Exelon Generation 10-Q 2 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	6 Months Ended
	Jun. 30, 2017shares
Entity Registrant Name	EXELON CORP
Entity Central Index Key	1,109,357
Document Type	10-Q
Document Period End Date	Jun. 30, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
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	960,087,898
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	127,017,160
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	3 Months Ended						6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017		Jun. 30, 2016
Operating revenues [Abstract]
Operating Revenue	$ 3,908		$ 3,234				$ 8,468		$ 7,708
Regulated Operating Revenue	3,715		3,676				7,913		6,777
Electric operating revenues	3,511	[1]	3,480	[1]			7,156	[2]	6,136	[2]
Natural gas operating revenues	204	[1]	197	[1]			757	[2]	641	[2]
Operating revenues from affiliates	0	[3]	1	[3]			0	[4]	2	[4]
Revenues	7,623		6,910				16,381		14,485
Operating expenses
Competitive businesses purchased power and fuel	2,158		1,576				4,952		4,016
Cost of Purchased Power	928		878				2,033		1,692
Operating and maintenance	2,971		2,505				5,431		5,341
Depreciation and amortization	915		941				1,811		1,626
Taxes other than income	420		394				857		720
Total operating expenses	7,392		6,294				15,084		13,395
Gain (Loss) on Disposition of Other Assets	1		31				5		40
Bargain purchase gain	0		0				226		0
Operating income	232		647				1,528		1,130
Other income and (deductions)
Interest expense, net	(426)		(366)				(789)		(643)
Interest expense to affiliates	(10)		(10)				(20)		(20)
Other, net	205		144				488		258
Total other income and (deductions)	(231)		(232)				(321)		(405)
Income before income taxes	1		415				1,207		725
Income taxes	(72)		102				143		285
Equity in losses of unconsolidated affiliates	(9)		(7)				(18)		(10)
Net income	64		306				1,046		430
Net (loss) income attributable to noncontrolling interests and preference stock dividends	(16)		39				(30)		(10)
Net income attributable to common shareholders	80		267				1,076		440
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost	(14)		(12)				(28)		(23)
Actuarial loss reclassified to periodic benefit cost	49		46				98		93
Pension and non-pension postretirement benefit plan valuation adjustment	(2)		(1)				(58)		(3)
Unrealized (loss) gain on cash flow hedges	1		0				(5)		7
Other Comprehensive Income Unrealized Income Loss On Equity Investments Arising During Period Net Of Tax	0		(4)				3		(7)
Unrealized gain on foreign currency translation	2		0				3		6
Unrealized gain on marketable securities	1		2				2		0
Other comprehensive income	35		31				25		59
Comprehensive income	99		337				1,071		489
Comprehensive (loss) income attributable to noncontrolling interests and preference stock dividends	(16)		39				(32)		(10)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 115		$ 298				$ 1,103		$ 499
Average shares of common stock outstanding:
Weighted average common shares outstanding — basic	934		924				931		923
Weighted average common shares outstanding — diluted	936		926				932		926
Earnings per average common share:
Basic	$ 0.09		$ 0.29				$ 1.16		$ 0.48
Diluted	0.09		0.29				1.15		0.48
Dividends declared per common share	$ 0.33		$ 0.32				$ 0.66		$ 0.63
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating Revenue	$ 3,906		$ 3,231				$ 8,463		$ 7,702
Operating revenues from affiliates	268		358				598		627
Revenues	4,174		3,589				9,061		8,329
Operating expenses
Cost of Purchased Power	2,156		1,575				4,952		4,015
Purchased power from affiliate	1		2				3		5
Operating and maintenance	1,824		1,369				3,132		2,665
Operating and maintenance from affiliates	186		161				365		332
Depreciation and amortization	334		408				637		697
Taxes other than income	140		118				282		244
Total operating expenses	4,641		3,633				9,371		7,958
Gain (Loss) on Disposition of Other Assets	0		31				4		31
Bargain purchase gain	0		0				226		0
Operating income	(467)		(13)				(80)		402
Other income and (deductions)
Interest expense, net	(120)		(89)				(209)		(176)
Interest expense to affiliates	(9)		(10)				(19)		(20)
Other, net	181		117				440		210
Total other income and (deductions)	52		18				212		14
Income before income taxes	(415)		5				132		416
Income taxes	(158)		(31)				(31)		120
Equity in losses of unconsolidated affiliates	(9)		(8)				(19)		(11)
Net income	(266)		28				144		285
Net (loss) income attributable to noncontrolling interests	(16)		36				(30)		(17)
Net (loss) income attributable to membership interest	(250)		(8)				174		302
Other comprehensive income (loss), net of income taxes
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	0		1				0		0
Unrealized (loss) gain on cash flow hedges	1		(1)				(5)		4
Other Comprehensive Income Unrealized Income Loss On Equity Investments Arising During Period Net Of Tax	0		(2)				4		(4)
Unrealized gain on foreign currency translation	2		0				3		6
Other comprehensive income	1		0				12		(2)
Comprehensive income	(265)		28				156		283
Comprehensive (loss) income attributable to noncontrolling interests and preference stock dividends	(16)		36				(32)		(17)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	(249)		(8)				188		300
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Electric operating revenues	1,354		1,283				2,647		2,527
Operating revenues from affiliates	3		3				9		8
Revenues	1,357		1,286				2,656		2,535
Operating expenses
Purchased power	360		326				689		668
Purchased power from affiliate	18		13				24		18
Operating and maintenance	312		318				620		623
Operating and maintenance from affiliates	65		50				127		113
Depreciation and amortization	211		190				419		379
Taxes other than income	72		65				144		141
Total operating expenses	1,038		962				2,023		1,942
Gain (Loss) on Disposition of Other Assets	0		0				0		5
Operating income	319		324				633		598
Other income and (deductions)
Interest expense, net	(98)		(88)				(179)		(170)
Interest expense to affiliates	(3)		(3)				(6)		(7)
Other, net	4		3				8		7
Total other income and (deductions)	(97)		(88)				(177)		(170)
Income before income taxes	222		236				456		428
Income taxes	104		91				197		168
Net income	118		145				259		260
Other comprehensive income (loss), net of income taxes
Comprehensive income	118		145				259		260
PECO Energy Co [Member]
Operating revenues [Abstract]
Electric operating revenues	548		585				1,138		1,228
Natural gas operating revenues	80		77				285		273
Operating revenues from affiliates	2		2				3		4
Revenues	630		664				1,426		1,505
Operating expenses
Purchased power	136		130				292		295
Purchased fuel	27		23				113		100
Purchased power from affiliate	34		64				79		142
Operating and maintenance	153		157				326		333
Operating and maintenance from affiliates	37		33				72		72
Depreciation and amortization	71		67				141		134
Taxes other than income	35		38				74		80
Total operating expenses	493		512				1,097		1,156
Operating income	137		152				329		349
Other income and (deductions)
Interest expense, net	(28)		(28)				(56)		(56)
Interest expense to affiliates	(3)		(3)				(6)		(6)
Other, net	2		2				3		4
Total other income and (deductions)	(29)		(29)				(59)		(58)
Income before income taxes	108		123				270		291
Income taxes	20		23				55		67
Net income	88		100				215		224
Other comprehensive income (loss), net of income taxes
Comprehensive income	88		100				215		224
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues	569		582				1,234		1,260
Natural gas operating revenues	102		94				383		340
Operating revenues from affiliates	3		4				8		9
Revenues	674		680				1,625		1,609
Operating expenses
Purchased power	115		108				248		235
Purchased fuel	22		20				105		95
Purchased power from affiliate	97		133				231		304
Operating and maintenance	135		177				284		345
Operating and maintenance from affiliates	39		31				73		65
Depreciation and amortization	112		97				239		206
Taxes other than income	56		55				119		114
Total operating expenses	576		621				1,299		1,364
Operating income	98		59				326		245
Other income and (deductions)
Interest expense, net	(22)		(20)				(46)		(40)
Interest expense to affiliates	(4)		(4)				(8)		(8)
Other, net	4		5				8		11
Total other income and (deductions)	(22)		(19)				(46)		(37)
Income before income taxes	76		40				280		208
Income taxes	31		6				111		73
Net income	45		34				169		135
Preference stock dividends	0		3				0		6
Net income attributable to common shareholders	45		31				169		129
Other comprehensive income (loss), net of income taxes
Comprehensive income	45		34				169		135
Comprehensive (loss) income attributable to noncontrolling interests and preference stock dividends	0		3				0		6
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	45		31				169		129
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						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 income						1
Comprehensive income						$ 20
Pepco Holdings LLC [Member] | Successor [Member]
Operating revenues [Abstract]
Electric operating revenues	1,040		1,030		$ 1,120		2,138
Natural gas operating revenues	22		26		28		87
Operating revenues from affiliates	12		10		23		23
Revenues	1,074		1,066		1,171		2,248
Operating expenses
Purchased power	259		263		288		547
Purchased fuel	9		9		11		39
Purchased power from affiliate	115		144		155		259
Operating and maintenance	231		223		670		454
Operating and maintenance from affiliates	38		23		25		70
Depreciation and amortization	165		160		174		332
Taxes other than income	110		108		123		221
Total operating expenses	927		930		1,446		1,922
Gain (Loss) on Disposition of Other Assets	1						1
Operating income	148		136		(275)		327
Other income and (deductions)
Interest expense, net	(59)		(66)		(71)		(122)
Other, net	13		11		12		26
Total other income and (deductions)	(46)		(55)		(59)		(96)
Income before income taxes	102		81		(334)		231
Income taxes	36		29		(77)		26
Net income	66		52		(257)		205
Other comprehensive income (loss), net of income taxes
Actuarial loss reclassified to periodic benefit cost	0		0		0		0
Other comprehensive income	0		0		0		0
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	66		52		$ (257)		205
Potomac Electric Power Company [Member]
Operating revenues [Abstract]
Electric operating revenues	513		508				1,042		1,058
Operating revenues from affiliates	1		1				3		3
Revenues	514		509				1,045		1,061
Operating expenses
Purchased power	74		64				157		256
Purchased power from affiliate	69		88				152		95
Operating and maintenance	106		100				208		389
Operating and maintenance from affiliates	14		9				26		10
Depreciation and amortization	78		70				160		144
Taxes other than income	90		89				180		182
Total operating expenses	431		420				883		1,076
Gain (Loss) on Disposition of Other Assets	1		8				1		8
Operating income	84		97				163		(7)
Other income and (deductions)
Interest expense, net	(28)		(31)				(58)		(68)
Other, net	7		6				15		14
Total other income and (deductions)	(21)		(25)				(43)		(54)
Income before income taxes	63		72				120		(61)
Income taxes	20		23				19		(1)
Net income	43		49				101		(60)
Other comprehensive income (loss), net of income taxes
Comprehensive income	43		49				101		(60)
Delmarva Power and Light Company [Member]
Operating revenues [Abstract]
Electric operating revenues	258		253				553		554
Natural gas operating revenues	22		26				87		85
Operating revenues from affiliates	2		2				4		4
Revenues	282		281				644		643
Operating expenses
Purchased power	64		70				141		216
Purchased fuel	9		9				38		35
Purchased power from affiliate	40		43				91		47
Operating and maintenance	66		73				133		277
Operating and maintenance from affiliates	8		5				15		6
Depreciation and amortization	40		38				79		76
Taxes other than income	14		13				28		28
Total operating expenses	241		251				525		685
Operating income	41		30				119		(42)
Other income and (deductions)
Interest expense, net	(13)		(13)				(25)		(25)
Other, net	3		3				6		6
Total other income and (deductions)	(10)		(10)				(19)		(19)
Income before income taxes	31		20				100		(61)
Income taxes	12		8				24		(1)
Net income	19		12				76		(60)
Other comprehensive income (loss), net of income taxes
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	19		12				76		(60)
Atlantic City Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues	269		269				543		559
Operating revenues from affiliates	1		1				1		2
Revenues	270		270				544		561
Operating expenses
Purchased power	121		129				250		285
Purchased power from affiliate	7		12				16		13
Operating and maintenance	71		63				139		275
Operating and maintenance from affiliates	7		5				13		5
Depreciation and amortization	37		41				72		81
Taxes other than income	2		2				4		4
Total operating expenses	245		252				494		663
Gain (Loss) on Disposition of Other Assets	0		1				0		1
Operating income	25		19				50		(101)
Other income and (deductions)
Interest expense, net	(15)		(16)				(30)		(32)
Other, net	2		2				4		5
Total other income and (deductions)	(13)		(14)				(26)		(27)
Income before income taxes	12		5				24		(128)
Income taxes	4		2				(12)		(31)
Net income	8		3				36		(97)
Other comprehensive income (loss), net of income taxes
Comprehensive income							$ 36		$ (97)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 8		$ 3
[1]	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 June 30, 2017 and 2016.
[2]	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 six months ended June 30, 2017 and 2016.
[3]	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.
[4]	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.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities
Net income	$ 1,046	$ 430
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	2,591	2,396
Impairment of long-lived assets and losses on regulatory assets	445	239
Gain on sales of assets	(5)	(40)
Business Combination, Bargain Purchase, Gain Recognized, Amount	(226)	0
Deferred income taxes and amortization of investment tax credits	107	261
Unrealized Gain (Loss) on Derivatives	(230)	(194)
Gain (Loss) on Investments	(284)	(114)
Other non-cash operating activities	415	1,056
Changes in assets and liabilities:
Accounts receivable	342	86
Inventories	(23)	89
Accounts payable and accrued expenses	(811)	(363)
Option premiums paid, net	(8)	(10)
Collateral (posted) received, net	(173)	710
Income taxes	58	470
Pension and non-pension postretirement benefit contributions	(325)	(258)
Other assets and liabilities	(481)	(593)
Net cash flows provided by (used in) operating activities	2,898	4,553
Cash flows from investing activities
Capital expenditures	(3,845)	(4,489)
Proceeds from Sale of Property Held-for-sale	211	45
Proceeds from nuclear decommissioning trust fund sales	5,213	4,977
Investment in nuclear decommissioning trust funds	(5,339)	(5,094)
Acquisition of businesses, net	(212)	(6,642)
Proceeds from termination of direct financing lease investment	0	360
Change in restricted cash	1	15
Other investing activities	(9)	(49)
Net cash flows provided by (used in) investing activities	(3,980)	(10,877)
Cash flows from financing activities
Changes in short-term borrowings	422	(798)
Proceeds from short-term borrowings with maturities greater than 90 days	576	194
Repayments of Short-term Debt, Maturing in More than Three Months	(510)	(315)
Issuance of long-term debt	981	3,174
Retirement of long-term debt	(1,049)	(217)
Dividends paid on common stock	(607)	(582)
Proceeds from Issuance of Common Stock	1,150
Proceeds from employee stock plans	43	17
Other financing activities	(23)	(4)
Net cash flows provided by (used in) financing activities	983	1,469
Increase (Decrease) in cash and cash equivalents	(99)	(4,855)
Cash and cash equivalents at beginning of period	635	6,502
Cash and cash equivalents at end of period	536	1,647
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	144	285
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	1,415	1,467
Impairment of long-lived assets and losses on regulatory assets	445	179
Gain on sales of assets	(4)	(31)
Business Combination, Bargain Purchase, Gain Recognized, Amount	(226)	0
Deferred income taxes and amortization of investment tax credits	(173)	(59)
Unrealized Gain (Loss) on Derivatives	(235)	(199)
Gain (Loss) on Investments	(284)	(114)
Other non-cash operating activities	121	169
Changes in assets and liabilities:
Accounts receivable	192	123
Change Receivables Payables From Affiliates	8	(77)
Inventories	(5)	57
Accounts payable and accrued expenses	(328)	(228)
Option premiums paid, net	(8)	(10)
Collateral (posted) received, net	(163)	720
Income taxes	(99)	41
Pension and non-pension postretirement benefit contributions	(116)	(117)
Other assets and liabilities	(180)	(217)
Net cash flows provided by (used in) operating activities	974	2,387
Cash flows from investing activities
Capital expenditures	(1,189)	(2,051)
Proceeds from Sale of Property Held-for-sale	210	30
Proceeds from nuclear decommissioning trust fund sales	5,213	4,977
Investment in nuclear decommissioning trust funds	(5,339)	(5,094)
Acquisition of businesses, net	(212)	(1)
Change in restricted cash	(8)	25
Other investing activities	(32)	(96)
Net cash flows provided by (used in) investing activities	(1,357)	(2,210)
Cash flows from financing activities
Changes in short-term borrowings	(51)	0
Proceeds from Debt, Maturing in More than Three Months	76	194
Repayments of Debt, Maturing in More than Three Months	(10)	(15)
Issuance of long-term debt	779	173
Retirement of long-term debt	(295)	(131)
Distribution to member	(330)	(111)
Proceeds from Contributions from Affiliates	0	45
Change in Exelon intercompany money pool borrowings	196	(429)
Other financing activities	(7)	39
Net cash flows provided by (used in) financing activities	358	(235)
Increase (Decrease) in cash and cash equivalents	(25)	(58)
Cash and cash equivalents at beginning of period	290	431
Cash and cash equivalents at end of period	265	373
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	259	260
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	419	379
Deferred income taxes and amortization of investment tax credits	235	222
Other non-cash operating activities	58	83
Changes in assets and liabilities:
Accounts receivable	12	(36)
Change Receivables Payables From Affiliates	(4)	1
Inventories	(2)	7
Accounts payable and accrued expenses	(182)	(42)
Collateral (posted) received, net	(8)	(10)
Income taxes	4	261
Pension and non-pension postretirement benefit contributions	(37)	(35)
Other assets and liabilities	34	38
Net cash flows provided by (used in) operating activities	788	1,128
Cash flows from investing activities
Capital expenditures	(1,168)	(1,334)
Change in restricted cash	(10)	0
Other investing activities	12	21
Net cash flows provided by (used in) investing activities	(1,166)	(1,313)
Cash flows from financing activities
Changes in short-term borrowings	389	(259)
Issuance of long-term debt	0	1,200
Dividends paid on common stock	(211)	(183)
Contributions from parent	184	113
Other financing activities	(1)	(17)
Net cash flows provided by (used in) financing activities	361	854
Increase (Decrease) in cash and cash equivalents	(17)	669
Cash and cash equivalents at beginning of period	56	67
Cash and cash equivalents at end of period	39	736
PECO Energy Co [Member]
Cash flows from operating activities
Net income	215	224
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	141	134
Deferred income taxes and amortization of investment tax credits	39	51
Other non-cash operating activities	22	27
Changes in assets and liabilities:
Accounts receivable	26	(1)
Change Receivables Payables From Affiliates	(10)	(2)
Inventories	7	19
Accounts payable and accrued expenses	(30)	(19)
Income taxes	51	31
Pension and non-pension postretirement benefit contributions	(23)	(29)
Other assets and liabilities	(70)	(96)
Net cash flows provided by (used in) operating activities	368	339
Cash flows from investing activities
Capital expenditures	(367)	(299)
Changes in Exelon intercompany money pool	121	0
Other investing activities	4	8
Net cash flows provided by (used in) investing activities	(242)	(291)
Cash flows from financing activities
Dividends paid on common stock	(144)	(139)
Other financing activities	0	(1)
Net cash flows provided by (used in) financing activities	(144)	(140)
Increase (Decrease) in cash and cash equivalents	(18)	(92)
Cash and cash equivalents at beginning of period	63	295
Cash and cash equivalents at end of period	45	203
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	169	135
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	239	206
Impairment of long-lived assets and losses on regulatory assets	0	52
Deferred income taxes and amortization of investment tax credits	99	17
Other non-cash operating activities	35	60
Changes in assets and liabilities:
Accounts receivable	77	11
Change Receivables Payables From Affiliates	(7)	6
Inventories	(5)	6
Accounts payable and accrued expenses	(83)	(5)
Income taxes	26	46
Pension and non-pension postretirement benefit contributions	(47)	(42)
Other assets and liabilities	(31)	(3)
Net cash flows provided by (used in) operating activities	472	489
Cash flows from investing activities
Capital expenditures	(405)	(392)
Change in restricted cash	18	5
Other investing activities	4	12
Net cash flows provided by (used in) investing activities	(383)	(375)
Cash flows from financing activities
Changes in short-term borrowings	40	(2)
Retirement of long-term debt	(41)	(39)
Dividends paid on common stock	(99)	(90)
Dividends paid on preference stock	0	(6)
Contributions from parent	0	21
Other financing activities	0	(2)
Net cash flows provided by (used in) financing activities	(100)	(118)
Increase (Decrease) in cash and cash equivalents	(11)	(4)
Cash and cash equivalents at beginning of period	23	9
Cash and cash equivalents at end of period	12	5
Pepco Holdings LLC [Member] | Successor [Member]
Cash flows from operating activities
Net income	205
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	332
Gain (Loss) on Disposition of Assets	(1)
Deferred income taxes and amortization of investment tax credits	59
Unrealized Gain (Loss) on Derivatives	0
Other non-cash operating activities	28
Changes in assets and liabilities:
Accounts receivable	(3)
Change Receivables Payables From Affiliates	(7)
Inventories	(19)
Accounts payable and accrued expenses	(61)
Income taxes	87
Pension and non-pension postretirement benefit contributions	(68)
Other assets and liabilities	(149)
Net cash flows provided by (used in) operating activities	403
Cash flows from investing activities
Capital expenditures	(671)
Proceeds from Sale of Property Held-for-sale	1
Purchases of investments	0
Change in restricted cash	3
Other investing activities	0
Net cash flows provided by (used in) investing activities	(667)
Cash flows from financing activities
Changes in short-term borrowings	45
Proceeds from short-term borrowings with maturities greater than 90 days	0
Repayments of Debt, Maturing in More than Three Months	(500)
Issuance of long-term debt	202
Retirement of long-term debt	(120)
Common stock issued for the Direct Stock Purchase and Dividend Reinvestment Plan and employee-related compensation	0
Distribution to member	(131)
Contributions from parent	751
Change in Exelon intercompany money pool borrowings	0
Other financing activities	(2)
Net cash flows provided by (used in) financing activities	245
Increase (Decrease) in cash and cash equivalents	(19)
Cash and cash equivalents at beginning of period	170
Cash and cash equivalents at end of period	151	294
Pepco Holdings LLC [Member] | Predecessor [Member]
Cash flows from financing activities
Cash and cash equivalents at beginning of period		26
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income	101	(60)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	160	144
Gain (Loss) on Disposition of Assets	(1)	0
Deferred income taxes and amortization of investment tax credits	35	20
Other non-cash operating activities	0	158
Changes in assets and liabilities:
Accounts receivable	(33)	(41)
Change Receivables Payables From Affiliates	(4)	47
Inventories	(10)	1
Accounts payable and accrued expenses	(45)	(19)
Income taxes	46	165
Pension and non-pension postretirement benefit contributions	(65)	(3)
Other assets and liabilities	(55)	(47)
Net cash flows provided by (used in) operating activities	129	365
Cash flows from investing activities
Capital expenditures	(291)	(256)
Proceeds from Sale of Property Held-for-sale	1	12
Acquisition of businesses, net		(33)
Purchases of investments	0	(31)
Change in restricted cash	(1)	(31)
Other investing activities	(2)	(1)
Net cash flows provided by (used in) investing activities	(293)	(307)
Cash flows from financing activities
Changes in short-term borrowings	(23)	(64)
Issuance of long-term debt	202	1
Retirement of long-term debt	(7)	(5)
Dividends paid on common stock	(58)	(55)
Contributions from parent	161	187
Other financing activities	(1)	0
Net cash flows provided by (used in) financing activities	274	64
Increase (Decrease) in cash and cash equivalents	110	122
Cash and cash equivalents at beginning of period	9	5
Cash and cash equivalents at end of period	119	127
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	76	(60)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	79	76
Deferred income taxes and amortization of investment tax credits	33	23
Other non-cash operating activities	(3)	121
Changes in assets and liabilities:
Accounts receivable	12	30
Change Receivables Payables From Affiliates	(2)	15
Inventories	(3)	1
Accounts payable and accrued expenses	18	(2)
Collateral (posted) received, net	0	1
Income taxes	13	66
Other assets and liabilities	(29)	(51)
Net cash flows provided by (used in) operating activities	194	220
Cash flows from investing activities
Capital expenditures	(192)	(182)
Change in restricted cash	0	(1)
Other investing activities	1	3
Net cash flows provided by (used in) investing activities	(191)	(180)
Cash flows from financing activities
Changes in short-term borrowings	25	(105)
Retirement of long-term debt	(14)	0
Dividends paid on common stock	(54)	(38)
Contributions from parent	0	113
Net cash flows provided by (used in) financing activities	(43)	(30)
Increase (Decrease) in cash and cash equivalents	(40)	10
Cash and cash equivalents at beginning of period	46	5
Cash and cash equivalents at end of period	6	15
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	36	(97)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	72	81
Deferred income taxes and amortization of investment tax credits	(8)	(28)
Other non-cash operating activities	7	138
Changes in assets and liabilities:
Accounts receivable	18	31
Change Receivables Payables From Affiliates	(6)	8
Inventories	(3)	(2)
Accounts payable and accrued expenses	3	6
Income taxes	11	181
Other assets and liabilities	(53)	(110)
Net cash flows provided by (used in) operating activities	77	208
Cash flows from investing activities
Capital expenditures	(175)	(164)
Proceeds from Sale of Property Held-for-sale	0	2
Change in restricted cash	2	1
Other investing activities	0	1
Net cash flows provided by (used in) investing activities	(173)	(160)
Cash flows from financing activities
Changes in short-term borrowings	42	(5)
Retirement of long-term debt	(17)	(22)
Dividends paid on common stock	(22)	(11)
Contributions from parent	0	139
Other financing activities	(1)	(1)
Net cash flows provided by (used in) financing activities	2	100
Increase (Decrease) in cash and cash equivalents	(94)	148
Cash and cash equivalents at beginning of period	101	3
Cash and cash equivalents at end of period	$ 7	$ 151

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Assets, Current [Abstract]
Cash and cash equivalents		$ 536	$ 635
Restricted cash and cash equivalents		252	253
Accounts receivable, net
Customer		3,825	4,158
Other		958	1,201
Mark-to-market derivative assets		833	917
Unamortized energy contract assets		84	88
Inventories, net
Fossil fuel and emission allowances		334	364
Materials and supplies		1,267	1,274
Prepaid Taxes		1,250	1,250
Regulatory assets		1,293	1,342
Other		1,600	930
Total current assets		12,232	12,412
Property, plant and equipment, net		72,748	71,555
Deferred debits and other assets
Regulatory assets		9,945	10,046
Nuclear decommissioning trust funds		12,641	11,061
Investments		638	629
Goodwill		6,677	6,677
Mark-to-market derivative assets		464	492
Pledged assets for Zion Station decommissioning		75	113
Unamortized energy contract assets		419	447
Other		1,265	1,472
Total deferred debits and other assets		32,124	30,937
Total assets		117,104	114,904
Liabilities, Current [Abstract]
Short-term borrowings		1,757	1,267
Long-term debt due within one year		3,619	2,430
Accounts payable		3,134	3,441
Accrued expenses		2,878	3,460
Payables to affiliates		8	8
Unamortized energy contract liabilities		340	407
Regulatory liabilities		574	602
Mark-to-market derivative liabilities (current liabilities)		244	282
Energy Marketing Accounts Payable		308	428
Accounts Payable and Accrued Liabilities, Current		126	151
Other		977	981
Total current liabilities		13,965	13,457
Long-term debt		30,315	31,575
Long-term debt to financing trusts		641	641
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		18,521	18,138
Asset Retirement Obligations, Noncurrent		9,848	9,111
Pension obligations		4,082	4,248
Non-pension postretirement benefit obligations		1,955	1,848
Spent nuclear fuel obligation		1,139	1,024
Regulatory liabilities		4,398	4,187
Mark-to-market derivative liabilities (noncurrent liabilities)		417	392
Unamortized energy contract liabilities		705	830
Payable for Zion Station decommissioning		0	14
Other		1,828	1,827
Total deferred credits and other liabilities		42,893	41,619
Total liabilities	[1]	87,814	87,292
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		18,860	18,794
Treasury stock, at cost (2 shares and 35 shares at June 30, 2017 and December 31, 2016, respectively)		(123)	(2,327)
Retained earnings		11,442	12,030
Accumulated other comprehensive loss, net		(2,633)	(2,660)
Total shareholders’ equity		27,546	25,837
Member’s equity
Noncontrolling interests		1,744	1,775
Total equity		29,290	27,612
Total liabilities and shareholders’ equity		117,104	114,904
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	[2]	293	502
Variable Interest Entity, Primary Beneficiary [Member]
Assets, Current [Abstract]
Cash and cash equivalents	[3],[4]	68	150
Restricted cash and cash equivalents	[3],[4]	55	59
Accounts receivable, net
Customer	[3],[4]	106	371
Other	[3],[4]	24	48
Mark-to-market derivative assets	[3],[4]	0	31
Inventories, net
Materials and supplies	[3],[4]	193	199
Other	[3],[4]	38	50
Total current assets	[3],[4]	484	908
Property, plant and equipment, net	[3],[4]	5,293	5,415
Deferred debits and other assets
Nuclear decommissioning trust funds	[3],[4]	2,341	2,185
Goodwill	[3],[4]	0	47
Mark-to-market derivative assets	[3],[4]	0	23
Other	[3],[4]	267	315
Total assets	[3],[4]	8,385	8,893
Liabilities, Current [Abstract]
Long-term debt due within one year	[3],[4]	191	181
Accounts payable	[3],[4]	80	269
Accrued expenses	[3],[4]	48	119
Unamortized energy contract liabilities	[3],[4]	16	15
Mark-to-market derivative liabilities (current liabilities)	[3],[4]	0	60
Other	[3],[4]	5	30
Total current liabilities	[3],[4]	340	674
Long-term debt	[3],[4]	616	641
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent	[3],[4]	1,954	1,904
Pension obligations	[3],[4],[5]	0	9
Unamortized energy contract liabilities	[3],[4]	13	22
Other	[3],[4]	98	106
Total liabilities	[3],[4]	3,021	3,356
Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		8,385	8,893
Deferred credits and other liabilities
Total liabilities		3,021	3,356
Exelon Generation Co L L C [Member]
Assets, Current [Abstract]
Cash and cash equivalents		265	290
Restricted cash and cash equivalents		166	158
Accounts receivable, net
Customer		2,242	2,433
Other		447	558
Mark-to-market derivative assets		833	917
Receivables from affiliates		143	156
Unamortized energy contract assets		84	88
Inventories, net
Fossil fuel and emission allowances		272	292
Materials and supplies		901	935
Other		1,241	701
Total current assets		6,594	6,528
Property, plant and equipment, net		25,261	25,585
Deferred debits and other assets
Nuclear decommissioning trust funds		12,641	11,061
Investments		426	418
Goodwill		47	47
Mark-to-market derivative assets		453	476
Prepaid pension asset		1,590	1,595
Pledged assets for Zion Station decommissioning		75	113
Unamortized energy contract assets		418	447
Deferred Tax Assets, Net, Noncurrent		5	16
Other		620	688
Total deferred debits and other assets		16,275	14,861
Total assets		48,130	46,974
Liabilities, Current [Abstract]
Short-term borrowings		716	699
Long-term debt due within one year		1,828	1,117
Accounts payable		1,527	1,610
Accrued expenses		722	989
Payables to affiliates		132	137
Unamortized energy contract liabilities		61	72
Other Short-term Borrowings		251	55
Mark-to-market derivative liabilities (current liabilities)		225	263
Energy Marketing Accounts Payable		308	428
Other		294	313
Total current liabilities		6,064	5,683
Long-term debt		7,010	7,202
Long-term debt to affiliate		916	922
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		5,578	5,585
Asset Retirement Obligations, Noncurrent		9,655	8,922
Non-pension postretirement benefit obligations		922	930
Spent nuclear fuel obligation		1,139	1,024
Due to Affiliate, Noncurrent		2,871	2,608
Mark-to-market derivative liabilities (noncurrent liabilities)		180	153
Unamortized energy contract liabilities		67	80
Payable for Zion Station decommissioning		0	14
Other		598	595
Total deferred credits and other liabilities		21,010	19,911
Total liabilities	[6]	35,000	33,718
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Retained earnings		2,119	2,275
Accumulated other comprehensive loss, net		(40)	(54)
Member’s equity
Members' Capital		9,308	9,261
Total member's equity		11,387	11,482
Noncontrolling interests		1,743	1,774
Total equity		13,130	13,256
Total liabilities and shareholders’ equity		48,130	46,974
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets, Current [Abstract]
Cash and cash equivalents		68	150
Restricted cash and cash equivalents		48	27
Accounts receivable, net
Customer		106	371
Other		24	48
Mark-to-market derivative assets		0	31
Inventories, net
Materials and supplies		193	199
Other		34	44
Total current assets		473	870
Property, plant and equipment, net		5,293	5,415
Deferred debits and other assets
Nuclear decommissioning trust funds		2,341	2,185
Goodwill		0	47
Mark-to-market derivative assets		0	23
Other		235	277
Total assets		8,342	8,817
Liabilities, Current [Abstract]
Long-term debt due within one year		154	99
Accounts payable		80	269
Accrued expenses		47	116
Unamortized energy contract liabilities		16	15
Mark-to-market derivative liabilities (current liabilities)		0	60
Other		5	30
Total current liabilities		302	589
Long-term debt		533	540
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent		1,954	1,904
Pension obligations	[5]	0	9
Unamortized energy contract liabilities		13	22
Other		98	106
Total liabilities		2,900	3,170
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		8,342	8,817
Deferred credits and other liabilities
Total liabilities		2,900	3,170
Commonwealth Edison Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		39	56
Restricted cash and cash equivalents		12	2
Accounts receivable, net
Customer		529	528
Other		211	218
Receivables from affiliates		386	356
Inventories, net
Inventories, net		160	159
Regulatory assets		182	190
Other		57	45
Total current assets		1,576	1,554
Property, plant and equipment, net		20,019	19,335
Deferred debits and other assets
Regulatory assets		1,050	977
Investments		6	6
Goodwill		2,625	2,625
Receivable from affiliate		2,364	2,170
Prepaid pension asset		1,283	1,343
Other		237	325
Total deferred debits and other assets		7,565	7,446
Total assets		29,160	28,335
Liabilities, Current [Abstract]
Short-term borrowings		389	0
Long-term debt due within one year		1,125	425
Accounts payable		547	645
Accrued expenses		1,107	1,250
Payables to affiliates		67	65
Customer deposits		115	121
Regulatory liabilities		269	329
Mark-to-market derivative liabilities (current liabilities)		19	19
Other		112	84
Total current liabilities		3,750	2,938
Long-term debt		5,911	6,608
Long-term debt to financing trusts		205	205
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		5,600	5,364
Asset Retirement Obligations, Noncurrent		122	119
Non-pension postretirement benefit obligations		229	239
Regulatory liabilities		3,585	3,369
Mark-to-market derivative liabilities (noncurrent liabilities)		237	239
Other		541	529
Total deferred credits and other liabilities		10,314	9,859
Total liabilities		20,180	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		6,357	6,150
Retained Earnings, Appropriated		2,674	2,626
Total shareholders’ equity		8,980	8,725
Member’s equity
Total liabilities and shareholders’ equity		29,160	28,335
PECO Energy Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		45	63
Restricted cash and cash equivalents		4	4
Accounts receivable, net
Customer		258	306
Other		135	131
Receivables from affiliates		1	4
Receivable from Exelon intercompany pool		10	131
Inventories, net
Fossil fuel and emission allowances		25	35
Materials and supplies		30	27
Prepaid Taxes		77	9
Regulatory assets		46	29
Other		25	18
Total current assets		656	757
Property, plant and equipment, net		7,758	7,565
Deferred debits and other assets
Regulatory assets		1,732	1,681
Investments		24	25
Receivable from affiliate		506	438
Prepaid pension asset		354	345
Other		11	20
Total deferred debits and other assets		2,627	2,509
Total assets		11,041	10,831
Liabilities, Current [Abstract]
Long-term debt due within one year		500	0
Accounts payable		278	342
Accrued expenses		136	104
Payables to affiliates		50	63
Customer deposits		63	61
Regulatory liabilities		155	127
Other		31	30
Total current liabilities		1,213	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		3,128	3,006
Asset Retirement Obligations, Noncurrent		28	28
Non-pension postretirement benefit obligations		289	289
Regulatory liabilities		544	517
Other		89	85
Total deferred credits and other liabilities		4,078	3,925
Total liabilities		7,555	7,416
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		2,473	2,473
Retained earnings		1,012	941
Accumulated other comprehensive loss, net		1	1
Total shareholders’ equity		3,486	3,415
Member’s equity
Total liabilities and shareholders’ equity		11,041	10,831
Baltimore Gas and Electric Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		12	23
Restricted cash and cash equivalents		6	24
Accounts receivable, net
Customer		312	395
Other		75	102
Receivables from affiliates		1	0
Inventories, net
Fossil fuel and emission allowances		31	30
Materials and supplies		42	38
Prepaid Taxes		0	15
Regulatory assets		197	208
Other		4	7
Total current assets		680	842
Property, plant and equipment, net		7,283	7,040
Deferred debits and other assets
Regulatory assets		495	504
Investments		13	12
Prepaid pension asset		310	297
Other		5	9
Total deferred debits and other assets		823	822
Total assets	[7]	8,786	8,704
Liabilities, Current [Abstract]
Short-term borrowings		85	45
Long-term debt due within one year		0	41
Accounts payable		205	205
Accrued expenses		100	175
Payables to affiliates		49	55
Customer deposits		113	110
Regulatory liabilities		67	50
Other		21	26
Total current liabilities		640	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		2,322	2,219
Asset Retirement Obligations, Noncurrent		22	21
Non-pension postretirement benefit obligations		201	205
Regulatory liabilities		90	110
Other		59	61
Total deferred credits and other liabilities		2,694	2,616
Total liabilities	[7]	5,868	5,856
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		1,421	1,421
Retained earnings		1,497	1,427
Total shareholders’ equity		2,918	2,848
Member’s equity
Total liabilities and shareholders’ equity		8,786	8,704
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets, Current [Abstract]
Cash and cash equivalents			0
Restricted cash and cash equivalents			23
Accounts receivable, net
Customer			0
Other			0
Mark-to-market derivative assets			0
Inventories, net
Materials and supplies			0
Other			0
Total current assets			23
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			3
Total assets			26
Liabilities, Current [Abstract]
Long-term debt due within one year			41
Accounts payable			0
Accrued expenses			1
Unamortized energy contract liabilities			0
Mark-to-market derivative liabilities (current liabilities)			0
Other			0
Total current liabilities			42
Long-term debt			0
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent			0
Pension obligations	[5]		0
Unamortized energy contract liabilities			0
Other			0
Total liabilities			42
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets			26
Deferred credits and other liabilities
Total liabilities			42
Pepco Holdings LLC [Member] | Successor [Member]
Assets, Current [Abstract]
Cash and cash equivalents		151	170
Restricted cash and cash equivalents		40	43
Accounts receivable, net
Customer		484	496
Other		199	283
Mark-to-market derivative assets		0	0
Receivables from affiliates		1	0
Inventories, net
Fossil fuel and emission allowances		6	6
Materials and supplies		134	116
Regulatory assets		605	653
Other		86	71
Total current assets		1,706	1,838
Property, plant and equipment, net		12,014	11,598
Deferred debits and other assets
Regulatory assets		2,715	2,851
Investments		132	133
Goodwill		4,005	4,005
Notes, Loans and Financing Receivable, Gross, Noncurrent		4	4
Mark-to-market derivative assets		0	0
Prepaid pension asset		529	509
Deferred Tax Assets, Net, Noncurrent		6	6
Other		79	81
Total deferred debits and other assets		7,470	7,589
Total assets	[8]	21,190	21,025
Liabilities, Current [Abstract]
Short-term borrowings		67	522
Long-term debt due within one year		160	253
Accounts payable		415	458
Accrued expenses		259	272
Payables to affiliates		86	94
Unamortized energy contract liabilities		279	335
Customer deposits		119	123
Regulatory liabilities		68	79
Mark-to-market derivative liabilities (current liabilities)		0	0
Payables to Customers		73	101
Other		36	47
Total current liabilities		1,562	2,284
Long-term debt		5,792	5,645
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		3,844	3,775
Asset Retirement Obligations, Noncurrent		14	14
Non-pension postretirement benefit obligations		135	134
Regulatory liabilities		151	158
Mark-to-market derivative liabilities (noncurrent liabilities)		0	0
Unamortized energy contract liabilities		638	750
Other		213	249
Total deferred credits and other liabilities		4,995	5,080
Total liabilities		12,349	13,009
Stockholders' Equity Attributable to Parent [Abstract]
Retained earnings		13	(61)
Member’s equity
Members' Capital		8,828	8,077
Total member's equity		8,841	8,016
Total equity		8,841	8,016
Total liabilities and shareholders’ equity	[8]	21,190	21,025
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Assets, Current [Abstract]
Cash and cash equivalents	[3]	0	0
Restricted cash and cash equivalents	[3]	7	9
Accounts receivable, net
Customer	[3]	0	0
Other	[3]	0	0
Mark-to-market derivative assets	[3]	0	0
Inventories, net
Materials and supplies	[3]	0	0
Other	[3]	4	5
Total current assets	[3]	11	14
Property, plant and equipment, net	[3]	0	0
Deferred debits and other assets
Nuclear decommissioning trust funds	[3]	0	0
Goodwill	[3]	0	0
Mark-to-market derivative assets	[3]	0	0
Other	[3]	32	35
Total assets	[3]	43	49
Liabilities, Current [Abstract]
Long-term debt due within one year	[3]	37	40
Accounts payable	[3]	0	0
Accrued expenses	[3]	1	2
Unamortized energy contract liabilities	[3]	0	0
Mark-to-market derivative liabilities (current liabilities)	[3]	0	0
Other	[3]	0	0
Total current liabilities	[3]	38	42
Long-term debt	[3]	83	101
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent	[3]	0	0
Pension obligations	[3],[5]	0	0
Unamortized energy contract liabilities	[3]	0	0
Other	[3]	0	0
Total liabilities	[3]	121	143
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member] | Successor [Member]
Deferred debits and other assets
Total assets		43	49
Deferred credits and other liabilities
Total liabilities		121	143
Potomac Electric Power Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		119	9
Restricted cash and cash equivalents		34	33
Accounts receivable, net
Customer		256	235
Other		114	150
Inventories, net
Materials and supplies		73	63
Regulatory assets		165	162
Other		7	32
Total current assets		768	684
Property, plant and equipment, net		5,759	5,571
Deferred debits and other assets
Regulatory assets		682	690
Investments		102	102
Prepaid pension asset		332	282
Other		5	6
Total deferred debits and other assets		1,121	1,080
Total assets		7,648	7,335
Liabilities, Current [Abstract]
Short-term borrowings		0	23
Long-term debt due within one year		18	16
Accounts payable		157	209
Accrued expenses		117	113
Payables to affiliates		70	74
Customer deposits		53	53
Regulatory liabilities		5	11
Payables to Customers		49	68
Other		16	29
Total current liabilities		485	596
Long-term debt		2,527	2,333
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		1,950	1,910
Non-pension postretirement benefit obligations		40	43
Regulatory liabilities		17	20
Other		125	133
Total deferred credits and other liabilities		2,132	2,106
Total liabilities		5,144	5,035
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		1,470	1,309
Other paid-in capital		1,034	991
Total shareholders’ equity		2,504	2,300
Member’s equity
Total liabilities and shareholders’ equity		7,648	7,335
Delmarva Power and Light Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		6	46
Accounts receivable, net
Customer		124	136
Other		49	63
Receivables from affiliates		0	3
Inventories, net
Fossil fuel and emission allowances		6	7
Materials and supplies		36	32
Regulatory assets		71	59
Other		19	24
Total current assets		311	370
Property, plant and equipment, net		3,412	3,273
Deferred debits and other assets
Regulatory assets		299	289
Goodwill		8	8
Prepaid pension asset		200	206
Other		5	7
Total deferred debits and other assets		512	510
Total assets		4,235	4,153
Liabilities, Current [Abstract]
Short-term borrowings		25	0
Long-term debt due within one year		109	119
Accounts payable		125	88
Accrued expenses		35	36
Payables to affiliates		33	38
Customer deposits		35	36
Regulatory liabilities		43	43
Payables to Customers		3	13
Other		9	8
Total current liabilities		417	381
Long-term debt		1,217	1,221
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		1,092	1,056
Non-pension postretirement benefit obligations		20	19
Regulatory liabilities		95	97
Other		46	53
Total deferred credits and other liabilities		1,253	1,225
Total liabilities		2,887	2,827
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		764	764
Retained earnings		584	562
Total shareholders’ equity		1,348	1,326
Member’s equity
Total liabilities and shareholders’ equity		4,235	4,153
Atlantic City Electric Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		7	101
Restricted cash and cash equivalents		7	9
Accounts receivable, net
Customer		103	125
Other		46	44
Inventories, net
Materials and supplies		25	22
Prepaid Taxes		37	0
Regulatory assets		89	96
Other		4	2
Total current assets		318	399
Property, plant and equipment, net		2,628	2,521
Deferred debits and other assets
Regulatory assets		406	405
Notes, Loans and Financing Receivable, Gross, Noncurrent		4	4
Prepaid pension asset		79	84
Other		43	44
Total deferred debits and other assets		532	537
Total assets	[9]	3,478	3,457
Liabilities, Current [Abstract]
Short-term borrowings		42	0
Long-term debt due within one year		33	35
Accounts payable		122	132
Accrued expenses		56	38
Payables to affiliates		23	29
Customer deposits		31	33
Regulatory liabilities		20	25
Payables to Customers		21	20
Other		8	8
Total current liabilities		356	320
Long-term debt		1,105	1,120
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		911	917
Non-pension postretirement benefit obligations		35	34
Regulatory liabilities		0	0
Other		23	32
Total deferred credits and other liabilities		969	983
Total liabilities		2,430	2,423
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		912	912
Retained earnings		136	122
Total shareholders’ equity		1,048	1,034
Member’s equity
Total liabilities and shareholders’ equity	[9]	3,478	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		74	89
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent		0	0
Pension obligations	[5]	0	0
Unamortized energy contract liabilities		0	0
Other		0	0
Total liabilities		108	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		$ 108	$ 126
[1]	Exelon’s consolidated assets include $8,385 million and $8,893 million at June 30, 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 $3,021 million and $3,356 million at June 30, 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 certain purchase accounting adjustments not pushed down to the ACE standalone entity.
[4]	Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity.
[5]	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.
[6]	Generation’s consolidated assets include $8,342 million and $8,817 million at June 30, 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 $2,900 million and $3,170 million at June 30, 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.
[7]	BGE’s consolidated assets include $26 million at December 31, 2016 of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $42 million at December 31, 2016 of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. BGE has no interests in any VIEs as of June 30, 2017. See Note 3 - Variable Interest Entities.
[8]	PHI’s consolidated total assets include $43 million and $49 million at June 30, 2017 and December 31, 2016, respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $121 million and $143 million at June 30, 2017 and December 31, 2016, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 3 - Variable Interest Entities.
[9]	ACE’s consolidated total assets include $30 million and $32 million at June 30, 2017 and December 31, 2016, respectively, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $108 million and $126 million at June 30, 2017 and December 31, 2016, respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 3 - Variable Interest Entities.

