Pepco 10-Q 3 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	3 Months Ended
	Mar. 31, 2017shares
Entity Registrant Name	EXELON CORP
Entity Central Index Key	1,109,357
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
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	926,096,660
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	127,017,158
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	Large Accelerated Filer
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	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 23, 2016
Operating revenues [Abstract]
Operating Revenue		$ 4,560	$ 4,473
Regulated Operating Revenue		4,197	3,100
Electric operating revenues		3,644	2,657
Natural gas operating revenues		553	444
Revenues		8,757	7,573
Operating expenses
Competitive businesses purchased power and fuel		2,795	2,440
Purchased power and fuel		1,104	814
Operating and maintenance		2,460	2,835
Depreciation and amortization		896	685
Taxes other than income		436	325
Total operating expenses		7,691	7,099
Gain (Loss) on Disposition of Other Assets		4	9
Bargain purchase gain		226	0
Operating income		1,296	483
Other income and (deductions)
Interest expense, net		(363)	(277)
Interest expense to affiliates		(10)	(10)
Other, net		283	114
Total other income and (deductions)		(90)	(173)
Income before income taxes		1,206	310
Income taxes		215	184
Equity in losses of unconsolidated affiliates		(10)	(3)
Net income		981	123
Net loss attributable to noncontrolling interests and preference stock dividends		(14)	(50)
Net income attributable to common shareholders		995	173
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost		(13)	(12)
Actuarial loss reclassified to periodic benefit cost		(49)	46
Pension and non-pension postretirement benefit plan valuation adjustment		(59)	1
Unrealized gain (loss) on cash flow hedges		6	7
Unrealized gain (loss) on equity investments		3	3
Unrealized gain on foreign currency translation		1	(6)
Unrealized gain (loss) on marketable securities		1	(1)
Other comprehensive (loss) income		(12)	28
Comprehensive income		969	151
Comprehensive loss attributable to noncontrolling interests and preference stock dividends		(16)	(50)
Comprehensive income attributable to common shareholders		$ 985	$ 201
Average shares of common stock outstanding:
Weighted average common shares outstanding — basic		928	923
Weighted average common shares outstanding — diluted		930	925
Earnings per average common share:
Basic		$ 1.07	$ 0.19
Diluted		1.07	0.19
Dividends declared per common share		$ 0.3275	$ 0.31
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating Revenue		$ 4,558	$ 4,471
Operating revenues from affiliates		330	268
Revenues		4,888	4,739
Operating expenses
Purchased power and fuel		2,796	2,440
Purchased power from affiliate		2	2
Operating and maintenance		1,309	1,296
Operating and maintenance from affiliates		179	171
Depreciation and amortization		302	289
Taxes other than income		143	126
Total operating expenses		4,731	4,324
Gain (Loss) on Disposition of Other Assets		4	0
Bargain purchase gain		226	0
Operating income		387	415
Other income and (deductions)
Interest expense, net		(90)	(87)
Interest expense to affiliates		(10)	(10)
Other, net		259	93
Total other income and (deductions)		159	(4)
Income before income taxes		546	411
Income taxes		127	151
Equity in losses of unconsolidated affiliates		(10)	(3)
Net income		409	257
Net loss attributable to noncontrolling interests		(14)	(53)
Net income attributable to membership interest		423	310
Other comprehensive income (loss), net of income taxes
Unrealized gain (loss) on cash flow hedges		(6)	5
Unrealized gain (loss) on equity investments		(4)	2
Unrealized gain on foreign currency translation		(1)	(6)
Other comprehensive (loss) income		11	(1)
Comprehensive income		420	256
Comprehensive loss attributable to noncontrolling interests and preference stock dividends		(16)	(53)
Comprehensive income attributable to common shareholders		436	309
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Electric operating revenues		1,293	1,244
Operating revenues from affiliates		5	5
Revenues		1,298	1,249
Operating expenses
Purchased power and fuel		329	343
Purchased power from affiliate		5	5
Operating and maintenance		307	305
Operating and maintenance from affiliates		63	63
Depreciation and amortization		208	189
Taxes other than income		72	75
Total operating expenses		984	980
Gain (Loss) on Disposition of Other Assets		0	5
Operating income		314	274
Other income and (deductions)
Interest expense, net		(82)	(83)
Interest expense to affiliates		(3)	(3)
Other, net		4	4
Total other income and (deductions)		(81)	(82)
Income before income taxes		233	192
Income taxes		92	77
Net income		141	115
Other comprehensive income (loss), net of income taxes
Comprehensive income		141	115
PECO Energy Co [Member]
Operating revenues [Abstract]
Electric operating revenues		589	643
Natural gas operating revenues		206	197
Operating revenues from affiliates		1	1
Revenues		796	841
Operating expenses
Purchased power		156	166
Purchased fuel		86	77
Purchased power from affiliate		45	78
Operating and maintenance		174	177
Operating and maintenance from affiliates		34	38
Depreciation and amortization		71	67
Taxes other than income		38	42
Total operating expenses		604	645
Operating income		192	196
Other income and (deductions)
Interest expense, net		(28)	(28)
Interest expense to affiliates		(3)	(3)
Other, net		2	2
Total other income and (deductions)		(29)	(29)
Income before income taxes		163	167
Income taxes		36	43
Net income		127	124
Other comprehensive income (loss), net of income taxes
Comprehensive income		127	124
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues		665	678
Natural gas operating revenues		281	246
Operating revenues from affiliates		5	5
Revenues		951	929
Operating expenses
Purchased power		133	127
Purchased fuel		83	75
Purchased power from affiliate		134	171
Operating and maintenance		148	168
Operating and maintenance from affiliates		35	34
Depreciation and amortization		128	109
Taxes other than income		62	58
Total operating expenses		723	742
Operating income		228	187
Other income and (deductions)
Interest expense, net		(23)	(20)
Interest expense to affiliates		(4)	(4)
Other, net		4	4
Total other income and (deductions)		(23)	(20)
Income before income taxes		205	167
Income taxes		80	66
Net income		125	101
Preference stock dividends		0	3
Net income attributable to common shareholders		125	98
Other comprehensive income (loss), net of income taxes
Comprehensive income		125	101
Comprehensive loss attributable to noncontrolling interests and preference stock dividends		0	3
Comprehensive income attributable to common shareholders		125	98
Pepco Holdings LLC [Member] | Predecessor [Member]
Operating revenues [Abstract]
Electric operating revenues				$ 1,096
Natural gas operating revenues				57
Operating revenues from affiliates				0
Revenues				1,153
Operating expenses
Purchased power and fuel				471
Purchased fuel				26
Purchased power from affiliate				0
Operating and maintenance				294
Operating and maintenance from affiliates				0
Depreciation and amortization				152
Taxes other than income				105
Total operating expenses				1,048
Operating income				105
Other income and (deductions)
Interest expense, net				(65)
Other, net				(4)
Total other income and (deductions)				(69)
Income before income taxes				36
Income taxes				17
Net income				19
Other comprehensive income (loss), net of income taxes
Actuarial loss reclassified to periodic benefit cost				1
Other comprehensive (loss) income				1
Comprehensive income				$ 20
Pepco Holdings LLC [Member] | Successor [Member]
Operating revenues [Abstract]
Electric operating revenues	$ 90	1,097
Natural gas operating revenues	3	66
Operating revenues from affiliates	12	12
Revenues	105	1,175
Operating expenses
Purchased power and fuel	26	288
Purchased fuel	1	29
Purchased power from affiliate	11	144
Operating and maintenance	447	223
Operating and maintenance from affiliates	2	33
Depreciation and amortization	14	167
Taxes other than income	15	111
Total operating expenses	516	995
Operating income	(411)	180
Other income and (deductions)
Interest expense, net	(6)	(62)
Other, net	2	13
Total other income and (deductions)	(4)	(49)
Income before income taxes	(415)	131
Income taxes	(106)	(9)
Net income	(309)	140
Other comprehensive income (loss), net of income taxes
Actuarial loss reclassified to periodic benefit cost	0	0
Other comprehensive (loss) income	0	0
Comprehensive income	$ (309)	140
Potomac Electric Power Company [Member]
Operating revenues [Abstract]
Electric operating revenues		529	550
Operating revenues from affiliates		1	1
Revenues		530	551
Operating expenses
Purchased power and fuel		83	191
Purchased power from affiliate		83	6
Operating and maintenance		101	288
Operating and maintenance from affiliates		12	2
Depreciation and amortization		82	75
Taxes other than income		90	94
Total operating expenses		451	656
Operating income		79	(105)
Other income and (deductions)
Interest expense, net		(29)	(37)
Other, net		8	9
Total other income and (deductions)		(21)	(28)
Income before income taxes		58	(133)
Income taxes		0	(25)
Net income		58	(108)
Other comprehensive income (loss), net of income taxes
Comprehensive income		58	(108)
Delmarva Power and Light Company [Member]
Operating revenues [Abstract]
Electric operating revenues		294	301
Natural gas operating revenues		66	59
Operating revenues from affiliates		2	2
Revenues		362	362
Operating expenses
Purchased power		77	147
Purchased fuel		29	25
Purchased power from affiliate		51	4
Operating and maintenance		66	204
Operating and maintenance from affiliates		7	0
Depreciation and amortization		39	39
Taxes other than income		15	15
Total operating expenses		284	434
Operating income		78	(72)
Other income and (deductions)
Interest expense, net		(13)	(12)
Other, net		3	3
Total other income and (deductions)		(10)	(9)
Income before income taxes		68	(81)
Income taxes		11	(9)
Net income		57	(72)
Other comprehensive income (loss), net of income taxes
Comprehensive income		57	(72)
Atlantic City Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues		274	290
Operating revenues from affiliates		1	1
Revenues		275	291
Operating expenses
Purchased power and fuel		128	157
Purchased power from affiliate		9	1
Operating and maintenance		69	211
Operating and maintenance from affiliates		7	1
Depreciation and amortization		35	40
Taxes other than income		2	2
Total operating expenses		250	412
Operating income		25	(121)
Other income and (deductions)
Interest expense, net		(15)	(16)
Other, net		2	4
Total other income and (deductions)		(13)	(12)
Income before income taxes		12	(133)
Income taxes		(16)	(33)
Net income		28	(100)
Other comprehensive income (loss), net of income taxes
Comprehensive income		$ 28	$ (100)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 23, 2016
Cash flows from operating activities
Net income		$ 981	$ 123
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		1,274	1,063
Impairment of long-lived assets		10	119
Gain on sales of assets		(4)	(9)
Business Combination, Bargain Purchase, Gain Recognized, Amount		(226)	0
Deferred income taxes and amortization of investment tax credits		189	127
Net fair value changes related to derivatives		47	(107)
Gain (Loss) on Investments		175	55
Other non-cash operating activities		118	804
Changes in assets and liabilities:
Accounts receivable		313	117
Inventories		109	142
Accounts payable and accrued expenses		(623)	(571)
Option premiums (paid) received, net		(6)	17
Increase (Decrease) Cash Collateral from Counterparties		(110)	206
Income taxes		50	47
Pension and non-pension postretirement benefit contributions		(307)	(239)
Other assets and liabilities		(439)	(311)
Net cash flows provided by (used in) operating activities		1,201	1,473
Cash flows from investing activities
Capital expenditures		(2,114)	(2,202)
Proceeds from nuclear decommissioning trust fund sales		1,767	2,240
Investment in nuclear decommissioning trust funds		(1,833)	(2,297)
Acquisition of businesses, net		(212)	(6,645)
Proceeds from termination of direct financing lease investment		0	360
Change in restricted cash		(1)	(2)
Other investing activities		(18)	(2)
Net cash flows provided by (used in) investing activities		(2,411)	(8,548)
Cash flows from financing activities
Changes in short-term borrowings		721	1,647
Proceeds from short-term borrowings with maturities greater than 90 days		560	123
Repayments of Short-term Debt, Maturing in More than Three Months		(500)	0
Issuance of long-term debt		763	151
Retirement of long-term debt		(65)	(116)
Dividends paid on common stock		(303)	(287)
Proceeds from employee stock plans		12	9
Other financing activities		(4)	6
Net cash flows provided by (used in) financing activities		1,184	1,533
Increase (Decrease) in cash and cash equivalents		(26)	(5,542)
Cash and cash equivalents at beginning of period		635	6,502	$ 6,502
Cash and cash equivalents at end of period	$ 960	609	960
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income		409	257
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		678	667
Impairment of long-lived assets		10	119
Gain on sales of assets		(4)	0
Business Combination, Bargain Purchase, Gain Recognized, Amount		(226)	0
Deferred income taxes and amortization of investment tax credits		112	68
Net fair value changes related to derivatives		51	(106)
Gain (Loss) on Investments		175	55
Other non-cash operating activities		(10)	51
Changes in assets and liabilities:
Accounts receivable		195	173
Change Receivables Payables From Affiliates		23	(17)
Inventories		81	93
Accounts payable and accrued expenses		62	(363)
Option premiums (paid) received, net		(6)	17
Increase (Decrease) Cash Collateral from Counterparties		(102)	198
Income taxes		(81)	(60)
Pension and non-pension postretirement benefit contributions		(110)	(112)
Other assets and liabilities		(167)	(148)
Net cash flows provided by (used in) operating activities		740	782
Cash flows from investing activities
Capital expenditures		(923)	(1,125)
Proceeds from nuclear decommissioning trust fund sales		1,767	2,240
Investment in nuclear decommissioning trust funds		(1,833)	(2,297)
Acquisition of businesses, net		(212)	(1)
Change in restricted cash		18	4
Other investing activities		(29)	(25)
Net cash flows provided by (used in) investing activities		(1,212)	(1,204)
Cash flows from financing activities
Changes in short-term borrowings		(42)	1,377
Proceeds from Debt, Maturing in More than Three Months		60	123
Issuance of long-term debt		762	151
Retirement of long-term debt		(30)	(94)
Distribution to member		(164)	(55)
Proceeds from Contributions from Affiliates		0	44
Change in Exelon intercompany money pool borrowings		(1)	(1,183)
Other financing activities		(3)	5
Net cash flows provided by (used in) financing activities		582	368
Increase (Decrease) in cash and cash equivalents		110	(54)
Cash and cash equivalents at beginning of period		290	431	431
Cash and cash equivalents at end of period	377	400	377
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income		141	115
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		208	189
Deferred income taxes and amortization of investment tax credits		137	70
Other non-cash operating activities		31	32
Changes in assets and liabilities:
Accounts receivable		92	69
Change Receivables Payables From Affiliates		(16)	0
Inventories		4	7
Accounts payable and accrued expenses		(327)	(207)
Increase (Decrease) Cash Collateral from Counterparties		(7)	7
Income taxes		(34)	20
Pension and non-pension postretirement benefit contributions		(35)	(32)
Other assets and liabilities		(49)	14
Net cash flows provided by (used in) operating activities		145	284
Cash flows from investing activities
Capital expenditures		(535)	(639)
Change in restricted cash		(1)	0
Other investing activities		7	13
Net cash flows provided by (used in) investing activities		(529)	(626)
Cash flows from financing activities
Changes in short-term borrowings		365	349
Dividends paid on common stock		(105)	(91)
Contributions from parent		100	39
Other financing activities		(1)	(1)
Net cash flows provided by (used in) financing activities		359	296
Increase (Decrease) in cash and cash equivalents		(25)	(46)
Cash and cash equivalents at beginning of period		56	67	67
Cash and cash equivalents at end of period	21	31	21
PECO Energy Co [Member]
Cash flows from operating activities
Net income		127	124
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		71	67
Deferred income taxes and amortization of investment tax credits		24	23
Other non-cash operating activities		23	24
Changes in assets and liabilities:
Accounts receivable		(25)	(51)
Change Receivables Payables From Affiliates		(10)	4
Inventories		19	24
Accounts payable and accrued expenses		(82)	18
Income taxes		25	29
Pension and non-pension postretirement benefit contributions		(23)	(29)
Other assets and liabilities		(85)	(95)
Net cash flows provided by (used in) operating activities		64	138
Cash flows from investing activities
Capital expenditures		(159)	(195)
Changes in Exelon intercompany money pool		131	(160)
Other investing activities		1	4
Net cash flows provided by (used in) investing activities		(27)	(351)
Cash flows from financing activities
Dividends paid on common stock		(72)	(69)
Net cash flows provided by (used in) financing activities		(72)	(69)
Increase (Decrease) in cash and cash equivalents		(35)	(282)
Cash and cash equivalents at beginning of period		63	295	295
Cash and cash equivalents at end of period	13	28	13
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income		125	101
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		128	109
Deferred income taxes and amortization of investment tax credits		72	26
Other non-cash operating activities		24	44
Changes in assets and liabilities:
Accounts receivable		(7)	(44)
Change Receivables Payables From Affiliates		(7)	7
Inventories		17	17
Accounts payable and accrued expenses		(121)	3
Income taxes		33	78
Pension and non-pension postretirement benefit contributions		(44)	(38)
Other assets and liabilities		(52)	(30)
Net cash flows provided by (used in) operating activities		168	273
Cash flows from investing activities
Capital expenditures		(166)	(176)
Change in restricted cash		(19)	(20)
Other investing activities		4	5
Net cash flows provided by (used in) investing activities		(181)	(191)
Cash flows from financing activities
Changes in short-term borrowings		50	(60)
Dividends paid on common stock		(49)	(45)
Dividends paid on preference stock		0	(3)
Contributions from parent		0	21
Other financing activities		0	1
Net cash flows provided by (used in) financing activities		1	(86)
Increase (Decrease) in cash and cash equivalents		(12)	(4)
Cash and cash equivalents at beginning of period		23	9	9
Cash and cash equivalents at end of period	5	11	5
Pepco Holdings LLC [Member] | Successor [Member]
Cash flows from operating activities
Net income	(309)	140
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	14	167
Deferred income taxes and amortization of investment tax credits	(112)	13
Net fair value changes related to derivatives	0	0
Other non-cash operating activities	410	(8)
Changes in assets and liabilities:
Accounts receivable	16	68
Change Receivables Payables From Affiliates	0	(8)
Inventories	0	(11)
Accounts payable and accrued expenses	(4)	(81)
Income taxes	7	55
Pension and non-pension postretirement benefit contributions	0	(66)
Other assets and liabilities	(25)	(75)
Net cash flows provided by (used in) operating activities	(3)	194
Cash flows from investing activities
Capital expenditures	(29)	(320)
Purchases of investments	(2)	0
Change in restricted cash	(1)	2
Other investing activities	2	(3)
Net cash flows provided by (used in) investing activities	(30)	(321)
Cash flows from financing activities
Changes in short-term borrowings	(20)	145
Proceeds from short-term borrowings with maturities greater than 90 days	0	0
Repayments of Debt, Maturing in More than Three Months	0	(500)
Issuance of long-term debt	0	1
Retirement of long-term debt	0	(24)
Common stock issued for the Direct Stock Purchase and Dividend Reinvestment Plan and employee-related compensation	0	0
Distribution to member	(108)	(69)
Contributions from parent	0	500
Change in Exelon intercompany money pool borrowings	(7)	13
Other financing activities	0	0
Net cash flows provided by (used in) financing activities	(135)	66
Increase (Decrease) in cash and cash equivalents	(168)	(61)
Cash and cash equivalents at beginning of period	319	170
Cash and cash equivalents at end of period	151	109	151	319
Pepco Holdings LLC [Member] | Predecessor [Member]
Cash flows from operating activities
Net income				19
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization				152
Deferred income taxes and amortization of investment tax credits				19
Net fair value changes related to derivatives				18
Other non-cash operating activities				46
Changes in assets and liabilities:
Accounts receivable				(28)
Change Receivables Payables From Affiliates				0
Inventories				(4)
Accounts payable and accrued expenses				42
Income taxes				12
Pension and non-pension postretirement benefit contributions				(4)
Other assets and liabilities				(8)
Net cash flows provided by (used in) operating activities				264
Cash flows from investing activities
Capital expenditures				(273)
Purchases of investments				(68)
Change in restricted cash				3
Other investing activities				(5)
Net cash flows provided by (used in) investing activities				(343)
Cash flows from financing activities
Changes in short-term borrowings				(121)
Proceeds from short-term borrowings with maturities greater than 90 days				500
Repayments of Debt, Maturing in More than Three Months				0
Issuance of long-term debt				0
Retirement of long-term debt				(11)
Common stock issued for the Direct Stock Purchase and Dividend Reinvestment Plan and employee-related compensation				2
Distribution to member				0
Contributions from parent				0
Change in Exelon intercompany money pool borrowings				0
Other financing activities				2
Net cash flows provided by (used in) financing activities				372
Increase (Decrease) in cash and cash equivalents				293
Cash and cash equivalents at beginning of period	319		26	26
Cash and cash equivalents at end of period				319
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income		58	(108)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		82	75
Deferred income taxes and amortization of investment tax credits		5	(31)
Other non-cash operating activities		(15)	153
Changes in assets and liabilities:
Accounts receivable		45	(24)
Change Receivables Payables From Affiliates		(6)	55
Inventories		(10)	1
Accounts payable and accrued expenses		(49)	(4)
Income taxes		20	151
Pension and non-pension postretirement benefit contributions		(64)	(1)
Other assets and liabilities		(37)	(9)
Net cash flows provided by (used in) operating activities		29	258
Cash flows from investing activities
Capital expenditures		(139)	(109)
Purchases of investments		0	(31)
Change in restricted cash		0	2
Other investing activities		(5)	2
Net cash flows provided by (used in) investing activities		(144)	(136)
Cash flows from financing activities
Changes in short-term borrowings		144	(64)
Issuance of long-term debt		1	0
Dividends paid on common stock		(30)	(39)
Other financing activities		(1)	0
Net cash flows provided by (used in) financing activities		114	(103)
Increase (Decrease) in cash and cash equivalents		(1)	19
Cash and cash equivalents at beginning of period		9	5	5
Cash and cash equivalents at end of period	24	8	24
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income		57	(72)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		39	39
Deferred income taxes and amortization of investment tax credits		13	(4)
Other non-cash operating activities		(7)	118
Changes in assets and liabilities:
Accounts receivable		6	4
Change Receivables Payables From Affiliates		1	20
Inventories		1	1
Accounts payable and accrued expenses		14	(3)
Income taxes		21	52
Other assets and liabilities		(23)	(8)
Net cash flows provided by (used in) operating activities		122	147
Cash flows from investing activities
Capital expenditures		(82)	(81)
Other investing activities		2	0
Net cash flows provided by (used in) investing activities		(80)	(81)
Cash flows from financing activities
Changes in short-term borrowings		0	(30)
Retirement of long-term debt		(14)	0
Dividends paid on common stock		(30)	(38)
Net cash flows provided by (used in) financing activities		(44)	(68)
Increase (Decrease) in cash and cash equivalents		(2)	(2)
Cash and cash equivalents at beginning of period		46	5	5
Cash and cash equivalents at end of period	3	44	3
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income		28	(100)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization		35	40
Deferred income taxes and amortization of investment tax credits		(7)	(33)
Other non-cash operating activities		2	132
Changes in assets and liabilities:
Accounts receivable		14	5
Change Receivables Payables From Affiliates		(5)	20
Inventories		(1)	(2)
Accounts payable and accrued expenses		(5)	19
Income taxes		3	168
Other assets and liabilities		(6)	(3)
Net cash flows provided by (used in) operating activities		58	246
Cash flows from investing activities
Capital expenditures		(88)	(101)
Change in restricted cash		2	1
Other investing activities		1	0
Net cash flows provided by (used in) investing activities		(85)	(100)
Cash flows from financing activities
Changes in short-term borrowings		0	(5)
Retirement of long-term debt		(10)	(11)
Dividends paid on common stock		(10)	(11)
Net cash flows provided by (used in) financing activities		(20)	(27)
Increase (Decrease) in cash and cash equivalents		(47)	119
Cash and cash equivalents at beginning of period		101	3	$ 3
Cash and cash equivalents at end of period	$ 122	$ 54	$ 122

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Assets, Current [Abstract]
Cash and cash equivalents		$ 609	$ 635
Restricted cash and cash equivalents		254	253
Accounts receivable, net
Customer		3,886	4,158
Other		1,133	1,201
Mark-to-market derivative assets		847	917
Unamortized energy contract assets		103	88
Inventories, net
Fossil fuel and emission allowances		249	364
Materials and supplies		1,312	1,274
Prepaid Taxes		1,250	1,250
Regulatory assets		1,330	1,342
Other		1,221	930
Total current assets		12,194	12,412
Property, plant and equipment, net		72,630	71,555
Deferred debits and other assets
Regulatory assets		10,051	10,046
Nuclear decommissioning trust funds		12,362	11,061
Investments		648	629
Goodwill		6,677	6,677
Mark-to-market derivative assets		539	492
Pledged assets for Zion Station decommissioning		95	113
Unamortized energy contract assets		432	447
Other		1,440	1,472
Total deferred debits and other assets		32,244	30,937
Total assets		117,068	114,904
Liabilities, Current [Abstract]
Short-term borrowings		2,048	1,267
Long-term debt due within one year		3,645	2,430
Accounts payable		3,011	3,441
Accrued expenses		3,007	3,460
Payables to affiliates		8	8
Unamortized energy contract liabilities		388	407
Regulatory liabilities		637	602
Mark-to-market derivative liabilities (current liabilities)		228	282
Energy Marketing Accounts Payable		400	428
Accounts Payable and Accrued Liabilities, Current		123	151
Other		942	981
Total current liabilities		14,437	13,457
Long-term debt		31,044	31,575
Long-term debt to financing trusts		641	641
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		18,518	18,138
Asset Retirement Obligations, Noncurrent		9,634	9,111
Pension obligations		4,082	4,248
Non-pension postretirement benefit obligations		1,928	1,848
Spent nuclear fuel obligation		1,136	1,024
Regulatory liabilities		4,302	4,187
Mark-to-market derivative liabilities (noncurrent liabilities)		420	392
Unamortized energy contract liabilities		779	830
Payable for Zion Station decommissioning		3	14
Other		1,853	1,827
Total deferred credits and other liabilities		42,655	41,619
Total liabilities	[1]	88,777	87,292
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		18,807	18,794
Treasury stock, at cost (35 shares at March 31, 2017 and December 31, 2016, respectively)		(2,327)	(2,327)
Retained earnings		12,720	12,030
Accumulated other comprehensive loss, net		(2,670)	(2,660)
Total shareholders’ equity		26,530	25,837
Member’s equity
Noncontrolling interests		1,761	1,775
Total equity		28,291	27,612
Total liabilities and shareholders’ equity		117,068	114,904
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	[2]	303	502
Variable Interest Entity, Primary Beneficiary [Member]
Assets, Current [Abstract]
Cash and cash equivalents		199	150
Restricted cash and cash equivalents		124	59
Accounts receivable, net
Customer		347	371
Other		23	48
Mark-to-market derivative assets		41	31
Inventories, net
Materials and supplies		191	199
Other		58	50
Total current assets		983	908
Property, plant and equipment, net		5,425	5,415
Deferred debits and other assets
Nuclear decommissioning trust funds		2,286	2,185
Goodwill		47	47
Mark-to-market derivative assets		57	23
Other		350	315
Total assets		9,148	8,893
Liabilities, Current [Abstract]
Long-term debt due within one year		237	181
Accounts payable		275	269
Accrued expenses		85	119
Unamortized energy contract liabilities		16	15
Mark-to-market derivative liabilities (current liabilities)		18	60
Other		11	30
Total current liabilities		642	674
Long-term debt		626	641
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent	[3]	1,929	1,904
Pension obligations		8	9
Unamortized energy contract liabilities		18	22
Other		122	106
Total liabilities		3,345	3,356
Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		9,148	8,893
Deferred credits and other liabilities
Total liabilities		3,345	3,356
Exelon Generation Co L L C [Member]
Assets, Current [Abstract]
Cash and cash equivalents		400	290
Restricted cash and cash equivalents		140	158
Accounts receivable, net
Customer		2,278	2,433
Other		545	558
Mark-to-market derivative assets		847	917
Receivables from affiliates		141	156
Unamortized energy contract assets		103	88
Inventories, net
Fossil fuel and emission allowances		222	292
Materials and supplies		957	935
Other		881	701
Total current assets		6,514	6,528
Property, plant and equipment, net		25,893	25,585
Deferred debits and other assets
Nuclear decommissioning trust funds		12,362	11,061
Investments		435	418
Goodwill		47	47
Mark-to-market derivative assets		527	476
Prepaid pension asset		1,646	1,595
Pledged assets for Zion Station decommissioning		95	113
Unamortized energy contract assets		432	447
Deferred Tax Assets, Net, Noncurrent		10	16
Other		648	688
Total deferred debits and other assets		16,202	14,861
Total assets		48,609	46,974
Liabilities, Current [Abstract]
Short-term borrowings		717	699
Long-term debt due within one year		1,156	1,117
Accounts payable		1,482	1,610
Accrued expenses		720	989
Payables to affiliates		145	137
Unamortized energy contract liabilities		68	72
Other Short-term Borrowings		54	55
Mark-to-market derivative liabilities (current liabilities)		209	263
Energy Marketing Accounts Payable		400	428
Other		286	313
Total current liabilities		5,237	5,683
Long-term debt		7,904	7,202
Long-term debt to affiliate		919	922
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		5,850	5,585
Asset Retirement Obligations, Noncurrent		9,444	8,922
Non-pension postretirement benefit obligations		926	930
Spent nuclear fuel obligation		1,136	1,024
Due to Affiliate, Noncurrent		2,776	2,608
Mark-to-market derivative liabilities (noncurrent liabilities)		157	153
Unamortized energy contract liabilities		78	80
Payable for Zion Station decommissioning		3	14
Other		615	595
Total deferred credits and other liabilities		20,985	19,911
Total liabilities	[4]	35,045	33,718
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Retained earnings		2,534	2,275
Accumulated other comprehensive loss, net		(41)	(54)
Member’s equity
Members' Capital		9,310	9,261
Total member's equity		11,803	11,482
Noncontrolling interests		1,761	1,774
Total equity		13,564	13,256
Total liabilities and shareholders’ equity		48,609	46,974
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets, Current [Abstract]
Cash and cash equivalents		199	150
Restricted cash and cash equivalents		75	27
Accounts receivable, net
Customer		347	371
Other		23	48
Mark-to-market derivative assets		41	31
Inventories, net
Materials and supplies		191	199
Other		54	44
Total current assets		930	870
Property, plant and equipment, net		5,425	5,415
Deferred debits and other assets
Nuclear decommissioning trust funds		2,286	2,185
Goodwill		47	47
Mark-to-market derivative assets		57	23
Other		314	277
Total assets		9,059	8,817
Liabilities, Current [Abstract]
Long-term debt due within one year		159	99
Accounts payable		275	269
Accrued expenses		83	116
Unamortized energy contract liabilities		16	15
Mark-to-market derivative liabilities (current liabilities)		18	60
Other		11	30
Total current liabilities		562	589
Long-term debt		535	540
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent		1,929	1,904	[3]
Pension obligations		8	9
Unamortized energy contract liabilities		18	22
Other		122	106
Total liabilities		3,174	3,170
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		9,059	8,817
Deferred credits and other liabilities
Total liabilities		3,174	3,170
Commonwealth Edison Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		31	56
Restricted cash and cash equivalents		3	2
Accounts receivable, net
Customer		461	528
Other		199	218
Receivables from affiliates		360	356
Inventories, net
Inventories, net		154	159
Regulatory assets		183	190
Other		55	45
Total current assets		1,446	1,554
Property, plant and equipment, net		19,692	19,335
Deferred debits and other assets
Regulatory assets		1,032	977
Investments		6	6
Goodwill		2,625	2,625
Receivable from affiliate		2,294	2,170
Prepaid pension asset		1,330	1,343
Other		331	325
Total deferred debits and other assets		7,618	7,446
Total assets		28,756	28,335
Liabilities, Current [Abstract]
Short-term borrowings		365	0
Long-term debt due within one year		1,125	425
Accounts payable		518	645
Accrued expenses		1,061	1,250
Payables to affiliates		52	65
Customer deposits		117	121
Regulatory liabilities		311	329
Mark-to-market derivative liabilities (current liabilities)		19	19
Other		77	84
Total current liabilities		3,645	2,938
Long-term debt		5,910	6,608
Long-term debt to financing trusts		205	205
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		5,502	5,364
Asset Retirement Obligations, Noncurrent		121	119
Non-pension postretirement benefit obligations		234	239
Regulatory liabilities		3,492	3,369
Mark-to-market derivative liabilities (noncurrent liabilities)		263	239
Other		523	529
Total deferred credits and other liabilities		10,135	9,859
Total liabilities		19,895	19,610
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		1,588	1,588
Retained earnings		(1,639)	(1,639)
Other paid-in capital		6,250	6,150
Retained Earnings, Appropriated		2,662	2,626
Total shareholders’ equity		8,861	8,725
Member’s equity
Total liabilities and shareholders’ equity		28,756	28,335
PECO Energy Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		28	63
Restricted cash and cash equivalents		4	4
Accounts receivable, net
Customer		314	306
Other		122	131
Receivables from affiliates		6	4
Receivable from Exelon intercompany pool		0	131
Inventories, net
Fossil fuel and emission allowances		14	35
Materials and supplies		29	27
Prepaid Taxes		100	9
Regulatory assets		40	29
Other		21	18
Total current assets		678	757
Property, plant and equipment, net		7,659	7,565
Deferred debits and other assets
Regulatory assets		1,708	1,681
Investments		25	25
Receivable from affiliate		482	438
Prepaid pension asset		361	345
Other		19	20
Total deferred debits and other assets		2,595	2,509
Total assets		10,932	10,831
Liabilities, Current [Abstract]
Long-term debt due within one year		500	0
Accounts payable		288	342
Accrued expenses		92	104
Payables to affiliates		55	63
Customer deposits		62	61
Regulatory liabilities		161	127
Other		29	30
Total current liabilities		1,187	727
Long-term debt		2,080	2,580
Long-term debt to financing trusts		184	184
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		3,076	3,006
Asset Retirement Obligations, Noncurrent		28	28
Non-pension postretirement benefit obligations		289	289
Regulatory liabilities		530	517
Other		88	85
Total deferred credits and other liabilities		4,011	3,925
Total liabilities		7,462	7,416
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		2,473	2,473
Retained earnings		996	941
Accumulated other comprehensive loss, net		1	1
Total shareholders’ equity		3,470	3,415
Member’s equity
Total liabilities and shareholders’ equity		10,932	10,831
Baltimore Gas and Electric Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		11	23
Restricted cash and cash equivalents		43	24
Accounts receivable, net
Customer		393	395
Other		79	102
Receivables from affiliates		1	0
Inventories, net
Fossil fuel and emission allowances		10	30
Materials and supplies		41	38
Prepaid Taxes		32	15
Regulatory assets		191	208
Other		11	7
Total current assets		812	842
Property, plant and equipment, net		7,166	7,040
Deferred debits and other assets
Regulatory assets		499	504
Investments		12	12
Prepaid pension asset		322	297
Other		10	9
Total deferred debits and other assets		843	822
Total assets	[5]	8,821	8,704
Liabilities, Current [Abstract]
Short-term borrowings		95	45
Long-term debt due within one year		41	41
Accounts payable		186	205
Accrued expenses		120	175
Payables to affiliates		49	55
Customer deposits		112	110
Regulatory liabilities		67	50
Other		23	26
Total current liabilities		693	707
Long-term debt		2,282	2,281
Long-term debt to financing trusts		252	252
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		2,295	2,219
Asset Retirement Obligations, Noncurrent		20	21
Non-pension postretirement benefit obligations		202	205
Regulatory liabilities		94	110
Other		59	61
Total deferred credits and other liabilities		2,670	2,616
Total liabilities	[5]	5,897	5,856
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		1,421	1,421
Retained earnings		1,503	1,427
Total shareholders’ equity		2,924	2,848
Member’s equity
Total liabilities and shareholders’ equity		8,821	8,704
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets, Current [Abstract]
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		42	23
Accounts receivable, net
Customer		0	0
Other		0	0
Mark-to-market derivative assets		0	0
Inventories, net
Materials and supplies		0	0
Other		0	0
Total current assets		42	23
Property, plant and equipment, net		0	0
Deferred debits and other assets
Nuclear decommissioning trust funds		0	0
Goodwill		0	0
Mark-to-market derivative assets		0	0
Other		3	3
Total assets		45	26
Liabilities, Current [Abstract]
Long-term debt due within one year		41	41
Accounts payable		0	0
Accrued expenses		1	1
Unamortized energy contract liabilities		0	0
Mark-to-market derivative liabilities (current liabilities)		0	0
Other		0	0
Total current liabilities		42	42
Long-term debt			0
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent		0	0
Pension obligations	[3]	0	0
Unamortized energy contract liabilities		0	0
Other		0	0
Total liabilities		42	42
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		45	26
Deferred credits and other liabilities
Total liabilities		42	42
Pepco Holdings LLC [Member] | Successor [Member]
Assets, Current [Abstract]
Cash and cash equivalents		109	170
Restricted cash and cash equivalents		41	43
Accounts receivable, net
Customer		440	496
Other		210	283
Mark-to-market derivative assets		0
Inventories, net
Fossil fuel and emission allowances		2	6
Materials and supplies		131	116
Regulatory assets		653	653
Other		64	71
Total current assets		1,650	1,838
Property, plant and equipment, net		11,801	11,598
Deferred debits and other assets
Regulatory assets		2,791	2,851
Investments		133	133
Goodwill		4,005	4,005
Notes, Loans and Financing Receivable, Gross, Noncurrent		4	4
Mark-to-market derivative assets		0
Prepaid pension asset		549	509
Deferred Tax Assets, Net, Noncurrent		5	6
Other		80	81
Total deferred debits and other assets		7,567	7,589
Total assets		21,018	21,025
Liabilities, Current [Abstract]
Short-term borrowings		167	522
Long-term debt due within one year		241	253
Accounts payable		386	458
Accrued expenses		269	272
Payables to affiliates		84	94
Unamortized energy contract liabilities		320	335
Customer deposits		121	123
Regulatory liabilities		82	79
Other Short-term Borrowings		13
Mark-to-market derivative liabilities (current liabilities)		0
Payables to Customers		74	101
Other		43	47
Total current liabilities		1,800	2,284
Long-term debt		5,619	5,645
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		3,789	3,775
Asset Retirement Obligations, Noncurrent		14	14
Non-pension postretirement benefit obligations		129	134
Regulatory liabilities		154	158
Mark-to-market derivative liabilities (noncurrent liabilities)		0
Unamortized energy contract liabilities		701	750
Other		225	249
Total deferred credits and other liabilities		5,012	5,080
Total liabilities		12,431	13,009
Stockholders' Equity Attributable to Parent [Abstract]
Retained earnings		10	(61)
Member’s equity
Members' Capital		8,577	8,077
Total member's equity		8,587	8,016
Total equity		8,587	8,016
Total liabilities and shareholders’ equity		21,018	21,025
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Assets, Current [Abstract]
Cash and cash equivalents		0
Restricted cash and cash equivalents		7
Accounts receivable, net
Customer		0
Other		0
Mark-to-market derivative assets		0
Inventories, net
Materials and supplies		0
Other		4
Total current assets		11
Property, plant and equipment, net		0
Deferred debits and other assets
Nuclear decommissioning trust funds		0
Goodwill		0
Mark-to-market derivative assets		0
Other		33
Total assets		44
Liabilities, Current [Abstract]
Long-term debt due within one year		37
Accounts payable		0
Accrued expenses		1
Unamortized energy contract liabilities		0
Mark-to-market derivative liabilities (current liabilities)		0
Other		0
Total current liabilities		38
Long-term debt		91
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent		0
Pension obligations	[3]	0
Unamortized energy contract liabilities		0
Other		0
Total liabilities		129
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member] | Successor [Member]
Deferred debits and other assets
Total assets		44	49
Deferred credits and other liabilities
Total liabilities		129	143
Potomac Electric Power Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		8	9
Restricted cash and cash equivalents		33	33
Accounts receivable, net
Customer		199	235
Other		127	150
Inventories, net
Materials and supplies		73	63
Regulatory assets		173	162
Other		21	32
Total current assets		634	684
Property, plant and equipment, net		5,659	5,571
Deferred debits and other assets
Regulatory assets		679	690
Investments		101	102
Prepaid pension asset		337	282
Other		7	6
Total deferred debits and other assets		1,124	1,080
Total assets		7,417	7,335
Liabilities, Current [Abstract]
Short-term borrowings		167	23
Long-term debt due within one year		17	16
Accounts payable		141	209
Accrued expenses		125	113
Payables to affiliates		68	74
Customer deposits		53	53
Regulatory liabilities		10	11
Payables to Customers		47	68
Other		23	29
Total current liabilities		651	596
Long-term debt		2,333	2,333
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		1,913	1,910
Non-pension postretirement benefit obligations		41	43
Regulatory liabilities		19	20
Other		132	133
Total deferred credits and other liabilities		2,105	2,106
Total liabilities		5,089	5,035
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		1,309	1,309
Other paid-in capital		1,019	991
Total shareholders’ equity		2,328	2,300
Member’s equity
Total liabilities and shareholders’ equity		7,417	7,335
Delmarva Power and Light Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		44	46
Accounts receivable, net
Customer		131	136
Other		39	63
Receivables from affiliates		0	3
Inventories, net
Fossil fuel and emission allowances		3	7
Materials and supplies		35	32
Regulatory assets		66	59
Other		21	24
Total current assets		339	370
Property, plant and equipment, net		3,334	3,273
Deferred debits and other assets
Regulatory assets		301	289
Investments		1	0
Goodwill		8	8
Prepaid pension asset		203	206
Other		5	7
Total deferred debits and other assets		518	510
Total assets		4,191	4,153
Liabilities, Current [Abstract]
Long-term debt due within one year		109	119
Accounts payable		106	88
Accrued expenses		44	36
Payables to affiliates		36	38
Customer deposits		36	36
Regulatory liabilities		47	43
Payables to Customers		4	13
Other		6	8
Total current liabilities		388	381
Long-term debt		1,217	1,221
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		1,072	1,056
Non-pension postretirement benefit obligations		17	19
Regulatory liabilities		95	97
Other		49	53
Total deferred credits and other liabilities		1,233	1,225
Total liabilities		2,838	2,827
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		764	764
Retained earnings		589	562
Total shareholders’ equity		1,353	1,326
Member’s equity
Total liabilities and shareholders’ equity		4,191	4,153
Atlantic City Electric Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		54	101
Restricted cash and cash equivalents		7	9
Accounts receivable, net
Customer		111	125
Other		41	44
Inventories, net
Materials and supplies		23	22
Regulatory assets		94	96
Other		3	2
Total current assets		333	399
Property, plant and equipment, net		2,583	2,521
Deferred debits and other assets
Regulatory assets		407	405
Notes, Loans and Financing Receivable, Gross, Noncurrent		4	4
Prepaid pension asset		82	84
Other		42	44
Total deferred debits and other assets		535	537
Total assets		3,451	3,457
Liabilities, Current [Abstract]
Long-term debt due within one year		33	35
Accounts payable		125	132
Accrued expenses		50	38
Payables to affiliates		24	29
Customer deposits		32	33
Regulatory liabilities		25	25
Payables to Customers		22	20
Other		9	8
Total current liabilities		320	320
Long-term debt		1,112	1,120
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		911	917
Non-pension postretirement benefit obligations		33	34
Regulatory liabilities		0	0
Other		23	32
Total deferred credits and other liabilities		967	983
Total liabilities		2,399	2,423
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		912	912
Retained earnings		140	122
Total shareholders’ equity		1,052	1,034
Member’s equity
Total liabilities and shareholders’ equity		3,451	3,457
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets, Current [Abstract]
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		7	9
Accounts receivable, net
Customer		0	0
Other		0	0
Mark-to-market derivative assets		0	0
Inventories, net
Materials and supplies		0	0
Other		0	0
Total current assets		7	9
Property, plant and equipment, net		0	0
Deferred debits and other assets
Nuclear decommissioning trust funds		0	0
Goodwill		0	0
Mark-to-market derivative assets		0	0
Other		23	23
Total assets		30	32
Liabilities, Current [Abstract]
Long-term debt due within one year		33	35
Accounts payable		0	0
Accrued expenses		1	2
Unamortized energy contract liabilities		0	0
Mark-to-market derivative liabilities (current liabilities)		0	0
Other		0	0
Total current liabilities		34	37
Long-term debt		81	89
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent		0	0
Pension obligations	[3]	0	0
Unamortized energy contract liabilities		0	0
Other		0	0
Total liabilities		115	126
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Member’s equity
Noncontrolling Interest in Variable Interest Entity		30	32
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities		$ 115	$ 126
[1]	Exelon’s consolidated assets include $9,148 million and $8,893 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,345 million and $3,356 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 3 - Variable Interest Entities.
[2]	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.
[3]	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 Consolidated Balance Sheets. See Note 13 - Retirement Benefits for additional details.
[4]	Generation’s consolidated assets include $9,059 million and $8,817 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,174 million and $3,170 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 3 - Variable Interest Entities.
[5]	BGE’s consolidated assets include $45 million and $26 million at March 31, 2017 and December 31, 2016, 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 $42 million at March 31, 2017 and December 31, 2016, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 3 - Variable Interest Entities.

Consolidated Balance Sheets (U5

Consolidated Balance Sheets (Unaudited) (Parenthetical) - shares	Mar. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common Stock, Shares Authorized	2,000,000,000	2,000,000,000
Common Stock, Shares, Outstanding	926,096,660	919,924,742
Treasury Stock, Shares held	34,743,157	34,743,157

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders Equity (Unaudited) - USD ($) shares in Thousands, $ in Millions		Total	Common Stock [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]		Noncontrolling Interest [Member]	Exelon Generation Co L L C [Member]	Exelon Generation Co L L C [Member]Membership Interest [Member]	Exelon Generation Co L L C [Member]Undistributed Earnings [Member]	Exelon Generation Co L L C [Member]Accumulated Other Comprehensive Income (Loss) [Member]		Exelon Generation Co L L C [Member]Noncontrolling Interest [Member]	Commonwealth Edison Co [Member]	Commonwealth Edison Co [Member]Common Stock [Member]	Commonwealth Edison Co [Member]Other Additional Capital [Member]	Commonwealth Edison Co [Member]Retained Earnings, Unappropriated [Member]	Commonwealth Edison Co [Member]Retained Earnings, Appropriated [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]		Baltimore Gas and Electric Company [Member]	Baltimore Gas and Electric Company [Member]Common Stock [Member]	Baltimore Gas and Electric Company [Member]Retained Earnings [Member]	Pepco Holdings LLC [Member]	Pepco Holdings LLC [Member]Membership Interest [Member]	Pepco Holdings LLC [Member]Undistributed Earnings [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]
Beginning Balance at Dec. 31, 2015	[1]					$ (2,624)						$ (63)											$ 1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		$ 123							$ 257						$ 115					$ 124					$ 101						$ (108)			$ (72)			$ (100)
Other Comprehensive Income (Loss), Net of Tax		$ 28				28	[1]		(1)			(1)	[1]										0
Proceeds from Contributions from Parent															39										21
Ending Balance at Mar. 31, 2016	[1]					(2,596)						(64)											1
Beginning Balance at Dec. 31, 2015	[1]					(2,624)						(63)											1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Successor [Member]																												$ (309)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																												0
Proceeds from Contributions from Parent | Successor [Member]																												0
Ending Balance at Mar. 31, 2016	[1]					(2,596)						(64)											1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings, Appropriated															(2,626)
Beginning Balance (in shares) at Dec. 31, 2016		958,778
Beginning Balance at Dec. 31, 2016		$ 27,612	$ 18,794	$ (2,327)	$ 12,030	(2,660)	[1]	$ 1,775				(54)	[1]										1	[1]
Beginning Balance at Dec. 31, 2016		25,837													8,725	$ 1,588	$ 6,150	$ (1,639)	$ 2,626	3,415	$ 2,473	$ 941	1		2,848	$ 1,421	$ 1,427				2,300	$ 1,309	$ 991	1,326	$ 764	$ 562	1,034	$ 912	$ 122
Beginning Balance (Successor [Member]) at Dec. 31, 2016																												8,016	$ 8,077	$ (61)
Beginning Balance at Dec. 31, 2016									13,256	$ 9,261	$ 2,275	(54)		$ 1,774
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Successor [Member]																												140		140
Net income		$ 981	0	0	995	0		(14)	409		423	0		(14)	141			141		127		127			125		125				58		58	57		57	28		28
Stock Issued During Period, Shares, Share-based Compensation, Gross		1,739
Stock Issued During Period, Value, Share-based Compensation, Gross		$ 1	1	0	0	0		0
Stock Issued During Period, Shares, Employee Stock Purchase Plans		323
Stock Issued During Period, Value, Employee Stock Purchase Plan		$ 12	12	0	0	0		0
Noncontrolling Interest, Period Increase (Decrease)		2	0	0	0	0		2
Noncontrolling Interest, Increase from Sale of Parent Equity Interest									3					3
Income Tax Effects Allocated Directly to Equity, Other									49	(49)
Common stock dividends		(305)	0	0	(305)	0		0												(72)		(72)			(49)		(49)							(30)		(30)	(10)		(10)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																												0
Other Comprehensive Income (Loss), Net of Tax		(12)	0	0	0	(10)	[1]	(2)	11		0	13	[1]	(2)									0	[1]
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared | Successor [Member]																												(69)		69
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared											(164)
Employee stock purchase plan issuances		$ 12	12	0	0	0		0
Adjustments to Additional Paid in Capital, Other | Successor [Member]																												500
Adjustments to Additional Paid in Capital, Other															100		100
Dividends															(105)				(105)												(30)		(30)
Proceeds from Contributions from Parent | Successor [Member]																												500	500
Proceeds from Contributions from Parent															100										0
Ending Balance (in shares) at Mar. 31, 2017		960,840
Ending Balance at Mar. 31, 2017		$ 28,291	$ 18,807	$ (2,327)	$ 12,720	$ (2,670)	[1]	$ 1,761				(41)	[1]										1	[1]
Ending Balance at Mar. 31, 2017		$ 26,530													8,861	$ 1,588	$ 6,250	(1,639)	2,662	$ 3,470	$ 2,473	$ 996	$ 1		$ 2,924	$ 1,421	$ 1,503				$ 2,328	$ 1,309	$ 1,019	$ 1,353	$ 764	$ 589	$ 1,052	$ 912	$ 140
Ending Balance (Successor [Member]) at Mar. 31, 2017																												$ 8,587	$ 8,577	$ 10
Ending Balance at Mar. 31, 2017									$ 13,564	$ 9,310	$ 2,534	$ (41)		$ 1,761
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings, Appropriated															$ (2,662)			$ (141)	$ (141)
[1]	All amounts are net of tax and noncontrolling interest. Amounts in parenthesis represent a decrease in AOCI.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation (Exelon, Generation, ComEd, PECO and BGE)	1 . 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, which sells electricity and natural gas to both wholesale and retail customers. 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) As a result of 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. In the second quarter of 2016, an error was identified and corrected related to the PHI successor period Consolidated Statement of Cash Flows for the period March 24, 2016 to March 31, 2016. The $46 million classification error related to the presentation of changes in Receivables from and payables to affiliates, net within Cash flows from operating activities and Change in Exelon intercompany money pool within Cash flows from financing activities. As revised for the first quarter of 2017, the successor period statement of cash flows for the period March 24, 2016 to March 31, 2016 presents Cash flows used in operating activities of $3 million , a decrease of $46 million from the originally reported amount, and Cash flows used in financing activities of $135 million , a decrease of $46 million from the originally reported amount. Management has concluded that the error is not material to the previously issued financial statements. Each of the Registrant’s Consolidated Financial Statements includes the accounts of its subsidiaries. All intercompany transactions have been eliminated. The accompanying consolidated financial statements as of March 31, 2017 and 2016 and for the three months then ended are unaudited but, in the opinion of the management of each Registrant include all adjustments that are considered necessary for a fair statement of the Registrants’ respective financial statements in accordance with GAAP. All adjustments are of a normal, recurring nature, except as otherwise disclosed. The December 31, 2016 Consolidated Balance Sheets were derived from audited financial statements. Financial results for interim periods are not necessarily indicative of results that may be expected for any other interim period or for the fiscal year ending December 31, 2017 . These Combined Notes to Consolidated Financial Statements have been prepared pursuant to the rules and regulations of the SEC for Quarterly Reports on Form 10-Q. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations.
Earnings Per Share, Policy [Policy Text Block]	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.
Fair Value of Financial Instruments, Policy [Policy Text Block]	Valuation Techniques Used to Determine Fair Value The following describes the valuation techniques used to measure the fair value of the assets and liabilities shown in the tables above. Cash Equivalents (Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE). The Registrants’ cash equivalents include investments with maturities of three months or less when purchased. The cash equivalents shown in the fair value tables are comprised of investments in mutual and money market funds. The fair values of the shares of these funds are based on observable market prices and, therefore, have been categorized in Level 1 in the fair value hierarchy. Preferred Stock Derivative (PHI). In connection with entering into the PHI Merger Agreement, PHI entered into a Subscription Agreement with Exelon dated April 29, 2014, pursuant to which PHI issued to Exelon shares of Preferred stock. 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. These Preferred stock derivatives were valued quarterly using quantitative and qualitative factors, including management’s assessment of the likelihood of a Regulatory Termination and therefore, were categorized in Level 3 in the fair value hierarchy. As a result of the PHI Merger, the PHI Preferred stock derivative was reduced to zero as of March 23, 2016 . The write-off was charged to Other, net on the PHI Consolidated Statement of Operations and Comprehensive Income. Nuclear Decommissioning Trust Fund Investments and Pledged Assets for Zion Station Decommissioning (Exelon and Generation). The trust fund investments have been established to satisfy Generation’s and CENG's nuclear decommissioning obligations as required by the NRC. The NDT funds hold debt and equity securities directly and indirectly through commingled funds and mutual funds, which are included in Equities and Fixed Income. Generation’s and CENG's NDT fund investments policies outline investment guidelines for the trusts and limit the trust funds’ exposures to investments in highly illiquid markets and other alternative investments. Investments with maturities of three months or less when purchased, including certain short-term fixed income securities are considered cash equivalents and included in the recurring fair value measurements hierarchy as Level 1 or Level 2. With respect to individually held equity securities, the trustees obtain prices from pricing services, whose prices are generally obtained from direct feeds from market exchanges, which Generation is able to independently corroborate. The fair values of equity securities held directly by the trust funds which are based on quoted prices in active markets are categorized in Level 1. Certain equity securities have been categorized as Level 2 because they are based on evaluated prices that reflect observable market information, such as actual trade information or similar securities. Equity securities held individually are primarily traded on the New York Stock Exchange and NASDAQ-Global Select Market, which contain only actively traded securities due to the volume trading requirements imposed by these exchanges. For fixed income securities, multiple prices from pricing services are obtained whenever possible, which enables cross-provider validations in addition to checks for unusual daily movements. A primary price source is identified based on asset type, class or issue for each security. With respect to individually held fixed income securities, the trustees monitor prices supplied by pricing services and may use a supplemental price source or change the primary price source of a given security if the portfolio managers challenge an assigned price and the trustees determine that another price source is considered to be preferable. Generation has obtained an understanding of how these prices are derived, including the nature and observability of the inputs used in deriving such prices. Additionally, Generation selectively corroborates the fair values of securities by comparison to other market-based price sources. U.S. Treasury securities are categorized as Level 1 because they trade in a highly liquid and transparent market. The fair values of fixed income securities, excluding U.S. Treasury securities, are based on evaluated prices that reflect observable market information, such as actual trade information or similar securities, adjusted for observable differences and are categorized in Level 2. The fair values of private placement fixed income securities, which are included in Corporate debt, are determined using a third party valuation that contains significant unobservable inputs and are categorized in Level 3. Equity and fixed income commingled funds and mutual funds are maintained by investment companies and hold certain investments in accordance with a stated set of fund objectives such as holding short term fixed income securities or tracking the performance of certain equity indices by purchasing equity securities to replicate the capitalization and characteristics of the indices. The values of some of these funds are publicly quoted. For mutual funds which are publicly quoted, the funds are valued based on quoted prices in active markets and have been categorized as Level 1. For commingled funds and mutual funds, which are not publicly quoted, the funds are valued using NAV as a practical expedient for fair value, which is primarily derived from the quoted prices in active markets on the underlying securities, and are not classified within the fair value hierarchy. These investments typically can be redeemed monthly with 30 or less days of notice and without further restrictions. Derivative instruments consisting primarily of futures and interest rate swaps to manage risk are recorded at fair value. Over the counter derivatives are valued daily based on quoted prices in active markets and trade in open markets, and have been categorized as Level 1. Derivative instruments other than over the counter derivatives are valued based on external price data of comparable securities and have been categorized as Level 2. Middle market lending are investments in loans or managed funds which lend to private companies. Generation elected the fair value option for its investments in certain limited partnerships that invest in middle market lending managed funds. The fair value of these loans is determined using a combination of valuation models including cost models, market models and income models. Investments in loans are categorized as Level 3 because the fair value of these securities is based largely on inputs that are unobservable and utilize complex valuation models. Managed funds are valued using NAV or its equivalent as a practical expedient, and therefore, are not classified within the fair value hierarchy. Investments in middle market lending typically cannot be redeemed until maturity of the term loan. Private equity and real estate investments include those in limited partnerships that invest in operating companies and real estate holding companies that are not publicly traded on a stock exchange, such as, leveraged buyouts, growth capital, venture capital, distressed investments, investments in natural resources, and direct investments in pools of real estate properties. The fair value of private equity and real estate investments is determined using NAV or its equivalent as a practical expedient, and therefore, are not classified within the fair value hierarchy. These investments typically cannot be redeemed and are generally liquidated over a period of 8 to 10 years from the initial investment date. Private equity and real estate valuations are reported by the fund manager and are based on the valuation of the underlying investments, which include inputs such as cost, operating results, discounted future cash flows, market based comparable data, and independent appraisals from sources with professional qualifications. These valuation inputs are unobservable. As of March 31, 2017 , Generation has outstanding commitments to invest in middle market lending, private equity investments and real estate investments of approximately $290 million , $120 million , and $107 million , respectively. These commitments will be funded by Generation’s existing nuclear decommissioning trust funds. Concentrations of Credit Risk . Generation evaluated its NDT portfolios for the existence of significant concentrations of credit risk as of March 31, 2017 . Types of concentrations that were evaluated include, but are not limited to, investment concentrations in a single entity, type of industry, foreign country, and individual fund. As of March 31, 2017 , there were no significant concentrations (generally defined as greater than 10 percent) of risk in Generation's NDT assets. See Note 12 — Nuclear Decommissioning for further discussion on the NDT fund investments. Rabbi Trust Investments (Exelon, Generation, PECO, BGE, PHI, Pepco, DPL and ACE). The Rabbi trusts were established to hold assets related to deferred compensation plans existing for certain active and retired members of Exelon’s executive management and directors. The Rabbi trusts assets are included in investments in the Registrants’ Consolidated Balance Sheets and consist primarily of money market funds, mutual funds, fixed income securities and life insurance policies. The mutual funds are maintained by investment companies and hold certain investments in accordance with a stated set of fund objectives, which are consistent with Exelon’s overall investment strategy. Money market funds and mutual funds are publicly quoted and have been categorized as Level 1 given the clear observability of the prices. The fair values of fixed income securities are based on evaluated prices that reflect observable market information, such as actual trade information or similar securities, adjusted for observable differences and are categorized in Level 2. The life insurance policies are valued using the cash surrender value of the policies, net of loans against those policies, which is provided by a third-party. Certain life insurance policies, which consist primarily of mutual funds that are priced based on observable market data, have been categorized as Level 2 because the life insurance policies can be liquidated at the reporting date for the value of the underlying assets. Life insurance policies that are valued using unobservable inputs have been categorized as Level 3. Mark-to-Market Derivatives (Exelon, Generation, ComEd, PHI and DPL) . Derivative contracts are traded in both exchange-based and non-exchange-based markets. Exchange-based derivatives that are valued using unadjusted quoted prices in active markets are categorized in Level 1 in the fair value hierarchy. Certain derivatives’ pricing is verified using indicative price quotations available through brokers or over-the-counter, on-line exchanges and are categorized in Level 2. These price quotations reflect the average of the bid-ask, mid-point prices and are obtained from sources that the Registrants believe provide the most liquid market for the commodity. The price quotations are reviewed and corroborated to ensure the prices are observable and representative of an orderly transaction between market participants. This includes consideration of actual transaction volumes, market delivery points, bid-ask spreads and contract duration. The remainder of derivative contracts are valued using the Black model, an industry standard option valuation model. The Black model takes into account inputs such as contract terms, including maturity, and market parameters, including assumptions of the future prices of energy, interest rates, volatility, credit worthiness and credit spread. For derivatives that trade in liquid markets, such as generic forwards, swaps and options, model inputs are generally observable. Such instruments are categorized in Level 2. The Registrants’ derivatives are predominately at liquid trading points. For derivatives that trade in less liquid markets with limited pricing information model inputs generally would include both observable and unobservable inputs. These valuations may include an estimated basis adjustment from an illiquid trading point to a liquid trading point for which active price quotations are available. Such instruments are categorized in Level 3. Exelon may utilize fixed-to-floating interest rate swaps, which are typically designated as fair value hedges, as a means to achieve its targeted level of variable-rate debt as a percent of total debt. In addition, the Registrants may utilize interest rate derivatives to lock in interest rate levels in anticipation of future financings. These interest rate derivatives are typically designated as cash flow hedges. Exelon determines the current fair value by calculating the net present value of expected payments and receipts under the swap agreement, based on and discounted by the market's expectation of future interest rates. Additional inputs to the net present value calculation may include the contract terms, counterparty credit risk and other market parameters. As these inputs are based on observable data and valuations of similar instruments, the interest rate swaps are categorized in Level 2 in the fair value hierarchy. See Note 9 - Derivative Financial Instruments for further discussion on mark-to-market derivatives. Deferred Compensation Obligations (Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE). The Registrants’ deferred compensation plans allow participants to defer certain cash compensation into a notional investment account. The Registrants include such plans in other current and noncurrent liabilities in their Consolidated Balance Sheets. The value of the Registrants’ deferred compensation obligations is based on the market value of the participants’ notional investment accounts. The underlying notional investments are comprised primarily of equities, mutual funds, commingled funds, and fixed income securities which are based on directly and indirectly observable market prices. Since the deferred compensation obligations themselves are not exchanged in an active market, they are categorized as Level 2 in the fair value hierarchy. The value of certain employment agreement obligations (which are included with the Deferred Compensation Obligation in the tables above) are based on a known and certain stream of payments to be made over time and are categorized as Level 2 within the fair value hierarchy.

