, Related Parties, Current		20			38
Delmarva Power and Light Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[4]	19			19
Delmarva Power and Light Company [Member] | Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)					2
Delmarva Power and Light Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		1
Delmarva Power and Light Company [Member] | Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)					1
Delmarva Power and Light Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		0			16
Delmarva Power and Light Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[4]	0			3
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Due to Related Parties, Noncurrent		252			252
Accounts Payable, Related Parties, Current		52			55
Baltimore Gas and Electric Company [Member] | BGE Capital Trust II [Member]
Related Party Transaction [Line Items]
Due to Related Parties, Noncurrent		252			252
Accounts Payable, Related Parties, Current		3			3
Baltimore Gas and Electric Company [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		1			1
Baltimore Gas and Electric Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[5]	31			26
Baltimore Gas and Electric Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[6]	17			22
Baltimore Gas and Electric Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Total payables to affiliates (current)		0			(1)
Baltimore Gas and Electric Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		0			2
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)		2			4
Total receivable from affiliates (noncurrent)		405			438
Due to Related Parties, Noncurrent		184			184
Accounts Payable, Related Parties, Current		55			63
PECO Energy Co [Member] | Voluntary Employee Beneficiary Association Trust [Member]
Related Party Transaction [Line Items]
Prepaid Expense Other, Noncurrent	[7]	2			1
PECO Energy Co [Member] | PECO Trust Three Affiliate [Member]
Related Party Transaction [Line Items]
Due to Related Parties, Noncurrent		81			81
Accounts Payable, Related Parties, Current		1			1
PECO Energy Co [Member] | PECO Trust Four Affiliate [Member]
Related Party Transaction [Line Items]
Due to Related Parties, Noncurrent		103			103
PECO Energy Co [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		1			1
PECO Energy Co [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)		0			2
PECO Energy Co [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Total receivable from affiliates (noncurrent)	[8]	405			438
Accounts Payable, Related Parties, Current	[9]	36			33
PECO Energy Co [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[10]	17			28
PECO Energy Co [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)		2			2
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)		199			356
Total receivable from affiliates (noncurrent)		2,172			2,170
Due to Related Parties, Noncurrent		205			205
Accounts Payable, Related Parties, Current		62			65
Commonwealth Edison Co [Member] | ComEd Financing Three Affiliate [Member]
Related Party Transaction [Line Items]
Due to Related Parties, Noncurrent		205			205
Accounts Payable, Related Parties, Current		4			4
Commonwealth Edison Co [Member] | Voluntary Employee Beneficiary Association Trust [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)		2			2
Prepaid Expense Other, Noncurrent	[11]	11			5
Commonwealth Edison Co [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		2			3
Commonwealth Edison Co [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)		188	[12]		345
Total receivable from affiliates (noncurrent)		0			1
Commonwealth Edison Co [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)		9			9
Total receivable from affiliates (noncurrent)	[13]	2,172			2,169
Accounts Payable, Related Parties, Current	[14]	15			14
Commonwealth Edison Co [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[15]	39			42
Commonwealth Edison Co [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		2			2
Pepco Holdings LLC [Member] | Predecessor [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		0
Pepco Holdings LLC [Member] | Successor [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current					94
Pepco Holdings LLC [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current					4
Pepco Holdings LLC [Member] | Exelon Corporation Affiliate [Member] | Successor [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current					6
Pepco Holdings LLC [Member] | Exelon Generation Co LLC Affiliate [Member] | Successor [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current					74
Pepco Holdings LLC [Member] | Exelon Business Services Co Affiliate [Member] | Successor [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current					10
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		16			29
Atlantic City Electric Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[16]	15			16
Atlantic City Electric Company [Member] | Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current					2
Atlantic City Electric Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		1			0
Atlantic City Electric Company [Member] | Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		0
Atlantic City Electric Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[17]	0			9
Atlantic City Electric Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current		$ 0			2	[16]
Constellation Energy Group LLC [Member] | Electricite De France LLC [Member]
Related Party Transaction [Line Items]
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased		49.99%
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)		$ 83			156
Due to Related Parties, Current		1,252			55
Due to Related Parties, Noncurrent		933			922
Notes Payable, Related Parties, Current		1,252			55
Accounts Payable, Related Parties, Current		104			137
Due to Affiliate, Noncurrent		$ 2,577			2,608
Exelon Generation Co L L C [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)	[18]				5
Exelon Generation Co L L C [Member] | Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)					8
Due to Related Parties, Current					55
Exelon Generation Co L L C [Member] | Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)	[19]				9
Exelon Generation Co L L C [Member] | Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)	[20]				16
Exelon Generation Co L L C [Member] | Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased				85.00%
Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group Llc Affiliate [Member]
Related Party Transaction [Line Items]
Long-term Contract for Purchase of Electric Power, Share of Plant Output Being Purchased		50.01%
Exelon Generation Co L L C [Member] | Exelon Corporation Affiliate [Member]
Related Party Transaction [Line Items]
Due to Related Parties, Current		$ 0
Due to Related Parties, Noncurrent	[21]	933			922
Notes Payable, Related Parties, Current		1,252			0
Accounts Payable, Related Parties, Current	[22]	16			22
Exelon Generation Co L L C [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)		1			1
Accounts Payable, Related Parties, Current		1			7
Exelon Generation Co L L C [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)	[23]	31			26
Exelon Generation Co L L C [Member] | Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)	[24]				44
Exelon Generation Co L L C [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	[18]	78			99
Due to Affiliate, Noncurrent	[18]	0			1
Exelon Generation Co L L C [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)	[25]	15			14
Accounts Payable, Related Parties, Current		9			9
Due to Affiliate, Noncurrent	[26]	2,172			2,169
Exelon Generation Co L L C [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Total receivables from affiliates (current)	[27]	36			33
Due to Affiliate, Noncurrent	[26]	$ 405			$ 438
[1]	Pepco receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[2]	Pepco procures a portion of its electricity and gas supply requirements from Generation under its MDPSC and DPSC approved market based SOS and gas commodity programs. See Note 3—Regulatory Matters for additional information.
[3]	Pepco bills customers on behalf of PES where PES has performed work for certain government agencies under a General Services Administration area-wide agreement on behalf of Pepco.
[4]	DPL receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[5]	BGE procures a portion of its electricity and gas supply requirements from Generation under its MDPSC-approved market-based SOS and gas commodity programs. See Note 3—Regulatory Matters for additional information.
[6]	BGE receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[7]	The voluntary employee beneficiary association trusts covering active employees are included in corporate operations and are funded by the Registrants. A prepayment to the active welfare plans has accumulated due to actuarially determined contribution rates, which are the basis for PECO’s contributions to the plans, being higher than actual claim expense incurred by the plans over time.
[8]	PECO has a long-term receivable from Generation as a result of the nuclear decommissioning contractual construct, whereby, to the extent the assets associated with decommissioning are greater than the applicable ARO at the end of decommissioning, such amounts are due back to PECO for payment to PECO’s customers.
[9]	PECO purchases electric supply from Generation under contracts executed through its competitive procurement process. In addition, PECO has five-year and ten-year agreements with Generation to purchase non-solar and solar AECs, respectively. See Note 3—Regulatory Matters for additional information on AECs.
[10]	PECO receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[11]	The voluntary employee benefit association trusts covering active employees are included in corporate operations and are funded by the Registrants. A prepayment to the active welfare plans has accumulated due to actuarially determined contribution rates, which are the basis for ComEd’s contributions to the plans, being higher than actual claim expense incurred by the plans over time. The prepayment is included in other current assets.
[12]	Represents indemnification from Exelon Corporate related to the like-kind exchange.
[13]	ComEd has a long-term receivable from Generation as a result of the nuclear decommissioning contractual construct for generating facilities previously owned by ComEd. To the extent the assets associated with decommissioning are greater than the applicable ARO at the end of decommissioning, such amounts are due back to ComEd for payment to ComEd’s customers.
[14]	ComEd procures a portion of its electricity supply requirements from Generation under an ICC-approved RFP contract. ComEd also purchases RECs from Generation. In addition, purchased power expense includes the settled portion of the financial swap contract with Generation, which expired in 2013. See Note 3—Regulatory Matters and Note 13—Derivative Financial Instruments for additional information.
[15]	ComEd receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[16]	.
[17]	ACE receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[18]	Generation receives a variety of corporate support services from BSC and PHISCO, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead. A portion of such services is capitalized.
[19]	(f)Generation provides electric supply to ACE under contracts executed through ACE's competitive procurement process. See Note 3—Regulatory Matters for additional information.
[20]	(e)Generation provides a portion of DPL's energy requirements under its MDPSC and DPSC approved market based SOS and gas commodity programs. See Note 3—Regulatory Matters for additional information.
[21]	In connection with the debt obligations assumed by Exelon as part of the Constellation merger, Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable included in Long-term Debt to affiliate on Generation’s Consolidated Balance Sheets and intercompany notes receivable at Exelon Corporate, which are eliminated in consolidation on Exelon’s Consolidated Balance Sheets.
[22]	The balance consists of interest owed to Exelon Corporation related to the senior unsecured notes, as well as, expense related to certain invoices Exelon Corporation processed on behalf of Generation.
[23]	Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs. See Note 3—Regulatory Matters for additional information.
[24]	See Note 3—Regulatory Matters for additional information.(d)Generation provides electric supply to Pepco under contracts executed through Pepco's competitive procurement process approved by the MDPSC and DCPSC. See Note 3—Regulatory Matters for additional information.
[25]	Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs to ComEd. In addition, Generation had revenue from ComEd associated with the settled portion of the financial swap contract established as part of the Illinois Settlement. See Note 3—Regulatory Matters for additional information.
[26]	Generation has long-term payables to ComEd and PECO as a result of the nuclear decommissioning contractual construct whereby, to the extent NDT funds are greater than the underlying ARO at the end of decommissioning, such amounts are due back to ComEd and PECO, as applicable, for payment to their respective customers. See Note 16—Asset Retirement Obligations
[27]	Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has a ten-year agreement with PECO to sell solar AECs. See Note 3—Regulatory Matters for additional information.