Consolidated Balance Sheets (U5

Consolidated Balance Sheets (Unaudited) (Parenthetical) - shares	Jun. 30, 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	960,087,898	922,872,373
Treasury Stock, Shares held	1,832,457	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
Beginning balance at Dec. 31, 2015	[1]					(2,624)						(63)											1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		$ 430							$ 285						$ 260					$ 224					$ 135						$ (60)			$ (60)			$ (97)
Other Comprehensive Income (Loss), Net of Tax		$ 59				59	[1]		(2)			(2)	[1]										0	[1]
Proceeds from Contributions from Parent															113										21						187			113			139
Ending balance at Jun. 30, 2016	[1]					(2,565)						(65)											1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Successor [Member]																												$ (257)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																												0
Proceeds from Contributions from Parent | Successor [Member]																												1,088
Ending balance at Jun. 30, 2016	[1]					(2,565)						(65)											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]																												205		205
Net income		1,046	0	0	1,076	0		(30)	144		174	0		(30)	259			259		215		215			169		169				101	0	101	76		76	36		36
Stock Issued During Period, Value, Treasury Stock Reissued		$ (1,150)		(2,204)	(1,054)
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid									49	49
Stock Issued During Period, Shares, Share-based Compensation, Gross		2,494
Stock Issued During Period, Value, Share-based Compensation, Gross		$ 23	23	0	0	0		0
Stock Issued During Period, Shares, Employee Stock Purchase Plans		648
Stock Issued During Period, Value, Employee Stock Purchase Plan		$ 43	43	0	0	0		0
Noncontrolling Interest, Period Increase (Decrease)		1	0	0	0	0		1
Noncontrolling Interest, Increase from Sale of Parent Equity Interest									1					1
Income Tax Effects Allocated Directly to Equity, Other									(2)	(2)
Common stock dividends		(610)	0	0	(610)	0		0												(144)	0	(144)	0		(99)		(99)				(58)	0	(58)	(54)		(54)	(22)		(22)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																												0
Other Comprehensive Income (Loss), Net of Tax		25	0	0	0	27	[1]	(2)	12		0	14	[1]	(2)									0	[1]
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared | Successor [Member]																												(131)		131
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared									(330)		(330)
Employee stock purchase plan issuances		$ 43	43	0	0	0		0
Dividends															(211)				(211)
Adjustments to Additional Paid in Capital, Other															184		184
Proceeds from Contributions from Parent | Successor [Member]																												751	751
Proceeds from Contributions from Parent															184										0						161	161		0			0
Ending Balance (in shares) at Jun. 30, 2017		961,920
Ending balance at Jun. 30, 2017		$ 29,290	$ 18,860	$ (123)	$ 11,442	$ (2,633)	[1]	$ 1,744				(40)	[1]										1	[1]
Ending Balance at Jun. 30, 2017		$ 27,546													8,980	$ 1,588	6,357	(1,639)	2,674	$ 3,486	$ 2,473	$ 1,012	$ 1		$ 2,918	$ 1,421	$ 1,497				$ 2,504	$ 1,470	$ 1,034	$ 1,348	$ 764	$ 584	$ 1,048	$ 912	$ 136
Ending Balance (Successor [Member]) at Jun. 30, 2017																												$ 8,841	$ 8,828	$ 13
Ending Balance at Jun. 30, 2017									$ 13,130	$ 9,308	$ 2,119	$ (40)		$ 1,743
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings, Appropriated															(2,674)			$ (259)	$ (259)
Other Additional Capital															$ 23		$ 23
[1]	All amounts are net of tax and noncontrolling interest. Amounts in parenthesis represent a decrease in AOCI.

Significant Accounting Policies

Significant Accounting Policies	6 Months Ended
	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation (Exelon, Generation, ComEd, PECO and BGE)	1 . Basis of Presentation (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 that identifiable 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 related to Exelon now also apply to PHI, Pepco, DPL and ACE, unless otherwise noted. Each of the Registrant’s Consolidated Financial Statements includes the accounts of its subsidiaries. All intercompany transactions have been eliminated. During preparation of the June 30, 2017 financial statements, errors were identified related to the Exelon, Generation, ComEd, PECO and BGE Consolidated Statements of Cash Flows for the three months ended March 31, 2017. These classification errors related to the presentation of changes in Account payable and accrued expenses and Accounts receivable within Cash flows provided by operating activities and Capital expenditures and Proceeds from sale of long-lived assets within Cash flows used in investing activities. These errors were corrected for the six months ended June 30, 2017, and will be revised within the first quarter 2018 Form 10-Q when the Consolidated Statements of Cash Flows for the three months ended March 31, 2017 will next be disclosed. As revised, the Cash flows provided by operating activities for the three months ended March 31, 2017 are $1,074 million , $ 420 million , $236 million , $106 million and $208 million for Exelon, Generation, ComEd, PECO and BGE, respectively, an increase (decrease) of $(127) million , $ (320) million , $ 91 million , $ 42 million and $ 40 million for Exelon, Generation, ComEd, PECO and BGE, respectively, from the originally reported amounts. As revised, the Cash flows used in investing activities are $ 2,284 million , $ 892 million , $ 620 million , $ 69 million and $ 221 million for Exelon, Generation, ComEd, PECO and BGE, respectively, an increase (decrease) of $ (127) million , $ (320) million , $ 91 million , $ 42 million and $ 40 million for Exelon, Generation, ComEd, PECO and BGE, respectively, from the originally reported amounts. Management has concluded that the errors are not material to the previously issued financial statements. The accompanying consolidated financial statements as of June 30, 2017 and 2016 and for the three and six 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 June 30, 2017 , Generation has outstanding commitments to invest in middle market lending, private equity investments and real estate investments of approximately $280 million , $218 million , and $98 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 June 30, 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 June 30, 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 predominantly 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)	6 Months Ended
	Jun. 30, 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. Exelon has not early adopted this 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. The Registrants currently expense those costs as incurred. These expenses are not expected to be material to the Registrants’ financial statements. 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 conducting this assessment, the Registrants have performed 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; • During the second quarter 2017, certain previously open implementation issues have been substantially resolved, including the collectability of utility tariff sale contracts and the accounting for bundled sales contracts. The Utility Registrants’ tariff sale contracts, including those with lower credit quality customers, are generally deemed to be probable of collection under the guidance and, thus, the timing of revenue recognition will continue to be based on the electricity or natural gas supplied in the period, consistent with current practice. Revenues recognized from bundled sales contracts are generally expected to be recognized based on the invoice price, consistent with current practice; and • Contributions in aid of construction are expected to be outside of the scope of the standard and, therefore, will continue to be accounted for as a reduction to Property, Plant, and Equipment. The Registrants generally anticipate that the implementation of the new standard will not have a material impact on the amount and timing of revenue recognition. However, certain implementation issues continue to be evaluated through the Industry Task Force process that could have an impact on the Registrants’ Consolidated Balance Sheets, Consolidated Statements of Operations and Comprehensive Income, Consolidated Statements of Cash Flows and disclosures. 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 eligible for capitalization). Exelon is currently evaluating the impact of this standard on its consolidated financial statements, 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 plans and apply multi-employer accounting. Multi-employer accounting is not impacted by this standard, so there is no impact on Exelon's subsidiary financial statements. The standard is effective January 1, 2018 and requires retrospective application for the presentation of the service cost component and the other components of net benefit cost and prospective application 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 January 1, 2019. 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 (with early adoption as of January 1, 2019 permitted) 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 June 30, 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 applied 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 is effective January 1, 2018, with early adoption permitted, 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 (current GAAP 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 January 1, 2018 with early adoption permitted. The guidance is required to be applied on a modified retrospective basis through a cumulative-effect adjustment 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 January 1, 2018 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)	6 Months Ended
	Jun. 30, 2017
Variable Interest Entity [Abstract]
Variable Interest Entity Disclosure (All Registrants)	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 June 30, 2017 and December 31, 2016 , Exelon, Generation, BGE, PHI and ACE collectively consolidated seven and nine VIEs or VIE groups, respectively, for which the applicable Registrant was the primary beneficiary ( see Consolidated Variable Interest Entities below) . As of June 30, 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 RSB BondCo LLC (BondCo) is a special purpose bankruptcy remote limited liability company formed by BGE to acquire, hold, issue and service bonds secured by rate stabilization property. BGE is required to remit all payments it receives from all residential customers through non-bypassable, rate stabilization charges to BondCo. On April 3, 2017, the rate stabilization bonds were fully redeemed. During the three and six months ended June 30, 2017 , BGE remitted $3 million and $22 million to BondCo, respectively, with all of the final $3 million remitted through June 30, 2017 after the bonds were fully redeemed. During the three and six months ended June 30, 2016 , BGE remitted $21 million and $42 million to BondCo, respectively. Upon the redemption of the bonds, BondCo no longer meets the definition of a variable interest entity and is removed from the list of consolidated VIEs noted below. However, BondCo will continue to be consolidated by BGE under the voting interest model. During 2009, Constellation formed a retail gas group to enter into a collateralized gas supply agreement with a third-party gas supplier. Upon assessment, the retail gas group was determined to be a VIE because there was not sufficient equity to fund the group’s activities without additional credit support and a $75 million parental guarantee provided by Generation. As the primary beneficiary, Generation consolidated the retail gas group. During the second quarter of 2017, the collateral structure was terminated with the third-party gas supplier except for the $75 million parental guarantee provided by Generation. Although the parental guarantee will remain, this is considered customary and reasonable for the unsecured position Generation has with the third-party gas supplier. As a result of the termination, the retail gas group no longer meets the definition of a VIE and is removed from the list of consolidated VIEs noted below. However, the retail gas group will continue to be consolidated by Generation under the voting interest model. Exelon's, Generation's, PHI's and ACE's consolidated VIEs consist of: • 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, 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 June 30, 2017 and December 31, 2016 , ComEd, PECO, Pepco and DPL did not have any material consolidated VIEs. As of June 30, 2017 and December 31, 2016 , Exelon, Generation, 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 $30 million in credit support for the retail power and gas companies for which Generation is the sole supplier of energy. • 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 were suspended during the term of the Reliability Support Services Agreement (RSSA), through the end of March 31, 2017. With the expiration of the RSSA, the PPA was reinstated beginning April 1, 2017 (see Note 5 — Regulatory Matters for additional details), • Generation provided a $400 million loan to CENG. As of June 30, 2017 , the remaining obligation is $324 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 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 and six months ended June 30, 2017 , ACE transferred $8 million and $27 million to ATF, respectively. During the three and six months ended June 30, 2016 , ACE transferred $12 million and $26 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, PHI and ACE did not provide any additional material financial support to the VIEs; • Exelon, Generation, 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, 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 June 30, 2017 and December 31, 2016 are as follows: June 30, 2017 December 31, 2016 Successor Successor Exelon (a) Generation PHI (a) ACE Exelon (a)(b) Generation BGE PHI (a) ACE Current assets $ 512 $ 501 $ 11 $ 7 $ 954 $ 916 $ 23 $ 14 $ 9 Noncurrent assets 8,617 8,585 32 23 8,563 8,525 3 35 23 Total assets $ 9,129 $ 9,086 $ 43 $ 30 $ 9,517 $ 9,441 $ 26 $ 49 $ 32 Current liabilities $ 573 $ 535 $ 38 $ 34 $ 885 $ 802 $ 42 $ 42 $ 37 Noncurrent liabilities 2,723 2,640 83 74 2,713 2,612 — 101 89 Total liabilities $ 3,296 $ 3,175 $ 121 $ 108 $ 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 June 30, 2017 and December 31, 2016 , these assets and liabilities primarily consisted of the following: June 30, 2017 December 31, 2016 Successor Successor Exelon (a) Generation PHI (a) ACE Exelon (a)(b) Generation BGE PHI (a) ACE Cash and cash equivalents $ 68 $ 68 $ — $ — $ 150 $ 150 $ — $ — $ — Restricted cash 55 48 7 7 59 27 23 9 9 Accounts receivable, net Customer 106 106 — — 371 371 — — — Other 24 24 — — 48 48 — — — Mark-to-market derivatives assets — — — — 31 31 — — — Inventory Materials and supplies 193 193 — — 199 199 — — — Other current assets 38 34 4 — 50 44 — 5 — Total current assets 484 473 11 7 908 870 23 14 9 Property, plant and equipment, net 5,293 5,293 — — 5,415 5,415 — — — Nuclear decommissioning trust funds 2,341 2,341 — — 2,185 2,185 — — — Goodwill — — — — 47 47 — — — Mark-to-market derivative assets — — — — 23 23 — — — Other noncurrent assets 267 235 32 23 315 277 3 35 23 Total noncurrent assets 7,901 7,869 32 23 7,985 7,947 3 35 23 Total assets $ 8,385 $ 8,342 $ 43 $ 30 $ 8,893 $ 8,817 $ 26 $ 49 $ 32 Long-term debt due within one year $ 191 $ 154 $ 37 $ 33 $ 181 $ 99 $ 41 $ 40 $ 35 Accounts payable 80 80 — — 269 269 — — — Accrued expenses 48 47 1 1 119 116 1 2 2 Mark-to-market derivative liabilities — — — — 60 60 — — — Unamortized energy contract liabilities 16 16 — — 15 15 — — — Other current liabilities 5 5 — — 30 30 — — — Total current liabilities 340 302 38 34 674 589 42 42 37 Long-term debt 616 533 83 74 641 540 — 101 89 Asset retirement obligations 1,954 1,954 — — 1,904 1,904 — — — Pension obligation (c) — — — — 9 9 — — — Unamortized energy contract liabilities 13 13 — — 22 22 — — — Other noncurrent liabilities 98 98 — — 106 106 — — — Total noncurrent liabilities 2,681 2,598 83 74 2,682 2,581 — 101 89 Total liabilities $ 3,021 $ 2,900 $ 121 $ 108 $ 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 predominantly 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 June 30, 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 the first quarter 2017, there is no further payment obligation under the parental guarantee. The following tables present summary information about Exelon's and Generation’s significant unconsolidated VIE entities: June 30, 2017 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 641 $ 529 $ 1,170 Total liabilities (a) 64 229 293 Exelon's ownership interest in VIE (a) — 268 268 Other ownership interests in VIE (a) 577 32 609 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 268 268 Contract intangible asset 9 — 9 Debt and payment guarantees — — — Net assets pledged for Zion Station decommissioning (b) 6 — 6 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 $75 million and $113 million as of June 30, 2017 and December 31, 2016 , respectively; offset by payables to ZionSolutions LLC of $69 million and $104 million as of June 30, 2017 and December 31, 2016 , respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE. See Note 12 - Nuclear Decommissioning for additional details. For each of the unconsolidated VIEs, Exelon and Generation have 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	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
Mergers, Acquisitions and Dispositions	Mergers, Acquisitions and Dispositions (Exelon, Generation, PHI and Pepco) 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 June 30, 2017 , Generation had remitted purchase price consideration of $293 million (including $239 million of cash and $54 million of nuclear fuel) to and on behalf of Entergy. 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 June 30, 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 June 30, 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 and six months ended June 30, 2017 , Exelon and Generation incurred $16 million and $47 million , respectively, of merger and integration related costs which are included within Operating and maintenance expense in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. 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. During the second quarter of 2017, Exelon finalized the application of $8 million funding for low- and moderate-income customers in the Pepco Maryland and DPL Maryland service territories. This resulted in an adjustment to merger commitment costs recorded at Exelon Corporate, Pepco, and DPL. Exelon Corporate recorded an increase of $8 million and Pepco and DPL recorded a decrease of $6 million and $2 million , respectively, in Operating and maintenance expense. 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 $ 67 $ 101 $ 259 $ 259 Energy efficiency 2016 - 2021 — — — — 122 Charitable contributions 2016 - 2026 28 12 10 50 50 Delivery system modernization Q2 2017 — — — — 22 Green sustainability fund Q2 2017 — — — — 14 Workforce development 2016 - 2020 — — — — 17 Other 1 5 — 6 29 Total $ 120 $ 84 $ 111 $ 315 $ 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 notices of appeal. On January 27, 2017, the Maryland Court of Special Appeals affirmed the Circuit Court's judgment that the MDPSC did not err in approving the merger. The OPC and Sierra Club filed petitions seeking further review in the Court of Appeals of Maryland, which is the highest court in Maryland. On June 21, 2017, the Court of Appeals granted discretionary review of the January 27, 2017 decision by the Maryland Court of Special Appeals. The Maryland Court of Appeals will review the OPC argument that the MDPSC did not properly consider the acquisition premium paid to PHI shareholders under Maryland’s merger approval standard and the Sierra Club’s argument that the merger would harm the renewable and distributed generation markets. The two lower courts examining these issues rejected these arguments, which Exelon believes are without merit. The petitioners’ briefs were filed on July 31, 2017, and briefs of Exelon and the MDPSC are due on August 30, 2017. The case is set for oral argument in October 2017. 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 July 20, 2017, the Court issued an opinion rejecting all of appellants’ arguments and affirming the Commission’s decision approving the merger. 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 180 Cash paid for PHI stock-based compensation equity awards (a) 29 Total purchase price $ 7,142 _____________ (a) 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 June 30, 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: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Operating revenues $ 1,113 $ 1,112 $ 2,332 $ 1,219 Net income (loss) 61 52 202 (262 ) For the three and six months ended June 30, 2017 and 2016 , the Registrants have recognized costs to achieve the PHI acquisition as follows: Three Months Ended June 30, Six Months Ended June 30, Acquisition, Integration and Financing Costs (a) 2017 2016 2017 2016 Exelon (b) $ 8 $ 1 $ 17 $ 103 Generation 4 4 13 20 ComEd (c) — 1 1 (7 ) PECO 1 1 2 2 BGE (d) 1 (5 ) 2 (4 ) Pepco (e) 1 (4 ) 2 23 DPL (f) — — (7 ) 16 ACE 1 2 2 15 Successor Predecessor Acquisition, Integration and Financing Costs (a) Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Six Months Ended June 30, 2017 March 24, 2016 to June 30, 2016 January 1, 2016 to March 23, 2016 PHI (g) $ 2 $ (1 ) $ (2 ) $ 55 $ 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 six months ended June 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 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 and six months ended June 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $6 million incurred at BGE that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. (e) For the three and six months ended June 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $9 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. (f) For the six months ended June 30, 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. For the three and six months ended June 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $3 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. (g) For the six months ended June 30, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. For the three months ended June 30, 2016 and the Successor period March 24, 2016 to June 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $12 million incurred at PHI 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 Six Months Ended Year Ended December 31, 2016 (a) 2016 (a) 2016 (b) Total operating revenues $ 6,910 $ 15,466 $ 32,342 Net income attributable to common shareholders 268 845 1,562 Basic earnings per share $ 0.29 $ 0.92 $ 1.69 Diluted earnings per share 0.29 0.91 1.69 ______________ (a) The amounts above include adjustments for non-recurring costs directly related to the merger of $1 million and $641 million for the three and six months ended June 30, 2016 , respectively, and intercompany revenue of $170 million for the six months ended June 30, 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 . Asset Divestitures (Exelon, Generation, PHI and Pepco) 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 secured a nonrecourse senior secured term loan facility, a revolving loan facility and certain commodity and interest rate swaps. 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 the sale, the normal and ordinary costs of operating the plants and repayment of the secured debt of EGTP, including the revolving credit facility. See Note 10 - Debt and Credit Agreements for details regarding the nonrecourse debt associated with EGTP. As a result, certain EGTP assets and liabilities were classified as held for sale at their respective fair values less costs to sell and included in the other current assets and other current liabilities balances on Exelon's and Generation's Consolidated Balance Sheets. At June 30, 2017, a $418 million pre-tax impairment loss was recorded within Operating and maintenance expense on Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. See Note 6 - Impairment of Long-Lived Assets for further information. On April 21, 2016, Generation completed the sale of the retired New Boston generating site, located in Boston, Massachusetts, resulting in a pre-tax gain of approximately $32 million . On May 2, 2016, Pepco completed the sale of the New York Avenue land parcel, located in Washington D.C., resulting in a pre-tax gain of approximately $8 million at Pepco. Due to the fair value adjustments recorded at Exelon and PHI as part of purchase accounting, no gain was recorded in the Exelon and PHI Consolidated Statements of Operations and Comprehensive Income.

Regulatory Matters (All Registr

Regulatory Matters (All Registrants)	6 Months Ended
	Jun. 30, 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 had 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 was reflected in customer rates in April 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 was effective June 1, 2017, and includes, among other provisions, (1) a Zero Emission Standard (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 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. On July 21, 2017, Exelon and others submitted comments on the IPA’s draft Procurement Plan. The IPA filed the plan with the ICC on July 31, 2017. The ICC has 45 days to approve the plan. Once the plan is approved by the ICC, bidders interested in participating in the procurement process will have 14 days to submit the required eligibility information and become qualified bidders. Generation’s Clinton and Quad Cities nuclear plants will participate in the procurement process. Winning bidders will contract directly with Illinois utilities, including ComEd, for 10-year terms extending through May 31, 2027. 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 annual future adjustments determined by the IPA for specified escalation and pricing adjustment mechanisms designed to lower the ZEC price based on increases in underlying energy and capacity prices. Utilities will be required to purchase an amount of ZECs equivalent to 16% of the actual amount of electricity delivered in 2014, subject to specified annual caps. For the initial delivery year, June 1, 2017 - May 31, 2018, the targeted procurement of ZECs, after applying the cap, is set at $235 million (ComEd’s share is approximately $170 million ). For subsequent delivery years, the IPA-approved targeted ZEC procurement amounts will change based on forward energy and capacity prices ComEd currently expects to enter into contracts with winning bidders in the fourth quarter 2017, at which time it will begin recording an associated obligation and expense for the procurement of ZEC's. Winning bidders will be entitled to compensation for the sale of ZECs retroactive to the June 1, 2017 effective date of FEJA. ComEd will recover all costs associated with purchasing ZECs through a new rate rider that provides 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 with interest. ComEd began billing its retail customers under its new ZEC rate rider on June 1, 2017 and recorded a regulatory liability of $22 million as of June 30, 2017 for revenues recorded in advance of incurring expenses. 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 PJM's FERC-approved 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. In addition, on March 31, 2017, plaintiffs in both lawsuits filed motions for preliminary injunction with the court; the court stayed briefing on the motions for preliminary injunction until the resolution of the motions to dismiss. On July 14, 2017, the court granted the motions to dismiss and also dismissed the motions for preliminary injunction. On July 17, 2017, the plaintiffs appealed the court’s decisions to the U.S. Court of Appeals for the Seventh Circuit. 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 additional information regarding the economic challenges facing Generation’s Clinton and Quad Cities nuclear plants and the expected benefits of the ZES. 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 in first quarter 2017. As of June 30, 2017 , ComEd recorded an increase to Operating revenues and its electric distribution services costs regulatory asset of approximately $36 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 Prior to FEJA, Illinois law required 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. On June 30, 2017, ComEd filed its 2018 - 2021 energy efficiency plan with the ICC, which must be approved no later than September 14, 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. Beginning January 1, 2018 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, PJM capacity revenues, and the projected year-end regulatory asset balance less any related deferred income 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 actual year-end energy efficiency regulatory asset balances less any related deferred income taxes. 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. ComEd cancelled its existing energy efficiency rate rider effective June 2, 2017. ComEd will 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 June 30, 2017, ComEd’s over-recoveries associated with its former energy efficiency rate rider were $88 million , which were reflected in Current regulatory liabilities on Exelon’s and ComEd’s Consolidated Balance Sheets as ComEd expects to provide the one-time credit to customers within the next twelve months. Initial Energy Efficiency Formula Rate Filing On June 9, 2017, ComEd filed its new initial energy efficiency formula rate with the ICC pursuant to FEJA. The filing establishes the formula under which energy efficiency rates will be calculated going forward and the revenue requirement used to set the initial rates for the period October 1, 2017 through December 31, 2017 subject to the ICC’s review and approval, which is required by August 23, 2017. The initial revenue requirement is based on projected costs and projected PJM capacity revenues for the period from June 1, 2017 through December 31, 2017, and projected year-end 2017 energy efficiency regulatory asset balances (less any related deferred income taxes). ComEd requested an initial decrease in revenue requirement of $7 million reflecting higher projected PJM capacity revenues compared to projected energy efficiency costs and provides for a weighted average debt and equity return 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 2017 will be included in ComEd’s 2018 energy efficiency formula rate filing and reflected in customer rates beginning January 2019. As of June 30, 2017, under the new formula rate, Exelon and ComEd deferred $21 million of energy efficiency costs as a regulatory asset. ComEd also recorded a regulatory liability of $2 million for the 2017 energy efficiency formula rate annual reconciliation. 2017 Energy Efficiency Formula Rate Filing On June 30, 2017, ComEd filed its annual energy efficiency formula rate with the ICC pursuant to FEJA. The filing establishes the revenue requirement used to set rates that will take effect in January 2018 after the ICC’s review and approval, which is due no later than September 14, 2017. The revenue requirement for 2018 is based on projected 2018 energy efficiency costs and PJM capacity revenues, and year-end 2018 energy efficiency regulatory asset balances (less any related deferred income taxes). In its 2017 filing ComEd requested a total increase to the revenue requirement of $12 million and provides for a weighted average debt and equity return 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 2018 will be included in ComEd’s 2019 energy efficiency formula rate filing, and reflected in customer rates beginning January 2020. 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. FEJA also requires ComEd to use RPS collections to fund utility job training and workforce development programs in the amounts of $10 million in each of the years 2017, 2021, and 2025. ComEd recorded a $10 million and $20 million current and non-current liability, respectively, as of June 30, 2017 associated with this obligation. ComEd will recover all costs associated with purchasing RECs and funding utility job training and workforce development programs through a new RPS rate rider that provides 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 with interest. The first reconciliation and true-up for RECs will occur in 2021 and 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. ComEd began billing its retail customers under its new RPS rate rider on June 1, 2017 and recorded a related regulatory asset of $19 million as of June 30, 2017. Any over-recovered RPS costs will be deposited into a separate interest bearing bank account pursuant to FEJA, which will be classified as Restricted cash on Exelon’s and ComEd’s Consolidated Balance Sheets. 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. On June 30, 2017, ComEd submitted 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 . Such projections indicate that customer rate impacts will not exceed the limitations set by FEJA discussed below. 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 records 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 be established under FEJA, ComEd records a regulatory asset or liability for any differences between revenues and incurred expenses. 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 June 30, 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 took 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. 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. The PAPUC approved PECO's petition for its proposed modified gas LTIIP on June 14, 2017 for spending of $762 million over a 10 year 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. 2017 Maryland Electric Distribution Rates (Exelon, PHI and DPL). On July 14, 2017, DPL filed an application with the MDPSC to increase its annual electric distribution base rates by $27 million based on a requested ROE of 10.1% . DPL expects a decision on the matter in the first quarter of 2018. DPL cannot predict how much of the requested increase the MDPSC will approve. 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. 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's positions on recovery of CWC and pass-through recovery of BGE’s actual uncollectibles and incremental costs. The order also grants BGE a 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. The residential consumer advocate filed its Memorandum on Appeal on June 5, 2017 and subsequent Reply Memoranda were filed by BGE and the MDPSC on July 7, 2017 and July 12, 2017, respectively. Oral arguments are scheduled for August 7, 2017. 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 June 30, 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 $137 million of unamortized incremental deployment costs of the AMI program, $56 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 June 30, 2017 reflects the impact of the cost disallowances and adjustments in BGE's 2015 electric and natural gas distribution rate case. 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 $56 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 base 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% . Delaware law allowed DPL to put into effect $2.5 million of each of the rate increases effective July 16, 2016. On December 17, 2016, the DPSC approved an additional $29.6 million in electric distribution rates and an additional $10.4 million in natural gas distribution rates effective December 17