New Accounting Standards (All R

New Accounting Standards (All Registrants)	3 Months Ended
	Mar. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Description of New Accounting Pronouncements Not yet Adopted [Text Block]	New Accounting Standards (All Registrants) New Accounting Standards Issued and Not Yet Adopted: The following new authoritative accounting guidance issued by the FASB has not yet been adopted and reflected by the Registrants in their consolidated financial statements. Unless otherwise indicated, the Registrants are currently assessing the impacts such guidance may have (which could be material) on their Consolidated Balance Sheets, Consolidated Statements of Operations and Comprehensive Income, Consolidated Statements of Cash Flows and disclosures, as well as the potential to early adopt where applicable. The Registrants have assessed other FASB issuances of new standards which are not listed below given the current expectation such standards will not significantly impact the Registrants' financial reporting. Revenue from Contracts with Customers (Issued May 2014 and subsequently amended to address implementation questions): Changes the criteria for recognizing revenue from a contract with a customer. The new revenue recognition guidance, including subsequent amendments, is effective for annual reporting periods beginning on or after December 15, 2017, with the option to early adopt the standard for annual periods beginning on or after December 15, 2016. The Registrants do not plan to early adopt the standard. The new standard replaces existing guidance on revenue recognition, including most industry specific guidance, with a five step model for recognizing and measuring revenue from contracts with customers. The objective of the new standard is to provide a single, comprehensive revenue recognition model for all contracts with customers to improve comparability within industries, across industries, and across capital markets. The underlying principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The guidance also requires a number of disclosures regarding the nature, amount, timing, and uncertainty of revenue and the related cash flows. In addition, the Registrants will be required to capitalize costs to acquire new contracts, and amortize such costs in a manner consistent with the transfer to the customer of the associated goods or services. Exelon currently expenses those costs as incurred. The guidance can be applied retrospectively to each prior reporting period presented (full retrospective method) or retrospectively with a cumulative effect adjustment to retained earnings for initial application of the guidance at the date of initial adoption (modified retrospective method). The Registrants continue to assess the impacts this guidance may have on their Consolidated Balance Sheets, Consolidated Statements of Operations and Comprehensive Income, Consolidated Statements of Cash Flows and disclosures. In performing this assessment, the Registrants have utilized a project implementation team comprised of both internal and external resources to conduct the following key activities: • Actively participate in the AICPA Power and Utilities Industry Task Force (Industry Task Force) process to identify implementation issues and support the development of related implementation guidance; • Evaluate existing contracts and revenue streams for potential changes in the amounts and timing of recognizing revenues under the new guidance; • Evaluate and select the transition method; and • Develop and implement the approach and process for complying with the new revenue recognition disclosure requirements. While there continues to be some ongoing activities in all of these areas, the Registrants have substantially completed the evaluation of their collective contracts and revenue streams, as well as the evaluation of the transition method. Based on the work completed thus far, the Registrants have reached the following preliminary conclusions: • The Registrants expect to apply the new guidance using the full retrospective method, however this conclusion could change based on the outcome of open implementation issues discussed below; • The Registrants currently anticipate that the implementation of the new guidance will not have a material impact on the amount and timing of revenue recognition; and • The new guidance will result in more detailed disclosures of revenue compared to current guidance. Notwithstanding the preliminary conclusions noted above, certain implementation issues continue to be debated and worked through the Industry Task Force process that could result in amendments to the standard or implementation guidance that could have a material impact on the Registrants’ Consolidated Balance Sheets, Consolidated Statements of Operations and Comprehensive Income, Consolidated Statements of Cash Flows and disclosures. The contributions in aid of construction (CIAC) implementation issue previously disclosed has been resolved, subject to the completion of the public comment period, with the conclusion that CIAC is outside of the scope of ASC 606 and, therefore, the accounting by the Utility Registrants for CIAC will not change as a result of ASC 606. The open implementation issues that could be most impactful to the Registrants include: (1) the ability of the Utility Registrants to recognize revenue for certain contracts where collectability is in question and (2) primarily at Generation, bundled sales contracts and contracts with pricing provisions that may require recognition of revenue at prices other than the contract price (e.g., straight line or estimated future market prices). As part of the overall implementation project, the Registrants have developed alternative adoption plans that would be implemented in the event the ultimate resolution of the open implementation issues result in significant changes from current revenue recognition practices. Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost (Issued March 2017): The new standard will require significant changes to the accounting and presentation of pension and OPEB costs at the plan sponsor (i.e., Exelon) level. This guidance requires plan sponsors to separate net periodic pension cost and net periodic OPEB cost (together, net benefit cost) into the service cost component and other components; service cost will be presented as part of income from operations and the other components will be classified outside of income from operations on the Consolidated Statements of Operations and Comprehensive Income. Additionally, service cost is the only component eligible for capitalization (whereas under current GAAP, all components of net benefit cost are classified as compensation cost and are eligible for capitalization). Exelon is currently evaluating the impact of this standard, including coordinating with its industry group and advisors. Generation, ComEd, PECO, BGE, BSC, PHI, Pepco, DPL, ACE and PHISCO participate in Exelon’s single employer plan and apply multi-employer accounting. Exelon is currently evaluating how the new standard will impact accounting and financial reporting for these registrants. The standard will be effective January 1, 2018 and requires retrospective adoption for the presentation of the service cost component and the other components of net benefit cost and prospective adoption for the capitalization of only the service cost component of net benefit cost. Exelon will not early adopt this standard. Leases (Issued February 2016): Increases transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. The guidance requires lessees to recognize both the right-of-use assets and lease liabilities in the balance sheet for most leases, whereas today only financing type lease liabilities (capital leases) are recognized in the balance sheet. This is expected to require significant changes to systems, processes and procedures in order to recognize and measure leases recorded on the balance sheet that are currently classified as operating leases. In addition, the definition of a lease has been revised in regards to when an arrangement conveys the right to control the use of the identified asset under the arrangement which may result in changes to the classification of an arrangement as a lease. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee have not significantly changed from current GAAP. The accounting applied by a lessor is largely unchanged from that applied under current GAAP. The standard is effective for fiscal years beginning after December 15, 2018. Early adoption is permitted, however the Registrants do not expect to early adopt the standard. Lessees and lessors are required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. Refer to Note 24 — Commitments and Contingencies of the Combined Notes to the Consolidated Financial Statements in the Exelon 2016 Form 10-K for additional information regarding operating leases. Impairment of Financial Instruments (Issued June 2016): Provides for a new Current Expected Credit Loss (CECL) impairment model for specified financial instruments including loans, trade receivables, debt securities classified as held-to-maturity investments and net investments in leases recognized by a lessor. Under the new guidance, on initial recognition and at each reporting period, an entity is required to recognize an allowance that reflects the entity’s current estimate of credit losses expected to be incurred over the life of the financial instrument. The standard does not make changes to the existing impairment models for non-financial assets such as fixed assets, intangibles and goodwill. The standard will be effective January 1, 2020 and, for most debt instruments, requires a modified retrospective transition approach through a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. Goodwill Impairment (issued January 2017): Simplifies the accounting for goodwill impairment by removing Step 2 of the current test, which requires calculation of a hypothetical purchase price allocation. Under the revised guidance, goodwill impairment will be measured as the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill (currently Step 1 of the two step impairment test). Entities will continue to have the option to perform a qualitative assessment to determine if a quantitative impairment test is necessary. Exelon, Generation, ComEd, PHI, and DPL have goodwill as of March 31, 2017. This updated guidance is not currently expected to impact the Registrants’ financial reporting. The standard is effective January 1, 2020, with early adoption permitted, and must be adopted on a prospective basis. Clarifying the Definition of a Business (issued January 2017): Clarifies the definition of a business with the objective of addressing whether acquisitions should be accounted for as acquisitions of assets or as acquisitions of businesses. If substantially all the fair value of the assets acquired is concentrated in a single identifiable asset or a group of similar identifiable assets, the set of transferred assets and activities is not a business. If the fair value of the assets acquired is not concentrated in a single identifiable asset or a group of similar identifiable assets, then an entity must evaluate whether an input and a substantive process exist, which together significantly contribute to the ability to produce outputs. The standard also revises the definition of outputs to focus on goods and services to customers. The standard could result in more acquisitions being accounted for as asset acquisitions. The standard will be effective January 1, 2018 and will be applied prospectively. Intra-Entity Transfers of Assets Other Than Inventory (Issued October 2016): Requires entities to recognize the income tax consequences of an intra-entity transfer of an asset other than inventory when the transfer occurs (compared to current GAAP which prohibits the recognition of current and deferred income taxes for an intra-entity asset transfer until the asset has been sold to an outside party). The standard is effective for fiscal years beginning after December 15, 2017 with early adoption permitted. The guidance is required to be applied on a modified retrospective basis through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments (Issued August 2016) and Restricted Cash (Issued November 2016): In 2016, the FASB issued two standards impacting the Statement of Cash Flows. The first adds or clarifies guidance on the classification of certain cash receipts and payments on the statement of cash flows as follows: debt prepayment or extinguishment costs, settlement of zero-coupon bonds, contingent consideration payments made after a business combination, proceeds from the settlement of insurance claims, proceeds from the settlement of corporate-owned life insurance policies and bank-owned life insurance policies, distributions received from equity method investees, beneficial interest in securitization transactions, and the application of the predominance principle to separately identifiable cash flows. The second states that amounts generally described as restricted cash and restricted cash equivalents should be included with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows (instead of being presented as cash flow activities). Exelon will adopt both standards on January 1, 2018 on a retrospective basis. Adoption of the second standard will result in a change in presentation of restricted cash on the face of the Statement of Cash Flows; otherwise the Registrants expect that adoption of the guidance will have insignificant impacts on the Registrants’ Consolidated Statements of Cash Flows and disclosures. Recognition and Measurement of Financial Assets and Financial Liabilities (Issued January 2016): (i) Requires all investments in equity securities, including other ownership interests such as partnerships, unincorporated joint ventures and limited liability companies, to be carried at fair value through net income, (ii) requires an incremental recognition and disclosure requirement related to the presentation of fair value changes of financial liabilities for which the fair value option has been elected, (iii) amends several disclosure requirements, including the methods and significant assumptions used to estimate fair value or a description of the changes in the methods and assumptions used to estimate fair value, and (iv) requires disclosure of the fair value of financial assets and liabilities measured at amortized cost at the amount that would be received to sell the asset or paid to transfer the liability. The standard is effective for fiscal years beginning after December 15, 2017 with early adoption permitted. The guidance is required to be applied retrospectively with a cumulative effect adjustment to retained earnings for initial application of the guidance at the date of adoption (modified retrospective method).

Variable Interest Entities (All

Variable Interest Entities (All Registrants)	3 Months Ended
	Mar. 31, 2017
Variable Interest Entity [Abstract]
Variable Interest Entity Disclosure (All Registrants)	3 . 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 March 31, 2017 and 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 ( see Consolidated Variable Interest Entities below) . As of March 31, 2017 and December 31, 2016 , Exelon and Generation collectively had significant interests in seven and eight , respectively, 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 Exelon's, Generation's, BGE's, PHI's and ACE's consolidated VIEs consist of: • A retail gas group formed by Generation to enter into a collateralized gas supply agreement with a third-party gas supplier, • a group of solar project limited liability companies formed by Generation to build, own and operate solar power facilities, • several wind project companies designed by Generation to develop, construct and operate wind generation facilities, • a group of companies formed by Generation to build, own and operate other generating facilities, • certain retail power and gas companies for which Generation is the sole supplier of energy, • CENG, • 2015 ESA Investco, LLC, a company that holds an equity method investment in a distributed energy company, • BondCo, a special purpose bankruptcy remote limited liability company formed by BGE to acquire, hold, issue and service bonds secured by rate stabilization property, and • ATF , 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. As of March 31, 2017 and December 31, 2016 , ComEd, PECO, Pepco and DPL did not have any material consolidated VIEs. As of March 31, 2017 and December 31, 2016 , Exelon, Generation, BGE, PHI and ACE provided the following support to their respective consolidated VIEs: • Generation provides operating and capital funding to the solar and wind entities for ongoing construction, operations and maintenance of the solar and wind power facilities and there is limited recourse to Generation related to certain solar and wind entities. • Generation provides approximately $27 million in credit support for the retail power and gas companies for which Generation is the sole supplier of energy. • Generation provides a $75 million parental guarantee to a third-party gas supplier and provides limited recourse to other third-party gas suppliers and customers in support of its retail gas group. • Generation provides operating and capital funding to the other generating facilities for ongoing construction, operations and maintenance and provides a parental guarantee of up to $275 million in support of the payment obligations related to the Engineering, Procurement and Construction contract in support of one of its other generating facilities. • 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 of the Exelon 2016 Form 10-K 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 5 — Regulatory Matters for additional details), • Generation provided a $400 million loan to CENG. As of March 31, 2017 , the remaining obligation is $320 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 17 — Commitments and Contingencies for more details), • 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 $8 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 17 — 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. • In the case of BondCo, BGE is required to remit all payments it receives from all residential customers through non-bypassable, rate stabilization charges to BondCo. During the three months ended March 31, 2017 and 2016 , BGE remitted $19 million and $20 million to BondCo, respectively. • In the case of ATF, 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 months ended March 31, 2017 and 2016 , ACE transferred $19 million and $14 million to ATF, respectively. 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. The carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in the Registrants' consolidated financial statements at March 31, 2017 and December 31, 2016 are as follows: March 31, 2017 December 31, 2016 Successor Successor Exelon (a) Generation BGE PHI (a) ACE Exelon (a)(b) Generation BGE PHI (a) ACE Current assets $ 1,018 $ 965 $ 42 $ 11 $ 7 $ 954 $ 916 $ 23 $ 14 $ 9 Noncurrent assets 8,891 8,855 3 33 23 8,563 8,525 3 35 23 Total assets $ 9,909 $ 9,820 $ 45 $ 44 $ 30 $ 9,517 $ 9,441 $ 26 $ 49 $ 32 Current liabilities $ 871 $ 791 $ 42 38 $ 34 $ 885 $ 802 $ 42 $ 42 $ 37 Noncurrent liabilities 2,745 2,654 — 91 81 2,713 2,612 — 101 89 Total liabilities $ 3,616 $ 3,445 $ 42 $ 129 $ 115 $ 3,598 $ 3,414 $ 42 $ 143 $ 126 _______ (a) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. (b) Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity. 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 March 31, 2017 and December 31, 2016 , these assets and liabilities primarily consisted of the following: March 31, 2017 December 31, 2016 Successor Successor Exelon (a) Generation BGE PHI (a) ACE Exelon (a)(b) Generation BGE PHI (a) ACE Cash and cash equivalents $ 199 $ 199 $ — $ — $ — $ 150 $ 150 $ — $ — $ — Restricted cash 124 75 42 7 7 59 27 23 9 9 Accounts receivable, net Customer 347 347 — — — 371 371 — — — Other 23 23 — — — 48 48 — — — Mark-to-market derivatives assets 41 41 — — — 31 31 — — — Inventory Materials and supplies 191 191 — — — 199 199 — — — Other current assets 58 54 — 4 — 50 44 — 5 — Total current assets 983 930 42 11 7 908 870 23 14 9 Property, plant and equipment, net 5,425 5,425 — — — 5,415 5,415 — — — Nuclear decommissioning trust funds 2,286 2,286 — — — 2,185 2,185 — — — Goodwill 47 47 — — — 47 47 — — — Mark-to-market derivatives assets 57 57 — — — 23 23 — — — Other noncurrent assets 350 314 3 33 23 315 277 3 35 23 Total noncurrent assets 8,165 8,129 3 33 23 7,985 7,947 3 35 23 Total assets $ 9,148 $ 9,059 $ 45 $ 44 $ 30 $ 8,893 $ 8,817 $ 26 $ 49 $ 32 Long-term debt due within one year $ 237 $ 159 $ 41 $ 37 $ 33 $ 181 $ 99 $ 41 $ 40 $ 35 Accounts payable 275 275 — — — 269 269 — — — Accrued expenses 85 83 1 1 1 119 116 1 2 2 Mark-to-market derivative liabilities 18 18 — — — 60 60 — — — Unamortized energy contract liabilities 16 16 — — — 15 15 — — — Other current liabilities 11 11 — — — 30 30 — — — Total current liabilities 642 562 42 38 34 674 589 42 42 37 Long-term debt 626 535 — 91 81 641 540 — 101 89 Asset retirement obligations 1,929 1,929 — — — 1,904 1,904 — — — Pension obligation (c) 8 8 — — — 9 9 — — — Unamortized energy contract liabilities 18 18 — — — 22 22 — — — Other noncurrent liabilities 122 122 — — — 106 106 — — — Total noncurrent liabilities 2,703 2,612 — 91 81 2,682 2,581 — 101 89 Total liabilities $ 3,345 $ 3,174 $ 42 $ 129 $ 115 $ 3,356 $ 3,170 $ 42 $ 143 $ 126 _______ (a) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. (b) Includes certain purchase accounting adjustments not pushed down to the BGE 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 Consolidated Balance Sheets. See Note 13 - 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. The Registrants’ unconsolidated VIEs consist of: • Energy purchase and sale agreements with VIEs for which Generation has concluded that consolidation is not required. • Asset sale agreement with ZionSolutions, LLC and EnergySolutions, Inc. in which Generation has a variable interest but has concluded that consolidation is not required. • Equity investments in distributed energy companies and energy generating facilities for which Generation has concluded that consolidation is not required. As of March 31, 2017 and December 31, 2016 , Exelon and Generation had significant unconsolidated variable interests in seven and eight VIEs, respectively for which Exelon or Generation, as applicable, was not the primary beneficiary; including certain equity investments and certain commercial agreements. The decrease in the number of unconsolidated VIEs is due to the sale of an equity investment in an energy generating facility. 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 $16 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 $16 million included in Investments on Exelon’s and Generation’s Consolidated Balance Sheets . The risk of a loss was assessed to be remote and, accordingly, Exelon and Generation have not recognized a liability associated with any portion of the maximum exposure to loss. 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 a distributed energy company, which is an unconsolidated VIE. 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 contributed a total of $227 million of equity incrementally from inception through the first quarter of 2017 in proportion of their ownership interests. Generation and the tax equity investor provided 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. As all equity contributions were made as of March 31, 2017 , there is no further payment obligation under the parental guarantee. The following tables present summary information about Exelon and Generation’s significant unconsolidated VIE entities: March 31, 2017 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 647 $ 541 $ 1,188 Total liabilities (a) 73 230 303 Exelon's ownership interest in VIE (a) — 276 276 Other ownership interests in VIE (a) 574 36 610 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 279 279 Contract intangible asset 9 — 9 Debt and payment guarantees — — — Net assets pledged for Zion Station decommissioning (b) 7 — 7 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 _______ (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 $95 million and $113 million as of March 31, 2017 and December 31, 2016 , respectively; offset by payables to ZionSolutions LLC of $88 million and $104 million as of March 31, 2017 and December 31, 2016 , respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE. For each of the unconsolidated VIEs, Exelon and Generation has 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 material agreements with, or commitments by, third parties that would affect the fair value or risk of their variable interests in these VIEs.

Mergers, Acquisitions, and Disp

Mergers, Acquisitions, and Dispositions	3 Months Ended
	Mar. 31, 2017
Business Combinations [Abstract]
Mergers, Acquisitions and Dispositions	Mergers, Acquisitions and Dispositions (Exelon, Generation and PHI) Acquisition of James A. FitzPatrick Nuclear Generating Station (Exelon and Generation) On March 31, 2017, Generation acquired the 838 MW single-unit James A. FitzPatrick (FitzPatrick) nuclear generating station located in Scriba, New York from Entergy Nuclear FitzPatrick LLC (Entergy) for a total purchase price of $293 million , which consisted of a cash purchase price of $110 million and a net cost reimbursement to and on behalf of Entergy of $183 million . As part of the acquisition agreements, Generation provided nuclear fuel and reimbursed Entergy for incremental costs to prepare for and conduct a plant refueling outage; and Generation reimbursed Entergy for incremental costs to operate and maintain the plant for the period after the refueling outage through the acquisition closing date. These reimbursements covered costs that Entergy otherwise would have avoided had it shut down the plant as originally intended in January 2017. The amounts reimbursed by Generation were offset by FitzPatrick's electricity and capacity sales revenues for this same post-outage period. As part of the transaction, Generation received the FitzPatrick NDT fund assets and assumed the obligation to decommission FitzPatrick. The NRC license for FitzPatrick expires in 2034. As of March 31, 2017 , Generation had remitted purchase price consideration of $302 million (including $248 million of cash and $54 million of nuclear fuel) to and on behalf of Entergy and has $9 million included in Accounts receivable, net - Other on Exelon’s and Generation’s Consolidated Balance Sheets, to be received during the second quarter of 2017. The following table summarizes the acquisition-date fair value of the consideration transferred and the assets and liabilities assumed for the FitzPatrick acquisition by Generation as of March 31, 2017 : Cash paid for purchase price $ 110 Cash paid for net cost reimbursement 129 Nuclear fuel transfer 54 Total consideration transferred $ 293 Identifiable assets acquired and liabilities assumed Current assets $ 58 Property, plant and equipment 278 Nuclear decommissioning trust funds 807 Other assets (a) 114 Total assets $ 1,257 Current liabilities $ 7 Asset retirement obligations 417 Pension and OPEB obligations 49 Deferred income taxes 144 Spent nuclear fuel obligation 110 Other liabilities 11 Total liabilities $ 738 Total net identifiable assets, at fair value $ 519 Bargain purchase gain (after-tax) $ 226 _____________ (a) Includes a $110 million asset associated with a contractual right to reimbursement from the New York Power Authority (NYPA), a prior owner of FitzPatrick, associated with the DOE one-time fee obligation. See Note 24 - Commitments and Contingencies of the Exelon 2016 Form 10- K for additional background regarding SNF obligations to the DOE. The after-tax bargain purchase gain of $226 million is included within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income and reflects differences in strategies between Generation and Entergy for the intended use and ultimate decommissioning of the plant. The fair values of FitzPatrick’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 and future power and fuel market prices. The valuations performed to assess the fair value of certain assets acquired and liabilities assumed are preliminary. Accounting guidance provides that the allocation of the purchase price may be modified up to one year from the date of the acquisition to the extent that additional information is obtained about the facts and circumstances that existed as of the acquisition date; however, Generation expects to finalize these amounts by the end of 2017. The significant assets and liabilities for which preliminary valuation amounts are recognized at March 31, 2017 include the fair value of the decommissioning ARO, pension and OPEB obligations and related deferred tax liabilities. Any changes to the fair value assessments may materially impact the purchase price allocation and the amount of the recorded bargain purchase gain. For the three months ended March 31, 2017 , Exelon and Generation incurred $32 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. 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 amount, excluding renewable generation commitments and charitable contributions). These filings reflect agreements reached with certain parties to the merger proceedings in these jurisdictions. In 2016, the DPSC and NJBPU approved the amounts and allocations of the additional merger benefits for Delaware and New Jersey, respectively. On April 12, 2017, the MDPSC issued an order approving the amounts of the additional merger benefits for Maryland, but amending the proposed allocations of the benefits. The amended allocations do not have a material effect on any of the Registrants' financial statements. No changes in commitment cost levels are required in the District of Columbia. The following amounts represent total commitment costs for Exelon, PHI, Pepco, DPL and ACE that have been recorded since the acquisition date: Expected Payment Period Successor Description Pepco DPL ACE PHI Exelon Rate credits 2016 - 2017 $ 91 $ 66 $ 101 $ 258 $ 258 Energy efficiency 2016 - 2021 — — — — 122 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 — — — — 17 Other 7 7 — 14 30 Total $ 126 $ 85 $ 111 $ 322 $ 513 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 approximately 37 MWs of new generation in Maryland, District of Columbia, and Delaware, 27 MWs of which are expected 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. 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. The Circuit Court 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, 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 each filed petitions seeking further review in the Court of Appeals of Maryland. Exelon, along with Prince George's County and Montgomery County have filed answers opposing those petitions, which Exelon believes are without merit. 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 parties have filed briefs and the Court scheduled oral argument for May 2. A decision on this matter 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 preliminary valuations performed in the first quarter of 2016 were updated in the second, third, and fourth quarters of 2016. There were no adjustments to the purchase price allocation in the first quarter of 2017 and the purchase price allocation is now final. 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: Purchase Price Allocation (a) 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 obligations 821 Other liabilities 187 Total liabilities $ 14,655 Total purchase price $ 7,142 _____________ (a) Amounts shown reflect the final purchase price allocation and the correction of a reporting error identified and corrected in the second quarter of 2016. The error had resulted in a gross up of certain assets and liabilities related to legacy PHI intercompany and income tax receivable and payable balances. 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 expected to be 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 5 - 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 March 31, 2017 . 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 $1.2 billion and Net income of $140 million during the three months ended March 31, 2017 , and Operating revenues of $107 million and Net loss of $(315) million during the three months ended March 31, 2016 . For the three months ended March 31, 2017 and 2016 , the Registrants have recognized costs to achieve the PHI acquisition as follows: Three Months Ended March 31, Acquisition, Integration and Financing Costs (a) 2017 2016 Exelon (b) $ 9 $ 102 Generation 9 16 ComEd (c) — (8 ) PECO 1 2 BGE 2 2 Pepco 1 27 DPL (d) (7 ) 16 ACE 1 13 Successor Predecessor Acquisition, Integration and Financing Costs (a) Three Months Ended March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 PHI (d) $ (5 ) $ 56 $ 29 ______________ (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 three months ended March 31, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $9 million , incurred at ComEd that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. (d) For the three months ended March 31, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million , incurred at DPL that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — 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. Three Months Ended Year Ended December 31, 2016 (a) 2016 (b) Total operating revenues $ 8,556 $ 32,342 Net income attributable to common shareholders 577 1,562 Basic earnings per share $ 0.63 $ 1.69 Diluted earnings per share 0.62 1.69 ______________ (a) The amounts above include adjustments for non-recurring costs directly related to the merger of $639 million and intercompany revenue of $170 million for the three months ended March 31, 2016 . (b) The amounts above include adjustments for non-recurring costs directly related to the merger of $680 million and intercompany revenue of $171 million for the year ended December 31, 2016 .

Regulatory Matters (All Registr

Regulatory Matters (All Registrants)	3 Months Ended
	Mar. 31, 2017
Regulated Operations [Abstract]
Regulatory Matters (All Registrants)	5 . Regulatory Matters (All Registrants) Except for the matters noted below, the disclosures set forth in Note 3 - Regulatory Matters of the Exelon 2016 Form 10-K reflect, in all material respects, the current status of regulatory and legislative proceedings of the Registrants. The following is an update to that discussion. Illinois Regulatory Matters Distribution Formula Rate (Exelon and ComEd). On April 13, 2017, ComEd filed its annual distribution formula rate with the ICC pursuant to EIMA. The filing establishes the revenue requirement used to set the rates that will take effect in January 2018 after the ICC’s review and approval, which is due by December 2017. The revenue requirement requested is based on 2016 actual costs plus projected 2017 capital additions as well as an annual reconciliation of the revenue requirement in effect in 2016 to the actual costs incurred that year. ComEd's 2017 filing request includes a total increase to the revenue requirement of $ 96 million , reflecting an increase of $ 78 million for the initial revenue requirement for 2017 and an increase of $ 18 million related to the annual reconciliation for 2016. The revenue requirement for 2017 provides for a weighted average debt and equity return on distribution rate base of 6.47% inclusive of an allowed ROE of 8.40% , reflecting the average rate on 30 -year treasury notes plus 580 basis points. The annual reconciliation for 2016 provided for a weighted average debt and equity return on distribution rate base of 6.45% inclusive of an allowed ROE of 8.34% , reflecting the average rate on 30 -year treasury notes plus 580 basis points less a performance metrics penalty of 6 basis points. See table below for ComEd's regulatory assets associated with its distribution formula rate. For additional information on ComEd's distribution formula rate filings see Note 3 — Regulatory Matters of the Exelon 2016 Form 10-K. On December 6, 2016, the ICC issued a final order approving the 2016 distribution formula rate, which included a total increase to the revenue requirement of $ 127 million , reflecting an increase of $ 134 million for the initial revenue requirement for 2016 and a decrease of $7 million related to the annual reconciliation for 2015. 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. On March 22, 2017, the ICC issued an order approving ComEd's proposal to reduce the 2016 revenue requirement by $ 18 million , which will be reflected in customer rates in 2017. 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 IPA 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. Illinois 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. On February 14, 2017, two lawsuits were filed in the Northern District of Illinois against the IPA alleging that the state’s ZEC program violates certain provisions of the U.S. Constitution. One lawsuit was filed by customers of ComEd, led by the Village of Old Mill Creek, and the other was brought by the EPSA and three other electric suppliers. Both lawsuits argue that the Illinois ZEC program will distort FERC’s energy and capacity market auction system of setting wholesale prices, and seek a permanent injunction preventing the implementation of the program. Exelon intervened and filed motions to dismiss in both lawsuits. These motions are currently pending. In addition, on March 31, 2017, plaintiffs in both lawsuits filed motions for preliminary injunction with the court. Exelon cannot predict the outcome of these lawsuits. It is possible that resolution of these matters could have a material, unfavorable impact on Exelon’s and Generation’s results of operations, financial positions and cash flows. See Note 7 - 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. These provisions do not impact ComEd’s Consolidated Balance Sheets, Consolidated Statements of Operations and Comprehensive Income or Consolidated Statements of Cash Flows until second quarter of 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 beginning with the reconciliation filed in 2018 for the 2017 calendar year. Elimination of the ROE collar effectively offsets the favorable or unfavorable impacts to Operating revenues associated with variations in delivery volumes associated with above or below normal weather, numbers of customers or usage per customer. ComEd began reflecting the impacts of this change in its electric distribution services costs regulatory asset beginning in first quarter 2017. As of March 31, 2017, ComEd recorded an increase to Operating revenues and its electric distribution services costs regulatory asset of approximately $16 million for this change. 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 after FEJA becomes effective on June 1, 2017, 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 March 31, 2017 , ComEd’s over-recoveries associated with its existing energy efficiency rider of $139 million were reflected in Current regulatory liabilities on Exelon’s and ComEd’s Consolidated Balance Sheets. ComEd expects to provide a one-time credit to customers in the second half of 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 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. Other than recognizing the impacts of eliminating the ROE collar in its electric distribution formula rate, FEJA did not have any impacts on ComEd’s Consolidated Balance Sheets, Consolidated Statements of Operations and Comprehensive Income or Consolidated Statements of Cash Flows in first quarter 2017. 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 March 31, 2017 , 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. ComEd acquired the necessary land rights across the project route through voluntary transactions. ComEd began construction of the line during 2015 and placed the line in-service on April 7, 2017. Pennsylvania Regulatory Matters Pennsylvania Procurement Proceedings (Exelon and PECO). Through PECO’s PAPUC approved DSP Programs, PECO procures electric supply for its default electric customers through PAPUC approved competitive procurements. 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 December 8, 2016, the PAPUC approved the fourth DSP Program for the modified 48-month term and deferred CAP Shopping to another proceeding. OCA and Low Income Advocates subsequently filed a Petition for Reconsideration and Clarification related to CAP Shopping. On March 16, 2017 the PAPUC granted reconsideration and consolidated the proceeding with the DSP II docket, which includes the pending CAP Shopping plan that would allow low-income CAP customers to purchase their generation supply from EGSs. PAPUC referred the consolidated proceedings to the Office of Administrative Law Judge for hearing and decision. Pennsylvania Act 11 of 2012 (Exelon and PECO). In February 2012, Act 11 was signed into law, which provided the PAPUC authority to approve the implementation of a distribution system improvement charge (DSIC) in rates designed to recover capital project costs incurred to repair, improve or replace utilities’ aging electric and natural gas distribution systems in Pennsylvania. Prior to recovering costs pursuant to a DSIC, the PAPUC's implementation order requires a utility to have a Long Term Infrastructure Improvement Plan (LTIIP) approved by the Commission, which outlines how the utility is planning to increase its investment for repairing, improving or replacing aging infrastructure. The PAPUC approved PECO’s petition for its proposed electric DSIC and LTIIP on October 22, 2015 for spending of $275 million over a 5 year period through 2020. On March 1, 2017, PECO filed a petition with the PAPUC for approval of a Modified Gas LTIIP to increase expenditures to $762 million from the approved $534 million over the 10 year LTIIP period through 2022. Maryland Regulatory Matters 2017 Maryland Electric Distribution Rates (Exelon, PHI and Pepco). On March 24, 2017, Pepco filed an application with the MDPSC requesting an increase of $69 million based on a ROE of 10.1% . The application includes a request for an income tax adjustment to reflect full normalization of removal costs associated with pre-1981 property, which accounts for $18 million of the requested increase. Pepco expects a decision in the matter in the fourth quarter of 2017, but cannot predict how much of the requested rate increase the MDPSC will approve or if it will approve the requested income tax adjustment. 2016 Maryland Electric Distribution Rates (Exelon, PHI and DPL). On February 15, 2017, the MDPSC approved an increase in DPL electric distribution rates of $38 million based on a ROE of 9.6% . The new rates became effective for services rendered on or after February 15, 2017. The MDPSC also denied DPL’s request to continue its Grid Resiliency Program, through which DPL proposed to invest $4.6 million a year for two years to improve priority feeders and install single-phase reclosing fuse technology. The final order did not result in the recognition of any incremental regulatory assets or liabilities during the first quarter of 2017. Cash Working Capital Order (Exelon and BGE). On November 17, 2016, the MDPSC rendered a decision in the proceeding to review BGE’s request to recover its cash working capital (CWC) requirement for its Provider of Last Resort service, also known as Standard Offer Service (SOS), as well as other components that make up the Administrative Charge, the mechanism that enables BGE to recover all of its SOS-related costs. The Administrative Charge is now comprised of five components: CWC, uncollectibles, incremental costs, return, and an administrative adjustment, which is an adder to the utility’s SOS rate to act as a proxy for retail suppliers’ costs. The Commission accepted BGE positions on recovery of CWC and pass-through recovery of BGE’s actual uncollectibles and incremental costs. The order also grants BGE a modest return on the SOS. The Commission ruled that the level of the administrative adjustment will be determined in BGE’s next rate case. On December 16, 2016, MDPSC Staff requested clarification concerning the amount of return on the SOS awarded to BGE and on December 19, 2016, the residential consumer advocate sought rehearing of the return awarded. On January 24, 2017, the MDPSC issued an order denying the MDPSC Staff request for clarification and the residential consumer advocate request for rehearing. On February 22, 2017, the residential consumer advocate filed an appeal of the MDPSC's orders with the Circuit Court for Baltimore City. BGE cannot predict the outcome of this appeal. Smart Meter and Smart Grid Investments (Exelon and BGE). In August 2010, the MDPSC approved a comprehensive smart grid initiative for BGE that included the planned installation of 2 million residential and commercial electric and natural gas smart meters at an expected total cost of $480 million of which $200 million was funded by SGIG. The MDPSC’s approval ordered BGE to defer the associated incremental costs, depreciation and amortization, and an appropriate return, in a regulatory asset until such time as a cost-effective advanced metering system is implemented. As of March 31, 2017 and December 31, 2016 , the balance of BGE's regulatory asset was $225 million and $230 million , respectively, representing incremental program deployment costs. The current quarter balance of $225 million consists of three major components, including $140 million of unamortized incremental deployment costs of the AMI program, $53 million of unamortized costs of the non-AMI meters replaced under the program, and $32 million related to post-test year incremental program deployment costs incurred prior to approval became effective June 2016. The balance as of March 31, 2017 reflects the impact of the cost disallowances and adjustments discussed below. The incremental deployment costs for the AMI program and the non-AMI meter components of the regulatory asset are being recovered through rates and amortized to expense over a 10 year period, while the post-test year incremental program deployment costs have not yet been approved for recovery by the MDPSC. A return on the regulatory asset is currently included in rates, except for the $53 million portion representing the unamortized cost of the retired non-AMI meters and a $32 million portion related to post-test year incremental program deployment costs. As a combined result of the MDPSC orders in BGE's 2015 electric and natural gas distribution rate case, BGE recorded a $52 million charge in June 2016 to Operating and maintenance expense in Exelon’s and BGE’s Consolidated Statements of Operations and Comprehensive Income reducing certain regulatory assets and other long-lived assets and reclassified $56 million of non-AMI plant costs from Property, plant and equipment, net to Regulatory assets on Exelon's and BGE's Consolidated Balance Sheets. For further information, see Note 3 - Regulatory Matters of the Exelon 2016 Form 10-K. Delaware Regulatory Matters Gas Cost Rates (Exelon, PHI and DPL). DPL makes an annual GCR filing with the DPSC for the purpose of allowing DPL to recover natural gas procurement costs through customer rates. In August 2016, DPL made its 2016-2017 GCR filing. The rates proposed in the 2016-2017 GCR filing resulted in a GCR increase of approximately 14% . On September 20, 2016, the DPSC issued an order allowing DPL to place the new rates into effect on November 1, 2016, subject to refund and pending final DPSC approval. A settlement agreement was reached by all parties. On April 20, 2017, the DPSC issued an order which approved the settlement agreement and made the rates approved as final effective November 1, 2016. 2016 Electric and Natural Gas Distribution Rates (Exelon, PHI and DPL). On May 17, 2016, DPL filed an application with the DPSC to increase its annual electric and natural gas distribution rates by $63 million (which was updated to $60 million on March 8, 2017) and $22 million , respectively, based on a requested ROE of 10.6% . While the DPSC is not required to issue a decision on the application within a specified period of time, Delaware law allowed DPL to put into effect $2.5 million of each of the rate increases two months after filing the applications which were effective July 16, 2016. On December 17, 2016, the DPSC approved that an additional $30 million in electric distribution rates be implemented effective December 17, 2016, subject to refund based on the final DPSC order, and an additional $10 million in natural gas distribution rates be implemented effective December 17, 2016, subject to refund based on the final DPSC order. On March 8, 2017, DPL entered into a settlement agreement with the Division of the Public Advocate, Delaware Electric Users Group and the DPSC Staff in its electric distribution rate proceeding, which provides for an increase in DPL electric distribution rates of $31.5 million based on an ROE of 9.7% . The settlement agreement also provides that the rates currently in effect, as approved by the DPSC, effective July 16, 2016 and December 17, 2016 (as discussed above), will remain in effect until the date of the final DPSC order and that no refund will be required. As a result, during the first quarter of 2017, DPL established a regulatory asset of $8 million for costs incurred to achieve the merger and reversed a regulatory liability of $1 million for electric revenues that are no longer subject to refund which resulted in an increase in net income of $5 million . DPL currently expects a final order on the settlement agreement during the second quarter of 2017. On April 6, 2017, DPL entered into a settlement agreement with the Division of the Public Advocate and the DPSC Staff in its natural gas distribution rate proceeding, which provides for an increase in DPL natural gas distribution rates of $4.9 million based on an ROE of 9.7% . The settlement agreement also provides that DPL will refund amounts in excess of the $4.9 million increase collected under the temporary rates effective July 16, 2016 and December 17, 2016 (as discussed above), and that the new rates will be effective within thirty days of DPSC approval of the settlement agreement. In the event that the final order reflects the settlement agreement, DPL does not expect the impact to be material to its financial statements. DPL currently expects a final order on the settlement agreement during the second quarter of 2017. District of Columbia Regulatory Matters 2016 Electric Distribution Rates (Exelon, PHI and Pepco). On June 30, 2016, Pepco filed an application with the DCPSC to increase its annual electric distribution rates by $86 million , which was updated to $82 million on October 14, 2016, and further updated to approximately $77 million on February 1, 2017, based on a requested ROE of 10.6% . The DCPSC has issued a procedural schedule indicating a final decision will be issued by July 25, 2017. Any adjustments to its rates approved by the DCPSC are expected to take effect soon thereafter. Pepco cannot predict how much of the requested increase the DCPSC will approve. On April 18, 2016, a party to a separate DCPSC proceeding filed a motion to suspend Pepco’s bill stabilization adjustment (BSA), which decouples distribution revenues from utility customers from the amount of electricity delivered. On September 9, 2016, the DCPSC denied the party’s motion and determined that the appropriate forum in which to determine whether the BSA continues to be just and reasonable is in Pepco’s rate case proceeding. In addition, the DCPSC stated that it was putting Pepco on notice that all funds collected for the BSA from January 2015 to the issuance of a decision in the rate case proceeding are subject to refund should the DCPSC determine that such funds were not justly or reasonably collected. On November 22, 2016, following Pepco's October 7, 2016 request for reconsideration of the order, the DCPSC issued an order stating that its September 9, 2016 order was not final and confirming that issues related to the BSA, including potential remedial actions, would be addressed in Pepco's rate case. Pepco cannot predict the outcome of this matter or the impact of a refund if ordered by the DCPSC. District of Colu

Impairment of Long-lived Assets

Impairment of Long-lived Assets (Exelon and Generation)	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Abstract]
Impairment of Long-Lived Assets (Exelon and Generation)	6 . Impairment of Long-Lived Assets (Exelon and Generation) Long-Lived Assets (Exelon and Generation) Generation evaluates long-lived assets for recoverability whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. 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 of the Exelon 2016 Form 10-K) 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 business by executing a forbearance agreement with the lenders of the nonrecourse debt. 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 - Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information. 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). 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 11 — Income Taxes for additional information.

Early Nuclear Plant Retirements

Early Nuclear Plant Retirements Early Nuclear Plant Retirements (Exelon, Generation)	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Abstract]
Implications Of Potential Early Retirement Disclosure [Text Block]	7 . 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 potential rules from the EPA requiring reduction of carbon and other emissions and the efforts of states to implement those final rules. In 2015 and 2016, Generation identified the Clinton, Quad Cities, Ginna, Nine Mile Point, and Three Mile Island (TMI) nuclear plants as having the greatest risk of early retirement based on economic valuation and other factors. PSEG has also recently made public similar financial challenges facing its New Jersey nuclear plants including Salem, of which Generation owns a 42.59% ownership interest. As previously disclosed, Exelon and Generation have committed to cease operation of the Oyster Creek nuclear plant by the end of 2019. Based on insufficient capacity auction results and the lack of progress on Illinois energy legislation, on June 2, 2016, Generation announced a decision to shut down the Clinton and Quad Cities nuclear plants on June 1, 2017 and June 1, 2018, respectively. With the passage of the Illinois ZES on December 7, 2016, and subject to prevailing over any related administrative or legal challenges, Generation reversed this decision and revised the expected economic useful lives for both facilities; 2027 for Clinton and 2032 for Quad Cities. Refer to Note 5 - Regulatory Matters for additional discussion on the Illinois ZES. Exelon's and Generation's 2016 results included a net incremental $714 million of total 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) Q2 2016 Q3 2016 Q4 2016 YTD 2016 Depreciation and amortization Accelerated depreciation (a) $ 115 $ 344 $ 253 $ 712 Accelerated Nuclear Fuel amortization 9 28 23 60 Operating and maintenance One time charges (b) 141 5 (120 ) 26 ARO accretion, net of contractual offset (c) — 2 — 2 Contractual offset for ARC depreciation (c) (14 ) (41 ) (31 ) (86 ) Total $ 251 $ 338 $ 125 $ 714 _____________ (a) Reflected incremental accelerated depreciation of plant assets, including any ARC, for the period June 2, 2016, through December 6, 2016. (b) Primarily included materials and supplies inventory reserve adjustments, employee related costs and construction work-in-progress (CWIP) impairments. (c) 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, Nine Mile Point, and Generation’s recently acquired FitzPatrick nuclear plant also faced 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, 2046 for Nine Mile Point Unit 2, and 2034 for FitzPatrick). On August 1, 2016, the NYPSC issued an order adopting the CES that, subject to prevailing over any administrative or legal challenges, would allow Ginna, Nine Mile Point, and FitzPatrick to continue to operate at least through the life of the program (March 31, 2029). The assumed useful life for depreciation purposes for each facility is through the end of their current operating licenses. Ginna most recently operated under an RSSA which expired March 31, 2017 and has filed the required notice with the NYPSC of its intent to continue operating beyond the expiry of the RSSA. Refer to Note 4 - Mergers, Acquisitions and Dispositions for additional information on Generation’s acquisition of FitzPatrick and Note 5 - 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 (and now including the newly acquired FitzPatrick) 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 TMI nuclear plant 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, the second consecutive year that TMI failed to clear the PJM base residual capacity auction. The plant is currently committed to operate through May 2019. TMI will be offered into the May 2017 PJM capacity auction for the 2020-2021 planning year, however the plant faces continued economic challenges and Exelon and Generation are exploring all options to return it to profitability, including the potential for a legislative solution in Pennsylvania similar to that passed in Illinois. The following table provides the balance sheet amounts as of March 31, 2017 for significant assets and liabilities associated with TMI, the plant 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 $ 40 Nuclear fuel inventory, net 72 Completed plant, net 1,000 Construction work in progress 40 Liability Balances Asset retirement obligation (572 ) 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.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities (All Registrants)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities (All Registrants)	8 . 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 March 31, 2017 and December 31, 2016 : Exelon March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 2,048 $ — $ 2,048 $ — $ 2,048 Long-term debt (including amounts due within one year) (a) 34,689 1,135 32,562 1,962 35,659 Long-term debt to financing trusts (b) 641 — — 677 677 SNF obligation 1,136 — 813 — 813 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 Generation March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 717 $ — $ 717 $ — $ 717 Long-term debt (including amounts due within one year) (a) 9,979 — 8,200 1,671 9,871 SNF obligation 1,136 — 813 — 813 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 ComEd March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 365 $ — $ 365 $ — $ 365 Long-term debt (including amounts due within one year) (a) 7,035 — 7,615 — 7,615 Long-term debt to financing trusts (b) 205 — — 218 218 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 PECO March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,580 $ — $ 2,806 $ — $ 2,806 Long-term debt to financing trusts 184 — — 193 193 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 BGE March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 95 $ — $ 95 $ — $ 95 Long-term debt (including amounts due within one year) (a) 2,323 — 2,501 — 2,501 Long-term debt to financing trusts (b) 252 — — 266 266 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 PHI (Successor) March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 167 $ — $ 167 $ — $ 167 Long-term debt (including amounts due within one year) (a) 5,860 — 5,510 291 5,801 December 31, 2016 Carrying Amount Fair Value 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 Pepco March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 167 $ — $ 167 $ — $ 167 Long-term debt (including amounts due within one year) (a) 2,350 — 2,804 9 2,813 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 DPL March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 1,326 $ — $ 1,374 $ — $ 1,374 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 ACE March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 1,145 $ — $ 989 $ 282 $ 1,271 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 ________ (a) Includes unamortized debt issuance costs which are not fair valued of $199 million , $67 million , $45 million , $15 million , $14 million , $2 million , $29 million , $11 million , and $5 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of March 31, 2017 . Includes unamortized debt issuance costs 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 . (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 March 31, 2017 and December 31, 2016 . 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 and Pepco'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 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 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. This amount also includes $110 million for the fair value of the one-time fee obligation associated with FitzPatrick as of March 31, 2017 . The fair value was determined using a similar methodology, however the New York Power Authority's (NYPA) discount rate is used in place of Generation's given the contractual right to reimbursement from NYPA for the obligation; see Note 4 - Mergers, Acquisitions and Dispositions for additional information on Generation's acquisition of FitzPatrick. 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. 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 material transfers between Level 1 and Level 2 during the three months ended March 31, 2017 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. 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 March 31, 2017 and December 31, 2016 : Generation Exelon As of March 31, 2017 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) $ 135 $ — $ — $ — $ 135 $ 342 $ — $ — $ — $ 342 NDT fund investments Cash equivalents (b) 160 21 — — 181 160 21 — — 181 Equities 4,113 505 1 2,089 6,708 4,113 505 1 2,089 6,708 Fixed income Corporate debt — 1,749 255 — 2,004 — 1,749 255 — 2,004 U.S. Treasury and agencies 1,516 35 — — 1,551 1,516 35 — — 1,551 Foreign governments — 57 — — 57 — 57 — — 57 State and municipal debt — 241 — — 241 — 241 — — 241 Other (c) — 52 — 484 536 — 52 — 484 536 Fixed income subtotal 1,516 2,134 255 484 4,389 1,516 2,134 255 484 4,389 Middle market lending — — 427 64 491 — — 427 64 491 Private equity — — — 158 158 — — — 158 158 Real estate — — — 427 427 — — — 427 427 NDT fund investments subtotal (d) 5,789 2,660 683 3,222 12,354 5,789 2,660 683 3,222 12,354 Pledged assets for Zion Station decommissioning Cash equivalents 21 — — — 21 21 — — — 21 Equities — 1 — — 1 — 1 — — 1 Fixed income - U.S. Treasury and agencies 8 1 — — 9 8 1 — — 9 Generation Exelon As of March 31, 2017 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Middle market lending — — 20 44 64 — — 20 44 64 Pledged assets for Zion Station (e) 29 2 20 44 95 29 2 20 44 95 Rabbi trust investments Cash equivalents 7 — — — 7 80 — — — 80 Mutual funds 20 — — — 20 53 — — — 53 Fixed income — — — — — — 15 — — 15 Life insurance contracts — 20 — — 20 — 66 20 — 86 Rabbi trust investments subtotal 27 20 — — 47 133 81 20 — 234 Commodity derivative assets Economic hedges 749 2,993 1,631 — 5,373 751 2,993 1,631 — 5,375 Proprietary trading 5 50 25 — 80 5 50 25 — 80 Effect of netting and allocation of collateral (f) (g) (639 ) (2,575 ) (873 ) — (4,087 ) (641 ) (2,575 ) (873 ) — (4,089 ) Commodity derivative assets subtotal 115 468 783 — 1,366 115 468 783 — 1,366 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 12 — — 12 Economic hedges — 22 — — 22 — 22 — — 22 Proprietary trading 3 1 — — 4 3 1 — — 4 Effect of netting and allocation of collateral (4 ) (14 ) — — (18 ) (4 ) (14 ) — — (18 ) Interest rate and foreign currency derivative assets subtotal (1 ) 9 — — 8 (1 ) 21 — — 20 Other investments — — 40 — 40 — — 40 — 40 Total assets 6,094 3,159 1,526 3,266 14,045 6,407 3,232 1,546 3,266 14,451 Liabilities Commodity derivative liabilities Economic hedges (787 ) (2,855 ) (1,167 ) — (4,809 ) (787 ) (2,855 ) (1,449 ) — (5,091 ) Proprietary trading (6 ) (49 ) (22 ) — (77 ) (6 ) (49 ) (22 ) — (77 ) Effect of netting and allocation of collateral (f) (g) 714 2,846 971 — 4,531 714 2,846 971 — 4,531 Commodity derivative liabilities subtotal (79 ) (58 ) (218 ) — (355 ) (79 ) (58 ) (500 ) — (637 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (1 ) — — (1 ) — (1 ) — — (1 ) Economic hedges — (25 ) — — (25 ) — (25 ) — — (25 ) Proprietary trading (3 ) — — — (3 ) (3 ) — — — (3 ) Effect of netting and allocation of collateral 4 14 — — 18 4 14 — — 18 Interest rate and foreign currency derivative liabilities subtotal 1 (12 ) — — (11 ) 1 (12 ) — — (11 ) Deferred compensation obligation — (35 ) — — (35 ) — (135 ) — — (135 ) Total liabilities (78 ) (105 ) (218 ) — (401 ) (78 ) (205 ) (500 ) — (783 ) Total net assets $ 6,016 $ 3,054 $ 1,308 $ 3,266 $ 13,644 $ 6,329 $ 3,027 $ 1,046 $ 3,266 $ 13,668 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 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) (g) (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 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 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) (g) 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 ________ (a) Generation excludes cash of $267 million and $252 million at March 31, 2017 and December 31, 2016 and restricted cash of $138 million and $157 million at March 31, 2017 and December 31, 2016 . Exelon excludes cash of $381 million and $360 million at March 31, 2017 and December 31, 2016 and restricted cash of $165 million and $180 million at March 31, 2017 and December 31, 2016 and includes long term restricted cash of $25 million at March 31, 2017 and December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) Includes less than $1 million and $29 million of cash received from outstanding repurchase agreements at March 31, 2017 and December 31, 2016 , respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (d) below. (c) Includes derivative instruments of $(1) million and $(2) million , which have a total notional amount of $886 million and $933 million at March 31, 2017 and December 31, 2016 , 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 assets (liabilities) of $8 million and $(31) million at March 31, 2017 and December 31, 2016 , 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 at March 31, 2017 and December 31, 2016 . These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (f) Collateral posted/(received) from counterparties totaled $75 million , $271 million and $98 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of March 31, 2017 . Collateral posted/(received) from counterparties, net of collateral paid to 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 . (g) Of the collateral posted/(received), $14 million represents variation margin on the exchanges as of March 31, 2017 . Of the collateral posted/(received), $(158) million represents variation margin on the exchanges as of December 31, 2016 . 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 March 31, 2017 and December 31, 2016 : ComEd PECO BGE As of March 31, 2017 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) $ — $ — $ — $ — $ 5 $ — $ — $ 5 $ 45 $ — $ — $ 45 Rabbi trust investments Mutual funds — — — — 7 — — 7 5 — — 5 Life insurance contracts — — — — — 10 — 10 — — — — Rabbi trust investments subtotal — — — — 7 10 — 17 5 — — 5 Total assets — — — — 12 10 — 22 50 — — 50 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (11 ) — (11 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (282 ) (282 ) — — — — — — — — Total liabilities — (8 ) (282 ) (290 ) — (11 ) — (11 ) — (4 ) — (4 ) Total net assets (liabilities) $ — $ (8 ) $ (282 ) $ (290 ) $ 12 $ (1 ) $ — $ 11 $ 50 $ (4 ) $ — $ 46 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 _________ (a) ComEd excludes cash of $31 million and $36 million at March 31, 2017 and December 31, 2016 and restricted cash of $3 million and $2 million at March 31, 2017 and December 31, 2016 . PECO excludes cash of $27 million and $22 million at March 31, 2017 and December 31, 2016 . BGE excludes cash of $11 million and $13 million at March 31, 2017 and December 31, 2016 and includes long term restricted cash of $2 million at March 31, 2017 and 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 $263 million , respectively, at March 31, 2017 , and $19 million and $239 million , respectively, at December 31, 2016 , 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 March 31, 2017 and December 31, 2016 : Successor Successor As of March 31, 2017 As of December 31, 2016 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 154 $ — $ — $ 154 $ 217 $ — $ — $ 217 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 74 — — 74 73 — — 73 Fixed income — 15 — 15 — 16 — 16 Life insurance contracts — 23 20 43 — 22 20 42 Rabbi trust investments subtotal 74 38 20 132 73 38 20 131 Total assets 228 38 20 286 290 38 20 348 Liabilities Deferred compensation obligation — (25 ) — (25 ) — (28 ) — (28 ) Total liabilities — (25 ) — (25 ) — (28 ) — (28 ) Total net assets $ 228 $ 13 $ 20 $ 261 $ 290 $ 10 $ 20 $ 320 Pepco DPL ACE As of March 31, 2017 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 $ 39 $ — $ — $ 39 $ 80 $ — $ — $ 80 Rabbi trust investments Cash equivalents 43 — — 43 1 — — 1 — — — — Fixed income — 15 — 15 — — — — — — — — Life insurance contracts — 23 20 43 — — — — — — — — Rabbi trust investments subtotal 43 38 20 101 1 — — 1 — — — — Total assets 76 38 20 134 40 — — 40 80 — — 80 Liabilities Deferred compensation obligation — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total liabilities — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 76 $ 34 $ 20 $ 130 $ 40 $ (1 ) $ — $ 39 $ 80 $ — $ — $ 80 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 _______ (a) PHI excludes cash of $19 million and $19 million at March 31, 2017 and December 31, 2016 and includes long term restricted cash of $23 million and $23 million at March 31, 2017 and December 31, 2016 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $8 million and $9 million at March 31, 2017 and December 31, 2016 . DPL excludes cash of $5 million and $4 million at March 31, 2017 and December 31, 2016 . ACE excludes cash of $4 million and $3 million at March 31, 2017 and December 31, 2016 and includes long term restricted cash of $23 million and $23 million at March 31, 2017 and December 31, 2016 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. The following tables present the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis during the three months ended March 31, 2017 and 2016 : Successor Generation ComEd PHI Exelon Three Months Ended March 31, 2017 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives (a) Life Insurance Contracts Eliminated in Consolidation Total Balance as of December 31, 2016 $ 677 $ 19 $ 493 $ 42 $ 1,231 $ (258 ) $ 20 $ — $ 993 Total realized / unrealized gains (losses) Included in net income 3 — (43 ) (b) 1 (39 ) — 1 — (38 ) Included in noncurrent payables to affiliates 9 — — — 9 — — (9 ) — Included in regulatory assets/liabilities — — — — — (24 ) — 9 (15 ) Change in collateral — — 38 — 38 — — — 38 Purchases, sales, issuances and settlements Purchases 17 1 69 2 89 — — — 89 Sales — — (2 ) — (2 ) — — — (2 ) Issuances — — — — — — (1 ) — (1 ) Settlements (23 ) — — — (23 ) — — — (23 ) Transfers into Level 3 — — (1 ) — (1 ) — — — (1 ) Transfers out of Level 3 — — 11 (5 ) 6 — — — 6 Balance as of March 31, 2017 $ 683 $ 20 $ 565 $ 40 $ 1,308 $ (282 ) $ 20 $ — $ 1,046 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2017 $ 2 $ — $ 59 $ — $ 61 $ — $ 1 $ — $ 62 ___________________ (a) Includes $ 30 million of decreases in fair value and an increase for realized losses due to settlements of $ 6 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 2017 . (b) Includes a reduction for the reclassification of $102 million of realized gains due to the settlement of derivative contracts for the three months ended March 31, 2017 . Successor Generation ComEd PHI (c) Exelon Three Months Ended March 31, 2016 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives (a) Life Insurance Contracts Eliminated in Consolidation Total Balance as of December 31, 2015 $ 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 2 — (6 ) (b) — (4 ) — — — (4 ) Included in noncurrent payables to affiliates 4 — — — 4 — — (4 ) — Included in payable for Zion Station decommissioning — 2 — — 2 — — — 2 Included in regulatory assets — — — — — (18 ) — 4 (14 ) Change in collateral — — (50 ) — (50 ) — — — (50 ) Purchases, sales, issuances and settlements Purchases 34 1 59 3 97 — — — 97 Sales — — (2 ) — (2 ) — — — (2 ) Settlements (26 ) — — — (26 ) — — — (26 ) Transfers into Level 3 — — 2 — 2 — — — 2 Transfers out of Level 3 — — (7 ) — (7 ) — — — (7 ) Balance as of March 31, 2016 $ 684 $ 25 $ 1,047 $ 36 $ 1,792 $ (265 ) $ 20 $ — $ 1,547 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2016 $ 1 $ — $ 219 $ — $ 220 $ — $ — $ — $ 220 _________ (a) Includes $25 million of decreases in fair value and an increase for realized losses due to settlements of $7 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 2016 . (b) Includes a reduction for the reclassification of $225 million of realized gains due to the settlement of derivative contracts recorded in results of operations for the three months ended March 31, 2016 . (c) Successor period represents activity from March 24, 2016 through March 31, 2016 . See tables below for PHI's predecessor periods, as well as activity for Pepco for the three months ended March 31, 2017 and 2016 . Predecessor January 1, 2016 to March 23, 2016 PHI Preferred Stock Life Insurance Contracts Beginning Balance $ 18 $ 19 Total realized / unrealized gains (losses) Included in net income (18 ) 1 Ending Balance $ — $ 20 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities for the period $ — $ 1 Life Insurance Contracts Three Months