Quarterly Data (Unaudited) - Qu

Quarterly Data (Unaudited) - Quarterly Operating Results (Details) - USD ($) $ in Millions	3 Months Ended										9 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016		Mar. 23, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Selected Quarterly Financial Information [Line Items]
Operating Revenues	$ 7,875	$ 9,002	$ 6,910	$ 7,573			$ 6,702	$ 7,401	$ 6,514	$ 8,830		$ 31,360	$ 29,447	$ 27,429
Operating Income (Loss)	714	1,267	647	483			707	1,200	1,134	1,366		3,112	4,409	3,096
Net Income (Loss) Attributable to Common Stockholders	204	490	267	173			309	629	638	693		1,134	2,269	1,623
Net income												1,204	2,250	1,820
Exelon Generation Co L L C [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues	4,388	5,035	3,589	4,739			4,294	4,768	4,232	5,840		17,751	19,135	17,393
Operating Income (Loss)	94	342	(13)	415			230	622	703	719		836	2,275	1,176
Net (Loss) Income Attributable to Membership Interest	(41)	236	(8)	310			154	377	398	443		496	1,372	835
Net income												558	1,340	1,019
Commonwealth Edison Co [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues	1,223	1,497	1,286	1,249			1,196	1,376	1,148	1,185		5,254	4,905	4,564
Operating Income (Loss)	217	389	324	274			217	327	243	230		1,205	1,017	980
Net income	80	37	145	115			87	149	99	90		378	426	408
PECO Energy Co [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues	701	788	664	841			645	740	661	985		2,994	3,032	3,094
Operating Income (Loss)	150	204	152	196			128	154	124	223		702	630	572
Net Income (Loss) Attributable to Common Stockholders	92	122	100	124			79	90	70	139		438	378	352
Net income												438	378	352
Baltimore Gas and Electric Company [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues	812	812	680	929			746	725	628	1,036		3,233	3,135	3,165
Operating Income (Loss)	190	115	59	187			144	110	99	204		550	558	439
Net Income (Loss) Attributable to Common Stockholders	103	54	31	98			74	51	44	106		286	275	198
Net income												294	288	211
Pepco Holdings LLC [Member] | Successor [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues	1,078	1,394	1,066	105	[1]						$ 3,643
Operating Income (Loss)	90	279	136	(411)	[1]						93
Net (Loss) Income Attributable to Membership Interest	30	166	52	(309)	[1]						(61)
Net income											$ (61)
Pepco Holdings LLC [Member] | Predecessor [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues						$ 1,153	1,126	1,336	1,119	1,354			4,935	4,808
Operating Income (Loss)						105	208	184	139	142			673	605
Net (Loss) Income Attributable to Membership Interest						19	130	91	53	53			327	242
Net income						$ 19							327	242
Potomac Electric Power Company [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues	491	635	509	551			488	592	504	545		2,186	2,129	2,055
Operating Income (Loss)	51	132	97	(105)			123	115	83	63		174	385	349
Net Income (Loss) Attributable to Common Stockholders	23	79	49	(108)			59	60	42	26		42	187	171
Net income												42	187	171
Delmarva Power and Light Company [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues	303	331	281	362			296	314	271	421		1,277	1,302	1,282
Operating Income (Loss)	20	72	30	(72)			46	32	24	63		50	165	207
Net Income (Loss) Attributable to Common Stockholders	7	44	12	(72)			21	15	8	32		(9)	76	104
Net income												(9)	76	104
Atlantic City Electric Company [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues	275	421	270	291			291	386	285	334		1,257	1,295	1,210
Operating Income (Loss)	26	83	19	(121)			29	51	25	29		7	134	137
Net Income (Loss) Attributable to Common Stockholders	$ 8	$ 47	$ 3	$ (100)			$ 3	$ 22	$ 6	$ 9		(42)	40	46
Net income												$ (42)	$ 40	$ 46
[1]	Amounts for March 31, 2016 reflect the PHI Successor activity for the period March 24, 2016 to March 31, 2016.