Impairment of Long-lived Assets

Impairment of Long-lived Assets (Exelon and Generation)	6 Months Ended
	Jun. 30, 2017
Property, Plant and Equipment [Abstract]
Asset Impairment Charges [Text Block]	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. EGTP’s operating cash flows have been negatively impacted by certain market conditions and the seasonality of its cash flows. On May 2, 2017, EGTP entered into a consent agreement with its lenders to 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 the sale, the normal and ordinary costs of operating the plants and repayment of the secured debt of EGTP. As a result, certain EGTP’s assets and liabilities were classified as held for sale at their respective fair values less costs to sell and included in the other current assets and other current liabilities balances on Exelon’s and Generation’s Consolidated Balance Sheets at June 30, 2017. Additionally, a pre-tax impairment charge of $418 million was recorded in June 2017 within Operating and maintenance expense on Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. See Note 4 - Mergers, Acquisitions and Dispositions for additional information. 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 - Mergers, Acquisitions and Dispositions of the Exelon 2016 Form 10-K for further information. In the second quarter of 2016, updates to the Company's long-term view of energy and capacity prices suggested that the carrying value of a group of merchant wind assets, located in West Texas, may be impaired. Upon review, the estimated undiscounted future cash flows and fair value of the group were less than their carrying value. The fair value analysis was based on the income approach using significant unobservable inputs (Level 3) including revenue and generation forecasts, projected capital and maintenance expenditures and discount rates. As a result of the fair value analysis, long-lived assets held and used with a carrying amount of approximately $60 million were written down to their fair value of $24 million and a pre-tax impairment charge of $36 million was recorded during the second quarter in Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. Also in the second quarter of 2016 , updates to the Company's long-term view, as described above, in conjunction with the previous decision to early retire the Clinton and Quad Cities nuclear facilities in Illinois suggested that the carrying value of our Midwest asset group may be impaired. Generation completed a comprehensive review of the estimated undiscounted future cash flows of the Midwest asset group and no impairment charge was required. 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)	6 Months Ended
	Jun. 30, 2017
Property, Plant and Equipment [Abstract]
Implications Of Potential Early Retirement Disclosure [Text Block]	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. 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. 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. The TMI nuclear plant did not clear in the May 2017 PJM capacity auction for the 2020-2021 planning year and will not receive capacity revenue for that period, the third consecutive year that TMI failed to clear the PJM base residual capacity auction. The plant is currently committed to operate through May 2019. Based on these capacity auction results, prolonged periods of low wholesale power prices, and the absence of federal or state policies that place a value on nuclear energy for its ability to produce electricity without air pollution, Exelon announced that Generation will permanently cease generation operations at TMI on or about September 30, 2019. The current NRC license for TMI expires in 2034. Generation is proceeding with the market and regulatory notifications that must be made to shut down the plant, including filing of a deactivation notice with PJM on May 30, 2017 and notification to the NRC on June 20, 2017. PJM has subsequently notified Generation that it has not identified any reliability issues and has approved the deactivation of TMI as proposed. In the second quarter of 2017, as a result of the plant retirement decision of TMI, Exelon and Generation recognized one-time charges in Operating and maintenance expense of $71 million related to materials and supplies inventory reserve adjustments, employee-related costs and construction work-in-progress (CWIP) impairments, among other items. In addition to these one-time charges, there will be ongoing annual incremental non-cash charges to earnings stemming from shortening the expected economic useful life of TMI primarily related to accelerated depreciation of plant assets (including any ARC), accelerated amortization of nuclear fuel, and additional ARO accretion expense associated with the changes in decommissioning timing and cost assumptions. Exelon’s and Generation’s second quarter 2017 results include an incremental $37 million of pre-tax expense for these items. Please refer to Note 12 — Nuclear Decommissioning for additional detail on changes to the nuclear decommissioning ARO balances resulting from the early retirement of TMI. Income statement expense (pre-tax) June 30, 2017 Depreciation and amortization Accelerated depreciation (a) $ 35 Accelerated Nuclear Fuel amortization 2 Total $ 37 ________ (a) Reflects incremental accelerated depreciation of plant assets, including any ARC. 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) Reflects incremental accelerated depreciation of plant assets, including any ARC, for the period June 2, 2016, through December 6, 2016. (b) Primarily includes 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.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities (All Registrants)	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : Exelon June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 1,757 $ — $ 1,757 $ — $ 1,757 Long-term debt (including amounts due within one year) (a) 33,934 — 33,460 1,956 35,416 Long-term debt to financing trusts (b) 641 — — 693 693 SNF obligation 1,139 — 830 — 830 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 716 $ — $ 716 $ — $ 716 Long-term debt (including amounts due within one year) (a) 9,754 — 8,061 1,661 9,722 SNF obligation 1,139 — 830 — 830 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 389 $ — $ 389 $ — $ 389 Long-term debt (including amounts due within one year) (a) 7,036 — 7,728 — 7,728 Long-term debt to financing trusts (b) 205 — — 223 223 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,580 $ — $ 2,834 $ — $ 2,834 Long-term debt to financing trusts 184 — — 199 199 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 85 $ — $ 85 $ — $ 85 Long-term debt (including amounts due within one year) (a) 2,282 — 2,497 — 2,497 Long-term debt to financing trusts (b) 252 — — 271 271 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) June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 67 $ — $ 67 $ — $ 67 Long-term debt (including amounts due within one year) (a) 5,952 — 5,707 295 6,002 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,545 $ — $ 3,065 $ 9 $ 3,074 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 25 $ — $ 25 $ — $ 25 Long-term debt (including amounts due within one year) (a) 1,326 — 1,398 — 1,398 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 42 $ — $ 42 $ — $ 42 Long-term debt (including amounts due within one year) (a) 1,138 — 980 286 1,266 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 $185 million , $53 million , $44 million , $15 million , $14 million , $6 million , $33 million , $11 million , and $5 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of June 30, 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 June 30, 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 as of June 30, 2017 for the fair value of the one-time fee obligation associated with closing of the FitzPatrick acquisition on 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 six months ended June 30, 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 June 30, 2017 and December 31, 2016 : Generation Exelon As of June 30, 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) $ 29 $ — $ — $ — $ 29 $ 257 $ — $ — $ — $ 257 NDT fund investments Cash equivalents (b) 117 67 — — 184 117 67 — — 184 Equities 3,980 717 — 2,104 6,801 3,980 717 — 2,104 6,801 Fixed income Corporate debt — 1,656 255 — 1,911 — 1,656 255 — 1,911 U.S. Treasury and agencies 1,767 32 — — 1,799 1,767 32 — — 1,799 Generation Exelon As of June 30, 2017 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Foreign governments — 51 — — 51 — 51 — — 51 State and municipal debt — 232 — — 232 — 232 — — 232 Other (c) — 46 — 502 548 — 46 — 502 548 Fixed income subtotal 1,767 2,017 255 502 4,541 1,767 2,017 255 502 4,541 Middle market lending — — 428 78 506 — — 428 78 506 Private equity — — — 197 197 — — — 197 197 Real estate — — — 441 441 — — — 441 441 NDT fund investments subtotal (d) 5,864 2,801 683 3,322 12,670 5,864 2,801 683 3,322 12,670 Pledged assets for Zion Station decommissioning Cash equivalents 21 — — — 21 21 — — — 21 Middle market lending — — 21 33 54 — — 21 33 54 Pledged assets for Zion Station (e) 21 — 21 33 75 21 — 21 33 75 Rabbi trust investments Cash equivalents 5 — — — 5 78 — — — 78 Mutual funds 22 — — — 22 54 — — — 54 Fixed income — — — — — — 13 — — 13 Life insurance contracts — 20 — — 20 — 67 21 — 88 Rabbi trust investments subtotal 27 20 — — 47 132 80 21 — 233 Commodity derivative assets Economic hedges 632 2,698 1,604 — 4,934 632 2,698 1,604 — 4,934 Proprietary trading 3 47 31 — 81 3 47 31 — 81 Effect of netting and allocation of collateral (f) (g) (627 ) (2,343 ) (767 ) — (3,737 ) (627 ) (2,343 ) (767 ) — (3,737 ) Commodity derivative assets subtotal 8 402 868 — 1,278 8 402 868 — 1,278 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 11 — — 11 Economic hedges — 17 — — 17 — 17 — — 17 Proprietary trading 3 1 — — 4 3 1 — — 4 Effect of netting and allocation of collateral (3 ) (10 ) — — (13 ) (3 ) (10 ) — — (13 ) Interest rate and foreign currency derivative assets subtotal — 8 — — 8 — 19 — — 19 Other investments — — 41 — 41 — — 41 — 41 Total assets 5,949 3,231 1,613 3,355 14,148 6,282 3,302 1,634 3,355 14,573 Liabilities Commodity derivative liabilities Economic hedges (697 ) (2,691 ) (1,151 ) — (4,539 ) (697 ) (2,691 ) (1,407 ) — (4,795 ) Proprietary trading (4 ) (48 ) (25 ) — (77 ) (4 ) (48 ) (25 ) — (77 ) Effect of netting and allocation of collateral (f) (g) 698 2,627 897 — 4,222 698 2,627 897 — 4,222 Commodity derivative liabilities subtotal (3 ) (112 ) (279 ) — (394 ) (3 ) (112 ) (535 ) — (650 ) Interest rate and foreign currency derivative liabilities Generation Exelon As of June 30, 2017 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Economic hedges — (20 ) — — (20 ) — (20 ) — — (20 ) Proprietary trading (4 ) — — — (4 ) (4 ) — — — (4 ) Effect of netting and allocation of collateral 3 10 — — 13 3 10 — — 13 Interest rate and foreign currency derivative liabilities subtotal (1 ) (10 ) — — (11 ) (1 ) (10 ) — — (11 ) Deferred compensation obligation — (33 ) — — (33 ) — (131 ) — — (131 ) Total liabilities (4 ) (155 ) (279 ) — (438 ) (4 ) (253 ) (535 ) — (792 ) Total net assets $ 5,945 $ 3,076 $ 1,334 $ 3,355 $ 13,710 $ 6,278 $ 3,049 $ 1,099 $ 3,355 $ 13,781 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 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 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 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 $238 million and $252 million at June 30, 2017 and December 31, 2016 and restricted cash of $164 million and $157 million at June 30, 2017 and December 31, 2016 . Exelon excludes cash of $353 million and $360 million at June 30, 2017 and December 31, 2016 and restricted cash of $203 million and $180 million at June 30, 2017 and December 31, 2016 and includes long term restricted cash of $25 million at June 30, 2017 and December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) Includes $48 million and $29 million of cash received from outstanding repurchase agreements at June 30, 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 $771 million and $933 million at June 30, 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 liabilities of $29 million and $31 million at June 30, 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 June 30, 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 $71 million , $284 million and $130 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of June 30, 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), $84 million represents variation margin on the exchanges as of June 30, 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 June 30, 2017 and December 31, 2016 : ComEd PECO BGE As of June 30, 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) $ — $ — $ — $ — $ 28 $ — $ — $ 28 $ 5 $ — $ — $ 5 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 — — — — 35 10 — 45 10 — — 10 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (10 ) — (10 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (256 ) (256 ) — — — — — — — — Total liabilities — (7 ) (256 ) (263 ) — (10 ) — (10 ) — (4 ) — (4 ) Total net assets (liabilities) $ — $ (7 ) $ (256 ) $ (263 ) $ 35 $ — $ — $ 35 $ 10 $ (4 ) $ — $ 6 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 $39 million and $36 million at June 30, 2017 and December 31, 2016 and restricted cash of $12 million and $2 million at June 30, 2017 and December 31, 2016 . PECO excludes cash of $21 million and $22 million at June 30, 2017 and December 31, 2016 . BGE excludes cash of $12 million and $13 million at June 30, 2017 and December 31, 2016 and restricted cash of $3 million at June 30, 2017 and includes long term restricted cash of $2 million at June 30, 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 $237 million , respectively, at June 30, 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 June 30, 2017 and December 31, 2016 : Successor As of June 30, 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) $ 189 $ — $ — $ 189 $ 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 73 — — 73 73 — — 73 Fixed income — 13 — 13 — 16 — 16 Life insurance contracts — 23 21 44 — 22 20 42 Rabbi trust investments subtotal 73 36 21 130 73 38 20 131 Total assets 262 36 21 319 290 38 20 348 Liabilities Deferred compensation obligation — (24 ) — (24 ) — (28 ) — (28 ) Total liabilities — (24 ) — (24 ) — (28 ) — (28 ) Total net assets $ 262 $ 12 $ 21 $ 295 $ 290 $ 10 $ 20 $ 320 Pepco DPL ACE As of June 30, 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) $ 144 $ — $ — $ 144 $ — $ — $ — $ — $ 29 $ — $ — $ 29 Rabbi trust investments Cash equivalents 43 — — 43 — — — — — — — — Fixed income — 13 — 13 — — — — — — — — Life insurance contracts — 23 21 44 — — — — — — — — Rabbi trust investments subtotal 43 36 21 100 — — — — — — — — Total assets 187 36 21 244 — — — — 29 — — 29 Liabilities Deferred compensation obligation — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total liabilities — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 187 $ 32 $ 21 $ 240 $ — $ (1 ) $ — $ (1 ) $ 29 $ — $ — $ 29 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 $24 million and $19 million at June 30, 2017 and December 31, 2016 and includes long term restricted cash of $22 million and $23 million at June 30, 2017 and December 31, 2016 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $9 million at June 30, 2017 and December 31, 2016 . DPL excludes cash of $6 million and $4 million at June 30, 2017 and December 31, 2016 . ACE excludes cash of $7 million and $3 million at June 30, 2017 and December 31, 2016 and includes long term restricted cash of $22 million and $23 million at June 30, 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 and six months ended June 30, 2017 and 2016 : Successor Generation ComEd PHI Exelon Three Months Ended June 30, 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 March 31, 2017 $ 683 $ 20 $ 565 $ 40 $ 1,308 $ (282 ) $ 20 $ — $ 1,046 Total realized / unrealized gains (losses) Included in net income 1 — (3 ) (b) — (2 ) — — — (2 ) Included in noncurrent payables to affiliates 4 — — — 4 — — (4 ) — Included in payable for Zion Station decommissioning — 1 — — 1 — — — 1 Included in regulatory assets — — — — — 26 — 4 30 Change in collateral — — 31 — 31 — — — 31 Purchases, sales, issuances and settlements Purchases 19 — 21 1 41 — — — 41 Sales — — (13 ) — (13 ) — — — (13 ) Settlements (24 ) — — — (24 ) — — — (24 ) Transfers into Level 3 — — (8 ) — (8 ) — — — (8 ) Transfers out of Level 3 — — (4 ) — (4 ) — — — (4 ) Balance at June 30, 2017 $ 683 $ 21 $ 589 $ 41 $ 1,334 $ (256 ) $ 20 $ — $ 1,098 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of June 30, 2017 $ — $ — $ 43 $ — $ 43 $ — $ — $ — $ 43 Successor Generation ComEd PHI Exelon Six Months Ended June 30, 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 4 — (46 ) (b) 1 (41 ) — 1 — (40 ) Included in noncurrent payables to affiliates 13 — — — 13 — — (13 ) — Included in payable for Zion Station decommissioning — 1 — — 1 — — — 1 Included in regulatory assets — — — — — 2 — 13 15 Change in collateral — — 69 — 69 — — — 69 Purchases, sales, issuances and settlements Purchases 36 1 90 3 130 — — — 130 Sales — — (15 ) — (15 ) — — — (15 ) Issuances — — — — — — (1 ) — (1 ) Settlements (47 ) — — — (47 ) — — — (47 ) Transfers into Level 3 — — (10 ) — (10 ) — — — (10 ) Transfers out of Level 3 — — 8 (5 ) 3 — — — 3 Balance as of June 30, 2017 $ 683 $ 21 $ 589 $ 41 $ 1,334 $ (256 ) $ 20 $ — $ 1,098 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of June 30, 2017 $ 2 $ — $ 102 $ 1 $ 105 $ — $ 1 $ — $ 106 ___________________ (a) Includes $ 25 million of increases in fair value and an increase for realized losses due to settlements of $ 1 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended June 30, 2017 . Includes $ 5 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 six months ended June 30, 2017 . (b) Includes a reduction for the reclassification of $46 million and $148 million of realized gains due to the settlement of derivative contracts for the three and six months ended June 30, 2017 . Successor Generation ComEd PHI Exelon Three Months Ended June 30, 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 March 31, 2016 $ 684 $ 25 $ 1,047 $ 36 $ 1,792 $ (265 ) $ 20 $ — $ 1,547 Total realized / unrealized gains (losses) Included in net income 4 — (428 ) (b) — (424 ) — 1 — (423 ) Included in noncurrent payables to affiliates 8 — — — 8 — — (8 ) — Included in regulatory assets — — — — — 44 — 8 52 Change in collateral — — (32 ) — (32 ) — — — (32 ) Purchases, sales, issuances and settlements Purchases 85 — 23 1 109 — — — 109 Sales (1 ) — (1 ) — (2 ) — — — (2 ) Issuances — — — — — — (1 ) — (1 ) Settlements (65 ) — — — (65 ) — — — (65

Derivative Financial Instrument

Derivative Financial Instruments (All Registrants)	6 Months Ended
	Jun. 30, 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 June 30, 2017 , the percentage of expected generation hedged for the major reportable segments is 96% - 99% , 71% - 74% , and 39% - 42% 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 20% 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 2,312 GWhs and 4,162 GWhs for the three and six months ended June 30, 2017 , respectively, and 1,289 GWhs and 2,509 GWhs and for the three and six months June 30, 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 June 30, 2017 , Exelon had $800 million of notional amounts of fixed-to-floating hedges outstanding, and Exelon and Generation had $492 million of notional amounts of floating-to-fixed hedges outstanding. Assuming the 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 $3 million decrease in Exelon Consolidated pre-tax income for the six months ended June 30, 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 June 30, 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) $ — $ 14 $ 3 $ (11 ) $ 6 $ — $ 6 Mark-to-market derivative assets (noncurrent assets) — 3 1 (2 ) 2 11 13 Total mark-to-market derivative assets — 17 4 (13 ) 8 11 19 Mark-to-market derivative liabilities (current liabilities) — (17 ) (4 ) 11 (10 ) — (10 ) Mark-to-market derivative liabilities (noncurrent liabilities) — (3 ) — 2 (1 ) — (1 ) Total mark-to-market derivative liabilities — (20 ) (4 ) 13 (11 ) — (11 ) Total mark-to-market derivative net assets (liabilities) $ — $ (3 ) $ — $ — $ (3 ) $ 11 $ 8 _________ (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 June 30, Income Statement Location 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on Borrowings Exelon Interest expense $ 1 $ 5 $ 2 $ (1 ) Six Months Ended June 30, Income Statement Location 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on Borrowings Exelon Interest expense $ (4 ) $ 22 $ 10 $ (16 ) At June 30, 2017 , Exelon had total outstanding fixed-to-floating fair value hedges related to interest rate swaps of $800 million , with a derivative asset of $11 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 and six months ended June 30, 2017 and 2016 , the impact on the results of operations as a result of ineffectiveness from fair value hedges was a $3 million gain, a $7 million gain, a $4 million gain, and a $6 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 its long-term borrowings. The swaps were de-designated as cash flow hedges and, during the second quarter of 2017, upon termination of the debt, Generation terminated the swaps. The total notional amount of the swaps was $164 million . No gain or loss was recognized as a result of the termination of the swaps. See Note 10 — Debt and Credit Agreements of the Combined Notes to Consolidated Financial Statements for additional information. During the three and six months ended June 30, 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 $492 million as of June 30, 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 June 30, 2017 , the subsidiary had a $8 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 was $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 June 30, 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 $103 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 June 30, 2017 and December 31, 2016 , $2 million and $8 million of cash collateral held, respectively, was not offset against derivative positions because such collateral was not associated with any energy-related derivatives, were associated with accrual positions, or as of the balance sheet date there were no positions to offset. Excluded from the tables below are economic hedges that qualify for the NPNS scope exception and other non-derivative contracts that are accounted for under the accrual method of accounting. ComEd’s use of cash collateral is generally unrestricted unless ComEd is downgraded below investment grade (i.e., to BB+ or Ba1). Cash collateral held by PECO and BGE must be deposited in a non affiliate major U.S. commercial bank or foreign bank with a U.S. branch office that meet certain qualifications. In the table below, DPL's economic hedges are shown gross. The impact of the netting of fair value balances with the same counterparty that are subject to legally enforceable master netting agreements, as well as netting of cash collateral, is aggregated in the collateral and netting column. The following table provides a summary of the derivative fair value balances recorded by the Registrants as of June 30, 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) $ 3,198 $ 58 $ (2,429 ) $ 827 $ — $ — $ — $ — $ — $ 827 Mark-to-market derivative assets (noncurrent assets) 1,736 23 (1,308 ) 451 — — — — — 451 Total mark-to-market derivative assets 4,934 81 (3,737 ) 1,278 — — — — — 1,278 Mark-to-market derivative liabilities (current liabilities) (2,895 ) (52 ) 2,732 (215 ) (19 ) — — — — (234 ) Mark-to-market derivative liabilities (noncurrent liabilities) (1,644 ) (25 ) 1,490 (179 ) (237 ) — — — — (416 ) Total mark-to-market derivative liabilities (4,539 ) (77 ) 4,222 (394 ) (256 ) — — — — (650 ) Total mark-to-market derivative net assets (liabilities) $ 395 $ 4 $ 485 $ 884 $ (256 ) $ — $ — $ — $ — $ 628 ______ (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 $149 million and $74 million , respectively, and current and noncurrent liabilities are shown net of collateral of $155 million and $107 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $485 million at June 30, 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), $84 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

Debt and Credit Agreements (All

Debt and Credit Agreements (All Registrants)	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : Commercial Paper Borrowings June 30, 2017 December 31, 2016 Exelon Corporate $ — $ — Generation 569 620 ComEd 389 — BGE 85 45 Pepco — 23 DPL 25 — ACE 42 — 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 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 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. On May 26, 2017, each of the Registrants' respective syndicated revolving credit facilities had their maturity dates extended to May 26, 2022. Long-Term Debt Issuance of Long-Term Debt During the six months ended June 30, 2017 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Exelon Junior Subordinated Notes (a) 3.50 % June 1, 2022 $ 1,150 Refinance Exelon's Junior Subordinated Notes issued in June 2014. Generation Albany Green Energy Project Financing LIBOR + 1.25% November 17, 2017 $ 13 Albany Green Energy biomass generation development. Generation Energy Efficiency Project Financing 3.90 % February 1, 2018 $ 12 Funding to install energy conservation measures for the Naval Station Great Lakes project. Generation Energy Efficiency Project Financing 2.61 % September 30, 2018 $ 6 Funding to install energy conservation measures for the Pensacola project. Generation Energy Efficiency Project Financing 3.53 % April 1, 2019 $ 8 Funding to install energy conservation measures for the State Department project. Generation Energy Efficiency Project Financing 3.72 % May 1, 2018 $ 3 Funding to install energy conservation measures for the Smithsonian Zoo project. 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. Generation ExGen Texas Power Nonrecourse Debt LIBOR + 4.75% September 18, 2021 $ 6 Funding 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. Pepco First Mortgage Bonds 4.15 % March 15, 2043 $ 200 Funding to repay outstanding commercial paper and for general corporate purposes. _________ (a) See the Junior Subordinated Notes discussion below for further information. 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 June 30, 2017 , $662 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. On May 2, 2017, EGTP entered into a consent agreement with its lenders, which resulted in the outstanding debt balance being classified as Long-term debt due within one year on Exelon's and Generation's Consolidated Balance Sheets. See Note 4 - Mergers, Acquisitions and Dispositions and Note 6 - Impairment of Long-Lived Assets for more information. 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 used debt remarketing proceeds towards settling the forward equity purchase contract with Exelon on June 1, 2017. Exelon issued approximately 33 million shares of common stock from treasury stock and received $1.15 billion upon settlement of the forward equity purchase contract. When reissuing treasury stock Exelon uses the average price paid to repurchase shares to calculate a gain or loss on issuance and records gains or losses directly to retained earnings. A loss on reissuance of treasury shares of $1.05 billion was recorded to retained earnings as of June 30, 2017. See Note 16 - Earnings Per Share and Equity for further information on the issuance of common stock. BGE Redemption of Trust Preferred Securities On August 1, 2017, BGE announced that it intends to redeem all of the outstanding shares of BGE Capital Trust II 6.20% Preferred Securities, which totaled $258 million at June 30, 2017. The securities will be redeemed on August 28, 2017, pursuant to the optional redemption provisions of the Indenture under which the securities were issued. The redemption will be made to stockholders of record as of the close of business on August 25, 2017. The redemption price per share is $25.19 , which equals the stated value per share plus accrued and unpaid dividends to, but excluding, the redemption date. No dividends on the Securities being redeemed will accrue on or after the redemption date, nor will any interest accrue on amounts held to pay the redemption price.

Income Taxes (All Registrants)

Income Taxes (All Registrants)	6 Months Ended
	Jun. 30, 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 June 30, 2017 Successor Exelon (a) Generation (b) 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 (2,745.7) 5.6 5.8 (0.6) 5.0 3.2 4.6 5.6 4.3 Qualified nuclear decommissioning trust fund income 3,156.6 (6.3) — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (528.7) 0.9 (0.2) (0.1) (0.2) (0.1) (0.1) (0.4) (0.1) Plant basis differences (2,764.4) — (0.2) (16.0) (0.3) (6.2) (1.7) (3.3) (4.8) Production tax credits and other credits (1,035.7) 2.0 — — — — — — — Noncontrolling interests 84.7 (0.2) — — — — — — — Like-kind exchange (c) (5,362.4) — 5.9 — — — — — — Other 1,960.6 1.1 0.5 0.2 1.3 (0.2) 0.9 (3.6) 0.9 Effective income tax rate (7,200.0)% 38.1% 46.8% 18.5% 40.8% 31.7% 38.7% 33.3% 35.3% Three Months Ended June 30, 2016 Successor Exelon Generation (d) ComEd PECO BGE (e) 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 2.3 (116.7) 4.8 0.3 2.0 3.5 4.8 5.9 6.1 Qualified nuclear decommissioning trust fund income 5.7 591.2 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.8) (157.8) (0.2) (0.1) (0.4) (0.1) (0.6) (1.6) (0.3) Plant basis differences (f) (6.9) — (0.4) (11.3) (20.6) (5.7) (3.5) (7.1) (7.0) Production tax credits and other credits (5.8) (603.0) — — — — — — — Noncontrolling interest 0.9 94.4 — — — — — — — Statute of limitations expiration (1.7) (410.8) — — — — — — — Merger expenses 0.2 — — — — 0.2 3.1 — 1.0 Other (g) (3.3) (52.3) (0.6) (5.2) (1.0) (1.0) 1.2 7.8 1.0 Effective income tax rate 24.6% (620.0)% 38.6% 18.7% 15.0% 31.9% 40.0% 40.0% 35.8% Six Months Ended June 30, 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 (1.0) (13.6) 5.3 (0.1) 5.1 3.8 5.1 5.6 4.6 Qualified nuclear decommissioning trust fund income 5.6 51.2 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.7) (5.4) (0.2) (0.1) (0.1) (0.1) (0.2) (0.4) (0.2) Plant basis differences (4.3) — (0.2) (14.3) (0.7) (6.0) (1.8) (3.3) (4.3) Production tax credits and other credits (1.4) (12.3) — — — — — — — Noncontrolling interests (0.1) (0.5) — — — — — — — Merger expenses (h) (11.4) (13.7) — — — (16.2) (15.1) (85.3) (23.8) Fitzpatrick bargain purchase gain (6.5) (60.0) — — — — — — — Like-kind exchange (c) (3.7) — 2.9 — — — — — — Other 0.3 (4.2) 0.4 (0.1) 0.3 (0.7) 1.0 (1.6) — Effective income tax rate 11.8% (23.5)% 43.2% 20.4% 39.6% 15.8% 24.0% (50.0)% 11.3% Successor Predecessor Six Months Ended June 30, 2016 March 24, 2016 to June 30, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco (i) DPL (i) ACE (i) PHI (i) 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 (i) 0.8 2.6 4.9 0.7 4.6 (9.5) (5.2) 5.9 5.2 11.9 Qualified nuclear decommissioning trust fund income 5.6 9.8 — — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.7) (2.5) (0.2) (0.1) (0.1) 0.1 0.4 0.1 0.1 (0.9) Plant basis differences (f) (6.3) — (0.3) (10.2) (4.5) 12.6 2.0 1.0 1.7 (13.5) Production tax credits and other credits (5.5) (9.6) — — — — — — — — Noncontrolling interest 0.7 1.2 — — — — — — — — Statute of limitations expiration (1.0) (3.9) — — — — — — — — Merger expenses 14.5 — — — — (36.1) (30.5) (17.7) (18.9) 11.1 Other (g) (2.8) (3.8) (0.1) (2.4) 0.1 (0.5) (0.1) (0.1) — 3.6 Effective income tax rate 39.3% 28.8% 39.3% 23.0% 35.1% 1.6% 1.6% 24.2% 23.1% 47.2% (a) The effective tax rate for the three months ended June 30, 2017 is disproportionately impacted due to the decline in consolidated pre-tax GAAP earnings as compared to the federal and state tax impacts of the Like-kind exchange, tax credits, Plant basis differences, and Qualified nuclear decommissioning trust fund income. (b) Generation recognized a loss before income taxes for the three months ended June 30, 2017 . As a result, positive percentages represent an income tax benefit for the period presented. (c) See Like-Kind Exchange within the Other Income Tax Matters section below for further details. (d) The effective tax rate for the three months ended June 30, 2016, is disproportionately impacted due to the decline in pre-tax GAAP earnings as compared to the changes in tax credits and other reconciling items. In three months ended June 30, 2016, due to the expiration of a statute of limitations, Generation recorded an income tax benefit of $ 16 million . The statute of limitations expired in the third quarter of 2015; therefore, this represents an out of period adjustment. (e) The effective tax rate for the three months ended June 30, 2016 is disproportionately impacted due to the decline in pre-tax GAAP earnings and changes in other reconciling items. (f) At BGE, includes a cumulative adjustment related to a regulatory asset. (g) At PECO, includes a cumulative adjustment related to an anticipated gas repairs tax return accounting method change. (h) Includes a remeasurement of uncertain federal and state income tax positions, see below. (i) Pepco, DPL and ACE recognized a loss before income taxes for the six months ended June 30, 2016 , and PHI recognized a loss before income taxes for the period of March 24, 2016, through June 30, 2016 . As a result, positive percentages represent an income tax benefit for the periods presented. (j) Includes a remeasurement of uncertain state income tax positions for Pepco and DPL. Accounting for Uncertainty in Income Taxes The Registrants have the following unrecognized tax benefits as of June 30, 2017 and December 31, 2016 : Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE June 30, 2017 $ 730 $ 467 $ 2 $ — $ 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 June 30, 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. Exelon reduced the liability related to the uncertain tax position associated with the like-kind exchange in the second quarter of 2017. Please see the Other Income Tax Matters section below for additional details related to the like-kind exchange adjustments made in the second quarter of 2017. 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 June 30, 2017 , Exelon and ComEd have approximately $ 39 million and $2 million , respectively, of unrecognized federal and state income tax benefits that could significantly decrease 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 and ComEd's effective tax rate. Settlement of Income Tax Audits As of June 30, 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 (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 the second half of 2017. In June of 2017, the IRS finalized its computation of tax, penalties and interest owed by Exelon pursuant to the Tax Court’s decision. 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. Exelon agreed to hold ComEd harmless from any unfavorable impacts on ComEd’s equity of the after-tax interest and penalty amounts. 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 from the like-kind exchange position, ComEd recorded on its Consolidated Balance Sheets as of September 30, 2016, a $ 150 million receivable and non-cash equity contributions from Exelon. As a result of the IRS’s finalization of its computation in the second quarter 2017, Exelon recorded a benefit to earnings of approximately $ 26 million , consisting of an income tax benefit of $ 50 million and a reduction of penalties of $ 2 million , partially offset by after-tax interest expense of $ 26 million , while ComEd recorded a charge to earnings of approximately $ 23 million , consisting of income tax expense of $ 15 million and after-tax interest expense of $ 8 million . In the second quarter of 2017, Exelon amended its agreement with ComEd to also hold ComEd harmless for the unfavorable impacts on its equity from the additional income tax amounts owed by ComEd as a result of the IRS’s finalization of its computation related to the like-kind exchange position. Accordingly, in the second quarter of 2017, ComEd recorded an additional receivable and non-cash equity contribution from Exelon for the total $ 23 million . 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 second half of 2017). Exelon expects that a payment of approximately $ 1.3 billion related to the like-kind exchange will be due, including $ 300 million from ComEd, in the second half 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 on ComEd’s equity from the like-kind exchange position. Upon a final appellate decision, which could take up to several years, Exelon expects to receive approximately $ 60 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 second half 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 June 30, 2017 , ComEd has a total receivable from Exelon pursuant to the hold harmless agreement of $ 369 million , which is included in Current Receivables from Affiliates on ComEd’s Consolidated Balance Sheet. Under the agreement, Exelon will settle this receivable with ComEd no later than the time that the payments related to the like-kind exchange are due to the IRS, currently anticipated in the second half of 2017. No recovery will be sought from ComEd customers for any interest, penalty or additional income tax payment amounts resulting from 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, ComEd, 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. On July 6, 2017, Illinois enacted Senate Bill 9, which permanently increased Illinois’ total corporate income tax rate from 7.75% to 9.50% effective July 1, 2017. As a result of the rate change, in the third quarter of 2017, after taking into account regulatory recovery of tax increases at Exelon, Generation and ComEd expect to record an estimated one-time increase to deferred income taxes of approximately $ 180 million , $ 15 million and $ 250 million , respectively. At ComEd, the increase to the Illinois deferred income tax liability will be offset by a regulatory asset. Exelon expects to record a decrease to income tax expense of approximately $ 70 million (net of federal taxes) and Generation expects to record an increase to income tax expense of approximately $ 15 million (net of federal taxes). The rate increase is not expected to have a material ongoing impact to Exelon’s, Generation’s and ComEd’s future results of operations.

Nuclear Decommissioning (Exelon

Nuclear Decommissioning (Exelon and Generation)	6 Months Ended
	Jun. 30, 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 June 30, 2017 : Nuclear decommissioning ARO at December 31, 2016 (a) $ 8,734 Acquisition of FitzPatrick 417 Net increase due to changes in, and timing of, estimated cash flows 103 Accretion expense 225 Costs incurred to decommission retired plants (3 ) Nuclear decommissioning ARO at June 30, 2017 (a)(b) $ 9,476 _________ (a) Includes $12 million and $10 million for the current portion of the ARO at June 30, 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 six months ended June 30, 2017 , Generation’s nuclear ARO increased by approximately $742 million . The increase is largely driven by the acquisition of FitzPatrick and the announced early retirement of TMI. 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 . Included in the $103 million net increase due to changes in, and timing of, estimated cash flows above, is $138 million associated with the May 30, 2017 announcement to early retire the TMI nuclear unit on September 30, 2019. Refer to Note 7 - Early Nuclear Plant Retirements for additional information regarding the announced early retirement of TMI. The increase in the ARO liability for TMI incorporates the early shutdown date, increases the probabilities of longer term decommissioning scenarios, and reflects an increase in the estimated costs to decommission based on updated decommissioning cost study reflecting the early retirement of the unit. 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 June 30, 2017 and December 31, 2016 , Exelon and Generation had NDT fund investments totaling $12,641 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 and six months ended June 30, 2017 and 2016 : Exelon and Generation Exelon and Generation Three Months Ended June 30, Six Months Ended 2017 2016 2017 2016 Net unrealized gains (losses) on decommissioning trust funds — Regulatory Agreement Units (a) $ (13 ) $ 52 $ 210 $ 131 Net unrealized gains on decommissioning trust funds — Non-Regulatory Agreement Units (b)(c) 70 48 235 100 _________ (a) Net unrealized gains (losses) related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets. (b) Excludes $(2) million and $1 million of net unrealized gains (losses) related to the Zion Station pledged assets for the three months ended June 30, 2017 and 2016 respectively. Excludes $(2) million and $3 million of net unrealized gains (losses) related to the Zion Station pledged assets for the six months ended June 30, 2017 and 2016, respectively. Net unrealized gains (losses) related to Zion Station pledged assets are included in Other current liabilities and Payable for Zion Station decommissioning on Exelon’s and Generation’s Consolidated Balance Sheets in 2017 and 2016, respectively. (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 $114 million which is included within the nuclear decommissioning ARO at June 30, 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 June 30, 2017 and December 31, 2016 : Exelon and Generation June 30, 2017 December 31, 2016 Carrying value of Zion Station pledged assets $ 75 $ 113 Payable to Zion Solutions (a) 69 104 Current portion of payable to Zion Solutions (b) 69 90 Cumulative withdrawals by Zion Solutions to pay decommissioning costs (c) 914 878 _________ (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. Generation will file its next decommissioning funding status report with the NRC by March 31, 2018 for shutdown reactors and reactors within five years of shutdown. This report will reflect the status of decommissioning funding assurance as of December 31, 2017 and will include the impact of the announced early retirement of TMI. A shortfall could require Exelon to post parental guarantee for Generation’s share of the funding assurance. However, the amount of any required guarantee will ultimately depend on the decommissioning approach adopted at TMI, the associated level of costs, and the decommissioning trust fund investment performance going forward.