Derivative Financial Instrument

Derivative Financial Instruments (All Registrants)	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments (All Registrants)	9 . 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 March 31, 2017 , the proportion of expected generation hedged for the major reportable segments is 97% - 100% , 60% - 63% and 30% - 33% 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 of the Exelon 2016 Form 10-K 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 5 — 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 1,850 GWhs and 1,220 GWhs for the three months ended March 31, 2017 and 2016 , respectively, 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 March 31, 2017 , Exelon had $800 million of notional amounts of fixed-to-floating hedges outstanding, and Exelon and Generation had $657 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 $2 million decrease in Exelon Consolidated pre-tax income for the three months ended March 31, 2017 . To manage foreign exchange rate exposure associated with international energy 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 March 31, 2017 : Generation Exelon Corporate Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary Trading (a) Collateral and Netting (b) Subtotal Derivatives Designated as Hedging Instruments Total Mark-to-market derivative assets (current assets) $ — $ 15 $ 3 $ (13 ) $ 5 $ — $ 5 Mark-to-market derivative assets (noncurrent assets) — 7 1 (5 ) 3 12 15 Total mark-to-market derivative assets — 22 4 (18 ) 8 12 20 Mark-to-market derivative liabilities (current liabilities) (1 ) (17 ) (2 ) 13 (7 ) — (7 ) Mark-to-market derivative liabilities (noncurrent liabilities) — (8 ) (1 ) 5 (4 ) — (4 ) Total mark-to-market derivative liabilities (1 ) (25 ) (3 ) 18 (11 ) — (11 ) Total mark-to-market derivative net assets (liabilities) $ (1 ) $ (3 ) $ 1 $ — $ (3 ) $ 12 $ 9 _________ (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 counterparty 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, 2016 : Generation Exelon Corporate Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary Trading (a) Collateral and Netting (b) Subtotal Derivatives Designated as Hedging Instruments 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 counterparty 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: Three Months Ended March 31, Income Statement Location 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on Borrowings Exelon Interest expense $ (4 ) $ 17 $ 8 $ (15 ) At March 31, 2017 , Exelon had total outstanding fixed-to-floating fair value hedges related to interest rate swaps of $800 million , with a derivative asset of $12 million . 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 . During the three months ended March 31, 2017 and 2016 , the impact on the results of operations as a result of ineffectiveness from fair value hedges was a $4 million gain and a $2 million gain, respectively. Cash Flow Hedges . 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 10 — 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 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 of the Exelon 2016 Form 10-K for additional information regarding the financing. The swaps have a notional amount of $164 million as of March 31, 2017 and expire in 2020. The swaps are designated as cash flow hedges. At March 31, 2017 , the subsidiary had a $1 million derivative liability related to the swaps. During the three months ended March 31, 2017 and 2016 , 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 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 of the Exelon 2016 Form 10-K for additional information regarding the financing. The swaps have a notional amount of $494 million as of March 31, 2017 and expire in 2019. The swap was designated as a cash flow hedge in the fourth quarter of 2014. During the first quarter of 2017, the swap was de-designated. At March 31, 2017 , the subsidiary had a $7 million derivative liability related to the swap. 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 of the Exelon 2016 Form 10-K 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 of the Exelon 2016 Form 10-K 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. At March 31, 2017 , Generation had immaterial notional amounts of interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions and $73 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 margin on exchange positions, is aggregated in the collateral and netting column. As of both March 31, 2017 and December 31, 2016 , $8 million of cash collateral held 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 March 31, 2017 : Successor Generation ComEd DPL PHI Exelon Derivatives Economic Hedges Proprietary Trading Collateral and Netting (a) (e) Subtotal (b) Economic Hedges (c) Economic Hedges (d) Collateral and Netting (a) Subtotal Subtotal Total Derivatives Mark-to-market derivative assets (current assets) $ 3,398 $ 56 $ (2,612 ) $ 842 $ — $ — $ — $ — $ — $ 842 Mark-to-market derivative assets (noncurrent assets) 1,975 24 (1,475 ) 524 — — — — — 524 Total mark-to-market derivative assets 5,373 80 (4,087 ) 1,366 — — — — — 1,366 Mark-to-market derivative liabilities (current liabilities) (3,029 ) (49 ) 2,876 (202 ) (19 ) — — — — (221 ) Mark-to-market derivative liabilities (noncurrent liabilities) (1,780 ) (28 ) 1,655 (153 ) (263 ) — — — — (416 ) Total mark-to-market derivative liabilities (4,809 ) (77 ) 4,531 (355 ) (282 ) — — — — (637 ) Total mark-to-market derivative net assets (liabilities) $ 564 $ 3 $ 444 $ 1,011 $ (282 ) $ — $ — $ — $ — $ 729 ______ (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 $128 million and $77 million , respectively, and current and noncurrent liabilities are shown net of collateral of $136 million and $103 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $444 million at March 31, 2017 . (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. (e) Of the collateral posted/(received), $14 million represents variation margin on the exchanges. 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 Description Economic Hedges Proprietary Trading Collateral and Netting (a) (e) Subtotal (b) Economic Hedges (c) Economic Hedges (d) Collateral and Netting (a) Subtotal Subtotal Total Mark-to-market derivative assets (current assets) $ 3,623 $ 55 $ (2,769 ) $ 909 $ — $ 2 $ (2 ) $ — $ — $ 909 Mark-to

Debt and Credit Agreements (All

Debt and Credit Agreements (All Registrants)	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
Debt and Credit Agreements (All Registrants)	10 . Debt and Credit Agreements (All Registrants) Short-Term Borrowings Exelon, Pepco, DPL and ACE meet their short-term liquidity requirements primarily through the issuance of commercial paper and short-term notes. 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. Commercial Paper The Registrants had the following amounts of commercial paper borrowings outstanding as of March 31, 2017 and December 31, 2016 : Commercial Paper Borrowings March 31, 2017 December 31, 2016 Exelon Corporate $ 204 $ — Generation 579 620 ComEd 365 — PECO — — BGE 95 45 PHI Corporate — — Pepco 167 23 Short-Term Loan Agreements 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. On March 23, 2017, the aggregate principal amount of all loans, together with any accrued but unpaid interest due under the loan agreement was fully repaid and the loan terminated. On March 23, 2017, Exelon Corporate entered into a similar type term loan for $500 million which expires on March 22, 2018. Pursuant to the loan agreement, loans made thereunder bear interest at a variable rate equal to LIBOR plus 1% and all indebtedness thereunder is unsecured. The loan agreement is reflected in Exelon’s Consolidated Balance Sheet within Short-Term borrowings. Credit Agreements On January 5, 2016, Generation entered into a credit agreement establishing a $150 million bilateral credit facility, scheduled to mature in January 2019. This facility will solely be utilized by Generation to issue letters of credit. This facility does not back Generation's commercial paper program. On January 9, 2017, the credit agreement for Generation's $75 million bilateral credit facility was amended and restated to increase the facility size to $100 million and extend the maturity to January 2019. This facility will solely be used by Generation to issue letters of credit. 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) converted its financial covenant from a debt to capitalization leverage ratio to an interest coverage ratio. Long-Term Debt Issuance of Long-Term Debt During the three months ended March 31, 2017 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Generation Energy Efficiency Project Financing 3.72 % April 30, 2018 $ 1 Funding to install energy conservation measures for the Smithsonian Zoo project Generation Energy Efficiency Project Financing 2.61 % September 30, 2018 $ 1 Funding to install energy conservation measures for the Pensacola project Generation Energy Efficiency Project Financing 3.90 % January 31, 2018 $ 6 Funding to install energy conservation measures for the Naval Station Great Lakes project Generation Albany Green Energy Project Financing LIBOR + 1.25% November 17, 2017 $ 13 Albany Green Energy biomass generation development Generation Senior Notes 2.95 % January 15, 2020 $ 250 Repay outstanding commercial paper obligations and for general corporate purposes. Generation Senior Notes 3.40 % March 15, 2022 $ 500 Repay outstanding commercial paper obligations and for general corporate purposes. Pepco Energy Efficiency Project Financing 3.30 % December 15, 2017 $ 1 Funding to install energy conservation measures for the DOE Germantown project EGTP Nonrecourse Debt In September 2014, EGTP, an indirect subsidiary of Exelon and Generation, issued $675 million aggregate principal amount of a nonrecourse senior secured term loan. The net proceeds were distributed to Generation for general business purposes. The loan is scheduled to mature on September 18, 2021. The term loan bears interest at a variable rate equal to LIBOR plus 4.75% , subject to a 1% LIBOR floor with interest payable quarterly. As of March 31, 2017 , $658 million was outstanding. As part of the agreement, a revolving credit facility was established for the amount of $20 million available through, and scheduled to mature on September 18, 2019. In addition to the financing, EGTP entered into various interest rate swaps with an initial notional amount of approximately $505 million at an interest rate of 2.34% to hedge a portion of the interest rate exposure in connection with this financing, as required by the debt covenants. See Note 9 — Derivative Financial Instruments for additional information regarding interest rate swaps. See Note 20 - Subsequent Events for additional information regarding EGTP and the associated nonrecourse debt. 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. Each equity unit represented an undivided beneficial ownership interest in Exelon’s $1.15 billion of 2.50% junior subordinated notes due in 2024 (“2024 notes”) and a forward equity purchase contract. As contemplated in the June 2014 equity unit structure, in April 2017, Exelon completed the remarketing of the 2024 notes into $1.15 billion of 3.497% junior subordinated notes due in 2022 (“Remarketing”). Exelon conducted the Remarketing on behalf of the holders of equity units and did not directly receive any proceeds therefrom. Instead, the former holders of the 2024 notes may use debt remarketing proceeds towards settling the forward equity purchase contract with Exelon on June 1, 2017. Exelon will receive $1.15 billion upon settlement on June 1, 2017, of the forward equity purchase contract. Exelon currently expects the number of equity shares to be issued to range from 26 million to 33 million dependent on Exelon’s stock price at the time of settlement pursuant to the equity unit terms. Until settlement of the equity purchase contract, earnings per share dilution resulting from the equity units is being determined under the treasury stock method. For the three months ended March 31, 2017 and 2016 , contract payments of $11 million related to the Contract Payment Obligation were included within Retirements of long-term debt in Exelon’s Consolidated Statements of Cash Flows.

Income Taxes (All Registrants)

Income Taxes (All Registrants)	3 Months Ended
	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes (All Registrants)	Income Taxes (All Registrants) The effective income tax rate from continuing operations varies from the U.S. Federal statutory rate principally due to the following: Three Months Ended March 31, 2017 Successor 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 0.9 1.0 4.9 0.1 5.2 4.6 5.3 5.6 4.9 Qualified nuclear decommissioning trust fund income 3.4 7.6 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.4) (0.7) (0.2) (0.1) (0.1) (0.1) (0.3) (0.4) (0.2) Plant basis differences (2.4) — (0.2) (13.2) (0.9) (5.8) (1.9) (3.4) (3.8) Production tax credits and other credits (0.6) (1.4) — — — — — — — Noncontrolling interests (0.1) (0.3) — — — — — — — Merger expenses (a) (11.4) (3.3) — — — (34.2) (21.9) (167.1) (42.4) Fitzpatrick bargain purchase gain (6.6) (14.5) — — — — — — — Other — (0.1) — 0.3 (0.2) 0.5 — (3.0) (0.4) Effective income tax rate 17.8% 23.3% 39.5% 22.1% 39.0% 0.0% 16.2% (133.3)% (6.9)% Successor Predecessor Three Months Ended March 31, 2016 March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco (b) DPL (b) ACE (b) PHI (b) 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 (c) (1.1) 3.7 5.1 1.0 5.2 (2.5) (2.7) 5.9 5.4 11.9 Qualified nuclear decommissioning trust fund income 5.6 4.2 — — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.6) (1.0) (0.3) (0.1) (0.1) — 0.1 0.2 — (0.9) Plant basis differences (5.5) — (0.1) (9.3) (0.6) 2.8 0.7 0.6 — (13.5) Production tax credits and other credits (5.1) (3.9) — — — — — — — — Noncontrolling interests 0.5 0.3 — — — — — — — — Merger expenses 33.6 — — — — (16.5) (22.1) (17.0) (15.1) 11.1 Other (2.0) (1.6) 0.4 (0.9) — — 0.1 0.1 0.2 3.6 Effective income tax rate 59.4% 36.7% 40.1% 25.7% 39.5% 18.8% 11.1% 24.8% 25.5% 47.2% (a) Includes a remeasurement of uncertain federal and state income tax positions, see below. (b) Pepco, DPL and ACE recognized a loss before income taxes for the three months ended March 31, 2016 , and PHI recognized a loss before income taxes for the period of March 24, 2016, through March 31, 2016 . As a result, positive percentages represent an income tax benefit for the periods presented. (c) Includes a remeasurement of uncertain state income tax positions for Pepco and DPL. -31 Accounting for Uncertainty in Income Taxes The Registrants have the following unrecognized tax benefits as of March 31, 2017 and December 31, 2016 : Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE March 31, 2017 $ 769 $ 470 $ (12 ) $ — $ 120 $ 112 $ 59 $ 21 $ — Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE December 31, 2016 $ 916 $ 490 $ (12 ) $ — $ 120 $ 172 $ 80 $ 37 $ 22 Exelon established a liability for an uncertain tax position associated with the tax deductibility of certain merger commitments incurred by Exelon in connection with the acquisitions of Constellation in 2012 and PHI in 2016. In the first quarter 2017, as a part of its examination of Exelon’s return, the IRS National Office issued guidance concurring with Exelon’s position that the merger commitments were deductible. As a result, Exelon, Generation, PHI, Pepco, DPL, and ACE decreased their liability for unrecognized tax benefits by $ 146 million , $ 19 million , $ 59 million , $ 21 million , $ 16 million , and $ 22 million , respectively, as of March 31, 2017 , resulting in a benefit to Income taxes on Exelon’s, Generation’s, PHI’s, Pepco’s, DPL’s and ACE’s Consolidated Statements of Operations and Comprehensive Income and corresponding decreases in their effective tax rates. Reasonably possible the total amount of unrecognized tax benefits could significantly increase or decrease within 12 months after the reporting date Like-Kind Exchange As of March 31, 2017 , Exelon and ComEd have approximately $ 76 million and $(12) million , respectively, of unrecognized state income tax benefits that could significantly decrease and increase within the 12 months after the reporting date due to a final resolution of the like-kind exchange litigation described below. The recognition of these unrecognized tax benefits would decrease Exelon’s effective tax rate and increase ComEd’s effective tax rate. Settlement of Income Tax Audits As of March 31, 2017 , Exelon, Generation, BGE, PHI, Pepco, and DPL have approximately $257 million , $ 57 million , $120 million , $ 80 million , $ 59 million , and $ 21 million of unrecognized federal and state tax benefits that could significantly decrease within the 12 months after the reporting date as a result of completing audits and potential settlements. Of the above unrecognized tax benefits, Exelon and Generation have $ 50 million that, if recognized, would decrease the effective tax rate. The unrecognized tax benefits related to BGE, DPL, and a portion of Pepco, if recognized, may be included in future regulated base rates and that portion would have no impact to the effective tax rate. Other Income Tax Matters Like-Kind Exchange (Exelon and ComEd) 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. 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. Exelon expects to timely appeal this decision to the U.S. Court of Appeals for the Seventh Circuit in 2017. In the first quarter of 2013, Exelon concluded that it was no longer more likely than not that the like-kind exchange position would be sustained and recorded charges to earnings representing the amount of interest expense (after-tax) and incremental state income tax expense that would be payable in the event Exelon is unsuccessful in litigation. Prior to the Tax Court’s decision, however, Exelon did not believe it was likely a penalty would be assessed based on applicable case law and the facts of the transaction. As a result, no charge had been recorded for the penalty or for after-tax interest on the penalty. 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 ultimate imposition of 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 addition, while further adjustments may be required, Exelon currently estimates that its income tax expense may decrease by as much as $ 50 million and ComEd’s income tax expense may increase by as much as $ 20 million resulting from the IRS's completion of its calculation of tax, penalties, and interest in the second quarter of 2017. In order to appeal the decision, Exelon is required to pay the tax, penalties and interest at the time Exelon files its appeal (expected in the third quarter of 2017). While the final calculation of tax, penalties and interest has not yet been finalized by the IRS, Exelon estimates that a payment of approximately $ 1.3 billion related to the like-kind exchange will be due, including $ 300 million from ComEd, in the third quarter of 2017. While Exelon will receive a tax benefit of approximately $ 350 million associated with the deduction for the interest, Exelon currently has 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 approximately $ 950 million , 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 approximately $ 80 million related to final interest computations . Of the above amounts payable, Exelon deposited with the IRS $ 1.25 billion in October of 2016. The remaining amount will be paid in the third 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 March 31, 2017 , 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 third quarter of 2017. Exelon will not seek recovery from ComEd customers for any interest or penalty payment 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 . In the first quarter of 2016, Exelon terminated its interests in the remaining two municipal-owned electric generation properties in exchange for $ 360 million . Long-Term Marginal State Income Tax Rate (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. Exelon and PHI's long-term marginal state income tax rate was revised in the first quarter of 2017 as a result of a statutory rate change pursuant to Exelon's marginal state income tax rate policy, resulting in the recording of a deferred state tax benefit for Exelon of $ 21 million , net of tax.

Nuclear Decommissioning (Exelon

Nuclear Decommissioning (Exelon and Generation)	3 Months Ended
	Mar. 31, 2017
Environmental Remediation Obligations [Abstract]
Nuclear Decommissioning (Exelon and Generation)	Nuclear Decommissioning (Exelon and Generation) 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 December 31, 2016 to March 31, 2017 : Nuclear decommissioning ARO at December 31, 2016 (a) $ 8,734 Acquisition of FitzPatrick 417 Accretion expense 109 Costs incurred to decommission retired plants (1 ) Nuclear decommissioning ARO at March 31, 2017 (a)(b) $ 9,259 _________ (a) Includes $11 million and $10 million for the current portion of the ARO at March 31, 2017 and December 31, 2016 , respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets. (b) Includes the fair value of the FitzPatrick ARO liability as of March 31, 2017, the date of the acquisition. See Note 4 - Mergers, Acquisitions and Dispositions . During the three months ended March 31, 2017 , Generation’s nuclear ARO increased by approximately $ 525 million . The increase is largely driven by the acquisition of FitzPatrick. The fair value of FitzPatrick’s assets and liabilities, including the ARO, was determined based on significant estimates and assumptions that are judgmental in nature. The fair value of the ARO is considered an initial estimate and will be updated with inputs from a third party engineering firm with corresponding adjustments recorded by the end of 2017. For additional details on the acquisition of FitzPatrick, see Note 4 - Mergers, Acquisitions and Dispositions . Nuclear Decommissioning Trust Fund Investments NDT funds have been established for each generation 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. On March 31, 2017, PECO filed its Nuclear Decommissioning Cost Adjustment (NDCA) with the PAPUC proposing an annual recovery from customers of approximately $4 million which, if approved by the PAPUC, will be effective January 1, 2018. This amount reflects a decrease from the current approved annual collection of approximately $24 million primarily due to the removal of the collections for Limerick Units 1 and 2 as a result of the NRC approving the extension of the operating licenses for an additional 20 years. See Note 16 - Asset Retirement Obligations of Exelon's 2016 Form 10-K, for information regarding the amount collected from PECO ratepayers for decommissioning costs. At March 31, 2017 and December 31, 2016 , Exelon and Generation had NDT fund investments totaling $12,362 million and $11,061 million , respectively. The increase is primarily driven by the acquisition of FitzPatrick. The following table provides unrealized gains on NDT funds for the three months ended March 31, 2017 and 2016 : Exelon and Generation Three Months Ended 2017 2016 Net unrealized gains on decommissioning trust funds — Regulatory Agreement Units (a) $ 222 $ 79 Net unrealized gains on decommissioning trust funds — Non-Regulatory Agreement Units (b)(c) 166 52 _________ (a) Net unrealized gains 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 and $2 million of net unrealized gains (losses) related to the Zion Station pledged assets for the three months ended March 31, 2017 and 2016 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 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. Refer to Note 3 — Regulatory Matters and Note 27 — Related Party Transactions of the Exelon 2016 Form 10-K 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 completing certain decommissioning activities at Zion Station, which is located in Zion, Illinois and ceased operation in 1998. See Note 16 — Asset Retirement Obligations of the Exelon 2016 Form 10-K for information regarding the specific treatment of assets, including NDT funds, and decommissioning liabilities transferred in the transaction. 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, are 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 $112 million which is included within the nuclear decommissioning ARO at March 31, 2017 . 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 March 31, 2017 and December 31, 2016 : Exelon and Generation March 31, 2017 December 31, 2016 Carrying value of Zion Station pledged assets $ 95 $ 113 Payable to Zion Solutions (a) 88 104 Current portion of payable to Zion Solutions (b) 85 90 Cumulative withdrawals by Zion Solutions to pay decommissioning costs (c) 895 878 _________ (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. 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. Generation filed its biennial decommissioning funding status report with the NRC on March 30, 2017 for all units 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 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 has been adjusted in the March 31, 2017 filing to the PAPUC which, if approved by the PAPUC, will be effective January 1, 2018.

Retirement Benefits (All Regist

Retirement Benefits (All Registrants)	3 Months Ended
	Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Retirement Benefits (Exelon, Generation, ComEd, PECO and BGE)	Retirement Benefits (All Registrants) Exelon sponsors defined benefit pension plans and other postretirement benefit plans for essentially all employees. Effective March 31, 2017, in connection with the acquisition of FitzPatrick, Exelon established a new qualified pension plan and a new other postretirement employee benefit plan, and recorded benefit plan obligations of $38 million and $11 million , respectively. Refer to Note 4 - Mergers, Acquisitions and Dispositions for additional discussion of the acquisition of FitzPatrick. 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. Defined Benefit Pension and Other Postretirement Benefits During the first quarter of 2017 , Exelon received an updated valuation of its pension and other postretirement benefit obligations to reflect actual census data as of January 1, 2017 . This valuation resulted in an increase to the pension obligation of $92 million and an increase to the other postretirement benefit obligation of $57 million . Additionally, accumulated other comprehensive loss increased by approximately $59 million (after tax), regulatory assets increased by approximately $57 million and regulatory liabilities increased by approximately $4 million . The majority of the 2017 pension benefit cost for Exelon-sponsored plans is calculated using an expected long-term rate of return on plan assets of 7.00% and a discount rate of 4.04% . The majority of the 2017 other postretirement benefit cost is calculated using an expected long-term rate of return on plan assets of 6.58% for funded plans and a discount rate of 4.04% . A portion of the net periodic benefit cost for all plans is capitalized within the Consolidated Balance Sheets. The following tables present the components of Exelon's net periodic benefit costs, prior to capitalization, for the three months ended March 31, 2017 and 2016 and PHI's net periodic benefit costs, prior to capitalization, for the predecessor period of January 1, 2016 to March 23, 2016 . Pension Benefits Other Postretirement Benefits 2017 2016(a) 2017 2016(a) Components of net periodic benefit cost: Service cost $ 95 $ 78 $ 26 $ 26 Interest cost 210 190 45 43 Expected return on assets (299 ) (263 ) (41 ) (38 ) Amortization of: Prior service cost (benefit) — 3 (47 ) (44 ) Actuarial loss 152 127 16 14 Net periodic benefit cost $ 158 $ 135 $ (1 ) $ 1 _______ (a) PHI net periodic benefit costs for the period prior to the merger are not included in the table above. Predecessor PHI Pension Benefits Other Postretirement Benefits January 1, 2016 to March 23, 2016 January 1, 2016 to March 23, 2016 Components of net periodic benefit cost: Service cost $ 12 $ 1 Interest cost 26 6 Expected return on assets (30 ) (5 ) Amortization of: Prior service cost (benefit) — (3 ) Actuarial loss 14 2 Net periodic benefit cost $ 22 $ 1 The amounts below represent Exelon's, Generation's, ComEd's, PECO's, BGE's, PHI's, Pepco's, DPL's, ACE's, BSC's and PHISCO's allocated portion of the pension and postretirement benefit plan costs, which were included in Property, plant and equipment within the respective Consolidated Balance Sheets and Operating and maintenance expense within the Consolidated Statement of Operations and Comprehensive Income during the three months ended March 31, 2017 and 2016 and PHI's for the predecessor and successor periods of January 1, 2016 to March 23, 2016 and March 24, 2016 to March 31, 2016 , respectively. Three Months Ended March 31, Pension and Other Postretirement Benefit Costs 2017 2016 Exelon $ 157 $ 136 Generation 54 54 ComEd 44 41 PECO 7 8 BGE 16 16 BSC (a) 12 14 Pepco (b) 7 8 DPL (b) 3 5 ACE (b) 3 4 PHISCO (a)(b) 11 9 Successor Predecessor Pension and Other Postretirement Benefit Costs March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 PHI $ 3 $ 23 _________ (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, PHI, Pepco, DPL or ACE amounts above. (b) Pepco's, DPL's, ACE's and PHISCO's pension and postretirement benefit costs for the three months ended March 31, 2016 include $7 million , $4 million , $3 million and $9 million , respectively, of costs incurred prior to the closing of Exelon’s merger with PHI on March 23, 2016 . Defined Contribution Savings Plans The Registrants participate in various 401(k) defined contribution savings plans that are sponsored by Exelon. The plans are qualified under applicable sections of the IRC and allow employees to contribute a portion of their pre-tax and/or after-tax income in accordance with specified guidelines. All Registrants match a percentage of the employee contributions up to certain limits. The following table presents the matching contributions to the savings plans during the three months ended March 31, 2017 and 2016 : Three Months Ended March 31, Savings Plan Matching Contributions 2017 2016 Exelon $ 30 $ 26 Generation 14 12 ComEd 7 6 PECO 2 2 BGE 2 1 BSC (a) 2 5 Pepco (b) 1 1 DPL (b) 1 1 PHISCO (a)(b) 1 1 Successor Predecessor Savings Plan Matching Contributions March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 PHI $ — $ 3 _________ (a) These amounts primarily represent amounts billed to Exelon and PHI's subsidiaries through intercompany allocations. These costs are not included in the Generation, ComEd, PECO, BGE, Pepco and DPL amounts above. (b) Pepco's, DPL's and PHISCO's matching contributions for the three months ended March 31, 2016 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 for the three months ended March 31, 2016.

Severance (All Registrants)

Severance (All Registrants)	3 Months Ended
	Mar. 31, 2017
Restructuring Charges [Abstract]
Severance (All Registrants)	Severance (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 three months ended March 31, 2017 and 2016 , Exelon, Generation, and ComEd recorded the following severance costs (benefits) associated with these ongoing severance benefits within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income. Exelon Generation (a) ComEd (a) Three Months Ended March 31, 2017 $ 4 $ 3 $ 1 March 31, 2016 2 2 — _______ (a) The amounts above for Generation include $1 million for amounts billed by BSC through intercompany allocations for both the three months ended March 31, 2017 and 2016 . Amounts billed by BSC to ComEd were immaterial. 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. For the three months ended March 31, 2017 and 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 Three Months Ended March 31, 2017 (a) $ (1 ) $ (1 ) $ — $ — $ — March 31, 2016 (b) $ 17 $ 12 $ 3 $ 1 $ 1 _______ (a) Amounts billed by BSC through intercompany allocations for the three months ended March 31, 2017 were immaterial. (b) 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 three months ended March 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 three months ended March 31, 2017 , the PHI merger severance costs were immaterial. For the three months ended March 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 DPL ACE Three Months Ended March 31, 2016 Severance benefits (a) $ 52 $ 10 $ 2 $ 1 $ 1 $ 37 $ 18 $ 11 $ 8 ______________ (a) The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $9 million , $2 million , $1 million , $1 million , $18 million , $11 million and $8 million , respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the three months ended March 31, 2016 . Severance Liability Amounts included in the table below represent the severance liability recorded for the severance plans above 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 Pepco DPL ACE Balance at December 31, 2016 $ 88 $ 36 $ 3 $ — $ — $ 29 $ — $ — $ — Severance charges (a) 3 1 — — — — — — — Payments (10 ) (3 ) — — — (5 ) — — — Balance at March 31, 2017 $ 81 $ 34 $ 3 $ — $ — $ 24 $ — $ — $ — ______________ (a) Includes salary continuance and health and welfare severance benefits.

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Exelon, Generation, PECO and PHI)	3 Months Ended
	Mar. 31, 2017
Changes in Accumulated Other Comprehensive Income [Abstract]
Comprehensive Income (Loss) Note [Text Block]	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 three months ended March 31, 2017 and 2016 : Three Months Ended March 31, 2017 Gains and (losses) on Cash Flow Hedges Unrealized Gains and (losses) on Marketable Securities Pension and Non-Pension Postretirement Benefit Plan Items Foreign Currency Items AOCI of Equity Investments Total Exelon (a) Beginning balance $ (17 ) $ 4 $ (2,610 ) $ (30 ) $ (7 ) $ (2,660 ) OCI before reclassifications 2 1 (59 ) 1 5 (50 ) Amounts reclassified from AOCI (b) 4 — 36 — — 40 Net current-period OCI 6 1 (23 ) 1 5 (10 ) Ending balance $ (11 ) $ 5 $ (2,633 ) $ (29 ) $ (2 ) $ (2,670 ) Generation (a) Beginning balance $ (19 ) $ 2 $ — $ (30 ) $ (7 ) $ (54 ) OCI before reclassifications 2 — — 1 6 9 Amounts reclassified from AOCI (b) 4 — — — — 4 Net current-period OCI 6 — — 1 6 13 Ending balance $ (13 ) $ 2 $ — $ (29 ) $ (1 ) $ (41 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 Three Months Ended March 31, 2016 Gains and (losses) on Hedging Activity Unrealized Gains and (losses) on Marketable Securities Pension and Non-Pension Postretirement Benefit Plan Items Foreign Currency Items AOCI of Equity Investments Total Exelon (a) Beginning balance $ (19 ) $ 3 $ (2,565 ) $ (40 ) $ (3 ) $ (2,624 ) OCI before reclassifications (10 ) (1 ) (1 ) 6 (3 ) (9 ) Amounts reclassified from AOCI (b) 3 — 34 — — 37 Net current-period OCI (7 ) (1 ) 33 6 (3 ) 28 Ending balance $ (26 ) $ 2 $ (2,532 ) $ (34 ) $ (6 ) $ (2,596 ) Generation (a) Beginning balance $ (21 ) $ 1 $ — $ (40 ) $ (3 ) $ (63 ) OCI before reclassifications (8 ) — — 6 (2 ) (4 ) Amounts reclassified from AOCI (b) 3 — — — — 3 Net current-period OCI (5 ) — — 6 (2 ) (1 ) Ending balance $ (26 ) $ 1 $ — $ (34 ) $ (5 ) $ (64 ) 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 ) ________ (a) All amounts are net of tax and noncontrolling interest. Amounts in parenthesis represent a decrease in AOCI. (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 three months ended March 31, 2017 and 2016 . The following tables present amounts reclassified out of AOCI to Net income for Exelon, Generation and PHI during the three months ended March 31, 2017 and 2016 . Three Months Ended March 31, 2017 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statement of Operations and Comprehensive Income Exelon Generation Gains and (losses) on cash flow hedges Other cash flow hedges $ (7 ) $ (7 ) Interest expense Total before tax (7 ) (7 ) Tax benefit 3 3 Net of tax $ (4 ) $ (4 ) Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 23 $ — Actuarial losses (b) (81 ) — Total before tax (58 ) — Tax benefit 22 — Net of tax $ (36 ) $ — Total Reclassifications $ (40 ) $ (4 ) Comprehensive income Three Months Ended March 31, 2016 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statement of Operations and Comprehensive Income Predecessor Exelon Generation PHI Gains and (losses) on cash flow hedges Other cash flow hedges $ (5 ) $ (5 ) — Interest expense Total before tax (5 ) (5 ) — Tax expense 2 2 — Net of tax $ (3 ) $ (3 ) $ — Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 20 $ — $ — Actuarial losses (b) (76 ) — (1 ) Total before tax (56 ) — (1 ) Tax benefit 22 — — Net of tax $ (34 ) $ — $ (1 ) Total Reclassifications $ (37 ) $ (3 ) $ (1 ) Comprehensive income _______ (a) Amounts in parenthesis represent a decrease in net income. (b) This AOCI component is included in the computation of net periodic pension and OPEB cost (see Note 13 — Retirement Benefits for additional details). The following table presents income tax expense (benefit) allocated to each component of other comprehensive income (loss) during the three months ended March 31, 2017 and 2016 : Three Months Ended March 31, 2017 2016 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 10 $ 7 Actuarial loss reclassified to periodic benefit cost (32 ) (30 ) Pension and non-pension postretirement benefit plans valuation adjustment — — Change in unrealized (loss)/gain on cash flow hedges (1 ) 3 Change in unrealized (loss)/gain on equity investments (4 ) 2 Change in unrealized (loss)/gain on marketable securities (1 ) 1 Total $ (28 ) $ (17 ) Generation Change in unrealized (loss)/gain on cash flow hedges $ (1 ) $ 2 Change in unrealized (loss)/gain on equity investments (3 ) 2 Total $ (4 ) $ 4 Predecessor PHI January 1, 2016 to March 23, 2016 Pension and non-pension postretirement benefit plans: Actuarial loss reclassified to periodic cost $ —

Earnings Per Share and Equity (

Earnings Per Share and Equity (Exelon)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share and Equity (Exelon)	Earnings Per Share and Equity (Exelon) Earnings per Share 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 these stock options, performance share awards and restricted stock on the weighted average number of shares outstanding used in calculating diluted earnings per share: Three Months Ended March 31, 2017 2016 Exelon Net income attributable to common shareholders $ 995 $ 173 Weighted average common shares outstanding — basic 928 923 Assumed exercise and/or distributions of stock-based awards 2 2 Weighted average common shares outstanding — diluted 930 925 The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was approximately 9 million and 13 million for the three months ended March 31, 2017 and 2016 , respectively. 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 three months ended March 31, 2017 . 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 was 4 million for the three months ended March 31, 2016 . Refer to Note 20 — Shareholders' Equity of the Exelon 2016 Form 10-K for further information regarding the equity 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 March 31, 2017 . In 2008, Exelon management decided to defer indefinitely any share repurchases.

Commitments and Contingencies (

Commitments and Contingencies (All Registrants)	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies (All Registrants)	17 . Commitments and Contingencies ( All Registrants ) The following is an update to the current status of commitments and contingencies set forth in Note 24 of the Exelon 2016 Form 10-K . See Note 4 - Mergers, Acquisitions and Dispositions for further discussion on the PHI Merger commitments. Commitments Constellation Merger Commitments (Exelon and Generation) 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 $ 550 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 $ 456 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. 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 (Exelon and Generation) 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. As of March 31, 2017 , Generation’s estimated commitments relating to its equity purchase agreements, including the in-kind services contributions, is anticipated to be as follows: Total 2017 $ 9 2018 7 2019 3 Total $ 19 Commercial Commitments (All Registrants) The Registrants’ commercial commitments as of March 31, 2017 , representing commitments potentially triggered by future events were as follows: Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Letters of credit (non-debt) (a) $ 1,527 $ 1,440 $ 14 $ 23 $ 5 $ 1 $ 1 $ — $ — Surety bonds (b) 1,038 964 5 7 11 16 9 4 3 Financing trust guarantees 628 — 200 178 250 — — — — Guaranteed lease residual values (c) 19 — — — — 19 5 7 5 Total commercial commitments $ 3,212 $ 2,404 $ 219 $ 208 $ 266 $ 36 $ 15 $ 11 $ 8 ________ (a) Letters of credit (non-debt) - Exelon and certain 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 $48 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. Nuclear Insurance (Exelon and Generation) 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 March 31, 2017 , 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 $2.8 billion , including CENG's related liability, however any amounts payable under this secondary layer would be capped at $ 420 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 of the Exelon 2016 Form 10-K 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. 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 $ 373 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. Environmental Issues (All Registrants) 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 the remediation has been completed 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 two sites are not considered material. The first phase of an investigation of an additional gas purification site (Riverside) was completed during the first quarter of 2015 at the direction of the MDE and investigations continue under MDE’s direction. 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. ComEd and PECO have recorded regulatory assets for the recovery of these costs. See Note 5 — 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 Three Months Ended March 31, 2017 and December 31, 2016 , 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: March 31, 2017 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 425 $ 319 Generation 71 — ComEd 288 286 PECO 33 31 BGE 4 2 PHI (Successor) 29 — Pepco 26 — DPL 2 — ACE 1 — December 31, 2016 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 429 $ 325 Generation 72 — ComEd 292 291 PECO 33 31 BGE 2 2 PHI (Successor) 30 1 Pepco 27 — DPL 2 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 the time of each study, including probabilistic and deterministic modeling for ComEd and PECO, and the remediation standards currently required by the applicable state environmental agency. Prior to completion of any significant clean up, each site remediation plan is approved by the appropriate state environmental agency. The Registrants cannot reasonably estimate whether they will incur other significant liabilities for additional investigation and remediation costs at these or additional sites identified by the Registrants, environmental agencies or others, or whether such costs will be recoverable from third parties, including customers. Water Quality Benning Road Site NPDES Permit Limit Exceedances . Pepco holds an NPDES permit issued by EPA with a July 19, 2009 effective date, which authorizes discharges from the Benning Road service facility. The 2009 permit for the first time imposed numerical limits on the allowable concentration of certain metals in storm water discharged from the site into the Anacostia River. The permit contemplated that Pepco would meet these limits over time through the use of best management practices (BMPs). The BMPs were effective in reducing metal concentrations in storm water discharges, but were not sufficient to meet all of the numerical limits for all metals. The 2009 permit remains in effect pending EPA’s action on the Pepco renewal application, including resolution of the stormwater compliance issues. On October 30, 2015, EPA filed a Clean Water Act civil enforcement action against Pepco in federal district court, and in March 2016 the court granted a motion by the Anacostia Riverkeeper to intervene in this case as a plaintiff along with EPA. Since 2009 Pepco has installed runoff mitigation measures and implemented new operating procedures to comply with regulations. In January 2017, the parties agreed to a settlement in the form of a Consent Decree whereby Pepco will pay a civil penalty in the amount of $ 1.6 million , continue the BMPs to manage stormwater, construct a new stormwater treatment system, and make certain other capital improvements to the stormwater management system. The Consent Decree has been lodged with the Court and has been subject to a 30-day public comment period. Upon completion of its review of public comments, It is expected that the Court will approve the Consent Decree in the second quarter of 2017. Pepco has established appropriate accruals for the liabilities under the Consent Agreement, which is included in the table above. Solid and Hazardous Waste Cotter Corporation. The EPA has advised Cotter Corporation (Cotter), a former ComEd subsidiary, that it is potentially liable in connection with radiological contamination at a site known as the West Lake Landfill in Missouri. In 2000, ComEd sold Cotter to an unaffiliated third-party. As part of the sale, ComEd agreed to indemnify Cotter for any liability arising in connection with the West Lake Landfill. In connection with Exelon’s 2001 corporate restructuring, this responsibility to indemnify Cotter was transferred to Generation. On May 29, 2008, the EPA issued a Record of Decision approving the remediation option submitted by Cotter and the two other PRPs that required additional landfill cover. The current estimated cost of the landfill cover remediation for the site is approximately $90 million , including escalation, which will be allocated among all PRPs. Generation has accrued what it believes to be an adequate amount to cover its anticipated share of such liability, which is included in the table above. By letter dated January 11, 2010, the EPA requested that the PRPs perform a supplemental feasibility study for a remediation alternative that would involve complete excavation of the radiological contamination. On September 30, 2011, the PRPs submitted the supplemental feasibility study to the EPA for review. Since June 2012, the EPA has requested that the PRPs perform a series of additional analyses and groundwater and soil sampling as part of the supplemental feasibility study, that were completed in December 2016. While the EPA has not yet announced a schedule for selection of the final remedy, the PRPs believe that the EPA announcement of the proposed remedy will not take place until the end of 2017, or possibly the first quarter of 2018. Thereafter, the EPA will select a final remedy and seek to enter into a Consent Decree with the PRPs to effectuate the remedy. Recent investigation has identified a number of other parties who may be PRPs and could be liable to contribute to the final remedy. Further investigation is underway. Generation believes that a partial excavation remedy is reasonably possible, and the partial excavation costs, inclusive of a landfill cover, could range from approximately $ 225 million to $ 650 million; such costs would likely be shared by the final group of identified PRPs. Generation believes the likelihood that the EPA would require a complete excavation remedy is remote. The cost of a partial or complete excavation could have a material, unfavorable impact on Generation’s and Exelon’s future results of operations and cash flows. During December 2015, the EPA took two actions related to the West Lake Landfill designed to abate what it termed as imminent and dangerous conditions at the landfill. The first involved installation by the PRPs of a non-combustible surface cover to protect against surface fires in areas where radiological materials are believed to have been disposed. Generation has accrued what it believes to be an adequate amount to cover its anticipated liability for this interim action. The second action involved EPA's public statement that it will require the PRPs to construct a barrier wall in an adjacent landfill to prevent a subsurface fire from spreading to those areas of the West Lake Landfill where radiological materials are believed to have been disposed. At this time, EPA has not provided sufficient details related to the basis for and the requirements and design of a barrier wall to enable Generation to determine the likelihood such a remedy will ultimately be implemented, assess the degree to which Generation may have liability as a potentially responsible party, or develop a reasonable estimate of the potential incremental costs. It is reasonably possible, however, that resolution of this matter could have a material, unfavorable impact on Generation's and Exelon's future results of operations and cash flows. Finally, one of the other PRPs, the landfill owner and operator of the adjacent landfill, has indicated that it will be making a contribution claim against Cotter for costs that it has incurred to prevent the subsurface fire from spreading to those areas of the West Lake Landfill where radiological materials are believed to have been disposed. At this time, Generation and Exelon do not possess sufficient information to assess this claim and are therefore unable to determine the impact on their future results of operations and cash flows. On February 2, 2016, the U.S. Senate passed a bill to transfer remediation authority over the West Lake Landfill from the EPA to the U.S. Army Corps of Engineers, under the Formerly Utilized Sites Remedial Action Program (FUSRAP). The legislation was not passed in the U.S. House of Representatives, and would therefore require reintroduction in the Senate for consideration in the current session of Congress. Should such proposed legislation ultimately become law, it would be subject to annual funding appropriations in the U.S. Budget. Remediation under FUSRAP would not alter the liability of the PRPs, but would likely delay the determination of a final remedy and its implementation. On A ugust 8, 2011, Cotter was notified by the DOJ that Cotter is considered a PRP with respect to the government’s clean-up costs for contamination attributable to low level radioactive residues at a former storage and reprocessing facility named Latty Avenue near St. Louis, Missouri. The Latty Avenue site is included in ComEd’s indemnification responsibilities discussed above as part of the sale of Cotter. The radioactive residues had been generated initially in connection with the processing of uranium ores as part of the U.S. government’s Manhattan Project. Cotter purchased the residues in 1969 for initial processing at the Latty Avenue facility for the subsequent extraction of uranium and metals. In 1976, the NRC found that the Latty Avenue site had radiation levels exceeding NRC criteria for decontamination of land areas. Latty Avenue was investigated and remediated by the United States Army Corps of Engineers pursuant to funding under the FUSRAP. The DOJ has not yet formally advised the PRPs of the amount that it is seeking, but it is believed to be approximately $90 million . The DOJ and the PRPs agreed to toll the statute of limitations until August 2017 so that settlement discussions could proceed. Based on Generation’s preliminary review, it appears probable that Generation has liability to Cotter under the indemnification agreement and has established an appropriate accrual for this liability, which is included in the table above. Commencing in February 2012, a number of lawsuits have been filed in the U.S. District Court for the Eastern District of Missouri. Among the defendants were Exelon, Generation and ComEd, all of which were subsequently dismissed from the case, as well as Cotter, which remains a defendant. The suits allege that individuals living in the North St. Louis area developed some form of cancer or other serious illness due to Cotter's negligent or reckless conduct in processing, transporting, storing, handling and/or disposing of radioactive materials. Plaintiffs are asserting public liability claims under the Price-Anderson Act. Their state law claims for negligence, strict liability, emotional distress, and medical monitoring have been dismissed. The complaints do not contain specific damage claims. In the event of a finding of liability against Cotter, it is reasonably possible that Exelon would be financially responsible due to its indemnification responsibilities of Cotter described above. The court has dismissed a number of lawsuits, and is expected to dismiss additional lawsuits based on a recent ruling. Pre-trial motions and discovery are proceeding in the remaining cases and a pre-trial scheduling order has been filed with the court. At this stage of the litigation, Generation and ComEd cannot estimate a range of loss, if any. 68 th Street Dump. In 1999, the EPA proposed to add the 68th Street Dump in Baltimore, Maryland to the Superfund National Priorities List, and notified BGE and 19 others that they are PRPs at the site. In connection with BGE's 2000 corporate restructuring the responsibility for this liability was transferred to Constellation and as a result of the 2012 Exelon and CEG merger is now Generation's responsibility. In March 2004, the PRPs formed the 68th Street Coalition and entered into consent order negotiations with the U.S. EPA to investigate clean-up options for the site under the Superfund Alternative Sites Program. In May 2006, a settlement among the U.S. EPA and the PRPs with respect to investigation of the site became effective. The settlement requires the PRPs, over the course of several years, to identify contamination at the site and recommend clean-up options. The PRPs submitted their investigation of the range of clean-up options in the first quarter of 2011. Although the investigation and options provided to the U.S. EPA are still subject to U.S. EPA review and selection of a remedy, the range of estimated clean-up costs to be allocated among all of the PRPs is in the range of $50 million to $64 million . On September 30, 2013, EPA issued the Record of Decision identifying its preferred remedial alternative for the site. The estimated cost for the alternative chosen by EPA is consistent with the PRPs estimated range of costs noted above. Based on Generation’s preliminary review, it appears probable that Generation has liability and has established an appropriate accrual for its share of the estimated clean-up costs which is included in the table above. Rossville Ash Site. The Rossville Ash Site is a 32-acre property located in Rosedale, Baltimore County, Maryland, which was used for the placement of fly ash from 1983-2007. The property is owned by Constellation Power Source Generation, LLC (CPSG), a wholly-owned subsidiary of Generation. In 2008, CPSG investigated and remediated the property by entering it into the Maryland Voluntary Cleanup Program (VCP) to address any historic environmental concerns and ready the site for appropriate future redevelopment. The site was accepted into the program in 2010 and is currently going through the process to remediate the site and receive closure from MDE. Exelon currently estimates the cost to close the site to be approximately $4 million which has been fully reserved and included in the table above as of March 31, 2017 . Sauer Dump. On May 30, 2012, BGE was notified by the U.S. EPA that it is considered a PRP at the Sauer Dump Superfund site in Dundalk, Maryland. The U.S. EPA offered BGE and three other PRPs the opportunity to conduct an environmental investigation and present cleanup recommendations at the site. In addition, the U.S. EPA is seeking recovery from the PRPs of $1.7 million for past cleanup and investigation costs at the site. On March 11, 2013, BGE and three other PRPs signed an Administrative Settlement Agreement and Order on Consent with the U.S. EPA which requires the PRPs to conduct a remedial investigation and feasibility study at the site to determine what, if any, are the appropriate and recommended cleanup activities for the site. The ultimate outcome of this proceeding is uncertain. Since the U.S. EPA has not selected a cleanup remedy and the allocation of the cleanup costs among the PRPs has not been determined, an estimate of the range of BGE’s reasonably possible loss, if any, cannot be determined. It is possible, however, that resolution of this matter could have a material, unfavorable impact on Exelon's and BGE’s future results of operations and cash flows , and an appropriate accrual has been established and is included in the table above. Riverside. In 2013, the MDE, at the request of EPA, conducted a site inspection and limited environmental sampling of certain portions of the 170 acre Riverside property owned by BGE. The site consists of several different parcels with different current and historical uses. The sampling included soil and groundwater samples for a number of potential environmental contaminants. The sampling confirmed the existence of contaminants consistent with the known historical uses of the various portions of the site. In March 2014, the MDE requested that BGE conduct an investigation which included a site-wide investigation of soils, sediment, groundwater, and surface water to complement the MDE sampling. The field investigation was completed in January 2015, and a final report was provided to MDE in June 2015. In November 2015, MDE provided BGE with its comments and recommendations on the report which require BGE to conduct further investigation and sampling at the site to better delineate the nature and extent of historic contamination, including off-site sediment and soil sampling. MDE did not request any interim remediation at this time and BGE anticipates completing the additional work requested by the end of the second quarter of 2017. BGE has established what it believes is an appropriate reserve based upon the investigation to date. The established reserve is included in the table above. As the investigation and potential remediation proceed, it is possible that additional reserves could be established, in amounts that could be material to BGE. 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. Benning Road Site. In September 2010, PHI received a letter from EPA identifying the Benning Road site as one of six land-based sites potentially contributing to contamination of the lower Anacostia River. A portion of the site was formerly the location of a Pepco Energy Services electric generating facility. That generating facility was deactivated in June 2012 and plant structure demolition was completed in July 2015. The remaining portion of the site consists of a Pepco transmission and distribution service center that remains in operation. In December 2011, the U.S. District Court for the District of Columbia approved a consent decree entered into by Pepco and Pepco Energy Services with the DOEE, which requires Pepco and Pepco Energy Services to conduct a RI/FS for the Benning Road site and an approximately 10 to 15 acre portion of the adjacent Anacostia River. The RI/FS will form the basis for the remedial actions for the Benning Road site and for the Anacostia River sediment associated with the site. The consent decree does not obligate Pepco or Pepco Energy Services to pay for or perform any remediation work, but it is anticipated that DOEE will look to Pepco and Pepco Energy Services to assume responsibility for cleanup of any conditions in the river that are determined to be attributable to past activities at the Benning Road site. The initial RI field work began in January 2013 and was completed in December 2014. In April 2015, Pepco and Pepco Energy Services submitted a draft RI Report to DOEE. After review, DOEE determined that additional field investigation and data analysis was required to complete the RI process (much of which was beyond the scope of the original DOEE-approved RI work plan). In the meantime, Pepco and Pepco Energy Services revised the draft RI Report to address DOEE’s comments and DOEE released the draft RI Report for public review in February 2016. Once the additional RI work has been completed, Pepco and Pepco Energy Services will issue a draft “final” RI report for review and comment by DOEE and the public. Pepco and Pepco Energy Services will then

Supplemental Financial Informat

Supplemental Financial Information (All Registrants)	3 Months Ended
	Mar. 31, 2017
Supplemental Financial Information [Abstract]
Supplemental Financial Information (All Registrants)	18 . 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 three months ended March 31, 2017 and 2016 . Three Months Ended March 31, 2017 Successor 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 $ 68 $ 68 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 32 32 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 222 222 — — — — — — — Non-regulatory agreement units 166 166 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (1 ) (1 ) — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (234 ) (234 ) — — — — — — — Total decommissioning-related activities 253 253 — — — — — — — Investment income 2 2 — — — — — — — Interest income related to uncertain income tax positions 1 — — — — — — — — AFUDC — Equity 17 — 2 2 4 9 5 2 2 Other 10 4 2 — — 4 3 1 — Other, net $ 283 $ 259 $ 4 $ 2 $ 4 $ 13 $ 8 $ 3 $ 2 Successor Predecessor Three Months Ended March 31, 2016 March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 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 $ 34 $ 34 $ — $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 21 21 — — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 79 79 — — — — — — — — Non-regulatory agreement units 52 52 — — — — — — — — Net unrealized gains on pledged assets Zion Station decommissioning 2 2 — — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (95 ) (95 ) — — — — — — — — Total decommissioning-related activities 93 93 — — — — — — — — Investment income 6 1 — — 1 — — — — — Long-term lease income 4 — — — — — — — — — Interest income related to uncertain income tax positions 1 — — — — 1 — 1 — — AFUDC — Equity 8 — 2 2 3 4 1 2 1 7 Loss on debt extinguishment (2 ) (2 ) — — — — — — — — Other 4 1 2 — — 4 2 1 1 (11 ) Other, net $ 114 $ 93 $ 4 $ 2 $ 4 $ 9 $ 3 $ 4 $ 2 $ (4 ) ____ (a) Includes investment income and realized gains and losses on sales of investments of the 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 of the Exelon 2016 Form 10-K for additional information regarding the accounting for nuclear decommissioning. The following utility taxes are included in revenues and expenses for the three months ended March 31, 2017 and 2016 . Generation’s utility tax expense represents gross receipts tax related to its retail operations, and the utility registrants' utility tax expense represents 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. Three Months Ended March 31, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 224 $ 32 $ 59 $ 31 $ 26 $ 76 $ 71 $ 5 $ — Successor Predecessor Three Months Ended March 31, 2016 March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Utility taxes $ 153 $ 28 $ 59 $ 35 $ 24 $ 79 $ 5 $ — $ 7 $ 77 Supplemental Cash Flow Information The following tables provide additional information regarding the Registrants’ Consolidated Statements of Cash Flows for the three months ended March 31, 2017 and 2016 . Three Months Ended March 31, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Depreciation, amortization and accretion Property, plant and equipment (a) $ 754 $ 289 $ 190 $ 64 $ 80 $ 112 $ 50 $ 30 $ 21 Amortization of regulatory assets (a) 128 — 18 7 48 55 32 9 14 Amortization of intangible assets, net (a) 14 13 — — — — — — — Amortization of energy contract assets and liabilities (b) 2 2 — — — — — — — Nuclear fuel (c) 264 264 — — — — — — — ARO accretion (d) 112 110 — — — — — — — Total depreciation, amortization and accretion $ 1,274 $ 678 $ 208 $ 71 $ 128 $ 167 $ 82 $ 39 $ 35 Successor Predecessor Three Months Ended March 31, 2016 March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Depreciation, amortization and accretion Property, plant and equipment (a) $ 606 $ 278 $ 170 $ 60 $ 75 $ 42 $ 27 $ 20 $ 9 $ 94 Amortization of regulatory assets (a) 65 — 19 7 34 33 12 20 5 58 Amortization of intangible assets, net (a) 14 11 — — — — — — — — Amortization of energy contract assets and liabilities (b) (14 ) (14 ) — — — — — — — — Nuclear fuel (c) 283 283 — — — — — — — — ARO accretion (d) 109 109 — — — — — — — — Total depreciation, amortization and accretion $ 1,063 $ 667 $ 189 $ 67 $ 109 $ 75 $ 39 $ 40 $ 14 $ 152 ________ (a) Included in Depreciation and amortization on the Registrants' Consolidated Statements of Operations and Comprehensive Income. (b) Included in Operating revenues or Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (d) Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Three Months Ended March 31, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 157 $ 54 $ 44 $ 7 $ 16 $ 24 $ 7 $ 3 $ 3 Loss from equity method investments 10 10 — — — — — — — Provision for uncollectible accounts 34 9 7 17 5 (4 ) (5 ) (1 ) 1 Stock-based compensation costs 31 — — — — — — — — Other decommissioning-related activity (a) (84 ) (84 ) — — — — — — — Energy-related options (b) (4 ) (4 ) — — — — — — — Amortization of regulatory asset related to debt costs 2 — 1 — — 1 — — — Amortization of rate stabilization deferral (14 ) — — — 7 (21 ) (15 ) (6 ) — Amortization of debt fair value adjustment (5 ) (3 ) — — — (2 ) — — — Discrete impacts from EIMA (c) (24 ) — (24 ) — — — — — — Amortization of debt costs 9 4 1 — — — — — — Provision for excess and obsolete inventory 2 1 1 — — — — — — Other 4 3 1 (1 ) (4 ) (6 ) (2 ) (3 ) (2 ) Total other non-cash operating activities $ 118 $ (10 ) $ 31 $ 23 $ 24 $ (8 ) $ (15 ) $ (7 ) $ 2 Non-cash investing and financing activities: Change in capital expenditures not paid $ (298 ) $ (354 ) $ 25 $ — $ 41 $ (5 ) $ (6 ) $ 9 $ — Non-cash financing of capital projects 10 10 — — — — — — — Dividends on stock compensation 2 — — — — — — — — Successor Predecessor Three Months Ended March 31, 2016 March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 136 $ 54 $ 41 $ 8 $ 16 $ 8 $ 5 $ 4 $ 3 $ 23 Loss from equity method investments 3 3 — — — — — — — — Provision for uncollectible accounts 41 6 9 16 12 5 5 7 (2 ) 16 Stock-based compensation costs 44 — — — — — — — — 3 Other decommissioning-related activity (a) (55 ) (55 ) — — — — — — — — Energy-related options (b) (9 ) (9 ) — — — — — — — — Amortization of regulatory asset related to debt costs 1 — 1 — — 1 — — — 1 Amortization of rate stabilization deferral 20 — — — 20 1 4 — — 5 Amortization of debt fair value adjustment (3 ) (3 ) — — — — — — — — Discrete impacts from EIMA (c) (14 ) — (14 ) — — — — — — — Amortization of debt costs 8 4 1 1 1 — — — — — Provision for excess and obsolete inventory 1 1 — — — 1 1 1 — 1 Merger-related commitments (d)(e) 503 3 — — — 138 100 120 358 — Severance costs 69 4 — — — — — — 52 — Asset retirement costs — — — — — — 4 2 — — Lower of cost or net realizable value inventory adjustment 36 36 — — — — — — — — Other 23 7 (6 ) (1 ) (5 ) (1 ) (1 ) (2 ) (1 ) (3 ) Total other non-cash operating activities $ 804 $ 51 $ 32 $ 24 $ 44 $ 153 $ 118 $ 132 $ 410 $ 46 Non-cash investing and financing activities: Change in capital expenditures not paid $ (290 ) $ (234 ) $ 25 $ (65 ) $ (4 ) $ 9 $ 8 $ (9 ) $ (7 ) $ 11 Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash (d)(f) — 119 — — — — — — — — Fair value of net assets distributed to Exelon in connection with the PHI Merger, net of cash (d)(f) — — — — — — — — 127 — Fair value of pension obligation transferred in connection with the PHI Merger — — — — — — — — 45 — Assumption of member purchase liability — — — — — — — — 29 — Change in PPE related to ARO update 62 62 — — — — — — — — Indemnification of like-kind exchange position (g) — — 1 — — — — — — — Non-cash financing of capital projects 31 31 — — — — — — — — Dividends on stock compensation 1 — — — — — — — — — ________ (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 of the Exelon 2016 Form 10-K 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 in Operating revenues. (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 tariff. See Note 5 — Regulatory Matters for more information. (d) See Note 4 — Mergers, Acquisitions and Dispositions for additional information related to the merger with PHI. (e) 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. (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) See Note 11 — Income Taxes for discussion of the like-kind exchange tax position. Supplemental Balance Sheet Information The following tables provide additional information about assets and liabilities of the Registrants as of March 31, 2017 and December 31, 2016 . Successor March 31, 2017 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Property, plant and equipment: Accumulated depreciation and amortization $ 19,716 (a) $ 10,801 (a) $ 4,040 $ 3,293 $ 3,311 $ 281 $ 3,090 $ 1,195 $ 1,032 Accounts receivable: Allowance for uncollectible accounts $ 346 $ 97 $ 80 $ 72 $ 35 $ 61 $ 18 $ 20 $ 23 Successor December 31, 2016 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Property, plant and equipment: Accumulated depreciation and amortization $ 19,169 (b) $ 10,562 (b) $ 3,937 $ 3,253 $ 3,254 $ 195 $ 3,050 $ 1,175 $ 1,016 Accounts receivable: Allowance for uncollectible accounts $ 334 $ 91 $ 70 $ 61 $ 32 $ 80 $ 29 $ 24 $ 27 _______ (a) Includes accumulated amortization of nuclear fuel in the reactor core of $3,171 million . (b) Includes accumulated amortization of nuclear fuel in the reactor core of $3,186 million . 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 $9 million as of March 31, 2017 and December 31, 2016 , 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 of the Exelon 2016 Form 10-K. The allowance for uncollectible accounts balance associated with these receivables at March 31, 2017 of $11 million consists of $0 million , $3 million and $8 million for low risk, medium risk and high risk segments, respectively. The allowance for uncollectible accounts balance 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 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 March 31, 2017 and December 31, 2016 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 of the Exelon 2016 Form 10-K.