Quarterly Data (Unaudited) -204

Quarterly Data (Unaudited) - Quarterly Per Share Information (Details) - $ / shares shares in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Data [Abstract]
Weighted average common shares outstanding—basic	925	925	924	923	921	913	863	862	924	890	860
Net Income per Basic Share	$ 0.22	$ 0.53	$ 0.29	$ 0.19	$ 0.34	$ 0.69	$ 0.74	$ 0.80
Weighted average common shares outstanding—diluted	928	927	926	925	924	915	866	867	927	893	864
Net Income per Diluted Share	$ 0.22	$ 0.53	$ 0.29	$ 0.19	$ 0.33	$ 0.69	$ 0.74	$ 0.80	$ 1.22	$ 2.54	$ 1.88

Quarterly Data (Unaudited) -205

Quarterly Data (Unaudited) - Quarterly Composite Common Stock Prices and Dividends (Details) - USD ($)	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015
Quarterly Financial Data [Abstract]
High price	$ 36.36	$ 37.70	$ 36.37	$ 35.95	$ 31.37	$ 34.44	$ 34.98	$ 38.25
Low price	$ 29.82	$ 32.86	$ 33.18	$ 26.26	$ 25.09	$ 28.41	$ 31.28	$ 31.71
Close	$ 35.49	$ 33.29	$ 36.36	$ 35.86	$ 27.77	$ 29.70	$ 31.42	$ 33.61
Dividends	$ 0.318	$ 0.318	$ 0.318	$ 0.310	$ 0.310	$ 0.310	$ 0.310	$ 0.310

Schedule I - Condensed Finan206

Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Statements of Operations and Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended									12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Mar. 23, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015		Dec. 31, 2014
Operating Expenses [Abstract]
Operating and maintenance										$ 10,048	$ 8,322		$ 8,568
Total operating expenses										28,200	25,056		25,039
Operating Income (Loss)	$ 714	$ 1,267	$ 647	$ 483		$ 707	$ 1,200	$ 1,134	$ 1,366	3,112	4,409		3,096
Other income and (deductions)
Interest expense, net										(1,495)	(992)		(1,024)
Equity in losses of unconsolidated affiliates										(24)	(7)		0
Other, net										413	(46)		455
Total other income and (deductions)										(1,123)	(1,079)		(610)
Income before income taxes										1,989	3,330		2,486
Income taxes										761	1,073		666
Net Income										1,204	2,250		1,820
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost, net of tax										48	46		30
Actuarial loss reclassified to periodic cost, net of tax										184	220		147
Unrealized gain (loss) on cash flow hedges, net of taxes					$ 0					2	9		(148)
Unrealized gain (loss) on marketable securities, net of taxes										(4)	(3)		8
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax										1	0		1
Unrealized gain (loss) on foreign currency translation, net of taxes										10	(21)		(9)
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease										0	0		(116)
Other comprehensive income (loss)										(36)	60	[1]	(644)
Comprehensive income										1,098	2,329		979
Exelon Corporate [Member]
Operating Expenses [Abstract]
Operating and maintenance										221	0		9
Operating and maintenance from affiliates										51	43		38
Other										4	4		3
Total operating expenses										276	47		50
Operating Income (Loss)										(276)	(47)		(50)
Other income and (deductions)
Interest expense, net										(312)	(168)		(237)
Equity in losses of unconsolidated affiliates										1,521	2,461		1,779
Interest income from affiliates, net										39	43		53
Other, net										7	(43)		(2)
Total other income and (deductions)										1,255	2,293		1,593
Income before income taxes										979	2,246		1,543
Income taxes										(155)	(23)		(80)
Net Income										1,134	2,269		1,623
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost, net of tax										48	46		30
Actuarial loss reclassified to periodic cost, net of tax										184	220		147
Other Comprehensive Income (Loss), Finalization of Pension and Other Postretirement Benefit Plan Valuation, Net of Tax										181	99		497
Unrealized gain (loss) on cash flow hedges, net of taxes										2	9		(148)
Unrealized gain (loss) on marketable securities, net of taxes										(4)	(3)		8
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax										1	0		1
Unrealized gain (loss) on foreign currency translation, net of taxes										10	(21)		(9)
OtherComprehensiveIncomeLossNetOfTaxPeriodDecrease										0	0		116
Other comprehensive income (loss)										(36)	60		(644)
Comprehensive income										$ 1,098	$ 2,329		$ 979
[1]	All amounts are net of tax and noncontrolling interests. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.