Retirement Benefits (All Regist

Retirement Benefits (All Registrants)	6 Months Ended
	Jun. 30, 2017
Retirement Benefits [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 and six months ended June 30, 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 (a) 2016 (b) 2017 (a) 2016 (b) Components of net periodic benefit cost: Service cost $ 97 $ 91 $ 28 $ 28 Interest cost 211 212 46 48 Expected return on assets (299 ) (292 ) (41 ) (42 ) Amortization of: Prior service cost (benefit) 1 4 (47 ) (47 ) Actuarial loss 150 142 15 16 Settlement charges 2 — — — Net periodic benefit cost $ 162 $ 157 $ 1 $ 3 Pension Benefits Other Postretirement Benefits 2017 (a) 2016 (b) 2017 (a) 2016 (b) Components of net periodic benefit cost: Service cost $ 191 $ 170 $ 54 $ 54 Interest cost 422 403 91 90 Expected return on assets (598 ) (555 ) (82 ) (80 ) Amortization of: Prior service cost (benefit) 1 7 (94 ) (91 ) Actuarial loss 302 269 31 30 Settlement charges 2 — — — Net periodic benefit cost $ 320 $ 294 $ — $ 3 _______ (a) FitzPatrick net benefit costs are included for the period after acquisition. (b) 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 and six months ended June 30, 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 June 30, 2016 , respectively. Three Months Ended June 30, Six Months Ended June 30, Pension and Other Postretirement Benefit Costs 2017 2016 2017 2016 Exelon $ 163 $ 160 $ 320 $ 297 Generation (c) 59 55 113 109 ComEd 44 42 87 83 PECO 7 8 14 17 BGE 16 18 32 33 BSC (a) 13 10 26 24 Pepco (b) 6 7 13 16 DPL (b) 3 4 6 9 ACE (b) 3 4 7 8 PHISCO (a)(b) 12 12 22 21 Successor Predecessor Pension and Other Postretirement Benefit Costs Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Six Months Ended June 30, 2017 March 24, 2016 to June 30, 2016 January 1, 2016 to March 23, 2016 PHI $ 24 $ 27 $ 48 $ 31 $ 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 six months ended June 30, 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 . (c) FitzPatrick net benefit costs are included for the period after acquisition. 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 and six months ended June 30, 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 June 30, 2016 , respectively. Three Months Ended June 30, Six Months Ended June 30, Savings Plan Matching Contributions 2017 2016 2017 2016 Exelon $ 33 $ 30 $ 63 $ 56 Generation 14 13 28 25 ComEd 8 7 15 13 PECO 2 2 4 4 BGE 3 2 4 3 BSC (a) 3 2 5 7 Pepco (b) 1 1 2 2 DPL (b) 1 — 1 1 PHISCO (a)(b) 1 2 3 3 ACE — 1 1 1 Successor Predecessor Savings Plan Matching Contributions Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Six Months Ended June 30, 2017 March 24, 2016 to June 30, 2016 January 1, 2016 to March 23, 2016 PHI $ 3 $ 4 $ 7 $ 4 $ 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 six months ended June 30, 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 six months ended June 30, 2016 .

Severance (All Registrants)

Severance (All Registrants)	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 2017 and 2016 , Exelon, Generation, ComEd, PHI, Pepco, DPL, and ACE recorded the following severance costs associated with these ongoing severance benefits within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income. Successor Exelon Generation (a) ComEd (a) PHI Pepco (a) DPL (a) ACE (a) Three Months Ended June 30, 2017 $ 5 $ 1 $ 1 $ 3 $ 1 $ 1 $ 1 June 30, 2016 2 1 1 — — — — Six Months Ended June 30, 2017 $ 9 $ 4 $ 2 $ 3 $ 1 $ 1 $ 1 June 30, 2016 4 3 1 — — — — _______ (a) The amounts above for Generation include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017 , respectively, and $1 million and $2 million for the three and six months ended June 30, 2016 , respectively. The amounts above for ComEd include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017 , respectively, and less than $1 million and $1 million for the three and six months ended June 30, 2016 , respectively. Amounts billed by PHISCO to Pepco, DPL and ACE were $1 million , each, for both three and six months ended June 30, 2017 . Pepco, DPL and ACE did not have any ongoing severance plans for the three and six months ended June 30, 2016 . 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 June 30, 2017 and 2016 , the amounts for severance costs related to the cost management program were immaterial. For the six months ended June 30, 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 Six Months Ended June 30, 2017 (a) $ (1 ) $ (1 ) $ — $ — $ — June 30, 2016 (b) $ 17 $ 12 $ 3 $ 1 $ 1 _______ (a) Amounts billed by BSC through intercompany allocations for the six months ended June 30, 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 six months ended June 30, 2016 . Early Plant Retirement-Related Severance (Exelon and Generation) As a result of the Three Mile Island plant retirement decision, Exelon and Generation will incur certain employee-related costs, including severance benefit costs. Severance costs will be provided to management employees that are eligible under Exelon’s severance policy, to the extent that those employees are not redeployed to other locations. In June 2017, Exelon and Generation recognized severance costs of $17 million related to expected management employee severances resulting from the plant retirements within Operating and maintenance expense in their Consolidated Statements of Operation and Comprehensive Income. Approximately half of the employees at this location fall under a collective bargaining union agreement and are not eligible for severance benefits under an existing plan. The union and Exelon will negotiate terms of any severance benefits. If severance benefits are successfully negotiated, the amounts will be accrued as a one-time employee termination benefit once the established plan is communicated to employees. The final amount of the severance cost will ultimately depend on the specific employees severed. See Note - 7 Early Nuclear Plant Retirements for additional information regarding the announced early retirement of TMI. 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. Pepco and DPL maintain regulatory assets for merger related integration costs which include a portion of the severance costs related to the PHI merger that is either currently being recovered in rates or is deemed probable of recovery if not currently being recovered in rates. As of June 30, 2017 and 2016, Pepco and DPL have regulatory assets of $12 million and $13 million , respectively, and $9 million and $3 million , respectively. For the three and six months ended June 30, 2017 , the PHI merger severance costs were immaterial. For the three and six months ended June 30, 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 June 30, 2016 Severance costs (benefits) (a) $ 2 $ (1 ) $ (1 ) $ — $ — $ 4 $ 2 $ 1 $ 1 Six Months Ended June 30, 2016 Severance costs (a) $ 55 $ 9 $ 2 $ 1 $ 1 $ 42 $ 20 $ 12 $ 10 ______________ (a) The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $(1) million , $(1) million , less than $1 million , less than $1 million , $2 million , $1 million and $1 million , respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the three months ended June 30, 2016 , and $8 million , $2 million , $1 million , $1 million , $19 million , $11 million and $10 million for the six months ended June 30, 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) 25 17 1 — — 3 — — — Payments (18 ) (4 ) (1 ) — — (10 ) — — — Balance at June 30, 2017 $ 95 $ 49 $ 3 $ — $ — $ 22 $ — $ — $ — ______________ (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)	6 Months Ended
	Jun. 30, 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 six months ended June 30, 2017 and 2016 : Six Months Ended June 30, 2017 Gains 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 1 2 (58 ) 3 5 (47 ) Amounts reclassified from AOCI (b) 4 — 70 — — 74 Net current-period OCI 5 2 12 3 5 27 Ending balance $ (12 ) $ 6 $ (2,598 ) $ (27 ) $ (2 ) $ (2,633 ) Generation (a) Beginning balance $ (19 ) $ 2 $ — $ (30 ) $ (7 ) $ (54 ) OCI before reclassifications 1 — — 3 6 10 Amounts reclassified from AOCI (b) 4 — — — — 4 Net current-period OCI 5 — — 3 6 14 Ending balance $ (14 ) $ 2 $ — $ (27 ) $ (1 ) $ (40 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 Six Months Ended June 30, 2016 Gains 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 ) — (2 ) 6 (7 ) (13 ) Amounts reclassified from AOCI (b) 3 — 69 — — 72 Net current-period OCI (7 ) — 67 6 (7 ) 59 Ending balance $ (26 ) $ 3 $ (2,498 ) $ (34 ) $ (10 ) $ (2,565 ) Generation (a) Beginning balance $ (21 ) $ 1 $ — $ (40 ) $ (3 ) $ (63 ) OCI before reclassifications (7 ) — — 6 (4 ) (5 ) Amounts reclassified from AOCI (b) 3 — — — — 3 Net current-period OCI (4 ) — — 6 (4 ) (2 ) Ending balance $ (25 ) $ 1 $ — $ (34 ) $ (7 ) $ (65 ) 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 and six months ended June 30, 2017 and 2016 . The following tables present amounts reclassified out of AOCI to Net income for Exelon, Generation and PHI during the three and six months ended June 30, 2017 and 2016 . Three Months Ended June 30, 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 (losses) on cash flow hedges Other cash flow hedges $ — $ — Interest expense Total before tax — — Tax benefit — — Net of tax $ — $ — 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 24 — Net of tax $ (34 ) $ — Total Reclassifications for the period $ (34 ) $ — Comprehensive income Six Months Ended June 30, 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) $ 46 $ — Actuarial losses (b) (162 ) — Total before tax (116 ) — Tax benefit 46 — Net of tax $ (70 ) $ — Total Reclassifications $ (74 ) $ (4 ) Comprehensive income Three Months Ended June 30, 2016 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statement of Operations and Comprehensive Income Exelon Generation Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 19 $ — Actuarial losses (b) (75 ) — Total before tax (56 ) — Tax benefit 22 — Net of tax $ (34 ) $ — Total Reclassifications for the period $ (34 ) $ — Comprehensive income Six Months Ended June 30, 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 benefit 2 2 — Net of tax $ (3 ) $ (3 ) $ — Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 38 $ — $ — Actuarial losses (b) (151 ) — (1 ) Total before tax (113 ) — (1 ) Tax benefit 44 — — Net of tax $ (69 ) $ — $ (1 ) Total Reclassifications $ (72 ) $ (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 and six months ended June 30, 2017 and 2016 : Three Months Ended June 30, Six Months Ended 2017 2016 2017 2016 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 9 $ 7 $ 18 $ 15 Actuarial loss reclassified to periodic benefit cost (32 ) (30 ) (64 ) (60 ) Pension and non-pension postretirement benefit plans valuation adjustment 1 — 3 1 Change in unrealized (loss)/gain on cash flow hedges (2 ) 2 (3 ) 4 Change in unrealized (loss)/gain on equity investments — 1 (3 ) 3 Change in unrealized (loss)/gain on marketable securities — (1 ) (1 ) — Total $ (24 ) $ (21 ) $ (50 ) $ (37 ) Generation Change in unrealized (loss)/gain on cash flow hedges $ (2 ) $ 1 $ (3 ) $ 3 Change in unrealized (loss)/gain on equity investments — 1 (2 ) 3 Total $ (2 ) $ 2 $ (5 ) $ 6 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)	6 Months Ended
	Jun. 30, 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 June 30, Six Months Ended June 30, 2017 2016 2017 2016 Exelon Net income attributable to common shareholders $ 80 $ 267 $ 1,076 $ 440 Weighted average common shares outstanding — basic 934 924 931 923 Assumed exercise and/or distributions of stock-based awards 2 2 1 3 Weighted average common shares outstanding — diluted 936 926 932 926 The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was approximately 8 million and 9 million for the three and six months ended June 30, 2017 , respectively, and 11 million and 12 million for the three and six months ended June 30, 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 and six months ended June 30, 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 under 1 million and 2 million for the three and six months ended June 30, 2016 . Refer to Note 20 — Shareholders' Equity of the Exelon 2016 Form 10-K for further information regarding the equity units. On June 1, 2017, Exelon settled the forward purchase contract, which was a component of the June 2014 equity units, through the issuance of approximately 33 million shares of Exelon common stock from treasury stock. The issuance of shares on June 1, 2017, triggered full dilution in the EPS calculation, which prior to settlement were included in the calculation of diluted EPS using the treasury stock method. Prior to the June 2017 issuance Exelon had approximately 35 million shares of treasury stock with a cost of $2.3 billion . After issuance, Exelon has approximately 2 million shares of Treasury stock remaining, at a historical cost of $123 million . In 2008, Exelon management decided to defer indefinitely any share repurchases.

Commitments and Contingencies (

Commitments and Contingencies (All Registrants)	6 Months Ended
	Jun. 30, 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 includes the construction of a new 21-story headquarters building in Baltimore for Generation’s competitive energy business that was substantially complete in November 2016 and is now occupied by approximately 1,500 Exelon employees. Generation’s investment includes leasehold improvements that are not expected to exceed $110 million . In addition, Generation entered into a 20 year operating lease as the primary lessee of the building. 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 Generation’s future minimum lease payments. The direct investment commitment also includes $ 450 million to $ 500 million relating to Exelon and Generation’s development or assistance in the development of 285-300 MWs of new generation in Maryland, which is expected to be completed within a period of 10 years. The MDPSC order contemplates various options for complying with the new generation development commitments, including building or acquiring generating assets, making subsidy or compliance payments, or in circumstances in which the generation build is delayed or certain specified provisions are elected, making liquidated damages payments. Exelon and Generation have incurred $ 457 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 and an additional 10 MW commitment satisfied through a liquidated damages payment made in the fourth quarter of 2016. Additionally, 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 June 30, 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 (remainder of year) $ 8 2018 7 2019 3 Total $ 18 Commercial Commitments (All Registrants) The Registrants’ commercial commitments as of June 30, 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) $ 1,326 $ 1,243 $ 14 $ 23 $ 2 $ 1 $ 1 $ — $ — Surety bonds (b) 1,113 1,014 12 18 11 21 13 4 4 Financing trust guarantees 628 — 200 178 250 — — — — Guaranteed lease residual values (c) 19 — — — — 19 6 7 5 Total commercial commitments $ 3,086 $ 2,257 $ 226 $ 219 $ 263 $ 41 $ 20 $ 11 $ 9 ________ (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, $18 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 June 30, 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 $ 360 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, 19 of which the remediation has been completed and approved by the Illinois EPA or the U.S. EPA and 23 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 of the 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. In May 2017, BGE completed the additional work requested by MDE. All the sample testing produced results that were below the cleanup action level established by MDE and no further investigation is required. 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 June 30, 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: June 30, 2017 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 412 $ 315 Generation 67 — ComEd 284 282 PECO 32 31 BGE 3 2 PHI (Successor) 26 — Pepco 23 — 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. On May 19, 2017, the Consent Decree was entered with the Court and became final. The Civil Penalty assessed under the Consent Decree of $ 1.6 million was paid on June 5, 2017 and other requirements of the Decree are now being implemented. 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. The EPA has advised the PRPs that the EPA announcement of the proposed remedy will take place in 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 2018 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. 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. In July, 2017 the PRPs and EPA finalized the terms of a Consent Decree which is being executed by the Parties and will then be lodged with the Court and subject to a 30-day public comment period after which it is anticipated it will be approved by the Court without any significant change in the costs for cleanup. There will also be an ancillary agreement between the PRP’s who will be performing the remedy and those who have elected to enter into cash settlements and become non-performing parties. Generation has elected to be a non-performing party and the settlement terms will provide contribution and all other protections against the performing parties. Generation has reached a preliminary settlement agreement for its share of the estimated clean-up costs, which is included in the table above and is immaterial to the Generation and Exelon financial statements. 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 $2 million which has been fully reserved and included in the table above as of June 30, 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. Although the ultimate outcome of this proceeding is uncertain based on the information complied to date, BGE has developed an estimate of the range of BGE’s probable liability and has established an appropriate accrual that is included it in the table above. It is possible, however, that final resolution of this matter could have a material, unfavorable impact on BGE’s future results of operations and cash flows. 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 in May 2017 BGE completed the additional work requested by MDE. All the sample testing produced results that were below the cleanup action level established by MDE and no further investigation is required. 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. Additionally, legislation was passed during the 2017 Maryland General Assembly session that should further support BGE’s recovery of its clean-up costs. 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 Remediation Investigation (RI)/ Feasibility Study (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

Supplemental Financial Informat

Supplemental Financial Information (All Registrants)	6 Months Ended
	Jun. 30, 2017
Supplemental Financial Information [Abstract]
Supplemental Financial Information (All Registrants)	Supplemental Financial Information (All Registrants) Supplemental Statement of Operations Information The following tables provide additional information about the Registrants’ Consolidated Statements of Operations and Comprehensive Income for the three and six months ended June 30, 2017 and 2016 . Three Months Ended June 30, 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 $ 211 $ 211 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 74 74 — — — — — — — Net unrealized (losses) gains on decommissioning trust funds Regulatory agreement units (13 ) (13 ) — — — — — — — Non-regulatory agreement units 70 70 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (2 ) (2 ) — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (160 ) (160 ) — — — — — — — Total decommissioning-related activities 180 180 — — — — — — — Investment income 2 1 — — — — — — — Interest expense related to uncertain income tax positions (1 ) — — — — — — — — Penalty related to uncertain income tax positions 1 — — — — — — — — AFUDC — Equity 17 — 2 2 4 9 5 2 2 Other 6 — 2 — — 4 2 1 — Other, net $ 205 $ 181 $ 4 $ 2 $ 4 $ 13 $ 7 $ 3 $ 2 Six Months Ended June 30, 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 $ 280 $ 280 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 106 106 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 210 210 — — — — — — Non-regulatory agreement units 235 235 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (2 ) (2 ) — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (396 ) (396 ) — — — — — — — Total decommissioning-related activities 433 433 — — — — — — — Investment income (expense) 4 3 — (1 ) — 1 1 — — Penalty income related to uncertain income tax positions 2 — — — — — — — — AFUDC — Equity 33 — 4 4 8 17 11 3 3 Other 16 4 4 — — 8 3 3 1 Other, net $ 488 $ 440 $ 8 $ 3 $ 8 $ 26 $ 15 $ 6 $ 4 Three Months Ended June 30, 2016 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 $ 90 $ 90 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 39 39 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 52 52 — — — — — — — Non-regulatory agreement units 48 48 — — — — — — — Net unrealized gains on pledged assets Zion Station decommissioning 1 1 — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (117 ) (117 ) — — — — — — — Total decommissioning-related activities 113 113 — — — — — — — Investment income 6 5 — — — — — — — Interest income related to uncertain income tax positions 4 — — — — — — — — AFUDC — Equity 15 — 1 2 5 7 5 1 1 Other 6 (1 ) 2 — — 4 1 2 1 Other, net $ 144 $ 117 $ 3 $ 2 $ 5 $ 11 $ 6 $ 3 $ 2 Successor Predecessor Six Months Ended June 30, 2016 March 24, 2016 to June 30, 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 $ 122 $ 122 $ — $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 61 61 — — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 131 131 — — — — — — — — Non-regulatory agreement units 100 100 — — — — — — — — Net unrealized gains on pledged assets Zion Station decommissioning 3 3 — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (211 ) (211 ) — — — — — — — — Total decommissioning-related activities 206 206 — — — — — — — — Investment income (expense) 12 5 — (1 ) 2 — — — — — Long-term lease income 4 — — — — — — — — — Interest income related to uncertain income tax positions 5 — — — — 1 — 1 — — AFUDC — Equity 24 — 3 4 9 9 2 3 8 7 Loss on debt extinguishment (3 ) (2 ) — — — — — — — — Other 10 1 4 1 — 4 4 1 4 (11 ) Other, net $ 258 $ 210 $ 7 $ 4 $ 11 $ 14 $ 6 $ 5 $ 12 $ (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 and six months ended June 30, 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 June 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 213 $ 30 $ 57 $ 29 $ 21 $ 76 $ 72 $ 4 $ — Six Months Ended June 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 438 $ 63 $ 116 $ 60 $ 47 $ 152 $ 143 $ 9 $ — Three Months Ended June 30, 2016 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 217 $ 27 $ 60 $ 32 $ 21 $ 77 $ 73 $ 4 $ — Successor Predecessor Six Months Ended June 30, 2016 March 24, 2016 to June 30, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Utility taxes $ 369 $ 55 $ 119 $ 66 $ 45 $ 152 $ 9 $ — $ 84 $ 77 Supplemental Cash Flow Information The following tables provide additional information regarding the Registrants’ Consolidated Statements of Cash Flows for the six months ended June 30, 2017 and 2016 . Six Months Ended June 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Depreciation, amortization and accretion Property, plant and equipment (a) $ 1,545 $ 612 $ 384 $ 129 $ 155 $ 227 $ 101 $ 61 $ 44 Amortization of regulatory assets (a) 238 — 35 12 84 105 59 18 28 Amortization of intangible assets, net (a) 28 25 — — — — — — — Amortization of energy contract assets and liabilities (b) 20 20 — — — — — — — Nuclear fuel (c) 529 529 — — — — — — — ARO accretion (d) 231 229 — — — — — — — Total depreciation, amortization and accretion $ 2,591 $ 1,415 $ 419 $ 141 $ 239 $ 332 $ 160 $ 79 $ 72 Successor Predecessor Six Months Ended June 30, 2016 March 24, 2016 to June 30, 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) $ 1,432 $ 674 $ 345 $ 121 $ 150 $ 85 $ 55 $ 40 $ 111 $ 94 Amortization of regulatory assets (a) 166 — 34 13 56 59 21 41 63 58 Amortization of intangible assets, net (a) 28 23 — — — — — — — — Amortization of energy contract assets and liabilities (b) (7 ) (7 ) — — — — — — — — Nuclear fuel (c) 557 557 — — — — — — — — ARO accretion (d) 220 220 — — — — — — — — Total depreciation, amortization and accretion $ 2,396 $ 1,467 $ 379 $ 134 $ 206 $ 144 $ 76 $ 81 $ 174 $ 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. Six Months Ended June 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 320 $ 113 $ 87 $ 14 $ 31 $ 48 $ 13 $ 6 $ 7 Loss from equity method investments 19 19 — — — — — — — Provision for uncollectible accounts 52 19 15 9 3 6 4 — 2 Stock-based compensation costs 57 — — — — — — — — Other decommissioning-related activity (a) (144 ) (144 ) — — — — — — — Energy-related options (b) 11 11 — — — — — — — Amortization of regulatory asset related to debt costs 4 — 2 — — 2 1 1 — Amortization of rate stabilization deferral (8 ) — — — 7 (15 ) (10 ) (5 ) — Amortization of debt fair value adjustment (9 ) (6 ) — — — (3 ) — — — Discrete impacts from EIMA and FEJA (c) (51 ) — (51 ) — — — — — — Amortization of debt costs 49 30 2 1 1 — — — — Provision for excess and obsolete inventory 51 49 1 — — 1 — — — Merger-related commitments (d) — — — — — (8 ) (6 ) (2 ) — Severance costs 25 17 — — — 3 — — — Other 39 13 2 (2 ) (7 ) (6 ) (2 ) (3 ) (2 ) Total other non-cash operating activities $ 415 $ 121 $ 58 $ 22 $ 35 $ 28 $ — $ (3 ) $ 7 Non-cash investing and financing activities: Change in capital expenditures not paid $ (105 ) $ 48 $ (82 ) $ (44 ) $ 6 $ (8 ) $ — $ 15 $ (14 ) Fair value of pension obligation transferred in connection with the FitzPatrick acquisition — 49 — — — — — — — Change in PPE related to ARO update 103 103 — — — — — — — Indemnification of like-kind exchange position (g) — — 23 — — — — — — Non-cash financing of capital projects 13 13 — — — — — — — Dividends on stock compensation 3 — — — — — — — — — Loss on reissuance of treasury stock 1,054 — — — — — — — — Successor Predecessor Six Months Ended June 30, 2016 March 24, 2016 to June 30, 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 $ 297 $ 109 $ 83 $ 17 $ 33 $ 16 $ 9 $ 8 $ 31 $ 23 Loss from equity method investments 10 11 — — — — — — — — Provision for uncollectible accounts 51 13 18 10 3 8 8 10 7 16 Stock-based compensation costs 67 — — — — — — — — 3 Other decommissioning-related activity (a) (123 ) (123 ) — — — — — — — — Energy-related options (b) (17 ) (17 ) — — — — — — — — Amortization of regulatory asset related to debt costs 4 — 2 1 — 1 — — 1 1 Amortization of rate stabilization deferral 34 — — — 34 (2 ) 2 — — 5 Amortization of debt fair value adjustment (6 ) (6 ) — — — — — — — — Discrete impacts from EIMA (c) (21 ) — (21 ) — — — — — — — Amortization of debt costs 14 10 2 1 2 — — — — — Provision for excess and obsolete inventory 68 66 2 — — 1 1 1 — 1 Merger-related commitments (d)(e) 503 3 — — — 138 100 120 358 — Severance costs 122 50 — — — — — — 54 — Asset retirement costs — — — — — — 4 2 — — Lower of cost or net realizable value inventory adjustment 36 36 — — — — — — — — Other 17 17 (3 ) (2 ) (12 ) (4 ) (3 ) (3 ) (7 ) (3 ) Total other non-cash operating activities $ 1,056 $ 169 $ 83 $ 27 $ 60 $ 158 $ 121 $ 138 $ 444 $ 46 Non-cash investing and financing activities: Change in capital expenditures not paid $ (364 ) $ (317 ) $ (21 ) $ (12 ) $ 2 $ 11 $ (9 ) $ 6 $ (4 ) $ 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 — — — — — — — — 53 — Assumption of member purchase liability — — — — — — — — 29 — Assumption of merger commitment liability — — — — — 33 — — 33 — Change in PPE related to ARO update 471 471 — — — — — — — — Indemnification of like-kind exchange position (g) — — 5 — — — — — — — Non-cash financing of capital projects 60 60 — — — — — — — — Dividends on stock compensation 2 — — — — — — — — — ________ (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 and FEJA, which allows for the recovery of distribution costs by a utility through a pre-established performance-based formula rate tariff. Beginning June 1, 2017, also reflects the change in energy efficiency rates pursuant to FEJA, which allows for the recovery of energy efficiency 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 June 30, 2017 and December 31, 2016 . Successor June 30, 2017 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Property, plant and equipment: Accumulated depreciation and amortization $ 19,735 (a) $ 10,550 (a) $ 4,122 $ 3,330 $ 3,358 $ 360 $ 3,131 $ 1,212 $ 1,042 Accounts receivable: Allowance for uncollectible accounts $ 322 $ 102 $ 71 $ 59 $ 26 $ 64 $ 25 $ 19 $ 20 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 $3,016 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 $11 million and $9 million as of June 30, 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 June 30, 2017 of $13 million consists of $1 million , $3 million and $9 million for low risk, medium risk and high risk segments, respectively. The allowance for uncollectible accounts balance 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 June 30, 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)	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Segment Information (All Registrants)	Segment Information (All Registrants) Operating segments for each of the Registrants are determined based on information used by the chief operating decision maker(s) (CODM) in deciding how to evaluate performance and allocate resources at each of the Registrants. In the first quarter of 2016, following the consummation of the PHI Merger, three new reportable segments were added: Pepco, DPL and ACE. As a result, Exelon has twelve reportable segments, which include ComEd, PECO, BGE, PHI's three reportable segments consisting of Pepco, DPL, and ACE, and Generation’s six reportable segments consisting of the Mid-Atlantic, Midwest, New England, New York, ERCOT and all other power regions referred to collectively as “Other Power Regions”, which includes activities in the South, West and Canada. ComEd, PECO, BGE, Pepco, DPL and ACE each represent a single reportable segment, and as such, no separate segment information is provided for these Registrants. Exelon, ComEd, PECO, BGE, Pepco, DPL and ACE's CODMs evaluate the performance of and allocate resources to ComEd, PECO, BGE, Pepco, DPL and ACE based on net income and return on equity. Effective with the consummation of the PHI Merger, PHI's reportable segments have changed based on the information used by the CODM to evaluate performance and allocate resources. PHI's reportable segments consist of Pepco, DPL and ACE. PHI's Predecessor periods' segment information has been recast to conform to the current presentation. The reclassification of the segment information did not impact PHI's reported consolidated revenues or net income. PHI's CODM evaluates the performance of and allocates resources to Pepco, DPL and ACE based on net income and return on equity. The basis for Generation's reportable segments is the integrated management of its electricity business that is located in different geographic regions, and largely representative of the footprints of ISO/RTO and/or NERC regions, which utilize multiple supply sources to provide electricity through various distribution channels (wholesale and retail). Generation's hedging strategies and risk metrics are also aligned to these same geographic regions. Descriptions of each of Generation’s six reportable segments are as follows: • Mid-Atlantic represents operations in the eastern half of PJM, which includes New Jersey, Maryland, Virginia, West Virginia, Delaware, the District of Columbia and parts of Pennsylvania and North Carolina. • Midwest represents operations in the western half of PJM, which includes portions of Illinois, Pennsylvania, Indiana, Ohio, Michigan, Kentucky and Tennessee, and the United States footprint of MISO, excluding MISO’s Southern Region, which covers all or most of North Dakota, South Dakota, Nebraska, Minnesota, Iowa, Wisconsin, the remaining parts of Illinois, Indiana, Michigan and Ohio not covered by PJM, and parts of Montana, Missouri and Kentucky. • New England represents the operations within ISO-NE covering the states of Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont. • New York represents operations within ISO-NY, which covers the state of New York in its entirety. • ERCOT represents operations within Electric Reliability Council of Texas, covering most of the state of Texas. • Other Power Regions : • South represents operations in the FRCC, MISO’s Southern Region, and the remaining portions of the SERC not included within MISO or PJM, which includes all or most of Florida, Arkansas, Louisiana, Mississippi, Alabama, Georgia, Tennessee, North Carolina, South Carolina and parts of Missouri, Kentucky and Texas. Generation’s South region also includes operations in the SPP, covering Kansas, Oklahoma, most of Nebraska and parts of New Mexico, Texas, Louisiana, Missouri, Mississippi and Arkansas. • West represents operations in the WECC, which includes California ISO, and covers the states of California, Oregon, Washington, Arizona, Nevada, Utah, Idaho, Colorado and parts of New Mexico, Wyoming and South Dakota. • Canada represents operations across the entire country of Canada and includes AESO, OIESO and the Canadian portion of MISO. The CODMs for Exelon and Generation evaluate the performance of Generation’s electric business activities and allocate resources based on revenues net of purchased power and fuel expense (RNF). Generation believes that RNF is a useful measurement of operational performance. RNF is not a presentation defined under GAAP and may not be comparable to other companies’ presentations or deemed more useful than the GAAP information provided elsewhere in this report. Generation’s operating revenues include all sales to third parties and affiliated sales to the Utility Registrants. Purchased power costs include all costs associated with the procurement and supply of electricity including capacity, energy and ancillary services. Fuel expense includes the fuel costs for Generation’s owned generation and fuel costs associated with tolling agreements. The results of Generation's other business activities are not regularly reviewed by the CODM and are therefore not classified as operating segments or included in the regional reportable segment amounts. These activities include natural gas, as well as other miscellaneous business activities that are not significant to Generation's overall operating revenues or results of operations. Further, Generation’s unrealized mark-to-market gains and losses on economic hedging activities and its amortization of certain intangible assets and liabilities relating to commodity contracts recorded at fair value from mergers and acquisitions are also excluded from the regional reportable segment amounts. Exelon and Generation do not use a measure of total assets in making decisions regarding allocating resources to or assessing the performance of these reportable segments. An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements for the three and six months ended June 30, 2017 and 2016 is as follows: Three Months Ended June 30, 2017 and 2016 Successor Generation (a) ComEd PECO BGE PHI (b) Other (c) Intersegment Exelon Operating revenues (d) : 2017 Competitive businesses electric revenues $ 3,719 $ — $ — $ — $ — $ — $ (266 ) $ 3,453 Competitive businesses natural gas revenues 430 — — — — — — 430 Competitive businesses other revenues 25 — — — — — — 25 Rate-regulated electric revenues — 1,357 550 571 1,040 — (7 ) 3,511 Rate-regulated natural gas revenues — — 80 103 22 — (1 ) 204 Shared service and other revenues — — — — 12 449 (461 ) — 2016 Competitive businesses electric revenues $ 3,655 $ — $ — $ — $ — $ — $ (354 ) $ 3,301 Competitive businesses natural gas revenues 367 — — — — — — 367 Competitive businesses other revenues (433 ) — — — — — (1 ) (434 ) Rate-regulated electric revenues — 1,286 587 584 1,030 — (7 ) 3,480 Rate-regulated natural gas revenues — — 77 96 26 — (2 ) 197 Shared service and other revenues — — — — 10 398 (409 ) (1 ) Intersegment revenues (e) : 2017 $ 266 $ 3 $ 2 $ 3 $ 12 $ 448 $ (734 ) $ — 2016 355 3 2 4 10 398 (771 ) 1 Net income (loss): 2017 $ (266 ) $ 118 $ 88 $ 45 $ 66 $ 13 $ — $ 64 2016 28 145 100 34 52 (52 ) (1 ) 306 Total assets: June 30, 2017 $ 48,130 $ 29,160 $ 11,041 $ 8,786 $ 21,190 $ 10,783 $ (11,986 ) $ 117,104 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 June 30, 2017 include revenue from sales to PECO of $34 million , sales to BGE of $99 million , sales to Pepco of $68 million , sales to DPL of $40 million , and sales to ACE of $7 million in the Mid-Atlantic region, and sales to ComEd of $18 million in the Midwest region. For the three months ended June 30, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $64 million , sales to BGE of $135 million , sales to Pepco of $88 million , sales to DPL of $43 million , and sales to ACE of $12 million in the Mid-Atlantic region, and sales to ComEd of $13 million in the Midwest region. (b) Amounts included represent activity for PHI's successor period, three months ended June 30, 2017 and 2016 . PHI includes the three reportable segments: Pepco, DPL and ACE. (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 June 30, 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 PHI: Pepco DPL ACE Other (b) Intersegment PHI Operating revenues (a) : Three months ended June 30, 2017 - Successor Rate-regulated electric revenues $ 514 $ 260 $ 270 $ — $ (4 ) $ 1,040 Rate-regulated natural gas revenues — 22 — — — 22 Shared service and other revenues — — — 13 (1 ) 12 Three months ended June 30, 2016 - Successor Rate-regulated electric revenues $ 509 $ 255 $ 270 $ — $ (4 ) $ 1,030 Rate-regulated natural gas revenues — 26 — — — 26 Shared service and other revenues — — — 10 — 10 Intersegment revenues: Three months ended June 30, 2017 - Successor $ 1 $ 2 $ 1 $ 13 $ (5 ) $ 12 Three months ended June 30, 2016 - Successor 1 2 1 10 (4 ) 10 Net income (loss): Three months ended June 30, 2017 - Successor $ 43 $ 19 $ 8 $ (16 ) $ 12 $ 66 Three months ended June 30, 2016 - Successor 49 12 3 (22 ) 10 52 Total assets: June 30, 2017 - Successor $ 7,648 $ 4,235 $ 3,478 $ 10,800 $ (4,971 ) $ 21,190 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 June 30, 2017 and 2016 . (b) Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities. Generation total revenues: Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Revenues (a) Intersegment Total Revenues (a) Intersegment Total Mid-Atlantic $ 1,356 $ 9 $ 1,365 $ 1,432 $ (16 ) $ 1,416 Midwest 1,058 (8 ) 1,050 1,076 7 1,083 New England 438 (5 ) 433 352 (1 ) 351 New York 352 (5 ) 347 356 (10 ) 346 ERCOT 247 — 247 207 — 207 Other Power Regions 268 (9 ) 259 232 (9 ) 223 Total Revenues for Reportable Segments 3,719 (18 ) 3,701 3,655 (29 ) 3,626 Other (b) 455 18 473 (66 ) 29 (37 ) Total Generation Consolidated Operating Revenues $ 4,174 $ — $ 4,174 $ 3,589 $ — $ 3,589 _ _________ (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 $15 million and $9 million decrease to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the three months ended June 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $143 million and $615 million for the three months ended June 30, 2017 and 2016 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 RNF (a) Intersegment RNF Total RNF RNF (a) Intersegment RNF Total RNF Mid-Atlantic $ 757 $ 26 $ 783 $ 830 $ (2 ) $ 828 Midwest 728 — 728 724 4 728 New England 157 (10 ) 147 118 (8 ) 110 New York 230 — 230 270 (3 ) 267 ERCOT 121 (51 ) 70 111 (34 ) 77 Other Power Regions 134 (44 ) 90 123 (27 ) 96 Total Revenues net of purchased power and fuel for Reportable Segments 2,127 (79 ) 2,048 2,176 (70 ) 2,106 Other (b) (110 ) 79 (31 ) (164 ) 70 (94 ) Total Generation Revenues net of purchased power and fuel expense $ 2,017 $ — $ 2,017 $ 2,012 $ — $ 2,012 __________ (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 $20 million and $12 million decrease to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the three months ended June 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $184 million and $304 million for the three months ended June 30, 2017 and 2016 , respectively, and the elimination of intersegment revenue net of purchased power and fuel expense. Six Months Ended June 30, 2017 and 2016 Successor Generation (a) ComEd PECO BGE PHI (b) Other (c) Intersegment Exelon Operating revenues (d) : 2017 Competitive businesses electric revenues $ 7,437 $ — $ — $ — $ — $ — $ (592 ) $ 6,845 Competitive businesses natural gas revenues 1,348 — — — — — — 1,348 Competitive businesses other revenues 276 — — — — — (1 ) 275 Rate-regulated electric revenues — 2,656 1,140 1,237 2,138 1 (16 ) 7,156 Rate-regulated natural gas revenues — — 286 388 87 — (4 ) 757 Shared service and other revenues — — — — 23 870 (893 ) — 2016 Competitive businesses electric revenues $ 7,352 $ — $ — $ — $ — $ — $ (620 ) $ 6,732 Competitive businesses natural gas revenues 1,189 — — — — — — 1,189 Competitive businesses other revenues (212 ) — — — — — (1 ) (213 ) Rate-regulated electric revenues — 2,535 1,232 1,264 1,120 — (15 ) 6,136 Rate-regulated natural gas revenues — — 273 345 28 — (5 ) 641 Shared service and other revenues — — — — 23 803 (826 ) — Intersegment revenues (e) : 2017 $ 594 $ 9 $ 3 $ 8 $ 23 $ 866 $ (1,503 ) $ — 2016 621 8 4 9 23 803 (1,466 ) 2 Net income (loss): 2017 $ 144 $ 259 $ 215 $ 169 $ 205 $ 54 $ — $ 1,046 2016 285 260 224 135 (257 ) (215 ) (2 ) 430 _________ (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 six months ended June 30, 2017 include revenue from sales to PECO of $79 million , sales to BGE of $233 million , sales to Pepco of $152 million , sales to DPL of $91 million , and sales to ACE of $16 million in the Mid-Atlantic region, and sales to ComEd of $23 million in the Midwest region. For the six months ended June 30, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $143 million and sales to BGE of $306 million in the Mid-Atlantic region, and sales to ComEd of $18 million in the Midwest region. For the Successor period of March 24, 2016 to June 30, 2016 , intersegment revenues for Generation include revenue from sales to Pepco of $94 million , sales to DPL of $47 million , and sales to ACE of $13 million in the Mid-Atlantic region. (b) Amounts included represent activity for PHI's successor period, six months ended June 30, 2017 and March 24, 2016 through June 30, 2016 . PHI includes the three reportable segments: Pepco, DPL and ACE. See tables below for PHI's predecessor period, including Pepco, DPL and ACE, for January 1, 2016 to March 23, 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 six months ended June 30, 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) : Six Months Ended June 30, 2017 - Successor Rate-regulated electric revenues $ 1,045 $ 557 $ 544 $ 1 $ (9 ) $ 2,138 Rate-regulated natural gas revenues — 87 — — — 87 Shared service and other revenues — — — 25 (2 ) 23 March 24, 2016 to June 30, 2016 - Successor Rate-regulated electric revenues $ 550 $ 279 $ 293 $ 3 $ (5 ) $ 1,120 Rate-regulated natural gas revenues — 29 — (1 ) — 28 Shared service and other revenues — — — 23 — 23 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: Six Months Ended June 30, 2017 - Successor $ 3 $ 4 $ 1 $ 24 $ (9 ) $ 23 March 24, 2016 to June 30, 2016 - Successor 2 2 1 23 (5 ) 23 January 1, 2016 to March 23, 2016 - Predecessor 1 2 1 — (4 ) — Net income (loss): Six Months Ended June 30, 2017 - Successor $ 101 $ 76 $ 36 $ (31 ) $ 23 $ 205 March 24, 2016 to June 30, 2016 - Successor (92 ) (86 ) (102 ) — 23 (257 ) January 1, 2016 to March 23, 2016 - Predecessor 32 26 5 (44 ) — 19 _________ (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 six months ended June 30, 2017 and 2016 . (b) Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities. For the predecessor period 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: Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 Revenues (a) Intersegment Total Revenues (a) Intersegment Total Mid-Atlantic $ 2,785 $ 5 $ 2,790 $ 2,964 $ (28 ) $ 2,936 Midwest 2,107 (5 ) 2,102 2,166 13 2,179 New England 987 (7 ) 980 823 (2 ) 821 New York 662 (8 ) 654 573 (24 ) 549 ERCOT 439 (1 ) 438 370 — 370 Other Power Regions 457 (14 ) 443 456 (9 ) 447 Total Revenues for Reportable Segments 7,437 (30 ) 7,407 7,352 (50 ) 7,302 Other (b) 1,624 30 1,654 977 50 1,027 Total Generation Consolidated Operating Revenues $ 9,061 $ — $ 9,061 $ 8,329 $ — $ 8,329 _ _________ (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 $17 million decrease to revenues and an $11 million increase to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the six months ended June 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $98 million and $553 million for the six months ended June 30, 2017 and 2016 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 RNF from external customers (a) Intersegment RNF Total RNF RNF from external customers (a) Intersegment RN Total RNF Mid-Atlantic $ 1,513 $ 44 $ 1,557 $ 1,661 $ 8 $ 1,669 Midwest 1,431 12 1,443 1,443 6 1,449 New England 271 (14 ) 257 204 (13 ) 191 New York 385 — 385 408 (13 ) 395 ERCOT 214 (76 ) 138 192 (54 ) 138 Other Power Regions 240 (88 ) 152 211 (37 ) 174 Total Revenues net of purchased power and fuel expense for Reportable Segments 4,054 (122 ) 3,932 4,119 (103 ) 4,016 Other (b) 52 122 174 190 103 293 Total Generation Revenues net of purchased power and fuel expense $ 4,106 $ — $ 4,106 $ 4,309 $ — $ 4,309 __________ (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 $22 million decrease to RNF and a $7 million increase to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the six months ended June 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $233 million and $201 million for the six months ended June 30, 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)	6 Months Ended
	Jun. 30, 2017
Subsequent Events [Abstract]
Subsequent Events [Text Block]	On July 6, 2017, ExGen Renewables Holdings, LLC, a wholly owned subsidiary of Generation, completed the sale of a 49% interest of ExGen Renewables Partners, LLC, a newly formed owner and operator of approximately 1,296 megawatts of Generation's operating wind and solar electric generating facilities. ExGen Renewables Holdings will be the managing member of ExGen Renewables Partners, LLC, and have day-to-day control and management over its renewable generation portfolio. The closing of the transaction was subject to certain regulatory approvals, including the Federal Energy Regulatory Commission (FERC) and the Public Utility Commission of Texas (PUCT) which were received during the second quarter of 2017. The sale price was $400 million plus immaterial working capital and other customary post-closing adjustments. The net proceeds, after approximately $120 million of income taxes, will be used to pay down debt and for general corporate purposes. Generation will continue to consolidate ExGen Renewables Partners, LLC and will record a noncontrolling interest on its Consolidated Balance Sheet for the investor's initial equity share as well as earnings attributable to the noncontrolling interest in the Consolidated Statements of Operations and Comprehensive Income each period going forward.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 are as follows: June 30, 2017 December 31, 2016 Successor Successor Exelon (a) Generation PHI (a) ACE Exelon (a)(b) Generation BGE PHI (a) ACE Current assets $ 512 $ 501 $ 11 $ 7 $ 954 $ 916 $ 23 $ 14 $ 9 Noncurrent assets 8,617 8,585 32 23 8,563 8,525 3 35 23 Total assets $ 9,129 $ 9,086 $ 43 $ 30 $ 9,517 $ 9,441 $ 26 $ 49 $ 32 Current liabilities $ 573 $ 535 $ 38 $ 34 $ 885 $ 802 $ 42 $ 42 $ 37 Noncurrent liabilities 2,723 2,640 83 74 2,713 2,612 — 101 89 Total liabilities $ 3,296 $ 3,175 $ 121 $ 108 $ 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. As of June 30, 2017 and December 31, 2016 , these assets and liabilities primarily consisted of the following: June 30, 2017 December 31, 2016 Successor Successor Exelon (a) Generation PHI (a) ACE Exelon (a)(b) Generation BGE PHI (a) ACE Cash and cash equivalents $ 68 $ 68 $ — $ — $ 150 $ 150 $ — $ — $ — Restricted cash 55 48 7 7 59 27 23 9 9 Accounts receivable, net Customer 106 106 — — 371 371 — — — Other 24 24 — — 48 48 — — — Mark-to-market derivatives assets — — — — 31 31 — — — Inventory Materials and supplies 193 193 — — 199 199 — — — Other current assets 38 34 4 — 50 44 — 5 — Total current assets 484 473 11 7 908 870 23 14 9 Property, plant and equipment, net 5,293 5,293 — — 5,415 5,415 — — — Nuclear decommissioning trust funds 2,341 2,341 — — 2,185 2,185 — — — Goodwill — — — — 47 47 — — — Mark-to-market derivative assets — — — — 23 23 — — — Other noncurrent assets 267 235 32 23 315 277 3 35 23 Total noncurrent assets 7,901 7,869 32 23 7,985 7,947 3 35 23 Total assets $ 8,385 $ 8,342 $ 43 $ 30 $ 8,893 $ 8,817 $ 26 $ 49 $ 32 Long-term debt due within one year $ 191 $ 154 $ 37 $ 33 $ 181 $ 99 $ 41 $ 40 $ 35 Accounts payable 80 80 — — 269 269 — — — Accrued expenses 48 47 1 1 119 116 1 2 2 Mark-to-market derivative liabilities — — — — 60 60 — — — Unamortized energy contract liabilities 16 16 — — 15 15 — — — Other current liabilities 5 5 — — 30 30 — — — Total current liabilities 340 302 38 34 674 589 42 42 37 Long-term debt 616 533 83 74 641 540 — 101 89 Asset retirement obligations 1,954 1,954 — — 1,904 1,904 — — — Pension obligation (c) — — — — 9 9 — — — Unamortized energy contract liabilities 13 13 — — 22 22 — — — Other noncurrent liabilities 98 98 — — 106 106 — — — Total noncurrent liabilities 2,681 2,598 83 74 2,682 2,581 — 101 89 Total liabilities $ 3,021 $ 2,900 $ 121 $ 108 $ 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. The following tables present summary information about Exelon's and Generation’s significant unconsolidated VIE entities: June 30, 2017 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 641 $ 529 $ 1,170 Total liabilities (a) 64 229 293 Exelon's ownership interest in VIE (a) — 268 268 Other ownership interests in VIE (a) 577 32 609 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 268 268 Contract intangible asset 9 — 9 Debt and payment guarantees — — — Net assets pledged for Zion Station decommissioning (b) 6 — 6 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 $75 million and $113 million as of June 30, 2017 and December 31, 2016 , respectively; offset by payables to ZionSolutions LLC of $69 million and $104 million as of June 30, 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)	6 Months Ended
	Jun. 30, 2017
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	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. 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 June 30, 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.
Business Combination, Separately Recognized Transactions [Table Text Block]	Three Months Ended June 30, Six Months Ended June 30, Acquisition, Integration and Financing Costs (a) 2017 2016 2017 2016 Exelon (b) $ 8 $ 1 $ 17 $ 103 Generation 4 4 13 20 ComEd (c) — 1 1 (7 ) PECO 1 1 2 2 BGE (d) 1 (5 ) 2 (4 ) Pepco (e) 1 (4 ) 2 23 DPL (f) — — (7 ) 16 ACE 1 2 2 15 Successor Predecessor Acquisition, Integration and Financing Costs (a) Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Six Months Ended June 30, 2017 March 24, 2016 to June 30, 2016 January 1, 2016 to March 23, 2016 PHI (g) $ 2 $ (1 ) $ (2 ) $ 55 $ 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 six months ended June 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 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 and six months ended June 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $6 million incurred at BGE that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. (e) For the three and six months ended June 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $9 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. (f) For the six months ended June 30, 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. For the three and six months ended June 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $3 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. (g) For the six months ended June 30, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. For the three months ended June 30, 2016 and the Successor period March 24, 2016 to June 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $12 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. Expected Payment Period Successor Description Pepco DPL ACE PHI Exelon Rate credits 2016 - 2017 $ 91 $ 67 $ 101 $ 259 $ 259 Energy efficiency 2016 - 2021 — — — — 122 Charitable contributions 2016 - 2026 28 12 10 50 50 Delivery system modernization Q2 2017 — — — — 22 Green sustainability fund Q2 2017 — — — — 14 Workforce development 2016 - 2020 — — — — 17 Other 1 5 — 6 29 Total $ 120 $ 84 $ 111 $ 315 $ 513 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 180 Cash paid for PHI stock-based compensation equity awards (a) 29 Total purchase price $ 7,142 _____________ (a) PHI’s unvested time-based restricted stock units and performance-based restricted stock units issued prior to April 29, 2014 were immediately vested and paid in cash upon the close of the merger. PHI’s remaining unvested time-based restricted stock units as of the close of the merger were cancelled. There were no remaining unvested performance-based restricted stock units as of the close of the merger. The current impact of PHI, including its unregulated businesses, on Exelon's Consolidated Statements of Operations and Comprehensive Income includes: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Operating revenues $ 1,113 $ 1,112 $ 2,332 $ 1,219 Net income (loss) 61 52 202 (262 )
Business Acquisition, Pro Forma Information, Nonrecurring Adjustments [Table Text Block]	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 Six Months Ended Year Ended December 31, 2016 (a) 2016 (a) 2016 (b) Total operating revenues $ 6,910 $ 15,466 $ 32,342 Net income attributable to common shareholders 268 845 1,562 Basic earnings per share $ 0.29 $ 0.92 $ 1.69 Diluted earnings per share 0.29 0.91 1.69 ______________ (a) The amounts above include adjustments for non-recurring costs directly related to the merger of $1 million and $641 million for the three and six months ended June 30, 2016 , respectively, and intercompany revenue of $170 million for the six months ended June 30, 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 (Tables)