Segment Information (All Regist

Segment Information (All Registrants)	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Segment Information (All Registrants)	19 . 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 three months ended March 31, 2017 and 2016 is as follows: Three Months Ended March 31, 2017 and 2016 Successor Generation (a) ComEd PECO BGE PHI (b) Other (c) Intersegment Exelon Operating revenues (d) : 2017 Competitive businesses electric revenues $ 3,720 $ — $ — $ — $ — $ — $ (328 ) $ 3,392 Competitive businesses natural gas revenues 918 — — — — — — 918 Competitive businesses other revenues 250 — — — — — — 250 Rate-regulated electric revenues — 1,298 590 667 1,097 — (8 ) 3,644 Rate-regulated natural gas revenues — — 206 284 66 — (3 ) 553 Shared service and other revenues — — — — 12 419 (431 ) — 2016 Competitive businesses electric revenues $ 3,695 $ — $ — $ — $ — $ — $ (266 ) $ 3,429 Competitive businesses natural gas revenues 822 — — — — — — 822 Competitive businesses other revenues 222 — — — — — — 222 Rate-regulated electric revenues — 1,249 644 680 90 — (6 ) 2,657 Rate-regulated natural gas revenues — — 197 249 3 — (5 ) 444 Shared service and other revenues — — — — 12 405 (418 ) (1 ) Intersegment revenues (e) : 2017 $ 328 $ 5 $ 1 $ 5 $ 12 $ 419 $ (770 ) $ — 2016 266 5 1 5 12 405 (695 ) (1 ) Net income (loss): 2017 $ 409 $ 141 $ 127 $ 125 $ 140 $ 39 $ — $ 981 2016 257 115 124 101 (309 ) (164 ) (1 ) 123 Total assets: March 31, 2017 $ 48,609 $ 28,756 $ 10,932 $ 8,821 $ 21,018 $ 10,700 $ (11,768 ) $ 117,068 December 31, 2016 46,974 28,335 10,831 8,704 21,025 10,369 (11,334 ) 114,904 _________ (a) Generation includes the six reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. Intersegment revenues for Generation for the three months ended March 31, 2017 include revenue from sales to PECO of $45 million , sales to BGE of $134 million , sales to Pepco of $83 million , sales to DPL of $51 million , and sales to ACE of $9 million in the Mid-Atlantic region, and sales to ComEd of $5 million in the Midwest region. For the three months ended March 31, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $79 million and sales to BGE of $173 million in the Mid-Atlantic region, and sales to ComEd of $5 million in the Midwest region. For the Successor period of March 24, 2016 to March 31, 2016 , intersegment revenues for Generation include revenue from sales to Pepco of $6 million , sales to DPL of $4 million , and sales to ACE of $1 million in the Mid-Atlantic region. (b) Amounts included represent activity for PHI's successor period, March 24, 2016 through March 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 three months ended March 31, 2016 . (c) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (d) 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 18 — Supplemental Financial Information for total utility taxes for the three months ended March 31, 2017 and 2016 . (e) 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. Successor and Predecessor PHI: Pepco DPL ACE Other (b) Intersegment PHI Operating revenues (a) : Three Months Ended March 31, 2017 - Successor Rate-regulated electric revenues $ 530 $ 296 $ 275 $ — $ (4 ) $ 1,097 Rate-regulated natural gas revenues — 66 — — — 66 Shared service and other revenues — — — 12 — 12 March 24, 2016 to March 31, 2016 - Successor Rate-regulated electric revenues $ 40 $ 24 $ 23 $ 3 $ — $ 90 Rate-regulated natural gas revenues — 3 — — — 3 Shared service and other revenues — — — 12 — 12 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 — — — — — — Intersegment revenues: Three Months Ended March 31, 2017 - Successor $ 1 $ 2 $ 1 $ 13 $ (5 ) $ 12 March 24, 2016 to March 31, 2016 - Successor — — — 12 — 12 January 1, 2016 to March 23, 2016 - Predecessor 1 2 1 — (4 ) — Net income (loss): Three Months Ended March 31, 2017 - Successor $ 58 $ 57 $ 28 $ (15 ) $ 12 $ 140 March 24, 2016 to March 31, 2016 - Successor (140 ) (98 ) (105 ) 22 12 (309 ) January 1, 2016 to March 23, 2016 - Predecessor 32 26 5 (44 ) — 19 Total assets: March 31, 2017 - Successor $ 7,417 $ 4,191 $ 3,451 $ 10,785 $ (4,826 ) $ 21,018 December 31, 2016 - Successor 7,335 4,153 3,457 10,804 (4,724 ) 21,025 _________ (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 18 — Supplemental Financial Information for total utility taxes for the three months ended March 31, 2017 and 2016 . (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: Three Months Ended March 31, 2017 Three Months Ended March 31, 2016 Revenues (a) Intersegment Total Revenues (a) Intersegment Total Mid-Atlantic $ 1,429 $ (4 ) $ 1,425 $ 1,532 $ (12 ) $ 1,520 Midwest 1,051 2 1,053 1,089 6 1,095 New England 549 (2 ) 547 471 (1 ) 470 New York 310 (3 ) 307 218 (15 ) 203 ERCOT 192 (1 ) 191 163 — 163 Other Power Regions 189 (5 ) 184 222 1 223 Total Revenues for Reportable Segments 3,720 (13 ) 3,707 3,695 (21 ) 3,674 Other (b) 1,168 13 1,181 1,044 21 1,065 Total Generation Consolidated Operating Revenues $ 4,888 $ — $ 4,888 $ 4,739 $ — $ 4,739 _ _________ (a) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. Includes a $3 million decrease to revenues and a $20 million increase to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the three months ended March 31, 2017 and 2016 , respectively, unrealized mark-to-market gains of $44 million and $63 million for the three months ended March 31, 2017 and 2016 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Three Months Ended March 31, 2017 Three Months Ended March 31, 2016 RNF from external customers (a) Intersegment RNF Total RNF RNF from external customers (a) Intersegment RN Total RNF Mid-Atlantic $ 755 $ 18 $ 773 $ 832 $ 9 $ 841 Midwest 704 11 715 715 3 718 New England 115 (4 ) 111 86 (5 ) 81 New York 153 — 153 141 (11 ) 130 ERCOT 94 (25 ) 69 81 (20 ) 61 Other Power Regions 108 (44 ) 64 86 (10 ) 76 Total Revenues net of purchased power and fuel expense for Reportable Segments 1,929 (44 ) 1,885 1,941 (34 ) 1,907 Other (b) 161 44 205 356 34 390 Total Generation Revenues net of purchased power and fuel expense $ 2,090 $ — $ 2,090 $ 2,297 $ — $ 2,297 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. Includes a $3 million decrease to RNF and a $19 million increase to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the three months ended March 31, 2017 and 2016 , respectively, unrealized mark-to-market losses of $49 million and gains of $103 million for the three months ended March 31, 2017 and 2016 , respectively, and the elimination of intersegment revenue net of purchased power and fuel expense.

Subsequent Events (Exelon and G

Subsequent Events (Exelon and Generation)	3 Months Ended
	Mar. 31, 2017
Subsequent Events [Abstract]
Subsequent Events [Text Block]	EGTP, a Delaware limited liability company, was formed in 2014 with the purpose of financing a portfolio of assets comprised of two combined-cycle gas turbines (CCGTs) and three peaking/simple cycle facilities consisting of approximately 3.4 GW of generation capacity in ERCOT North and Houston Zones. EGTP is an indirect wholly owned subsidiary of Exelon and Generation. Each of the aforementioned facilities is held through a wholly-owned direct subsidiary of EGTP. EGTP also owns two equity method investments in shared facility companies. EGTP, its direct parent and its wholly owned subsidiaries secure a nonrecourse senior secured term loan facility, a revolving loan facility and certain commodity and interest rate swaps. EGTP’s operating cash flows have been negatively impacted by certain market conditions including, but not limited to: low power prices, higher fuel prices and the seasonality of its cash flows. Despite the declining operating cash flows, EGTP remained in compliance with its covenants related to the project financing through March 31, 2017. On May 2, 2017, EGTP entered into a consent agreement with its lenders to permit EGTP to draw on its revolving credit facility and initiate an orderly sales process to sell the assets of its wholly-owned subsidiaries, the proceeds from which will first be used to pay the administrative costs of administering the sale, the normal and ordinary costs of operating the plants and repayment of the secured debt of EGTP, including the revolving credit facility. As a result, in the second quarter, Exelon and Generation will reclassify certain EGTP’s assets and liabilities on Exelon’s and Generation’s Consolidated Balance Sheets as held for sale at their respective fair values. Exelon and Generation estimate a pre-tax impairment charge upon reclassification ranging from $ 300 million to $400 million will be recognized in the second quarter of 2017. See Note 10 - Debt and Credit Agreements for details regarding the nonrecourse debt associated with EGTP. The resolution of this matter has no direct effect on any other Exelon or Generation debt or credit facilities.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	3 Months Ended
	Mar. 31, 2017
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 March 31, 2017 and December 31, 2016 are as follows: March 31, 2017 December 31, 2016 Successor Successor Exelon (a) Generation BGE PHI (a) ACE Exelon (a)(b) Generation BGE PHI (a) ACE Current assets $ 1,018 $ 965 $ 42 $ 11 $ 7 $ 954 $ 916 $ 23 $ 14 $ 9 Noncurrent assets 8,891 8,855 3 33 23 8,563 8,525 3 35 23 Total assets $ 9,909 $ 9,820 $ 45 $ 44 $ 30 $ 9,517 $ 9,441 $ 26 $ 49 $ 32 Current liabilities $ 871 $ 791 $ 42 38 $ 34 $ 885 $ 802 $ 42 $ 42 $ 37 Noncurrent liabilities 2,745 2,654 — 91 81 2,713 2,612 — 101 89 Total liabilities $ 3,616 $ 3,445 $ 42 $ 129 $ 115 $ 3,598 $ 3,414 $ 42 $ 143 $ 126 _______ (a) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. March 31, 2017 December 31, 2016 Successor Successor Exelon (a) Generation BGE PHI (a) ACE Exelon (a)(b) Generation BGE PHI (a) ACE Cash and cash equivalents $ 199 $ 199 $ — $ — $ — $ 150 $ 150 $ — $ — $ — Restricted cash 124 75 42 7 7 59 27 23 9 9 Accounts receivable, net Customer 347 347 — — — 371 371 — — — Other 23 23 — — — 48 48 — — — Mark-to-market derivatives assets 41 41 — — — 31 31 — — — Inventory Materials and supplies 191 191 — — — 199 199 — — — Other current assets 58 54 — 4 — 50 44 — 5 — Total current assets 983 930 42 11 7 908 870 23 14 9 Property, plant and equipment, net 5,425 5,425 — — — 5,415 5,415 — — — Nuclear decommissioning trust funds 2,286 2,286 — — — 2,185 2,185 — — — Goodwill 47 47 — — — 47 47 — — — Mark-to-market derivatives assets 57 57 — — — 23 23 — — — Other noncurrent assets 350 314 3 33 23 315 277 3 35 23 Total noncurrent assets 8,165 8,129 3 33 23 7,985 7,947 3 35 23 Total assets $ 9,148 $ 9,059 $ 45 $ 44 $ 30 $ 8,893 $ 8,817 $ 26 $ 49 $ 32 Long-term debt due within one year $ 237 $ 159 $ 41 $ 37 $ 33 $ 181 $ 99 $ 41 $ 40 $ 35 Accounts payable 275 275 — — — 269 269 — — — Accrued expenses 85 83 1 1 1 119 116 1 2 2 Mark-to-market derivative liabilities 18 18 — — — 60 60 — — — Unamortized energy contract liabilities 16 16 — — — 15 15 — — — Other current liabilities 11 11 — — — 30 30 — — — Total current liabilities 642 562 42 38 34 674 589 42 42 37 Long-term debt 626 535 — 91 81 641 540 — 101 89 Asset retirement obligations 1,929 1,929 — — — 1,904 1,904 — — — Pension obligation (c) 8 8 — — — 9 9 — — — Unamortized energy contract liabilities 18 18 — — — 22 22 — — — Other noncurrent liabilities 122 122 — — — 106 106 — — — Total noncurrent liabilities 2,703 2,612 — 91 81 2,682 2,581 — 101 89 Total liabilities $ 3,345 $ 3,174 $ 42 $ 129 $ 115 $ 3,356 $ 3,170 $ 42 $ 143 $ 126 _______ (a) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. (b) Includes certain purchase accounting adjustments not pushed down to the BGE 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 Consolidated Balance Sheets. See Note 13 - Retirement Benefits for additional details. March 31, 2017 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 647 $ 541 $ 1,188 Total liabilities (a) 73 230 303 Exelon's ownership interest in VIE (a) — 276 276 Other ownership interests in VIE (a) 574 36 610 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 279 279 Contract intangible asset 9 — 9 Debt and payment guarantees — — — Net assets pledged for Zion Station decommissioning (b) 7 — 7 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 _______ (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 $95 million and $113 million as of March 31, 2017 and December 31, 2016 , respectively; offset by payables to ZionSolutions LLC of $88 million and $104 million as of March 31, 2017 and December 31, 2016 , respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VI

Mergers, Acquisitions and Dispo

Mergers, Acquisitions and Dispositions (Tables)	3 Months Ended
	Mar. 31, 2017
Business Combinations [Abstract]
Business Acquisition, Pro Forma Information, Nonrecurring Adjustments [Table Text Block]	Three Months Ended Year Ended December 31, 2016 (a) 2016 (b) Total operating revenues $ 8,556 $ 32,342 Net income attributable to common shareholders 577 1,562 Basic earnings per share $ 0.63 $ 1.69 Diluted earnings per share 0.62 1.69 ______________ (a) The amounts above include adjustments for non-recurring costs directly related to the merger of $639 million and intercompany revenue of $170 million for the three months ended March 31, 2016 . (b) The amounts above include adjustments for non-recurring costs directly related to the merger of $680 million and intercompany revenue of $171 million for the year ended December 31, 2016 .
Business Combination, Separately Recognized Transactions [Table Text Block]	(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 DPL ACE PHI Exelon Rate credits 2016 - 2017 $ 91 $ 66 $ 101 $ 258 $ 258 Energy efficiency 2016 - 2021 — — — — 122 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 — — — — 17 Other 7 7 — 14 30 Total $ 126 $ 85 $ 111 $ 322 $ 513
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The following table summarizes the acquisition-date fair value of the consideration transferred and the assets and liabilities assumed for the FitzPatrick acquisition by Generation as of March 31, 2017 : Cash paid for purchase price $ 110 Cash paid for net cost reimbursement 129 Nuclear fuel transfer 54 Total consideration transferred $ 293 Identifiable assets acquired and liabilities assumed Current assets $ 58 Property, plant and equipment 278 Nuclear decommissioning trust funds 807 Other assets (a) 114 Total assets $ 1,257 Current liabilities $ 7 Asset retirement obligations 417 Pension and OPEB obligations 49 Deferred income taxes 144 Spent nuclear fuel obligation 110 Other liabilities 11 Total liabilities $ 738 Total net identifiable assets, at fair value $ 519 Bargain purchase gain (after-tax) $ 226 _____________ (a) Includes a $110 million asset associated with a contractual right to reimbursement from the New York Power Authority (NYPA), a prior owner of FitzPatrick, associated with the DOE one-time fee obligation. See Note 24 - Commitments and Contingencies of the Exelon 2016 Form 10- K for additional background regarding SNF obligations to the DOE. Purchase Price Allocation (a) 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 obligations 821 Other liabilities 187 Total liabilities $ 14,655 Total purchase price $ 7,142 _____________ (a) Amounts shown reflect the final purchase price allocation and the correction of a reporting error identified and corrected in the second quarter of 2016. The error had resulted in a gross up of certain assets and liabilities related to legacy PHI intercompany and income tax receivable and payable balances.
Restructuring and Related Costs	Three Months Ended March 31, Acquisition, Integration and Financing Costs (a) 2017 2016 Exelon (b) $ 9 $ 102 Generation 9 16 ComEd (c) — (8 ) PECO 1 2 BGE 2 2 Pepco 1 27 DPL (d) (7 ) 16 ACE 1 13 Successor Predecessor Acquisition, Integration and Financing Costs (a) Three Months Ended March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 PHI (d) $ (5 ) $ 56 $ 29 ______________ (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 three months ended March 31, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $9 million , incurred at ComEd that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. (d) For the three months ended March 31, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million , incurred at DPL that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. For the three months ended March 31, 2017 and 2016 , Exelon, Generation, and ComEd recorded the following severance costs (benefits) associated with these ongoing severance benefits within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income. Exelon Generation (a) ComEd (a) Three Months Ended March 31, 2017 $ 4 $ 3 $ 1 March 31, 2016 2 2 — _______ (a) The amounts above for Generation include $1 million for amounts billed by BSC through intercompany allocations for both the three months ended March 31, 2017 and 2016 . Amounts billed by BSC to ComEd were immaterial. For the three months ended March 31, 2017 and 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 Three Months Ended March 31, 2017 (a) $ (1 ) $ (1 ) $ — $ — $ — March 31, 2016 (b) $ 17 $ 12 $ 3 $ 1 $ 1 _______ (a) Amounts billed by BSC through intercompany allocations for the three months ended March 31, 2017 were immaterial. (b) 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 three months ended March 31, 2016 . For the three months ended March 31, 2017 , the PHI merger severance costs were immaterial. For the three months ended March 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 DPL ACE Three Months Ended March 31, 2016 Severance benefits (a) $ 52 $ 10 $ 2 $ 1 $ 1 $ 37 $ 18 $ 11 $ 8 ______________ (a) The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $9 million , $2 million , $1 million , $1 million , $18 million , $11 million and $8 million , respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the three months ended March 31, 2016 .
Schedule of Goodwill [Table Text Block]

Regulatory Matters (Tables)

Regulatory Matters (Tables)	3 Months Ended
	Mar. 31, 2017
Regulated Operations [Abstract]
Schedule of Regulatory Assets	Successor March 31, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory liabilities Other postretirement benefits $ 48 $ — $ — $ — $ — $ — $ — $ — Nuclear decommissioning 2,776 2,294 482 — — — — — Removal costs 1,598 1,328 — 136 134 17 117 — Deferred rent 39 — — — 39 — — — Energy efficiency and demand response programs 185 139 44 — 2 2 — — DLC program costs 8 — 8 — — — — — Electric distribution tax repairs 66 — 66 — — — — — Gas distribution tax repairs 18 — 18 — — — — — Energy and transmission programs (d)(e)(f)(g)(h)(i) 133 38 66 2 27 7 12 8 Rate stabilization deferral 3 — — 3 — — — — Other 65 4 7 20 34 3 13 17 Total regulatory liabilities 4,939 3,803 691 161 236 29 142 25 Less: current portion 637 311 161 67 82 10 47 25 Total non-current regulatory liabilities $ 4,302 $ 3,492 $ 530 $ 94 $ 154 $ 19 $ 95 $ — Successor December 31, 2016 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory assets Pension and other postretirement benefits (a) $ 4,162 $ — $ — $ — $ — $ — $ — $ — Deferred income taxes (b) 2,016 75 1,583 98 260 171 38 51 AMI programs 701 164 49 230 258 174 84 — Under-recovered distribution service costs (c) 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 (d)(e)(f)(g)(h)(i) 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 (j)(k) 25 — — 10 15 11 4 — Under-recovered revenue decoupling (l) 27 — — 3 24 21 3 — COPCO acquisition adjustment 8 — — — 8 — 8 — 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 non-current regulatory assets $ 10,046 $ 977 $ 1,681 $ 504 $ 2,851 $ 690 $ 289 $ 405 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 (d)(e)(f)(g)(h)(i) 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 non-current regulatory liabilities $ 4,187 $ 3,369 $ 517 $ 110 $ 158 $ 20 $ 97 $ — ______ (a) As of March 31, 2017 and December 31, 2016 , the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $1,087 million established at the date of the PHI Merger related to unrecognized costs that are probable of regulatory recovery. The regulatory assets are amortized over periods from 3 to 15 years, depending on the underlying component. Pepco, DPL and ACE are currently recovering these costs through base rates. Pepco, DPL and ACE are not earning a return on the recovery of these costs in base rates. (b) As of March 31, 2017 , includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $ 22 million , $39 million , $31 million , $21 million and $20 million for ComEd, BGE, Pepco, DPL and ACE, respectively. As of December 31, 2016 , includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $ 22 million , $ 38 million , $31 million , $20 million and $19 million for ComEd, BGE, Pepco, DPL and ACE, respectively. (c) As of March 31, 2017 , ComEd’s regulatory asset of $211 million was comprised of $158 million for the 2015 - 2017 annual reconciliations and $53 million related to significant one-time events including $17 million of deferred storm costs, $10 million of Constellation and PHI merger and integration related costs and $26 million of smart meter related costs. As of December 31, 2016 , ComEd’s regulatory asset of $188 million was comprised of $134 million for the 2015 and 2016 annual reconciliations and $54 million related to significant one-time events, including $20 million of deferred storm costs and $11 million of Constellation and PHI merger and integration related costs, and $23 million of smart meter related costs. ComEd's 2015 annual reconciliation regulatory asset included a reduction of $8 million related to a ComEd-proposed refund to customers for the impact of changing its OSHA recordable rate for 2014 and 2015. See Note 4 — Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information. (d) As of March 31, 2017 , ComEd’s regulatory asset of $18 million included $10 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of March 31, 2017 , ComEd’s regulatory liability of $38 million included $6 million related to over-recovered energy costs and $32 million associated with revenues received for renewable energy requirements. As of December 31, 2016 , ComEd’s regulatory asset of $23 million included $15 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2016 , ComEd’s regulatory liability of $60 million included $30 million related to over-recovered energy costs and $30 million associated with revenues received for renewable energy requirements. (e) As of March 31, 2017 , PECO's regulatory liability of $66 million included $41 million related to over-recovered costs under the DSP program, $13 million related to the over-recovered natural gas costs under the PGC, $10 million related to over-recovered non-bypassable transmission service charges and $2 million related to over-recovered electric transmission costs. As of December 31, 2016 , PECO's regulatory liability of $56 million included $34 million related to over-recovered costs under the DSP program, $10 million related to over-recovered non-bypassable transmission service charges, $8 million related to the over-recovered natural gas costs under the PGC and $4 million related to the over-recovered electric transmission costs. (f) As of March 31, 2017 , BGE's regulatory asset of $19 million included $3 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $13 million related to under-recovered electric energy costs, and $3 million of abandonment costs to be recovered upon FERC approval. As of March 31, 2017 , BGE's regulatory liability consisted of $2 million related to over-recovered natural gas costs. As of December 31, 2016 , BGE’s regulatory asset of $38 million included $4 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $28 million related to under-recovered electric energy costs, $3 million of abandonment costs to be recovered upon FERC approval, and $3 million of under-recovered natural gas costs. (g) As of March 31, 2017 , Pepco's regulatory asset of $6 million included $2 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of March 31, 2017 , Pepco's regulatory liability of $7 million included $2 million of over-recovered transmission costs and $5 million of over-recovered electric energy costs. As of December 31, 2016 , Pepco's regulatory asset of $6 million related to under-recovered electric energy costs. As of December 31, 2016 , Pepco's regulatory liability of $8 million included $ 5 million of over-recovered transmission costs and $3 million of over-recovered electric energy costs. (h) As of March 31, 2017 , DPL's regulatory asset of $5 million related to under-recovered electric energy costs. As of March 31, 2017 , DPL's regulatory liability of $12 million included $9 million of over-recovered electric energy costs, $1 million of over-recovered transmission costs, and $2 million of over-recovered gas cost. As of December 31, 2016 , DPL's regulatory asset of $5 million included $1 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of December 31, 2016 , DPL's regulatory liability of $5 million included $2 million of over-recovered electric energy costs and $3 million of over-recovered transmission costs. (i) As of March 31, 2017 , ACE's regulatory asset of $23 million included $10 million of transmission costs recoverable through its FERC approved formula rate and $13 million of under-recovered electric energy costs. As of March 31, 2017 , ACE's regulatory liability of $8 million included $2 million of over-recovered transmission costs and $6 million of over-recovered electric energy costs. As of December 31, 2016 , ACE's regulatory asset of $17 million included $6 million of transmission costs recoverable through its FERC approved formula rate and $11 million of under-recovered electric energy costs. As of December 31, 2016 , ACE's regulatory liability of $5 million included $4 million of over-recovered transmission costs and $1 million of over-recovered electric energy costs. (j) As of March 31, 2017 , BGE's regulatory asset of $8 million included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order. (k) As of March 31, 2017 and December 31, 2016 , Pepco’s regulatory asset of $11 million represents previously incurred PHI acquisition costs authorized for recovery by the November 2016 Maryland distribution rate case order. As of March 31, 2017 , DPL’s regulatory asset of $13 million represents previously incurred PHI acquisition costs, including $5 million authorized for recovery by the February 2017 Maryland distribution rate case order and $8 million expected to be recovered in electric and gas distribution rates in the Delaware service territory. As of December 31, 2016 , DPL's regulatory asset of $4 million represents previously incurred PHI acquisition costs expected to be recovered in distribution rates in the Maryland service territory. (l) Represents the electric and natural gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of March 31, 2017 , BGE had a regulatory asset of $25 million related to under-recovered electric revenue decoupling and $6 million related to under-recovered natural gas revenue decoupling. As of December 31, 2016 , BGE had a regulatory asset of $2 million related to under-recovered natural gas revenue decoupling and $1 million related to under-recovered electric revenue decoupling.
Schedule of Regulatory Liabilities	Successor March 31, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory liabilities Other postretirement benefits $ 48 $ — $ — $ — $ — $ — $ — $ — Nuclear decommissioning 2,776 2,294 482 — — — — — Removal costs 1,598 1,328 — 136 134 17 117 — Deferred rent 39 — — — 39 — — — Energy efficiency and demand response programs 185 139 44 — 2 2 — — DLC program costs 8 — 8 — — — — — Electric distribution tax repairs 66 — 66 — — — — — Gas distribution tax repairs 18 — 18 — — — — — Energy and transmission programs (d)(e)(f)(g)(h)(i) 133 38 66 2 27 7 12 8 Rate stabilization deferral 3 — — 3 — — — — Other 65 4 7 20 34 3 13 17 Total regulatory liabilities 4,939 3,803 691 161 236 29 142 25 Less: current portion 637 311 161 67 82 10 47 25 Total non-current regulatory liabilities $ 4,302 $ 3,492 $ 530 $ 94 $ 154 $ 19 $ 95 $ — Successor December 31, 2016 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory assets Pension and other postretirement benefits (a) $ 4,162 $ — $ — $ — $ — $ — $ — $ — Deferred income taxes (b) 2,016 75 1,583 98 260 171 38 51 AMI programs 701 164 49 230 258 174 84 — Under-recovered distribution service costs (c) 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 (d)(e)(f)(g)(h)(i) 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 (j)(k) 25 — — 10 15 11 4 — Under-recovered revenue decoupling (l) 27 — — 3 24 21 3 — COPCO acquisition adjustment 8 — — — 8 — 8 — 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 non-current regulatory assets $ 10,046 $ 977 $ 1,681 $ 504 $ 2,851 $ 690 $ 289 $ 405 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 (d)(e)(f)(g)(h)(i) 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 non-current regulatory liabilities $ 4,187 $ 3,369 $ 517 $ 110 $ 158 $ 20 $ 97 $ — ______ (a) As of March 31, 2017 and December 31, 2016 , the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $1,087 million established at the date of the PHI Merger related to unrecognized costs that are probable of regulatory recovery. The regulatory assets are amortized over periods from 3 to 15 years, depending on the underlying component. Pepco, DPL and ACE are currently recovering these costs through base rates. Pepco, DPL and ACE are not earning a return on the recovery of these costs in base rates. (b) As of March 31, 2017 , includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $ 22 million , $39 million , $31 million , $21 million and $20 million for ComEd, BGE, Pepco, DPL and ACE, respectively. As of December 31, 2016 , includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $ 22 million , $ 38 million , $31 million , $20 million and $19 million for ComEd, BGE, Pepco, DPL and ACE, respectively. (c) As of March 31, 2017 , ComEd’s regulatory asset of $211 million was comprised of $158 million for the 2015 - 2017 annual reconciliations and $53 million related to significant one-time events including $17 million of deferred storm costs, $10 million of Constellation and PHI merger and integration related costs and $26 million of smart meter related costs. As of December 31, 2016 , ComEd’s regulatory asset of $188 million was comprised of $134 million for the 2015 and 2016 annual reconciliations and $54 million related to significant one-time events, including $20 million of deferred storm costs and $11 million of Constellation and PHI merger and integration related costs, and $23 million of smart meter related costs. ComEd's 2015 annual reconciliation regulatory asset included a reduction of $8 million related to a ComEd-proposed refund to customers for the impact of changing its OSHA recordable rate for 2014 and 2015. See Note 4 — Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information. (d) As of March 31, 2017 , ComEd’s regulatory asset of $18 million included $10 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of March 31, 2017 , ComEd’s regulatory liability of $38 million included $6 million related to over-recovered energy costs and $32 million associated with revenues received for renewable energy requirements. As of December 31, 2016 , ComEd’s regulatory asset of $23 million included $15 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2016 , ComEd’s regulatory liability of $60 million included $30 million related to over-recovered energy costs and $30 million associated with revenues received for renewable energy requirements. (e) As of March 31, 2017 , PECO's regulatory liability of $66 million included $41 million related to over-recovered costs under the DSP program, $13 million related to the over-recovered natural gas costs under the PGC, $10 million related to over-recovered non-bypassable transmission service charges and $2 million related to over-recovered electric transmission costs. As of December 31, 2016 , PECO's regulatory liability of $56 million included $34 million related to over-recovered costs under the DSP program, $10 million related to over-recovered non-bypassable transmission service charges, $8 million related to the over-recovered natural gas costs under the PGC and $4 million related to the over-recovered electric transmission costs. (f) As of March 31, 2017 , BGE's regulatory asset of $19 million included $3 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $13 million related to under-recovered electric energy costs, and $3 million of abandonment costs to be recovered upon FERC approval. As of March 31, 2017 , BGE's regulatory liability consisted of $2 million related to over-recovered natural gas costs. As of December 31, 2016 , BGE’s regulatory asset of $38 million included $4 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $28 million related to under-recovered electric energy costs, $3 million of abandonment costs to be recovered upon FERC approval, and $3 million of under-recovered natural gas costs. (g) As of March 31, 2017 , Pepco's regulatory asset of $6 million included $2 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of March 31, 2017 , Pepco's regulatory liability of $7 million included $2 million of over-recovered transmission costs and $5 million of over-recovered electric energy costs. As of December 31, 2016 , Pepco's regulatory asset of $6 million related to under-recovered electric energy costs. As of December 31, 2016 , Pepco's regulatory liability of $8 million included $ 5 million of over-recovered transmission costs and $3 million of over-recovered electric energy costs. (h) As of March 31, 2017 , DPL's regulatory asset of $5 million related to under-recovered electric energy costs. As of March 31, 2017 , DPL's regulatory liability of $12 million included $9 million of over-recovered electric energy costs, $1 million of over-recovered transmission costs, and $2 million of over-recovered gas cost. As of December 31, 2016 , DPL's regulatory asset of $5 million included $1 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of December 31, 2016 , DPL's regulatory liability of $5 million included $2 million of over-recovered electric energy costs and $3 million of over-recovered transmission costs. (i) As of March 31, 2017 , ACE's regulatory asset of $23 million included $10 million of transmission costs recoverable through its FERC approved formula rate and $13 million of under-recovered electric energy costs. As of March 31, 2017 , ACE's regulatory liability of $8 million included $2 million of over-recovered transmission costs and $6 million of over-recovered electric energy costs. As of December 31, 2016 , ACE's regulatory asset of $17 million included $6 million of transmission costs recoverable through its FERC approved formula rate and $11 million of under-recovered electric energy costs. As of December 31, 2016 , ACE's regulatory liability of $5 million included $4 million of over-recovered transmission costs and $1 million of over-recovered electric energy costs. (j) As of March 31, 2017 , BGE's regulatory asset of $8 million included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order. (k) As of March 31, 2017 and December 31, 2016 , Pepco’s regulatory asset of $11 million represents previously incurred PHI acquisition costs authorized for recovery by the November 2016 Maryland distribution rate case order. As of March 31, 2017 , DPL’s regulatory asset of $13 million represents previously incurred PHI acquisition costs, including $5 million authorized for recovery by the February 2017 Maryland distribution rate case order and $8 million expected to be recovered in electric and gas distribution rates in the Delaware service territory. As of December 31, 2016 , DPL's regulatory asset of $4 million represents previously incurred PHI acquisition costs expected to be recovered in distribution rates in the Maryland service territory. (l) Represents the electric and natural gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of March 31, 2017 , BGE had a regulatory asset of $25 million related to under-recovered electric revenue decoupling and $6 million related to under-recovered natural gas revenue decoupling. As of December 31, 2016 , BGE had a regulatory asset of $2 million related to under-recovered natural gas revenue decoupling and $1 million related to under-recovered electric revenue decoupling.
Purchase Of Receivables	Successor As of December 31, 2016 Exelon ComEd PECO BGE PHI Pepco DPL ACE Purchased receivables (b) $ 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 _______ (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. (b) Pepco's electric POR program in Maryland included a discount on purchased receivables ranging from 0% to 2% depending on customer class, and Pepco's electric POR program in the District of Columbia included a discount on purchased receivables ranging from 0% to 6% depending on customer class. DPL's electric POR program in Maryland included a discount on purchased receivables ranging from 0% to 1% depending on customer class.
Public Utilities General Disclosures [Table Text Block]	he following total increases/(decreases) were included in ComEd’s and BGE’s electric transmission formula rate filings: 2017 Annual Transmission Filings (a) ComEd BGE Initial revenue requirement increase $ 44 $ 31 Annual reconciliation (decrease) increase (33 ) 3 Dedicated facilities decrease (b) — (8 ) Total revenue requirement increase $ 11 $ 26 Allowed return on rate base (c) 8.43 % 7.47 % Allowed ROE (d) 11.50 % 10.50 % _____________ (a) All rates are effective June 2017, subject to review by the FERC and other parties, which is due by fourth quarter 2017. (b) 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. (c) Represents the weighted average debt and equity return on transmission rate bases. (d) As part of the FERC-approved settlement of ComEd’s 2007 transmission rate case, the rate of return on common equity is 11.50% and the common equity component of the ratio used to calculate the weighted average debt and equity return for the transmission formula rate is currently capped at 55%. As part of the FERC-approved settlement of the ROE complaint against BGE, the rate of return on common equity is 10.50% , inclusive of a 50 basis point incentive adder for being a member of a re Exelon ComEd (a) PECO BGE (b) PHI Pepco (c) DPL (c) ACE March 31, 2017 $ 71 $ 5 $ — $ 56 $ 10 $ 6 $ 4 $ — Exelon ComEd (a) PECO BGE (b) PHI Pepco (b) DPL (b) ACE December 31, 2016 $ 72 $ 5 $ — $ 57 $ 10 $ 6 $ 4 $ — _________________________ (a) Reflects ComEd's unrecognized equity returns earned for ratemaking purposes on its under-recovered distribution services costs regulatory assets. (b) BGE's authorized amounts capitalized for ratemaking purposes related to earnings on shareholders' investment on its AMI Programs.

Early Nuclear Plant Retiremen30

Early Nuclear Plant Retirements Early Nuclear Plant Retirements (Tables)	3 Months Ended
	Mar. 31, 2017
Property, Plant and Equipment [Abstract]
ImplicationsofPotentialEarlyPlantRetirement [Table Text Block]	(in millions) TMI Asset Balances Materials and supplies inventory $ 40 Nuclear fuel inventory, net 72 Completed plant, net 1,000 Construction work in progress 40 Liability Balances Asset retirement obligation (572 ) NRC License Renewal Term 2034
Schedule of Other Operating Cost and Expense, by Component [Table Text Block]	Exelon's and Generation's 2016 results included a net incremental $714 million of total 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) Q2 2016 Q3 2016 Q4 2016 YTD 2016 Depreciation and amortization Accelerated depreciation (a) $ 115 $ 344 $ 253 $ 712 Accelerated Nuclear Fuel amortization 9 28 23 60 Operating and maintenance One time charges (b) 141 5 (120 ) 26 ARO accretion, net of contractual offset (c) — 2 — 2 Contractual offset for ARC depreciation (c) (14 ) (41 ) (31 ) (86 ) Total $ 251 $ 338 $ 125 $ 714 _____________ (a) Reflected incremental accelerated depreciation of plant assets, including any ARC, for the period June 2, 2016, through December 6, 2016. (b) Primarily included materials and supplies inventory reserve adjustments, employee related costs and construction work-in-progress (CWIP) impairments. (c) 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.

Fair Value of Financial Asset31

Fair Value of Financial Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value Tables [Line Items]
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 March 31, 2017 and December 31, 2016 : Exelon March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 2,048 $ — $ 2,048 $ — $ 2,048 Long-term debt (including amounts due within one year) (a) 34,689 1,135 32,562 1,962 35,659 Long-term debt to financing trusts (b) 641 — — 677 677 SNF obligation 1,136 — 813 — 813 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 Generation March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 717 $ — $ 717 $ — $ 717 Long-term debt (including amounts due within one year) (a) 9,979 — 8,200 1,671 9,871 SNF obligation 1,136 — 813 — 813 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 ComEd March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 365 $ — $ 365 $ — $ 365 Long-term debt (including amounts due within one year) (a) 7,035 — 7,615 — 7,615 Long-term debt to financing trusts (b) 205 — — 218 218 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 PECO March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,580 $ — $ 2,806 $ — $ 2,806 Long-term debt to financing trusts 184 — — 193 193 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 BGE March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 95 $ — $ 95 $ — $ 95 Long-term debt (including amounts due within one year) (a) 2,323 — 2,501 — 2,501 Long-term debt to financing trusts (b) 252 — — 266 266 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 PHI (Successor) March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 167 $ — $ 167 $ — $ 167 Long-term debt (including amounts due within one year) (a) 5,860 — 5,510 291 5,801 December 31, 2016 Carrying Amount Fair Value 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 Pepco March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 167 $ — $ 167 $ — $ 167 Long-term debt (including amounts due within one year) (a) 2,350 — 2,804 9 2,813 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 DPL March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 1,326 $ — $ 1,374 $ — $ 1,374 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 ACE March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 1,145 $ — $ 989 $ 282 $ 1,271 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 ________ (a) Includes unamortized debt issuance costs which are not fair valued of $199 million , $67 million , $45 million , $15 million , $14 million , $2 million , $29 million , $11 million , and $5 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of March 31, 2017 . Includes unamortized debt issuance costs 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 . (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 March 31, 2017 and December 31, 2016 .
Assets and liabilities measured and recorded at fair value on recurring basis	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 March 31, 2017 and December 31, 2016 : Generation Exelon As of March 31, 2017 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) $ 135 $ — $ — $ — $ 135 $ 342 $ — $ — $ — $ 342 NDT fund investments Cash equivalents (b) 160 21 — — 181 160 21 — — 181 Equities 4,113 505 1 2,089 6,708 4,113 505 1 2,089 6,708 Fixed income Corporate debt — 1,749 255 — 2,004 — 1,749 255 — 2,004 U.S. Treasury and agencies 1,516 35 — — 1,551 1,516 35 — — 1,551 Foreign governments — 57 — — 57 — 57 — — 57 State and municipal debt — 241 — — 241 — 241 — — 241 Other (c) — 52 — 484 536 — 52 — 484 536 Fixed income subtotal 1,516 2,134 255 484 4,389 1,516 2,134 255 484 4,389 Middle market lending — — 427 64 491 — — 427 64 491 Private equity — — — 158 158 — — — 158 158 Real estate — — — 427 427 — — — 427 427 NDT fund investments subtotal (d) 5,789 2,660 683 3,222 12,354 5,789 2,660 683 3,222 12,354 Pledged assets for Zion Station decommissioning Cash equivalents 21 — — — 21 21 — — — 21 Equities — 1 — — 1 — 1 — — 1 Fixed income - U.S. Treasury and agencies 8 1 — — 9 8 1 — — 9 Generation Exelon As of March 31, 2017 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Middle market lending — — 20 44 64 — — 20 44 64 Pledged assets for Zion Station (e) 29 2 20 44 95 29 2 20 44 95 Rabbi trust investments Cash equivalents 7 — — — 7 80 — — — 80 Mutual funds 20 — — — 20 53 — — — 53 Fixed income — — — — — — 15 — — 15 Life insurance contracts — 20 — — 20 — 66 20 — 86 Rabbi trust investments subtotal 27 20 — — 47 133 81 20 — 234 Commodity derivative assets Economic hedges 749 2,993 1,631 — 5,373 751 2,993 1,631 — 5,375 Proprietary trading 5 50 25 — 80 5 50 25 — 80 Effect of netting and allocation of collateral (f) (g) (639 ) (2,575 ) (873 ) — (4,087 ) (641 ) (2,575 ) (873 ) — (4,089 ) Commodity derivative assets subtotal 115 468 783 — 1,366 115 468 783 — 1,366 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 12 — — 12 Economic hedges — 22 — — 22 — 22 — — 22 Proprietary trading 3 1 — — 4 3 1 — — 4 Effect of netting and allocation of collateral (4 ) (14 ) — — (18 ) (4 ) (14 ) — — (18 ) Interest rate and foreign currency derivative assets subtotal (1 ) 9 — — 8 (1 ) 21 — — 20 Other investments — — 40 — 40 — — 40 — 40 Total assets 6,094 3,159 1,526 3,266 14,045 6,407 3,232 1,546 3,266 14,451 Liabilities Commodity derivative liabilities Economic hedges (787 ) (2,855 ) (1,167 ) — (4,809 ) (787 ) (2,855 ) (1,449 ) — (5,091 ) Proprietary trading (6 ) (49 ) (22 ) — (77 ) (6 ) (49 ) (22 ) — (77 ) Effect of netting and allocation of collateral (f) (g) 714 2,846 971 — 4,531 714 2,846 971 — 4,531 Commodity derivative liabilities subtotal (79 ) (58 ) (218 ) — (355 ) (79 ) (58 ) (500 ) — (637 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (1 ) — — (1 ) — (1 ) — — (1 ) Economic hedges — (25 ) — — (25 ) — (25 ) — — (25 ) Proprietary trading (3 ) — — — (3 ) (3 ) — — — (3 ) Effect of netting and allocation of collateral 4 14 — — 18 4 14 — — 18 Interest rate and foreign currency derivative liabilities subtotal 1 (12 ) — — (11 ) 1 (12 ) — — (11 ) Deferred compensation obligation — (35 ) — — (35 ) — (135 ) — — (135 ) Total liabilities (78 ) (105 ) (218 ) — (401 ) (78 ) (205 ) (500 ) — (783 ) Total net assets $ 6,016 $ 3,054 $ 1,308 $ 3,266 $ 13,644 $ 6,329 $ 3,027 $ 1,046 $ 3,266 $ 13,668 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 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) (g) (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 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 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) (g) 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 ________ (a) Generation excludes cash of $267 million and $252 million at March 31, 2017 and December 31, 2016 and restricted cash of $138 million and $157 million at March 31, 2017 and December 31, 2016 . Exelon excludes cash of $381 million and $360 million at March 31, 2017 and December 31, 2016 and restricted cash of $165 million and $180 million at March 31, 2017 and December 31, 2016 and includes long term restricted cash of $25 million at March 31, 2017 and December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) Includes less than $1 million and $29 million of cash received from outstanding repurchase agreements at March 31, 2017 and December 31, 2016 , respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (d) below. (c) Includes derivative instruments of $(1) million and $(2) million , which have a total notional amount of $886 million and $933 million at March 31, 2017 and December 31, 2016 , 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 assets (liabilities) of $8 million and $(31) million at March 31, 2017 and December 31, 2016 , 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 at March 31, 2017 and December 31, 2016 . These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (f) Collateral posted/(received) from counterparties totaled $75 million , $271 million and $98 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of March 31, 2017 . Collateral posted/(received) from counterparties, net of collateral paid to 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 . (g) Of the collateral posted/(received), $14 million represents variation margin on the exchanges as of March 31, 2017 . Of the collateral posted/(received), $(158) million represents variation margin on the exchanges as of December 31, 2016 . 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 March 31, 2017 and December 31, 2016 : ComEd PECO BGE As of March 31, 2017 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) $ — $ — $ — $ — $ 5 $ — $ — $ 5 $ 45 $ — $ — $ 45 Rabbi trust investments Mutual funds — — — — 7 — — 7 5 — — 5 Life insurance contracts — — — — — 10 — 10 — — — — Rabbi trust investments subtotal — — — — 7 10 — 17 5 — — 5 Total assets — — — — 12 10 — 22 50 — — 50 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (11 ) — (11 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (282 ) (282 ) — — — — — — — — Total liabilities — (8 ) (282 ) (290 ) — (11 ) — (11 ) — (4 ) — (4 ) Total net assets (liabilities) $ — $ (8 ) $ (282 ) $ (290 ) $ 12 $ (1 ) $ — $ 11 $ 50 $ (4 ) $ — $ 46 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 _________ (a) ComEd excludes cash of $31 million and $36 million at March 31, 2017 and December 31, 2016 and restricted cash of $3 million and $2 million at March 31, 2017 and December 31, 2016 . PECO excludes cash of $27 million and $22 million at March 31, 2017 and December 31, 2016 . BGE excludes cash of $11 million and $13 million at March 31, 2017 and December 31, 2016 and includes long term restricted cash of $2 million at March 31, 2017 and 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 $263 million , respectively, at March 31, 2017 , and $19 million and $239 million , respectively, at December 31, 2016 , 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 March 31, 2017 and December 31, 2016 : Successor Successor As of March 31, 2017 As of December 31, 2016 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 154 $ — $ — $ 154 $ 217 $ — $ — $ 217 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 74 — — 74 73 — — 73 Fixed income — 15 — 15 — 16 — 16 Life insurance contracts — 23 20 43 — 22 20 42 Rabbi trust investments subtotal 74 38 20 132 73 38 20 131 Total assets 228 38 20 286 290 38 20 348 Liabilities Deferred compensation obligation — (25 ) — (25 ) — (28 ) — (28 ) Total liabilities — (25 ) — (25 ) — (28 ) — (28 ) Total net assets $ 228 $ 13 $ 20 $ 261 $ 290 $ 10 $ 20 $ 320 Pepco DPL ACE As of March 31, 2017 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 $ 39 $ — $ — $ 39 $ 80 $ — $ — $ 80 Rabbi trust investments Cash equivalents 43 — — 43 1 — — 1 — — — — Fixed income — 15 — 15 — — — — — — — — Life insurance contracts — 23 20 43 — — — — — — — — Rabbi trust investments subtotal 43 38 20 101 1 — — 1 — — — — Total assets 76 38 20 134 40 — — 40 80 — — 80 Liabilities Deferred compensation obligation — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total liabilities — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 76 $ 34 $ 20 $ 130 $ 40 $ (1 ) $ — $ 39 $ 80 $ — $ — $ 80 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 _______ (a) PHI excludes cash of $19 million and $19 million at March 31, 2017 and December 31, 2016 and includes long term restricted cash of $23 million and $23 million at March 31, 2017 and December 31, 2016 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $8 million and $9 million at March 31, 2017 and December 31, 2016 . DPL excludes cash of $5 million and $4 million at March 31, 2017 and December 31, 2016 . ACE excludes cash of $4 million and $3 million at March 31, 2017 and December 31, 2016 and includes long term restricted cash of $23 million and $23 million at March 31, 2017 and December 31, 2016 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.
Fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis	The following tables present the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis during the three months ended March 31, 2017 and 2016 : Successor Generation ComEd PHI Exelon Three Months Ended March 31, 2017 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives (a) Life Insurance Contracts Eliminated in Consolidation Total Balance as of December 31, 2016 $ 677 $ 19 $ 493 $ 42 $ 1,231 $ (258 ) $ 20 $ — $ 993 Total realized / unrealized gains (losses) Included in net income 3 — (43 ) (b) 1 (39 ) — 1 — (38 ) Included in noncurrent payables to affiliates 9 — — — 9 — — (9 ) — Included in regulatory assets/liabilities — — — — — (24 ) — 9 (15 ) Change in collateral — — 38 — 38 — — — 38 Purchases, sales, issuances and settlements Purchases 17 1 69 2 89 — — — 89 Sales — — (2 ) — (2 ) — — — (2 ) Issuances — — — — — — (1 ) — (1 ) Settlements (23 ) — — — (23 ) — — — (23 ) Transfers into Level 3 — — (1 ) — (1 ) — — — (1 ) Transfers out of Level 3 — — 11 (5 ) 6 — — — 6 Balance as of March 31, 2017 $ 683 $ 20 $ 565 $ 40 $ 1,308 $ (282 ) $ 20 $ — $ 1,046 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2017 $ 2 $ — $ 59 $ — $ 61 $ — $ 1 $ — $ 62 ___________________ (a) Includes $ 30 million of decreases in fair value and an increase for realized losses due to settlements of $ 6 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 2017 . (b) Includes a reduction for the reclassification of $102 million of realized gains due to the settlement of derivative contracts for the three months ended March 31, 2017 . Successor Generation ComEd PHI (c) Exelon Three Months Ended March 31, 2016 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives (a) Life Insurance Contracts Eliminated in Consolidation Total Balance as of December 31, 2015 $ 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 2 — (6 ) (b) — (4 ) — — — (4 ) Included in noncurrent payables to affiliates 4 — — — 4 — — (4 ) — Included in payable for Zion Station decommissioning — 2 — — 2 — — — 2 Included in regulatory assets — — — — — (18 ) — 4 (14 ) Change in collateral — — (50 ) — (50 ) — — — (50 ) Purchases, sales, issuances and settlements Purchases 34 1 59 3 97 — — — 97 Sales — — (2 ) — (2 ) — — — (2 ) Settlements (26 ) — — — (26 ) — — — (26 ) Transfers into Level 3 — — 2 — 2 — — — 2 Transfers out of Level 3 — — (7 ) — (7 ) — — — (7 ) Balance as of March 31, 2016 $ 684 $ 25 $ 1,047 $ 36 $ 1,792 $ (265 ) $ 20 $ — $ 1,547 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2016 $ 1 $ — $ 219 $ — $ 220 $ — $ — $ — $ 220 _________ (a) Includes $25 million of decreases in fair value and an increase for realized losses due to settlements of $7 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 2016 . (b) Includes a reduction for the reclassification of $225 million of realized gains due to the settlement of derivative contracts recorded in results of operations for the three months ended March 31, 2016 . (c) Successor period represents activity from March 24, 2016 through March 31, 2016 . See tables below for PHI's predecessor periods, as well as activity for Pepco for the three months ended March 31, 2017 and 2016 . Predecessor January 1, 2016 to March 23, 2016 PHI Preferred Stock Life Insurance Contracts Beginning Balance $ 18 $ 19 Total realized / unrealized gains (losses) Included in net income (18 ) 1 Ending Balance $ — $ 20 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities for the period $ — $ 1 Life Insurance Contracts Three Months Ended March 31, Pepco 2017 2016 Beginning Balance $ 20 $ 19 Total realized / unrealized gains (losses) Included in net income 1 1 Purchases, sales, issuances and settlements Issuances (1 ) — Ending Balance $ 20 $ 20 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities for the period $ 1 $ 1
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 three months ended March 31, 2017 and 2016 : Successor Generation PHI Exelon Operating Purchased Other, net (a) Other, net (a) Operating Purchased Other, net (a) Total gains (losses) included in net income for the three months ended March 31, 2017 88 (131 ) 3 1 88 (131 ) 4 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended March 31, 2017 140 (81 ) 2 1 140 (81 ) 3 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 three months ended March 31, 2016 49 (55 ) 2 49 (55 ) 2 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended March 31, 2016 254 (35 ) 1 254 (35 ) 1 Predecessor PHI Pepco January 1, 2016 to March 23, 2016 Three Months Ended March 31, 2017 Three Months Ended March 31, 2016 Other, net Total gains (losses) included in net income $ (17 ) $ 1 $ 1 Change in the unrealized gains (losses) relating to assets and liabilities held 1 1 1 _________ (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 PHI and Pepco.
Fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis, valuation technique	isk. The table below discloses the significant inputs to the forward curve used to value these positions. Type of trade Fair Value at March 31, 2017 Valuation Technique Unobservable Input Range Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(c) $ 464 Discounted Forward power $8 - $130 Forward gas $1.92 - $9.87 Option Model Volatility 13% - 112% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(c) $ 3 Discounted Forward power $15 - $67 Mark-to-market derivatives (Exelon and ComEd) $ (282 ) Discounted Forward heat (b) 8x - 9x Marketability 3% - 8% Renewable 88% - 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 $98 million as of March 31, 2017 . 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 Forward power price $11 - $130 Forward gas price $1.72 - $9.2 Option Model Volatility percentage 8% - 173% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(c) $ (3 ) Discounted Forward power price $19 - $79 Mark-to-market derivatives (Exelon and ComEd) $ (258 ) Discounted Cash Flow Forward heat (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
Exelon Generation Co L L C [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	Generation March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 717 $ — $ 717 $ — $ 717 Long-term debt (including amounts due within one year) (a) 9,979 — 8,200 1,671 9,871 SNF obligation 1,136 — 813 — 813 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
Commonwealth Edison Co [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	ComEd March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 365 $ — $ 365 $ — $ 365 Long-term debt (including amounts due within one year) (a) 7,035 — 7,615 — 7,615 Long-term debt to financing trusts (b) 205 — — 218 218 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
PECO Energy Co [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	PECO March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,580 $ — $ 2,806 $ — $ 2,806 Long-term debt to financing trusts 184 — — 193 193 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
Baltimore Gas and Electric Company [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	BGE March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 95 $ — $ 95 $ — $ 95 Long-term debt (including amounts due within one year) (a) 2,323 — 2,501 — 2,501 Long-term debt to financing trusts (b) 252 — — 266 266 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
PEPCO Holdings Inc [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	PHI (Successor) March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 167 $ — $ 167 $ — $ 167 Long-term debt (including amounts due within one year) (a) 5,860 — 5,510 291 5,801 December 31, 2016 Carrying Amount Fair Value 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
Potomac Electric Power Company [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	Pepco March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 167 $ — $ 167 $ — $ 167 Long-term debt (including amounts due within one year) (a) 2,350 — 2,804 9 2,813 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
Delmarva Power and Light Company [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	DPL March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 1,326 $ — $ 1,374 $ — $ 1,374 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
Atlantic City Electric Company [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	ACE March 31, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 1,145 $ — $ 989 $ 282 $ 1,271 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

Derivative Financial Instrume32

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of the derivative fair value	Generation Exelon Corporate Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary Trading (a) Collateral and Netting (b) Subtotal Derivatives Designated as Hedging Instruments Total Mark-to-market derivative assets (current assets) $ — $ 15 $ 3 $ (13 ) $ 5 $ — $ 5 Mark-to-market derivative assets (noncurrent assets) — 7 1 (5 ) 3 12 15 Total mark-to-market derivative assets — 22 4 (18 ) 8 12 20 Mark-to-market derivative liabilities (current liabilities) (1 ) (17 ) (2 ) 13 (7 ) — (7 ) Mark-to-market derivative liabilities (noncurrent liabilities) — (8 ) (1 ) 5 (4 ) — (4 ) Total mark-to-market derivative liabilities (1 ) (25 ) (3 ) 18 (11 ) — (11 ) Total mark-to-market derivative net assets (liabilities) $ (1 ) $ (3 ) $ 1 $ — $ (3 ) $ 12 $ 9 _________ (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 counterparty 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, 2016 : Generation Exelon Corporate Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary Trading (a) Collateral and Netting (b) Subtotal Derivatives Designated as Hedging Instruments 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 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: Three Months Ended March 31, Income Statement Location 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on Borrowings Exelon Interest expense $ (4 ) $ 17 $ 8 $ (15 ) The following table provides a summary of the derivative fair value balances recorded by the Registrants as of March 31, 2017 : Successor Generation ComEd DPL PHI Exelon Derivatives Economic Hedges Proprietary Trading Collateral and Netting (a) (e) Subtotal (b) Economic Hedges (c) Economic Hedges (d) Collateral and Netting (a) Subtotal Subtotal Total Derivatives Mark-to-market derivative assets (current assets) $ 3,398 $ 56 $ (2,612 ) $ 842 $ — $ — $ — $ — $ — $ 842 Mark-to-market derivative assets (noncurrent assets) 1,975 24 (1,475 ) 524 — — — — — 524 Total mark-to-market derivative assets 5,373 80 (4,087 ) 1,366 — — — — — 1,366 Mark-to-market derivative liabilities (current liabilities) (3,029 ) (49 ) 2,876 (202 ) (19 ) — — — — (221 ) Mark-to-market derivative liabilities (noncurrent liabilities) (1,780 ) (28 ) 1,655 (153 ) (263 ) — — — — (416 ) Total mark-to-market derivative liabilities (4,809 ) (77 ) 4,531 (355 ) (282 ) — — — — (637 ) Total mark-to-market derivative net assets (liabilities) $ 564 $ 3 $ 444 $ 1,011 $ (282 ) $ — $ — $ — $ — $ 729 ______ (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 $128 million and $77 million , respectively, and current and noncurrent liabilities are shown net of collateral of $136 million and $103 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $444 million at March 31, 2017 . (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. (e) Of the collateral posted/(received), $14 million represents variation margin on the exchanges. 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 Description Economic Hedges Proprietary Trading Collateral and Netting (a) (e) Subtotal (b) Economic Hedges (c) Economic Hedges (d) Collateral and Netting (a) Subtotal Subtotal Total 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, 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 $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.
The activity of accumulated OCI related to cash flow hedges	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 Three Months Ended March 31, 2017 Income Statement Location Total Cash Total Cash Accumulated OCI derivative loss at December 31, 2016 $ (19 ) $ (17 ) Effective portion of changes in fair value 2 2 Reclassifications from AOCI to net income Interest Expense 4 (a) 4 (a) Accumulated OCI derivative loss at March 31, 2017 $ (13 ) $ (11 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Three Months Ended March 31, 2016 Income Statement Location Total Cash Total Cash Flow Hedges Accumulated OCI derivative loss at December 31, 2015 $ (21 ) $ (19 ) Effective portion of changes in fair value (8 ) (10 ) Reclassifications from AOCI to net income Interest Expense 3 (b) 3 (b) Accumulated OCI derivative loss at March 31, 2016 $ (26 ) $ (26 ) __
Other Derivatives - Gain (loss) and reclassification	Generation Exelon Three Months Ended March 31, 2017 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ 93 $ (135 ) $ (42 ) $ (42 ) Reclassification to realized of commodity positions (47 ) 42 (5 ) (5 ) Net commodity mark-to-market gains (losses) 46 (93 ) (47 ) (47 ) Change in fair value of treasury positions (1 ) — (1 ) (1 ) Reclassification to realized of treasury positions (1 ) — (1 ) (1 ) Net treasury mark-to-market gains (losses) (2 ) — (2 ) (2 ) Net mark-to-market gains (losses) $ 44 $ (93 ) $ (49 ) $ (49 ) Generation Exelon Three Months Ended March 31, 2016 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ 279 $ (127 ) $ 152 $ 152 Reclassification to realized of commodity positions (211 ) 167 (44 ) (44 ) Net commodity mark-to-market gains (losses) 68 40 108 108 Change in fair value of treasury positions (3 ) — (3 ) (3 ) Reclassification to realized of treasury positions (2 ) — (2 ) (2 ) Net treasury mark-to-market gains (losses) (5 ) — (5 ) (5 ) Net mark-to-market gains (losses) $ 63 $ 40 $ 103 $ 103 Prop 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” represents the recognized change in fair value that was reclassified to realized due to settlement of the derivative during the period. Three Months Ended March 31, 2017 2016 Change in fair value of commodity positions $ — $ 7 Reclassification to realized of commodity positions (1 ) (3 ) Net commodity mark-to-market gains (losses) (1 ) 4 Change in fair value of treasury positions — (2 ) Reclassification to realized of treasury positions (1 ) 1 Net treasury mark-to-market gains (losses) (1 ) (1 ) Total net mark-to-market gains (losses) $ (2 ) $ 3 Cr
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	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: Credit-Risk Related Contingent Feature March 31, 2017 December 31, 2016 Gross Fair Value of Derivative Contracts Containing this Feature (a) $ (994 ) $ (960 ) Offsetting Fair Value of In-the-Money Contracts Under Master Netting Arrangements (b) 712 627 Net Fair Value of Derivative Contracts Containing This Feature (c) $ (282 ) $ (333 ) _______ (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. Ge following tables provide information on Generation’s credit exposure for all derivative instruments, NPNS and applicable payables and receivables, net of collateral and instruments that are subject to master netting agreements, as of March 31, 2017 . The tables further delineate that exposure by credit rating of the counterparties and provide guidance on the concentration of credit risk to individual counterparties. 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, NASDAQ, NGX 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 $13 million , $31 million , $24 million , $40 million , $13 million , and $7 million as of March 31, 2017 , respectively. Rating as of March 31, 2017 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 $ 964 $ 16 $ 948 1 $ 313 Non-investment grade 75 3 72 — — No external ratings Internally rated — investment grade 324 — 324 — — Internally rated — non-investment grade 127 14 113 — — Total $ 1,490 $ 33 $ 1,457 1 $ 313 Net Credit Exposure by Type of Counterparty As of March 31, 2017 Financial institutions $ 101 Investor-owned utilities, marketers, power producers 600 Energy cooperatives and municipalities 663 Other 93 Total $ 1,457 _____ (a) As of March 31, 2017 , credit collateral held from counterparties where Generation had credit exposure included $23 million of cash and $10 million of letters of credit. The credit collateral does not include non-liquid collateral.