Schedule I - Condensed Finan207

Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Millions	Feb. 26, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net cash flows provided by operating activities		$ 8,445	$ 7,616	$ 4,457
Cash flows from investing activities
Proceeds From Lease Termination	$ 335	360
Proceeds from Sale and Collection of Lease Receivables		360	0	335
Capital expenditures		(8,553)	(7,624)	(6,077)
Cash and restricted cash acquired from Constellation		0	0	140
Change in restricted cash		(42)	66	(104)
Other investing activities		(153)	(119)	(88)
Net cash flows used in investing activities		(15,503)	(7,822)	(4,599)
Cash flows from financing activities
Changes in short-term borrowings		240	0	0
Issuance of long-term debt		4,716	6,709	3,463
Retirement of long-term debt		(1,936)	(2,687)	(1,545)
Proceeds from Issuance of Common Stock		0	1,868	0
Dividends paid on common stock		(1,166)	(1,105)	(1,065)
Proceeds from employee stock plans		55	32	35
Other financing activities		(85)	(99)	(178)
Net cash flows provided by financing activities		1,191	4,830	411
(Decrease) Increase in cash and cash equivalents		(5,867)	4,624	269
Cash and cash equivalents at beginning of period		6,502	1,878	1,609
Cash and cash equivalents at end of period		635	6,502	1,878
Exelon Corporate [Member]
Net cash flows provided by operating activities		1,029	3,071	806
Cash flows from investing activities
Payments to Acquire Businesses, Net of Cash Acquired		(6,962)
Proceeds from Sale and Collection of Lease Receivables		0	0	335
Increase (Decrease) Due from Affiliates		1,390	(1,217)	(83)
Increase (Decrease) in Due from Affiliates, Current		0	550	0
Capital expenditures		0	0	1
Investment in affiliates		(1,757)	(212)	(70)
Other investing activities		5	(55)	(126)
Net cash flows used in investing activities		(7,324)	(934)	57
Cash flows from financing activities
Issuance of long-term debt		1,800	4,200	1,150
Retirement of long-term debt		(46)	(2,263)	(23)
Proceeds from Issuance of Common Stock		0	1,868	0
Dividends paid on common stock		(1,166)	(1,105)	(1,065)
Proceeds from employee stock plans		55	32	35
Other financing activities		(20)	(58)	(84)
Net cash flows provided by financing activities		623	2,674	13
(Decrease) Increase in cash and cash equivalents		(5,672)	4,811	876
Cash and cash equivalents at beginning of period		5,690	879	3
Cash and cash equivalents at end of period		$ 18	$ 5,690	$ 879

Schedule I - Condensed Finan208

Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Balance Sheet (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current assets
Cash and cash equivalents		$ 635	$ 6,502	$ 1,878	$ 1,609
Prepaid Taxes		1,250	0
Accounts receivable, net
Other		1,201	912
Regulatory assets		1,342	759
Other		930	752
Total current assets		12,412	15,334
Property, plant and equipment, net		71,555	57,439
Deferred debits and other assets
Regulatory assets		10,046	6,065
Other		1,472	1,445
Total assets (a)	[1]	114,904	95,384
Current liabilities
Short-term Debt		1,267	533
Due to Affiliate, Current		706	0
Long-term debt due within one year		2,430	1,500
Accounts payable		3,441	2,883
Unamortized energy contract liabilities		407	100
Accrued expenses		3,460	2,376
Regulatory liabilities		602	369
Other		981	842
Total current liabilities		13,457	9,118
Long-term debt		31,575	23,645
Deferred credits and other liabilities
Regulatory liabilities		4,187	4,201
Pension obligations		4,248	3,385
Non-pension postretirement benefit obligations		1,848	1,618
Other		1,827	1,491
Total liabilities	[1]	87,292	68,062
Shareholders’ equity
Common stock		18,794	18,676
Treasury stock, at cost (35 shares at December 31, 2016 and 2015, respectively)		(2,327)	(2,327)
Retained earnings		12,030	12,068
Accumulated other comprehensive loss, net		(2,660)	(2,624)
Total shareholders’ equity		25,837	25,793
BGE preference stock not subject to mandatory redemption		0	193
Liabilities and Equity		114,904	95,384
Exelon Corporate [Member]
Current assets
Cash and cash equivalents		18	5,690	$ 879	$ 3
Accounts receivable, net
Other		73	272
Accounts receivable from affiliates		48	20
Receivables from affiliates		88	1,478
Regulatory assets		263	241
Other		1,250	5
Total current assets		1,740	7,706
Property, plant and equipment, net		51	53
Deferred debits and other assets
Regulatory assets		4,033	3,072
Investments in affiliates		34,869	26,119
Deferred income taxes		2,107	2,036
Receivable from affiliates		922	933
Defined Benefit Plan, Assets for Plan Benefits, Noncurrent			108
Other		256	404
Total deferred debits and other assets		42,187	32,672
Total assets (a)		43,978	40,431
Current liabilities
Short-term Debt		0	188
Due to Affiliate, Current		706
Long-term debt due within one year		570	60
Accounts payable		2	5
Accrued expenses		489	440
Regulatory liabilities		16	63
Pension and Other Postretirement Defined Benefit Plans, Current Liabilities		58	52
Other		50	1
Total current liabilities		1,891	809
Long-term debt		7,193	6,017
Deferred credits and other liabilities
Regulatory liabilities		31	31
Pension obligations		8,608	7,520
Non-pension postretirement benefit obligations		7	0
Deferred income taxes		226	134
Other		182	122
Deferred Credits and Other Liabilities, Noncurrent		9,054	7,807
Total liabilities		18,138	14,633
Commitments and Contingencies
Shareholders’ equity
Common stock		18,797	18,678
Treasury stock, at cost (35 shares at December 31, 2016 and 2015, respectively)		(2,327)	(2,327)
Retained earnings		12,030	12,068
Accumulated other comprehensive loss, net		(2,660)	(2,624)
Total shareholders’ equity		25,840	25,795
BGE preference stock not subject to mandatory redemption		0	3
Liabilities and Equity		$ 43,978	$ 40,431
[1]	Exelon’s consolidated assets include $8,893 million and $8,268 million at December 31, 2016 and December 31, 2015, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,356 million and $3,264 million at December 31, 2016 and December 31, 2015, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2–Variable Interest Entities.