Regulatory Matters (Tables)	6 Months Ended
	Jun. 30, 2017
Regulated Operations [Abstract]
Public Utilities General Disclosures [Table Text Block]	The following total increases/(decreases) were included in ComEd’s, BGE’s, Pepco's, DPL's and ACE's electric transmission formula rate filings: 2017 Annual Transmission Filings (a) ComEd BGE Pepco DPL ACE Initial revenue requirement increase $ 44 $ 31 $ 5 $ 6 $ 20 Annual reconciliation (decrease) increase (33 ) 3 15 8 22 Dedicated facilities decrease (b) — (8 ) — — — Total revenue requirement increase $ 11 $ 26 $ 20 $ 14 $ 42 Allowed return on rate base (c) 8.43 % 7.47 % 7.92 % 7.16 % 8.02 % Allowed ROE (d) 11.50 % 10.50 % 10.50 % 10.50 % 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, Pepco, DPL and ACE, the rate of return on common equity is 10.50% , inclusive of a 50 basis point incentive adder for being a member of a regional transmission organization. Exelon ComEd (a) PECO BGE (b) PHI Pepco (c) DPL (c) ACE June 30, 2017 $ 71 $ 6 $ — $ 55 $ 10 $ 6 $ 4 $ — Exelon ComEd (a) PECO BGE (b) PHI Pepco (c) DPL (c) 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 relate to earnings on shareholders' investment on its AMI Programs.
Schedule of Regulatory Assets	The following tables provide information about the regulatory assets and liabilities of Exelon, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE as of June 30, 2017 and December 31, 2016 . For additional information on the specific regulatory assets and liabilities, refer to Note 3 — Regulatory Matters of the Exelon 2016 Form 10-K. Successor June 30, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory assets Pension and other postretirement benefits (a) $ 4,086 $ — $ — $ — $ — $ — $ — $ — Deferred income taxes (b) 2,091 76 1,645 100 270 176 41 53 AMI programs 679 163 43 225 248 167 81 — Under-recovered distribution service costs (c) 239 239 — — — — — — Energy efficiency costs 19 19 — — — — — — Debt costs 117 39 1 7 77 16 8 6 Fair value of long-term debt 782 — — — 645 — — — Fair value of PHI's unamortized energy contracts 918 — — — 918 — — — Severance 3 — — 3 — — — — Asset retirement obligations 119 84 23 12 — — — — MGP remediation costs 289 266 23 — — — — — Under-recovered uncollectible accounts 55 55 — — — — — — Renewable energy 258 256 — — 2 — 1 1 Energy and transmission programs (d)(e)(f)(g)(h)(i) 69 8 1 21 39 6 6 27 Deferred storm costs 34 — — — 34 10 6 18 Electric generation-related regulatory asset 5 — — 5 — — — — Energy efficiency and demand response programs 590 — 1 271 318 236 82 — Merger integration costs (j)(k) 32 — — 7 25 12 13 — Under-recovered revenue decoupling (l) 74 — — 35 39 31 8 — COPCO acquisition adjustment 6 — — — 6 — 6 — Workers compensation and long-term disability cost 34 — — — 34 34 — — Vacation accrual 47 — 22 — 25 — 15 10 Securitized stranded costs 108 — — — 108 — — 108 CAP arrearage 10 — 10 — — — — — Removal costs 500 — — — 500 138 95 268 Renewable portfolio standards costs 19 19 — — — — — — Other 55 8 9 6 32 21 8 4 Total regulatory assets 11,238 1,232 1,778 692 3,320 847 370 495 Less: current portion 1,293 182 46 197 605 165 71 89 Total non-current regulatory assets $ 9,945 $ 1,050 $ 1,732 $ 495 $ 2,715 $ 682 $ 299 $ 406 Successor June 30, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory liabilities Other postretirement benefits $ 43 $ — $ — $ — $ — $ — $ — $ — Nuclear decommissioning 2,870 2,364 506 — — — — — Removal costs 1,592 1,332 — 129 131 18 113 — Deferred rent 38 — — — 38 — — — Energy efficiency and demand response programs 128 88 39 — 1 1 — — DLC program costs 8 — 8 — — — — — Electric distribution tax repairs 59 — 59 — — — — — Gas distribution tax repairs 16 — 16 — — — — — Energy and transmission programs (d)(e)(f)(g)(h)(i) 123 40 61 — 22 2 12 8 Rate stabilization deferral 3 — — 3 — — — — Zero emission credit costs 22 22 — — — — — — Other 70 8 10 25 27 1 13 12 Total regulatory liabilities 4,972 3,854 699 157 219 22 138 20 Less: current portion 574 269 155 67 68 5 43 20 Total non-current regulatory liabilities $ 4,398 $ 3,585 $ 544 $ 90 $ 151 $ 17 $ 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 June 30, 2017 and December 31, 2016 , the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $1,025 million and $995 million , respectively, as a result 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 June 30, 2017 , includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $22 million , $41 million , $33 million , $22 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. On December 13, 2016, BGE filed with FERC to begin recovering these existing and any similar future regulatory assets through its transmission formula rate. On May 9, 2017, FERC accepted BGE’s filing and made effective BGE’s proposed modifications to its transmission formula rate, subject to refund and further Commission order. ComEd, Pepco, DPL, and ACE are expected to make similar filings with FERC and other parties in subsequent periods. (c) As of June 30, 2017 , ComEd’s regulatory asset of $239 million was comprised of $184 million for the 2015 - 2017 annual reconciliations and $55 million related to significant one-time events including $14 million of deferred storm costs, $9 million of Constellation and PHI merger and integration related costs, $3 million of emerald ash borer costs, and $29 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. See Note 4 — Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information. (d) As of June 30, 2017 , ComEd’s regulatory asset of $8 million reflects Constellation merger and integration costs to be recovered upon FERC approval. As of June 30, 2017 , ComEd’s regulatory liability of $40 million included $8 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 June 30, 2017 , PECO's regulatory asset of $1 million related to under-recovered electric transmission costs. As of June 30, 2017 , PECO's regulatory liability of $61 million included $36 million related to over-recovered costs under the DSP program, $16 million related to the over-recovered natural gas costs under the PGC and $9 million related to over-recovered non-bypassable transmission service charges. 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 June 30, 2017 , BGE's regulatory asset of $21 million included $10 million related to under-recovered electric energy costs, $5 million related to under-recovered natural gas costs, $4 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $2 million of abandonment costs to be recovered upon FERC approval. 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 June 30, 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 June 30, 2017 , Pepco's regulatory liability of $2 million related to 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 June 30, 2017 , DPL's regulatory asset of $6 million related to under-recovered electric energy costs. As of June 30, 2017 , DPL's regulatory liability of $12 million included $10 million of over-recovered electric energy 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 June 30, 2017 , ACE's regulatory asset of $27 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $16 million of under-recovered electric energy costs. As of June 30, 2017 , ACE's regulatory liability of $8 million related to 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 June 30, 2017 and December 31, 2016 , BGE's regulatory asset of $7 million and $10 million , respectively, included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order. (k) As of June 30, 2017 and December 31, 2016 , Pepco’s regulatory asset of $12 million and $11 million , respectively, represents previously incurred PHI acquisition costs authorized for recovery by the November 2016 Maryland distribution rate case order. As of June 30, 2017 , DPL’s regulatory asset of $13 million represents previously incurred PHI acquisition costs, including $4 million authorized for recovery by the February 2017 Maryland distribution rate case order, $6 million authorized for recovery by the May 2017 Delaware electric distribution rate case order, and $3 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 June 30, 2017 , BGE had a regulatory asset of $24 million related to under-recovered electric revenue decoupling and $11 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	The following tables provide information about the regulatory assets and liabilities of Exelon, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE as of June 30, 2017 and December 31, 2016 . For additional information on the specific regulatory assets and liabilities, refer to Note 3 — Regulatory Matters of the Exelon 2016 Form 10-K. Successor June 30, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory assets Pension and other postretirement benefits (a) $ 4,086 $ — $ — $ — $ — $ — $ — $ — Deferred income taxes (b) 2,091 76 1,645 100 270 176 41 53 AMI programs 679 163 43 225 248 167 81 — Under-recovered distribution service costs (c) 239 239 — — — — — — Energy efficiency costs 19 19 — — — — — — Debt costs 117 39 1 7 77 16 8 6 Fair value of long-term debt 782 — — — 645 — — — Fair value of PHI's unamortized energy contracts 918 — — — 918 — — — Severance 3 — — 3 — — — — Asset retirement obligations 119 84 23 12 — — — — MGP remediation costs 289 266 23 — — — — — Under-recovered uncollectible accounts 55 55 — — — — — — Renewable energy 258 256 — — 2 — 1 1 Energy and transmission programs (d)(e)(f)(g)(h)(i) 69 8 1 21 39 6 6 27 Deferred storm costs 34 — — — 34 10 6 18 Electric generation-related regulatory asset 5 — — 5 — — — — Energy efficiency and demand response programs 590 — 1 271 318 236 82 — Merger integration costs (j)(k) 32 — — 7 25 12 13 — Under-recovered revenue decoupling (l) 74 — — 35 39 31 8 — COPCO acquisition adjustment 6 — — — 6 — 6 — Workers compensation and long-term disability cost 34 — — — 34 34 — — Vacation accrual 47 — 22 — 25 — 15 10 Securitized stranded costs 108 — — — 108 — — 108 CAP arrearage 10 — 10 — — — — — Removal costs 500 — — — 500 138 95 268 Renewable portfolio standards costs 19 19 — — — — — — Other 55 8 9 6 32 21 8 4 Total regulatory assets 11,238 1,232 1,778 692 3,320 847 370 495 Less: current portion 1,293 182 46 197 605 165 71 89 Total non-current regulatory assets $ 9,945 $ 1,050 $ 1,732 $ 495 $ 2,715 $ 682 $ 299 $ 406 Successor June 30, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory liabilities Other postretirement benefits $ 43 $ — $ — $ — $ — $ — $ — $ — Nuclear decommissioning 2,870 2,364 506 — — — — — Removal costs 1,592 1,332 — 129 131 18 113 — Deferred rent 38 — — — 38 — — — Energy efficiency and demand response programs 128 88 39 — 1 1 — — DLC program costs 8 — 8 — — — — — Electric distribution tax repairs 59 — 59 — — — — — Gas distribution tax repairs 16 — 16 — — — — — Energy and transmission programs (d)(e)(f)(g)(h)(i) 123 40 61 — 22 2 12 8 Rate stabilization deferral 3 — — 3 — — — — Zero emission credit costs 22 22 — — — — — — Other 70 8 10 25 27 1 13 12 Total regulatory liabilities 4,972 3,854 699 157 219 22 138 20 Less: current portion 574 269 155 67 68 5 43 20 Total non-current regulatory liabilities $ 4,398 $ 3,585 $ 544 $ 90 $ 151 $ 17 $ 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 June 30, 2017 and December 31, 2016 , the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $1,025 million and $995 million , respectively, as a result 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 June 30, 2017 , includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $22 million , $41 million , $33 million , $22 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. On December 13, 2016, BGE filed with FERC to begin recovering these existing and any similar future regulatory assets through its transmission formula rate. On May 9, 2017, FERC accepted BGE’s filing and made effective BGE’s proposed modifications to its transmission formula rate, subject to refund and further Commission order. ComEd, Pepco, DPL, and ACE are expected to make similar filings with FERC and other parties in subsequent periods. (c) As of June 30, 2017 , ComEd’s regulatory asset of $239 million was comprised of $184 million for the 2015 - 2017 annual reconciliations and $55 million related to significant one-time events including $14 million of deferred storm costs, $9 million of Constellation and PHI merger and integration related costs, $3 million of emerald ash borer costs, and $29 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. See Note 4 — Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information. (d) As of June 30, 2017 , ComEd’s regulatory asset of $8 million reflects Constellation merger and integration costs to be recovered upon FERC approval. As of June 30, 2017 , ComEd’s regulatory liability of $40 million included $8 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 June 30, 2017 , PECO's regulatory asset of $1 million related to under-recovered electric transmission costs. As of June 30, 2017 , PECO's regulatory liability of $61 million included $36 million related to over-recovered costs under the DSP program, $16 million related to the over-recovered natural gas costs under the PGC and $9 million related to over-recovered non-bypassable transmission service charges. 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 June 30, 2017 , BGE's regulatory asset of $21 million included $10 million related to under-recovered electric energy costs, $5 million related to under-recovered natural gas costs, $4 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $2 million of abandonment costs to be recovered upon FERC approval. 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 June 30, 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 June 30, 2017 , Pepco's regulatory liability of $2 million related to 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 June 30, 2017 , DPL's regulatory asset of $6 million related to under-recovered electric energy costs. As of June 30, 2017 , DPL's regulatory liability of $12 million included $10 million of over-recovered electric energy 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 June 30, 2017 , ACE's regulatory asset of $27 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $16 million of under-recovered electric energy costs. As of June 30, 2017 , ACE's regulatory liability of $8 million related to 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 June 30, 2017 and December 31, 2016 , BGE's regulatory asset of $7 million and $10 million , respectively, included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order. (k) As of June 30, 2017 and December 31, 2016 , Pepco’s regulatory asset of $12 million and $11 million , respectively, represents previously incurred PHI acquisition costs authorized for recovery by the November 2016 Maryland distribution rate case order. As of June 30, 2017 , DPL’s regulatory asset of $13 million represents previously incurred PHI acquisition costs, including $4 million authorized for recovery by the February 2017 Maryland distribution rate case order, $6 million authorized for recovery by the May 2017 Delaware electric distribution rate case order, and $3 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 June 30, 2017 , BGE had a regulatory asset of $24 million related to under-recovered electric revenue decoupling and $11 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. Pepco's electric POR program in the District of Columbia included a discount on purchased receivables ranging from 0% to 6% through April 6, 2017 and 0% to 2% effective April 7, 2017, depending on customer class. DPL's electric POR program in Maryland included a discount on purchased receivables ranging from 0% to 1% through May 31, 2017 and 0% to 4% effective June 1, 2017, depending on customer class.