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
Commercial Paper Borrowings	The Registrants had the following amounts of commercial paper borrowings outstanding as of March 31, 2017 and December 31, 2016 : Commercial Paper Borrowings March 31, 2017 December 31, 2016 Exelon Corporate $ 204 $ — Generation 579 620 ComEd 365 — PECO — — BGE 95 45 PHI Corporate — — Pepco 167 23
Issuance Of Long Term Debt	During the three months ended March 31, 2017 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Generation Energy Efficiency Project Financing 3.72 % April 30, 2018 $ 1 Funding to install energy conservation measures for the Smithsonian Zoo project Generation Energy Efficiency Project Financing 2.61 % September 30, 2018 $ 1 Funding to install energy conservation measures for the Pensacola project Generation Energy Efficiency Project Financing 3.90 % January 31, 2018 $ 6 Funding to install energy conservation measures for the Naval Station Great Lakes project Generation Albany Green Energy Project Financing LIBOR + 1.25% November 17, 2017 $ 13 Albany Green Energy biomass generation development Generation Senior Notes 2.95 % January 15, 2020 $ 250 Repay outstanding commercial paper obligations and for general corporate purposes. Generation Senior Notes 3.40 % March 15, 2022 $ 500 Repay outstanding commercial paper obligations and for general corporate purposes. Pepco Energy Efficiency Project Financing 3.30 % December 15, 2017 $ 1 Funding to install energy conservation measures for the DOE Germantown project

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	Three Months Ended March 31, 2017 Successor 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 0.9 1.0 4.9 0.1 5.2 4.6 5.3 5.6 4.9 Qualified nuclear decommissioning trust fund income 3.4 7.6 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.4) (0.7) (0.2) (0.1) (0.1) (0.1) (0.3) (0.4) (0.2) Plant basis differences (2.4) — (0.2) (13.2) (0.9) (5.8) (1.9) (3.4) (3.8) Production tax credits and other credits (0.6) (1.4) — — — — — — — Noncontrolling interests (0.1) (0.3) — — — — — — — Merger expenses (a) (11.4) (3.3) — — — (34.2) (21.9) (167.1) (42.4) Fitzpatrick bargain purchase gain (6.6) (14.5) — — — — — — — Other — (0.1) — 0.3 (0.2) 0.5 — (3.0) (0.4) Effective income tax rate 17.8% 23.3% 39.5% 22.1% 39.0% 0.0% 16.2% (133.3)% (6.9)% Successor Predecessor Three Months Ended March 31, 2016 March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco (b) DPL (b) ACE (b) PHI (b) 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 (c) (1.1) 3.7 5.1 1.0 5.2 (2.5) (2.7) 5.9 5.4 11.9 Qualified nuclear decommissioning trust fund income 5.6 4.2 — — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.6) (1.0) (0.3) (0.1) (0.1) — 0.1 0.2 — (0.9) Plant basis differences (5.5) — (0.1) (9.3) (0.6) 2.8 0.7 0.6 — (13.5) Production tax credits and other credits (5.1) (3.9) — — — — — — — — Noncontrolling interests 0.5 0.3 — — — — — — — — Merger expenses 33.6 — — — — (16.5) (22.1) (17.0) (15.1) 11.1 Other (2.0) (1.6) 0.4 (0.9) — — 0.1 0.1 0.2 3.6 Effective income tax rate 59.4% 36.7% 40.1% 25.7% 39.5% 18.8% 11.1% 24.8% 25.5% 47.2%

Nuclear Decommissioning (Tables

Nuclear Decommissioning (Tables) - Exelon Generation Co L L C [Member]	3 Months Ended
	Mar. 31, 2017
Schedule Of Nuclear Decommissioning [Line Items]
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 December 31, 2016 to March 31, 2017 : Nuclear decommissioning ARO at December 31, 2016 (a) $ 8,734 Acquisition of FitzPatrick 417 Accretion expense 109 Costs incurred to decommission retired plants (1 ) Nuclear decommissioning ARO at March 31, 2017 (a)(b) $ 9,259 _________ (a) Includes $11 million and $10 million for the current portion of the ARO at March 31, 2017 and December 31, 2016 , respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets. (b) Includes the fair value of the FitzPatrick ARO liability as of March 31, 2017, the date of the acquisition. See Note 4 - Mergers, Acquisitions and Dispositions .
Unrealized Gains (Losses) on nuclear decommissioning trust funds	The following table provides unrealized gains on NDT funds for the three months ended March 31, 2017 and 2016 : Exelon and Generation Three Months Ended 2017 2016 Net unrealized gains on decommissioning trust funds — Regulatory Agreement Units (a) $ 222 $ 79 Net unrealized gains on decommissioning trust funds — Non-Regulatory Agreement Units (b)(c) 166 52 _________ (a) Net unrealized gains 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 and $2 million of net unrealized gains (losses) related to the Zion Station pledged assets for the three months ended March 31, 2017 and 2016 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 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.
Zion Station pledged assets	and December 31, 2016 : Exelon and Generation March 31, 2017 December 31, 2016 Carrying value of Zion Station pledged assets $ 95 $ 113 Payable to Zion Solutions (a) 88 104 Current portion of payable to Zion Solutions (b) 85 90 Cumulative withdrawals by Zion Solutions to pay decommissioning costs (c) 895 878 _________ (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.

Retirement Benefits (Tables)

Retirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Schedule Of Pension And Other Postretirement Benefit Costs	The amounts below represent Exelon's, Generation's, ComEd's, PECO's, BGE's, PHI's, Pepco's, DPL's, ACE's, BSC's and PHISCO's allocated portion of the pension and postretirement benefit plan costs, which were included in Property, plant and equipment within the respective Consolidated Balance Sheets and Operating and maintenance expense within the Consolidated Statement of Operations and Comprehensive Income during the three months ended March 31, 2017 and 2016 and PHI's for the predecessor and successor periods of January 1, 2016 to March 23, 2016 and March 24, 2016 to March 31, 2016 , respectively. Three Months Ended March 31, Pension and Other Postretirement Benefit Costs 2017 2016 Exelon $ 157 $ 136 Generation 54 54 ComEd 44 41 PECO 7 8 BGE 16 16 BSC (a) 12 14 Pepco (b) 7 8 DPL (b) 3 5 ACE (b) 3 4 PHISCO (a)(b) 11 9 Successor Predecessor Pension and Other Postretirement Benefit Costs March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 PHI $ 3 $ 23 _________ (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, PHI, Pepco, DPL or ACE amounts above.
Schedule Of Defined Contributions	The following table presents the matching contributions to the savings plans during the three months ended March 31, 2017 and 2016 : Three Months Ended March 31, Savings Plan Matching Contributions 2017 2016 Exelon $ 30 $ 26 Generation 14 12 ComEd 7 6 PECO 2 2 BGE 2 1 BSC (a) 2 5 Pepco (b) 1 1 DPL (b) 1 1 PHISCO (a)(b) 1 1 Successor Predecessor Savings Plan Matching Contributions March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 PHI $ — $ 3 _________ (a) These amounts primarily represent amounts billed to Exelon and PHI's subsidiaries through intercompany allocations. These costs are not included in the Generation, ComEd, PECO, BGE, Pepco and DPL amounts above. (b) Pepco's, DPL's and PHISCO's matching contributions for the three months ended March 31, 2016 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 for the three months ended March 31, 2016.
Schedule of Net Benefit Costs [Table Text Block]	Pension Benefits Other Postretirement Benefits 2017 2016(a) 2017 2016(a) Components of net periodic benefit cost: Service cost $ 95 $ 78 $ 26 $ 26 Interest cost 210 190 45 43 Expected return on assets (299 ) (263 ) (41 ) (38 ) Amortization of: Prior service cost (benefit) — 3 (47 ) (44 ) Actuarial loss 152 127 16 14 Net periodic benefit cost $ 158 $ 135 $ (1 ) $ 1 _______ (a) PHI net periodic benefit costs for the period prior to the merger are not included in the table above. Predecessor PHI Pension Benefits Other Postretirement Benefits January 1, 2016 to March 23, 2016 January 1, 2016 to March 23, 2016 Components of net periodic benefit cost: Service cost $ 12 $ 1 Interest cost 26 6 Expected return on assets (30 ) (5 ) Amortization of: Prior service cost (benefit) — (3 ) Actuarial loss 14 2 Net periodic benefit cost $ 22 $ 1

Severance (Tables)

Severance (Tables)	3 Months Ended
	Mar. 31, 2017
Restructuring and Related Activities [Abstract]
Severance	Three Months Ended March 31, Acquisition, Integration and Financing Costs (a) 2017 2016 Exelon (b) $ 9 $ 102 Generation 9 16 ComEd (c) — (8 ) PECO 1 2 BGE 2 2 Pepco 1 27 DPL (d) (7 ) 16 ACE 1 13 Successor Predecessor Acquisition, Integration and Financing Costs (a) Three Months Ended March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 PHI (d) $ (5 ) $ 56 $ 29 ______________ (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 three months ended March 31, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $9 million , incurred at ComEd that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. (d) For the three months ended March 31, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million , incurred at DPL that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. For the three months ended March 31, 2017 and 2016 , Exelon, Generation, and ComEd recorded the following severance costs (benefits) associated with these ongoing severance benefits within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income. Exelon Generation (a) ComEd (a) Three Months Ended March 31, 2017 $ 4 $ 3 $ 1 March 31, 2016 2 2 — _______ (a) The amounts above for Generation include $1 million for amounts billed by BSC through intercompany allocations for both the three months ended March 31, 2017 and 2016 . Amounts billed by BSC to ComEd were immaterial. For the three months ended March 31, 2017 and 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 Three Months Ended March 31, 2017 (a) $ (1 ) $ (1 ) $ — $ — $ — March 31, 2016 (b) $ 17 $ 12 $ 3 $ 1 $ 1 _______ (a) Amounts billed by BSC through intercompany allocations for the three months ended March 31, 2017 were immaterial. (b) 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 three months ended March 31, 2016 . For the three months ended March 31, 2017 , the PHI merger severance costs were immaterial. For the three months ended March 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 DPL ACE Three Months Ended March 31, 2016 Severance benefits (a) $ 52 $ 10 $ 2 $ 1 $ 1 $ 37 $ 18 $ 11 $ 8 ______________ (a) The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $9 million , $2 million , $1 million , $1 million , $18 million , $11 million and $8 million , respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the three months ended March 31, 2016 .
Severance Liability	Amounts included in the table below represent the severance liability recorded for the severance plans above 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 Pepco DPL ACE Balance at December 31, 2016 $ 88 $ 36 $ 3 $ — $ — $ 29 $ — $ — $ — Severance charges (a) 3 1 — — — — — — — Payments (10 ) (3 ) — — — (5 ) — — — Balance at March 31, 2017 $ 81 $ 34 $ 3 $ — $ — $ 24 $ — $ — $ — ______________ (a) Includes salary continuance and health and welfare severance benefits.

Changes in Accumulated Other 38

Changes in Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2017
Changes in Accumulated Other Comprehensive Income [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	three months ended March 31, 2017 and 2016 : Three Months Ended March 31, 2017 Gains and (losses) on Cash Flow Hedges Unrealized Gains and (losses) on Marketable Securities Pension and Non-Pension Postretirement Benefit Plan Items Foreign Currency Items AOCI of Equity Investments Total Exelon (a) Beginning balance $ (17 ) $ 4 $ (2,610 ) $ (30 ) $ (7 ) $ (2,660 ) OCI before reclassifications 2 1 (59 ) 1 5 (50 ) Amounts reclassified from AOCI (b) 4 — 36 — — 40 Net current-period OCI 6 1 (23 ) 1 5 (10 ) Ending balance $ (11 ) $ 5 $ (2,633 ) $ (29 ) $ (2 ) $ (2,670 ) Generation (a) Beginning balance $ (19 ) $ 2 $ — $ (30 ) $ (7 ) $ (54 ) OCI before reclassifications 2 — — 1 6 9 Amounts reclassified from AOCI (b) 4 — — — — 4 Net current-period OCI 6 — — 1 6 13 Ending balance $ (13 ) $ 2 $ — $ (29 ) $ (1 ) $ (41 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 Three Months Ended March 31, 2016 Gains and (losses) on Hedging Activity Unrealized Gains and (losses) on Marketable Securities Pension and Non-Pension Postretirement Benefit Plan Items Foreign Currency Items AOCI of Equity Investments Total Exelon (a) Beginning balance $ (19 ) $ 3 $ (2,565 ) $ (40 ) $ (3 ) $ (2,624 ) OCI before reclassifications (10 ) (1 ) (1 ) 6 (3 ) (9 ) Amounts reclassified from AOCI (b) 3 — 34 — — 37 Net current-period OCI (7 ) (1 ) 33 6 (3 ) 28 Ending balance $ (26 ) $ 2 $ (2,532 ) $ (34 ) $ (6 ) $ (2,596 ) Generation (a) Beginning balance $ (21 ) $ 1 $ — $ (40 ) $ (3 ) $ (63 ) OCI before reclassifications (8 ) — — 6 (2 ) (4 ) Amounts reclassified from AOCI (b) 3 — — — — 3 Net current-period OCI (5 ) — — 6 (2 ) (1 ) Ending balance $ (26 ) $ 1 $ — $ (34 ) $ (5 ) $ (64 ) 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 ) ________ (a) All amounts are net of tax and noncontrolling interest. Amounts in parenthesis represent a decrease in AOCI. (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.
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 three months ended March 31, 2017 and 2016 . Three Months Ended March 31, 2017 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statement of Operations and Comprehensive Income Exelon Generation Gains and (losses) on cash flow hedges Other cash flow hedges $ (7 ) $ (7 ) Interest expense Total before tax (7 ) (7 ) Tax benefit 3 3 Net of tax $ (4 ) $ (4 ) Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 23 $ — Actuarial losses (b) (81 ) — Total before tax (58 ) — Tax benefit 22 — Net of tax $ (36 ) $ — Total Reclassifications $ (40 ) $ (4 ) Comprehensive income Three Months Ended March 31, 2016 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statement of Operations and Comprehensive Income Predecessor Exelon Generation PHI Gains and (losses) on cash flow hedges Other cash flow hedges $ (5 ) $ (5 ) — Interest expense Total before tax (5 ) (5 ) — Tax expense 2 2 — Net of tax $ (3 ) $ (3 ) $ — Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 20 $ — $ — Actuarial losses (b) (76 ) — (1 ) Total before tax (56 ) — (1 ) Tax benefit 22 — — Net of tax $ (34 ) $ — $ (1 ) Total Reclassifications $ (37 ) $ (3 ) $ (1 ) Comprehensive income _______ (a) Amounts in parenthesis represent a decrease in net income. (b) This AOCI component is included in the computation of net periodic pension and OPEB cost (see Note 13 — Retirement Benefits for additional details).
Schedule Of Other Comprehensive Income Loss Tax	The following table presents income tax expense (benefit) allocated to each component of other comprehensive income (loss) during the three months ended March 31, 2017 and 2016 : Three Months Ended March 31, 2017 2016 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 10 $ 7 Actuarial loss reclassified to periodic benefit cost (32 ) (30 ) Pension and non-pension postretirement benefit plans valuation adjustment — — Change in unrealized (loss)/gain on cash flow hedges (1 ) 3 Change in unrealized (loss)/gain on equity investments (4 ) 2 Change in unrealized (loss)/gain on marketable securities (1 ) 1 Total $ (28 ) $ (17 ) Generation Change in unrealized (loss)/gain on cash flow hedges $ (1 ) $ 2 Change in unrealized (loss)/gain on equity investments (3 ) 2 Total $ (4 ) $ 4

Earnings Per Share and Equity39

Earnings Per Share and Equity (Tables)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Reconciliation of basic and diluted earnings per share	Three Months Ended March 31, 2017 2016 Exelon Net income attributable to common shareholders $ 995 $ 173 Weighted average common shares outstanding — basic 928 923 Assumed exercise and/or distributions of stock-based awards 2 2 Weighted average common shares outstanding — diluted 930 925

Commitments and Contingencies40

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2017
Commitments And Contingencies Tables Disclosure [Line Items]
Commercial Commitments	The Registrants’ commercial commitments as of March 31, 2017 , representing commitments potentially triggered by future events were as follows: Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Letters of credit (non-debt) (a) $ 1,527 $ 1,440 $ 14 $ 23 $ 5 $ 1 $ 1 $ — $ — Surety bonds (b) 1,038 964 5 7 11 16 9 4 3 Financing trust guarantees 628 — 200 178 250 — — — — Guaranteed lease residual values (c) 19 — — — — 19 5 7 5 Total commercial commitments $ 3,212 $ 2,404 $ 219 $ 208 $ 266 $ 36 $ 15 $ 11 $ 8 ________ (a) Letters of credit (non-debt) - Exelon and certain 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.
Accrued environmental liabilities	of Three Months Ended March 31, 2017 and December 31, 2016 , 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: March 31, 2017 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 425 $ 319 Generation 71 — ComEd 288 286 PECO 33 31 BGE 4 2 PHI (Successor) 29 — Pepco 26 — DPL 2 — ACE 1 — December 31, 2016 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 429 $ 325 Generation 72 — ComEd 292 291 PECO 33 31 BGE 2 2 PHI (Successor) 30 1 Pepco 27 — DPL 2 1 ACE 1 —
Exelon Generation Co L L C [Member] | Equity Method Investments [Member]
Commitments And Contingencies Tables Disclosure [Line Items]
Other Commitments	, Generation’s estimated commitments relating to its equity purchase agreements, including the in-kind services contributions, is anticipated to be as follows: Total 2017 $ 9 2018 7 2019 3 Total $ 19

Supplemental Financial Inform41

Supplemental Financial Information (Tables)	3 Months Ended
	Mar. 31, 2017
Supplemental Financial Information [Abstract]
Components of non-operating income and expenses	The following tables provide additional information about the Registrants’ Consolidated Statements of Operations and Comprehensive Income for the three months ended March 31, 2017 and 2016 . Three Months Ended March 31, 2017 Successor 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 $ 68 $ 68 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 32 32 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 222 222 — — — — — — — Non-regulatory agreement units 166 166 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (1 ) (1 ) — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (234 ) (234 ) — — — — — — — Total decommissioning-related activities 253 253 — — — — — — — Investment income 2 2 — — — — — — — Interest income related to uncertain income tax positions 1 — — — — — — — — AFUDC — Equity 17 — 2 2 4 9 5 2 2 Other 10 4 2 — — 4 3 1 — Other, net $ 283 $ 259 $ 4 $ 2 $ 4 $ 13 $ 8 $ 3 $ 2 Successor Predecessor Three Months Ended March 31, 2016 March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 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 $ 34 $ 34 $ — $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 21 21 — — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 79 79 — — — — — — — — Non-regulatory agreement units 52 52 — — — — — — — — Net unrealized gains on pledged assets Zion Station decommissioning 2 2 — — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (95 ) (95 ) — — — — — — — — Total decommissioning-related activities 93 93 — — — — — — — — Investment income 6 1 — — 1 — — — — — Long-term lease income 4 — — — — — — — — — Interest income related to uncertain income tax positions 1 — — — — 1 — 1 — — AFUDC — Equity 8 — 2 2 3 4 1 2 1 7 Loss on debt extinguishment (2 ) (2 ) — — — — — — — — Other 4 1 2 — — 4 2 1 1 (11 ) Other, net $ 114 $ 93 $ 4 $ 2 $ 4 $ 9 $ 3 $ 4 $ 2 $ (4 ) ____ (a) Includes investment income and realized gains and losses on sales of investments of the 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 of the Exelon 2016 Form 10-K for additional information regarding the accounting for nuclear decommissioning.
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 three months ended March 31, 2017 and 2016 . Three Months Ended March 31, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Depreciation, amortization and accretion Property, plant and equipment (a) $ 754 $ 289 $ 190 $ 64 $ 80 $ 112 $ 50 $ 30 $ 21 Amortization of regulatory assets (a) 128 — 18 7 48 55 32 9 14 Amortization of intangible assets, net (a) 14 13 — — — — — — — Amortization of energy contract assets and liabilities (b) 2 2 — — — — — — — Nuclear fuel (c) 264 264 — — — — — — — ARO accretion (d) 112 110 — — — — — — — Total depreciation, amortization and accretion $ 1,274 $ 678 $ 208 $ 71 $ 128 $ 167 $ 82 $ 39 $ 35 Successor Predecessor Three Months Ended March 31, 2016 March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Depreciation, amortization and accretion Property, plant and equipment (a) $ 606 $ 278 $ 170 $ 60 $ 75 $ 42 $ 27 $ 20 $ 9 $ 94 Amortization of regulatory assets (a) 65 — 19 7 34 33 12 20 5 58 Amortization of intangible assets, net (a) 14 11 — — — — — — — — Amortization of energy contract assets and liabilities (b) (14 ) (14 ) — — — — — — — — Nuclear fuel (c) 283 283 — — — — — — — — ARO accretion (d) 109 109 — — — — — — — — Total depreciation, amortization and accretion $ 1,063 $ 667 $ 189 $ 67 $ 109 $ 75 $ 39 $ 40 $ 14 $ 152 ________ (a) Included in Depreciation and amortization on the Registrants' Consolidated Statements of Operations and Comprehensive Income. (b) Included in Operating revenues or Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (d) Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
Cash Flow Supplemental Disclosures	Three Months Ended March 31, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 157 $ 54 $ 44 $ 7 $ 16 $ 24 $ 7 $ 3 $ 3 Loss from equity method investments 10 10 — — — — — — — Provision for uncollectible accounts 34 9 7 17 5 (4 ) (5 ) (1 ) 1 Stock-based compensation costs 31 — — — — — — — — Other decommissioning-related activity (a) (84 ) (84 ) — — — — — — — Energy-related options (b) (4 ) (4 ) — — — — — — — Amortization of regulatory asset related to debt costs 2 — 1 — — 1 — — — Amortization of rate stabilization deferral (14 ) — — — 7 (21 ) (15 ) (6 ) — Amortization of debt fair value adjustment (5 ) (3 ) — — — (2 ) — — — Discrete impacts from EIMA (c) (24 ) — (24 ) — — — — — — Amortization of debt costs 9 4 1 — — — — — — Provision for excess and obsolete inventory 2 1 1 — — — — — — Other 4 3 1 (1 ) (4 ) (6 ) (2 ) (3 ) (2 ) Total other non-cash operating activities $ 118 $ (10 ) $ 31 $ 23 $ 24 $ (8 ) $ (15 ) $ (7 ) $ 2 Non-cash investing and financing activities: Change in capital expenditures not paid $ (298 ) $ (354 ) $ 25 $ — $ 41 $ (5 ) $ (6 ) $ 9 $ — Non-cash financing of capital projects 10 10 — — — — — — — Dividends on stock compensation 2 — — — — — — — — Successor Predecessor Three Months Ended March 31, 2016 March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 136 $ 54 $ 41 $ 8 $ 16 $ 8 $ 5 $ 4 $ 3 $ 23 Loss from equity method investments 3 3 — — — — — — — — Provision for uncollectible accounts 41 6 9 16 12 5 5 7 (2 ) 16 Stock-based compensation costs 44 — — — — — — — — 3 Other decommissioning-related activity (a) (55 ) (55 ) — — — — — — — — Energy-related options (b) (9 ) (9 ) — — — — — — — — Amortization of regulatory asset related to debt costs 1 — 1 — — 1 — — — 1 Amortization of rate stabilization deferral 20 — — — 20 1 4 — — 5 Amortization of debt fair value adjustment (3 ) (3 ) — — — — — — — — Discrete impacts from EIMA (c) (14 ) — (14 ) — — — — — — — Amortization of debt costs 8 4 1 1 1 — — — — — Provision for excess and obsolete inventory 1 1 — — — 1 1 1 — 1 Merger-related commitments (d)(e) 503 3 — — — 138 100 120 358 — Severance costs 69 4 — — — — — — 52 — Asset retirement costs — — — — — — 4 2 — — Lower of cost or net realizable value inventory adjustment 36 36 — — — — — — — — Other 23 7 (6 ) (1 ) (5 ) (1 ) (1 ) (2 ) (1 ) (3 ) Total other non-cash operating activities $ 804 $ 51 $ 32 $ 24 $ 44 $ 153 $ 118 $ 132 $ 410 $ 46 Non-cash investing and financing activities: Change in capital expenditures not paid $ (290 ) $ (234 ) $ 25 $ (65 ) $ (4 ) $ 9 $ 8 $ (9 ) $ (7 ) $ 11 Fair value of net assets contributed to Generation in connection with the PHI Merger, net of cash (d)(f) — 119 — — — — — — — — Fair value of net assets distributed to Exelon in connection with the PHI Merger, net of cash (d)(f) — — — — — — — — 127 — Fair value of pension obligation transferred in connection with the PHI Merger — — — — — — — — 45 — Assumption of member purchase liability — — — — — — — — 29 — Change in PPE related to ARO update 62 62 — — — — — — — — Indemnification of like-kind exchange position (g) — — 1 — — — — — — — Non-cash financing of capital projects 31 31 — — — — — — — — Dividends on stock compensation 1 — — — — — — — — — ________ (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 of the Exelon 2016 Form 10-K 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 in Operating revenues. (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 tariff. See Note 5 — Regulatory Matters for more information. (d) See Note 4 — Mergers, Acquisitions and Dispositions for additional information related to the merger with PHI. (e) 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. (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) See Note 11 — Income Taxes for discussion of the like-kind exchange tax position.
Supplemental Balance Sheet Disclosures	The following tables provide additional information about assets and liabilities of the Registrants as of March 31, 2017 and December 31, 2016 . Successor March 31, 2017 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Property, plant and equipment: Accumulated depreciation and amortization $ 19,716 (a) $ 10,801 (a) $ 4,040 $ 3,293 $ 3,311 $ 281 $ 3,090 $ 1,195 $ 1,032 Accounts receivable: Allowance for uncollectible accounts $ 346 $ 97 $ 80 $ 72 $ 35 $ 61 $ 18 $ 20 $ 23 Successor December 31, 2016 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Property, plant and equipment: Accumulated depreciation and amortization $ 19,169 (b) $ 10,562 (b) $ 3,937 $ 3,253 $ 3,254 $ 195 $ 3,050 $ 1,175 $ 1,016 Accounts receivable: Allowance for uncollectible accounts $ 334 $ 91 $ 70 $ 61 $ 32 $ 80 $ 29 $ 24 $ 27 _______ (a) Includes accumulated amortization of nuclear fuel in the reactor core of $3,171 million . (b) Includes accumulated amortization of nuclear fuel in the reactor core of $3,186 million
Schedule Of Taxes Excluding Income And Excise Taxes [Text Block]	The following utility taxes are included in revenues and expenses for the three months ended March 31, 2017 and 2016 . Generation’s utility tax expense represents gross receipts tax related to its retail operations, and the utility registrants' utility tax expense represents 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. Three Months Ended March 31, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 224 $ 32 $ 59 $ 31 $ 26 $ 76 $ 71 $ 5 $ — Successor Predecessor Three Months Ended March 31, 2016 March 24, 2016 to March 31, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Utility taxes $ 153 $ 28 $ 59 $ 35 $ 24 $ 79 $ 5 $ — $ 7 $ 77

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2017
Segment Reporting Information [Line Items]
Analysis and reconciliation of reportable segment information
Analysis and reconciliation of reportable segment revenues for Generation	_________ (a) Generation includes the six reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. Intersegment revenues for Generation for the three months ended March 31, 2017 include revenue from sales to PECO of $45 million , sales to BGE of $134 million , sales to Pepco of $83 million , sales to DPL of $51 million , and sales to ACE of $9 million in the Mid-Atlantic region, and sales to ComEd of $5 million in the Midwest region. For the three months ended March 31, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $79 million and sales to BGE of $173 million in the Mid-Atlantic region, and sales to ComEd of $5 million in the Midwest region. For the Successor period of March 24, 2016 to March 31, 2016 , intersegment revenues for Generation include revenue from sales to Pepco of $6 million , sales to DPL of $4 million , and sales to ACE of $1 million in the Mid-Atlantic region. (b) Amounts included represent activity for PHI's successor period, March 24, 2016 through March 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 three months ended March 31, 2016 . (c) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (d) 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 18 — Supplemental Financial Information for total utility taxes for the three months ended March 31, 2017 and 2016 . (e) 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. Successor and Predecessor PHI: Pepco DPL ACE Other (b) Intersegment PHI Operating revenues (a) : Three Months Ended March 31, 2017 - Successor Rate-regulated electric revenues $ 530 $ 296 $ 275 $ — $ (4 ) $ 1,097 Rate-regulated natural gas revenues — 66 — — — 66 Shared service and other revenues — — — 12 — 12 March 24, 2016 to March 31, 2016 - Successor Rate-regulated electric revenues $ 40 $ 24 $ 23 $ 3 $ — $ 90 Rate-regulated natural gas revenues — 3 — — — 3 Shared service and other revenues — — — 12 — 12 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 — — — — — — Intersegment revenues: Three Months Ended March 31, 2017 - Successor $ 1 $ 2 $ 1 $ 13 $ (5 ) $ 12 March 24, 2016 to March 31, 2016 - Successor — — — 12 — 12 January 1, 2016 to March 23, 2016 - Predecessor 1 2 1 — (4 ) — Net income (loss): Three Months Ended March 31, 2017 - Successor $ 58 $ 57 $ 28 $ (15 ) $ 12 $ 140 March 24, 2016 to March 31, 2016 - Successor (140 ) (98 ) (105 ) 22 12 (309 ) January 1, 2016 to March 23, 2016 - Predecessor 32 26 5 (44 ) — 19 Total assets: March 31, 2017 - Successor $ 7,417 $ 4,191 $ 3,451 $ 10,785 $ (4,826 ) $ 21,018 December 31, 2016 - Successor 7,335 4,153 3,457 10,804 (4,724 ) 21,025 _________ (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 18 — Supplemental Financial Information for total utility taxes for the three months ended March 31, 2017 and 2016 . (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: Three Months Ended March 31, 2017 Three Months Ended March 31, 2016 Revenues (a) Intersegment Total Revenues (a) Intersegment Total Mid-Atlantic $ 1,429 $ (4 ) $ 1,425 $ 1,532 $ (12 ) $ 1,520 Midwest 1,051 2 1,053 1,089 6 1,095 New England 549 (2 ) 547 471 (1 ) 470 New York 310 (3 ) 307 218 (15 ) 203 ERCOT 192 (1 ) 191 163 — 163 Other Power Regions 189 (5 ) 184 222 1 223 Total Revenues for Reportable Segments 3,720 (13 ) 3,707 3,695 (21 ) 3,674 Other (b) 1,168 13 1,181 1,044 21 1,065 Total Generation Consolidated Operating Revenues $ 4,888 $ — $ 4,888 $ 4,739 $ — $ 4,739 _ _________ (a) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. Includes a $3 million decrease to revenues and a $20 million increase to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the three months ended March 31, 2017 and 2016 , respectively, unrealized mark-to-market gains of $44 million and $63 million for the three months ended March 31, 2017 and 2016 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense:
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Analysis and reconciliation of reportable segment revenues for Generation

Significant Accounting Polici43

Significant Accounting Policies - Narrative (Details) - USD ($)	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 23, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities		$ (1,201,000,000)	$ (1,473,000,000)
Net Cash Provided by (Used in) Financing Activities		(1,184,000,000)	(1,533,000,000)
Pepco Holdings LLC [Member] | Predecessor [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results		1,000,000
Net Cash Provided by (Used in) Operating Activities				$ (264,000,000)
Net Cash Provided by (Used in) Financing Activities				$ (372,000,000)
Pepco Holdings LLC [Member] | Successor [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Amount	$ 46,000,000
Net Cash Provided by (Used in) Operating Activities	3,000,000	(194,000,000)
Net Cash Provided by (Used in) Financing Activities	$ 135,000,000	(66,000,000)
Delmarva Power and Light Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results		1,000,000
Net Cash Provided by (Used in) Operating Activities		(122,000,000)	(147,000,000)
Net Cash Provided by (Used in) Financing Activities		44,000,000	68,000,000
Atlantic City Electric Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results		1,000,000
Net Cash Provided by (Used in) Operating Activities		(58,000,000)	(246,000,000)
Net Cash Provided by (Used in) Financing Activities		20,000,000	27,000,000
Potomac Electric Power Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results		1,000,000
Net Cash Provided by (Used in) Operating Activities		(29,000,000)	(258,000,000)
Net Cash Provided by (Used in) Financing Activities		$ (114,000,000)	$ 103,000,000

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details)		3 Months Ended
		Mar. 31, 2017USD ($)VIE	Mar. 31, 2016USD ($)	Dec. 31, 2016USD ($)VIE	Apr. 01, 2014USD ($)
Variable Interest Entity [Line Items]
Other Commitment		$ 3,212,000,000
Variable Interest Entity, Financial or Other Support, Amount		$ 27,000,000
Number of Variable Interest Entities not consolidated by equity holders | VIE		7		8
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		$ 16,000,000
Number Of Variable Interest Entities Consolidated | VIE		9		9
Guarantor Obligations, Current Carrying Value		$ 75,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted		48,000,000
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value		275,000,000
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Measure of Activity, Other, Amount		0.5001
Other Commitment		2,404,000,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		$ 16,000,000
Related Party Purchase Of Nuclear Output By Third Party Percentage		49.99%
Exelon Generation Co L L C [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value		$ 275,000,000
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value		8,000,000
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Other Commitment		266,000,000
Baltimore Gas and Electric Company [Member] | RSB Bond Co LLC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Financial or Other Support, Amount		19,000,000	$ 20,000,000
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Other Commitment		8,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted		13,000,000
Atlantic City Electric Company [Member] | ATF [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Financial or Other Support, Amount		19,000,000	$ 14,000,000
Distributed Energy Company [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests		227,000,000
Constellation Energy Nuclear Group [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Receivables from affiliates		320,000,000			$ 400,000,000
Financial Guarantee [Member] | Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted					165,000,000
Payment Guarantee [Member] | Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Payables to affiliates					$ 245,000,000
Equity Method Investment Variable Interest Entities [Member] | Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value		637,000,000
Investments [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		279,000,000		$ 264,000,000
Investments [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		0		0
Investments [Member] | Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		279,000,000		264,000,000
Finite-Lived Intangible Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		9,000,000		9,000,000
Finite-Lived Intangible Assets [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		9,000,000		9,000,000
Finite-Lived Intangible Assets [Member] | Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		0		0
Debt [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		0		3,000,000
Debt [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		0		0
Debt [Member] | Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		0		3,000,000
Other Assets [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	[1]	7,000,000		9,000,000
Other Assets [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	[1]	7,000,000		9,000,000
Other Assets [Member] | Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount	[1]	$ 0		$ 0
[1]	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 $95 million and $113 million as of March 31, 2017 and December 31, 2016, respectively; offset by payables to ZionSolutions LLC of $88 million and $104 million as of March 31, 2017 and December 31, 2016, respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE.

Variable Interest Entities - Ca

Variable Interest Entities - Carrying Amounts and Classification of Consolidated VIE Assets and Liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Consolidated VIE Assets		$ 9,909	$ 9,517
Consolidated VIE Liabilities		3,616	3,598
Assets		117,068	114,904
Liabilities	[1]	88,777	87,292
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		9,148	8,893
Liabilities		3,345	3,356
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		9,820	9,441
Consolidated VIE Liabilities		3,445	3,414
Assets		48,609	46,974
Liabilities	[2]	35,045	33,718
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		9,059	8,817
Liabilities		3,174	3,170
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		45	26
Consolidated VIE Liabilities		42	42
Assets	[3]	8,821	8,704
Liabilities	[3]	5,897	5,856
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		45	26
Liabilities		42	42
Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets			49
Consolidated VIE Liabilities			143
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		44
Consolidated VIE Liabilities		129
Assets		21,018	21,025
Liabilities		12,431	13,009
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Assets			49
Liabilities			143
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Assets		44
Liabilities		129
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		30	32
Consolidated VIE Liabilities		115	126
Assets		3,451	3,457
Liabilities		2,399	2,423
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		30	32
Liabilities		115	126
CurrentAssetsMember [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		1,018	954
CurrentAssetsMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		965	916
CurrentAssetsMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		42	23
CurrentAssetsMember [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets			14
CurrentAssetsMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		11
CurrentAssetsMember [Member] | Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		7	9
NoncurrentAssetMember [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		8,891	8,563
NoncurrentAssetMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		8,855	8,525
NoncurrentAssetMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		3	3
NoncurrentAssetMember [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets			35
NoncurrentAssetMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		33
NoncurrentAssetMember [Member] | Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		23	23
CurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		871	885
CurrentLiabilityMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		791	802
CurrentLiabilityMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		42	42
CurrentLiabilityMember [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities			42
CurrentLiabilityMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		38
CurrentLiabilityMember [Member] | Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		34	37
NoncurrentLiabilityMember [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		2,745	2,713
NoncurrentLiabilityMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		2,654	2,612
NoncurrentLiabilityMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		0	0
NoncurrentLiabilityMember [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities			101
NoncurrentLiabilityMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		91
NoncurrentLiabilityMember [Member] | Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		$ 81	$ 89
[1]	Exelon’s consolidated assets include $9,148 million and $8,893 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,345 million and $3,356 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 3 - Variable Interest Entities.
[2]	Generation’s consolidated assets include $9,059 million and $8,817 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,174 million and $3,170 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 3 - Variable Interest Entities.
[3]	BGE’s consolidated assets include $45 million and $26 million at March 31, 2017 and December 31, 2016, 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 $42 million at March 31, 2017 and December 31, 2016, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 3 - Variable Interest Entities.

Variable Interest Entities - As

Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016		Mar. 31, 2016	Mar. 23, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 609	$ 635		$ 960		$ 6,502
Restricted cash		254	253
Accounts receivable, net
Customer		3,886	4,158
Other		1,133	1,201
Derivative Asset, Current		847	917
Inventory
Materials and supplies		1,312	1,274
Other current assets		1,221	930
Total current assets		12,194	12,412
Property, plant and equipment, net		72,630	71,555
Nuclear decommissioning trust funds		12,362	11,061
Goodwill		6,677	6,677
Derivative Asset, Noncurrent		539	492
Other noncurrent assets		1,440	1,472
Total assets		117,068	114,904
Short-term borrowings		2,048	1,267
Long-term debt due within one year		3,645	2,430
Accounts payable		3,011	3,441
Accrued expenses		3,007	3,460
Mark-to-market derivative liabilities (current liabilities)		228	282
Other current liabilities		388	407
Other		942	981
Total current liabilities		14,437	13,457
Long-term debt		31,044	31,575
Asset retirement obligations		9,634	9,111
Pension obligation(c)		4,082	4,248
Energy Marketing Contract Liabilities, Noncurrent		779	830
Other noncurrent liabilities		1,853	1,827
Total liabilities	[1]	88,777	87,292
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		199	150
Restricted cash		124	59
Accounts receivable, net
Customer		347	371
Other		23	48
Derivative Asset, Current		41	31
Inventory
Materials and supplies		191	199
Other current assets		58	50
Total current assets		983	908
Property, plant and equipment, net		5,425	5,415
Nuclear decommissioning trust funds		2,286	2,185
Goodwill		47	47
Derivative Asset, Noncurrent		57	23
Other noncurrent assets		350	315
Total noncurrent assets		8,165	7,985
Total assets		9,148	8,893
Long-term debt due within one year		237	181
Accounts payable		275	269
Accrued expenses		85	119
Mark-to-market derivative liabilities (current liabilities)		18	60
Other current liabilities		16	15
Other		11	30
Total current liabilities		642	674
Long-term debt		626	641
Asset retirement obligations	[2]	1,929	1,904
Pension obligation(c)		8	9
Energy Marketing Contract Liabilities, Noncurrent		18	22
Other noncurrent liabilities		122	106
Total deferred credits and other liabilities		2,703	2,682
Total liabilities		3,345	3,356
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		400	290		377		431
Restricted cash		140	158
Accounts receivable, net
Customer		2,278	2,433
Other		545	558
Derivative Asset, Current		847	917
Inventory
Materials and supplies		957	935
Other current assets		881	701
Total current assets		6,514	6,528
Property, plant and equipment, net		25,893	25,585
Nuclear decommissioning trust funds		12,362	11,061
Goodwill		47	47
Derivative Asset, Noncurrent		527	476
Other noncurrent assets		648	688
Total assets		48,609	46,974
Short-term borrowings		717	699
Long-term debt due within one year		1,156	1,117
Accounts payable		1,482	1,610
Accrued expenses		720	989
Mark-to-market derivative liabilities (current liabilities)		209	263
Other current liabilities		68	72
Other		286	313
Total current liabilities		5,237	5,683
Long-term debt		7,904	7,202
Asset retirement obligations		9,444	8,922
Energy Marketing Contract Liabilities, Noncurrent		78	80
Other noncurrent liabilities		615	595
Total liabilities	[3]	35,045	33,718
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		199	150
Restricted cash		75	27
Accounts receivable, net
Customer		347	371
Other		23	48
Derivative Asset, Current		41	31
Inventory
Materials and supplies		191	199
Other current assets		54	44
Total current assets		930	870
Property, plant and equipment, net		5,425	5,415
Nuclear decommissioning trust funds		2,286	2,185
Goodwill		47	47
Derivative Asset, Noncurrent		57	23
Other noncurrent assets		314	277
Total noncurrent assets		8,129	7,947
Total assets		9,059	8,817
Long-term debt due within one year		159	99
Accounts payable		275	269
Accrued expenses		83	116
Mark-to-market derivative liabilities (current liabilities)		18	60
Other current liabilities		16	15
Other		11	30
Total current liabilities		562	589
Long-term debt		535	540
Asset retirement obligations		1,929	1,904	[2]
Pension obligation(c)		8	9
Energy Marketing Contract Liabilities, Noncurrent		18	22
Other noncurrent liabilities		122	106
Total deferred credits and other liabilities		2,612	2,581
Total liabilities		3,174	3,170
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		11	23		5		9
Restricted cash		43	24
Accounts receivable, net
Customer		393	395
Other		79	102
Inventory
Materials and supplies		41	38
Other current assets		11	7
Total current assets		812	842
Property, plant and equipment, net		7,166	7,040
Other noncurrent assets		10	9
Total assets	[4]	8,821	8,704
Short-term borrowings		95	45
Long-term debt due within one year		41	41
Accounts payable		186	205
Accrued expenses		120	175
Other		23	26
Total current liabilities		693	707
Long-term debt		2,282	2,281
Asset retirement obligations		20	21
Other noncurrent liabilities		59	61
Total liabilities	[4]	5,897	5,856
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		42	23
Accounts receivable, net
Customer		0	0
Other		0	0
Derivative Asset, Current		0	0
Inventory
Materials and supplies		0	0
Other current assets		0	0
Total current assets		42	23
Property, plant and equipment, net		0	0
Nuclear decommissioning trust funds		0	0
Goodwill		0	0
Derivative Asset, Noncurrent		0	0
Other noncurrent assets		3	3
Total noncurrent assets		3	3
Total assets		45	26
Long-term debt due within one year		41	41
Accounts payable		0	0
Accrued expenses		1	1
Mark-to-market derivative liabilities (current liabilities)		0	0
Other current liabilities		0	0
Other		0	0
Total current liabilities		42	42
Long-term debt			0
Asset retirement obligations		0	0
Pension obligation(c)	[2]	0	0
Energy Marketing Contract Liabilities, Noncurrent		0	0
Other noncurrent liabilities		0	0
Total deferred credits and other liabilities		0	0
Total liabilities		42	42
Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents						$ 319	26
Accounts receivable, net
Derivative Asset, Current			0
Inventory
Derivative Asset, Noncurrent			0
Mark-to-market derivative liabilities (current liabilities)			0
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		109	170		151	$ 319
Restricted cash		41	43
Accounts receivable, net
Customer		440	496
Other		210	283
Derivative Asset, Current		0
Inventory
Materials and supplies		131	116
Other current assets		64	71
Total current assets		1,650	1,838
Property, plant and equipment, net		11,801	11,598
Goodwill		4,005	4,005
Derivative Asset, Noncurrent		0
Other noncurrent assets		80	81
Total assets		21,018	21,025
Short-term borrowings		167	522
Long-term debt due within one year		241	253
Accounts payable		386	458
Accrued expenses		269	272
Mark-to-market derivative liabilities (current liabilities)		0
Other current liabilities		320	335
Other		43	47
Total current liabilities		1,800	2,284
Long-term debt		5,619	5,645
Asset retirement obligations		14	14
Energy Marketing Contract Liabilities, Noncurrent		701	750
Other noncurrent liabilities		225	249
Total liabilities		12,431	13,009
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents			0
Restricted cash			9
Accounts receivable, net
Customer			0
Other			0
Derivative Asset, Current			0
Inventory
Materials and supplies			0
Other current assets			5
Total current assets			14
Property, plant and equipment, net			0
Nuclear decommissioning trust funds			0
Goodwill			0
Derivative Asset, Noncurrent			0
Other noncurrent assets			35
Total noncurrent assets			35
Total assets			49
Long-term debt due within one year			40
Accounts payable			0
Accrued expenses			2
Mark-to-market derivative liabilities (current liabilities)			0
Other current liabilities			0
Other			0
Total current liabilities			42
Long-term debt			101
Asset retirement obligations			0
Pension obligation(c)	[2]		0
Energy Marketing Contract Liabilities, Noncurrent			0
Other noncurrent liabilities			0
Total deferred credits and other liabilities			101
Total liabilities			143
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0
Restricted cash		7
Accounts receivable, net
Customer		0
Other		0
Derivative Asset, Current		0
Inventory
Materials and supplies		0
Other current assets		4
Total current assets		11
Property, plant and equipment, net		0
Nuclear decommissioning trust funds		0
Goodwill		0
Derivative Asset, Noncurrent		0
Other noncurrent assets		33
Total noncurrent assets		33
Total assets		44
Long-term debt due within one year		37
Accounts payable		0
Accrued expenses		1
Mark-to-market derivative liabilities (current liabilities)		0
Other current liabilities		0
Other		0
Total current liabilities		38
Long-term debt		91
Asset retirement obligations		0
Pension obligation(c)	[2]	0
Energy Marketing Contract Liabilities, Noncurrent		0
Other noncurrent liabilities		0
Total deferred credits and other liabilities		91
Total liabilities		129
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		54	101		$ 122		$ 3
Restricted cash		7	9
Accounts receivable, net
Customer		111	125
Other		41	44
Inventory
Materials and supplies		23	22
Other current assets		3	2
Total current assets		333	399
Property, plant and equipment, net		2,583	2,521
Other noncurrent assets		42	44
Total assets		3,451	3,457
Long-term debt due within one year		33	35
Accounts payable		125	132
Accrued expenses		50	38
Other		9	8
Total current liabilities		320	320
Long-term debt		1,112	1,120
Other noncurrent liabilities		23	32
Total liabilities		2,399	2,423
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash		7	9
Accounts receivable, net
Customer		0	0
Other		0	0
Derivative Asset, Current		0	0
Inventory
Materials and supplies		0	0
Other current assets		0	0
Total current assets		7	9
Property, plant and equipment, net		0	0
Nuclear decommissioning trust funds		0	0
Goodwill		0	0
Derivative Asset, Noncurrent		0	0
Other noncurrent assets		23	23
Total noncurrent assets		23	23
Total assets		30	32
Long-term debt due within one year		33	35
Accounts payable		0	0
Accrued expenses		1	2
Mark-to-market derivative liabilities (current liabilities)		0	0
Other current liabilities		0	0
Other		0	0
Total current liabilities		34	37
Long-term debt		81	89
Asset retirement obligations		0	0
Pension obligation(c)	[2]	0	0
Energy Marketing Contract Liabilities, Noncurrent		0	0
Other noncurrent liabilities		0	0
Total deferred credits and other liabilities		81	89
Total liabilities		$ 115	$ 126
[1]	Exelon’s consolidated assets include $9,148 million and $8,893 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,345 million and $3,356 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 3 - Variable Interest Entities.
[2]	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 Consolidated Balance Sheets. See Note 13 - Retirement Benefits for additional details.
[3]	Generation’s consolidated assets include $9,059 million and $8,817 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,174 million and $3,170 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 3 - Variable Interest Entities.
[4]	BGE’s consolidated assets include $45 million and $26 million at March 31, 2017 and December 31, 2016, 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 $42 million at March 31, 2017 and December 31, 2016, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 3 - Variable Interest Entities.

Variable Interest Entities - Su

Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Total assets	[1]	$ 1,188	$ 1,205
Total liabilities	[1]	303	502
Exelon's ownership interest in VIE	[1]	276	248
Other ownership interests in VIE	[1]	610	455
Registrants' maximum exposure to loss		16
Assets Held-in-trust, Noncurrent		95	113
Investments [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		279	264
Debt [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	3
Finite-Lived Intangible Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Other Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	7	9
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	647	638
Total liabilities	[1]	73	215
Exelon's ownership interest in VIE	[1]	0	0
Other ownership interests in VIE	[1]	574	423
Commercial Agreement Variable Interest Entities [Member] | Investments [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Commercial Agreement Variable Interest Entities [Member] | Debt [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Commercial Agreement Variable Interest Entities [Member] | Finite-Lived Intangible Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Commercial Agreement Variable Interest Entities [Member] | Other Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	7	9
Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	541	567
Total liabilities	[1]	230	287
Exelon's ownership interest in VIE	[1]	276	248
Other ownership interests in VIE	[1]	36	32
Equity Investment VIE [Member] | Investments [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		279	264
Equity Investment VIE [Member] | Debt [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	3
Equity Investment VIE [Member] | Finite-Lived Intangible Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Equity Investment VIE [Member] | Other Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	0	0
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		16
Assets Held-in-trust, Noncurrent		95	113
Payable to Zion Solutions	[3]	$ 88	$ 104
[1]	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.
[2]	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 $95 million and $113 million as of March 31, 2017 and December 31, 2016, respectively; offset by payables to ZionSolutions LLC of $88 million and $104 million as of March 31, 2017 and December 31, 2016, respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE.
[3]	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.