Schedule I - Condensed Finan209

Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Condensed Balance Sheet - Phantom (Details) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	2,000,000,000	2,000,000,000
Common Stock, Shares, Outstanding	924,035,059	919,924,742
Treasury Stock, Shares held	35,000,000	35,000,000
Exelon Corporate [Member]
Common stock, par value	$ 0	$ 0
Common stock, shares authorized	2,000,000,000	2,000,000,000
Treasury Stock, Shares held	35,000,000	35,000,000

Schedule I - Condensed Finan210

Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Basis of Presentation - Narrative (Details) - Exelon Corporate [Member]	Dec. 31, 2016
Exelon Generation Co L L C [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	100.00%
Commonwealth Edison Co [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	99.00%
Baltimore Gas and Electric Company [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	100.00%
Baltimore Gas and Electric Company [Member] | Preferred Stock [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	0.00%
PECO Energy Co [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	100.00%
PECO Energy Co [Member] | Preferred Stock [Member]
Schedule of Equity Method Investments [Line Items]
Ownership interest	0.00%

Schedule I - Condensed Finan211

Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Debt and Credit Agreements - Narrative (Details)	Dec. 31, 2016USD ($)
Line of Credit Facility [Line Items]
Line of Credit Facility, Capacity Available for Trade Purchases	$ 7,108,000,000	[1]
Exelon Corporate [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Capacity Available for Trade Purchases	571,000,000	[1]
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum Program Size	9,500,000,000	[2]
Revolving Credit Facility [Member] | Exelon Corporate [Member]
Line of Credit Facility [Line Items]
Maximum Program Size	$ 600,000,000	[3],[4]
[1]	Pepco, DPL and ACE's revolving credit facility is subject to available borrowing capacity. The borrowing capacity may be increased or decreased during the term of the facility, except that (i) the sum of the borrowing capacity must equal the total amount of the facility, and (ii) the aggregate amount of credit used at any given time by each of Pepco, DPL or ACE may not exceed $900 million or the maximum amount of short-term debt the company is permitted to have outstanding by its regulatory authorities. The total number of the borrowing reallocations may not exceed eight per year during the term of the facility.
[2]	Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million ,$5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.
[3]	Excludes $500 million and $275 million in bilateral credit facilities that do not back Generation's commercial paper program at December 31, 2016 and 2015, respectively
[4]	Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million, $5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.

Schedule I - Condensed Finan212

Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Debt and Credit Agreements - Schedule of Outstanding Long-term Debt (Details) - USD ($)		Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2015
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 33,311,000,000	$ 25,113,000,000
Unamortized debt discount and premium, net		(68,000,000)	(63,000,000)
Long-term debt		31,575,000,000	23,645,000,000
Unamortized Debt Issuance Expense	[1]	(200,000,000)	(180,000,000)
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		1,150,000,000	1,150,000,000	$ 1,150,000,000
Senior Notes [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		11,868,000,000	9,803,000,000
contract Payments Junior Subordinate Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 19,000,000	64,000,000
Maximum [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		6.50%
Maximum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		7.60%
Maximum [Member] | contract Payments Junior Subordinate Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		2.50%
Minimum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage		1.55%
Exelon Corporate [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 7,608,000,000	5,853,000,000
Unamortized debt discount and premium, net		(8,000,000)	(4,000,000)
Fair value adjustment of consolidated subsidiary		220,000,000	275,000,000
Long-term debt due within one year		(570,000,000)	(60,000,000)
Long-term debt		7,193,000,000	6,017,000,000
Unamortized Debt Issuance Expense		(57,000,000)	(47,000,000)
Exelon Corporate [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 1,150,000,000	1,150,000,000
Debt Instrument, Interest Rate, Stated Percentage		6.50%
Exelon Corporate [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured Long Term Debt	[2]	$ 6,439,000,000	4,639,000,000
Exelon Corporate [Member] | contract Payments Junior Subordinate Debt [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross		$ 19,000,000	$ 64,000,000
Debt Instrument, Interest Rate, Stated Percentage		2.50%
Exelon Corporate [Member] | Maximum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[2]	7.60%
Exelon Corporate [Member] | Minimum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	[2]	1.60%
[1]	Amounts owed to these financing trusts are recorded as Long-term debt to financing trusts within Exelon’s Consolidated Balance Sheets.
[2]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjY2ZTAyZGU0MjJhODQwMGQ4YTI0ZmVhYjg5OGIyNGRifFRleHRTZWxlY3Rpb246QjFDN0Q4OTA0OTQyMUZCQTgxMDE5RjkyNUQyN0VERjAM}

Schedule I - Condensed Finan213

Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Debt and Credit Agreements - Schedule of Debt Maturities (Details) $ in Millions	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
2,017	$ 2,430
2,018	1,742
2,019	1,060
2,020	3,331
2,021	2,400
Thereafter	22,996	[1]
Total	33,959
Exelon Corporate [Member]
Debt Instrument [Line Items]
2,017	570
2,018	0
2,019	0
2,020	1,450
2,021	300
Thereafter	5,288
Total	$ 7,608
[1]	Includes $648 million due to ComEd, PECO and BGE financing trusts.