Early Nuclear Plant Retiremen30

Early Nuclear Plant Retirements Early Nuclear Plant Retirements (Tables)	6 Months Ended
	Jun. 30, 2017
Property, Plant and Equipment [Abstract]
Schedule of Other Operating Cost and Expense, by Component [Table Text Block]	Please refer to Note 12 — Nuclear Decommissioning for additional detail on changes to the nuclear decommissioning ARO balances resulting from the early retirement of TMI. Income statement expense (pre-tax) June 30, 2017 Depreciation and amortization Accelerated depreciation (a) $ 35 Accelerated Nuclear Fuel amortization 2 Total $ 37 ________ (a) Reflects incremental accelerated depreciation of plant assets, including any ARC. 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) Reflects incremental accelerated depreciation of plant assets, including any ARC, for the period June 2, 2016, through December 6, 2016. (b) Primarily includes 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)	6 Months Ended
	Jun. 30, 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 June 30, 2017 and December 31, 2016 : Exelon June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 1,757 $ — $ 1,757 $ — $ 1,757 Long-term debt (including amounts due within one year) (a) 33,934 — 33,460 1,956 35,416 Long-term debt to financing trusts (b) 641 — — 693 693 SNF obligation 1,139 — 830 — 830 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 716 $ — $ 716 $ — $ 716 Long-term debt (including amounts due within one year) (a) 9,754 — 8,061 1,661 9,722 SNF obligation 1,139 — 830 — 830 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 389 $ — $ 389 $ — $ 389 Long-term debt (including amounts due within one year) (a) 7,036 — 7,728 — 7,728 Long-term debt to financing trusts (b) 205 — — 223 223 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,580 $ — $ 2,834 $ — $ 2,834 Long-term debt to financing trusts 184 — — 199 199 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 85 $ — $ 85 $ — $ 85 Long-term debt (including amounts due within one year) (a) 2,282 — 2,497 — 2,497 Long-term debt to financing trusts (b) 252 — — 271 271 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) June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 67 $ — $ 67 $ — $ 67 Long-term debt (including amounts due within one year) (a) 5,952 — 5,707 295 6,002 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,545 $ — $ 3,065 $ 9 $ 3,074 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 25 $ — $ 25 $ — $ 25 Long-term debt (including amounts due within one year) (a) 1,326 — 1,398 — 1,398 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 42 $ — $ 42 $ — $ 42 Long-term debt (including amounts due within one year) (a) 1,138 — 980 286 1,266 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 $185 million , $53 million , $44 million , $15 million , $14 million , $6 million , $33 million , $11 million , and $5 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of June 30, 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 June 30, 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 June 30, 2017 and December 31, 2016 : Generation Exelon As of June 30, 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) $ 29 $ — $ — $ — $ 29 $ 257 $ — $ — $ — $ 257 NDT fund investments Cash equivalents (b) 117 67 — — 184 117 67 — — 184 Equities 3,980 717 — 2,104 6,801 3,980 717 — 2,104 6,801 Fixed income Corporate debt — 1,656 255 — 1,911 — 1,656 255 — 1,911 U.S. Treasury and agencies 1,767 32 — — 1,799 1,767 32 — — 1,799 Generation Exelon As of June 30, 2017 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Foreign governments — 51 — — 51 — 51 — — 51 State and municipal debt — 232 — — 232 — 232 — — 232 Other (c) — 46 — 502 548 — 46 — 502 548 Fixed income subtotal 1,767 2,017 255 502 4,541 1,767 2,017 255 502 4,541 Middle market lending — — 428 78 506 — — 428 78 506 Private equity — — — 197 197 — — — 197 197 Real estate — — — 441 441 — — — 441 441 NDT fund investments subtotal (d) 5,864 2,801 683 3,322 12,670 5,864 2,801 683 3,322 12,670 Pledged assets for Zion Station decommissioning Cash equivalents 21 — — — 21 21 — — — 21 Middle market lending — — 21 33 54 — — 21 33 54 Pledged assets for Zion Station (e) 21 — 21 33 75 21 — 21 33 75 Rabbi trust investments Cash equivalents 5 — — — 5 78 — — — 78 Mutual funds 22 — — — 22 54 — — — 54 Fixed income — — — — — — 13 — — 13 Life insurance contracts — 20 — — 20 — 67 21 — 88 Rabbi trust investments subtotal 27 20 — — 47 132 80 21 — 233 Commodity derivative assets Economic hedges 632 2,698 1,604 — 4,934 632 2,698 1,604 — 4,934 Proprietary trading 3 47 31 — 81 3 47 31 — 81 Effect of netting and allocation of collateral (f) (g) (627 ) (2,343 ) (767 ) — (3,737 ) (627 ) (2,343 ) (767 ) — (3,737 ) Commodity derivative assets subtotal 8 402 868 — 1,278 8 402 868 — 1,278 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 11 — — 11 Economic hedges — 17 — — 17 — 17 — — 17 Proprietary trading 3 1 — — 4 3 1 — — 4 Effect of netting and allocation of collateral (3 ) (10 ) — — (13 ) (3 ) (10 ) — — (13 ) Interest rate and foreign currency derivative assets subtotal — 8 — — 8 — 19 — — 19 Other investments — — 41 — 41 — — 41 — 41 Total assets 5,949 3,231 1,613 3,355 14,148 6,282 3,302 1,634 3,355 14,573 Liabilities Commodity derivative liabilities Economic hedges (697 ) (2,691 ) (1,151 ) — (4,539 ) (697 ) (2,691 ) (1,407 ) — (4,795 ) Proprietary trading (4 ) (48 ) (25 ) — (77 ) (4 ) (48 ) (25 ) — (77 ) Effect of netting and allocation of collateral (f) (g) 698 2,627 897 — 4,222 698 2,627 897 — 4,222 Commodity derivative liabilities subtotal (3 ) (112 ) (279 ) — (394 ) (3 ) (112 ) (535 ) — (650 ) Interest rate and foreign currency derivative liabilities Generation Exelon As of June 30, 2017 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Economic hedges — (20 ) — — (20 ) — (20 ) — — (20 ) Proprietary trading (4 ) — — — (4 ) (4 ) — — — (4 ) Effect of netting and allocation of collateral 3 10 — — 13 3 10 — — 13 Interest rate and foreign currency derivative liabilities subtotal (1 ) (10 ) — — (11 ) (1 ) (10 ) — — (11 ) Deferred compensation obligation — (33 ) — — (33 ) — (131 ) — — (131 ) Total liabilities (4 ) (155 ) (279 ) — (438 ) (4 ) (253 ) (535 ) — (792 ) Total net assets $ 5,945 $ 3,076 $ 1,334 $ 3,355 $ 13,710 $ 6,278 $ 3,049 $ 1,099 $ 3,355 $ 13,781 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 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 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 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 $238 million and $252 million at June 30, 2017 and December 31, 2016 and restricted cash of $164 million and $157 million at June 30, 2017 and December 31, 2016 . Exelon excludes cash of $353 million and $360 million at June 30, 2017 and December 31, 2016 and restricted cash of $203 million and $180 million at June 30, 2017 and December 31, 2016 and includes long term restricted cash of $25 million at June 30, 2017 and December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) Includes $48 million and $29 million of cash received from outstanding repurchase agreements at June 30, 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 $771 million and $933 million at June 30, 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 liabilities of $29 million and $31 million at June 30, 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 June 30, 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 $71 million , $284 million and $130 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of June 30, 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), $84 million represents variation margin on the exchanges as of June 30, 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 June 30, 2017 and December 31, 2016 : ComEd PECO BGE As of June 30, 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) $ — $ — $ — $ — $ 28 $ — $ — $ 28 $ 5 $ — $ — $ 5 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 — — — — 35 10 — 45 10 — — 10 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (10 ) — (10 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (256 ) (256 ) — — — — — — — — Total liabilities — (7 ) (256 ) (263 ) — (10 ) — (10 ) — (4 ) — (4 ) Total net assets (liabilities) $ — $ (7 ) $ (256 ) $ (263 ) $ 35 $ — $ — $ 35 $ 10 $ (4 ) $ — $ 6 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 $39 million and $36 million at June 30, 2017 and December 31, 2016 and restricted cash of $12 million and $2 million at June 30, 2017 and December 31, 2016 . PECO excludes cash of $21 million and $22 million at June 30, 2017 and December 31, 2016 . BGE excludes cash of $12 million and $13 million at June 30, 2017 and December 31, 2016 and restricted cash of $3 million at June 30, 2017 and includes long term restricted cash of $2 million at June 30, 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 $237 million , respectively, at June 30, 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 June 30, 2017 and December 31, 2016 : Successor As of June 30, 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) $ 189 $ — $ — $ 189 $ 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 73 — — 73 73 — — 73 Fixed income — 13 — 13 — 16 — 16 Life insurance contracts — 23 21 44 — 22 20 42 Rabbi trust investments subtotal 73 36 21 130 73 38 20 131 Total assets 262 36 21 319 290 38 20 348 Liabilities Deferred compensation obligation — (24 ) — (24 ) — (28 ) — (28 ) Total liabilities — (24 ) — (24 ) — (28 ) — (28 ) Total net assets $ 262 $ 12 $ 21 $ 295 $ 290 $ 10 $ 20 $ 320 Pepco DPL ACE As of June 30, 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) $ 144 $ — $ — $ 144 $ — $ — $ — $ — $ 29 $ — $ — $ 29 Rabbi trust investments Cash equivalents 43 — — 43 — — — — — — — — Fixed income — 13 — 13 — — — — — — — — Life insurance contracts — 23 21 44 — — — — — — — — Rabbi trust investments subtotal 43 36 21 100 — — — — — — — — Total assets 187 36 21 244 — — — — 29 — — 29 Liabilities Deferred compensation obligation — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total liabilities — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 187 $ 32 $ 21 $ 240 $ — $ (1 ) $ — $ (1 ) $ 29 $ — $ — $ 29 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 $24 million and $19 million at June 30, 2017 and December 31, 2016 and includes long term restricted cash of $22 million and $23 million at June 30, 2017 and December 31, 2016 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $9 million at June 30, 2017 and December 31, 2016 . DPL excludes cash of $6 million and $4 million at June 30, 2017 and December 31, 2016 . ACE excludes cash of $7 million and $3 million at June 30, 2017 and December 31, 2016 and includes long term restricted cash of $22 million and $23 million at June 30, 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 and six months ended June 30, 2017 and 2016 : Successor Generation ComEd PHI Exelon Three Months Ended June 30, 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 March 31, 2017 $ 683 $ 20 $ 565 $ 40 $ 1,308 $ (282 ) $ 20 $ — $ 1,046 Total realized / unrealized gains (losses) Included in net income 1 — (3 ) (b) — (2 ) — — — (2 ) Included in noncurrent payables to affiliates 4 — — — 4 — — (4 ) — Included in payable for Zion Station decommissioning — 1 — — 1 — — — 1 Included in regulatory assets — — — — — 26 — 4 30 Change in collateral — — 31 — 31 — — — 31 Purchases, sales, issuances and settlements Purchases 19 — 21 1 41 — — — 41 Sales — — (13 ) — (13 ) — — — (13 ) Settlements (24 ) — — — (24 ) — — — (24 ) Transfers into Level 3 — — (8 ) — (8 ) — — — (8 ) Transfers out of Level 3 — — (4 ) — (4 ) — — — (4 ) Balance at June 30, 2017 $ 683 $ 21 $ 589 $ 41 $ 1,334 $ (256 ) $ 20 $ — $ 1,098 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of June 30, 2017 $ — $ — $ 43 $ — $ 43 $ — $ — $ — $ 43 Successor Generation ComEd PHI Exelon Six Months Ended June 30, 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 4 — (46 ) (b) 1 (41 ) — 1 — (40 ) Included in noncurrent payables to affiliates 13 — — — 13 — — (13 ) — Included in payable for Zion Station decommissioning — 1 — — 1 — — — 1 Included in regulatory assets — — — — — 2 — 13 15 Change in collateral — — 69 — 69 — — — 69 Purchases, sales, issuances and settlements Purchases 36 1 90 3 130 — — — 130 Sales — — (15 ) — (15 ) — — — (15 ) Issuances — — — — — — (1 ) — (1 ) Settlements (47 ) — — — (47 ) — — — (47 ) Transfers into Level 3 — — (10 ) — (10 ) — — — (10 ) Transfers out of Level 3 — — 8 (5 ) 3 — — — 3 Balance as of June 30, 2017 $ 683 $ 21 $ 589 $ 41 $ 1,334 $ (256 ) $ 20 $ — $ 1,098 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of June 30, 2017 $ 2 $ — $ 102 $ 1 $ 105 $ — $ 1 $ — $ 106 ___________________ (a) Includes $ 25 million of increases in fair value and an increase for realized losses due to settlements of $ 1 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended June 30, 2017 . Includes $ 5 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 six months ended June 30, 2017 . (b) Includes a reduction for the reclassification of $46 million and $148 million of realized gains due to the settlement of derivative contracts for the three and six months ended June 30, 2017 . Successor Generation ComEd PHI Exelon Three Months Ended June 30, 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 March 31, 2016 $ 684 $ 25 $ 1,047 $ 36 $ 1,792 $ (265 ) $ 20 $ — $ 1,547 Total realized / unrealized gains (losses) Included in net income 4 — (428 ) (b) — (424 ) — 1 — (423 ) Included in noncurrent payables to affiliates 8 — — — 8 — — (8 ) — Included in regulatory assets — — — — — 44 — 8 52 Change in collateral — — (32 ) — (32 ) — — — (32 ) Purchases, sales, issuances and settlements Purchases 85 — 23 1 109 — — — 109 Sales (1 ) — (1 ) — (2 ) — — — (2 ) Issuances — — — — — — (1 ) — (1 ) Settlements (65 ) — — — (65 ) — — — (65 ) Transfers into Level 3 — — — — — — — — — Transfers out of Level 3 — — — — — — — — — Balance as of June 30, 2016 $ 715 $ 25 $ 609 $ 37 $ 1,386 $ (221 ) $ 20 $ — $ 1,185 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of June 30, 2016 $ 3 $ — $ (264 ) $ — $ (261 ) $ — $ 1 $ — $ (260 ) Successor Generation ComEd PHI (c) Exelon Six Months Ended June 30, 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 6 — (434 ) (b) — (428 ) — 1 — (427 ) Included in noncurrent payables to affiliates 12 — — — 12 — — (12 ) — Included in payable for Zion Station decommissioning — 2 — — 2 — — — 2 Included in regulatory assets — — — — — 26 — 12 38 Change in collateral — — (82 ) — (82 ) — — — (82 ) Purchases, sales, issuances and settlements Purchases 119 1 82 4 206 — — — 206 Sales (1 ) — (3 ) — (4 ) — — — (4 ) Issuances — — — — — — (1 ) — (1 ) Settlements (91 ) — — — (91 ) — — — (91 ) Transfers into Level 3 — — 2 — 2 — — — 2 Transfers out of Level 3 — — (7 ) — (7 ) — — — (7 ) Balance as of June 30, 2016 $ 715 $ 25 $ 609 $ 37 $ 1,386 $ (221 ) $ 20 $ — $ 1,185 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of June 30, 2016 $ 4 $ — $ (45 ) $ — $ (41 ) $ — $ 1 $ — $ (40 ) _________ (a) Includes $40 million of increases in fair value and an increase for realized losses due to settlements of $4 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended June 30, 2016 . Includes $15 million of increases in fair value and an increase for realized losses due to settlements of $11 million for the six months ended June 30, 2016 . (b) Includes a reduction for the reclassification of $164 million and $389 million of realized gains due to the settlement of derivative contracts recorded in results of operations for the three and six months ended June 30, 2016 . (c) Successor period represents activity from March 24, 2016 through June 30, 2016 . See tables below for PHI's predecessor periods, as well as activity for Pepco for the three and six months ended June 30, 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 Six Months Ended Pepco 2017 2016 2017 2016 Beginning balance $ 20 $ 20 $ 20 $ 19 Total realized / unrealized gains (losses) Included in net income — 1 1 2 Purchases, sales, issuances and settlements Issuances — (1 ) (1 ) (1 ) Ending balance $ 20 $ 20 $ 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 $ — $ 2
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 and six months ended June 30, 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 June 30, 2017 $ (51 ) $ 48 $ 1 $ — $ (51 ) $ 48 $ 1 Total gains (losses) included in net income for the six months ended June 30, 2017 37 (83 ) 5 1 37 (83 ) 6 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended June 30, 2017 — 43 — — — 43 — Change in the unrealized gains (losses) relating to assets and liabilities held for the six months ended June 30, 2017 140 (38 ) 3 1 140 (38 ) 4 Successor Generation PHI Exelon Operating Revenues Purchased Power and Fuel Other, net (a) Other, net (a) Operating Revenues Purchased Power and Fuel Other, net (a) Total gains (losses) included in net income for the three months ended June 30, 2016 $ (462 ) $ 34 $ 4 $ 1 $ (462 ) $ 34 $ 5 Total gains (losses) included in net income for the six months ended June 30, 2016 (413 ) (21 ) 6 1 (413 ) (21 ) 7 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended June 30, 2016 (274 ) 10 3 1 (274 ) 10 4 Change in the unrealized gains (losses) relating to assets and liabilities held for the six months ended June 30, 2016 (20 ) (25 ) 4 1 (20 ) (25 ) 5 Predecessor PHI Pepco January 1, 2016 to March 23, 2016 Three Months Ended Six Months Ended 2017 2016 2017 2016 Other, net (a) Other, net (a) Total gains (losses) included in net income $ (17 ) $ — $ 1 $ 1 $ 2 Change in the unrealized gains (losses) relating to assets and liabilities held 1 — 1 1 2 _________ (a) Other, net activity consists of realized and unrealized gains (losses) included in income for the NDT funds held by Generation, accrued interest on a convertible promissory note at 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 June 30, 2017 Valuation Technique Unobservable Input Range Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(c) $ 453 Discounted Forward power $8 - $124 Forward gas $1.92 - $9.37 Option Model Volatility 11% - 253% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(c) $ 6 Discounted Forward power $11 - $73 Mark-to-market derivatives (Exelon and ComEd) $ (256 ) Discounted Forward heat (b) 9x - 10x Marketability 3% - 8% Renewable 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 $130 million as of June 30, 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 716 $ — $ 716 $ — $ 716 Long-term debt (including amounts due within one year) (a) 9,754 — 8,061 1,661 9,722 SNF obligation 1,139 — 830 — 830 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 389 $ — $ 389 $ — $ 389 Long-term debt (including amounts due within one year) (a) 7,036 — 7,728 — 7,728 Long-term debt to financing trusts (b) 205 — — 223 223 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,580 $ — $ 2,834 $ — $ 2,834 Long-term debt to financing trusts 184 — — 199 199 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 85 $ — $ 85 $ — $ 85 Long-term debt (including amounts due within one year) (a) 2,282 — 2,497 — 2,497 Long-term debt to financing trusts (b) 252 — — 271 271 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) June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 67 $ — $ 67 $ — $ 67 Long-term debt (including amounts due within one year) (a) 5,952 — 5,707 295 6,002 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,545 $ — $ 3,065 $ 9 $ 3,074 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 25 $ — $ 25 $ — $ 25 Long-term debt (including amounts due within one year) (a) 1,326 — 1,398 — 1,398 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 June 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 42 $ — $ 42 $ — $ 42 Long-term debt (including amounts due within one year) (a) 1,138 — 980 286 1,266 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)	6 Months Ended
	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of the derivative fair value	Below is a summary of the interest rate and foreign exchange hedge balances as of June 30, 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) $ — $ 14 $ 3 $ (11 ) $ 6 $ — $ 6 Mark-to-market derivative assets (noncurrent assets) — 3 1 (2 ) 2 11 13 Total mark-to-market derivative assets — 17 4 (13 ) 8 11 19 Mark-to-market derivative liabilities (current liabilities) — (17 ) (4 ) 11 (10 ) — (10 ) Mark-to-market derivative liabilities (noncurrent liabilities) — (3 ) — 2 (1 ) — (1 ) Total mark-to-market derivative liabilities — (20 ) (4 ) 13 (11 ) — (11 ) Total mark-to-market derivative net assets (liabilities) $ — $ (3 ) $ — $ — $ (3 ) $ 11 $ 8 _________ (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. The following table provides a summary of the derivative fair value balances recorded by the Registrants as of June 30, 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) $ 3,198 $ 58 $ (2,429 ) $ 827 $ — $ — $ — $ — $ — $ 827 Mark-to-market derivative assets (noncurrent assets) 1,736 23 (1,308 ) 451 — — — — — 451 Total mark-to-market derivative assets 4,934 81 (3,737 ) 1,278 — — — — — 1,278 Mark-to-market derivative liabilities (current liabilities) (2,895 ) (52 ) 2,732 (215 ) (19 ) — — — — (234 ) Mark-to-market derivative liabilities (noncurrent liabilities) (1,644 ) (25 ) 1,490 (179 ) (237 ) — — — — (416 ) Total mark-to-market derivative liabilities (4,539 ) (77 ) 4,222 (394 ) (256 ) — — — — (650 ) Total mark-to-market derivative net assets (liabilities) $ 395 $ 4 $ 485 $ 884 $ (256 ) $ — $ — $ — $ — $ 628 ______ (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 $149 million and $74 million , respectively, and current and noncurrent liabilities are shown net of collateral of $155 million and $107 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $485 million at June 30, 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), $84 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. (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), $(158) million represents variation margin on the exchanges. 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 June 30, Income Statement Location 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on Borrowings Exelon Interest expense $ 1 $ 5 $ 2 $ (1 ) Six Months Ended June 30, Income Statement Location 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on Borrowings Exelon Interest expense $ (4 ) $ 22 $ 10 $ (16 )
The activity of accumulated OCI related to cash flow hedges	The amounts reclassified from OCI, when combined with the impacts of the hedged transactions, result in the ultimate recognition of net revenues or expenses at the contractual price. Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Three Months Ended June 30, 2017 Income Statement Location Total Cash Total Cash Flow Hedges Accumulated OCI derivative loss at March 31, 2017 $ (13 ) $ (11 ) Effective portion of changes in fair value (1 ) (1 ) Accumulated OCI derivative loss at June 30, 2017 $ (14 ) $ (12 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Six Months Ended June 30, 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 1 1 Reclassifications from AOCI to net income Interest Expense 4 (a) 4 (a) Accumulated OCI derivative loss at June 30, 2017 $ (14 ) $ (12 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Three Months Ended June 30, 2016 Income Statement Location Total Cash Total Cash Flow Hedges Accumulated OCI derivative loss at March 31, 2016 $ (26 ) $ (26 ) Reclassifications from AOCI to net income Interest Expense 1 — Accumulated OCI derivative loss at June 30, 2016 $ (25 ) $ (26 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Six Months Ended June 30, 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 (7 ) (10 ) Reclassifications from AOCI to net income Interest Expense 3 (b) 3 (b) Accumulated OCI derivative loss at June 30, 2016 $ (25 ) $ (26 ) ______ (a) Amount is net of related income tax expense of $3 million for the six months ended June 30, 2017 . (b) Amount is net of related income tax expense of $2 million for the six months ended June 30, 2016 .
Other Derivatives - Gain (loss) and reclassification	In the tables below, “Change in fair value” represents the change in fair value of the derivative contracts held at the reporting date. The “Reclassification to realized” represents the recognized change in fair value that was reclassified to realized due to settlement of the derivative during the period. Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Change in fair value of commodity positions $ 6 $ 5 $ 6 $ 14 Reclassification to realized of commodity positions (6 ) (5 ) (7 ) (11 ) Net commodity mark-to-market gains (losses) — — (1 ) 3 Change in fair value of treasury positions — — (1 ) (2 ) Reclassification to realized of treasury positions — (1 ) — 1 Net treasury mark-to-market gains (losses) — (1 ) (1 ) (1 ) Total net mark-to-market gains (losses) $ — $ (1 ) $ (2 ) $ 2 In the tables below, “Change in fair value” represents the change in fair value of the derivative contracts held at the reporting date. The “Reclassification to realized” generally represents the recognized change in fair value that was reclassified from unrealized to realized when the transaction to which the derivative relates occurs. Generation Exelon Three Months Ended June 30, 2017 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ (100 ) $ (62 ) $ (162 ) $ (162 ) Reclassification to realized at settlement of commodity positions (41 ) 21 (20 ) (20 ) Net commodity mark-to-market gains (losses) (141 ) (41 ) (182 ) (182 ) Change in fair value of treasury positions (2 ) — (2 ) (2 ) Reclassification to realized at settlement of treasury positions — — — — Net treasury mark-to-market gains (losses) (2 ) — (2 ) (2 ) Net mark-to-market gains (losses) $ (143 ) $ (41 ) $ (184 ) $ (184 ) Generation Exelon Six Months Ended June 30, 2017 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ (9 ) $ (197 ) $ (206 ) $ (206 ) Reclassification to realized of commodity positions (87 ) 63 (24 ) (24 ) Net commodity mark-to-market gains (losses) (96 ) (134 ) (230 ) (230 ) Change in fair value of treasury positions (1 ) — (1 ) (1 ) Reclassification to realized of treasury positions (2 ) — (2 ) (2 ) Net treasury mark-to-market gains (losses) (3 ) — (3 ) (3 ) Net mark-to-market gains (losses) $ (99 ) $ (134 ) $ (233 ) $ (233 ) Generation Exelon Three Months Ended June 30, 2016 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ (432 ) $ 235 $ (197 ) $ (197 ) Reclassification to realized at settlement of commodity positions (181 ) 76 (105 ) (105 ) Net commodity mark-to-market gains (losses) (613 ) 311 (302 ) (302 ) Change in fair value of treasury positions 1 — 1 1 Reclassification to realized at settlement of treasury positions (3 ) — (3 ) (3 ) Net treasury mark-to-market gains (losses) (2 ) — (2 ) (2 ) Net mark-to-market gains (losses) $ (615 ) $ 311 $ (304 ) $ (304 ) Generation Exelon Six Months Ended June 30, 2016 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ (153 ) $ 109 $ (44 ) $ (44 ) Reclassification to realized of commodity positions (392 ) 243 (149 ) (149 ) Net commodity mark-to-market gains (losses) (545 ) 352 (193 ) (193 ) Change in fair value of treasury positions (4 ) — (4 ) (4 ) Reclassification to realized of treasury positions (4 ) — (4 ) (4 ) Net treasury mark-to-market gains (losses) (8 ) — (8 ) (8 ) Net mark-to-market gains (losses) $ (553 ) $ 352 $ (201 ) $ (201 )
Information on Generation's credit exposure for all derivative instruments, normal purchase normal sales, and applicable payables and receivables, net of collateral and instruments that are subject to master netting agreements	The aggregate fair value of all derivative instruments with credit-risk-related contingent features in a liability position that are not fully collateralized (excluding transactions on the exchanges that are fully collateralized) is detailed in the table below: Credit-Risk Related Contingent Feature June 30, 2017 December 31, 2016 Gross Fair Value of Derivative Contracts Containing this Feature (a) $ (942 ) $ (960 ) Offsetting Fair Value of In-the-Money Contracts Under Master Netting Arrangements (b) 601 627 Net Fair Value of Derivative Contracts Containing This Feature (c) $ (341 ) $ (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. The 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 June 30, 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 $23 million , $27 million , $21 million , $41 million , $12 million , and $6 million as of June 30, 2017 , respectively. Rating as of June 30, 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 $ 878 $ 14 $ 864 1 $ 299 Non-investment grade 47 1 46 — — No external ratings Internally rated — investment grade 327 — 327 — — Internally rated — non-investment grade 123 14 109 — — Total $ 1,375 $ 29 $ 1,346 1 $ 299 Net Credit Exposure by Type of Counterparty As of June 30, 2017 Financial institutions $ 89 Investor-owned utilities, marketers, power producers 563 Energy cooperatives and municipalities 560 Other 134 Total $ 1,346 _____ (a) As of June 30, 2017 , credit collateral held from counterparties where Generation had credit exposure included $19 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)	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Commercial Paper Borrowings	The Registrants had the following amounts of commercial paper borrowings outstanding as of June 30, 2017 and December 31, 2016 : Commercial Paper Borrowings June 30, 2017 December 31, 2016 Exelon Corporate $ — $ — Generation 569 620 ComEd 389 — BGE 85 45 Pepco — 23 DPL 25 — ACE 42 —
Issuance Of Long Term Debt	During the six months ended June 30, 2017 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Exelon Junior Subordinated Notes (a) 3.50 % June 1, 2022 $ 1,150 Refinance Exelon's Junior Subordinated Notes issued in June 2014. Generation Albany Green Energy Project Financing LIBOR + 1.25% November 17, 2017 $ 13 Albany Green Energy biomass generation development. Generation Energy Efficiency Project Financing 3.90 % February 1, 2018 $ 12 Funding to install energy conservation measures for the Naval Station Great Lakes project. Generation Energy Efficiency Project Financing 2.61 % September 30, 2018 $ 6 Funding to install energy conservation measures for the Pensacola project. Generation Energy Efficiency Project Financing 3.53 % April 1, 2019 $ 8 Funding to install energy conservation measures for the State Department project. Generation Energy Efficiency Project Financing 3.72 % May 1, 2018 $ 3 Funding to install energy conservation measures for the Smithsonian Zoo project. 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. Generation ExGen Texas Power Nonrecourse Debt LIBOR + 4.75% September 18, 2021 $ 6 Funding 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. Pepco First Mortgage Bonds 4.15 % March 15, 2043 $ 200 Funding to repay outstanding commercial paper and for general corporate purposes.

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The effective income tax rate from continuing operations varies from the U.S. Federal statutory rate principally due to the following: Three Months Ended June 30, 2017 Successor Exelon (a) Generation (b) 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 (2,745.7) 5.6 5.8 (0.6) 5.0 3.2 4.6 5.6 4.3 Qualified nuclear decommissioning trust fund income 3,156.6 (6.3) — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (528.7) 0.9 (0.2) (0.1) (0.2) (0.1) (0.1) (0.4) (0.1) Plant basis differences (2,764.4) — (0.2) (16.0) (0.3) (6.2) (1.7) (3.3) (4.8) Production tax credits and other credits (1,035.7) 2.0 — — — — — — — Noncontrolling interests 84.7 (0.2) — — — — — — — Like-kind exchange (c) (5,362.4) — 5.9 — — — — — — Other 1,960.6 1.1 0.5 0.2 1.3 (0.2) 0.9 (3.6) 0.9 Effective income tax rate (7,200.0)% 38.1% 46.8% 18.5% 40.8% 31.7% 38.7% 33.3% 35.3% Three Months Ended June 30, 2016 Successor Exelon Generation (d) ComEd PECO BGE (e) 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 2.3 (116.7) 4.8 0.3 2.0 3.5 4.8 5.9 6.1 Qualified nuclear decommissioning trust fund income 5.7 591.2 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.8) (157.8) (0.2) (0.1) (0.4) (0.1) (0.6) (1.6) (0.3) Plant basis differences (f) (6.9) — (0.4) (11.3) (20.6) (5.7) (3.5) (7.1) (7.0) Production tax credits and other credits (5.8) (603.0) — — — — — — — Noncontrolling interest 0.9 94.4 — — — — — — — Statute of limitations expiration (1.7) (410.8) — — — — — — — Merger expenses 0.2 — — — — 0.2 3.1 — 1.0 Other (g) (3.3) (52.3) (0.6) (5.2) (1.0) (1.0) 1.2 7.8 1.0 Effective income tax rate 24.6% (620.0)% 38.6% 18.7% 15.0% 31.9% 40.0% 40.0% 35.8% Six Months Ended June 30, 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 (1.0) (13.6) 5.3 (0.1) 5.1 3.8 5.1 5.6 4.6 Qualified nuclear decommissioning trust fund income 5.6 51.2 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.7) (5.4) (0.2) (0.1) (0.1) (0.1) (0.2) (0.4) (0.2) Plant basis differences (4.3) — (0.2) (14.3) (0.7) (6.0) (1.8) (3.3) (4.3) Production tax credits and other credits (1.4) (12.3) — — — — — — — Noncontrolling interests (0.1) (0.5) — — — — — — — Merger expenses (h) (11.4) (13.7) — — — (16.2) (15.1) (85.3) (23.8) Fitzpatrick bargain purchase gain (6.5) (60.0) — — — — — — — Like-kind exchange (c) (3.7) — 2.9 — — — — — — Other 0.3 (4.2) 0.4 (0.1) 0.3 (0.7) 1.0 (1.6) — Effective income tax rate 11.8% (23.5)% 43.2% 20.4% 39.6% 15.8% 24.0% (50.0)% 11.3% Successor Predecessor Six Months Ended June 30, 2016 March 24, 2016 to June 30, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco (i) DPL (i) ACE (i) PHI (i) 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 (i) 0.8 2.6 4.9 0.7 4.6 (9.5) (5.2) 5.9 5.2 11.9 Qualified nuclear decommissioning trust fund income 5.6 9.8 — — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.7) (2.5) (0.2) (0.1) (0.1) 0.1 0.4 0.1 0.1 (0.9) Plant basis differences (f) (6.3) — (0.3) (10.2) (4.5) 12.6 2.0 1.0 1.7 (13.5) Production tax credits and other credits (5.5) (9.6) — — — — — — — — Noncontrolling interest 0.7 1.2 — — — — — — — — Statute of limitations expiration (1.0) (3.9) — — — — — — — — Merger expenses 14.5 — — — — (36.1) (30.5) (17.7) (18.9) 11.1 Other (g) (2.8) (3.8) (0.1) (2.4) 0.1 (0.5) (0.1) (0.1) — 3.6 Effective income tax rate 39.3% 28.8% 39.3% 23.0% 35.1% 1.6% 1.6% 24.2% 23.1% 47.2% (a) The effective tax rate for the three months ended June 30, 2017 is disproportionately impacted due to the decline in consolidated pre-tax GAAP earnings as compared to the federal and state tax impacts of the Like-kind exchange, tax credits, Plant basis differences, and Qualified nuclear decommissioning trust fund income. (b) Generation recognized a loss before income taxes for the three months ended June 30, 2017 . As a result, positive percentages represent an income tax benefit for the period presented. (c) See Like-Kind Exchange within the Other Income Tax Matters section below for further details. (d) The effective tax rate for the three months ended June 30, 2016, is disproportionately impacted due to the decline in pre-tax GAAP earnings as compared to the changes in tax credits and other reconciling items. In three months ended June 30, 2016, due to the expiration of a statute of limitations, Generation recorded an income tax benefit of $ 16 million . The statute of limitations expired in the third quarter of 2015; therefore, this represents an out of period adjustment. (e) The effective tax rate for the three months ended June 30, 2016 is disproportionately impacted due to the decline in pre-tax GAAP earnings and changes in other reconciling items. (f) At BGE, includes a cumulative adjustment related to a regulatory asset. (g) At PECO, includes a cumulative adjustment related to an anticipated gas repairs tax return accounting method change. (h) Includes a remeasurement of uncertain federal and state income tax positions, see below. (i) Pepco, DPL and ACE recognized a loss before income taxes for the six months ended June 30, 2016 , and PHI recognized a loss before income taxes for the period of March 24, 2016, through June 30, 2016 . As a result, positive percentages represent an income tax benefit for the periods presented. (j) Includes a remeasurement of uncertain state income tax positions for Pepco and DPL.	[1]
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	The Registrants have the following unrecognized tax benefits as of June 30, 2017 and December 31, 2016 : Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE June 30, 2017 $ 730 $ 467 $ 2 $ — $ 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
[1]	Includes a remeasurement of uncertain federal and state income tax positions, see below.

Nuclear Decommissioning (Tables

Nuclear Decommissioning (Tables)	6 Months Ended
	Jun. 30, 2017
Schedule Of Nuclear Decommissioning [Line Items]
Zion Station pledged assets	and December 31, 2016 : Exelon and Generation June 30, 2017 December 31, 2016 Carrying value of Zion Station pledged assets $ 75 $ 113 Payable to Zion Solutions (a) 69 104 Current portion of payable to Zion Solutions (b) 69 90 Cumulative withdrawals by Zion Solutions to pay decommissioning costs (c) 914 878 _________ (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.
Schedule of Change in Asset Retirement Obligation [Table Text Block]	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 June 30, 2017 : Nuclear decommissioning ARO at December 31, 2016 (a) $ 8,734 Acquisition of FitzPatrick 417 Net increase due to changes in, and timing of, estimated cash flows 103 Accretion expense 225 Costs incurred to decommission retired plants (3 ) Nuclear decommissioning ARO at June 30, 2017 (a)(b) $ 9,476 _________ (a) Includes $12 million and $10 million for the current portion of the ARO at June 30, 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 Gain (Loss) on Investments [Table Text Block]	The following table provides unrealized gains on NDT funds for the three and six months ended June 30, 2017 and 2016 : Exelon and Generation Exelon and Generation Three Months Ended June 30, Six Months Ended 2017 2016 2017 2016 Net unrealized gains (losses) on decommissioning trust funds — Regulatory Agreement Units (a) $ (13 ) $ 52 $ 210 $ 131 Net unrealized gains on decommissioning trust funds — Non-Regulatory Agreement Units (b)(c) 70 48 235 100 _________ (a) Net unrealized gains (losses) related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets. (b) Excludes $(2) million and $1 million of net unrealized gains (losses) related to the Zion Station pledged assets for the three months ended June 30, 2017 and 2016 respectively. Excludes $(2) million and $3 million of net unrealized gains (losses) related to the Zion Station pledged assets for the six months ended June 30, 2017 and 2016, respectively. Net unrealized gains (losses) related to Zion Station pledged assets are included in Other current liabilities and Payable for Zion Station decommissioning on Exelon’s and Generation’s Consolidated Balance Sheets in 2017 and 2016, respectively. (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.

Retirement Benefits (Tables)

Retirement Benefits (Tables)	6 Months Ended
	Jun. 30, 2017
Retirement Benefits [Abstract]
Schedule of Net Benefit Costs [Table Text Block]	The following tables present the components of Exelon's net periodic benefit costs, prior to capitalization, for the three and six months ended June 30, 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 (a) 2016 (b) 2017 (a) 2016 (b) Components of net periodic benefit cost: Service cost $ 97 $ 91 $ 28 $ 28 Interest cost 211 212 46 48 Expected return on assets (299 ) (292 ) (41 ) (42 ) Amortization of: Prior service cost (benefit) 1 4 (47 ) (47 ) Actuarial loss 150 142 15 16 Settlement charges 2 — — — Net periodic benefit cost $ 162 $ 157 $ 1 $ 3 Pension Benefits Other Postretirement Benefits 2017 (a) 2016 (b) 2017 (a) 2016 (b) Components of net periodic benefit cost: Service cost $ 191 $ 170 $ 54 $ 54 Interest cost 422 403 91 90 Expected return on assets (598 ) (555 ) (82 ) (80 ) Amortization of: Prior service cost (benefit) 1 7 (94 ) (91 ) Actuarial loss 302 269 31 30 Settlement charges 2 — — — Net periodic benefit cost $ 320 $ 294 $ — $ 3 _______ (a) FitzPatrick net benefit costs are included for the period after acquisition. (b) 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
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 and six months ended June 30, 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 June 30, 2016 , respectively. Three Months Ended June 30, Six Months Ended June 30, Pension and Other Postretirement Benefit Costs 2017 2016 2017 2016 Exelon $ 163 $ 160 $ 320 $ 297 Generation (c) 59 55 113 109 ComEd 44 42 87 83 PECO 7 8 14 17 BGE 16 18 32 33 BSC (a) 13 10 26 24 Pepco (b) 6 7 13 16 DPL (b) 3 4 6 9 ACE (b) 3 4 7 8 PHISCO (a)(b) 12 12 22 21 Successor Predecessor Pension and Other Postretirement Benefit Costs Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Six Months Ended June 30, 2017 March 24, 2016 to June 30, 2016 January 1, 2016 to March 23, 2016 PHI $ 24 $ 27 $ 48 $ 31 $ 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 six months ended June 30, 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 .
Schedule Of Defined Contributions	The following table presents the matching contributions to the savings plans during the three and six months ended June 30, 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 June 30, 2016 , respectively. Three Months Ended June 30, Six Months Ended June 30, Savings Plan Matching Contributions 2017 2016 2017 2016 Exelon $ 33 $ 30 $ 63 $ 56 Generation 14 13 28 25 ComEd 8 7 15 13 PECO 2 2 4 4 BGE 3 2 4 3 BSC (a) 3 2 5 7 Pepco (b) 1 1 2 2 DPL (b) 1 — 1 1 PHISCO (a)(b) 1 2 3 3 ACE — 1 1 1 Successor Predecessor Savings Plan Matching Contributions Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Six Months Ended June 30, 2017 March 24, 2016 to June 30, 2016 January 1, 2016 to March 23, 2016 PHI $ 3 $ 4 $ 7 $ 4 $ 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 six months ended June 30, 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 six months ended June 30, 2016 .

Severance (Tables)

Severance (Tables)	6 Months Ended
	Jun. 30, 2017
Restructuring and Related Activities [Abstract]
Severance	For the three and six months ended June 30, 2017 , the PHI merger severance costs were immaterial. For the three and six months ended June 30, 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 June 30, 2016 Severance costs (benefits) (a) $ 2 $ (1 ) $ (1 ) $ — $ — $ 4 $ 2 $ 1 $ 1 Six Months Ended June 30, 2016 Severance costs (a) $ 55 $ 9 $ 2 $ 1 $ 1 $ 42 $ 20 $ 12 $ 10 ______________ (a) The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $(1) million , $(1) million , less than $1 million , less than $1 million , $2 million , $1 million and $1 million , respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the three months ended June 30, 2016 , and $8 million , $2 million , $1 million , $1 million , $19 million , $11 million and $10 million for the six months ended June 30, 2016 . For the six months ended June 30, 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 Six Months Ended June 30, 2017 (a) $ (1 ) $ (1 ) $ — $ — $ — June 30, 2016 (b) $ 17 $ 12 $ 3 $ 1 $ 1 _______ (a) Amounts billed by BSC through intercompany allocations for the six months ended June 30, 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 six months ended June 30, 2016 . For the three and six months ended June 30, 2017 and 2016 , Exelon, Generation, ComEd, PHI, Pepco, DPL, and ACE recorded the following severance costs associated with these ongoing severance benefits within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income. Successor Exelon Generation (a) ComEd (a) PHI Pepco (a) DPL (a) ACE (a) Three Months Ended June 30, 2017 $ 5 $ 1 $ 1 $ 3 $ 1 $ 1 $ 1 June 30, 2016 2 1 1 — — — — Six Months Ended June 30, 2017 $ 9 $ 4 $ 2 $ 3 $ 1 $ 1 $ 1 June 30, 2016 4 3 1 — — — — _______ (a) The amounts above for Generation include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017 , respectively, and $1 million and $2 million for the three and six months ended June 30, 2016 , respectively. The amounts above for ComEd include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017 , respectively, and less than $1 million and $1 million for the three and six months ended June 30, 2016 , respectively. Amounts billed by PHISCO to Pepco, DPL and ACE were $1 million , each, for both three and six months ended June 30, 2017 . Pepco, DPL and ACE did not have any ongoing severance plans for the three and six months ended June 30, 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) 25 17 1 — — 3 — — — Payments (18 ) (4 ) (1 ) — — (10 ) — — — Balance at June 30, 2017 $ 95 $ 49 $ 3 $ — $ — $ 22 $ — $ — $ — ______________ (a) Includes salary continuance and health and welfare severance benefits.