Mergers, Acquisitions, and Di48

Mergers, Acquisitions, and Dispositions - Narrative (Details) $ / shares in Units, MW in Millions, $ in Millions		Mar. 31, 2016USD ($)MW	Mar. 31, 2017USD ($)MW		Mar. 31, 2016USD ($)		Dec. 31, 2016USD ($)		Mar. 24, 2016USD ($)$ / shares
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue					$ 8,556	[1]	$ 32,342	[2]
Revenues			$ 8,757		7,573
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross			(212)		(6,645)
Business Combination, Integration Related Costs	[3],[4]		9		102
Other Commitment			3,212
Net income			981		123
Business Combination, Bargain Purchase, Gain Recognized, Amount			226		0
Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Revenues			1,200		107
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Cash offered in exchange for each share of PHI stock | $ / shares									$ 27.25
Other Commitment			513
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets	[5]		4,005
Business Combination, Contingent Consideration, Asset									$ 235
Net income			140		(315)
Pepco Holdings LLC [Member] | Other Intangible Assets [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Finite-lived Intangible Assets Acquired			$ 1,500
Pepco Holdings LLC [Member] | Common Stock [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross		$ (6,933)
Pepco Holdings LLC [Member] | Common Stock [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross		$ (180)
Pepco Holdings LLC [Member] | Other Solar Projects [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
OtherNonFinancialCommitment1 | MW		37	27
Pepco Holdings LLC [Member] | Wind Assets [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
OtherNonFinancialCommitment1 | MW		100
Pepco Holdings LLC [Member] | Other Investments [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Other Commitment									137
PEPCO Holdings Inc [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross		$ (7,142)
Other Commitment			$ 513
PEPCO Holdings Inc [Member] | Other Investments [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Other Commitment			444
Fitzpatrick [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Bargain Purchase, Gain Recognized, Amount			226
Business Combination, Consideration Transferred			293
Fitzpatrick [Member] | Cash and Cash Equivalents [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Consideration Transferred			110
Business Combination, Consideration Transferred, Other			129
Fitzpatrick [Member] | Nuclear Fuel [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Consideration Transferred, Other			54
Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Revenues			4,888		4,739
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross			(212)		(1)
Business Combination, Integration Related Costs	[4]		9		16
Other Commitment			2,404
Net income			409		257
Members' Capital			9,310				9,261
Business Combination, Bargain Purchase, Gain Recognized, Amount			226		0
Exelon Generation Co L L C [Member] | Pepco Holdings LLC [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Contingent Consideration, Asset									163
Exelon Generation Co L L C [Member] | Fitzpatrick [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross			(302)
Business Combination, Integration Related Costs			32
Business Combination, Consideration Transferred			293
Business Combination, Consideration Transferred, Other			183
Exelon Generation Co L L C [Member] | Fitzpatrick [Member] | Cash and Cash Equivalents [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross			(248)
Business Combination, Consideration Transferred			110
Exelon Generation Co L L C [Member] | Fitzpatrick [Member] | Nuclear Fuel [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross			(54)
Exelon Generation Co L L C [Member] | Fitzpatrick [Member] | Accounts Receivable [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross			(9)
Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Revenues			275		291
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Integration Related Costs	[4]		1		13
Other Commitment			8
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets			1,200
Net income			28		(100)
Atlantic City Electric Company [Member] | Pepco Holdings LLC [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Other Commitment			111
Equity Contribution		49
Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Revenues			530		551
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Other Commitment			15
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets			1,700
Net income			58		(108)
Potomac Electric Power Company [Member] | Pepco Holdings LLC [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Other Commitment			126
Equity Contribution		73
Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Revenues			362		362
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Integration Related Costs	[4]		(7)	[6]	16
Other Commitment			11
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets			1,100
Net income			57		(72)
Delmarva Power and Light Company [Member] | Pepco Holdings LLC [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Other Commitment			85
Equity Contribution		46
Pepco Holdings LLC [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Integration Related Costs	[4]		1		$ 27
Pepco Holdings LLC [Member] | Scenario, Adjustment [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Fresh-Start Adjustment, Increase (Decrease), Deferred Income Tax Liabilities, Noncurrent									59
Pepco Holdings LLC [Member] | Successor [Member]
Business Acquisition [Line Items]
Revenues		105	1,175
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Integration Related Costs		56	(5)
Net income		$ (309)	140
Members' Capital			8,577				$ 8,077		$ 7,200
Pepco Holdings LLC [Member] | Pepco Holdings LLC [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Other Commitment			$ 322
[1]	The amounts above include adjustments for non-recurring costs directly related to the merger of $639 million and intercompany revenue of $170 million for the three months ended March 31, 2016.
[2]	The amounts above include adjustments for non-recurring costs directly related to the merger of $680 million and intercompany revenue of $171 million for the year ended December 31, 2016.
[3]	Reflects costs (benefits) recorded at Exelon related to financing, including mark-to-market activity on forward-starting interest rate swaps.
[4]	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.
[5]	Amounts shown reflect the final purchase price allocation and the correction of a reporting error identified and corrected in the second quarter of 2016. The error had resulted in a gross up of certain assets and liabilities related to legacy PHI intercompany and income tax receivable and payable balances.
[6]	For the three months ended March 31, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, incurred at DPL that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.

Mergers, Acquisitions, and Di49

Mergers, Acquisitions, and Dispositions Merger Commitments Table (Details)	Mar. 31, 2017USD ($)
Other Commitments [Line Items]
Other Commitment	$ 3,212,000,000
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	15,000,000
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	11,000,000
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	8,000,000
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	513,000,000
Pepco Holdings LLC [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	322,000,000
Pepco Holdings LLC [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	126,000,000
Pepco Holdings LLC [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	85,000,000
Pepco Holdings LLC [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	111,000,000
Pepco Holdings LLC [Member] | Rate Bill Credits [Member]
Other Commitments [Line Items]
Other Commitment	258,000,000
Pepco Holdings LLC [Member] | Rate Bill Credits [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	258,000,000
Pepco Holdings LLC [Member] | Rate Bill Credits [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	91,000,000
Pepco Holdings LLC [Member] | Rate Bill Credits [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	66,000,000
Pepco Holdings LLC [Member] | Rate Bill Credits [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	101,000,000
Pepco Holdings LLC [Member] | Energy Efficiency Program [Member]
Other Commitments [Line Items]
Other Commitment	122,000,000
Pepco Holdings LLC [Member] | Energy Efficiency Program [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Energy Efficiency Program [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Energy Efficiency Program [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Energy Efficiency Program [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Charitable Contributions [Member]
Other Commitments [Line Items]
Other Commitment	50,000,000
Pepco Holdings LLC [Member] | Charitable Contributions [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	50,000,000
Pepco Holdings LLC [Member] | Charitable Contributions [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	28,000,000
Pepco Holdings LLC [Member] | Charitable Contributions [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	12,000,000
Pepco Holdings LLC [Member] | Charitable Contributions [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	10,000,000
Pepco Holdings LLC [Member] | Delivery System Modernization [Member]
Other Commitments [Line Items]
Other Commitment	22,000,000
Pepco Holdings LLC [Member] | Delivery System Modernization [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Delivery System Modernization [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Delivery System Modernization [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Delivery System Modernization [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Green Sustainability Fund [Member]
Other Commitments [Line Items]
Other Commitment	14,000,000
Pepco Holdings LLC [Member] | Green Sustainability Fund [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Green Sustainability Fund [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Green Sustainability Fund [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Green Sustainability Fund [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Workforce Development [Member]
Other Commitments [Line Items]
Other Commitment	17,000,000
Pepco Holdings LLC [Member] | Workforce Development [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Workforce Development [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Workforce Development [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Workforce Development [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	0
Pepco Holdings LLC [Member] | Other1 [Member]
Other Commitments [Line Items]
Other Commitment	30,000,000
Pepco Holdings LLC [Member] | Other1 [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	14,000,000
Pepco Holdings LLC [Member] | Other1 [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	7,000,000
Pepco Holdings LLC [Member] | Other1 [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	7,000,000
Pepco Holdings LLC [Member] | Other1 [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	$ 0

Mergers, Acquisitions, and Di50

Mergers, Acquisitions, and Dispositions Merger Transaction Table (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 24, 2016
Payments to Acquire Businesses, Gross		$ 212	$ 6,645
Pepco Holdings LLC [Member]
Business Acquisition, Share Price				$ 27.25
Pepco Holdings LLC [Member] | Common Stock [Member]
Payments to Acquire Businesses, Gross	$ 6,933
Pepco Holdings LLC [Member] | Preferred Stock [Member]
Payments to Acquire Businesses, Gross	180
Pepco Holdings LLC [Member] | Deferred Compensation, Share-based Payments [Member]
Payments to Acquire Businesses, Gross	$ 29

Mergers, Acquisitions, and Di51

Mergers, Acquisitions, and Dispositions Purchase Price Allocation Table (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Business Acquisition [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Amount		$ 226	$ 0
Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets	[1]	1,441
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	[1]	11,088
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRegulatedAssets	[1]	5,015
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets	[1]	248
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	[1]	21,797
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities	[1]	(2,752)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities	[1]	(1,515)
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRegulatedLiabilities	[1]	297
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	[1]	5,636
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other	[1]	(187)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	[1]	14,655
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	[1]	7,142
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets	[1]	4,005
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent	[1]	3,447
_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRetirmentObligations	[1]	821
Fitzpatrick [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets		58
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		278
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Assets	[2]	114
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		1,257
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities		(7)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities		(417)
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRegulatedLiabilities		110
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other		(11)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		738
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		519
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities Noncurrent		144
_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRetirmentObligations		49
Business Combination, Consideration Transferred		293
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Assets		807
Business Combination, Bargain Purchase, Gain Recognized, Amount		226
Cash and Cash Equivalents [Member] | Fitzpatrick [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		110
Business Combination, Consideration Transferred, Other		129
Nuclear Fuel [Member] | Fitzpatrick [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Other		54
Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets		1,700
Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets		$ 1,100
[1]	Amounts shown reflect the final purchase price allocation and the correction of a reporting error identified and corrected in the second quarter of 2016. The error had resulted in a gross up of certain assets and liabilities related to legacy PHI intercompany and income tax receivable and payable balances.
[2]	Includes a $110 million asset associated with a contractual right to reimbursement from the New York Power Authority (NYPA), a prior owner of FitzPatrick, associated with the DOE one-time fee obligation. See Note 24-Commitments and Contingencies of the Exelon 2016 Form 10-K for additional background regarding SNF obligations to the DOE.

Mergers, Acquisitions, and Di52

Mergers, Acquisitions, and Dispositions Goodwill Amortization Schedule (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 6,677	$ 6,677
Exelon Generation Co L L C [Member]
Goodwill [Line Items]
Goodwill	$ 47	$ 47

Mergers, Acquisitions, and Di53

Mergers, Acquisitions, and Dispositions ProForma Impact of Merger (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016		Dec. 31, 2016
Business Acquisition, Pro Forma Revenue		$ 8,556	[1]	$ 32,342	[2]
Business Acquisition, Pro Forma Net Income (Loss)		$ 577	[1]	$ 1,562	[2]
Business Acquisition, Pro Forma Earnings Per Share, Basic		$ 0.63	[1]	$ 1.69	[2]
Business Acquisition, Pro Forma Earnings Per Share, Diluted		$ 0.62	[1]	$ 1.69	[2]
Noncash Merger Related Costs		$ 503
Consolidation, Eliminations [Member]
BusinessCombinationProformaIntercompanyRevenue		170
Business Acquisition, Pro Forma Revenue				$ 171
Noncash Merger Related Costs	$ 680	$ 639
[1]	The amounts above include adjustments for non-recurring costs directly related to the merger of $639 million and intercompany revenue of $170 million for the three months ended March 31, 2016.
[2]	The amounts above include adjustments for non-recurring costs directly related to the merger of $680 million and intercompany revenue of $171 million for the year ended December 31, 2016.

Mergers, Acquisitions, and Di54

Mergers, Acquisitions, and Dispositions Merger Integration Related Costs Table (Details) - USD ($) $ in Millions		Mar. 31, 2016	Mar. 31, 2017		Mar. 31, 2016		Mar. 23, 2016
Business Combination, Integration Related Costs	[1],[2]		$ 9		$ 102
Exelon Generation Co L L C [Member]
Business Combination, Integration Related Costs	[2]		9		16
Commonwealth Edison Co [Member]
Business Combination, Integration Related Costs	[2]		0		(8)	[3]
PECO Energy Co [Member]
Business Combination, Integration Related Costs	[2]		1		2
Baltimore Gas and Electric Company [Member]
Business Combination, Integration Related Costs	[2]		2		2
Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs	[2]		1		27
Delmarva Power and Light Company [Member]
Business Combination, Integration Related Costs	[2]		(7)	[4]	16
Atlantic City Electric Company [Member]
Business Combination, Integration Related Costs	[2]		1		13
Successor [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs		$ 56	(5)
Predecessor [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs							$ 29
Regulatory Assets [Member] | Commonwealth Edison Co [Member]
Business Combination, Integration Related Costs					$ 9
Regulatory Assets [Member] | Delmarva Power and Light Company [Member]
Business Combination, Integration Related Costs			$ 8
[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]	For the three months ended March 31, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $9 million, incurred at ComEd that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[4]	For the three months ended March 31, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, incurred at DPL that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details) GWh in Millions		Dec. 31, 2030	May 31, 2014USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)GWh		Dec. 31, 2016USD ($)		Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)		Jun. 30, 2015USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2017	Dec. 31, 2016USD ($)		Jun. 01, 2019	Jun. 01, 2018	Jun. 01, 2017	Sep. 30, 2016USD ($)	Aug. 31, 2010USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					$ 11,381,000,000		$ 11,388,000,000								$ 11,388,000,000
Business Combination, Integration Related Costs	[1],[2]				9,000,000					$ 102,000,000
Capital Expenditures Incurred but Not yet Paid					(298,000,000)					(290,000,000)
Regulatory Liabilities					4,939,000,000		4,789,000,000								4,789,000,000
Regulatory assets					10,051,000,000		10,046,000,000								10,046,000,000
Regulatory Liability, Current					637,000,000		602,000,000								602,000,000
Other Commitment					3,212,000,000
Fair Value, Net Asset (Liability)					2,400,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					1,215,000,000		1,167,000,000								1,167,000,000
Business Combination, Integration Related Costs	[2]				0					(8,000,000)	[3]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount					11,000,000
Capital Expenditures Incurred but Not yet Paid					25,000,000					25,000,000
Regulatory Liabilities					3,803,000,000		3,698,000,000								3,698,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 44,000,000
Public Utilities, Interim Rate Increase (Decrease), Amount															$ (8,000,000)
Approved ROE					11.50%
Public Utilities, Requested Rate Increase (Decrease), Percentage					8.40%										8.34%
Regulatory assets					$ 1,032,000,000		977,000,000								$ 977,000,000
Regulatory Liability, Current					311,000,000		329,000,000								329,000,000
Other Commitment					219,000,000
SocialCarbonCost					16.50
NuclearFacilityPurchaseAmount					0.16
LowIncomeEnergyAssistanceContributionAnnual					$ 10,000,000
LowIncomeEnergyAssistanceContributionLength					5
Low Income Sector Consumption Reduction Targets Act 129 Phase II					0.10%
Renewable Energy Resources Cumulatively Increase					1.50%
DecouplingImpactOnOperatingRevenuesAndRegulatoryAssets					$ 16,000,000
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount					96,000,000		(18,000,000)								127,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount					78,000,000										134,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount					$ 18,000,000										$ 7,000,000
Requested Debt and Equity Return on Distribution					6.47%										6.45%
ICC Approved Rate Increase (Decrease), Amount					$ 18,000,000										$ 7,000,000
Commonwealth Edison Co [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
FutureEnergyEfficiencySpending					$ 250,000,000
Renewable Energy Resources Cumulatively Increase					11.50%
Commonwealth Edison Co [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
ResidentialCustomerRateIncrease					25.00%
CommercialAndIndustrialCustomerRateIncrease					1.30%
Renewable Energy Resources Cumulatively Increase					25.00%
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]
Regulatory Assets					$ 1,748,000,000		1,710,000,000								1,710,000,000
Business Combination, Integration Related Costs	[2]				1,000,000					2,000,000
Capital Expenditures Incurred but Not yet Paid					0					(65,000,000)
Regulatory Liabilities					691,000,000		644,000,000								644,000,000
Regulatory assets					1,708,000,000		1,681,000,000								1,681,000,000
Regulatory Liability, Current					161,000,000		127,000,000								127,000,000
Other Commitment					208,000,000
Total Projected Natural Gas LTIIP Spend					762,000,000							$ 534,000,000
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					690,000,000		712,000,000								712,000,000
Business Combination, Integration Related Costs	[2]				2,000,000					2,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount					26,000,000
Capital Expenditures Incurred but Not yet Paid					41,000,000					(4,000,000)
Regulatory Liabilities					161,000,000		160,000,000								160,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount					31,000,000
Estimated number of smart meters to be installed																					2,000,000
Total smart grid and smart meter investment grant amount																					$ 480,000,000
Reimbursements received from the DOE																					$ 200,000,000
Regulatory assets					$ 499,000,000		504,000,000								504,000,000
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint					10.50%
Regulatory Liability, Current					$ 67,000,000		50,000,000								50,000,000
Other Commitment					266,000,000
Proposed Capital Expenditure					8,000,000
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Business Combination, Integration Related Costs	[2]				9,000,000					16,000,000
Unregulated Operating Revenue					101,000,000
Customer Refund Liability, Noncurrent					20,000,000
Capital Expenditures Incurred but Not yet Paid					(354,000,000)					(234,000,000)
Customer Refund					20,000,000
License Costs					29,000,000
Other Commitment					2,404,000,000
Exelon Generation Co L L C [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation					3,000,000
Exelon Generation Co L L C [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation					7,000,000
PEPCO Holdings Inc [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment					36,000,000
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					852,000,000		852,000,000								852,000,000
Capital Expenditures Incurred but Not yet Paid					(6,000,000)					9,000,000
Regulatory Liabilities					29,000,000		31,000,000								31,000,000
Regulatory assets					$ 679,000,000		690,000,000								690,000,000
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint					10.50%
CapitalProjectFundedByEntity			$ 500,000,000		$ 250,000,000
Capital ProjectFundedByBonds			375,000,000		188,000,000
CapitalProjectFundedByAgency			125,000,000		62,000,000
Regulatory Liability, Current					10,000,000		11,000,000								11,000,000
Other Commitment					15,000,000
Projected Capital Expenditures			$ 1,000,000,000		500,000,000
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount					77,000,000		82,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount					69,000,000								$ 86,000,000
TaxAdjustmentIncludedInPublicUtilitiesRequestedRateIncreaseDecreaseAmount					$ 18,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage					10.10%				10.60%
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					$ 367,000,000		348,000,000								348,000,000
Business Combination, Integration Related Costs	[2]				(7,000,000)	[4]				16,000,000
Capital Expenditures Incurred but Not yet Paid					9,000,000					8,000,000
Regulatory Liabilities					142,000,000		140,000,000								140,000,000
Public Utilities, Interim Rate Increase (Decrease), Amount									$ 2,500,000
Regulatory assets					$ 301,000,000		289,000,000								289,000,000
Public Utilities, Requested Return on Equity, Percentage					9.70%				10.60%
Regulatory Liability, Current					$ 47,000,000		43,000,000								43,000,000
Other Commitment					$ 11,000,000
Requested ROE					9.70%				10.60%
Delmarva Power and Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount							10,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount									$ 22,000,000
Gas Revenues Increase Settlement																				$ 0.14
Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount					$ 31,500,000		30,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount					60,000,000				63,000,000
Public Utilities, Approved Rate Increase (Decrease), Amount					$ 38,000,000
Approved ROE					9.60%
ICC Approved Rate Increase (Decrease), Amount					$ 38,000,000
Delmarva Power and Light Company [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Projected Capital Expenditures					4,600,000
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					501,000,000		501,000,000								501,000,000
Business Combination, Integration Related Costs	[2]				1,000,000					13,000,000
Capital Expenditures Incurred but Not yet Paid					0					$ (9,000,000)
Regulatory Liabilities					25,000,000		25,000,000								25,000,000
Regulatory assets					407,000,000		405,000,000								405,000,000
Regulatory Liability, Current					25,000,000		25,000,000								25,000,000
Other Commitment					8,000,000
Proposed Capital Expenditure					29,000,000
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount					$ 70,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage					10.10%
Advanced Metering Infrastructure Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					$ 26,000,000		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					140,000,000
Under Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					71,000,000		89,000,000								89,000,000
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[5]				18,000,000		23,000,000								23,000,000
Business Combination, Integration Related Costs					8,000,000		8,000,000
Under Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					0		0								0
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[6]				19,000,000		38,000,000								38,000,000
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
Under Recovered Energy And Transmission Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[7]				5,000,000		5,000,000								5,000,000
Under Recovered Energy And Transmission Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[8]				23,000,000		17,000,000								17,000,000
Merger Integration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					32,000,000		25,000,000								25,000,000
Merger Integration Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets							0								0
Merger Integration Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					0		0								0
Merger Integration Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[9]				8,000,000		10,000,000		6,000,000				6,000,000		10,000,000
Merger Integration Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					11,000,000	[10]	11,000,000								11,000,000
Merger Integration Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[10]				13,000,000		4,000,000								4,000,000
Merger Integration Costs [Member] | Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					8,000,000
Other Income					5,000,000
Merger Integration Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					0		0								0
MergerIntegrationCostsToBeRecoveredInDelawareServiceTerritory [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[10]				8,000,000
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[10]				5,000,000
Under Recovered Distribution Service Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					211,000,000		188,000,000								188,000,000
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[11]				211,000,000		188,000,000								188,000,000
Business Combination, Integration Related Costs					10,000,000										11,000,000
Under Recovered Distribution Service Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					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
Under Recovered Distribution Service Costs [Member] | Potomac Electric Power Company [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
Under Recovered Distribution Service Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					0		0								0
AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					689,000,000		701,000,000								701,000,000
AMI Expenses [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					165,000,000		164,000,000								164,000,000
AMI Expenses [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					46,000,000		49,000,000								49,000,000
AMI Expenses [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					225,000,000		230,000,000	[12]							230,000,000	[12]
Regulatory assets					225,000,000		230,000,000								230,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets					52,000,000
AMI Expenses [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					170,000,000	[12]	174,000,000								174,000,000
AMI Expenses [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					83,000,000	[12]	84,000,000								84,000,000
AMI Expenses [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					0		0								0
Energy Efficiency And Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					596,000,000		621,000,000								621,000,000
Energy Efficiency And Demand Response Programs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					0		0								0
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
Energy Efficiency And Demand Response Programs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					269,000,000		285,000,000								285,000,000
Energy Efficiency And Demand Response Programs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					241,000,000		250,000,000								250,000,000
Energy Efficiency And Demand Response Programs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					84,000,000		85,000,000								85,000,000
Energy Efficiency And Demand Response Programs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					1,000,000		$ 0								$ 0
Legacy AMI [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets					$ 53,000,000				$ 56,000,000				$ 56,000,000
Subsequent Event [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
EnergyEfficiencyAnnualCumulativeSavings		21.50%												6.60%
RenewableEnergyRetailLoad																	100.00%	75.00%	50.00%
Subsequent Event [Member] | Delmarva Power and Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount				$ 4,900,000
Public Utilities, Requested Return on Equity, Percentage				9.70%
Requested ROE				9.70%
Subsequent Event [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Proposed Capital Expenditure				$ 32,000,000
[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]	For the three months ended March 31, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $9 million, incurred at ComEd that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[4]	For the three months ended March 31, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, incurred at DPL that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[5]	As of March 31, 2017, ComEd’s regulatory asset of $18 million included $10 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of March 31, 2017, ComEd’s regulatory liability of $38 million included $6 million related to over-recovered energy costs and $32 million associated with revenues received for renewable energy requirements. As of December 31, 2016, ComEd’s regulatory asset of $23 million included $15 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2016, ComEd’s regulatory liability of $60 million included $30 million related to over-recovered energy costs and $30 million associated with revenues received for renewable energy requirements.
[6]	As of March 31, 2017, PECO's regulatory liability of $66 million included $41 million related to over-recovered costs under the DSP program, $13 million related to the over-recovered natural gas costs under the PGC, $10 million related to over-recovered non-bypassable transmission service charges and $2 million related to over-recovered electric transmission costs. As of December 31, 2016, PECO's regulatory liability of $56 million included $34 million related to over-recovered costs under the DSP program, $10 million related to over-recovered non-bypassable transmission service charges, $8 million related to the over-recovered natural gas costs under the PGC and $4 million related to the over-recovered electric transmission costs.
[7]	As of March 31, 2017, Pepco's regulatory asset of $6 million included $2 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of March 31, 2017, Pepco's regulatory liability of $7 million included $2 million of over-recovered transmission costs and $5 million of over-recovered electric energy costs. As of December 31, 2016, Pepco's regulatory asset of $6 million related to under-recovered electric energy costs. As of December 31, 2016, Pepco's regulatory liability of $8 million included $5 million of over-recovered transmission costs and $3 million of over-recovered electric energy costs.
[8]	As of March 31, 2017, DPL's regulatory asset of $5 million related to under-recovered electric energy costs. As of March 31, 2017, DPL's regulatory liability of $12 million included $9 million of over-recovered electric energy costs, $1 million of over-recovered transmission costs, and $2 million of over-recovered gas cost. As of December 31, 2016, DPL's regulatory asset of $5 million included $1 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of December 31, 2016, DPL's regulatory liability of $5 million included $2 million of over-recovered electric energy costs and $3 million of over-recovered transmission costs.
[9]	As of March 31, 2017, ACE's regulatory asset of $23 million included $10 million of transmission costs recoverable through its FERC approved formula rate and $13 million of under-recovered electric energy costs. As of March 31, 2017, ACE's regulatory liability of $8 million included $2 million of over-recovered transmission costs and $6 million of over-recovered electric energy costs. As of December 31, 2016, ACE's regulatory asset of $17 million included $6 million of transmission costs recoverable through its FERC approved formula rate and $11 million of under-recovered electric energy costs. As of December 31, 2016, ACE's regulatory liability of $5 million included $4 million of over-recovered transmission costs and $1 million of over-recovered electric energy costs.
[10]	As of March 31, 2017, BGE's regulatory asset of $8 million included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order.
[11]	As of March 31, 2017, ComEd’s regulatory asset of $211 million was comprised of $158 million for the 2015 - 2017 annual reconciliations and $53 million related to significant one-time events including $17 million of deferred storm costs, $10 million of Constellation and PHI merger and integration related costs and $26 million of smart meter related costs. As of December 31, 2016, ComEd’s regulatory asset of $188 million was comprised of $134 million for the 2015 and 2016 annual reconciliations and $54 million related to significant one-time events, including $20 million of deferred storm costs and $11 million of Constellation and PHI merger and integration related costs, and $23 million of smart meter related costs. ComEd's 2015 annual reconciliation regulatory asset included a reduction of $8 million related to a ComEd-proposed refund to customers for the impact of changing its OSHA recordable rate for 2014 and 2015. See Note 4— Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information.
[12]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246OUQ2REY5QzBDOTYwNUNBMEEyNzM0RkVGRjBENjIxNzEM}

Regulatory Matters Regulatory M

Regulatory Matters Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions		Mar. 31, 2016	Mar. 31, 2017		Dec. 31, 2016		Jun. 30, 2016	Mar. 31, 2016		Mar. 23, 2016	Dec. 31, 2016
Regulatory Assets [Line Items]
Current			$ 1,330		$ 1,342						$ 1,342
Noncurrent			10,051		10,046						10,046
Regulatory Assets			11,381		11,388						11,388
Regulatory Liabilities			4,939		4,789						4,789
Business Combination, Integration Related Costs	[1],[2]		9					$ 102
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4,152	[3]	4,162						4,162
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			2,055		2,016						2,016
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			689		701						701
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			211		188						188
Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			122		124						124
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			797		812	[4]					812	[4]
Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Current			1,021
Regulatory Assets					1,085						1,085
Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4		5						5
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			116		111						111
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			296		305						305
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			63		56						56
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			285		260						260
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			71		89						89
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			39		36						36
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			8		10						10
Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets					7						7
Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			596		621						621
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			32		25						25
Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			46		49						49
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			76		27						27
Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7		8						8
Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets			33		34						34
Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			42		31						31
Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			123		138						138
CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets			11		11						11
AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			486		477						477
Under funded Benefit Post Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[3]		1,087
Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Current			183		190						190
Noncurrent			1,032		977						977
Regulatory Assets			1,215		1,167						1,167
Public Utilities, Interim Rate Increase (Decrease), Amount											(8)
Regulatory Liabilities			3,803		3,698						3,698
Business Combination, Integration Related Costs	[2]		0					(8)	[5]
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			22		22						22
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Commonwealth Edison Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			76	[6]	75						75
Commonwealth Edison Co [Member] | Recoverable Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			53		54						54
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			165		164						164
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[7]		211		188						188
Business Combination, Integration Related Costs			10								11
Commonwealth Edison Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			41		42						42
Commonwealth Edison Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Commonwealth Edison Co [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0						0
Commonwealth Edison Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Commonwealth Edison Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			82		76						76
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			271		278						278
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets			63		56						56
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets			282		258						258
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[8]		18		23						23
Business Combination, Integration Related Costs			8		8
Commonwealth Edison Co [Member] | Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			17		20						20
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
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
Commonwealth Edison Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			6		7						7
Business Combination, Integration Related Costs								9
Commonwealth Edison Co [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			26		23						23
Commonwealth Edison Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0						0
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] | Annual Reconciliations [Member]
Regulatory Assets [Line Items]
Regulatory Assets			158		134						134
Commonwealth Edison Co [Member] | ElectricTransmissionCostsUnderRecovery [Member]
Regulatory Assets [Line Items]
Regulatory Assets			10		15						15
PECO Energy Co [Member]
Regulatory Assets [Line Items]
Current			40		29						29
Noncurrent			1,708		1,681						1,681
Regulatory Assets			1,748		1,710						1,710
Regulatory Liabilities			691		644						644
Business Combination, Integration Related Costs	[2]		1					2
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1,617		1,583						1,583
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			46		49						49
PECO Energy Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
PECO Energy Co [Member] | Loss on Reacquired Debt [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] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Current			0
Regulatory Assets					0						0
PECO Energy Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
PECO Energy Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			22		23						23
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			25		26						26
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						0
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
PECO Energy Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets					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] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			8		9						9
PECO Energy Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0						0
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			17		7						7
PECO Energy Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
PECO Energy Co [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets			11		11						11
Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Current			191		208						208
Noncurrent			499		504						504
Regulatory Assets			690		712						712
Regulatory Liabilities			161		160						160
Business Combination, Integration Related Costs	[2]		2					2
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			39		38						38
Baltimore Gas and Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets			3		4						4
Baltimore Gas and Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			13		28						28
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 Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			101	[6]	98						98
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Noncurrent			225		230						230
Regulatory Assets			225		230	[9]					230	[9]
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] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7		7						7
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] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0						0
Baltimore Gas and Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4		5						5
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			12		12						12
Baltimore Gas and Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		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	[10]		19		38						38
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1		1						1
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			8		10						10
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets					7						7
Baltimore Gas and Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			269		285						285
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[11]		8		10		$ 6				10
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			5		5						5
Baltimore Gas and Electric Company [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			140
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[12]		31		3						3
Baltimore Gas and Electric Company [Member] | UnderRecoveredNaturalGasDecouplingRevenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			6		2						2
Baltimore Gas and Electric Company [Member] | Under-Recovered Electric Revenue Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets			25
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
Baltimore Gas and Electric Company [Member] | Legacy AMI [Member]
Regulatory Assets [Line Items]
Regulatory Assets			53				56
Baltimore Gas and Electric Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			32
Pepco Holdings LLC [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs	[2]		1					27
Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs										$ 29
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Current			653		653						653
Noncurrent			2,791		2,851						2,851
Regulatory Assets			3,444		3,504						3,504
Regulatory Liabilities			236		237						237
Business Combination, Integration Related Costs		$ 56	(5)
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	[3]	0						0
Pepco Holdings LLC [Member] | Deferred Income Tax Charge [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			261		260						260
Pepco Holdings LLC [Member] | AMI Expenses [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			253		258						258
Pepco Holdings LLC [Member] | Under Recovered Distribution Service Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Pepco Holdings LLC [Member] | Loss on Reacquired Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			80	[13]	81						81
Pepco Holdings LLC [Member] | Fair Value Of Long Term Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			658	[4]	671						671
Pepco Holdings LLC [Member] | Fair Value Of Supply Contract [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1,021	[14]	1,085						1,085
Pepco Holdings LLC [Member] | Employee Severance [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Pepco Holdings LLC [Member] | Asset Retirement Obligation Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Pepco Holdings LLC [Member] | Environmental Restoration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Pepco Holdings LLC [Member] | Under Recovered Uncollectible Accounts Expense [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Pepco Holdings LLC [Member] | Renewable Energy And Associated REC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			3		2						2
Pepco Holdings LLC [Member] | Under Recovered Energy And Transmission Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			34		28						28
Pepco Holdings LLC [Member] | Deferred Storm Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			38		35						35
Pepco Holdings LLC [Member] | Electric Generation Related Regulatory Asset [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						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] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			326		335						335
Pepco Holdings LLC [Member] | Merger Integration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			24		15						15
Pepco Holdings LLC [Member] | Regulatory Assets [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			27		29						29
Pepco Holdings LLC [Member] | Under Recovered Decoupling Revenue [Member] | Successor [Member]
Regulatory Assets [Line Items]
Current			45
Regulatory Assets					24						24
Pepco Holdings LLC [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7
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] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			33		34						34
Pepco Holdings LLC [Member] | Recoverable Vacation Pay [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			25		24						24
Pepco Holdings LLC [Member] | Stranded Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			123		138						138
Pepco Holdings LLC [Member] | AssetRemovalCosts [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets			486		477						477
Potomac Electric Power Company [Member]
Regulatory Assets [Line Items]
Current			173		162						162
Noncurrent			679		690						690
Regulatory Assets			852		852						852
Regulatory Liabilities			29		31						31
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			31		31						31
Potomac Electric Power Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets			2
Potomac Electric Power Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4
Potomac Electric Power Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	[3]	0						0
Potomac Electric Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			169	[6]	171						171
Potomac Electric Power Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			170	[9]	174						174
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] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			17		17						17
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] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Potomac Electric Power Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
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						6
Potomac Electric Power Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			12		12						12
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
Potomac Electric Power Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			241		250						250
Potomac Electric Power Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			11	[15]	11						11
Potomac Electric Power Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			21		22						22
Potomac Electric Power Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			36		21						21
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			33		34						34
Potomac Electric Power Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Potomac Electric Power Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Potomac Electric Power Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			136		134						134
Delmarva Power and Light Company [Member]
Regulatory Assets [Line Items]
Current			66		59						59
Noncurrent			301		289						289
Regulatory Assets			367		348						348
Public Utilities, Interim Rate Increase (Decrease), Amount							$ 2.5
Regulatory Liabilities			142		140						140
Business Combination, Integration Related Costs	[2]		(7)	[16]				16
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			21		20						20
Delmarva Power and Light Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets					1						1
Delmarva Power and Light Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			5		4						4
Delmarva Power and Light Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	[3]	0						0
Delmarva Power and Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			40	[6]	38						38
Delmarva Power and Light Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets			83	[9]	84						84
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] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			9		9						9
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] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Delmarva Power and Light Company [Member] | Asset Retirement Obligation Costs [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			1		0						0
Delmarva Power and Light Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[17]		5		5						5
Delmarva Power and Light Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7		5						5
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
Delmarva Power and Light Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			84		85						85
Delmarva Power and Light Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[15]		13		4						4
Delmarva Power and Light Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4		5						5
Business Combination, Integration Related Costs			8
Delmarva Power and Light Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Current			9
Regulatory Assets					3						3
Delmarva Power and Light Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7		8						8
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			15		14						14
Delmarva Power and Light Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Delmarva Power and Light Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			90		88						88
Atlantic City Electric Company [Member]
Regulatory Assets [Line Items]
Current			94		96						96
Noncurrent			407		405						405
Regulatory Assets			501		501						501
Regulatory Liabilities			25		25						25
Business Combination, Integration Related Costs	[2]		1					$ 13
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets			20		19						19
Atlantic City Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets			10		6						6
Atlantic City Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			13		11						11
Atlantic City Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0	[3]	0						0
Atlantic City Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets			52	[6]	51						51
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] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets			6		6						6
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						0
Atlantic City Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Atlantic City Electric Company [Member] | Asset Retirement Obligation Costs [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						2
Atlantic City Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[18]		23		17						17
Atlantic City Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			19		18						18
Atlantic City Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0
Atlantic City Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets					0						0
Atlantic City Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			1		0						0
Atlantic City Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
Atlantic City Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets			4		4						4
Atlantic City Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0		0						0
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						10
Atlantic City Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets			123		138						138
Atlantic City Electric Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets			$ 261		$ 255						$ 255
[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]	As of March 31, 2017 and December 31, 2016, the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $1,087 million established at the date of the PHI Merger related to unrecognized costs that are probable of regulatory recovery. The regulatory assets are amortized over periods from 3 to 15 years, depending on the underlying component. Pepco, DPL and ACE are currently recovering these costs through base rates. Pepco, DPL and ACE are not earning a return on the recovery of these costs in base rates.
[4]	.
[5]	For the three months ended March 31, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $9 million, incurred at ComEd that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[6]	As of March 31, 2017, includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $22 million, $39 million, $31 million, $21 million and $20 million for ComEd, BGE, Pepco, DPL and ACE, respectively. As of December 31, 2016, includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $22 million, $38 million, $31 million, $20 million and $19 million for ComEd, BGE, Pepco, DPL and ACE, respectively.
[7]	As of March 31, 2017, ComEd’s regulatory asset of $211 million was comprised of $158 million for the 2015 - 2017 annual reconciliations and $53 million related to significant one-time events including $17 million of deferred storm costs, $10 million of Constellation and PHI merger and integration related costs and $26 million of smart meter related costs. As of December 31, 2016, ComEd’s regulatory asset of $188 million was comprised of $134 million for the 2015 and 2016 annual reconciliations and $54 million related to significant one-time events, including $20 million of deferred storm costs and $11 million of Constellation and PHI merger and integration related costs, and $23 million of smart meter related costs. ComEd's 2015 annual reconciliation regulatory asset included a reduction of $8 million related to a ComEd-proposed refund to customers for the impact of changing its OSHA recordable rate for 2014 and 2015. See Note 4— Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information.
[8]	As of March 31, 2017, ComEd’s regulatory asset of $18 million included $10 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of March 31, 2017, ComEd’s regulatory liability of $38 million included $6 million related to over-recovered energy costs and $32 million associated with revenues received for renewable energy requirements. As of December 31, 2016, ComEd’s regulatory asset of $23 million included $15 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2016, ComEd’s regulatory liability of $60 million included $30 million related to over-recovered energy costs and $30 million associated with revenues received for renewable energy requirements.
[9]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246OUQ2REY5QzBDOTYwNUNBMEEyNzM0RkVGRjBENjIxNzEM}
[10]	As of March 31, 2017, PECO's regulatory liability of $66 million included $41 million related to over-recovered costs under the DSP program, $13 million related to the over-recovered natural gas costs under the PGC, $10 million related to over-recovered non-bypassable transmission service charges and $2 million related to over-recovered electric transmission costs. As of December 31, 2016, PECO's regulatory liability of $56 million included $34 million related to over-recovered costs under the DSP program, $10 million related to over-recovered non-bypassable transmission service charges, $8 million related to the over-recovered natural gas costs under the PGC and $4 million related to the over-recovered electric transmission costs.
[11]	As of March 31, 2017, ACE's regulatory asset of $23 million included $10 million of transmission costs recoverable through its FERC approved formula rate and $13 million of under-recovered electric energy costs. As of March 31, 2017, ACE's regulatory liability of $8 million included $2 million of over-recovered transmission costs and $6 million of over-recovered electric energy costs. As of December 31, 2016, ACE's regulatory asset of $17 million included $6 million of transmission costs recoverable through its FERC approved formula rate and $11 million of under-recovered electric energy costs. As of December 31, 2016, ACE's regulatory liability of $5 million included $4 million of over-recovered transmission costs and $1 million of over-recovered electric energy costs.
[12]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246QTMwMjk0OTRCOENBNTU2NkI1MzcxQjk3NDgwNEUyMzMM}
[13]	.
[14]	.
[15]	As of March 31, 2017, BGE's regulatory asset of $8 million included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order.
[16]	For the three months ended March 31, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million, incurred at DPL that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[17]	As of March 31, 2017, Pepco's regulatory asset of $6 million included $2 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of March 31, 2017, Pepco's regulatory liability of $7 million included $2 million of over-recovered transmission costs and $5 million of over-recovered electric energy costs. As of December 31, 2016, Pepco's regulatory asset of $6 million related to under-recovered electric energy costs. As of December 31, 2016, Pepco's regulatory liability of $8 million included $5 million of over-recovered transmission costs and $3 million of over-recovered electric energy costs.
[18]	As of March 31, 2017, DPL's regulatory asset of $5 million related to under-recovered electric energy costs. As of March 31, 2017, DPL's regulatory liability of $12 million included $9 million of over-recovered electric energy costs, $1 million of over-recovered transmission costs, and $2 million of over-recovered gas cost. As of December 31, 2016, DPL's regulatory asset of $5 million included $1 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of December 31, 2016, DPL's regulatory liability of $5 million included $2 million of over-recovered electric energy costs and $3 million of over-recovered transmission costs.

Regulatory Matters Regulatory57

Regulatory Matters Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		$ 637	$ 602
Noncurrent		4,302	4,187
Regulatory Liabilities		4,939	4,789
Regulatory Assets		11,381	11,388
Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		66	76
Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		48	47
Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,776	2,607
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,598	1,601
Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		39	39
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		185	185
Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8	8
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		18	20
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		133	134
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		65	72
Rate Stabilization Deferral [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		67	50
Noncurrent		94	110
Regulatory Liabilities		161	160
Regulatory Assets		690	712
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] | Abandonment costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Gas Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets			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] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Baltimore Gas and Electric Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		136	141
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] | 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	[1]	2	0
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		20	19
Baltimore Gas and Electric Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	3
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		82	79
Noncurrent		154	158
Regulatory Liabilities		236	237
Regulatory Assets		3,444	3,504
Pepco Holdings LLC [Member] | Electric Transmission And Distribution Tax Repairs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Pepco Holdings LLC [Member] | Nuclear Decommissioning [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Pepco Holdings LLC [Member] | Removal Costs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		134	136
Pepco Holdings LLC [Member] | Deferred Lease Revenue [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2]	39	39
Pepco Holdings LLC [Member] | Energy Efficiency Demand Response Programs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	3
Pepco Holdings LLC [Member] | Dlc Program Cost [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Pepco Holdings LLC [Member] | Gas Distribution Tax Repairs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Pepco Holdings LLC [Member] | Over Recovered Energy And Transmission Costs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		27	18
Pepco Holdings LLC [Member] | Regulatory Liabilities Other [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		34	41
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		161	127
Noncurrent		530	517
Regulatory Liabilities		691	644
Regulatory Assets		1,748	1,710
PECO Energy Co [Member] | Over Recovered NonBypassable Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		10
PECO Energy Co [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	4
PECO Energy Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		66	76
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
PECO Energy Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		482	438
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		44	41
PECO Energy Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8	8
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		18	20
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		66	56
PECO Energy Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		7	5
PECO Energy Co [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		13	8
PECO Energy Co [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			10
PECO Energy Co [Member] | Default Service Provider Program [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		41	34
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		311	329
Noncurrent		3,492	3,369
Regulatory Liabilities		3,803	3,698
Regulatory Assets		1,215	1,167
Commonwealth Edison Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Commonwealth Edison Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,294	2,169
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,328	1,324
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		139	141
Commonwealth Edison Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			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	[3]	38	60
Commonwealth Edison Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		4	4
Commonwealth Edison Co [Member] | Renewable energy Requirements [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		32	30
Commonwealth Edison Co [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		6	30
Potomac Electric Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		10	11
Noncurrent		19	20
Regulatory Liabilities		29	31
Regulatory Assets		852	852
Potomac Electric Power Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	5
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] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Potomac Electric Power Company [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Potomac Electric Power Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		17	18
Potomac Electric Power Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	3
Potomac Electric Power Company [Member] | Dlc Program Cost [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	[4]	7	8
Potomac Electric Power Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3	2
Potomac Electric Power Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		5	3
Delmarva Power and Light Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		47	43
Noncurrent		95	97
Regulatory Liabilities		142	140
Regulatory Assets		367	348
Delmarva Power and Light Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1	3
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] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Delmarva Power and Light Company [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Delmarva Power and Light Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		117	118
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] | 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]	12	5
Delmarva Power and Light Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		13	17
Delmarva Power and Light Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2
Delmarva Power and Light Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		9	2
Atlantic City Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		25	25
Noncurrent		0	0
Regulatory Liabilities		25	25
Regulatory Assets		501	501
Atlantic City Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	4
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] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	0
Atlantic City Electric Company [Member] | Nuclear Decommissioning [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	0
Atlantic City Electric Company [Member] | Dlc Program Cost [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	[6]	8	5
Atlantic City Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		17	20
Atlantic City Electric Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		6	1
Under-Recovered Electric Revenue Decoupling [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		25
Under Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		71	89
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	[1]	19	38
Under Recovered Energy And Transmission Costs [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		34	28
Under Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		0	0
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	[3]	18	23
Under Recovered Energy And Transmission Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		6	6
Under Recovered Energy And Transmission Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	[5]	5	5
Under Recovered Energy And Transmission Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets	[6]	23	17
UnderRecoveredNaturalGasDecouplingRevenue [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Assets		$ 6	$ 2
[1]	As of March 31, 2017, PECO's regulatory liability of $66 million included $41 million related to over-recovered costs under the DSP program, $13 million related to the over-recovered natural gas costs under the PGC, $10 million related to over-recovered non-bypassable transmission service charges and $2 million related to over-recovered electric transmission costs. As of December 31, 2016, PECO's regulatory liability of $56 million included $34 million related to over-recovered costs under the DSP program, $10 million related to over-recovered non-bypassable transmission service charges, $8 million related to the over-recovered natural gas costs under the PGC and $4 million related to the over-recovered electric transmission costs.
[2]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246NThDMDVEQzYxNzNFNTQ4RUJFNEFCOUVFNjQ1RDA3RDIM}
[3]	As of March 31, 2017, ComEd’s regulatory asset of $18 million included $10 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of March 31, 2017, ComEd’s regulatory liability of $38 million included $6 million related to over-recovered energy costs and $32 million associated with revenues received for renewable energy requirements. As of December 31, 2016, ComEd’s regulatory asset of $23 million included $15 million associated with transmission costs recoverable through its FERC approved formula rate and $8 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2016, ComEd’s regulatory liability of $60 million included $30 million related to over-recovered energy costs and $30 million associated with revenues received for renewable energy requirements.
[4]	As of March 31, 2017, BGE's regulatory asset of $19 million included $3 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $13 million related to under-recovered electric energy costs, and $3 million of abandonment costs to be recovered upon FERC approval. As of March 31, 2017, BGE's regulatory liability consisted of $2 million related to over-recovered natural gas costs. As of December 31, 2016, BGE’s regulatory asset of $38 million included $4 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $28 million related to under-recovered electric energy costs, $3 million of abandonment costs to be recovered upon FERC approval, and $3 million of under-recovered natural gas costs.
[5]	As of March 31, 2017, Pepco's regulatory asset of $6 million included $2 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of March 31, 2017, Pepco's regulatory liability of $7 million included $2 million of over-recovered transmission costs and $5 million of over-recovered electric energy costs. As of December 31, 2016, Pepco's regulatory asset of $6 million related to under-recovered electric energy costs. As of December 31, 2016, Pepco's regulatory liability of $8 million included $5 million of over-recovered transmission costs and $3 million of over-recovered electric energy costs.
[6]	As of March 31, 2017, DPL's regulatory asset of $5 million related to under-recovered electric energy costs. As of March 31, 2017, DPL's regulatory liability of $12 million included $9 million of over-recovered electric energy costs, $1 million of over-recovered transmission costs, and $2 million of over-recovered gas cost. As of December 31, 2016, DPL's regulatory asset of $5 million included $1 million of transmission costs recoverable through its FERC approved formula rate and $4 million of under-recovered electric energy costs. As of December 31, 2016, DPL's regulatory liability of $5 million included $2 million of over-recovered electric energy costs and $3 million of over-recovered transmission costs.

Regulatory Matters Regulatory58

Regulatory Matters Regulatory Matters - Purchase of Receivables Programs (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2017		Dec. 31, 2016
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 305		$ 313
Allowance for Doubtful Accounts Receivable		(36)	[1]	(37)
Payments to Acquire Other Receivables, Net		269		276
Commonwealth Edison Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		85		87
Allowance for Doubtful Accounts Receivable		(14)	[1]	(14)
Payments to Acquire Other Receivables, Net		71		73
PECO Energy Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		72		72
Allowance for Doubtful Accounts Receivable	[2]	(7)		(6)
Payments to Acquire Other Receivables, Net		65		66
Baltimore Gas and Electric Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		59		59
Allowance for Doubtful Accounts Receivable	[1]	(4)		(4)
Payments to Acquire Other Receivables, Net		55		55	[3]
PEPCO Holdings Inc [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		89		95
Allowance for Doubtful Accounts Receivable	[1]	(11)		(13)
Payments to Acquire Other Receivables, Net		78		82
Potomac Electric Power Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		58		63
Allowance for Doubtful Accounts Receivable	[4]	(6)		(7)
Payments to Acquire Other Receivables, Net		$ 52		56
Potomac Electric Power Company [Member] | Maryland Service Territory [Member] | Minimum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		0.00%
Potomac Electric Power Company [Member] | Maryland Service Territory [Member] | Maximum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		2.00%
Potomac Electric Power Company [Member] | District of Columbia Service Territory [Member] | Minimum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		0.00%
Potomac Electric Power Company [Member] | District of Columbia Service Territory [Member] | Maximum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		6.00%
Delmarva Power and Light Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 10		10
Allowance for Doubtful Accounts Receivable	[1]	(2)		(2)
Payments to Acquire Other Receivables, Net		$ 8		8
Delmarva Power and Light Company [Member] | Maryland Service Territory [Member] | Minimum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		0.00%
Delmarva Power and Light Company [Member] | Maryland Service Territory [Member] | Maximum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		1.00%
Atlantic City Electric Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 21		22
Allowance for Doubtful Accounts Receivable	[1]	(3)		(4)
Payments to Acquire Other Receivables, Net		$ 18		$ 18
[1]	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]	.
[3]	As of March 31, 2017, PECO's regulatory liability of $66 million included $41 million related to over-recovered costs under the DSP program, $13 million related to the over-recovered natural gas costs under the PGC, $10 million related to over-recovered non-bypassable transmission service charges and $2 million related to over-recovered electric transmission costs. As of December 31, 2016, PECO's regulatory liability of $56 million included $34 million related to over-recovered costs under the DSP program, $10 million related to over-recovered non-bypassable transmission service charges, $8 million related to the over-recovered natural gas costs under the PGC and $4 million related to the over-recovered electric transmission costs.
[4]	Pepco's electric POR program in Maryland included a discount on purchased receivables ranging from 0% to 2% depending on customer class, and Pepco's electric POR program in the District of Columbia included a discount on purchased receivables ranging from 0% to 6% depending on customer class. DPL's electric POR program in Maryland included a discount on purchased receivables ranging from 0% to 1% depending on customer class.

Regulatory Matters Annual Elect

Regulatory Matters Annual Electric Transmission Fillings (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 44
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 11
Public Utilities, Approved Return on Equity, Percentage	11.50%
Public Utilities, Approved Equity Capital Structure, Percentage	8.43%
Prior Year Revenue Adjustment	$ (33)
Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	31
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 26
Public Utilities, Approved Return on Equity, Percentage	10.50%
Public Utilities, Approved Equity Capital Structure, Percentage	7.47%
Prior Year Revenue Adjustment	$ 3
Proposed Capital Expenditure	$ (8)
Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Approved Return on Equity, Percentage	10.50%
Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Proposed Capital Expenditure	$ (29)

Regulatory Matters Capitalized

Regulatory Matters Capitalized Ratemaking Amount Not Recognized (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	$ 71	$ 72
Commonwealth Edison Co [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	5	5
PECO Energy Co [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	0	0
Baltimore Gas and Electric Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	56	57
Pepco Holdings LLC [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	10	10
Potomac Electric Power Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	6	6
Delmarva Power and Light Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	4	4
Atlantic City Electric Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	$ 0	$ 0

Impairment of Long-Lived Asse61

Impairment of Long-Lived Assets (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Sep. 30, 2016	Mar. 31, 2017	Mar. 31, 2016
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Proceeds from Long-term Capital Lease Obligations			$ 360
Estimated residual value of leased assets			356
Proceeds From Lease Termination		$ 0	360
Gain (Loss) on Contract Termination			4
Constellation Energy Group LLC [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Tangible Asset Impairment Charges	$ 15		$ 119

Early Nuclear Plant Retiremen62

Early Nuclear Plant Retirements Early Nuclear Plant Retirements (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	$ 1,312	$ 1,274
Property, plant and equipment, net	72,630	$ 71,555
Three Mile Island [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	40
Nuclear Fuel, Net of Amortization	72
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	40
Asset Retirement Obligation	(572)
Property, plant and equipment, net	$ 1,000

Early Nuclear Plant Retiremen63

Early Nuclear Plant Retirements Early Plant Retirement Pretax Expense (Details) - USD ($) $ in Millions		3 Months Ended					12 Months Ended
		Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016
Depreciation	[1]	$ 754				$ 606
Other Cost and Expense, Operating		2,460				2,835
Other, net		$ 283				$ 114
Nuclear Plant [Member]
Nuclear Fuel Amortization			$ 23	$ 28	$ 9		$ 60
Depreciation			253	344	115		712
Other Cost and Expense, Operating			(120)	5	141		26
Accretion Expense, Including Asset Retirement Obligations			0	2	0		2
Other, net			(31)	(41)	(14)		(86)
Other Expenses			$ 125	$ 338	$ 251		714
Facility Closing [Member]
Other Expenses							$ 714
[1]	(a)Included in Depreciation and amortization on the Registrants' Consolidated Statements of Operations and Comprehensive Income.

Fair Value of Financial Asset64

Fair Value of Financial Assets and Liabilities - Fair Value of Financial Liabilities Recorded at the Carrying Amount (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Spent Nuclear Fuel Obligation, Noncurrent		$ 1,136	$ 1,024
Due to Related Parties, Noncurrent		641	641
Deferred Finance Costs, Net		199	200
Financing Trusts [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		7	7
Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		2,048	1,267
Long-term debt (including amounts due within one year)(a)	[1]	34,689	34,005
Spent Nuclear Fuel Obligation, Noncurrent		1,136	1,024
Due to Related Parties, Noncurrent	[2]	641	641
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		2,048	1,267
Long-term debt (including amounts due within one year)(a)	[1]	35,659	34,813
Spent Nuclear Fuel Obligation, Noncurrent		813	732
Due to Related Parties, Noncurrent	[2]	677	667
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year)(a)	[1]	1,135	1,113
Spent Nuclear Fuel Obligation, Noncurrent		0	0
Due to Related Parties, Noncurrent	[2]	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		2,048	1,267
Long-term debt (including amounts due within one year)(a)	[1]	32,562	31,741
Spent Nuclear Fuel Obligation, Noncurrent		813	732
Due to Related Parties, Noncurrent	[2]	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year)(a)	[1]	1,962	1,959
Spent Nuclear Fuel Obligation, Noncurrent		0	0
Due to Related Parties, Noncurrent	[2]	677	667
Exelon Generation Co L L C [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Spent Nuclear Fuel Obligation, Noncurrent		1,136	1,024
Deferred Finance Costs, Net		67	64
Exelon Generation Co L L C [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		717	699
Long-term debt (including amounts due within one year)(a)	[1]	9,979	9,241
Spent Nuclear Fuel Obligation, Noncurrent		1,136	1,024
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		717	699
Long-term debt (including amounts due within one year)(a)	[1]	9,871	9,152
Spent Nuclear Fuel Obligation, Noncurrent		813	732
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
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]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		717	699
Long-term debt (including amounts due within one year)(a)	[1]	8,200	7,482
Spent Nuclear Fuel Obligation, Noncurrent		813	732
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year)(a)	[1]	1,671	1,670
Spent Nuclear Fuel Obligation, Noncurrent		0	0
Commonwealth Edison Co [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Due to Related Parties, Noncurrent		205	205
Deferred Finance Costs, Net		45	46
Commonwealth Edison Co [Member] | Financing Trusts [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		1	1
Commonwealth Edison Co [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		365
Long-term debt (including amounts due within one year)(a)	[1]	7,035	7,033
Due to Related Parties, Noncurrent	[2]	205	205
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		365
Long-term debt (including amounts due within one year)(a)	[1]	7,615	7,585
Due to Related Parties, Noncurrent	[2]	218	215
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
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]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		365
Long-term debt (including amounts due within one year)(a)	[1]	7,615	7,585
Due to Related Parties, Noncurrent	[2]	0	0
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
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]	218	215
PECO Energy Co [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Due to Related Parties, Noncurrent		184	184
Deferred Finance Costs, Net		15	15
PECO Energy Co [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
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]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)	[1]	2,806	2,794
Due to Related Parties, Noncurrent		193	192
PECO Energy Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
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]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)	[1]	2,806	2,794
Due to Related Parties, Noncurrent		0	0
PECO Energy Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)	[1]	0	0
Due to Related Parties, Noncurrent		193	192
Baltimore Gas and Electric Company [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Due to Related Parties, Noncurrent		252	252
Deferred Finance Costs, Net		14	15
Baltimore Gas and Electric Company [Member] | Financing Trusts [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		6	6
Baltimore Gas and Electric Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		95	45
Long-term debt (including amounts due within one year)(a)	[1]	2,323	2,322
Due to Related Parties, Noncurrent	[2]	252	252
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		95	45
Long-term debt (including amounts due within one year)(a)	[1]	2,501	2,467
Due to Related Parties, Noncurrent	[2]	266	260
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
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]	0	0
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		95	45
Long-term debt (including amounts due within one year)(a)	[1]	2,501	2,467
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]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
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]	266	260
Pepco Holdings LLC [Member] | Successor [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		2	2
Pepco Holdings LLC [Member] | Reported Value Measurement [Member] | Successor [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		167	522
Long-term debt (including amounts due within one year)(a)	[1]	5,860	5,898
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Successor [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		167	522
Long-term debt (including amounts due within one year)(a)	[1]	5,801	5,809
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member] | Successor [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year)(a)	[1]	0	0
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member] | Successor [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		167	522
Long-term debt (including amounts due within one year)(a)	[1]	5,510	5,520
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member] | Successor [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year)(a)	[1]	291	289
Potomac Electric Power Company [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		29	30
Potomac Electric Power Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		167	23
Long-term debt (including amounts due within one year)(a)	[1]	2,350	2,349
Potomac Electric Power Company [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		167	23
Long-term debt (including amounts due within one year)(a)	[1]	2,813	2,796
Potomac Electric Power Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
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]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		167	23
Long-term debt (including amounts due within one year)(a)	[1]	2,804	2,788
Potomac Electric Power Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		0	0
Long-term debt (including amounts due within one year)(a)	[1]	9	8
Delmarva Power and Light Company [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		11	11
Delmarva Power and Light Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)	[1]	1,326	1,340
Delmarva Power and Light Company [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)	[1]	1,374	1,383
Delmarva Power and Light Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
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]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)	[1]	1,374	1,383
Delmarva Power and Light Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)	[1]	0	0
Atlantic City Electric Company [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		5	6
Atlantic City Electric Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)		1,145	1,155
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)		1,271	1,287
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)		0	0
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)		989	1,007
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)(a)		$ 282	$ 280
[1]	Includes unamortized debt issuance costs which are not fair valued of $199 million, $67 million, $45 million, $15 million, $14 million, $2 million, $29 million, $11 million, and $5 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of March 31, 2017. Includes unamortized debt issuance costs 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.
[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 March 31, 2017 and December 31, 2016.