Schedule I - Condensed Finan214

Schedule I - Condensed Financial Information of Parent (Exelon Corporate) - Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments		$ (24)	$ (7)	$ 0
Due to Affiliate, Current		706	0
Exelon Corporate [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates		51	43	38
Interest income from affiliates, net		39	43	53
Income (Loss) from Equity Method Investments		1,521	2,461	1,779
Cash contributions received from affiliates		1,912	3,209	1,370
Accounts receivable from affiliates		48	20
Receivables from affiliates		88	1,478
Investments in affiliates		34,869	26,119
Total receivable from affiliates (noncurrent)		922	933
Due to Affiliate, Current		706
Exelon Corporate [Member] | Business Services Company [Member]
Related Party Transaction [Line Items]
Operating and maintenance from affiliates	[1]	51	43	38
Income (Loss) from Equity Method Investments		1
Accounts receivable from affiliates	[1]	15	0
Receivables from affiliates	[1]	88	226
Investments in affiliates	[1]	194	191
Due to Affiliate, Current		361
Exelon Corporate [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates		6
Exelon Corporate [Member] | Potomac Capital Investment Affiliate [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments		6
Investments in affiliates	[2]	77
Exelon Corporate [Member] | Exelon Energy Delivery Company LLC [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments	[3]	1,041	1,079	958
Investments in affiliates	[3]	23,003	14,163
Exelon Corporate [Member] | Exelon Ventures Company LLC [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments	[2]	0	0	926
Exelon Corporate [Member] | UII LLC [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments		(9)	20	(6)
Investments in affiliates		92	102
Exelon Corporate [Member] | Exelon Transmission Company LLC [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments		(13)	(8)	(7)
Investments in affiliates		5	3
Exelon Corporate [Member] | ExelonEnterprise [Member]
Related Party Transaction [Line Items]
Income (Loss) from Equity Method Investments		(1)	(1)	(1)
Investments in affiliates		21	22
Exelon Corporate [Member] | Exelon Consolidations [Member]
Related Party Transaction [Line Items]
Investments in affiliates		(6)	(6)
Exelon Corporate [Member] | Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Interest income from affiliates, net		39	43	53
Income (Loss) from Equity Method Investments		496	1,371	$ (91)
Accounts receivable from affiliates		22	16
Receivables from affiliates		0	1,252
Investments in affiliates		11,488	11,637
Total receivable from affiliates (noncurrent)		922	933
Exelon Corporate [Member] | Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates		3	2
Due to Affiliate, Current		345	188
Exelon Corporate [Member] | PECO Energy Co [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates		1	1
Exelon Corporate [Member] | Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Accounts receivable from affiliates		1	1
Exelon Corporate [Member] | VEBA [Member]
Related Party Transaction [Line Items]
Investments in affiliates		$ (5)	$ 7
[1]	Exelon Corporate receives a variety of corporate support services from BSC, including legal, human resources, financial, information technology and supply management services. All services are provided at cost, including applicable overhead.
[2]	Exelon Ventures Company, LLC primarily consisted of Generation
[3]	Exelon Energy Delivery Company, LLC consists of ComEd, PECO, BGE, PHI, Pepco, DPL and ACE.