Changes in Accumulated Other 38

Changes in Accumulated Other Comprehensive Income (Tables)	6 Months Ended
	Jun. 30, 2017
Changes in Accumulated Other Comprehensive Income [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following tables present changes in accumulated other comprehensive income (loss) (AOCI) by component for the six months ended June 30, 2017 and 2016 : Six Months Ended June 30, 2017 Gains 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 1 2 (58 ) 3 5 (47 ) Amounts reclassified from AOCI (b) 4 — 70 — — 74 Net current-period OCI 5 2 12 3 5 27 Ending balance $ (12 ) $ 6 $ (2,598 ) $ (27 ) $ (2 ) $ (2,633 ) Generation (a) Beginning balance $ (19 ) $ 2 $ — $ (30 ) $ (7 ) $ (54 ) OCI before reclassifications 1 — — 3 6 10 Amounts reclassified from AOCI (b) 4 — — — — 4 Net current-period OCI 5 — — 3 6 14 Ending balance $ (14 ) $ 2 $ — $ (27 ) $ (1 ) $ (40 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 Six Months Ended June 30, 2016 Gains 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 ) — (2 ) 6 (7 ) (13 ) Amounts reclassified from AOCI (b) 3 — 69 — — 72 Net current-period OCI (7 ) — 67 6 (7 ) 59 Ending balance $ (26 ) $ 3 $ (2,498 ) $ (34 ) $ (10 ) $ (2,565 ) Generation (a) Beginning balance $ (21 ) $ 1 $ — $ (40 ) $ (3 ) $ (63 ) OCI before reclassifications (7 ) — — 6 (4 ) (5 ) Amounts reclassified from AOCI (b) 3 — — — — 3 Net current-period OCI (4 ) — — 6 (4 ) (2 ) Ending balance $ (25 ) $ 1 $ — $ (34 ) $ (7 ) $ (65 ) 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 and six months ended June 30, 2017 and 2016 . Three Months Ended June 30, 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 (losses) on cash flow hedges Other cash flow hedges $ — $ — Interest expense Total before tax — — Tax benefit — — Net of tax $ — $ — 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 24 — Net of tax $ (34 ) $ — Total Reclassifications for the period $ (34 ) $ — Comprehensive income Six Months Ended June 30, 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) $ 46 $ — Actuarial losses (b) (162 ) — Total before tax (116 ) — Tax benefit 46 — Net of tax $ (70 ) $ — Total Reclassifications $ (74 ) $ (4 ) Comprehensive income Three Months Ended June 30, 2016 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statement of Operations and Comprehensive Income Exelon Generation Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 19 $ — Actuarial losses (b) (75 ) — Total before tax (56 ) — Tax benefit 22 — Net of tax $ (34 ) $ — Total Reclassifications for the period $ (34 ) $ — Comprehensive income Six Months Ended June 30, 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 benefit 2 2 — Net of tax $ (3 ) $ (3 ) $ — Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 38 $ — $ — Actuarial losses (b) (151 ) — (1 ) Total before tax (113 ) — (1 ) Tax benefit 44 — — Net of tax $ (69 ) $ — $ (1 ) Total Reclassifications $ (72 ) $ (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 and six months ended June 30, 2017 and 2016 : Three Months Ended June 30, Six Months Ended 2017 2016 2017 2016 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 9 $ 7 $ 18 $ 15 Actuarial loss reclassified to periodic benefit cost (32 ) (30 ) (64 ) (60 ) Pension and non-pension postretirement benefit plans valuation adjustment 1 — 3 1 Change in unrealized (loss)/gain on cash flow hedges (2 ) 2 (3 ) 4 Change in unrealized (loss)/gain on equity investments — 1 (3 ) 3 Change in unrealized (loss)/gain on marketable securities — (1 ) (1 ) — Total $ (24 ) $ (21 ) $ (50 ) $ (37 ) Generation Change in unrealized (loss)/gain on cash flow hedges $ (2 ) $ 1 $ (3 ) $ 3 Change in unrealized (loss)/gain on equity investments — 1 (2 ) 3 Total $ (2 ) $ 2 $ (5 ) $ 6 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 Equity39

Earnings Per Share and Equity (Tables)	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Reconciliation of basic and diluted earnings per share	Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Exelon Net income attributable to common shareholders $ 80 $ 267 $ 1,076 $ 440 Weighted average common shares outstanding — basic 934 924 931 923 Assumed exercise and/or distributions of stock-based awards 2 2 1 3 Weighted average common shares outstanding — diluted 936 926 932 926

Commitments and Contingencies40

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2017
Commitments And Contingencies Tables Disclosure [Line Items]
Commercial Commitments	The Registrants’ commercial commitments as of June 30, 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) $ 1,326 $ 1,243 $ 14 $ 23 $ 2 $ 1 $ 1 $ — $ — Surety bonds (b) 1,113 1,014 12 18 11 21 13 4 4 Financing trust guarantees 628 — 200 178 250 — — — — Guaranteed lease residual values (c) 19 — — — — 19 6 7 5 Total commercial commitments $ 3,086 $ 2,257 $ 226 $ 219 $ 263 $ 41 $ 20 $ 11 $ 9 ________ (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 June 30, 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: June 30, 2017 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 412 $ 315 Generation 67 — ComEd 284 282 PECO 32 31 BGE 3 2 PHI (Successor) 26 — Pepco 23 — 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 (remainder of year) $ 8 2018 7 2019 3 Total $ 18

Supplemental Financial Inform41

Supplemental Financial Information (Tables)	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 2017 and 2016 . Three Months Ended June 30, 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 $ 211 $ 211 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 74 74 — — — — — — — Net unrealized (losses) gains on decommissioning trust funds Regulatory agreement units (13 ) (13 ) — — — — — — — Non-regulatory agreement units 70 70 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (2 ) (2 ) — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (160 ) (160 ) — — — — — — — Total decommissioning-related activities 180 180 — — — — — — — Investment income 2 1 — — — — — — — Interest expense related to uncertain income tax positions (1 ) — — — — — — — — Penalty related to uncertain income tax positions 1 — — — — — — — — AFUDC — Equity 17 — 2 2 4 9 5 2 2 Other 6 — 2 — — 4 2 1 — Other, net $ 205 $ 181 $ 4 $ 2 $ 4 $ 13 $ 7 $ 3 $ 2 Six Months Ended June 30, 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 $ 280 $ 280 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 106 106 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 210 210 — — — — — — Non-regulatory agreement units 235 235 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (2 ) (2 ) — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (396 ) (396 ) — — — — — — — Total decommissioning-related activities 433 433 — — — — — — — Investment income (expense) 4 3 — (1 ) — 1 1 — — Penalty income related to uncertain income tax positions 2 — — — — — — — — AFUDC — Equity 33 — 4 4 8 17 11 3 3 Other 16 4 4 — — 8 3 3 1 Other, net $ 488 $ 440 $ 8 $ 3 $ 8 $ 26 $ 15 $ 6 $ 4 Three Months Ended June 30, 2016 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 $ 90 $ 90 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 39 39 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 52 52 — — — — — — — Non-regulatory agreement units 48 48 — — — — — — — Net unrealized gains on pledged assets Zion Station decommissioning 1 1 — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (117 ) (117 ) — — — — — — — Total decommissioning-related activities 113 113 — — — — — — — Investment income 6 5 — — — — — — — Interest income related to uncertain income tax positions 4 — — — — — — — — AFUDC — Equity 15 — 1 2 5 7 5 1 1 Other 6 (1 ) 2 — — 4 1 2 1 Other, net $ 144 $ 117 $ 3 $ 2 $ 5 $ 11 $ 6 $ 3 $ 2 Successor Predecessor Six Months Ended June 30, 2016 March 24, 2016 to June 30, 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 $ 122 $ 122 $ — $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 61 61 — — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 131 131 — — — — — — — — Non-regulatory agreement units 100 100 — — — — — — — — Net unrealized gains on pledged assets Zion Station decommissioning 3 3 — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (211 ) (211 ) — — — — — — — — Total decommissioning-related activities 206 206 — — — — — — — — Investment income (expense) 12 5 — (1 ) 2 — — — — — Long-term lease income 4 — — — — — — — — — Interest income related to uncertain income tax positions 5 — — — — 1 — 1 — — AFUDC — Equity 24 — 3 4 9 9 2 3 8 7 Loss on debt extinguishment (3 ) (2 ) — — — — — — — — Other 10 1 4 1 — 4 4 1 4 (11 ) Other, net $ 258 $ 210 $ 7 $ 4 $ 11 $ 14 $ 6 $ 5 $ 12 $ (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.
Schedule Of Taxes Excluding Income And Excise Taxes [Text Block]	The following utility taxes are included in revenues and expenses for the three and six months ended June 30, 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 June 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 213 $ 30 $ 57 $ 29 $ 21 $ 76 $ 72 $ 4 $ — Six Months Ended June 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 438 $ 63 $ 116 $ 60 $ 47 $ 152 $ 143 $ 9 $ — Three Months Ended June 30, 2016 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 217 $ 27 $ 60 $ 32 $ 21 $ 77 $ 73 $ 4 $ — Successor Predecessor Six Months Ended June 30, 2016 March 24, 2016 to June 30, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Utility taxes $ 369 $ 55 $ 119 $ 66 $ 45 $ 152 $ 9 $ — $ 84 $ 77
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 six months ended June 30, 2017 and 2016 . Six Months Ended June 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Depreciation, amortization and accretion Property, plant and equipment (a) $ 1,545 $ 612 $ 384 $ 129 $ 155 $ 227 $ 101 $ 61 $ 44 Amortization of regulatory assets (a) 238 — 35 12 84 105 59 18 28 Amortization of intangible assets, net (a) 28 25 — — — — — — — Amortization of energy contract assets and liabilities (b) 20 20 — — — — — — — Nuclear fuel (c) 529 529 — — — — — — — ARO accretion (d) 231 229 — — — — — — — Total depreciation, amortization and accretion $ 2,591 $ 1,415 $ 419 $ 141 $ 239 $ 332 $ 160 $ 79 $ 72 Successor Predecessor Six Months Ended June 30, 2016 March 24, 2016 to June 30, 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) $ 1,432 $ 674 $ 345 $ 121 $ 150 $ 85 $ 55 $ 40 $ 111 $ 94 Amortization of regulatory assets (a) 166 — 34 13 56 59 21 41 63 58 Amortization of intangible assets, net (a) 28 23 — — — — — — — — Amortization of energy contract assets and liabilities (b) (7 ) (7 ) — — — — — — — — Nuclear fuel (c) 557 557 — — — — — — — — ARO accretion (d) 220 220 — — — — — — — — Total depreciation, amortization and accretion $ 2,396 $ 1,467 $ 379 $ 134 $ 206 $ 144 $ 76 $ 81 $ 174 $ 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	Six Months Ended June 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 320 $ 113 $ 87 $ 14 $ 31 $ 48 $ 13 $ 6 $ 7 Loss from equity method investments 19 19 — — — — — — — Provision for uncollectible accounts 52 19 15 9 3 6 4 — 2 Stock-based compensation costs 57 — — — — — — — — Other decommissioning-related activity (a) (144 ) (144 ) — — — — — — — Energy-related options (b) 11 11 — — — — — — — Amortization of regulatory asset related to debt costs 4 — 2 — — 2 1 1 — Amortization of rate stabilization deferral (8 ) — — — 7 (15 ) (10 ) (5 ) — Amortization of debt fair value adjustment (9 ) (6 ) — — — (3 ) — — — Discrete impacts from EIMA and FEJA (c) (51 ) — (51 ) — — — — — — Amortization of debt costs 49 30 2 1 1 — — — — Provision for excess and obsolete inventory 51 49 1 — — 1 — — — Merger-related commitments (d) — — — — — (8 ) (6 ) (2 ) — Severance costs 25 17 — — — 3 — — — Other 39 13 2 (2 ) (7 ) (6 ) (2 ) (3 ) (2 ) Total other non-cash operating activities $ 415 $ 121 $ 58 $ 22 $ 35 $ 28 $ — $ (3 ) $ 7 Non-cash investing and financing activities: Change in capital expenditures not paid $ (105 ) $ 48 $ (82 ) $ (44 ) $ 6 $ (8 ) $ — $ 15 $ (14 ) Fair value of pension obligation transferred in connection with the FitzPatrick acquisition — 49 — — — — — — — Change in PPE related to ARO update 103 103 — — — — — — — Indemnification of like-kind exchange position (g) — — 23 — — — — — — Non-cash financing of capital projects 13 13 — — — — — — — Dividends on stock compensation 3 — — — — — — — — — Loss on reissuance of treasury stock 1,054 — — — — — — — — Successor Predecessor Six Months Ended June 30, 2016 March 24, 2016 to June 30, 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 $ 297 $ 109 $ 83 $ 17 $ 33 $ 16 $ 9 $ 8 $ 31 $ 23 Loss from equity method investments 10 11 — — — — — — — — Provision for uncollectible accounts 51 13 18 10 3 8 8 10 7 16 Stock-based compensation costs 67 — — — — — — — — 3 Other decommissioning-related activity (a) (123 ) (123 ) — — — — — — — — Energy-related options (b) (17 ) (17 ) — — — — — — — — Amortization of regulatory asset related to debt costs 4 — 2 1 — 1 — — 1 1 Amortization of rate stabilization deferral 34 — — — 34 (2 ) 2 — — 5 Amortization of debt fair value adjustment (6 ) (6 ) — — — — — — — — Discrete impacts from EIMA (c) (21 ) — (21 ) — — — — — — — Amortization of debt costs 14 10 2 1 2 — — — — — Provision for excess and obsolete inventory 68 66 2 — — 1 1 1 — 1 Merger-related commitments (d)(e) 503 3 — — — 138 100 120 358 — Severance costs 122 50 — — — — — — 54 — Asset retirement costs — — — — — — 4 2 — — Lower of cost or net realizable value inventory adjustment 36 36 — — — — — — — — Other 17 17 (3 ) (2 ) (12 ) (4 ) (3 ) (3 ) (7 ) (3 ) Total other non-cash operating activities $ 1,056 $ 169 $ 83 $ 27 $ 60 $ 158 $ 121 $ 138 $ 444 $ 46 Non-cash investing and financing activities: Change in capital expenditures not paid $ (364 ) $ (317 ) $ (21 ) $ (12 ) $ 2 $ 11 $ (9 ) $ 6 $ (4 ) $ 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 — — — — — — — — 53 — Assumption of member purchase liability — — — — — — — — 29 — Assumption of merger commitment liability — — — — — 33 — — 33 — Change in PPE related to ARO update 471 471 — — — — — — — — Indemnification of like-kind exchange position (g) — — 5 — — — — — — — Non-cash financing of capital projects 60 60 — — — — — — — — Dividends on stock compensation 2 — — — — — — — — — ________ (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 and FEJA, which allows for the recovery of distribution costs by a utility through a pre-established performance-based formula rate tariff. Beginning June 1, 2017, also reflects the change in energy efficiency rates pursuant to FEJA, which allows for the recovery of energy efficiency 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 June 30, 2017 and December 31, 2016 . Successor June 30, 2017 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Property, plant and equipment: Accumulated depreciation and amortization $ 19,735 (a) $ 10,550 (a) $ 4,122 $ 3,330 $ 3,358 $ 360 $ 3,131 $ 1,212 $ 1,042 Accounts receivable: Allowance for uncollectible accounts $ 322 $ 102 $ 71 $ 59 $ 26 $ 64 $ 25 $ 19 $ 20 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 $3,016 million . (b) Includes accumulated amortization of nuclear fuel in the reactor core of $3,186 million

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2017
Segment Reporting [Abstract]
Analysis and reconciliation of reportable segment information	Six Months Ended June 30, 2017 and 2016 Successor Generation (a) ComEd PECO BGE PHI (b) Other (c) Intersegment Exelon Operating revenues (d) : 2017 Competitive businesses electric revenues $ 7,437 $ — $ — $ — $ — $ — $ (592 ) $ 6,845 Competitive businesses natural gas revenues 1,348 — — — — — — 1,348 Competitive businesses other revenues 276 — — — — — (1 ) 275 Rate-regulated electric revenues — 2,656 1,140 1,237 2,138 1 (16 ) 7,156 Rate-regulated natural gas revenues — — 286 388 87 — (4 ) 757 Shared service and other revenues — — — — 23 870 (893 ) — 2016 Competitive businesses electric revenues $ 7,352 $ — $ — $ — $ — $ — $ (620 ) $ 6,732 Competitive businesses natural gas revenues 1,189 — — — — — — 1,189 Competitive businesses other revenues (212 ) — — — — — (1 ) (213 ) Rate-regulated electric revenues — 2,535 1,232 1,264 1,120 — (15 ) 6,136 Rate-regulated natural gas revenues — — 273 345 28 — (5 ) 641 Shared service and other revenues — — — — 23 803 (826 ) — Intersegment revenues (e) : 2017 $ 594 $ 9 $ 3 $ 8 $ 23 $ 866 $ (1,503 ) $ — 2016 621 8 4 9 23 803 (1,466 ) 2 Net income (loss): 2017 $ 144 $ 259 $ 215 $ 169 $ 205 $ 54 $ — $ 1,046 2016 285 260 224 135 (257 ) (215 ) (2 ) 430 _________ (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 six months ended June 30, 2017 include revenue from sales to PECO of $79 million , sales to BGE of $233 million , sales to Pepco of $152 million , sales to DPL of $91 million , and sales to ACE of $16 million in the Mid-Atlantic region, and sales to ComEd of $23 million in the Midwest region. For the six months ended June 30, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $143 million and sales to BGE of $306 million in the Mid-Atlantic region, and sales to ComEd of $18 million in the Midwest region. For the Successor period of March 24, 2016 to June 30, 2016 , intersegment revenues for Generation include revenue from sales to Pepco of $94 million , sales to DPL of $47 million , and sales to ACE of $13 million in the Mid-Atlantic region. (b) Amounts included represent activity for PHI's successor period, six months ended June 30, 2017 and March 24, 2016 through June 30, 2016 . PHI includes the three reportable segments: Pepco, DPL and ACE. See tables below for PHI's predecessor period, including Pepco, DPL and ACE, for January 1, 2016 to March 23, 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 six months ended June 30, 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) : Six Months Ended June 30, 2017 - Successor Rate-regulated electric revenues $ 1,045 $ 557 $ 544 $ 1 $ (9 ) $ 2,138 Rate-regulated natural gas revenues — 87 — — — 87 Shared service and other revenues — — — 25 (2 ) 23 March 24, 2016 to June 30, 2016 - Successor Rate-regulated electric revenues $ 550 $ 279 $ 293 $ 3 $ (5 ) $ 1,120 Rate-regulated natural gas revenues — 29 — (1 ) — 28 Shared service and other revenues — — — 23 — 23 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: Six Months Ended June 30, 2017 - Successor $ 3 $ 4 $ 1 $ 24 $ (9 ) $ 23 March 24, 2016 to June 30, 2016 - Successor 2 2 1 23 (5 ) 23 January 1, 2016 to March 23, 2016 - Predecessor 1 2 1 — (4 ) — Net income (loss): Six Months Ended June 30, 2017 - Successor $ 101 $ 76 $ 36 $ (31 ) $ 23 $ 205 March 24, 2016 to June 30, 2016 - Successor (92 ) (86 ) (102 ) — 23 (257 ) January 1, 2016 to March 23, 2016 - Predecessor 32 26 5 (44 ) — 19 _________ (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 six months ended June 30, 2017 and 2016 . (b) Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities. For the predecessor period presented, Other includes the activity of PHI’s unregulated businesses which were distributed to Exelon and Generation as a result of the PHI Merger. An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements for the three and six months ended June 30, 2017 and 2016 is as follows: Three Months Ended June 30, 2017 and 2016 Successor Generation (a) ComEd PECO BGE PHI (b) Other (c) Intersegment Exelon Operating revenues (d) : 2017 Competitive businesses electric revenues $ 3,719 $ — $ — $ — $ — $ — $ (266 ) $ 3,453 Competitive businesses natural gas revenues 430 — — — — — — 430 Competitive businesses other revenues 25 — — — — — — 25 Rate-regulated electric revenues — 1,357 550 571 1,040 — (7 ) 3,511 Rate-regulated natural gas revenues — — 80 103 22 — (1 ) 204 Shared service and other revenues — — — — 12 449 (461 ) — 2016 Competitive businesses electric revenues $ 3,655 $ — $ — $ — $ — $ — $ (354 ) $ 3,301 Competitive businesses natural gas revenues 367 — — — — — — 367 Competitive businesses other revenues (433 ) — — — — — (1 ) (434 ) Rate-regulated electric revenues — 1,286 587 584 1,030 — (7 ) 3,480 Rate-regulated natural gas revenues — — 77 96 26 — (2 ) 197 Shared service and other revenues — — — — 10 398 (409 ) (1 ) Intersegment revenues (e) : 2017 $ 266 $ 3 $ 2 $ 3 $ 12 $ 448 $ (734 ) $ — 2016 355 3 2 4 10 398 (771 ) 1 Net income (loss): 2017 $ (266 ) $ 118 $ 88 $ 45 $ 66 $ 13 $ — $ 64 2016 28 145 100 34 52 (52 ) (1 ) 306 Total assets: June 30, 2017 $ 48,130 $ 29,160 $ 11,041 $ 8,786 $ 21,190 $ 10,783 $ (11,986 ) $ 117,104 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 June 30, 2017 include revenue from sales to PECO of $34 million , sales to BGE of $99 million , sales to Pepco of $68 million , sales to DPL of $40 million , and sales to ACE of $7 million in the Mid-Atlantic region, and sales to ComEd of $18 million in the Midwest region. For the three months ended June 30, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $64 million , sales to BGE of $135 million , sales to Pepco of $88 million , sales to DPL of $43 million , and sales to ACE of $12 million in the Mid-Atlantic region, and sales to ComEd of $13 million in the Midwest region. (b) Amounts included represent activity for PHI's successor period, three months ended June 30, 2017 and 2016 . PHI includes the three reportable segments: Pepco, DPL and ACE. (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 June 30, 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 PHI: Pepco DPL ACE Other (b) Intersegment PHI Operating revenues (a) : Three months ended June 30, 2017 - Successor Rate-regulated electric revenues $ 514 $ 260 $ 270 $ — $ (4 ) $ 1,040 Rate-regulated natural gas revenues — 22 — — — 22 Shared service and other revenues — — — 13 (1 ) 12 Three months ended June 30, 2016 - Successor Rate-regulated electric revenues $ 509 $ 255 $ 270 $ — $ (4 ) $ 1,030 Rate-regulated natural gas revenues — 26 — — — 26 Shared service and other revenues — — — 10 — 10 Intersegment revenues: Three months ended June 30, 2017 - Successor $ 1 $ 2 $ 1 $ 13 $ (5 ) $ 12 Three months ended June 30, 2016 - Successor 1 2 1 10 (4 ) 10 Net income (loss): Three months ended June 30, 2017 - Successor $ 43 $ 19 $ 8 $ (16 ) $ 12 $ 66 Three months ended June 30, 2016 - Successor 49 12 3 (22 ) 10 52 Total assets: June 30, 2017 - Successor $ 7,648 $ 4,235 $ 3,478 $ 10,800 $ (4,971 ) $ 21,190 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 June 30, 2017 and 2016 . (b) Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities.
Analysis and reconciliation of reportable segment revenues for Generation	Generation total revenues: Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 Revenues (a) Intersegment Total Revenues (a) Intersegment Total Mid-Atlantic $ 1,356 $ 9 $ 1,365 $ 1,432 $ (16 ) $ 1,416 Midwest 1,058 (8 ) 1,050 1,076 7 1,083 New England 438 (5 ) 433 352 (1 ) 351 New York 352 (5 ) 347 356 (10 ) 346 ERCOT 247 — 247 207 — 207 Other Power Regions 268 (9 ) 259 232 (9 ) 223 Total Revenues for Reportable Segments 3,719 (18 ) 3,701 3,655 (29 ) 3,626 Other (b) 455 18 473 (66 ) 29 (37 ) Total Generation Consolidated Operating Revenues $ 4,174 $ — $ 4,174 $ 3,589 $ — $ 3,589 _ _________ (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 $15 million and $9 million decrease to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the three months ended June 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $143 million and $615 million for the three months ended June 30, 2017 and 2016 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Three Months Ended June 30, 2017 Three Months Ended June 30, 2016 RNF (a) Intersegment RNF Total RNF RNF (a) Intersegment RNF Total RNF Mid-Atlantic $ 757 $ 26 $ 783 $ 830 $ (2 ) $ 828 Midwest 728 — 728 724 4 728 New England 157 (10 ) 147 118 (8 ) 110 New York 230 — 230 270 (3 ) 267 ERCOT 121 (51 ) 70 111 (34 ) 77 Other Power Regions 134 (44 ) 90 123 (27 ) 96 Total Revenues net of purchased power and fuel for Reportable Segments 2,127 (79 ) 2,048 2,176 (70 ) 2,106 Other (b) (110 ) 79 (31 ) (164 ) 70 (94 ) Total Generation Revenues net of purchased power and fuel expense $ 2,017 $ — $ 2,017 $ 2,012 $ — $ 2,012 __________ (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 $20 million and $12 million decrease to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the three months ended June 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $184 million and $304 million for the three months ended June 30, 2017 and 2016 , respectively, and the elimination of intersegment revenue net of purchased power and fuel expense. Generation total revenues: Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 Revenues (a) Intersegment Total Revenues (a) Intersegment Total Mid-Atlantic $ 2,785 $ 5 $ 2,790 $ 2,964 $ (28 ) $ 2,936 Midwest 2,107 (5 ) 2,102 2,166 13 2,179 New England 987 (7 ) 980 823 (2 ) 821 New York 662 (8 ) 654 573 (24 ) 549 ERCOT 439 (1 ) 438 370 — 370 Other Power Regions 457 (14 ) 443 456 (9 ) 447 Total Revenues for Reportable Segments 7,437 (30 ) 7,407 7,352 (50 ) 7,302 Other (b) 1,624 30 1,654 977 50 1,027 Total Generation Consolidated Operating Revenues $ 9,061 $ — $ 9,061 $ 8,329 $ — $ 8,329 _ _________ (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 $17 million decrease to revenues and an $11 million increase to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the six months ended June 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $98 million and $553 million for the six months ended June 30, 2017 and 2016 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Six Months Ended June 30, 2017 Six Months Ended June 30, 2016 RNF from external customers (a) Intersegment RNF Total RNF RNF from external customers (a) Intersegment RN Total RNF Mid-Atlantic $ 1,513 $ 44 $ 1,557 $ 1,661 $ 8 $ 1,669 Midwest 1,431 12 1,443 1,443 6 1,449 New England 271 (14 ) 257 204 (13 ) 191 New York 385 — 385 408 (13 ) 395 ERCOT 214 (76 ) 138 192 (54 ) 138 Other Power Regions 240 (88 ) 152 211 (37 ) 174 Total Revenues net of purchased power and fuel expense for Reportable Segments 4,054 (122 ) 3,932 4,119 (103 ) 4,016 Other (b) 52 122 174 190 103 293 Total Generation Revenues net of purchased power and fuel expense $ 4,106 $ — $ 4,106 $ 4,309 $ — $ 4,309 __________ (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 $22 million decrease to RNF and a $7 million increase to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the six months ended June 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $233 million and $201 million for the six months ended June 30, 2017 and 2016 , respectively, and the elimination of intersegment revenue net of purchased power and fuel expense.

Significant Accounting Polici43

Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Mar. 31, 2017	Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017	Jun. 30, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities				$ 2,898	$ 4,553
Quantifying Misstatement in Current Year Financial Statements, Amount	$ (127)
Net Cash Provided by (Used in) Investing Activities				(3,980)	(10,877)
Scenario, Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities	1,074
Net Cash Provided by (Used in) Investing Activities	2,284
Exelon Generation Co L L C [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities				974	2,387
Quantifying Misstatement in Current Year Financial Statements, Amount	(320)
Net Cash Provided by (Used in) Investing Activities				(1,357)	(2,210)
Exelon Generation Co L L C [Member] | Scenario, Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities	420
Net Cash Provided by (Used in) Investing Activities	892
Commonwealth Edison Co [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities				788	1,128
Quantifying Misstatement in Current Year Financial Statements, Amount	91
Net Cash Provided by (Used in) Investing Activities				(1,166)	(1,313)
Commonwealth Edison Co [Member] | Scenario, Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities	236
Net Cash Provided by (Used in) Investing Activities	620
PECO Energy Co [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities				368	339
Quantifying Misstatement in Current Year Financial Statements, Amount	42
Net Cash Provided by (Used in) Investing Activities				(242)	(291)
PECO Energy Co [Member] | Scenario, Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities	106
Net Cash Provided by (Used in) Investing Activities	69
Baltimore Gas and Electric Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities				472	489
Quantifying Misstatement in Current Year Financial Statements, Amount	40
Net Cash Provided by (Used in) Investing Activities				(383)	(375)
Baltimore Gas and Electric Company [Member] | Scenario, Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities	208
Net Cash Provided by (Used in) Investing Activities	$ 221
Pepco Holdings LLC [Member] | Predecessor [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities			$ 264
Net Cash Provided by (Used in) Investing Activities			$ (343)
Pepco Holdings LLC [Member] | Successor [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities		$ 188		403
Net Cash Provided by (Used in) Investing Activities		$ (350)		(667)
Delmarva Power and Light Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities				194	220
Net Cash Provided by (Used in) Investing Activities				(191)	(180)
Atlantic City Electric Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities				77	208
Net Cash Provided by (Used in) Investing Activities				(173)	(160)
Potomac Electric Power Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net Cash Provided by (Used in) Operating Activities				129	365
Net Cash Provided by (Used in) Investing Activities				$ (293)	$ (307)

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details)		3 Months Ended		6 Months Ended
		Jun. 30, 2017USD ($)VIE	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)VIE	Jun. 30, 2016USD ($)	Dec. 31, 2016USD ($)VIE	Apr. 01, 2014USD ($)
Variable Interest Entity [Line Items]
Number Of Variable Interest Entities Consolidated | VIE		7		7		9
Number of Variable Interest Entities not consolidated by equity holders | VIE		7		7		8
Other Nonconsolidated Variable Interest Entity Ownership Interests	[1]	$ 609,000,000		$ 609,000,000		$ 455,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted		48,000,000		48,000,000
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount		16,000,000		16,000,000
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Other Nonconsolidated Variable Interest Entity Ownership Interests	[1]	577,000,000		577,000,000		423,000,000
Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Other Nonconsolidated Variable Interest Entity Ownership Interests	[1]	32,000,000		32,000,000		$ 32,000,000
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Other Nonconsolidated Variable Interest Entity Ownership Interests		16,000,000		16,000,000
Variable Interest Entity, Financial or Other Support, Amount				30,000,000
Guarantor Obligations, Current Carrying Value		75,000,000		$ 75,000,000
Guarantor Obligations, Liquidation Proceeds, Percentage				49.99%
Related Party Purchase Of Nuclear Output By Third Party Percentage				50.01%
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		$ 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		8,000,000
Baltimore Gas and Electric Company [Member] | RSB Bond Co LLC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Financial or Other Support, Amount		3,000,000	$ 21,000,000	22,000,000	$ 42,000,000
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		13,000,000		13,000,000
Atlantic City Electric Company [Member] | ATF [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Financial or Other Support, Amount		8,000,000	$ 12,000,000	27,000,000	$ 26,000,000
Distributed Energy Company [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests		227,000,000		227,000,000
Constellation Energy Nuclear Group [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Receivables from affiliates		324,000,000		324,000,000			$ 400,000,000
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		637,000,000
Payment Guarantee [Member] | Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value		$ 275,000,000		$ 275,000,000
Payment Guarantee [Member] | Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted							245,000,000
Financial Guarantee [Member] | Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted							$ 165,000,000
[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.

Variable Interest Entities - Ca

Variable Interest Entities - Carrying Amounts and Classification of Consolidated VIE Assets and Liabilities (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Consolidated VIE Assets	[1],[2]	$ 9,129	$ 9,517
Consolidated VIE Liabilities	[1],[2]	3,296	3,598
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		9,086	9,441
Consolidated VIE Liabilities		3,175	3,414
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets			26
Consolidated VIE Liabilities			42
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets	[1]	43	49
Consolidated VIE Liabilities	[1]	121	143
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		30	32
Consolidated VIE Liabilities		108	126
CurrentAssetsMember [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets	[1],[2]	512	954
CurrentAssetsMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		501	916
CurrentAssetsMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets			23
CurrentAssetsMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets	[1]	11	14
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	[1],[2]	8,617	8,563
NoncurrentAssetMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets		8,585	8,525
NoncurrentAssetMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets			3
NoncurrentAssetMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Assets	[1]	32	35
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	[1],[2]	573	885
CurrentLiabilityMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		535	802
CurrentLiabilityMember [Member] | Baltimore Gas and Electric Company [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	[1]	38	42
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	[1],[2]	2,723	2,713
NoncurrentLiabilityMember [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		2,640	2,612
NoncurrentLiabilityMember [Member] | Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities			0
NoncurrentLiabilityMember [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities	[1]	83	101
NoncurrentLiabilityMember [Member] | Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Consolidated VIE Liabilities		$ 74	$ 89
[1]	Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity.
[2]	Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity.

Variable Interest Entities - As

Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 23, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 536	$ 635	$ 1,647		$ 6,502
Restricted cash		252	253
Accounts receivable, net
Customer		3,825	4,158
Other		958	1,201
Mark-to-market derivatives assets		833	917
Inventory
Materials and supplies		1,267	1,274
Other current assets		1,600	930
Total current assets		12,232	12,412
Property, plant and equipment, net		72,748	71,555
Nuclear decommissioning trust funds		12,641	11,061
Goodwill		6,677	6,677
Mark-to-market derivative assets		464	492
Other noncurrent assets		1,265	1,472
Total Deferred Debits And Other Assets		32,124	30,937
Total assets		117,104	114,904
Long-term debt due within one year		3,619	2,430
Accounts payable		3,134	3,441
Accrued expenses		2,878	3,460
Mark-to-market derivative liabilities (current liabilities)		244	282
Unamortized energy contract liabilities		340	407
Other		977	981
Total current liabilities		13,965	13,457
Long-term debt		30,315	31,575
Asset retirement obligations		9,848	9,111
Pension obligation(c)		4,082	4,248
Unamortized energy contract liabilities		705	830
Other noncurrent liabilities		1,828	1,827
Total liabilities	[1]	87,814	87,292
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents	[2],[3]	68	150
Restricted cash	[2],[3]	55	59
Accounts receivable, net
Customer	[2],[3]	106	371
Other	[2],[3]	24	48
Mark-to-market derivatives assets	[2],[3]	0	31
Inventory
Materials and supplies	[2],[3]	193	199
Other current assets	[2],[3]	38	50
Total current assets	[2],[3]	484	908
Property, plant and equipment, net	[2],[3]	5,293	5,415
Nuclear decommissioning trust funds	[2],[3]	2,341	2,185
Goodwill	[2],[3]	0	47
Mark-to-market derivative assets	[2],[3]	0	23
Other noncurrent assets	[2],[3]	267	315
Total noncurrent assets	[2],[3]	7,901	7,985
Total assets	[2],[3]	8,385	8,893
Long-term debt due within one year	[2],[3]	191	181
Accounts payable	[2],[3]	80	269
Accrued expenses	[2],[3]	48	119
Mark-to-market derivative liabilities (current liabilities)	[2],[3]	0	60
Unamortized energy contract liabilities	[2],[3]	16	15
Other	[2],[3]	5	30
Total current liabilities	[2],[3]	340	674
Long-term debt	[2],[3]	616	641
Asset retirement obligations	[2],[3]	1,954	1,904
Pension obligation(c)	[2],[3],[4]	0	9
Unamortized energy contract liabilities	[2],[3]	13	22
Other noncurrent liabilities	[2],[3]	98	106
Total noncurrent liabilities	[2],[3]	2,681	2,682
Total liabilities	[2],[3]	3,021	3,356
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		265	290	373		431
Restricted cash		166	158
Accounts receivable, net
Customer		2,242	2,433
Other		447	558
Mark-to-market derivatives assets		833	917
Inventory
Materials and supplies		901	935
Other current assets		1,241	701
Total current assets		6,594	6,528
Property, plant and equipment, net		25,261	25,585
Nuclear decommissioning trust funds		12,641	11,061
Goodwill		47	47
Mark-to-market derivative assets		453	476
Other noncurrent assets		620	688
Total Deferred Debits And Other Assets		16,275	14,861
Total assets		48,130	46,974
Long-term debt due within one year		1,828	1,117
Accounts payable		1,527	1,610
Accrued expenses		722	989
Mark-to-market derivative liabilities (current liabilities)		225	263
Unamortized energy contract liabilities		61	72
Other		294	313
Total current liabilities		6,064	5,683
Long-term debt		7,010	7,202
Asset retirement obligations		9,655	8,922
Unamortized energy contract liabilities		67	80
Other noncurrent liabilities		598	595
Total liabilities	[5]	35,000	33,718
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		68	150
Restricted cash		48	27
Accounts receivable, net
Customer		106	371
Other		24	48
Mark-to-market derivatives assets		0	31
Inventory
Materials and supplies		193	199
Other current assets		34	44
Total current assets		473	870
Property, plant and equipment, net		5,293	5,415
Nuclear decommissioning trust funds		2,341	2,185
Goodwill		0	47
Mark-to-market derivative assets		0	23
Other noncurrent assets		235	277
Total noncurrent assets		7,869	7,947
Total assets		8,342	8,817
Long-term debt due within one year		154	99
Accounts payable		80	269
Accrued expenses		47	116
Mark-to-market derivative liabilities (current liabilities)		0	60
Unamortized energy contract liabilities		16	15
Other		5	30
Total current liabilities		302	589
Long-term debt		533	540
Asset retirement obligations		1,954	1,904
Pension obligation(c)	[4]	0	9
Unamortized energy contract liabilities		13	22
Other noncurrent liabilities		98	106
Total noncurrent liabilities		2,598	2,581
Total liabilities		2,900	3,170
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		12	23	5		9
Restricted cash		6	24
Accounts receivable, net
Customer		312	395
Other		75	102
Inventory
Materials and supplies		42	38
Other current assets		4	7
Total current assets		680	842
Property, plant and equipment, net		7,283	7,040
Other noncurrent assets		5	9
Total Deferred Debits And Other Assets		823	822
Total assets	[6]	8,786	8,704
Long-term debt due within one year		0	41
Accounts payable		205	205
Accrued expenses		100	175
Other		21	26
Total current liabilities		640	707
Long-term debt		2,282	2,281
Asset retirement obligations		22	21
Other noncurrent liabilities		59	61
Total liabilities	[6]	5,868	5,856
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents			0
Restricted cash			23
Accounts receivable, net
Customer			0
Other			0
Mark-to-market derivatives assets			0
Inventory
Materials and supplies			0
Other current assets			0
Total current assets			23
Property, plant and equipment, net			0
Nuclear decommissioning trust funds			0
Goodwill			0
Mark-to-market derivative assets			0
Other noncurrent assets			3
Total noncurrent assets			3
Total assets			26
Long-term debt due within one year			41
Accounts payable			0
Accrued expenses			1
Mark-to-market derivative liabilities (current liabilities)			0
Unamortized energy contract liabilities			0
Other			0
Total current liabilities			42
Long-term debt			0
Asset retirement obligations			0
Pension obligation(c)	[4]		0
Unamortized energy contract liabilities			0
Other noncurrent liabilities			0
Total noncurrent liabilities			0
Total liabilities			42
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		151	170	294	$ 319
Restricted cash		40	43
Accounts receivable, net
Customer		484	496
Other		199	283
Mark-to-market derivatives assets		0	0
Inventory
Materials and supplies		134	116
Other current assets		86	71
Total current assets		1,706	1,838
Property, plant and equipment, net		12,014	11,598
Goodwill		4,005	4,005
Mark-to-market derivative assets		0	0
Other noncurrent assets		79	81
Total Deferred Debits And Other Assets		7,470	7,589
Total assets	[7]	21,190	21,025
Long-term debt due within one year		160	253
Accounts payable		415	458
Accrued expenses		259	272
Mark-to-market derivative liabilities (current liabilities)		0	0
Unamortized energy contract liabilities		279	335
Other		36	47
Total current liabilities		1,562	2,284
Long-term debt		5,792	5,645
Asset retirement obligations		14	14
Unamortized energy contract liabilities		638	750
Other noncurrent liabilities		213	249
Total liabilities		12,349	13,009
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents	[2]	0	0
Restricted cash	[2]	7	9
Accounts receivable, net
Customer	[2]	0	0
Other	[2]	0	0
Mark-to-market derivatives assets	[2]	0	0
Inventory
Materials and supplies	[2]	0	0
Other current assets	[2]	4	5
Total current assets	[2]	11	14
Property, plant and equipment, net	[2]	0	0
Nuclear decommissioning trust funds	[2]	0	0
Goodwill	[2]	0	0
Mark-to-market derivative assets	[2]	0	0
Other noncurrent assets	[2]	32	35
Total noncurrent assets	[2]	32	35
Total assets	[2]	43	49
Long-term debt due within one year	[2]	37	40
Accounts payable	[2]	0	0
Accrued expenses	[2]	1	2
Mark-to-market derivative liabilities (current liabilities)	[2]	0	0
Unamortized energy contract liabilities	[2]	0	0
Other	[2]	0	0
Total current liabilities	[2]	38	42
Long-term debt	[2]	83	101
Asset retirement obligations	[2]	0	0
Pension obligation(c)	[2],[4]	0	0
Unamortized energy contract liabilities	[2]	0	0
Other noncurrent liabilities	[2]	0	0
Total noncurrent liabilities	[2]	83	101
Total liabilities	[2]	121	143
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		7	101	$ 151		$ 3
Restricted cash		7	9
Accounts receivable, net
Customer		103	125
Other		46	44
Inventory
Materials and supplies		25	22
Other current assets		4	2
Total current assets		318	399
Property, plant and equipment, net		2,628	2,521
Other noncurrent assets		43	44
Total Deferred Debits And Other Assets		532	537
Total assets	[8]	3,478	3,457
Long-term debt due within one year		33	35
Accounts payable		122	132
Accrued expenses		56	38
Other		8	8
Total current liabilities		356	320
Long-term debt		1,105	1,120
Other noncurrent liabilities		23	32
Total liabilities		2,430	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
Mark-to-market derivatives assets		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
Mark-to-market derivative assets		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
Unamortized energy contract liabilities		0	0
Other		0	0
Total current liabilities		34	37
Long-term debt		74	89
Asset retirement obligations		0	0
Pension obligation(c)	[4]	0	0
Unamortized energy contract liabilities		0	0
Other noncurrent liabilities		0	0
Total noncurrent liabilities		74	89
Total liabilities		$ 108	$ 126
[1]	Exelon’s consolidated assets include $8,385 million and $8,893 million at June 30, 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 $3,021 million and $3,356 million at June 30, 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 certain purchase accounting adjustments not pushed down to the ACE standalone entity.
[3]	Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity.
[4]	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.
[5]	Generation’s consolidated assets include $8,342 million and $8,817 million at June 30, 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 $2,900 million and $3,170 million at June 30, 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.
[6]	BGE’s consolidated assets include $26 million at December 31, 2016 of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $42 million at December 31, 2016 of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. BGE has no interests in any VIEs as of June 30, 2017. See Note 3 - Variable Interest Entities.
[7]	PHI’s consolidated total assets include $43 million and $49 million at June 30, 2017 and December 31, 2016, respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $121 million and $143 million at June 30, 2017 and December 31, 2016, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 3 - Variable Interest Entities.
[8]	ACE’s consolidated total assets include $30 million and $32 million at June 30, 2017 and December 31, 2016, respectively, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $108 million and $126 million at June 30, 2017 and December 31, 2016, respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 3 - Variable Interest Entities.