Fair Value of Financial Asset65

Fair Value of Financial Assets and Liabilities - Fair Value Measurements of Assets and Liabilities, Recurring and Nonrecurring (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
Derivative Asset, Notional Amount		$ 886	$ 933
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Margin Deposit Assets		(14)	(158)
Derivative Liability, Noncurrent		420	392
Derivative Liability, Current		228	282
Derivative, Collateral, Right to Reclaim Cash		1	29
Derivative Asset, Notional Amount		886	933
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		(1)	(2)
Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		381	360
Cash and Cash Equivalents, Fair Value Disclosure		381	360
Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		165	180
Cash and Cash Equivalents, Fair Value Disclosure		165	180
Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		25	25
Cash and Cash Equivalents, Fair Value Disclosure		25	25
Nuclear Decommissioning Trust Fund Investments [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments		8	(31)
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	342	373
Cash and Cash Equivalents, Fair Value Disclosure	[1]	342	373
FinancialAssetsFairValueDisclosure1		14,451	13,253
Deferred Compensation Liability, Current and Noncurrent		(135)	(136)
Financial Liabilities Fair Value Disclosure		(783)	(810)
FinancialAssetLiabilitiesNetFairValueDisclosure1		13,668	12,443
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		3,266	3,113
Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(637)	(662)
Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(5,091)	(4,697)
Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(77)	(79)
Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(11)	(12)
Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(25)	(21)
Fair Value, Measurements, Recurring [Member] | ProprietaryTradingLiabilitiesInterestandFX [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(3)	(4)
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]
Total mark-to-market derivative liabilities	[2]	4,531	4,114
Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(1)	(10)
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]
Total mark-to-market derivative liabilities		18	23
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		2,004	1,804
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	[3]	12,354	11,092
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[3]	3,222	3,049
Fair Value, Measurements, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	181	129
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		6,708	6,014
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		2,089	2,011
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		158	148
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		158	148
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		57	37
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		1,551	1,320
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		9	17
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]	536	552
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[5]	484	493
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		427	326
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		427	326
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		22	28
Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,366	1,381
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		241	264
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]	95	113
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[6]	44	64
Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		21	11
Cash and Cash Equivalents, Fair Value Disclosure		21	11
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		1	2
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		64	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		44	64
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		4,389	3,977
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		484	493
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		491	498
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		64	71
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		234	224
Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		80	74
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		15	16
Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		53	50
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		86	84
Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		40	42
Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		80	76
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]	(4,089)	(3,787)
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		20	28
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		12	16
Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		5,375	5,092
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		4	5
Fair Value, Measurements, Recurring [Member] | Effectsofnettingandallocationofcollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		(18)	(21)
Fair Value, Inputs, Level 1 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties		75	71
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	342	373
Cash and Cash Equivalents, Fair Value Disclosure	[1]	342	373
FinancialAssetsFairValueDisclosure1		6,407	5,674
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(78)	(37)
FinancialAssetLiabilitiesNetFairValueDisclosure1		6,329	5,637
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]
Total mark-to-market derivative liabilities		(79)	(37)
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]
Total mark-to-market derivative liabilities		(787)	(1,267)
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]
Total mark-to-market derivative liabilities		(6)	(3)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		1	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]
Total mark-to-market derivative liabilities		0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | ProprietaryTradingLiabilitiesInterestandFX [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(3)	(4)
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]
Total mark-to-market derivative liabilities	[2]	714	1,233
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]
Total mark-to-market derivative liabilities		0	0
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]
Total mark-to-market derivative liabilities		4	4
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] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[3]	5,789	4,952
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]
Investments, Fair Value Disclosure	[4]	160	110
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		4,113	3,551
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] | 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] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,516	1,291
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		8	16
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] | 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] | 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] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		115	197
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] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	29	27
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 equivalents		21	11
Cash and Cash Equivalents, Fair Value Disclosure		21	11
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	0
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] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,516	1,291
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] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		133	124
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		80	74
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
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		53	50
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 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] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		5	3
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]	(641)	(1,164)
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)	1
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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		751	1,358
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	3
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		(4)	(2)
Fair Value, Inputs, Level 2 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties		271	197
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	0	0
Cash and Cash Equivalents, Fair Value Disclosure	[1]	0	0
FinancialAssetsFairValueDisclosure1		3,232	2,937
Deferred Compensation Liability, Current and Noncurrent		(135)	(136)
Financial Liabilities Fair Value Disclosure		(205)	(237)
FinancialAssetLiabilitiesNetFairValueDisclosure1		3,027	2,700
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]
Total mark-to-market derivative liabilities		(58)	(89)
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]
Total mark-to-market derivative liabilities		(2,855)	(2,378)
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]
Total mark-to-market derivative liabilities		(49)	(50)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(12)	(12)
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]
Total mark-to-market derivative liabilities		(25)	(21)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | ProprietaryTradingLiabilitiesInterestandFX [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		0	0
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]
Total mark-to-market derivative liabilities	[2]	2,846	2,339
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]
Total mark-to-market derivative liabilities		(1)	(10)
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]
Total mark-to-market derivative liabilities		14	19
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		1,749	1,554
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	[3]	2,660	2,414
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]
Investments, Fair Value Disclosure	[4]	21	19
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		505	452
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] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		57	37
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		35	29
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	1
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]	52	59
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] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		22	28
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		468	413
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		241	264
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]	2	3
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 equivalents		0	0
Cash and Cash Equivalents, Fair Value Disclosure		0	0
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		1	2
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] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		2,134	1,943
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] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		81	80
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
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		15	16
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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		66	64
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] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		50	50
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]	(2,575)	(2,142)
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		21	27
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		12	16
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		2,993	2,505
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		1	2
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		(14)	(19)
Fair Value, Inputs, Level 3 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties		98	61
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	0	0
Cash and Cash Equivalents, Fair Value Disclosure	[1]	0	0
FinancialAssetsFairValueDisclosure1		1,546	1,529
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(500)	(536)
FinancialAssetLiabilitiesNetFairValueDisclosure1		1,046	993
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]
Total mark-to-market derivative liabilities		(500)	(536)
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]
Total mark-to-market derivative liabilities		(1,449)	(1,052)
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]
Total mark-to-market derivative liabilities		(22)	(26)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		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]
Total mark-to-market derivative liabilities		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | ProprietaryTradingLiabilitiesInterestandFX [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		0	0
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]
Total mark-to-market derivative liabilities	[2]	971	542
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]
Total mark-to-market derivative liabilities		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]
Total mark-to-market derivative liabilities		0	0
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		255	250
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	[3]	683	677
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]
Investments, Fair Value Disclosure	[4]	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		1	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] | 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] | 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] | 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] | 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] | 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] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		783	771
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] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	20	19
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 equivalents		0	0
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] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20	19
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		255	250
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	427
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	20
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
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
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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20	20
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		40	42
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		25	23
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]	(873)	(481)
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] | 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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,631	1,229
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
Exelon Generation Co L L C [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		157	153
Derivative Liability, Current		209	263
Exelon Generation Co L L C [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		267	252
Cash and Cash Equivalents, Fair Value Disclosure		267	252
Exelon Generation Co L L C [Member] | Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		138	157
Cash and Cash Equivalents, Fair Value Disclosure		138	157
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	135	39
Cash and Cash Equivalents, Fair Value Disclosure	[1]	135	39
FinancialAssetsFairValueDisclosure1		14,045	12,718
Deferred Compensation Liability, Current and Noncurrent		(35)	(34)
Financial Liabilities Fair Value Disclosure		(401)	(450)
FinancialAssetLiabilitiesNetFairValueDisclosure1		13,644	12,268
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		3,266	3,113
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]
Total mark-to-market derivative liabilities		(355)	(404)
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]
Total mark-to-market derivative liabilities		(4,809)	(4,439)
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]
Total mark-to-market derivative liabilities		(77)	(79)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(11)	(12)
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]
Total mark-to-market derivative liabilities		(25)	(21)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | ProprietaryTradingLiabilitiesInterestandFX [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(3)	(4)
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]
Total mark-to-market derivative liabilities	[2]	4,531	4,114
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]
Total mark-to-market derivative liabilities		(1)	(10)
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]
Total mark-to-market derivative liabilities		18	23
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		2,004	1,804
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]
Investments, Fair Value Disclosure	[3]	12,354	11,092
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[3]	3,222	3,049
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]
Investments, Fair Value Disclosure	[4]	181	129
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]
Investments, Fair Value Disclosure		6,708	6,014
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		2,089	2,011
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]
Investments, Fair Value Disclosure		158	148
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		158	148
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		57	37
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		1,551	1,320
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		9	17
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]
Investments, Fair Value Disclosure	[5]	536	552
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[5]	484	493
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]
Investments, Fair Value Disclosure		427	326
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		427	326
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		22	28
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		1,366	1,381
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		241	264
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]
Investments, Fair Value Disclosure	[6]	95	113
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure	[6]	44	64
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 equivalents		21	11
Cash and Cash Equivalents, Fair Value Disclosure		21	11
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		1	2
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]
Investments, Fair Value Disclosure		64	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		44	64
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]
Investments, Fair Value Disclosure		4,389	3,977
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		484	493
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]
Investments, Fair Value Disclosure		491	498
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Alternative Investments, Fair Value Disclosure		64	71
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		47	39
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		7	2
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	0
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		20	19
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		20	18
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		40	42
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		80	76
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]	(4,087)	(3,785)
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		8	12
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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		5,373	5,090
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		4	5
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		(18)	(21)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	135	39
Cash and Cash Equivalents, Fair Value Disclosure	[1]	135	39
FinancialAssetsFairValueDisclosure1		6,094	5,237
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(78)	(37)
FinancialAssetLiabilitiesNetFairValueDisclosure1		6,016	5,200
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]
Total mark-to-market derivative liabilities		(79)	(37)
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]
Total mark-to-market derivative liabilities		(787)	(1,267)
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]
Total mark-to-market derivative liabilities		(6)	(3)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		1	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]
Total mark-to-market derivative liabilities		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | ProprietaryTradingLiabilitiesInterestandFX [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(3)	(4)
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]
Total mark-to-market derivative liabilities	[2]	714	1,233
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]
Total mark-to-market derivative liabilities		0	0
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]
Total mark-to-market derivative liabilities		4	4
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] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[3]	5,789	4,952
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]
Investments, Fair Value Disclosure	[4]	160	110
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		4,113	3,551
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] | 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] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,516	1,291
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		8	16
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] | 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] | 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] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		115	197
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] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	29	27
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 equivalents		21	11
Cash and Cash Equivalents, Fair Value Disclosure		21	11
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	0
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] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,516	1,291
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] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		27	21
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		7	2
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	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		20	19
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 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] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		5	3
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]	(639)	(1,162)
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)	1
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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		749	1,356
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	3
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		(4)	(2)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	0	0
Cash and Cash Equivalents, Fair Value Disclosure	[1]	0	0
FinancialAssetsFairValueDisclosure1		3,159	2,859
Deferred Compensation Liability, Current and Noncurrent		(35)	(34)
Financial Liabilities Fair Value Disclosure		(105)	(135)
FinancialAssetLiabilitiesNetFairValueDisclosure1		3,054	2,724
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]
Total mark-to-market derivative liabilities		(58)	(89)
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]
Total mark-to-market derivative liabilities		(2,855)	(2,378)
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]
Total mark-to-market derivative liabilities		(49)	(50)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		(12)	(12)
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]
Total mark-to-market derivative liabilities		(25)	(21)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | ProprietaryTradingLiabilitiesInterestandFX [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		0	0
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]
Total mark-to-market derivative liabilities	[2]	2,846	2,339
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]
Total mark-to-market derivative liabilities		(1)	(10)
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]
Total mark-to-market derivative liabilities		14	19
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		1,749	1,554
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	[3]	2,660	2,414
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]
Investments, Fair Value Disclosure	[4]	21	19
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		505	452
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] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		57	37
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		35	29
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	1
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]	52	59
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] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		22	28
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		468	413
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		241	264
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]	2	3
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 equivalents		0	0
Cash and Cash Equivalents, Fair Value Disclosure		0	0
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		1	2
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] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		2,134	1,943
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] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20	18
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	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	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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20	18
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] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		50	50
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]	(2,575)	(2,142)
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		9	11
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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		2,993	2,505
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		1	2
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		(14)	(19)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	0	0
Cash and Cash Equivalents, Fair Value Disclosure	[1]	0	0
FinancialAssetsFairValueDisclosure1		1,526	1,509
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(218)	(278)
FinancialAssetLiabilitiesNetFairValueDisclosure1		1,308	1,231
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]
Total mark-to-market derivative liabilities		(218)	(278)
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]
Total mark-to-market derivative liabilities		(1,167)	(794)
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]
Total mark-to-market derivative liabilities		(22)	(26)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interestrateandforeigncurrencyderivativeliabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		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]
Total mark-to-market derivative liabilities		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | ProprietaryTradingLiabilitiesInterestandFX [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities		0	0
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]
Total mark-to-market derivative liabilities	[2]	971	542
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]
Total mark-to-market derivative liabilities		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]
Total mark-to-market derivative liabilities		0	0
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		255	250
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	[3]	683	677
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]
Investments, Fair Value Disclosure	[4]	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		1	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] | 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] | 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] | 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] | 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] | 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] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		783	771
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] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	20	19
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 equivalents		0	0
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] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20	19
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		255	250
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	427
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	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	0
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] | 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 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		40	42
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		25	23
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]	(873)	(481)
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] | 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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,631	1,229
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
PECO Energy Co [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		27	22
Cash and Cash Equivalents, Fair Value Disclosure		27	22
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	5	45
Cash and Cash Equivalents, Fair Value Disclosure	[7]	5	45
FinancialAssetsFairValueDisclosure1		22	62
Deferred Compensation Liability, Current and Noncurrent		(11)	(11)
Financial Liabilities Fair Value Disclosure		(11)	(11)
FinancialAssetLiabilitiesNetFairValueDisclosure1		11	51
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	0	0
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	17
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	7
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	10
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	5	45
Cash and Cash Equivalents, Fair Value Disclosure	[7]	5	45
FinancialAssetsFairValueDisclosure1		12	52
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		12	52
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	0	0
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	7
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	7
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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	0	0
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
FinancialAssetsFairValueDisclosure1		10	10
Deferred Compensation Liability, Current and Noncurrent		(11)	(11)
Financial Liabilities Fair Value Disclosure		(11)	(11)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(1)	(1)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	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	10
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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		10	10
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	0	0
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
FinancialAssetsFairValueDisclosure1		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	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] | 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] | 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] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		11	13
Cash and Cash Equivalents, Fair Value Disclosure		11	13
Baltimore Gas and Electric Company [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		2	2
Cash and Cash Equivalents, Fair Value Disclosure		2	2
Baltimore Gas and Electric Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	45	36
Cash and Cash Equivalents, Fair Value Disclosure	[7]	45	36
FinancialAssetsFairValueDisclosure1		50	40
Deferred Compensation Liability, Current and Noncurrent		(4)	(4)
Financial Liabilities Fair Value Disclosure		(4)	(4)
FinancialAssetLiabilitiesNetFairValueDisclosure1		46	36
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	0	0
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		5	4
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		5	4
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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	45	36
Cash and Cash Equivalents, Fair Value Disclosure	[7]	45	36
FinancialAssetsFairValueDisclosure1		50	40
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		50	40
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	0	0
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		5	4
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		5	4
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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	0	0
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
FinancialAssetsFairValueDisclosure1		0	0
Deferred Compensation Liability, Current and Noncurrent		(4)	(4)
Financial Liabilities Fair Value Disclosure		(4)	(4)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(4)	(4)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	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] | 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] | 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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	0	0
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
FinancialAssetsFairValueDisclosure1		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	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] | 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] | 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, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		33	33
Cash and Cash Equivalents, Fair Value Disclosure		33	33
FinancialAssetsFairValueDisclosure1		134	133
Deferred Compensation Liability, Current and Noncurrent		(4)	(5)
Financial Liabilities Fair Value Disclosure		(4)	(5)
FinancialAssetLiabilitiesNetFairValueDisclosure1		130	128
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		101	100
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	43
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		15	16
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		43	41
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		33	33
Cash and Cash Equivalents, Fair Value Disclosure		33	33
Investments, Fair Value Disclosure		0
FinancialAssetsFairValueDisclosure1		76	76
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		76	76
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		8	9
Cash and Cash Equivalents, Fair Value Disclosure		8	9
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	43
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	43
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] | Cash Surrender Value [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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
FinancialAssetsFairValueDisclosure1		38	38
Deferred Compensation Liability, Current and Noncurrent		(4)	(5)
Financial Liabilities Fair Value Disclosure		(4)	(5)
FinancialAssetLiabilitiesNetFairValueDisclosure1		34	33
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	38
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		15	16
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Surrender Value [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		23	22
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			0
FinancialAssetsFairValueDisclosure1		20	19
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		20	19
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		20	19
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] | Cash Surrender Value [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20	19
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		39	42
Cash and Cash Equivalents, Fair Value Disclosure		39	42
FinancialAssetsFairValueDisclosure1		40	42
Deferred Compensation Liability, Current and Noncurrent		(1)	(1)
Financial Liabilities Fair Value Disclosure		(1)	(1)
FinancialAssetLiabilitiesNetFairValueDisclosure1		39	41
U.S. Treasury and agencies
Derivative Asset, Fair Value, Amount Not Offset Against Collateral			2
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		1	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		1	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] | Cash Surrender Value [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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		39	42
Cash and Cash Equivalents, Fair Value Disclosure		39	42
Investments, Fair Value Disclosure		1	0
Derivative Asset			2
FinancialAssetsFairValueDisclosure1		40	42
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		40	42
U.S. Treasury and agencies
Collateral Amount Offset Against Fair Value Of Derivative Current Asset			(2)
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		5	4
Cash and Cash Equivalents, Fair Value Disclosure		5	4
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		1	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] | Cash Surrender Value [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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		0	0
Cash and Cash Equivalents, Fair Value Disclosure		0	0
Investments, Fair Value Disclosure			0
FinancialAssetsFairValueDisclosure1		0	0
Deferred Compensation Liability, Current and Noncurrent		(1)	(1)
Financial Liabilities Fair Value Disclosure		(1)	(1)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(1)	(1)
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] | 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] | Cash Surrender Value [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] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		0	0
Cash and Cash Equivalents, Fair Value Disclosure		0	0
Investments, Fair Value Disclosure			0
FinancialAssetsFairValueDisclosure1		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	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] | 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] | Cash Surrender Value [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] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Pepco Holdings LLC [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0
Total mark-to-market derivative liabilities		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		0
Derivative Liability, Current		0
Pepco Holdings LLC [Member] | Predecessor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset			0
Total mark-to-market derivative liabilities			0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent			0
Derivative Liability, Current			0
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		154	217
Cash and Cash Equivalents, Fair Value Disclosure		154	217
Derivative Asset		0	2
FinancialAssetsFairValueDisclosure1		286	348
Deferred Compensation Liability, Current and Noncurrent		(25)	(28)
Financial Liabilities Fair Value Disclosure		(25)	(28)
FinancialAssetLiabilitiesNetFairValueDisclosure1		261	320
U.S. Treasury and agencies
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0	0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0	(2)
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		132	131
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		74	73
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		15	16
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Surrender Value [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		43	42
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Successor [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			19
Cash and Cash Equivalents, Fair Value Disclosure			19
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		23	23
Cash and Cash Equivalents, Fair Value Disclosure		23	23
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		154	217
Cash and Cash Equivalents, Fair Value Disclosure		154	217
Derivative Asset		0	2
FinancialAssetsFairValueDisclosure1		228	290
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		228	290
U.S. Treasury and agencies
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0	0
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0	(2)
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		19
Cash and Cash Equivalents, Fair Value Disclosure		19
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		74	73
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		74	73
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Surrender Value [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		0	0
Cash and Cash Equivalents, Fair Value Disclosure		0	0
Investments, Fair Value Disclosure			0
FinancialAssetsFairValueDisclosure1		38	38
Deferred Compensation Liability, Current and Noncurrent		(25)	(28)
Financial Liabilities Fair Value Disclosure		(25)	(28)
FinancialAssetLiabilitiesNetFairValueDisclosure1		13	10
U.S. Treasury and agencies
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash and Cash Equivalents [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] | Successor [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		38	38
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		15	16
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Surrender Value [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		23	22
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		0	0
Cash and Cash Equivalents, Fair Value Disclosure		0	0
Investments, Fair Value Disclosure			0
FinancialAssetsFairValueDisclosure1		20	20
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		20	20
U.S. Treasury and agencies
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Derivative, Name [Domain]
U.S. Treasury and agencies
Derivative Asset, Fair Value, Amount Not Offset Against Collateral			0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash and Cash Equivalents [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] | Successor [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20	20
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | Cash Surrender Value [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		20	20
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		80	130
Cash and Cash Equivalents, Fair Value Disclosure		80	130
FinancialAssetsFairValueDisclosure1		80	130
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		80	130
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] | Cash Surrender Value [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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		80	130
Cash and Cash Equivalents, Fair Value Disclosure		80	130
Investments, Fair Value Disclosure		0	0
FinancialAssetsFairValueDisclosure1		80	130
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		80	130
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		4	3
Cash and Cash Equivalents, Fair Value Disclosure		4	3
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		23	23
Cash and Cash Equivalents, Fair Value Disclosure		23	23
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] | 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] | Cash Surrender Value [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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		0	0
Cash and Cash Equivalents, Fair Value Disclosure		0	0
Investments, Fair Value Disclosure			0
FinancialAssetsFairValueDisclosure1		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	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] | 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] | Cash Surrender Value [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] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		0	0
Cash and Cash Equivalents, Fair Value Disclosure		0	0
Investments, Fair Value Disclosure			0
FinancialAssetsFairValueDisclosure1		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	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] | 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] | Cash Surrender Value [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] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Commonwealth Edison Co [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		263	239
Derivative Liability, Current		19	19
Commonwealth Edison Co [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		31	36
Cash and Cash Equivalents, Fair Value Disclosure		31	36
Commonwealth Edison Co [Member] | Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		3	2
Cash and Cash Equivalents, Fair Value Disclosure		3	2
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	0	20
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	20
FinancialAssetsFairValueDisclosure1		0	20
Deferred Compensation Liability, Current and Noncurrent		(8)	(8)
Financial Liabilities Fair Value Disclosure		(290)	(266)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(290)	(246)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	282	258
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] | 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] | 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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	0	20
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	20
FinancialAssetsFairValueDisclosure1		0	20
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	20
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	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] | 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] | 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, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	0	0
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
FinancialAssetsFairValueDisclosure1		0	0
Deferred Compensation Liability, Current and Noncurrent		(8)	(8)
Financial Liabilities Fair Value Disclosure		(8)	(8)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(8)	(8)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	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] | 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] | 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, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[7]	0	0
Cash and Cash Equivalents, Fair Value Disclosure	[7]	0	0
FinancialAssetsFairValueDisclosure1		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(282)	(258)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(282)	(258)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	[8]	282	258
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] | 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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		$ 0	$ 0
[1]	Generation excludes cash of $267 million and $252 million at March 31, 2017 and December 31, 2016 and restricted cash of $138 million and $157 million at March 31, 2017 and December 31, 2016. Exelon excludes cash of $381 million and $360 million at March 31, 2017 and December 31, 2016 and restricted cash of $165 million and $180 million at March 31, 2017 and December 31, 2016 and includes long term restricted cash of $25 million at March 31, 2017 and December 31, 2016, which is reported in other deferred debits on the balance sheet.
[2]	Collateral posted/(received) from counterparties totaled $75 million, $271 million and $98 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of March 31, 2017. Collateral posted/(received) from counterparties, net of collateral paid to 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.
[3]	Excludes net assets (liabilities) of $8 million and $(31) million at March 31, 2017 and December 31, 2016, 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.
[4]	Includes less than $1 million and $29 million of cash received from outstanding repurchase agreements at March 31, 2017 and December 31, 2016, respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (d) below.
[5]	Includes derivative instruments of $(1) million and $(2) million, which have a total notional amount of $886 million and $933 million at March 31, 2017 and December 31, 2016, 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 at March 31, 2017 and December 31, 2016. 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 $31 million and $36 million at March 31, 2017 and December 31, 2016 and restricted cash of $3 million and $2 million at March 31, 2017 and December 31, 2016. PECO excludes cash of $27 million and $22 million at March 31, 2017 and December 31, 2016. BGE excludes cash of $11 million and $13 million at March 31, 2017 and December 31, 2016 and includes long term restricted cash of $2 million at March 31, 2017 and 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 $263 million, respectively, at March 31, 2017, and $19 million and $239 million, respectively, at December 31, 2016, related to floating-to-fixed energy swap contracts with unaffiliated suppliers.

Fair Value of Financial Asset66

Fair Value of Financial Assets and Liabilities - Fair Value Assets Liabilities Measured On Recurring Basis Unobservable Input Reconciliation (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016		Dec. 31, 2016		Mar. 24, 2016	Dec. 31, 2015
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		$ 1,046		$ 1,547		$ 993		$ 20	$ 1,529
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(38)		(4)
Total realized / unrealized gains (losses)
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 Included In Regulatory assets		(15)		(14)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		89		97
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		(2)		(2)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		62		220
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances		(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(23)		(26)
Purchases, sales, issuances and settlements
Purchases		89		97
Ending balance
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		38		(50)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		(1)		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		6		(7)
Fair Value, Inputs, Level 3 [Member] | Consolidation, Eliminations [Member]
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		(9)		(4)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets		9		4
Exelon Generation Co L L C [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings		(102)		225
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Realized Investment Gains (Losses)		(6)		(7)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		1,308		1,792		1,231			1,776
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(39)		(4)
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		9		4
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 Included In Regulatory assets		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		89		97
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		(2)		(2)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		61		220
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(23)		(26)
Purchases, sales, issuances and settlements
Purchases		89		97
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)		(30)		(25)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		38		(50)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		(1)		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		6		(7)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		683		684		677			670
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		3		2
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		9		4
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 Included In Regulatory assets				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		17		34
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		2		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(23)		(26)
Purchases, sales, issuances and settlements
Purchases		17		34
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3				0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		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
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		20		25		19			22
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0
Total realized / unrealized gains (losses)
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 Included In Regulatory assets				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		1		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0
Purchases, sales, issuances and settlements
Purchases		1		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3				0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		565		1,047		493			1,051
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(43)	[1]	(6)	[2]
Total realized / unrealized gains (losses)
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 Included In Regulatory assets				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		69		59
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		(2)		(2)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		59		219
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0
Purchases, sales, issuances and settlements
Purchases		69		59
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		38		(50)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		(1)		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		11		(7)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Other Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		40		36		42			33
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1		0
Total realized / unrealized gains (losses)
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 Included In Regulatory assets				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		2		3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0
Purchases, sales, issuances and settlements
Purchases		2		3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		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		(5)		0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		(282)	[3]	(265)	[4]	(258)	[3]		(247)	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0	[3]	0	[4]
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		0	[3]	0	[4]
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 Included In Regulatory assets		(24)	[3]	(18)	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0	[3]	0	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0	[3]	0	[4]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	[3]	0	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0	[3]	0	[4]
Purchases, sales, issuances and settlements
Purchases		0	[3]	0	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3	[4]			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	[4]			0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		0	[3]	0	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	[3]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	[3]	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value								$ 20
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1		0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		20		20		20
Total realized / unrealized gains (losses)
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 Included In Regulatory assets		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, Sales		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		1		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances		(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0
Purchases, sales, issuances and settlements
Purchases		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3		0		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		0		0
Potomac Electric Power Company [Member] | 6311 Life Insurance [Member]
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		1		0
Purchases, sales, issuances and settlements
Purchases		1		0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(1)
Total realized / unrealized gains (losses)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		1
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		$ 20		20		$ 20			$ 19
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings				(1)
Total realized / unrealized gains (losses)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)				$ 1
[1]	Includes a reduction for the reclassification of $102 million of realized gains due to the settlement of derivative contracts for the three months ended March 31, 2017.
[2]	Includes a reduction for the reclassification of $225 million of realized gains due to the settlement of derivative contracts recorded in results of operations for the three months ended March 31, 2016.
[3]	Includes $30 million of decreases in fair value and an increase for realized losses due to settlements of $6 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 2017.
[4]	Includes $25 million of decreases in fair value and an increase for realized losses due to settlements of $7 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 2016.

Fair Value of Financial Asset67

Fair Value of Financial Assets and Liabilities Fair Value of Financial Assets and Liabilities - Narrative (Details)	Mar. 31, 2017USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward Power Basis	$ 2.67
Forward Gas Basis	0.40
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	290,000,000
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	120,000,000
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	$ 107,000,000

Fair Value of Financial Asset68

Fair Value of Financial Assets and Liabilities - Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Mar. 23, 2016	Dec. 31, 2016	Mar. 24, 2016	Dec. 31, 2015
Operating Revenue [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		$ 88	$ 49
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		140	254
Purchased Power And Fuel [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(131)	(55)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(81)	(35)
Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	[1]	4	2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	[1]	3	1
Exelon Generation Co L L C [Member] | Operating Revenue [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		88	49
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		140	254
Exelon Generation Co L L C [Member] | Purchased Power And Fuel [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(131)	(55)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(81)	(35)
Exelon Generation Co L L C [Member] | Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	[1]	3	2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	[1]	2	1
Pepco Holdings LLC [Member] | Other, net [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings				$ (17)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)				1
Potomac Electric Power Company [Member] | Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1	1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		1	1
6311 Life Insurance [Member] | Potomac Electric Power Company [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		(1)	0
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		1,046	1,547		$ 993	$ 20	$ 1,529
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		38	4
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		62	220
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		(89)	(97)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		23	26
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		1,308	1,792		1,231		1,776
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		39	4
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		61	220
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		(89)	(97)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		23	26
Fair Value, Inputs, Level 3 [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value						20
Fair Value, Inputs, Level 3 [Member] | Pepco Holdings LLC [Member] | Other, net [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			1
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		1
Fair Value, Inputs, Level 3 [Member] | Potomac Electric Power Company [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		1
Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] | Pepco Holdings LLC [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(1)	0
Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		20	20		20
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		1	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, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				20		$ 0	19
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings				1
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)				1
Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] | Potomac Electric Power Company [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		$ 20	20		$ 20		19
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			1
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)			$ 1
Fair Value, Inputs, Level 3 [Member] | Preferred Stock [Member] | Pepco Holdings LLC [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				0			$ 18
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings				(18)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)				$ 0
[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 PHI and Pepco.

Fair Value of Financial Asset69

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2017		Dec. 31, 2016
Exelon Generation Co L L C [Member] | Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 464,000,000	[1],[2]	$ 435,000,000	[3],[4]
Exelon Generation Co L L C [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	8		11
Forward gas price assets	1.92		1.72
Exelon Generation Co L L C [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	130		130
Forward gas price assets	$ 9.87		$ 9.2
Exelon Generation Co L L C [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Volatility percentage	13.00%		8.00%
Exelon Generation Co L L C [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Volatility percentage	112.00%		173.00%
Exelon Generation Co L L C [Member] | Proprietary Trading [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ 3,000,000	[1],[2]	$ (3,000,000)	[3],[4]
Exelon Generation Co L L C [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	15		19
Exelon Generation Co L L C [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	67		79
Commonwealth Edison Co [Member] | Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ (282,000,000)		$ (258,000,000)
Commonwealth Edison Co [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Forward heat rate	8.00%		8.00%
Derivatives Fair Value Footnotes [Abstract]
Fair Value Inputs, Discount for Lack of Marketability	3.00%		3.00%
Fair Value Inputs Renewable Factor	88.00%		89.00%
Commonwealth Edison Co [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward heat rate	9.00%		9.00%
Derivatives Fair Value Footnotes [Abstract]
Fair Value Inputs, Discount for Lack of Marketability	8.00%		8.00%
Fair Value Inputs Renewable Factor	121.00%		121.00%
[1]	(a)The valuation techniques, unobservable inputs and ranges are the same for the asset and liability positions.
[2]	The fair values do not include cash collateral posted on level three positions of $98 million as of March 31, 2017.
[3]	The fair values do not include cash collateral posted on level three positions of $61 million as of December 31, 2016.
[4]	The valuation techniques, unobservable inputs and ranges are the same for the asset and liability positions.

Derivative Financial Instrume70

Derivative Financial Instruments - Summary of Interest Rate and Foreign Currency Hedges (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Interest Rate Fair Value Hedge Asset at Fair Value		$ 9
Derivative Asset, Current		847	$ 917
Derivative Asset, Noncurrent		539	492
Derivative Liability, Current		(228)	(282)
Derivative Liability, Noncurrent		(420)	(392)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Interest Rate Fair Value Hedge Asset at Fair Value		3
Derivative Asset, Current		847	917
Derivative Asset, Noncurrent		527	476
Derivative Liability, Current		(209)	(263)
Derivative Liability, Noncurrent		(157)	(153)
InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Asset, Current		5	8
Derivative Asset, Noncurrent		3	4
Derivative Asset		8	12
Derivative Liability, Current		(7)	8
Derivative Liability, Noncurrent		(4)	(4)
Derivative Liability		(11)	12
Derivative, Fair Value, Net		(3)	0
InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member] | Economic Hedges [Member]
Derivative [Line Items]
Derivative Asset, Current		15	17
Derivative Asset, Noncurrent		7	11
Derivative Asset		22	28
Derivative Liability, Current		(17)	13
Derivative Liability, Noncurrent		(8)	(8)
Derivative Liability		(25)	21
Derivative, Fair Value, Net		(3)	(7)
InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member] | Collateral And Netting [Member]
Derivative [Line Items]
Derivative Asset, Current		(13)	(13)
Derivative Asset, Noncurrent		(5)	(8)
Derivative Asset		(18)	(21)
Derivative Liability, Current		13	(14)
Derivative Liability, Noncurrent		5	(9)
Derivative Liability		18	(23)
Derivative, Fair Value, Net		0	(2)
Derivative [Member]
Derivative [Line Items]
Derivative Asset, Current		842	909
Derivative Asset, Noncurrent		524	472
Derivative Asset		1,366	1,381
Derivative Liability, Current		(221)	(274)
Derivative Liability, Noncurrent		(416)	(388)
Derivative Liability		(637)	(662)
Derivative, Fair Value, Net		(729)	(719)
Derivative [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Asset, Current	[1]	842	909
Derivative Asset, Noncurrent	[1]	524	472
Derivative Asset	[1]	1,366	1,381
Derivative Liability, Current	[1]	(202)	(255)
Derivative Liability, Noncurrent	[1]	(153)	(149)
Derivative Liability	[1]	(355)	(404)
Derivative, Fair Value, Net	[1]	(1,011)	(977)
Not Designated as Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Asset, Current		3	4
Derivative Asset, Noncurrent		1	1
Derivative Asset		4	5
Derivative Liability, Current		(2)	2
Derivative Liability, Noncurrent		(1)	(2)
Derivative Liability		(3)	4
Derivative, Fair Value, Net		1	(1)
Designated as Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Derivative Asset, Current		5	8
Derivative Asset, Noncurrent		15	20
Derivative Asset		20	28
Derivative Liability, Current		(7)	8
Derivative Liability, Noncurrent		(4)	(4)
Derivative Liability		(11)	12
Derivative, Fair Value, Net			(16)
Designated as Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Asset, Current		0	0
Derivative Asset, Noncurrent		0	0
Derivative Asset		0	0
Derivative Liability, Current		(1)	7
Derivative Liability, Noncurrent		0	(3)
Derivative Liability		(1)	10
Derivative, Fair Value, Net		(1)	10
Designated as Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member] | Corporate, Non-Segment [Member]
Derivative [Line Items]
Derivative Asset, Current		0	0
Derivative Asset, Noncurrent		12	16
Derivative Asset		12	16
Derivative Liability, Current		0	0
Derivative Liability, Noncurrent		0	0
Derivative Liability		0	0
Derivative, Fair Value, Net		$ 12	$ (16)
[1]	.

Derivative Financial Instrume71

Derivative Financial Instruments - Summary of Gains and Losses on Hedges (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016
Derivative [Line Items]
Income taxes		$ 215		$ 184
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net	[1]	4		2
Derivative, Loss on Derivative			$ 3
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		1			$ 2
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes		127		151
Interest Expense [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Increase (Decrease) in Fair Value of Hedged Item in Price Risk Fair Value Hedge		8		(15)
Interest Rate Swap [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings		$ (4)		$ 17
[1]	Three Months Ended March 31, Income StatementLocation 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on BorrowingsExelonInterest expense $(4) $17 $8 $(15)

Derivative Financial Instrume72

Derivative Financial Instruments Derivative Financial Instruments - Summary of Derivative Fair Value Balances (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative Asset, Current		$ 847	$ 917
Derivative Asset, Noncurrent		539	492
Derivative, Collateral, Right to Reclaim Cash		1	29
Margin Deposit Assets		14	158
Derivative Liability, Current		(228)	(282)
Derivative Liability, Noncurrent		(420)	(392)
Derivative [Member]
Derivative [Line Items]
Derivative Asset, Current		842	909
Derivative Asset, Noncurrent		524	472
Total mark-to-market derivative net assets (liabilities)		729	719
Total mark-to-market derivative assets		1,366	1,381
Derivative Liability, Current		(221)	(274)
Derivative Liability, Noncurrent		(416)	(388)
Total mark-to-market derivative liabilities		(637)	(662)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Asset, Current		847	917
Derivative Asset, Noncurrent		527	476
Derivative Liability, Current		(209)	(263)
Derivative Liability, Noncurrent		(157)	(153)
Exelon Generation Co L L C [Member] | Economic Hedges [Member]
Derivative [Line Items]
Derivative Asset, Current		3,398	3,623
Derivative Asset, Noncurrent		1,975	1,467
Total mark-to-market derivative net assets (liabilities)		564	651
Total mark-to-market derivative assets		5,373	5,090
Derivative Liability, Current		(3,029)	(3,165)
Derivative Liability, Noncurrent		(1,780)	(1,274)
Total mark-to-market derivative liabilities		(4,809)	(4,439)
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Current assets collateral offset			100
Noncurrent assets collateral offset			72
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		444
Current liabilities collateral offset			95
Noncurrent liabilities collateral offset			62
Total cash collateral received net of cash collateral posted			329
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative, Collateral, Right to Reclaim Cash		128
Margin Deposit Assets		14	158
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative, Collateral, Obligation to Return Cash		136
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative, Collateral, Right to Reclaim Cash		77
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivative [Line Items]
Derivative, Collateral, Obligation to Return Cash		103
Exelon Generation Co L L C [Member] | Derivative [Member]
Derivative [Line Items]
Derivative Asset, Current	[1]	842	909
Derivative Asset, Noncurrent	[1]	524	472
Total mark-to-market derivative net assets (liabilities)	[1]	1,011	977
Total mark-to-market derivative assets	[1]	1,366	1,381
Derivative Liability, Current	[1]	(202)	(255)
Derivative Liability, Noncurrent	[1]	(153)	(149)
Total mark-to-market derivative liabilities	[1]	(355)	(404)
Exelon Generation Co L L C [Member] | Proprietary Trading [Member]
Derivative [Line Items]
Derivative Asset, Current		56	55
Derivative Asset, Noncurrent		24	21
Total mark-to-market derivative net assets (liabilities)		3	(3)
Total mark-to-market derivative assets		80	76
Derivative Liability, Current		(49)	(54)
Derivative Liability, Noncurrent		(28)	(25)
Total mark-to-market derivative liabilities		(77)	(79)
Exelon Generation Co L L C [Member] | Collateral And Netting [Member]
Derivative [Line Items]
Derivative Asset, Current		(2,612)	(2,769)
Derivative Asset, Noncurrent		(1,475)	(1,016)
Total mark-to-market derivative net assets (liabilities)	[2]	444	329
Total mark-to-market derivative assets	[2]	(4,087)	(3,785)
Derivative Liability, Current		2,876	2,964
Derivative Liability, Noncurrent		1,655	1,150
Total mark-to-market derivative liabilities	[2]	4,531	4,114
Commonwealth Edison Co [Member]
Derivative [Line Items]
Derivative Liability, Current		(19)	(19)
Derivative Liability, Noncurrent		(263)	(239)
Commonwealth Edison Co [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Current		0	0
Derivative Asset, Noncurrent		0	0
Total mark-to-market derivative net assets (liabilities)	[3]	(282)	(258)
Total mark-to-market derivative assets	[3]	0	0
Derivative Liability, Current		(19)	(19)
Derivative Liability, Noncurrent		(263)	(239)
Total mark-to-market derivative liabilities	[3]	(282)	(258)
Delmarva Power and Light Company [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Asset, Current		0	2
Derivative Asset, Noncurrent		0	0
Total mark-to-market derivative net assets (liabilities)		0	2
Total mark-to-market derivative assets		0	2
Derivative Liability, Current		0	0
Derivative Liability, Noncurrent		0	0
Total mark-to-market derivative liabilities		0	0
Delmarva Power and Light Company [Member] | Derivative [Member]
Derivative [Line Items]
Derivative Asset, Current	[4]	0	0
Derivative Asset, Noncurrent	[4]	0	0
Total mark-to-market derivative net assets (liabilities)		0	0
Total mark-to-market derivative assets	[4]	0	0
Derivative Liability, Current	[4]	0	0
Derivative Liability, Noncurrent	[4]	0	0
Total mark-to-market derivative liabilities	[4]	0	0
Delmarva Power and Light Company [Member] | Collateral And Netting [Member]
Derivative [Line Items]
Derivative Asset, Current		0	(2)
Derivative Asset, Noncurrent		0	0
Total mark-to-market derivative net assets (liabilities)		0	(2)
Total mark-to-market derivative assets		0	(2)
Derivative Liability, Current		0	0
Derivative Liability, Noncurrent		0	0
Total mark-to-market derivative liabilities		0	0
Pepco Holdings LLC [Member] | Successor [Member]
Derivative [Line Items]
Derivative Asset, Current		0
Derivative Asset, Noncurrent		0
Total mark-to-market derivative net assets (liabilities)		0
Total mark-to-market derivative assets		0
Derivative Liability, Current		0
Derivative Liability, Noncurrent		0
Total mark-to-market derivative liabilities		$ 0
Pepco Holdings LLC [Member] | Predecessor [Member]
Derivative [Line Items]
Derivative Asset, Current			0
Derivative Asset, Noncurrent			0
Total mark-to-market derivative net assets (liabilities)			0
Total mark-to-market derivative assets			0
Derivative Liability, Current			0
Derivative Liability, Noncurrent			0
Total mark-to-market derivative liabilities			$ 0
[1]	.
[2]	.
[3]	.
[4]	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.

Derivative Financial Instrume73

Derivative Financial Instruments - Summary of AOCI related to Cash Flow Hedges (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016		Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		$ (2,670)				$ (2,660)
Income taxes		215		$ 184
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassifications from accumulated OCI to net income		4,560		4,473
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(41)				(54)
Income taxes		127		151
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassifications from accumulated OCI to net income		4,558		4,471
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Derivative [Line Items]
OCI before reclassifications	[1]	2		(10)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]	(4)		(3)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(11)	[1]	(26)	[1]	(17)	$ (19)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
OCI before reclassifications	[1]	2		(8)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2]	(4)		(3)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax		(13)	[1]	(26)	[1]	$ (19)	$ (21)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[3]	(40)		(37)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[3]	$ (4)		(3)
Interest Expense [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion				3
Interest Expense [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion				3
Interest Expense [Member] | Operating Revenue [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion				(10)
Interest Expense [Member] | Total Cash Flow Hedges [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion				$ (8)
[1]	All amounts are net of tax and noncontrolling interest. Amounts in parenthesis represent a decrease in AOCI.
[2]	See next tables for details about these reclassifications.
[3]	Amounts in parenthesis represent a decrease in net income.

Derivative Financial Instrume74

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ (47)	$ 107
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(49)	103
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(51)	106
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(49)	103
Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(93)	40
Interest Expense [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(47)	108
Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	44	63
Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(2)	3
Foreign Exchange Contract [Member] | Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0
Unrealized Gain (Loss) on Derivatives	0	0
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	0	0
Foreign Exchange Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1)	(2)
Unrealized Gain (Loss) on Derivatives	(2)	(5)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(1)	(3)
Foreign Exchange Contract [Member] | Interest Expense [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1)	(2)
Unrealized Gain (Loss) on Derivatives	(2)	(5)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(1)	(3)
Foreign Exchange Contract [Member] | Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1)	(2)
Unrealized Gain (Loss) on Derivatives	(2)	(5)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(1)	(3)
Foreign Exchange Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1)	1
Unrealized Gain (Loss) on Derivatives	(1)	(1)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	0	(2)
Commodity Contract [Member] | Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	(135)	(127)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	42	167
Unrealized Gain (Loss) on Derivatives	(93)	40
Commodity Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	(42)	152
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(5)	(44)
Unrealized Gain (Loss) on Derivatives	(47)	108
Commodity Contract [Member] | Interest Expense [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	(42)	152
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(5)	(44)
Commodity Contract [Member] | Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	93	279
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(47)	(211)
Unrealized Gain (Loss) on Derivatives	46	68
Commodity Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	0	7
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1)	(3)
Unrealized Gain (Loss) on Derivatives	$ (1)	$ 4

Derivative Financial Instrume75

Derivative Financial Instruments - Summary of Proprietary Trading Activities (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ (47)	$ 107
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(49)	103
Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(2)	3
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(51)	106
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(49)	103
Commodity Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	0	7
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1)	(3)
Unrealized Gain (Loss) on Derivatives	(1)	4
Foreign Exchange Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1)	1
Unrealized Gain (Loss) on Derivatives	(1)	(1)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	$ 0	$ (2)

Derivative Financial Instrume76

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) - Exelon Generation Co L L C [Member] $ in Millions	Mar. 31, 2017USD ($)
Derivative [Line Items]
Investor-owned utilities, marketers and power producers	$ 600
Energy Cooperatives And Municipalities	663
Financial institutions	101
Other	93
Net Exposure [Member]
Derivative [Line Items]
Investment grade	948
Non-investment grade	72
No external ratings - internally rated - investment grade	324
No external ratings - internally rated - non-investment grade	113
Total	1,457
Total Exposure Before Credit Collateral [Member]
Derivative [Line Items]
Investment grade	964
Non-investment grade	75
No external ratings - internally rated - investment grade	324
No external ratings - internally rated - non-investment grade	127
Total	1,490
Credit Collateral [Member]
Derivative [Line Items]
Investment grade	16
Non-investment grade	3
No external ratings - internally rated - investment grade	0
No external ratings - internally rated - non-investment grade	14
Total	33	[1]
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Investment grade	1
Non-investment grade	0
No external ratings - internally rated - investment grade	0
No external ratings - 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	313
Non-investment grade	0
No external ratings - internally rated - investment grade	0
No external ratings - internally rated - non-investment grade	0
Total	$ 313
[1]	of March 31, 2017, credit collateral held from counterparties where Generation had credit exposure included $23 million of cash and $10 million of letters of credit. The credit collateral does not include non-liquid collateral.

Derivative Financial Instrume77

Derivative Financial Instruments - Summary of Credit Risk Related Contingent Features (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Aggregate fair value of derivatives with credit-risk-related contingent features		$ (994)	$ (960)
Contractual right of offset related to derivative assets		712	627
Net liability position after contractual right of offset	[1]	$ (282)	$ (333)
[1]	unt 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.Ge

Derivative Financial Instrume78

Derivative Financial Instruments - Narrative (Details) $ in Thousands		3 Months Ended			12 Months Ended
		Mar. 31, 2017USD ($)GWh	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)GWh	Dec. 31, 2016USD ($)
Derivative [Line Items]
Income taxes		$ 215,000		$ 184,000
Derivative, Notional Amount			$ 100,000	600,000
Derivative, Loss on Derivative			3,000
Derivative Instruments, Loss Recognized in Other Comprehensive Income (Loss), Effective Portion			$ 3,000
Hypothetical increase in interest rates associated with variable-rate debt		2,000
Ineffective portion recognized in income	[1]	4,000		2,000
Mark-to-market derivative liabilities (noncurrent liabilities)		420,000			$ 392,000
Cash collateral posted		23,000
Letters of credit posted		10,000
Interest Rate Fair Value Hedge Asset at Fair Value		(9,000)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes		127,000		$ 151,000
Mark-to-market derivative liabilities (noncurrent liabilities)		157,000			153,000
Cash collateral received not offset against net derivative positions		(8,000)
Cash collateral posted		471,000			347,000
Letters of credit held		32,000			28,000
Letters of credit posted		273,000			284,000
Cash collateral held		35,000			24,000
Incremental collateral for loss of investment grade credit rating		1,800,000			1,900,000
Interest Rate Fair Value Hedge Asset at Fair Value		$ (3,000)
Derivative, Nonmonetary Notional Amount, Energy Measure | GWh		1,850		1,220
Commonwealth Edison Company [Member]
Derivative [Line Items]
Cash collateral held		$ 1,000
Commonwealth Edison Co [Member]
Derivative [Line Items]
Income taxes		92,000		$ 77,000
Mark-to-market derivative liabilities (noncurrent liabilities)		263,000			239,000
Cash collateral held		19,000
Incremental collateral for loss of investment grade credit rating		10,000
Credit Exposure Under Off System Sales		1,000
PECO Energy Co [Member]
Derivative [Line Items]
Income taxes		$ 36,000		43,000
Estimated percentage of natural gas purchases hedged		25.00%
Incremental collateral for loss of investment grade credit rating		$ 27,000
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Income taxes		80,000		66,000
Incremental collateral for loss of investment grade credit rating		47,000
Credit Exposure Under Off System Sales		3,000
Delmarva Power and Light Company [Member]
Derivative [Line Items]
Income taxes		11,000		(9,000)
Incremental collateral for loss of investment grade credit rating		$ 11,000
Minimum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		97.00%
Expected Generation Hedged In Year Two		60.00%
Expected generation hedged in year three		30.00%
Minimum [Member] | Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Estimated percentage of natural gas purchases hedged		10.00%
Maximum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		100.00%
Expected Generation Hedged In Year Two		63.00%
Expected generation hedged in year three		33.00%
Maximum [Member] | Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Estimated percentage of natural gas purchases hedged		20.00%
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		$ 800,000
Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative, Notional Amount				100,000
Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Notional Amount of Pre-issuance Interest Rate Cash Flow Hedge Derivatives		657,000
Designated as Hedging Instrument [Member] | Commonwealth Edison Co [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	[2]	(282,000)			(258,000)
Mark-to-market derivative liabilities (noncurrent liabilities)		263,000			239,000
Designated as Hedging Instrument [Member] | Delmarva Power and Light Company [Member]
Derivative [Line Items]
Derivative, Fair Value, Net		0			2,000
Mark-to-market derivative liabilities (noncurrent liabilities)		0			0
Foreign Exchange Contract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Notional Amount		73,000
Energy Related Derivative [Member] | Delmarva Power and Light Company [Member]
Derivative [Line Items]
Brokered Natural Gas Margin Revenue		2,750
Derivative [Member]
Derivative [Line Items]
Derivative, Fair Value, Net		729,000			719,000
Mark-to-market derivative liabilities (noncurrent liabilities)		416,000			388,000
Derivative [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	[3]	1,011,000			977,000
Mark-to-market derivative liabilities (noncurrent liabilities)	[3]	153,000			149,000
Derivative [Member] | Delmarva Power and Light Company [Member]
Derivative [Line Items]
Derivative, Fair Value, Net		0			0
Mark-to-market derivative liabilities (noncurrent liabilities)	[4]	0			0
Fair Value Hedging [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		800,000			800,000
Increase (Decrease) in Fair Value of Interest Rate Fair Value Hedging Instruments		12,000			$ 16,000
Other Solar Projects [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Notional amounts on forward starting interest rate swaps				25,000
Other Solar Projects [Member] | Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Notional amounts on forward starting interest rate swaps				24,000
ExGen Texas Power [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		494,000
ExGen Texas Power [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities (noncurrent liabilities)		7,000
ExGen Renewables [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		164,000
ExGen Renewables [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities (noncurrent liabilities)		1,000
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Income taxes	[5]	(3,000)		$ (2,000)
Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		13,000
PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from affiliated electric and gas utility		31,000
Baltimore Gas And Electric Company Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from affiliated electric and gas utility		24,000
Potomac Electric Power Company [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		40,000
Delmarva Power and Light Company [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		13,000
Atlantic City Electric Company [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		$ 7,000
[1]	Three Months Ended March 31, Income StatementLocation 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on BorrowingsExelonInterest expense $(4) $17 $8 $(15)
[2]	.
[3]	.
[4]	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.
[5]	Amounts in parenthesis represent a decrease in net income.

Debt and Credit Agreements - Co

Debt and Credit Agreements - Commercial Paper Borrowings (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Corporate, Non-Segment [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	$ 204	$ 0
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	579	620
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	365	0
PECO Energy Co [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	0	0
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	95	45
PEPCO Holdings Inc [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	0	0
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	$ 167	$ 23

Debt and Credit Agreements - Is

Debt and Credit Agreements - Issuance of Long-Term Debt (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Exelon Generation Co L L C [Member] | EEPFNotes372April2018 [Member]
Debt Instrument [Line Items]
Interest Rate	3.72%
Debt Instrument, Face Amount	$ 1
Exelon Generation Co L L C [Member] | EEPF261Sep2018 [Member]
Debt Instrument [Line Items]
Interest Rate	2.61%
Debt Instrument, Face Amount	$ 1
Exelon Generation Co L L C [Member] | EEPFNotes390Jan2018 [Member]
Debt Instrument [Line Items]
Interest Rate	3.90%
Debt Instrument, Face Amount	$ 6
Exelon Generation Co L L C [Member] | AGEPFNotesNov2017 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 13
Debt Instrument, Interest Rate Terms	LIBOR + 1.25%
Exelon Generation Co L L C [Member] | SeniorUnsecured295Jan2020 [Member]
Debt Instrument [Line Items]
Interest Rate	2.95%
Debt Instrument, Face Amount	$ 250
Exelon Generation Co L L C [Member] | SeniorUnsecured340Mar2022 [Member]
Debt Instrument [Line Items]
Interest Rate	3.40%
Debt Instrument, Face Amount	$ 500
Potomac Electric Power Company [Member] | EEPFNotes330December2017 [Member]
Debt Instrument [Line Items]
Interest Rate	3.30%
Debt Instrument, Face Amount	$ 1

Debt and Credit Agreements - Na

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

1 Months Ended

3 Months Ended

Jun. 30, 2014

Mar. 31, 2017

Mar. 31, 2016

Mar. 23, 2017

Jan. 09, 2017

May 26, 2016

Apr. 01, 2016

Jan. 13, 2016

Jan. 05, 2016

Oct. 23, 2015

Aug. 10, 2013

Jan. 31, 2013

Aug. 01, 2011

Debt Instrument [Line Items]

Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value

$ 1,150

Extinguishment of Debt, Amount

11

$ 11

Junior Subordinated Debt [Member]

Debt Instrument [Line Items]

Junior Subordinated Notes

$ 1,150

Equity Units Issued

23

Debt Instrument, Convertible, Conversion Price

$ 50

Interest Rate

2.50%

3.497%

Minimum [Member] | Junior Subordinated Debt [Member]

Debt Instrument [Line Items]

Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value

26

Maximum [Member] | Junior Subordinated Debt [Member]

Debt Instrument [Line Items]

Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Shares, at Fair Value

33

Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of Credit Facility, Maximum Borrowing Capacity

$ 600

$ 500

Corporate, Non-Segment [Member]

Debt Instrument [Line Items]

Short-term Bank Loans and Notes Payable

$ 500

Debt Instrument, Interest Rate Terms

LIBOR plus 1%

Pepco Holdings LLC [Member]

Debt Instrument [Line Items]

Short-term Bank Loans and Notes Payable

$ 500

Debt Instrument, Interest Rate Terms

LIBOR plus 1%

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

Debt Instrument [Line Items]

Line of Credit Facility, Maximum Borrowing Capacity

$ 900

$ 1,500

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

Debt Instrument [Line Items]

Line of Credit Facility, Maximum Borrowing Capacity

$ 100

$ 200

$ 150

$ 100

$ 75

Income Taxes - Reconciliation t

Income Taxes - Reconciliation to Effective Tax Rate (Details)		Mar. 31, 2016		Mar. 31, 2017	Mar. 31, 2016		Mar. 23, 2016
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				0.90%	(1.10%)
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				3.40%	5.60%
Amortization of investment tax credit, including deferred taxes on basis difference				(0.40%)	(1.60%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(2.40%)	(5.50%)
Production tax credits and other credits				(0.60%)	(5.10%)
Noncontrolling interests				(0.10%)	0.50%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				(11.40%)	33.60%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent				(6.60%)
Other				(0.00%)	(2.00%)
Effective income tax rate				17.80%	59.40%
Exelon Generation Co L L C [Member]
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				1.00%	3.70%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				7.60%	4.20%
Amortization of investment tax credit, including deferred taxes on basis difference				(0.70%)	(1.00%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				0.00%	0.00%
Production tax credits and other credits				(1.40%)	(3.90%)
Noncontrolling interests				(0.30%)	0.30%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				(3.30%)	0.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent				(14.50%)
Other				(0.10%)	(1.60%)
Effective income tax rate				23.30%	36.70%
Commonwealth Edison Co [Member]
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				4.90%	5.10%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)	(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference				(0.20%)	(0.30%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(0.20%)	(0.10%)
Production tax credits and other credits				(0.00%)	(0.00%)
Noncontrolling interests				0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				0.00%	0.00%
Other				(0.00%)	0.40%
Effective income tax rate				39.50%	40.10%
PECO Energy Co [Member]
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				0.10%	1.00%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)	(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference				(0.10%)	(0.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(13.20%)	(9.30%)
Production tax credits and other credits				(0.00%)	(0.00%)
Noncontrolling interests				0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				0.00%	0.00%
Other				0.30%	(0.90%)
Effective income tax rate				22.10%	25.70%
Baltimore Gas and Electric Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				5.20%	5.20%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)	(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference				(0.10%)	(0.10%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(0.90%)	(0.60%)
Production tax credits and other credits				(0.00%)	(0.00%)
Noncontrolling interests				0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				0.00%	0.00%
Other				(0.20%)	(0.00%)
Effective income tax rate				39.00%	39.50%
Delmarva Power and Light Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%	[1]
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				5.30%	(2.70%)	[1],[2]
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)	(0.00%)	[1]
Amortization of investment tax credit, including deferred taxes on basis difference				(0.30%)	0.10%	[1]
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(1.90%)	0.70%	[1]
Production tax credits and other credits				(0.00%)	(0.00%)	[1]
Noncontrolling interests				0.00%	0.00%	[1]
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				(21.90%)	(22.10%)
Other				(0.00%)	0.10%	[1]
Effective income tax rate				16.20%	11.10%	[1]
Potomac Electric Power Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%	[1]
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				4.60%	(2.50%)	[1],[2]
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent	[1]				(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference				(0.10%)	(0.00%)	[1]
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(5.80%)	2.80%	[1]
Production tax credits and other credits				(0.00%)	(0.00%)	[1]
Noncontrolling interests				0.00%	0.00%	[1]
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				(34.20%)	(16.50%)
Other				0.50%	(0.00%)	[1]
Effective income tax rate				0.00%	18.80%	[1]
Potomac Electric Power Company [Member] | Successor [Member]
Increase (decrease) due to:
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)
Atlantic City Electric Company [Member]
Increase (decrease) due to:
U.S. Federal statutory rate				35.00%	35.00%	[1]
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent				5.60%	5.90%	[1]
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent				(0.00%)	(0.00%)	[1]
Amortization of investment tax credit, including deferred taxes on basis difference				(0.40%)	0.20%	[1]
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent				(3.40%)	0.60%	[1]
Production tax credits and other credits				(0.00%)	(0.00%)	[1]
Noncontrolling interests				0.00%	0.00%	[1]
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				(167.10%)	(17.00%)
Other				(3.00%)	0.10%	[1]
Effective income tax rate				(133.30%)	24.80%	[1]
Pepco Holdings LLC [Member] | Predecessor [Member]
Increase (decrease) due to:
U.S. Federal statutory rate							35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent							11.90%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent							(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference							(0.90%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent							(13.50%)
Production tax credits and other credits							(0.00%)
Noncontrolling interests							0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent							11.10%
Other							3.60%
Effective income tax rate							47.20%
Pepco Holdings LLC [Member] | Successor [Member]
Increase (decrease) due to:
U.S. Federal statutory rate		35.00%	[1]	35.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent		5.40%	[1]	4.90%
Effective Income Tax Rate Reconciliation, Tax Contingency, Other, Percent		(0.00%)	[1]	(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference		(0.00%)	[1]	(0.20%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		0.00%	[1]	(3.80%)
Production tax credits and other credits		(0.00%)	[1]	(0.00%)
Noncontrolling interests		0.00%	[1]	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent		(15.10%)		(42.40%)
Other		0.20%	[1]	(0.40%)
Effective income tax rate		25.50%	[1]	(6.90%)
[1]	Pepco, DPL and ACE recognized a loss before income taxes for the three months ended March 31, 2016, and PHI recognized a loss before income taxes for the period of March 24, 2016, through March 31, 2016. As a result, positive percentages represent an income tax benefit for the periods presented.
[2]	Includes a remeasurement of uncertain state income tax positions for Pepco and DPL.