Schedule II - Valuation and 215

Schedule II - Valuation and Qualifying Accounts Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended	12 Months Ended
		Mar. 23, 2016	Dec. 31, 2016	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	[1]	$ 284		$ 284		$ 311	$ 272
Charged to Costs and Expenses	[1]			162		113	175
Charged to Other Accounts	[1],[2]			99	[3]	27	69
Deductions	[1],[4]			211		167	205
Balance at End of Period	[1]		$ 334	334		284	311
Deferred Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		13		13		50	13
Charged to Costs and Expenses				0		0	0
Charged to Other Accounts				10	[3]	(27)	37
Deductions				3		10	0
Balance at End of Period			20	20		13	50
Reserve for Obsolete Materials [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		105		105		95	58
Charged to Costs and Expenses				12		10	5
Charged to Other Accounts				1	[3]	2	34
Deductions				5		2	2
Balance at End of Period			113	113		105	95
Exelon Generation Co L L C [Member] | Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		77		77		60	57
Charged to Costs and Expenses				19		22	14
Charged to Other Accounts				3		0	8
Deductions				8		5	19
Balance at End of Period			91	91		77	60
Exelon Generation Co L L C [Member] | Deferred Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		11		11		48	11
Charged to Costs and Expenses				0		0	0
Charged to Other Accounts				0		(27)	37
Deductions				2		10	0
Balance at End of Period			9	9		11	48
Exelon Generation Co L L C [Member] | Reserve for Obsolete Materials [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		102		102		93	55
Charged to Costs and Expenses				6		9	5
Charged to Other Accounts				0		0	32
Deductions				2		0	(1)
Balance at End of Period			106	106		102	93
Commonwealth Edison Co [Member] | Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		75		75		84	62
Charged to Costs and Expenses				45		39	45
Charged to Other Accounts	[5]			23		18	33
Deductions	[6]			73		66	56
Balance at End of Period			70	70		75	84
Commonwealth Edison Co [Member] | Reserve for Obsolete Materials [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		3		3		2	2
Charged to Costs and Expenses				4		1	0
Charged to Other Accounts				1		2	2
Deductions				4		2	2
Balance at End of Period			4	4		3	2
PECO Energy Co [Member] | Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	[7]	83		83		100	107
Charged to Costs and Expenses	[7]			32		37	52
Charged to Other Accounts	[7],[8]			7		9	11
Deductions	[7],[9]			61		63	70
Balance at End of Period	[7]		61	61		83	100
PECO Energy Co [Member] | Reserve for Obsolete Materials [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		1		1		1	1
Charged to Costs and Expenses				1		0	0
Charged to Other Accounts				0		0	0
Deductions				0		0	0
Balance at End of Period			2	2		1	1
PECO Energy Co [Member] | Allowance for Doubtful Accounts, Noncurrent [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		8		8		8
Balance at End of Period			23	23		8	8
Baltimore Gas and Electric Company [Member] | Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		49		49		67	46
Charged to Costs and Expenses				1		15	64
Charged to Other Accounts	[10]			9		0	17
Deductions	[11]			27		33	60
Balance at End of Period			32	32		49	67
Baltimore Gas and Electric Company [Member] | Deferred Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		1		1		1	1
Charged to Costs and Expenses				0		0	0
Charged to Other Accounts				0		0	0
Deductions				0		0	0
Balance at End of Period			1	1		1	1
Baltimore Gas and Electric Company [Member] | Reserve for Obsolete Materials [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		0		0		0	1
Charged to Costs and Expenses				0		0	0
Charged to Other Accounts				0		0	0
Deductions				0		0	1
Balance at End of Period			0	0		0	0
Pepco Holdings LLC [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Charged to Costs and Expenses				10
Potomac Electric Power Company [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Charged to Costs and Expenses				6
Potomac Electric Power Company [Member] | Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		17		17		16	16
Charged to Costs and Expenses				29		20	17
Charged to Other Accounts	[12]			3		1	2
Deductions	[13]			20		20	19
Balance at End of Period			29	29		17	16
Potomac Electric Power Company [Member] | Deferred Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		0		0		0	0
Charged to Costs and Expenses				0		0	0
Charged to Other Accounts				0		0	0
Deductions				0		0	0
Balance at End of Period			0	0		0	0
Potomac Electric Power Company [Member] | Reserve for Obsolete Materials [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		0		0		0	0
Charged to Costs and Expenses				3		0	0
Charged to Other Accounts				0		0	0
Deductions				2		0	0
Balance at End of Period			1	1		0	0
Delmarva Power and Light Company [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Charged to Costs and Expenses				4
Delmarva Power and Light Company [Member] | Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		17		17		11	12
Charged to Costs and Expenses				23		20	13
Charged to Other Accounts	[14]			2		2	4
Deductions	[15]			18		16	18
Balance at End of Period			24	24		17	11
Delmarva Power and Light Company [Member] | Deferred Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		0		0		0	0
Charged to Costs and Expenses				0		0	0
Charged to Other Accounts				0		0	0
Deductions				0		0	0
Balance at End of Period			0	0		0	0
Delmarva Power and Light Company [Member] | Reserve for Obsolete Materials [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		0		0		0	0
Charged to Costs and Expenses				1		0	0
Charged to Other Accounts				0		0	0
Deductions				1		0	0
Balance at End of Period			0	0		0	0
Atlantic City Electric Company [Member] | Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		17		17		9	10
Charged to Costs and Expenses				32		18	12
Charged to Other Accounts	[16]			2		2	3
Deductions	[17]			24		12	16
Balance at End of Period			27	27		17	9
Atlantic City Electric Company [Member] | Deferred Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		0		0		0	0
Charged to Costs and Expenses				0		0	0
Charged to Other Accounts				0		0	0
Deductions				0		0	0
Balance at End of Period			0	0		0	0
Atlantic City Electric Company [Member] | Reserve for Obsolete Materials [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		0		0		0	0
Charged to Costs and Expenses				1		0	0
Charged to Other Accounts				0		0	0
Deductions				0		0	0
Balance at End of Period			1	1		0	0
Successor [Member] | Pepco Holdings LLC [Member] | Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period			52
Charged to Costs and Expenses			65
Charged to Other Accounts	[18]		5
Deductions	[19]		42
Balance at End of Period		52	80	80
Successor [Member] | Pepco Holdings LLC [Member] | Deferred Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period			63
Charged to Costs and Expenses			0
Charged to Other Accounts			(53)
Deductions			0
Balance at End of Period		63	10	10
Successor [Member] | Pepco Holdings LLC [Member] | Reserve for Obsolete Materials [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period			0
Charged to Costs and Expenses			1
Charged to Other Accounts			0
Deductions			(1)
Balance at End of Period		0	2	2
Predecessor [Member] | Pepco Holdings LLC [Member] | Allowance for Uncollectible Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		56	52	56		40	38
Charged to Costs and Expenses		16				59	46
Charged to Other Accounts	[18]	2				5	9
Deductions	[19]	22				48	53
Balance at End of Period		52				56	40
Predecessor [Member] | Pepco Holdings LLC [Member] | Deferred Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		63	63	63		61	21
Charged to Costs and Expenses		0				0	0
Charged to Other Accounts		0				2	40
Deductions		0				0	0
Balance at End of Period		63				63	61
Predecessor [Member] | Pepco Holdings LLC [Member] | Reserve for Obsolete Materials [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period		0	$ 0	$ 0		0	0
Charged to Costs and Expenses		0				0	0
Charged to Other Accounts		0				0	0
Deductions		0				0	0
Balance at End of Period		$ 0				$ 0	$ 0
[1]	Excludes the non-current allowance for uncollectible accounts related to PECO’s installment plan receivables of $23 million, $8 million, and $8 million for the years ended December 31, 2016, 2015, and 2014, respectively.
[2]	Includes charges for late payments and non-service receivables.
[3]	Primarily represents the addition of PHI's results as of March 23, 2016, the date of the merger
[4]	Write-off of individual accounts receivable.
[5]	Primarily charges for late payments and non-service receivables.
[6]	Write-off of individual accounts receivable.
[7]	Excludes the non-current allowance for uncollectible accounts related to PECO’s installment plan receivables of $23 million, $8 million, and $8 million for the years ended December 31, 2016, 2015, and 2014, respectively.
[8]	Primarily charges for late payments.
[9]	Write-off of individual accounts receivable.
[10]	Primarily charges for late payments.
[11]	Write-off of individual accounts receivable.
[12]	Primarily charges for late payments.
[13]	Write-off of individual accounts receivable.
[14]	Primarily charges for late payments.
[15]	Write-off of individual accounts receivable.
[16]	Primarily charges for late payments.
[17]	Write-off of individual accounts receivable.
[18]	Primarily charges for late payments.
[19]	Write-off of individual accounts receivable.

Uncategorized Items - exc-20161

Label	Element	Value
Successor [Member]
Impairment of Long-Lived Assets Held-for-use	us-gaap_ImpairmentOfLongLivedAssetsHeldForUse	$ 0
Predecessor [Member]
Impairment of Long-Lived Assets Held-for-use	us-gaap_ImpairmentOfLongLivedAssetsHeldForUse	0
PECO Energy Co [Member] | Over-Recovered Electric Transmission Cost [Member]
Regulatory Liabilities	us-gaap_RegulatoryLiabilities	3,000,000
PECO Energy Co [Member] | DSP Program costs [Member]
Regulatory Liabilities	us-gaap_RegulatoryLiabilities	35,000,000
PECO Energy Co [Member] | OverRecoveredNaturalGasSupply [Member]
Regulatory Liabilities	us-gaap_RegulatoryLiabilities	$ 22,000,000
PECO Energy Co [Member] | Minimum [Member] | Energy Efficiency And Demand Response Programs [Member]
Cumulative Consumption Reduction Targets	exc_CumulativeConsumptionReductionTargets	1,962,659
Pepco Holdings LLC [Member] | Successor [Member]
Increase (Decrease) Cash Collateral from Counterparties	us-gaap_IncreaseDecreaseCashCollateralFromCounterparties	$ 0
Net Cash Provided by (Used in) Investing Activities	us-gaap_NetCashProvidedByUsedInInvestingActivities	(1,030,000,000)
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	37,000,000
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	338,000,000
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	(149,000,000)
Net Cash Provided by (Used in) Financing Activities	us-gaap_NetCashProvidedByUsedInFinancingActivities	(7,000,000)
Proceeds from Stock Plans	us-gaap_ProceedsFromStockPlans	0
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	(5,000,000)
Increase (Decrease) in Other Operating Assets and Liabilities, Net	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet	311,000,000
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	0
Proceeds from (Repayments of) Short-term Debt	us-gaap_ProceedsFromRepaymentsOfShortTermDebt	(515,000,000)
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	0
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	42,000,000
Repayments of Debt, Maturing in More than Three Months	us-gaap_RepaymentsOfDebtMaturingInMoreThanThreeMonths	300,000,000
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	24,000,000
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(514,000,000)
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	295,000,000
Increase (Decrease) in Due to Affiliates	us-gaap_IncreaseDecreaseInDueToAffiliates	(6,000,000)
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	0
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	21,000,000
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	19,000,000
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	9,000,000
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax	0
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	(3,000,000)
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	179,000,000
Net Cash Provided by (Used in) Operating Activities	us-gaap_NetCashProvidedByUsedInOperatingActivities	888,000,000
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	(22,000,000)
Proceeds from Issuance of Preferred Stock and Preference Stock	us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0
Pepco Holdings LLC [Member] | Predecessor [Member]
Increase (Decrease) Cash Collateral from Counterparties	us-gaap_IncreaseDecreaseCashCollateralFromCounterparties	1,000,000
Net Cash Provided by (Used in) Investing Activities	us-gaap_NetCashProvidedByUsedInInvestingActivities	(343,000,000)
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	(3,000,000)
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	11,000,000
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	293,000,000
Net Cash Provided by (Used in) Financing Activities	us-gaap_NetCashProvidedByUsedInFinancingActivities	372,000,000
Proceeds from Stock Plans	us-gaap_ProceedsFromStockPlans	2,000,000
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	2,000,000
Increase (Decrease) in Other Operating Assets and Liabilities, Net	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet	9,000,000
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	500,000,000
Proceeds from (Repayments of) Short-term Debt	us-gaap_ProceedsFromRepaymentsOfShortTermDebt	(121,000,000)
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	68,000,000
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	0
Repayments of Debt, Maturing in More than Three Months	us-gaap_RepaymentsOfDebtMaturingInMoreThanThreeMonths	0
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	0
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(46,000,000)
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	19,000,000
Increase (Decrease) in Due to Affiliates	us-gaap_IncreaseDecreaseInDueToAffiliates	0
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	(18,000,000)
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	28,000,000
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	42,000,000
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	5,000,000
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax	0
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	4,000,000
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	0
Net Cash Provided by (Used in) Operating Activities	us-gaap_NetCashProvidedByUsedInOperatingActivities	264,000,000
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	12,000,000
Proceeds from Issuance of Preferred Stock and Preference Stock	us-gaap_ProceedsFromIssuanceOfPreferredStockAndPreferenceStock	0
Baltimore Gas and Electric Company [Member] | Stride Program [Member]
Regulatory Liabilities	us-gaap_RegulatoryLiabilities	2,000,000
Captial and OM estimates current year	exc_CapitalandOMestimatescurrentyear	131,000,000
Retained Earnings [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	10,358,000,000
Retained Earnings [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Members' Equity	us-gaap_MembersEquity	0
Retained Earnings [Member] | Baltimore Gas and Electric Company [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1,005,000,000
Treasury Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	(2,327,000,000)
Common Stock [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	16,741,000,000
Employee Service Share-based Compensation, Tax Benefit Realized from Exercise of Stock Options	us-gaap_EmployeeServiceShareBasedCompensationTaxBenefitRealizedFromExerciseOfStockOptions	(18,000,000)
Common Stock [Member] | Baltimore Gas and Electric Company [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	1,360,000,000
AOCI Attributable to Parent [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	(2,040,000,000)
AOCI Attributable to Parent [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Members' Equity	us-gaap_MembersEquity	0
AOCI Attributable to Parent [Member] | Exelon Generation Co L L C [Member]
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_LimitedLiabilityCompanyLlcMembersEquityIncludingPortionAttributableToNoncontrollingInterest	(54,000,000)
Noncontrolling Interest [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	15,000,000
Noncontrolling Interest [Member] | Exelon Generation Co L L C [Member]
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	us-gaap_NoncontrollingInterestIncreaseFromSaleOfParentEquityInterest	2,000,000
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_LimitedLiabilityCompanyLlcMembersEquityIncludingPortionAttributableToNoncontrollingInterest	1,774,000,000
Common Stock Including Additional Paid in Capital [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Members' Equity	us-gaap_MembersEquity	7,200,000,000	[1]
Business Combination, Contingent Consideration, Liability, Noncurrent	us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent	53,000,000
Preference Stock Not Subject To Mandatory Redemption [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	193,000,000
Preference Stock Not Subject To Mandatory Redemption [Member] | Baltimore Gas and Electric Company [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	190,000,000
Undistributed Earnings [Member] | Exelon Generation Co L L C [Member]
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_LimitedLiabilityCompanyLlcMembersEquityIncludingPortionAttributableToNoncontrollingInterest	2,275,000,000
Membership Interest [Member] | Baltimore Gas and Electric Company [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	2,365,000,000
Membership Interest [Member] | Exelon Generation Co L L C [Member]
Limited Liability Company (LLC) Members' Equity, Including Portion Attributable to Noncontrolling Interest	us-gaap_LimitedLiabilityCompanyLlcMembersEquityIncludingPortionAttributableToNoncontrollingInterest	9,261,000,000
Pepco Holdings LLC [Member] | Commitments [Member] | Successor [Member]
Payments to Acquire Businesses, Gross	us-gaap_PaymentsToAcquireBusinessesGross	$ 33,000,000
[1]	The March 24, 2016, beginning balance differs from the PHI Merger total purchase price by $59 million related to an acquisition accounting adjustment recorded at Exelon Corporate to reflect unitary state income tax consequences of the merger.