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Mar. 31, 2016	Mar. 31, 2013	Dec. 31, 2009
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	$ 769	$ 916
Unrecognized Tax Benefits, Period Increase (Decrease)	76
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities	21
Like kind exchange [Member]
Income Tax Additional Narrative Information [Line Items]
Payments for Other Taxes	950
Deferred Gain on Sale of Property						$ 1,200
IRS asserted penalties for understatement of tax	90
Expected non-cash charge to earnings					$ 50
Early termination amount		1,250
Taxes Payable, Current	335			$ 360
Income Taxes Receivable	80
Unrecognized Tax Benefits, Income Tax Penalties Accrued	1,300
Deferred Income Tax Expense (Benefit)	350
Tax Adjustments, Settlements, and Unusual Provisions			$ 106
Income Tax Examination, Interest Expense			94
Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	470	490
Commonwealth Edison Co [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	(12)	(12)
Unrecognized Tax Benefits, Period Increase (Decrease)	(12)
Commonwealth Edison Co [Member] | Like kind exchange [Member]
Income Tax Additional Narrative Information [Line Items]
Payments for Other Taxes	300
Expected non-cash charge to earnings					$ 20
Taxes Payable, Current			150
Income Taxes Receivable	345
Unrecognized Tax Benefits, Income Tax Penalties Accrued	300
Tax Adjustments, Settlements, and Unusual Provisions			86
Income Tax Examination, Interest Expense			$ 64
PECO Energy Co [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	0	0
Baltimore Gas and Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	120	120
Pepco Holdings LLC [Member] | Successor [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	112	172
Potomac Electric Power Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	59	80
Delmarva Power and Light Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	21	37
Atlantic City Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	0	$ 22
Internal Revenue Service (IRS) [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	146
Internal Revenue Service (IRS) [Member] | Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	19
Internal Revenue Service (IRS) [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	59
Internal Revenue Service (IRS) [Member] | Potomac Electric Power Company [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	21
Internal Revenue Service (IRS) [Member] | Delmarva Power and Light Company [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	16
Internal Revenue Service (IRS) [Member] | Atlantic City Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	22
State and Local Jurisdiction [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	257
State and Local Jurisdiction [Member] | Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized tax benefits that if recognized would affect the effective tax rate	50
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	57
State and Local Jurisdiction [Member] | Baltimore Gas and Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	120
State and Local Jurisdiction [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	80
State and Local Jurisdiction [Member] | Potomac Electric Power Company [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	59
State and Local Jurisdiction [Member] | Delmarva Power and Light Company [Member]
Income Tax Additional Narrative Information [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	$ 21

Income Taxes Income Tax Unrecog

Income Taxes Income Tax Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 769	$ 916
Exelon Generation Co L L C [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	470	490
Commonwealth Edison Co [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	(12)	(12)
PECO Energy Co [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	0	0
Baltimore Gas and Electric Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	120	120
Pepco Holdings LLC [Member] | Successor [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	112	172
Delmarva Power and Light Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	21	37
Potomac Electric Power Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	59	80
Atlantic City Electric Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 0	$ 22

Nuclear Decommissioning - Rollf

Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]	$ 112	$ 109
Asset Retirement Obligation, Revision of Estimate			0
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]	110	$ 109
Current portion of ARO				$ 10
Exelon Generation Co L L C [Member] | Nuclear Decommissioning [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Nuclear Decommissioning ARO, Beginning Balance	[2]	8,734
Asset Retirement Obligation, Accretion Expense		109
Asset Retirement Obligation, Liabilities Settled		(1)
Asset Retirement Obligation, Period Increase (Decrease)		525
Asset Retirement Obligation, Revision of Estimate		417
Nuclear Decommissioning ARO, Ending Balance	[2]	9,259
Current portion of ARO		$ 11
[1]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income
[2]	Includes $11 million and $10 million for the current portion of the ARO at March 31, 2017 and December 31, 2016, respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets.

Nuclear Decommissioning (Detail

Nuclear Decommissioning (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent	$ 3	$ 14
Decommissioning Fund Investments	12,362	11,061
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent	3	14
Proceeds from Customers	4	24
Decommissioning Fund Investments	12,362	$ 11,061
Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent	$ 112

Nuclear Decommissioning - Unrea

Nuclear Decommissioning - Unrealized Gains on NDT Funds (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Unrealized Losses On Nuclear Decommissioning Trust Fund Investment [Line Items]
Net unrealized gains (losses) on decommissioning trust funds - regulatory agreement units	[1]	$ 222	$ 79
Net unrealized gains (losses) on decommissioning trust funds - non-regulatory agreement units	[2],[3]	166	$ 52
Unrealized Gain Loss Investment Income Pledged Assets		$ (1)
[1]	Net unrealized gains 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 and $2 million of net unrealized gains (losses) related to the Zion Station pledged assets for the three months ended March 31, 2017 and 2016 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 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 - Asset

Nuclear Decommissioning - Assets, Payables and Withdrawals by ZionSolutions (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Nuclear Decommissioning Additional Narrative Information [Line Items]
Pledged assets for Zion Station decommissioning		$ 95		$ 113
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Pledged assets for Zion Station decommissioning		95		113
Payable to Zion Solutions	[1]	88		104
Current portion of payable to Zion Solutions	[2]	85		90
Withdrawals by Zion Solutions to pay decommissioning costs		895	$ 878
Nuclear Decommissioning Asset Retirement Obligation [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Pledged assets for Zion Station decommissioning		$ 95		$ 113
[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.
[2]	Included in Other current liabilities within Exelon’s and Generation’s Consolidated Balance Sheets.

Retirement Benefits - Narrative

Retirement Benefits - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
Defined Benefit Plan Disclosure [Line Items]
Increase in regulatory assets due valuation received by Exelon for its legacy pension and other postretirement benefit obligations.	$ 57
Increase in regulatory liabilities due to updated valuation of Exelon's legacy pension and postretirement benefit obligations	4
Increase (Decrease) in Pension Plan Obligations	92
Increase (Decrease) in Postretirement Obligations	57
Defined Benefit Plan, Accumulated Other Comprehensive Income Net Gains (Losses), after Tax	(59)
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Pension Plan Obligations	38
Increase (Decrease) in Postretirement Obligations	$ 11
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on assets	7.00%
Discount rate	4.04%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on assets	6.58%
Discount rate	4.04%

Retirement Benefits - Calculati

Retirement Benefits - Calculation of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions		Mar. 31, 2016	Mar. 31, 2017		Mar. 31, 2016		Mar. 23, 2016
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			$ 157		$ 136
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost			95	[1]	78
Interest cost			210	[1]	190
Expected return on assets			(299)	[1]	(263)
Amortization of:
Prior service cost (benefit)			0	[1]	3
Defined Benefit Plan, Actuarial Gain (Loss)			152	[1]	127
Net periodic benefit cost			158	[1]	135
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost			26	[1]	26
Interest cost			45	[1]	43
Expected return on assets			(41)	[1]	(38)
Amortization of:
Prior service cost (benefit)			(47)	[1]	(44)
Defined Benefit Plan, Actuarial Gain (Loss)			16	[1]	14
Net periodic benefit cost			(1)	[1]	1
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			7	[2]	8	[2]	$ 7
Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense							23
Pepco Holdings LLC [Member] | Successor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense		$ 3	24
Pepco Holdings LLC [Member] | Pension Plan, Defined Benefit [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost							12
Interest cost							26
Expected return on assets							(30)
Amortization of:
Prior service cost (benefit)							0
Defined Benefit Plan, Actuarial Gain (Loss)							14
Net periodic benefit cost							22
Pepco Holdings LLC [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost							1
Interest cost							6
Expected return on assets							(5)
Amortization of:
Prior service cost (benefit)							(3)
Defined Benefit Plan, Actuarial Gain (Loss)							2
Net periodic benefit cost							1
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			3	[2]	5	[2]	4
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			3	[2]	4	[2]	3
Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense	[3]		12		14
Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			$ 11	[2],[3]	$ 9	[2],[3]	$ 9
[1]	(a)PHI net periodic benefit costs for the period prior to the merger are not included in the table above.
[2]	Pepco's, DPL's, ACE's and PHISCO's pension and postretirement benefit costs for the three months ended March 31, 2016 include $7 million, $4 million, $3 million and $9 million, respectively, of costs incurred prior to the closing of Exelon’s merger with PHI on March 23, 2016.
[3]	These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO, BGE, PHI, Pepco, DPL or ACE amounts above.

Retirement Benefits - Allocated

Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions		Mar. 31, 2016	Mar. 31, 2017		Mar. 31, 2016		Mar. 23, 2016
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			$ 157		$ 136
Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense	[1]		12		14
Pepco Holdings LLC [Member] | Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			11	[1],[2]	9	[1],[2]	$ 9
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			54		54
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			44		41
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			7		8
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			16		16
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			7	[2]	8	[2]	7
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			3	[2]	5	[2]	4
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense			3	[2]	$ 4	[2]	3
Predecessor [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense							$ 23
Successor [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefit Expense		$ 3	$ 24
[1]	These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO, BGE, PHI, Pepco, DPL or ACE amounts above.
[2]	Pepco's, DPL's, ACE's and PHISCO's pension and postretirement benefit costs for the three months ended March 31, 2016 include $7 million, $4 million, $3 million and $9 million, respectively, of costs incurred prior to the closing of Exelon’s merger with PHI on March 23, 2016.

Retirement Benefits - Defined C

Retirement Benefits - Defined Contribution Savings Plans (Details) - USD ($) $ in Millions		Mar. 31, 2016	Mar. 31, 2017		Mar. 31, 2016		Mar. 23, 2016
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions			$ 30		$ 26
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions			14		12
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions			7		6
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions			2		2
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions			2		1
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions			1	[1]	1	[1]	$ 1
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions			1	[1]	1	[1]	1
Predecessor [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions							3
Successor [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		$ 0
Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[2]		2		5
Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1],[2]		$ 1		$ 1		$ 1
[1]	Pepco's, DPL's and PHISCO's matching contributions for the three months ended March 31, 2016 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 for the three months ended March 31, 2016.
[2]	These amounts primarily represent amounts billed to Exelon and PHI's subsidiaries through intercompany allocations. These costs are not included in the Generation, ComEd, PECO, BGE, Pepco and DPL amounts above.

Severance - Ongoing Severance P

Severance - Ongoing Severance Plans (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 4	$ 2
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	3	2
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	$ 1	$ 0
[1]	he amounts above for Generation include $1 million for amounts billed by BSC through intercompany allocations for both the three months ended March 31, 2017 and 2016. Amounts billed by BSC to ComEd were immaterial.

Severance Severance - Cost Mana

Severance Severance - Cost Management Program-Related (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ (4)		$ (2)
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		(1)	[1]	(17)	[2]
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[3]	(3)		(2)
Exelon Generation Co L L C [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		(1)	[1]	(12)	[2]
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		(1)
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				(7)
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[3]	(1)		0
Commonwealth Edison Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		0	[1]	(3)	[2]
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				(3)
PECO Energy Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		0	[1]	(1)	[2]
PECO Energy Co [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				(1)
Baltimore Gas and Electric Company [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 0	[1]	(1)	[2]
Baltimore Gas and Electric Company [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ (1)
[1]	(a)Amounts billed by BSC through intercompany allocations for the three months ended March 31, 2017 were immaterial.
[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 three months ended March 31, 2016.
[3]	he amounts above for Generation include $1 million for amounts billed by BSC through intercompany allocations for both the three months ended March 31, 2017 and 2016. Amounts billed by BSC to ComEd were immaterial.

Severance - PHI Merger (Details

Severance - PHI Merger (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 4	$ 2
PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		52
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	3	2
Exelon Generation Co L L C [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		10
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			9
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	$ 1	0
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] | 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] | 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] | Successor [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		37
Potomac Electric Power Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		18
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			18
Delmarva Power and Light Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		11
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			11
Atlantic City Electric Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		8
Atlantic City Electric Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			$ 8
[1]	(a)The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $9 million, $2 million, $1 million, $1 million, $18 million, $11 million and $8 million, respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the three months ended March 31, 2016.
[2]	he amounts above for Generation include $1 million for amounts billed by BSC through intercompany allocations for both the three months ended March 31, 2017 and 2016. Amounts billed by BSC to ComEd were immaterial.

Severance - Severance Liabiliti

Severance - Severance Liabilities (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Restructuring Reserve [Roll Forward]
Severance Costs		$ 4	$ 2
Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		88
Severance Costs	[1]	3
Payments for Restructuring		(10)
Ending Balance		81
Exelon Generation Co L L C [Member]
Restructuring Reserve [Roll Forward]
Severance Costs	[2]	3	2
Exelon Generation Co L L C [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		36
Severance Costs	[1]	1
Payments for Restructuring		(3)
Ending Balance		34
Commonwealth Edison Co [Member]
Restructuring Reserve [Roll Forward]
Severance Costs	[2]	1	$ 0
Commonwealth Edison Co [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		3
Severance Costs	[1]	0
Payments for Restructuring		0
Ending Balance		3
PECO Energy Co [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		0
Severance Costs	[1]	0
Payments for Restructuring		0
Ending Balance		0
Baltimore Gas and Electric Company [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		0
Severance Costs	[1]	0
Payments for Restructuring		0
Ending Balance		0
Pepco Holdings LLC [Member] | Successor [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		29
Severance Costs	[1]	0
Payments for Restructuring		(5)
Ending Balance		24
Potomac Electric Power Company [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		0
Severance Costs	[1]	0
Payments for Restructuring		0
Ending Balance		0
Delmarva Power and Light Company [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		0
Severance Costs	[1]	0
Payments for Restructuring		0
Ending Balance		0
Atlantic City Electric Company [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance		0
Severance Costs	[1]	0
Payments for Restructuring		0
Ending Balance		$ 0
[1]	(a)Includes salary continuance and health and welfare severance benefits.
[2]	he amounts above for Generation include $1 million for amounts billed by BSC through intercompany allocations for both the three months ended March 31, 2017 and 2016. Amounts billed by BSC to ComEd were immaterial.

Severance Severance - Narrative

Severance Severance - Narrative (Details) - Cost Management Project [Member]	1 Months Ended
	Aug. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated	500
Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated	250
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated	250

Mezzanine Equity Mezzanine Equi

Mezzanine Equity Mezzanine Equity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Preferred Stock, Shares Subscribed but Unissued, Value [Abstract]
Payments to Acquire Businesses, Gross	$ 212	$ 6,645
Exelon Generation Co L L C [Member]
Redeemable Noncontrolling Interest [Line Items]
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	3
Preferred Stock, Shares Subscribed but Unissued, Value [Abstract]
Payments to Acquire Businesses, Gross	$ 212	$ 1

Changes in Accumulated Other 99

Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016		Mar. 23, 2016	Dec. 31, 2016		Dec. 31, 2015
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Net current-period OCI		$ (12)		$ 28
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		28,291					$ 27,612
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]	2		(10)
Amounts reclassified from AOCI	[1],[2]	4		3
Net current-period OCI	[1]	6		(7)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	[1]	(11)		(26)					$ (19)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]	1		(1)
Amounts reclassified from AOCI		0		0
Net current-period OCI	[1]	1		(1)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		5	[1]	2	[1]		4	[1]	3
Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications		(59)	[1]	(1)
Amounts reclassified from AOCI	[1],[2],[3]	36		34
Net current-period OCI	[1]	(23)		33
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	[1]	(2,633)		(2,532)			(2,610)		(2,565)
Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]	1		6
Amounts reclassified from AOCI		0		0
Net current-period OCI	[1]	1		6
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(29)	[1]	(34)	[1]		(30)	[1]	(40)
Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]	5		(3)
Amounts reclassified from AOCI	[1],[2]	0		0
Net current-period OCI	[1]	5		(3)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	[1]	(2)		(6)			(7)		(3)
AOCI Attributable to Parent [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]	(50)		(9)
Amounts reclassified from AOCI	[1]	(40)		37	[2]
Net current-period OCI	[1]	(10)		28
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	[1]	(2,670)		(2,596)			(2,660)		(2,624)
Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Net current-period OCI		11		(1)
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]
OCI before reclassifications	[1]	2		(8)
Amounts reclassified from AOCI	[1],[2]	4		3
Net current-period OCI	[1]	6		(5)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(13)	[1]	(26)	[1]				(21)
Exelon Generation Co L L C [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]	0		0
Amounts reclassified from AOCI		0		0
Net current-period OCI	[1]	0		0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		2	[1]	1	[1]		2		1	[1]
Exelon Generation Co L L C [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications		0		0
Amounts reclassified from AOCI		0		0
Net current-period OCI		0		0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		0		0	[1]		0		0	[1]
Exelon Generation Co L L C [Member] | Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]	1		6
Amounts reclassified from AOCI		0		0
Net current-period OCI	[1]	1		6
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		(29)	[1]	(34)	[1]		(30)	[1]	(40)
Exelon Generation Co L L C [Member] | Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]	6		(2)
Amounts reclassified from AOCI	[1],[2]	0		0
Net current-period OCI	[1]	6		(2)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	[1]	(1)		(5)			(7)		(3)
Exelon Generation Co L L C [Member] | AOCI Attributable to Parent [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]	9		(4)
Amounts reclassified from AOCI	[1]	(4)		3	[2]
Net current-period OCI	[1]	13		(1)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	[1]	(41)		(64)			(54)		(63)
PECO Energy Co [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications		0		0	[1]
Amounts reclassified from AOCI		0		0
Net current-period OCI		0		0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	[1]	0		0			0		0
PECO Energy Co [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications		0		0	[1]
Amounts reclassified from AOCI		0		0
Net current-period OCI		0		0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		1	[1]	1	[1]		1	[1]	1
PECO Energy Co [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications		0		0
Amounts reclassified from AOCI		0		0
Net current-period OCI		0		0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		0		0			0		0
PECO Energy Co [Member] | Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications		0		0	[1]
Amounts reclassified from AOCI		0		0
Net current-period OCI		0		0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		0		0			0		0
PECO Energy Co [Member] | Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications		0		0	[1]
Amounts reclassified from AOCI		0		0
Net current-period OCI		0		0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		0		0			0		0
PECO Energy Co [Member] | AOCI Attributable to Parent [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications	[1]	0		0
Amounts reclassified from AOCI		0	[1]	0
Net current-period OCI		0	[1]	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	[1]	$ 1		1			$ 1		1
PEPCO Holdings Inc [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI				$ 1
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications						$ 0
Amounts reclassified from AOCI						0
Net current-period OCI						0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest						(8)			(8)
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications						0
Amounts reclassified from AOCI						0
Net current-period OCI						0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest						0			0
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications						0
Amounts reclassified from AOCI						1
Net current-period OCI						1
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest						(27)			(28)
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications						0
Amounts reclassified from AOCI						0
Net current-period OCI						0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest						0			0
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications						0
Amounts reclassified from AOCI						0
Net current-period OCI						0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest						0			0
PEPCO Holdings Inc [Member] | Predecessor [Member] | AOCI Attributable to Parent [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
OCI before reclassifications						0
Amounts reclassified from AOCI						1
Net current-period OCI						1
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest						$ (35)			$ (36)
[1]	All amounts are net of tax and noncontrolling interest. Amounts in parenthesis represent a decrease in AOCI.
[2]	See next tables for details about these reclassifications.
[3]	Amounts in parenthesis represent a decrease in net income.

Changes in Accumulated Other100

Changes in Accumulated Other Comprehensive Income - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016	Mar. 23, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes		$ (215)		$ (184)
Other, net		283		114
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(40)		(37)
Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]	(58)		(56)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1],[2],[3]	(36)		(34)
Reclassification from AOCI, Current Period, Tax		(22)	[1]	(22)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		0		0
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		0		0
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	[1]	3		2
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	[1]	(4)		(3)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	[1]	(7)		(5)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Income (Expense), Nonoperating, Net		(7)		(5)
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1],[4]	(81)		(76)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		23		20
Exelon Generation Co L L C [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes		(127)		(151)
Other, net		259		93
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	[1]	(4)		(3)
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Income (Expense), Nonoperating, Net		(7)		(5)
Exelon Generation Co L L C [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes		0
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		0		0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		0		0
Reclassification from AOCI, Current Period, Tax		0		0
Exelon Generation Co L L C [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		0		0
Exelon Generation Co L L C [Member] | Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		0		0
Exelon Generation Co L L C [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes		3	[1]	(2)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	[1]	(4)		(3)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	[1]	(7)		(5)
Exelon Generation Co L L C [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax				0
Exelon Generation Co L L C [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		0
Exelon Generation Co L L C [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		$ 0		0
PEPCO Holdings Inc [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				(1)
PEPCO Holdings Inc [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Income (Expense), Nonoperating, Net				0
PEPCO Holdings Inc [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax				(1)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax				(1)
Reclassification from AOCI, Current Period, Tax				0
PEPCO Holdings Inc [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income taxes				0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest				0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest				0
PEPCO Holdings Inc [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax				$ (1)
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax					$ (1)
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax					0
PEPCO Holdings Inc [Member] | Predecessor [Member] | Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax					$ 0
[1]	Amounts in parenthesis represent a decrease in net income.
[2]	All amounts are net of tax and noncontrolling interest. Amounts in parenthesis represent a decrease in AOCI.
[3]	See next tables for details about these reclassifications.
[4]	This AOCI component is included in the computation of net periodic pension and OPEB cost (see Note 13 — Retirement Benefits for additional details).

Changes in Accumulated Other101

Changes in Accumulated Other Comprehensive Income - Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 23, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ (28)	$ (17)
PEPCO Holdings Inc [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax			$ 0
Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(4)	4
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(1)	3
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(1)	2
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in unrealized (loss)/gain on equity investments	(4)	2
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in unrealized (loss)/gain on equity investments	(3)	2
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	0	0
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 (Loss), Tax	32	30
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 (Loss), Tax	10	7
Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ (1)	$ 1

Common Stock - Narrative (Detai

Common Stock - Narrative (Details) $ in Millions	Mar. 31, 2017USD ($)
Common Stock [Abstract]
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value	$ 1,150

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
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 995	$ 173
Weighted average common shares outstanding — basic	928	923
Assumed exercise and/or distributions of stock-based awards	2	2
Weighted average common shares outstanding — diluted	930	925

Earnings Per Share and Equit104

Earnings Per Share and Equity - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Statement Of Equity Line Item [Line Items]
Treasury Stock, Shares held	34,743,157		34,743,157
Treasury Stock, Value	$ (2,327)		$ (2,327)
Equity units issued [Member]
Statement Of Equity Line Item [Line Items]
Stock options not included in the calculation of diluted common shares outstanding		4,000,000
Employee Stock Option [Member]
Statement Of Equity Line Item [Line Items]
Stock options not included in the calculation of diluted common shares outstanding	9,000,000	13,000,000

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Equity Investment Commitments (Details) $ in Millions	Mar. 31, 2017USD ($)
Guarantor Obligations [Line Items]
Other Commitment	$ 3,212
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	2,404
Equity Unit Purchase Agreements [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment, Due in Next Twelve Months	9
Other Commitment, Due in Second Year	7
Other Commitment, Due in Third Year	3
Other Commitment	$ 19

Commitments and Contingencie106

Commitments and Contingencies - Commitments Narrative (Details) $ in Millions	1 Months Ended		3 Months Ended
	Nov. 30, 2015USD ($)	Sep. 23, 2015USD ($)	Mar. 31, 2017USD ($)MW	Dec. 31, 2016USD ($)	Mar. 31, 2016USD ($)	Jun. 30, 2014USD ($)
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 48
Noncash Merger Related Costs					$ 503
Power Volume | MW			220
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Noncash Merger Related Costs					3
Costs Incurred, Development Costs			$ 456
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Noncash Merger Related Costs					0
PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Noncash Merger Related Costs					0
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Oil and Gas Property, Lease Operating Expense				$ 29
Occupancy, Net	$ 42	$ 12
Noncash Merger Related Costs					$ 0
Operating Leases, Income Statement, Initial Direct Costs				25
Operating Expenses				$ 28
Minimum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Business Acquisition, Development Of New Generation Cost			450
Maximum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Business Acquisition, Development Of New Generation Cost			$ 550
Merger Commitment [Member]
Guarantor Obligations [Line Items]
Investments						$ 1,000
Merger Commitment [Member] | Minimum [Member]
Guarantor Obligations [Line Items]
Investments						0
Merger Commitment [Member] | Maximum [Member]
Guarantor Obligations [Line Items]
Investments						$ 0

Commitments and Contingencie107

Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Mar. 31, 2017USD ($)
Guarantor Obligations [Line Items]
Other Commitment	$ 3,212
Guarantor Obligations, Maximum Exposure, Undiscounted	48
Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,527
Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	628
Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,038
GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	19
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	2,404
Exelon Generation Co L L C [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,440
Exelon Generation Co L L C [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Exelon Generation Co L L C [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	964
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	219
Commonwealth Edison Co [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	14
Commonwealth Edison Co [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	200
Commonwealth Edison Co [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	5
PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	208
PECO Energy Co [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	23
PECO Energy Co [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	178
PECO Energy Co [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	7
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	266
Baltimore Gas and Electric Company [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	5
Baltimore Gas and Electric Company [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	250
Baltimore Gas and Electric Company [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	11
PEPCO Holdings Inc [Member]
Guarantor Obligations [Line Items]
Other Commitment	36
PEPCO Holdings Inc [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1
PEPCO Holdings Inc [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
PEPCO Holdings Inc [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	16
PEPCO Holdings Inc [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	19
Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	15
Guarantor Obligations, Maximum Exposure, Undiscounted	14
Potomac Electric Power Company [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1
Potomac Electric Power Company [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Potomac Electric Power Company [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	9
Potomac Electric Power Company [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	5
Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	8
Guarantor Obligations, Maximum Exposure, Undiscounted	13
Atlantic City Electric Company [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Atlantic City Electric Company [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Atlantic City Electric Company [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	3
Atlantic City Electric Company [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	5
Delmarva Power and Light Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	11
Guarantor Obligations, Maximum Exposure, Undiscounted	17
Delmarva Power and Light Company [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Delmarva Power and Light Company [Member] | Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	0
Delmarva Power and Light Company [Member] | Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	4
Delmarva Power and Light Company [Member] | GuaranteedLeaseResidualValues [Member]
Guarantor Obligations [Line Items]
Other Commitment	$ 7

Commitments and Contingencie108

Commitments and Contingencies - Contingencies Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)MW
Commitments And Contingencies Additional Narrative Information [Line Items]
BusinessAcquisitionResidualcommitment | MW	55
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 48
Loss Contingency, Loss in Period	0
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Required nuclear liability insurance per site	0
Loss Contingency, Undiscounted Amount of Insurance-related Assessment Liability	450
Current Liability Per Incident	13,400
Maximum liability per nuclear incident	13,000
Mutual Replacement Power Cost Insurance Maximum Retrospective Premium Obligation	3,200
Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	14
Nuclear Insurance Premiums [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Nuclear financial protection pool value	2,800
Nuclear Insurance Premiums [Member] | Maximum [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Nuclear financial protection pool value	$ 0

Commitments and Contingencie109

Commitments and Contingencies - Environmental Issues Narrative (Details) $ in Millions	1 Months Ended	3 Months Ended
	Aug. 31, 2015gal	Mar. 31, 2017USD ($)MGPSiteOpen_claimgal
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total number of MGP sites | MGPSite		18
Mgp Site Contingency Monitoring Count | MGPSite		24
Approved clean-up | MGPSite		42
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total number of MGP sites | MGPSite		17
Mgp Site Contingency Monitoring Count | MGPSite		9
Approved clean-up | MGPSite		26
Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Approved clean-up | MGPSite		13
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Component Amount		$ 90
Mutual Replacement Power Cost Insurance Maximum Retrospective Premium Obligation		3,200
Site Contingency, Loss Exposure Not Accrued, Best Estimate		90
Consent decree penalty		$ 1.6
Exelon Generation Co L L C [Member] | Minimum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, New Claims Filed, Number | Open_claim		225
Exelon Generation Co L L C [Member] | Maximum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, New Claims Filed, Number | Open_claim		650,000,000
PEPCO Holdings Inc [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Sites under study/remediation | MGPSite		9
Environmental Remediation Expense		$ 10
PEPCO Holdings Inc [Member] | Minimum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		7
PEPCO Holdings Inc [Member] | Maximum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		18
Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
QuantityOfMineralOilSPill | gal	6,100
Potomac Electric Power Company [Member] | Minimum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Anticipated Cost		3
Potomac Electric Power Company [Member] | Maximum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Environmental Exit Costs, Anticipated Cost		$ 6
Delmarva Power and Light Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total number of MGP sites | gal		2
Calpine Corporation [Member] | Maximum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		$ 10
Sixty-Eighth Street Dump [Member] | Baltimore Gas and Electric Company [Member] | Minimum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		50
Sixty-Eighth Street Dump [Member] | Baltimore Gas and Electric Company [Member] | Maximum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		64
Rossville Ash Site [Member] | Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		4
Sauer Dump Site [Member] | Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		$ 1.7

Commitments and Contingencie110

Commitments and Contingencies - Litigation and Regulatory Matters (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)Open_claim	Mar. 31, 2017USD ($)
Asbestos Loss Contingency [Abstract]
Open asbestos liability claims | Open_claim	240
Exelon Generation Co L L C [Member]
Asbestos Loss Contingency [Abstract]
Asbestos liability reserve	$ 83	$ 82
Asbestos liability reserve related to open claims		23
Asbestos liability reserve related to anticipated claims		$ 59
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency, Damages Sought, Value	$ 14

Commitments and Contingencie111

Commitments and Contingencies - Schedule of Accruals for Environmental Matters (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Total Accrual For Environmental Loss Contingencies [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	$ 425	$ 429
Total Accrual For Environmental Loss Contingencies [Member] | Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	71	72
Total Accrual For Environmental Loss Contingencies [Member] | Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	288	292
Total Accrual For Environmental Loss Contingencies [Member] | PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	33	33
Total Accrual For Environmental Loss Contingencies [Member] | Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	4	2
Total Accrual For Environmental Loss Contingencies [Member] | PEPCO Holdings Inc [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	29	30
Total Accrual For Environmental Loss Contingencies [Member] | Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	26	27
Total Accrual For Environmental Loss Contingencies [Member] | Delmarva Power and Light Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	2	2
Total Accrual For Environmental Loss Contingencies [Member] | Atlantic City Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	1	1
Accrual For MGP Investigation And Remediation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	319	325
Accrual For MGP Investigation And Remediation [Member] | Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	0
Accrual For MGP Investigation And Remediation [Member] | Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	286	291
Accrual For MGP Investigation And Remediation [Member] | PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	31	31
Accrual For MGP Investigation And Remediation [Member] | Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	2	2
Accrual For MGP Investigation And Remediation [Member] | PEPCO Holdings Inc [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	1
Accrual For MGP Investigation And Remediation [Member] | Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	0
Accrual For MGP Investigation And Remediation [Member] | Delmarva Power and Light Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	1
Accrual For MGP Investigation And Remediation [Member] | Atlantic City Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	$ 0	$ 0

Supplemental Financial Infor112

Supplemental Financial Information - Narrative (Details) - PECO Energy Co [Member] - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net	$ 9	$ 9
Financing Receivable, Allowance for Credit Losses	11	13
Low To Medium Risk [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses	0	1
Risk Level, Medium [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses	3	3
Risk Level, High [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses	$ 8	$ 9

Supplemental Financial Infor113

Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions		Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016		Mar. 23, 2016
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes			$ 224	$ 153
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units			68	34	[1]
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units			32	21	[1]
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units			222	79
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement			166	52
Net unrealized income (losses) on pledged assets			(1)	2
Regulatory offset to decommissioning trust fund-related activities			(234)	(95)	[2]
Total decommissioning-related activities			253	93
Investment income			2	6
Long-term lease income				4
Unrecognized Tax Benefits Interest Income			1	1
AFUDC - equity			17	8
Gains (Losses) on Extinguishment of Debt	[3]			(2)
Other Income			10	4
Other, net			283	114
Exelon Generation Co L L C [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes			32	28
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]		68	34
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]		32	21
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units			222	79
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement			166	52
Net unrealized income (losses) on pledged assets			(1)	2
Regulatory offset to decommissioning trust fund-related activities	[2]		(234)	(95)
Total decommissioning-related activities			253	93
Investment income			2	1
Unrecognized Tax Benefits Interest Income			0	0
Gains (Losses) on Extinguishment of Debt				(2)
Other Income			4	1
Other, net			259	93
Commonwealth Edison Co [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes			59	59
Decommissioning-Related Activities [Abstract]
Investment income			0
Unrecognized Tax Benefits Interest Income			0	0
AFUDC - equity			2	2
Other Income			2	2
Other, net			4	4
PECO Energy Co [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes			31	35
Decommissioning-Related Activities [Abstract]
Investment income			0	0
Unrecognized Tax Benefits Interest Income			0	0
AFUDC - equity			2	2
Other Income			0	0
Other, net			2	2
Baltimore Gas and Electric Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes			26	24
Decommissioning-Related Activities [Abstract]
Investment income			0	1	[4]
Unrecognized Tax Benefits Interest Income			0
AFUDC - equity			4	3
Other Income			0	0
Other, net			4	4
Potomac Electric Power Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes			71	79
Decommissioning-Related Activities [Abstract]
Investment income			0	0
Long-term lease income				0
Unrecognized Tax Benefits Interest Income			0	1
AFUDC - equity			5	4
Other Income			3	4
Other, net			8	9
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes		$ 7	76
Decommissioning-Related Activities [Abstract]
Investment income		0	0
Long-term lease income		0
Unrecognized Tax Benefits Interest Income		0	0
AFUDC - equity		1	9
Other Income		1	4
Other, net		$ 2	13
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes						$ 77
Decommissioning-Related Activities [Abstract]
Investment income						0
Long-term lease income						0
Unrecognized Tax Benefits Interest Income						0
AFUDC - equity						7
Other Income						(11)
Other, net						$ (4)
Delmarva Power and Light Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes			5	5
Decommissioning-Related Activities [Abstract]
Investment income			0	0
Long-term lease income				0
Unrecognized Tax Benefits Interest Income			0	0
AFUDC - equity			2	1
Other Income			1	2
Other, net			3	3
Atlantic City Electric Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes			0	0
Decommissioning-Related Activities [Abstract]
Investment income			0	0
Long-term lease income				0
Unrecognized Tax Benefits Interest Income			0	1
AFUDC - equity			2	2
Other Income			0	1
Other, net			$ 2	$ 4
[1]	Includes investment income and realized gains and losses on sales of investments of the 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 of the Exelon 2016 Form 10-K for additional information regarding the accounting for nuclear decommissioning.
[3]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246OEU0NzY4ODA4OERBNTYzQUFFQjI2MDMyNzhGRDg2RUUM}
[4]	.

Supplemental Financial Infor114

Supplemental Financial Information - Cash Flow (Details) - USD ($) $ in Millions		Mar. 31, 2016		Mar. 31, 2017		Mar. 31, 2016		Mar. 23, 2016	Dec. 31, 2016
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]			$ 754		$ 606
Regulatory assets	[1]			128		65
Amortization of intangible assets, net	[1]			14		14
Amortization of Power Contracts Emission Credits	[2]			2		(14)
Asset retirement obligation accretion						0
Total depreciation, amortization and accretion				1,274		1,063
Amortization of Nuclear Fuel Lease	[3]			264		283
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				157		136
Gain (loss) on equity method investments				10		3
Provision for uncollectible accounts				34		41
Stock-based compensation costs				31		44
Other Decommissioning Related Activity	[4]			(84)		(55)
Energy-related options	[5]			(4)		(9)
Amortization of regulatory asset related to debt costs				2		1
Amortization of rate stabilization deferral				(14)		20
Amortization of debt fair value adjustment				(5)		(3)
Discrete impacts from EIMA	[6]			(24)		(14)
Amortization of debt costs				9		8
Merger related commitments						503
Inventory Write-down				2		1
InventoryLCMReservePeriodCharge						36
Restructuring Costs						69
Other				4		23
Total other noncash operating activities				118		804
Changes In Other Assets and Liabilities [Abstract]
Total changes in other assets and liabilities				(439)		(311)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						0
Payments to Acquire Businesses, Gross				212		6,645
Capital Expenditures Incurred but Not yet Paid				(298)		(290)
Capitalized Costs, Asset Retirement Costs									$ 62
Asset Retirement Obligation, Accretion Expense	[7]			112		109
Asset Retirement Obligation, Revision of Estimate						0
Stock Issued				2		1
Capital Project [Member]
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired				10		31
Exelon Generation Co L L C [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]			289		278
Amortization of intangible assets, net	[1]			13		11
Amortization of Power Contracts Emission Credits	[2]			2		(14)
Total depreciation, amortization and accretion				678		667
Amortization of Nuclear Fuel Lease	[3]			264		283
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				54		54
Gain (loss) on equity method investments				10		3
Provision for uncollectible accounts				9		6
Stock-based compensation costs				0		0
Other Decommissioning Related Activity	[4]			(84)		(55)
Energy-related options	[5]			(4)		(9)
Amortization of regulatory asset related to debt costs				0		0
Amortization of rate stabilization deferral				0		0
Amortization of debt fair value adjustment				(3)		(3)
Discrete impacts from EIMA				0		0
Amortization of debt costs				4		4
Merger related commitments						3
Inventory Write-down				1		1
InventoryLCMReservePeriodCharge						36
Restructuring Costs						4
Other				3		7
Total other noncash operating activities				(10)		51
Changes In Other Assets and Liabilities [Abstract]
Total changes in other assets and liabilities				(167)		(148)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						119
Payments to Acquire Businesses, Gross				212		1
Capital Expenditures Incurred but Not yet Paid				(354)		(234)
Capitalized Costs, Asset Retirement Costs									62
Asset Retirement Obligation, Accretion Expense	[7]			110		109
Commonwealth Edison Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]			190		170
Regulatory assets	[1]			18		19
Total depreciation, amortization and accretion				208		189
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				44		41
Gain (loss) on equity method investments				0		0
Provision for uncollectible accounts				7		9
Stock-based compensation costs				0		0
Other Decommissioning Related Activity				0		0
Energy-related options				0		0
Amortization of regulatory asset related to debt costs				1		1
Amortization of rate stabilization deferral				0		0
Amortization of debt fair value adjustment				0		0
Discrete impacts from EIMA	[6]			(24)		(14)
Amortization of debt costs				1		1
Merger related commitments						0
Inventory Write-down				1		0
InventoryLCMReservePeriodCharge						0
Other				1		(6)
Total other noncash operating activities				31		32
Changes In Other Assets and Liabilities [Abstract]
Total changes in other assets and liabilities				(49)		14
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						0
Capital Expenditures Incurred but Not yet Paid				25		25
Capitalized Costs, Asset Retirement Costs									0
Asset Retirement Obligation, Accretion Expense	[7]			0
Commonwealth Edison Co [Member] | Indemnification Agreement [Member]
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Contribution of Property	[8]					1
PECO Energy Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]			64		60
Regulatory assets	[1]			7		7
Total depreciation, amortization and accretion				71		67
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				7		8
Gain (loss) on equity method investments				0		0
Provision for uncollectible accounts				17		16
Stock-based compensation costs				0		0
Other Decommissioning Related Activity				0		0
Energy-related options				0		0
Amortization of regulatory asset related to debt costs				0		0
Amortization of rate stabilization deferral				0		0
Amortization of debt fair value adjustment				0		0
Discrete impacts from EIMA				0		0
Amortization of debt costs				0		1
Merger related commitments						0
Inventory Write-down				0		0
InventoryLCMReservePeriodCharge						0
Other				(1)		(1)
Total other noncash operating activities				23		24
Changes In Other Assets and Liabilities [Abstract]
Total changes in other assets and liabilities				(85)		(95)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						0
Capital Expenditures Incurred but Not yet Paid				0		(65)
Capitalized Costs, Asset Retirement Costs									0
Asset Retirement Obligation, Accretion Expense	[7]			0
Baltimore Gas and Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]			80		75
Regulatory assets	[1]			48		34
Total depreciation, amortization and accretion				128		109
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				16		16
Gain (loss) on equity method investments				0		0
Provision for uncollectible accounts				5		12
Stock-based compensation costs				0		0
Other Decommissioning Related Activity				0		0
Energy-related options				0		0
Amortization of regulatory asset related to debt costs				0		0
Amortization of rate stabilization deferral				7		20
Amortization of debt fair value adjustment				0		0
Discrete impacts from EIMA				0		0
Amortization of debt costs				0		1
Merger related commitments						0
Inventory Write-down				0		0
InventoryLCMReservePeriodCharge						0
Other				(4)		(5)
Total other noncash operating activities				24		44
Changes In Other Assets and Liabilities [Abstract]
Total changes in other assets and liabilities				(52)		(30)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						0
Capital Expenditures Incurred but Not yet Paid				41		(4)
Capitalized Costs, Asset Retirement Costs									0
Asset Retirement Obligation, Accretion Expense				0
Potomac Electric Power Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]			50		42
Regulatory assets	[1]			32		33
Amortization of intangible assets, net	[1]			0		0
Amortization of Power Contracts Emission Credits	[2]			0		0
Total depreciation, amortization and accretion				82		75
Amortization of Nuclear Fuel Lease	[3]			0		0
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				7	[9]	8	[9]	$ 7
Gain (loss) on equity method investments				0		0
Provision for uncollectible accounts				(5)		5
Stock-based compensation costs				0		0
Other Decommissioning Related Activity				0		0
Energy-related options				0		0
Amortization of regulatory asset related to debt costs				0		1
Amortization of rate stabilization deferral				(15)		1
Amortization of debt fair value adjustment				0		0
Discrete impacts from EIMA				0		0
Amortization of debt costs				0		0
Merger related commitments						138
Inventory Write-down				0		1
Other				(2)		(1)
Total other noncash operating activities				(15)		153
Changes In Other Assets and Liabilities [Abstract]
Total changes in other assets and liabilities				(37)		(9)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						0
Capital Expenditures Incurred but Not yet Paid				(6)		9
Capitalized Costs, Asset Retirement Costs									0
Asset Retirement Obligation, Accretion Expense	[7]			0		0
Delmarva Power and Light Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]			30		27
Regulatory assets	[1]			9		12
Amortization of intangible assets, net	[1]			0		0
Amortization of Power Contracts Emission Credits	[2]			0		0
Asset retirement obligation accretion						4
Total depreciation, amortization and accretion				39		39
Amortization of Nuclear Fuel Lease	[3]			0		0
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				3	[9]	5	[9]	4
Gain (loss) on equity method investments				0		0
Provision for uncollectible accounts				(1)		5
Stock-based compensation costs				0		0
Other Decommissioning Related Activity				0		0
Energy-related options				0		0
Amortization of regulatory asset related to debt costs				0		0
Amortization of rate stabilization deferral				(6)		4
Amortization of debt fair value adjustment				0		0
Discrete impacts from EIMA				0		0
Amortization of debt costs				0		0
Merger related commitments						100
Inventory Write-down				0		1
Other				(3)		(1)
Total other noncash operating activities				(7)		118
Changes In Other Assets and Liabilities [Abstract]
Total changes in other assets and liabilities				(23)		(8)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						0
Capital Expenditures Incurred but Not yet Paid				9		8
Capitalized Costs, Asset Retirement Costs									0
Asset Retirement Obligation, Accretion Expense	[7]			0		0
Asset Retirement Obligation, Revision of Estimate						4
Atlantic City Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]			21		20
Regulatory assets	[1]			14		20
Amortization of intangible assets, net	[1]			0		0
Amortization of Power Contracts Emission Credits	[2]			0		0
Asset retirement obligation accretion						2
Total depreciation, amortization and accretion				35		40
Amortization of Nuclear Fuel Lease	[3]			0		0
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				3	[9]	4	[9]	3
Gain (loss) on equity method investments				0		0
Provision for uncollectible accounts				1		7
Stock-based compensation costs				0		0
Other Decommissioning Related Activity				0		0
Energy-related options				0		0
Amortization of regulatory asset related to debt costs				0		0
Amortization of rate stabilization deferral				0		0
Amortization of debt fair value adjustment				0		0
Discrete impacts from EIMA				0		0
Amortization of debt costs				0		0
Merger related commitments						120
Inventory Write-down				0		1
Other				(2)		(2)
Total other noncash operating activities				2		132
Changes In Other Assets and Liabilities [Abstract]
Total changes in other assets and liabilities				(6)		(3)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						0
Capital Expenditures Incurred but Not yet Paid				0		(9)
Capitalized Costs, Asset Retirement Costs									0
Asset Retirement Obligation, Accretion Expense	[7]			0		0
Asset Retirement Obligation, Revision of Estimate						$ 2
Pepco Holdings LLC [Member]
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG								0
Pepco Holdings LLC [Member] | Successor [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation		$ 9	[1]	112
Regulatory assets		5	[1]	55
Amortization of intangible assets, net		0	[1]	0
Amortization of Power Contracts Emission Credits		0	[2]	0
Total depreciation, amortization and accretion		14		167
Amortization of Nuclear Fuel Lease		0	[3]	0
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense		3		24
Gain (loss) on equity method investments				0
Provision for uncollectible accounts		(2)		(4)
Stock-based compensation costs		0		0
Other Decommissioning Related Activity		0		0
Energy-related options		0		0
Amortization of regulatory asset related to debt costs		0		1
Amortization of rate stabilization deferral		0		(21)
Amortization of debt fair value adjustment		0		(2)
Discrete impacts from EIMA		0		0
Amortization of debt costs		0		0
Merger related commitments		358
Inventory Write-down		0		0
Restructuring Costs		52
Other		(1)		(6)
Total other noncash operating activities		410		(8)
Changes In Other Assets and Liabilities [Abstract]
Total changes in other assets and liabilities		(25)		(75)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG		127
Capital Expenditures Incurred but Not yet Paid		(7)		(5)
Asset Retirement Obligation, Accretion Expense		0	[7]	$ 0
Business Combination, Contingent Consideration, Liability, Noncurrent									$ 45
Pepco Holdings LLC [Member] | Predecessor [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]							94
Regulatory assets	[1]							58
Amortization of intangible assets, net	[1]							0
Amortization of Power Contracts Emission Credits	[2]							0
Nuclear fuel	[3]							0
Total depreciation, amortization and accretion								152
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense								23
Gain (loss) on equity method investments								0
Provision for uncollectible accounts								16
Stock-based compensation costs								3
Other Decommissioning Related Activity								0
Energy-related options								0
Amortization of regulatory asset related to debt costs								1
Amortization of rate stabilization deferral								5
Amortization of debt fair value adjustment								0
Discrete impacts from EIMA								0
Amortization of debt costs								0
Inventory Write-down								1
Other								(3)
Total other noncash operating activities								46
Changes In Other Assets and Liabilities [Abstract]
Total changes in other assets and liabilities								(8)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid								11
Asset Retirement Obligation, Accretion Expense	[7]							$ 0
Deferred Compensation, Share-based Payments [Member] | Pepco Holdings LLC [Member]
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Payments to Acquire Businesses, Gross		29
Deferred Compensation, Share-based Payments [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Payments to Acquire Businesses, Gross		$ 29
[1]	(a)Included in Depreciation and amortization on the Registrants' Consolidated Statements of Operations and Comprehensive Income.
[2]	(b)Included in Operating revenues or Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income
[3]	Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income
[4]	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 of the Exelon 2016 Form 10-K for additional information regarding the accounting for nuclear decommissioning
[5]	Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded
[6]	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 tariff. See Note 5 — Regulatory Matters for more information
[7]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income
[8]	See Note 11— Income Taxes for discussion of the like-kind exchange tax position
[9]	Pepco's, DPL's, ACE's and PHISCO's pension and postretirement benefit costs for the three months ended March 31, 2016 include $7 million, $4 million, $3 million and $9 million, respectively, of costs incurred prior to the closing of Exelon’s merger with PHI on March 23, 2016.

Supplemental Financial Infor115

Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2017		Dec. 31, 2016
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	$ 19,716	[1]	$ 19,169	[2]
Accounts receivable, net
Allowance for uncollectible accounts	346		334
Exelon Generation Co L L C [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	10,801	[1]	10,562	[2]
Accounts receivable, net
Allowance for uncollectible accounts	97		91
Exelon Generation Co L L C [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,171		3,186
Commonwealth Edison Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	4,040		3,937
Accounts receivable, net
Allowance for uncollectible accounts	80		70
PECO Energy Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,293		3,253
Accounts receivable, net
Allowance for uncollectible accounts	72		61
Baltimore Gas and Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,311		3,254
Accounts receivable, net
Allowance for uncollectible accounts	35		32
Pepco Holdings LLC [Member] | Successor [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	281		195
Accounts receivable, net
Allowance for uncollectible accounts	61		80
Potomac Electric Power Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,090		3,050
Accounts receivable, net
Allowance for uncollectible accounts	18		29
Delmarva Power and Light Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	1,195		1,175
Accounts receivable, net
Allowance for uncollectible accounts	20		24
Atlantic City Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	1,032		1,016
Accounts receivable, net
Allowance for uncollectible accounts	$ 23		$ 27
[1]	Includes accumulated amortization of nuclear fuel in the reactor core of $3,171 million
[2]	Includes accumulated amortization of nuclear fuel in the reactor core of $3,186 million

Supplemental Financial Infor116

Supplemental Financial Information Supplemental Financial Information - Utility Taxes (Details) - USD ($) $ in Millions	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 23, 2016
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes		$ 224	$ 153
Exelon Generation Co L L C [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes		32	28
Commonwealth Edison Co [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes		59	59
PECO Energy Co [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes		31	35
Baltimore Gas and Electric Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes		26	24
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes				$ 77
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	$ 7	76
Potomac Electric Power Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes		71	79
Delmarva Power and Light Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes		5	5
Atlantic City Electric Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes		$ 0	$ 0

Segment Information - Narrative

Segment Information - Narrative (Details)	3 Months Ended
	Mar. 31, 2017Reportable_segment
Segment Reporting Information [Line Items]
Number of reportable segments	12
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	3
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	6

Segment Information - Reconcili

Segment Information - Reconciliation to Consolidated Financial Statements (Details) - USD ($) $ in Millions		Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Mar. 23, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Competitive Energy Revenue			$ 3,392	$ 3,429
Revenue from Purchased Oil and Gas			918	822
Other Operating Income			250	222
Electric Revenue			3,644	2,657
Gas Domestic Regulated Revenue			553	444
Sales Revenue, Services, Other			0	(1)
Net income (loss)			981	123
Assets			117,068			$ 114,904
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			330	268
Net income (loss)			409	257
Assets			48,609			46,974
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue			(328)	(266)
Revenue from Purchased Oil and Gas			0	0
Other Operating Income			0	0
Electric Revenue			(8)	(6)
Gas Domestic Regulated Revenue			(3)	(5)
Sales Revenue, Services, Other			(431)	(418)
Operating revenues from affiliates			0	(1)
Net income (loss)			0	(1)
Assets			(11,768)			(11,334)
Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		$ 0	(4)
Gas Domestic Regulated Revenue		0	0
Sales Revenue, Services, Other		0	0
Operating revenues from affiliates		0	(5)
Net income (loss)		12	12
Assets			(4,826)			(4,724)
Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue					$ (4)
Gas Domestic Regulated Revenue					0
Sales Revenue, Services, Other					0
Operating revenues from affiliates					(4)
Net income (loss)					0
Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue			3,720	3,695
Revenue from Purchased Oil and Gas			918	822
Other Operating Income			250	222
Electric Revenue			0	0
Gas Domestic Regulated Revenue			0	0
Sales Revenue, Services, Other			0	0
Net income (loss)			409	257
Assets			48,609			46,974
Exelon Generation Co L L C [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			328	266
Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue			0	0
Revenue from Purchased Oil and Gas			0	0
Other Operating Income			0	0
Electric Revenue			1,298	1,249
Gas Domestic Regulated Revenue			0	0
Sales Revenue, Services, Other			0	0
Net income (loss)			141	115
Assets			28,756			28,335
Commonwealth Edison Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			5	5
PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue			0	0
Revenue from Purchased Oil and Gas			0	0
Other Operating Income			0	0
Electric Revenue			590	644
Gas Domestic Regulated Revenue			206	197
Sales Revenue, Services, Other			0	0
Net income (loss)			127	124
Assets			10,932			10,831
PECO Energy Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			1	1
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue			0	0
Revenue from Purchased Oil and Gas			0	0
Other Operating Income			0	0
Electric Revenue			667	680
Gas Domestic Regulated Revenue			284	249
Sales Revenue, Services, Other			0	0
Net income (loss)			125	101
Assets			8,821			8,704
Baltimore Gas and Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			5	5
Pepco Holdings LLC [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		90	1,097
Gas Domestic Regulated Revenue		3	66
Sales Revenue, Services, Other		12	12
Operating revenues from affiliates		12	12
Net income (loss)		(309)	140
Assets			21,018			21,025
Pepco Holdings LLC [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue					1,096
Gas Domestic Regulated Revenue					57
Sales Revenue, Services, Other					0
Operating revenues from affiliates					0
Net income (loss)					19
Pepco Holdings LLC [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue			0	0
Revenue from Purchased Oil and Gas			0	0
Other Operating Income			0	0
Electric Revenue			1,097	90
Gas Domestic Regulated Revenue			66	3
Sales Revenue, Services, Other			12	12
Net income (loss)			140	(309)
Assets			21,018			21,025
Pepco Holdings LLC [Member] | Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			12	12
Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue			0	0
Revenue from Purchased Oil and Gas			0	0
Other Operating Income			0	0
Electric Revenue			0	0
Gas Domestic Regulated Revenue			0	0
Sales Revenue, Services, Other			419	405
Net income (loss)			39	(164)
Assets			10,700			10,369
Corporate and Other [Member] | Corporate, Non-Segment [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		3	0
Gas Domestic Regulated Revenue		0	0
Sales Revenue, Services, Other		12	12
Operating revenues from affiliates		12	13
Net income (loss)		22	(15)
Assets			10,785			10,804
Corporate and Other [Member] | Corporate, Non-Segment [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue					42
Gas Domestic Regulated Revenue					1
Sales Revenue, Services, Other					0
Operating revenues from affiliates					0
Net income (loss)					(44)
Corporate and Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			419	405
Segment Elimination [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			(770)	(695)
Generation Mid Atlantic [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[1]		(4)	(12)
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			2	6
Potomac Electric Power Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		40	530
Gas Domestic Regulated Revenue		0	0
Sales Revenue, Services, Other		0	0
Operating revenues from affiliates		0	1
Net income (loss)		(140)	58
Assets			7,417			7,335
Potomac Electric Power Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue					511
Gas Domestic Regulated Revenue					0
Sales Revenue, Services, Other					0
Operating revenues from affiliates					1
Net income (loss)					32
Delmarva Power and Light Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		24	296
Gas Domestic Regulated Revenue		3	66
Sales Revenue, Services, Other		0	0
Operating revenues from affiliates		0	2
Net income (loss)		(98)	57
Assets			4,191			4,153
Delmarva Power and Light Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue					279
Gas Domestic Regulated Revenue					56
Sales Revenue, Services, Other					0
Operating revenues from affiliates					2
Net income (loss)					26
Atlantic City Electric Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		23	275
Gas Domestic Regulated Revenue		0	0
Sales Revenue, Services, Other		0	0
Operating revenues from affiliates		0	1
Net income (loss)		(105)	28
Assets			3,451			$ 3,457
Atlantic City Electric Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue					268
Gas Domestic Regulated Revenue					0
Sales Revenue, Services, Other					0
Operating revenues from affiliates					1
Net income (loss)					$ 5
Commonwealth Edison Co Affiliate [Member] | Generation Midwest [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			5	5
PECO Energy Co Affiliate [Member] | Generation Mid Atlantic [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			45	79
Baltimore Gas And Electric Company Affiliate [Member] | Generation Mid Atlantic [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			134	$ 173
PotomacElectricPowerCompanyAffiliate [Member] | Generation Mid Atlantic [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		6	83
DelmarvaPowerandLightCompanyAffiliate [Member] | Generation Mid Atlantic [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		4	51
AtlanticCityElectricCompanyAffiliate [Member] | Generation Mid Atlantic [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		$ 1	$ 9
[1]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246Q0Y3NjFBOTE3OTRBNTEzRDhFNjI0REU4QUE2RDFBNEMM}

Segment Information - Generatio

Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Revenues		$ 8,757	$ 7,573
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues		1,425	1,520
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues		1,053	1,095
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues		547	470
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues		307	203
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues		191	163
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues		184	223
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues		3,707	3,674
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues		1,181	1,065
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues		4,888	4,739
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	[1],[2]	1,429	1,532
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	1,051	1,089
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	549	471
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	[1],[2]	310	218
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	192	163
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	[2],[3]	189	222
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	3,720	3,695
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Amortization of intangible assets related to commodity contracts		(3)	20
Unrealized Gain (Loss) on Securities		44	63
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	[2]	4,888	4,739
Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	[2],[4]	1,168	1,044
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		0	(1)
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[1]	(4)	(12)
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		2	6
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		(2)	(1)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[1]	(3)	(15)
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		(1)	0
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[3]	(5)	1
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		(13)	(21)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[4]	13	21
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		$ 0	$ 0
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[2]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246RDM5OTkzNTIwRTlBNTQ4OEJFQzlGRTdDMDZERTMzQUIM}
[3]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246QTZBNDlCQjFFQkUwNUI0QjgwNTJERUMxRjVGRjhFQjgM}
[4]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk4YjY2MmVjNTk5ZDQ4ZGNhYWRkOTNkYjIyYTc3MzFkfFRleHRTZWxlY3Rpb246OUZFMzMxN0MyRkRCNUZCRjg4REJDODEyRjhCMjQyRDIM}

Segment Information - Genera120

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	$ 773	$ 841
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	715	718
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	111	81
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	153	130
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	69	61
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	64	76
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	1,885	1,907
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	205	390
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	2,090	2,297
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	18	9
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	11	3
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(4)	(5)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	0	(11)
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(25)	(20)
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(44)	(10)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(44)	(34)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	44	34
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	0	0
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	755	832
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	704	715
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	115	86
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	153	141
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	94	81
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	108	86
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	1,929	1,941
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	161	356
Amortization Of Intangible Assets Related To Commodity Contracts For Revenue Net Purchased Power And Fuel	(3)	19
Unrealized Gain on Securities	(49)	103
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	$ 2,090	$ 2,297

Subsequent Event (Details)

Subsequent Event (Details) - Subsequent Event [Member]	May 02, 2017USD ($)
Minimum [Member]
Subsequent Event [Line Items]
Asset Impairment Charges	$ 300
Maximum [Member]
Subsequent Event [Line Items]
Asset Impairment Charges	$ 400

Uncategorized Items - exc-20170

Label	Element	Value
Delmarva Power and Light Company [Member] | Electric Distribution [Member] | Merger Integration Costs [Member]
Amount of Impairment to Carrying Amount of Regulatory Assets	us-gaap_AmountOfImpairmentToCarryingAmountOfRegulatoryAssets	$ 1,000,000
Exelon Generation Co L L C [Member]
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared	us-gaap_DistributionMadeToLimitedLiabilityCompanyLLCMemberCashDistributionsDeclared	$ 164,000,000