Variable Interest Entities - Su

Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Total assets	[1]	$ 1,170	$ 1,205
Total liabilities	[1]	293	502
Exelon's ownership interest in VIE	[1]	268	248
Other ownership interests in VIE	[1]	609	455
Registrants' maximum exposure to loss		16
Pledged assets for Zion Station decommissioning		75	113
Investments [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		268	264
Finite-Lived Intangible Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Debt [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	3
Other Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	6	9
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	641	638
Total liabilities	[1]	64	215
Exelon's ownership interest in VIE	[1]	0	0
Other ownership interests in VIE	[1]	577	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] | Finite-Lived Intangible Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
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] | Other Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	6	9
Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	529	567
Total liabilities	[1]	229	287
Exelon's ownership interest in VIE	[1]	268	248
Other ownership interests in VIE	[1]	32	32
Equity Investment VIE [Member] | Investments [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		268	264
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] | Debt [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	3
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]
Other ownership interests in VIE		16
Pledged assets for Zion Station decommissioning		75	113
Payable to Zion Solutions	[3]	$ 69	$ 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 $75 million and $113 million as of June 30, 2017 and December 31, 2016, respectively; offset by payables to ZionSolutions LLC of $69 million and $104 million as of June 30, 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		May 02, 2016USD ($)	Apr. 21, 2016USD ($)	Mar. 23, 2016USD ($)	Jun. 30, 2017USD ($)MW	Jun. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)MW	Jun. 30, 2016USD ($)	Dec. 31, 2016USD ($)	Mar. 24, 2016USD ($)$ / shares
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross								$ 212	$ 6,642
Business Combination, Bargain Purchase, Gain Recognized, Amount					$ 0	$ 0		226	0
Business Combination, Integration Related Costs	[1],[2]				8	1		17	103
Other Commitment					3,086			3,086
Impairment of Long-Lived Assets to be Disposed of								418
Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross				$ 7,142
Other Commitment					$ 513			513		$ 513
Cash offered in exchange for each share of PHI stock | $ / shares											$ 27.25
Goodwill				4,005
Business Combination, Contingent Consideration, Asset											$ 235
Pepco Holdings LLC [Member] | Other Intangible Assets [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired								$ 1,500
Pepco Holdings LLC [Member] | Other Solar Projects [Member]
Business Acquisition [Line Items]
OtherNonFinancialCommitment1 | MW					27			37
Pepco Holdings LLC [Member] | Wind Assets [Member]
Business Acquisition [Line Items]
OtherNonFinancialCommitment1 | MW								100
Pepco Holdings LLC [Member] | Commitment Adjustment [Member]
Business Acquisition [Line Items]
Other Commitment					$ 8			$ 8
Pepco Holdings LLC [Member] | Net present value [Member]
Business Acquisition [Line Items]
Other Commitment										444
Pepco Holdings LLC [Member] | Other commitments [Member]
Business Acquisition [Line Items]
Other Investments					137			137
Fitzpatrick [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred								293
Business Combination, Bargain Purchase, Gain Recognized, Amount								226
Fitzpatrick [Member] | Cash and Cash Equivalents [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred								110
Business Combination, Consideration Transferred, Other								129
Fitzpatrick [Member] | Nuclear Fuel [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Other								54
Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross								212	1
Business Combination, Bargain Purchase, Gain Recognized, Amount					0	0		226	0
Business Combination, Integration Related Costs	[2]				4	4		13	20
Other Commitment					2,257			2,257
Members' Capital					9,308			9,308		9,261
Gain (Loss) on Disposition of Property Plant Equipment			$ 32
Exelon Generation Co L L C [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Business Combination, Contingent Consideration, Asset											163
Exelon Generation Co L L C [Member] | Fitzpatrick [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred								293
Business Combination, Consideration Transferred, Other								183
Payments to Acquire Businesses, Gross								293
Business Combination, Integration Related Costs					16			47
Exelon Generation Co L L C [Member] | Fitzpatrick [Member] | Cash and Cash Equivalents [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred								110
Payments to Acquire Businesses, Gross								239
Exelon Generation Co L L C [Member] | Fitzpatrick [Member] | Nuclear Fuel [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross								54
Pepco Holdings LLC [Member] | Scenario, Adjustment [Member]
Business Acquisition [Line Items]
Fresh-Start Adjustment, Increase (Decrease), Deferred Income Tax Liabilities, Noncurrent											59
Pepco Holdings LLC [Member] | Successor [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross							$ 33
Business Combination, Integration Related Costs	[2],[3]				2	(1)	55
Members' Capital					8,828			8,828		$ 8,077	$ 7,200
Pepco Holdings LLC [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					315			315
Potomac Electric Power Company [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross									33
Business Combination, Integration Related Costs	[2],[4]				1	(4)		2	23
Other Commitment					20			20
Goodwill					1,700			1,700
Gain (Loss) on Disposition of Property Plant Equipment		$ 8
Potomac Electric Power Company [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					120			120
Potomac Electric Power Company [Member] | Pepco Holdings LLC [Member] | Commitment Adjustment [Member]
Business Acquisition [Line Items]
Other Commitment					6			6
Potomac Electric Power Company [Member] | Pepco Holdings LLC [Member] | Other commitments [Member]
Business Acquisition [Line Items]
Other Additional Capital						73	73		73
Delmarva Power and Light Company [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs	[2],[5]				0	0		(7)	16
Other Commitment					11			11
Goodwill					1,100			1,100
Delmarva Power and Light Company [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					84			84
Delmarva Power and Light Company [Member] | Pepco Holdings LLC [Member] | Commitment Adjustment [Member]
Business Acquisition [Line Items]
Other Commitment					2			2
Delmarva Power and Light Company [Member] | Pepco Holdings LLC [Member] | Other commitments [Member]
Business Acquisition [Line Items]
Other Additional Capital						46	46		46
Atlantic City Electric Company [Member]
Business Acquisition [Line Items]
Business Combination, Integration Related Costs	[2]				1	2		2	15
Other Commitment					9			9
Goodwill					1,200			1,200
Atlantic City Electric Company [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Other Commitment					$ 111			$ 111
Atlantic City Electric Company [Member] | Pepco Holdings LLC [Member] | Other commitments [Member]
Business Acquisition [Line Items]
Other Additional Capital						$ 49	$ 49		$ 49
Preferred Stock [Member] | Pepco Holdings LLC [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross				$ 180
[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]	(g)For the six months ended June 30, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. For the three months ended June 30, 2016 and the Successor period March 24, 2016 to June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $12 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[4]	(e)For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $9 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[5]	(f)For the six months ended June 30, 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. For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $3 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 Purchase Price Allocation Table - FitzPatrick (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Business Acquisition [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Amount		$ 0	$ 0	$ 226	$ 0
Fitzpatrick [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred				293
Current assets		58		58
Property, plant and equipment		278		278
Nuclear decommissioning trust funds		807		807
Other assets	[1]	114		114
Total assets		1,257		1,257
Current liabilities		7		7
Asset Retirement Obligations		417		417
Pension and OPEB obligations		49		49
Deferred income taxes		144		144
Spent nuclear fuel obligation		110		110
Other liabilities		11		11
Total liabilities		738		738
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		519		519
Business Combination, Bargain Purchase, Gain Recognized, Amount				226
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets		$ 110		110
Fitzpatrick [Member] | Cash and Cash Equivalents [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred				110
Business Combination, Consideration Transferred, Other				129
Fitzpatrick [Member] | Nuclear Fuel [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Other				$ 54
[1]	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 Di50

Mergers, Acquisitions, and Dispositions Merger Commitments Table (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Other Commitments [Line Items]
Other Commitment	$ 3,086
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	20
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	11
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	9
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	513	$ 513
Pepco Holdings LLC [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	315
Pepco Holdings LLC [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	120
Pepco Holdings LLC [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	84
Pepco Holdings LLC [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	111
Pepco Holdings LLC [Member] | Rate Bill Credits [Member]
Other Commitments [Line Items]
Other Commitment	259
Pepco Holdings LLC [Member] | Rate Bill Credits [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	259
Pepco Holdings LLC [Member] | Rate Bill Credits [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	91
Pepco Holdings LLC [Member] | Rate Bill Credits [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	67
Pepco Holdings LLC [Member] | Rate Bill Credits [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	101
Pepco Holdings LLC [Member] | Energy Efficiency Program [Member]
Other Commitments [Line Items]
Other Commitment	122
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
Pepco Holdings LLC [Member] | Charitable Contributions [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	50
Pepco Holdings LLC [Member] | Charitable Contributions [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	28
Pepco Holdings LLC [Member] | Charitable Contributions [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	12
Pepco Holdings LLC [Member] | Charitable Contributions [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	10
Pepco Holdings LLC [Member] | Delivery System Modernization [Member]
Other Commitments [Line Items]
Other Commitment	22
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
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
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	29
Pepco Holdings LLC [Member] | Other1 [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	6
Pepco Holdings LLC [Member] | Other1 [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	1
Pepco Holdings LLC [Member] | Other1 [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	5
Pepco Holdings LLC [Member] | Other1 [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	$ 0

Mergers, Acquisitions, and Di51

Mergers, Acquisitions, and Dispositions Merger Transaction Table (Details) - USD ($) $ in Millions		Mar. 23, 2016	Jun. 30, 2017	Jun. 30, 2016
Payments to Acquire Businesses, Gross			$ 212	$ 6,642
Pepco Holdings LLC [Member]
Payments to Acquire Businesses, Gross		$ 7,142
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	[1]	$ 29
[1]	(a)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.

Mergers, Acquisitions, and Di52

Mergers, Acquisitions, and Dispositions Purchase Price Allocation Table - PHI (Details) - Pepco Holdings LLC [Member] $ in Millions	Mar. 23, 2016USD ($)
Business Acquisition [Line Items]
Current assets	$ 1,441	[1]
Property, plant and equipment	11,088	[1]
Regulatory assets	5,015	[1]
Other assets	248	[1]
Goodwill	4,005
Total assets	21,797	[1]
Current liabilities	2,752	[1]
Unamortized energy contracts	1,515	[1]
Regulatory liabilities	297	[1]
Long-term debt, including current maturities	5,636	[1]
Deferred income taxes	3,447	[1]
Pension and OPEB obligations	821	[1]
Other liabilities	187	[1]
Total liabilities	14,655	[1]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 7,142	[1]
[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.

Mergers, Acquisitions, and Di53

Mergers, Acquisitions, and Dispositions PHI Impact on Exelon Consolidated (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 7,623	$ 6,910	$ 16,381	$ 14,485
Net income	64	306	1,046	430
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues	1,113	1,112	2,332	1,219
Net income	$ 61	$ 52	$ 202	$ (262)

Mergers, Acquisitions, and Di54

Mergers, Acquisitions, and Dispositions Merger Integration Related Costs Table (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017	Jun. 30, 2016
Business Combination, Integration Related Costs	[1],[2]	$ 8	$ 1			$ 17	$ 103
Exelon Generation Co L L C [Member]
Business Combination, Integration Related Costs	[2]	4	4			13	20
Commonwealth Edison Co [Member]
Business Combination, Integration Related Costs	[2],[3]	0	1			1	(7)
PECO Energy Co [Member]
Business Combination, Integration Related Costs	[2]	1	1			2	2
Baltimore Gas and Electric Company [Member]
Business Combination, Integration Related Costs	[2],[4]	1	(5)			2	(4)
Potomac Electric Power Company [Member]
Business Combination, Integration Related Costs	[2],[5]	1	(4)			2	23
Delmarva Power and Light Company [Member]
Business Combination, Integration Related Costs	[2],[6]	0	0			(7)	16
Atlantic City Electric Company [Member]
Business Combination, Integration Related Costs	[2]	1	2			2	15
Successor [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs	[2],[7]	$ 2	$ (1)	$ 55
Predecessor [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs	[2],[7]				$ 29	(2)
Regulatory Assets [Member] | Commonwealth Edison Co [Member]
Business Combination, Integration Related Costs							8
Regulatory Assets [Member] | Baltimore Gas and Electric Company [Member]
Business Combination, Integration Related Costs							6
Regulatory Assets [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs						8	12
Regulatory Assets [Member] | Potomac Electric Power Company [Member]
Business Combination, Integration Related Costs							9
Regulatory Assets [Member] | Delmarva Power and Light Company [Member]
Business Combination, Integration Related Costs						$ 8	$ 3
[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 six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $8 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]	(d)For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $6 million incurred at BGE that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[5]	(e)For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $9 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[6]	(f)For the six months ended June 30, 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. For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $3 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.
[7]	(g)For the six months ended June 30, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. For the three months ended June 30, 2016 and the Successor period March 24, 2016 to June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $12 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.

Mergers, Acquisitions, and Di55

Mergers, Acquisitions, and Dispositions ProForma Impact of Merger (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended				12 Months Ended
	Jun. 30, 2016		Jun. 30, 2017	[3],[4]	Jun. 30, 2016		Dec. 31, 2016
Business Acquisition, Pro Forma Revenue	$ 6,910	[1]			$ 15,466	[1]	$ 32,342	[2]
Business Acquisition, Pro Forma Net Income (Loss)	$ 268	[1]			$ 845	[1]	$ 1,562	[2]
Business Acquisition, Pro Forma Earnings Per Share, Basic	$ 0.29	[1]			$ 0.92	[1]	$ 1.69	[2]
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$ 0.29	[1]			$ 0.91	[1]	$ 1.69	[2]
Noncash Merger Related Costs			$ 0		$ 503
Pepco Holdings LLC [Member]
Noncash Merger Related Costs	$ 1				641		$ 680
Pepco Holdings LLC [Member] | Consolidation, Eliminations [Member]
Business Acquisition, Pro Forma Revenue					$ 170		$ 171
[1]	The amounts above include adjustments for non-recurring costs directly related to the merger of $1 million and $641 million for the three and six months ended June 30, 2016, respectively, and intercompany revenue of $170 million for the six months ended June 30, 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]	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.
[4]	See Note 4 — Mergers, Acquisitions and Dispositions for additional information related to the merger with PHI.

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details) GWh in Millions		Dec. 31, 2030	Jun. 30, 2017USD ($)		Jun. 09, 2017USD ($)	Jun. 30, 2017USD ($)		Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)		Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)		Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jun. 30, 2017USD ($)GWh		Jun. 30, 2016USD ($)	Dec. 31, 2017	Dec. 31, 2016USD ($)		Jun. 01, 2019	Jun. 01, 2018	Aug. 01, 2017USD ($)	Jul. 21, 2017USD ($)	Jun. 01, 2017	Sep. 30, 2016USD ($)	Aug. 31, 2010USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Revenues									$ 7,623,000,000					$ 6,910,000,000			$ 16,381,000,000		$ 14,485,000,000
Regulatory Assets			$ 11,238,000,000			$ 11,238,000,000			11,238,000,000			$ 11,388,000,000					11,238,000,000				$ 11,388,000,000
Business Combination, Integration Related Costs	[1],[2]								8,000,000					1,000,000			17,000,000		103,000,000
Capital Expenditures Incurred but Not yet Paid																	105,000,000		364,000,000
Regulatory Liabilities			4,972,000,000			4,972,000,000			4,972,000,000			4,789,000,000					4,972,000,000				4,789,000,000
Regulatory assets			9,945,000,000			9,945,000,000			9,945,000,000			10,046,000,000					9,945,000,000				10,046,000,000
Regulatory Liability, Current			574,000,000			574,000,000			574,000,000			602,000,000					574,000,000				602,000,000
Regulatory Liability, Noncurrent			4,398,000,000			4,398,000,000			4,398,000,000			4,187,000,000					4,398,000,000				4,187,000,000
Liabilities, Current			13,965,000,000			13,965,000,000			13,965,000,000			13,457,000,000					13,965,000,000				13,457,000,000
Other Commitment			3,086,000,000			3,086,000,000			3,086,000,000								3,086,000,000
Fair Value, Net Asset (Liability)			2,400,000,000			2,400,000,000			2,400,000,000								2,400,000,000
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
DecouplingImpactOnOperatingRevenuesAndRegulatoryAssets																	$ 36,000,000
CumulativeAnnualEnergyEfficiencyGoal | GWh																	88
Renewable Energy Resources Cumulatively Increase																	1.50%
LowIncomeEnergyAssistanceContributionAnnual																	$ 10,000,000
RenewableEnergyRetailLoad																											50.00%
Revenues									1,357,000,000					1,286,000,000			2,656,000,000		2,535,000,000
Regulatory Assets			1,232,000,000			1,232,000,000			1,232,000,000			1,167,000,000					1,232,000,000				1,167,000,000
Business Combination, Integration Related Costs	[2],[3]								0					1,000,000			1,000,000		(7,000,000)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																$ 11,000,000
Public Utilities, Requested Equity Capital Structure, Percentage																	6.47%
Capital Expenditures Incurred but Not yet Paid																	$ 82,000,000		21,000,000
Regulatory Liabilities			3,854,000,000			3,854,000,000			3,854,000,000			3,698,000,000					3,854,000,000				3,698,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount			12,000,000		$ 7,000,000												$ 44,000,000	[4]
Requested Debt and Equity Return on Distribution																	6.47%
Approved ROE	[4],[5]																11.50%
Regulatory assets			1,050,000,000			1,050,000,000			1,050,000,000			977,000,000					$ 1,050,000,000				977,000,000
Public Utilities, Requested Return on Equity, Percentage																	8.40%
Regulatory Liability, Current			269,000,000			269,000,000			269,000,000			329,000,000					$ 269,000,000				329,000,000
Regulatory Liability, Noncurrent			3,585,000,000			3,585,000,000			3,585,000,000			3,369,000,000					3,585,000,000				3,369,000,000
Liabilities, Current			3,750,000,000			3,750,000,000			3,750,000,000			2,938,000,000					3,750,000,000				2,938,000,000
Other Commitment			226,000,000			226,000,000			226,000,000								$ 226,000,000
LowIncomeEnergyAssistanceContributionLength																	5
Low Income Sector Consumption Reduction Targets Act 129 Phase II																	0.10%
SocialCarbonCost																	$ 16.50
NuclearFacilityPurchaseAmount																	$ 0.16
Requested ROE																	8.40%
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount												(18,000,000)					$ 96,000,000				$ 127,000,000
Public Utilities, Requested Equity Capital Structure, Percentage																	6.47%				6.45%
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
Public Utilities, Requested Rate Increase (Decrease), Percentage																	8.40%				8.34%
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]
CommercialAndIndustrialCustomerRateIncrease																	1.30%
FutureEnergyEfficiencySpending																	$ 400,000,000
Renewable Energy Resources Cumulatively Increase																	25.00%
ResidentialCustomerRateIncrease																	25.00%
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Total Projected Natural Gas LTIIP Spend									762,000,000							$ 275,000,000
Revenues									630,000,000					664,000,000			$ 1,426,000,000		1,505,000,000
Regulatory Assets			1,778,000,000			1,778,000,000			1,778,000,000			1,710,000,000					1,778,000,000				$ 1,710,000,000
Business Combination, Integration Related Costs	[2]								1,000,000					1,000,000			2,000,000		2,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount									$ 22,000,000
Public Utilities, Requested Equity Capital Structure, Percentage									11.00%
Capital Expenditures Incurred but Not yet Paid																	44,000,000		12,000,000
Regulatory Liabilities			699,000,000			699,000,000			$ 699,000,000			644,000,000					699,000,000				644,000,000
Requested Debt and Equity Return on Distribution									11.00%
Regulatory assets			1,732,000,000			1,732,000,000			$ 1,732,000,000			1,681,000,000					1,732,000,000				1,681,000,000
Regulatory Liability, Current			155,000,000			155,000,000			155,000,000			127,000,000					155,000,000				127,000,000
Regulatory Liability, Noncurrent			544,000,000			544,000,000			544,000,000			517,000,000					544,000,000				517,000,000
Liabilities, Current			1,213,000,000			1,213,000,000			1,213,000,000			727,000,000					1,213,000,000				727,000,000
Other Commitment			219,000,000			219,000,000			219,000,000								219,000,000
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Proposed Capital Expenditure	[4],[6]																8,000,000
Revenues									674,000,000					680,000,000			1,625,000,000		1,609,000,000
Regulatory Assets			692,000,000			692,000,000			692,000,000			712,000,000					692,000,000				712,000,000
Business Combination, Integration Related Costs	[2],[7]								1,000,000					(5,000,000)			2,000,000		(4,000,000)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																26,000,000
Capital Expenditures Incurred but Not yet Paid																	(6,000,000)		(2,000,000)
Regulatory Liabilities			157,000,000			157,000,000			157,000,000			160,000,000					157,000,000				160,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]																$ 31,000,000
Approved ROE	[4],[5]																10.50%
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			495,000,000			495,000,000			495,000,000			504,000,000					$ 495,000,000				504,000,000
Regulatory Liability, Current			67,000,000			67,000,000			67,000,000			50,000,000					67,000,000				50,000,000
Regulatory Liability, Noncurrent			90,000,000			90,000,000			90,000,000			110,000,000					90,000,000				110,000,000
Liabilities, Current			640,000,000			640,000,000			640,000,000			707,000,000					640,000,000				707,000,000
Other Commitment			263,000,000			263,000,000			263,000,000								263,000,000
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues						12,000,000			4,174,000,000					3,589,000,000			9,061,000,000		8,329,000,000
Business Combination, Integration Related Costs	[2]								4,000,000					4,000,000			13,000,000		20,000,000
Unregulated Operating Revenue																	101,000,000
Customer Refund Liability, Noncurrent			20,000,000			20,000,000			20,000,000								20,000,000
Capital Expenditures Incurred but Not yet Paid																	(48,000,000)		317,000,000
Customer Refund			20,000,000			20,000,000			20,000,000								20,000,000
License Costs																	29,000,000
Liabilities, Current			6,064,000,000			6,064,000,000			6,064,000,000			5,683,000,000					6,064,000,000				5,683,000,000
Other Commitment			2,257,000,000			2,257,000,000			2,257,000,000								2,257,000,000
Exelon Generation Co L L C [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation			3,000,000			3,000,000			3,000,000								3,000,000
Exelon Generation Co L L C [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation			7,000,000			7,000,000			7,000,000								7,000,000
PEPCO Holdings Inc [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment			41,000,000			41,000,000			41,000,000								41,000,000
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
CapitalProjectFundedByAgency									62,500,000
Revenues									514,000,000					509,000,000			1,045,000,000		1,061,000,000
Regulatory Assets			847,000,000			847,000,000			847,000,000			852,000,000					847,000,000				852,000,000
Business Combination, Integration Related Costs	[2],[8]								1,000,000					$ (4,000,000)			2,000,000		23,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																20,000,000
Capital Expenditures Incurred but Not yet Paid																	0		(11,000,000)
Regulatory Liabilities			22,000,000			22,000,000			22,000,000			31,000,000					22,000,000				31,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]																$ 5,000,000
Approved ROE	[4],[5]																10.50%
Regulatory assets			682,000,000			682,000,000			682,000,000			690,000,000					$ 682,000,000				690,000,000
Regulatory Liability, Current			5,000,000			5,000,000			5,000,000			11,000,000					5,000,000				11,000,000
Regulatory Liability, Noncurrent			17,000,000			17,000,000			17,000,000			20,000,000					17,000,000				20,000,000
Liabilities, Current			485,000,000			485,000,000			485,000,000			596,000,000					485,000,000				596,000,000
Other Commitment			20,000,000			20,000,000			20,000,000								20,000,000
Projected Capital Expenditures									500,000,000
Alternative Net Capital Requirement			250,000,000			250,000,000			250,000,000								250,000,000
Capital ProjectFundedByBonds									187,500,000
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount									$ 36,900,000		$ 77,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount											69,000,000								86,000,000
TaxAdjustmentIncludedInPublicUtilitiesRequestedRateIncreaseDecreaseAmount											$ 18,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage									9.50%		10.10%			10.60%
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues									$ 282,000,000					$ 281,000,000			644,000,000		643,000,000
Regulatory Assets			370,000,000			370,000,000			370,000,000			348,000,000					370,000,000				348,000,000
Business Combination, Integration Related Costs	[2],[9]								0					0			(7,000,000)		16,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																14,000,000
Capital Expenditures Incurred but Not yet Paid																	(15,000,000)		9,000,000
Regulatory Liabilities			138,000,000			138,000,000			138,000,000			140,000,000					138,000,000				140,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]																$ 6,000,000
Public Utilities, Interim Rate Increase (Decrease), Amount														$ 2,500,000
Approved ROE	[4],[5]																10.50%
Regulatory assets			299,000,000			299,000,000			299,000,000			289,000,000					$ 299,000,000				289,000,000
Public Utilities, Requested Return on Equity, Percentage														10.60%
Regulatory Liability, Current			43,000,000			43,000,000			43,000,000			43,000,000					43,000,000				43,000,000
Regulatory Liability, Noncurrent			95,000,000			95,000,000			95,000,000			97,000,000					95,000,000				97,000,000
Liabilities, Current			417,000,000			417,000,000			417,000,000			381,000,000					417,000,000				381,000,000
Other Commitment			11,000,000			11,000,000			11,000,000								11,000,000
Requested ROE														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									$ 4,900,000			10,400,000
Public Utilities, Requested Rate Increase (Decrease), Amount														$ 22,000,000
Public Utilities, Requested Return on Equity, Percentage									9.70%
Gas Revenues Increase Settlement																												$ 0.14
Requested ROE									9.70%
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			29,600,000			$ 32,100,000
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
Public Utilities, Requested Return on Equity, Percentage									9.70%
Projected Capital Expenditures											4,600,000
Requested ROE									9.70%
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Proposed Capital Expenditure									$ 32,000,000		29,000,000
Revenues									270,000,000					270,000,000			544,000,000		561,000,000
Regulatory Assets			495,000,000			495,000,000			495,000,000			501,000,000					495,000,000				501,000,000
Business Combination, Integration Related Costs	[2]								1,000,000					2,000,000			2,000,000		15,000,000
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[4]																42,000,000
Capital Expenditures Incurred but Not yet Paid																	14,000,000		(6,000,000)
Regulatory Liabilities			20,000,000			20,000,000			20,000,000			25,000,000					20,000,000				25,000,000
Public Utilities, Requested Rate Increase (Decrease), Amount	[4]																$ 20,000,000
Approved ROE	[4],[5]																10.50%
Regulatory assets			406,000,000			406,000,000			406,000,000			405,000,000					$ 406,000,000				405,000,000
Regulatory Liability, Current			20,000,000			20,000,000			20,000,000			25,000,000					20,000,000				25,000,000
Regulatory Liability, Noncurrent			0			0			0			0					0				0
Liabilities, Current			356,000,000			356,000,000			356,000,000			320,000,000					356,000,000				320,000,000
Other Commitment			9,000,000			9,000,000			9,000,000								9,000,000
Projected Capital Expenditures									79,000,000
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount									72,600,000		$ 70,000,000
Public Utilities, Requested Rate Increase (Decrease), Percentage											10.10%
Renewable Portfolio Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			19,000,000			19,000,000			19,000,000								19,000,000
Renewable Portfolio Standard [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			19,000,000			19,000,000			19,000,000								19,000,000
Recoverable Smart Meter Related Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			32,000,000			32,000,000			32,000,000								32,000,000
MergerIntegrationCostsToBeRecoveredInDelawareServiceTerritory [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			3,000,000			3,000,000			3,000,000								3,000,000
MergerIntegrationCostsToBeRecoveredInDelawareServiceTerritory [Member] | Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			6,000,000			6,000,000			6,000,000								6,000,000
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			4,000,000			4,000,000			4,000,000			4,000,000	[10]				4,000,000				4,000,000	[10]
Advanced Metering Infrastructure Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			29,000,000			29,000,000			29,000,000			23,000,000					29,000,000				23,000,000
Advanced Metering Infrastructure Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			137,000,000			137,000,000			137,000,000								137,000,000
Under Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			69,000,000			69,000,000			69,000,000			89,000,000					69,000,000				89,000,000
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[11]		8,000,000			8,000,000			8,000,000			23,000,000					8,000,000				23,000,000
Under Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			1,000,000			1,000,000			1,000,000			0					1,000,000				0
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[12]		21,000,000			21,000,000			21,000,000			38,000,000					21,000,000				38,000,000
Under Recovered Energy And Transmission Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[13]		6,000,000			6,000,000			6,000,000			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	[14]		6,000,000			6,000,000			6,000,000			5,000,000					6,000,000				5,000,000
Under Recovered Energy And Transmission Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[15]		27,000,000	[14]		27,000,000	[14]		27,000,000	[14]		17,000,000					27,000,000	[14]			17,000,000
Merger Integration Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			32,000,000			32,000,000			32,000,000			25,000,000					32,000,000				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			0					0				0
Merger Integration Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[16]		7,000,000			7,000,000			7,000,000			10,000,000					7,000,000				10,000,000
Merger Integration Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			12,000,000			12,000,000			12,000,000			11,000,000	[10]	9,000,000			12,000,000		9,000,000		11,000,000	[10]
Merger Integration Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			13,000,000			13,000,000			13,000,000					3,000,000			13,000,000		3,000,000
Merger Integration Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			10,000,000			10,000,000			10,000,000			28,000,000					10,000,000				28,000,000
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			4,000,000			4,000,000			4,000,000								4,000,000
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			6,000,000			6,000,000			6,000,000			4,000,000					6,000,000				4,000,000
MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			16,000,000			16,000,000			16,000,000			11,000,000					16,000,000				11,000,000
Under Recovered Distribution Service Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			239,000,000			239,000,000			239,000,000			188,000,000					239,000,000				188,000,000
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[17]		239,000,000			239,000,000			239,000,000			188,000,000					239,000,000				188,000,000
Under Recovered Distribution Service Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Under Recovered Distribution Service Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Under Recovered Distribution Service Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Under Recovered Distribution Service Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Under Recovered Distribution Service Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			679,000,000			679,000,000			679,000,000			701,000,000					679,000,000				701,000,000
AMI Expenses [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			163,000,000			163,000,000			163,000,000			164,000,000					163,000,000				164,000,000
AMI Expenses [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			43,000,000			43,000,000			43,000,000			49,000,000					43,000,000				49,000,000
AMI Expenses [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			225,000,000			225,000,000			225,000,000			230,000,000					225,000,000				230,000,000
Regulatory assets			225,000,000			225,000,000			225,000,000			230,000,000					225,000,000				230,000,000
Amount of Impairment to Carrying Amount of Regulatory Assets			52,000,000			52,000,000			52,000,000								52,000,000
AMI Expenses [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			167,000,000			167,000,000			167,000,000			174,000,000					167,000,000				174,000,000
AMI Expenses [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			81,000,000			81,000,000			81,000,000			84,000,000					81,000,000				84,000,000
AMI Expenses [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Energy Efficiency And Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			590,000,000			590,000,000			590,000,000			621,000,000					590,000,000				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			0					0				0
Energy Efficiency And Demand Response Programs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			1,000,000			1,000,000			1,000,000			1,000,000					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			271,000,000			271,000,000			271,000,000			285,000,000					271,000,000				285,000,000
Energy Efficiency And Demand Response Programs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			236,000,000			236,000,000			236,000,000			250,000,000					236,000,000				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			82,000,000			82,000,000			82,000,000			85,000,000					82,000,000				85,000,000
Energy Efficiency And Demand Response Programs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			0			0			0			0					0				0
Legacy AMI [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			56,000,000			56,000,000			56,000,000					$ 56,000,000			56,000,000		$ 56,000,000
Energy Efficiency Program [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			21,000,000			21,000,000			21,000,000								21,000,000
Energy Efficiency Program [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			2,000,000			2,000,000			2,000,000								2,000,000
Zero Emission Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities			22,000,000			22,000,000			22,000,000								22,000,000
Zero Emission Standard [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities			22,000,000			22,000,000			22,000,000								22,000,000
Zero Emission Standard [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues									73,000,000
Renewable Portfolio Standard [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liability, Current			10,000,000			10,000,000			10,000,000								10,000,000
Regulatory Liability, Noncurrent			20,000,000			20,000,000			20,000,000								20,000,000
Subsequent Event [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
EnergyEfficiencyAnnualCumulativeSavings		21.50%																		6.60%
RenewableEnergyRetailLoad																							100.00%	75.00%
Purchase Obligation																										$ 170,000,000
Subsequent Event [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation																										$ 235,000,000
Subsequent Event [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Customer Refund Liability, Noncurrent																									$ 5,000,000
Customer Refund																									$ 5,000,000
Public Utilities, Requested Return on Equity, Percentage								10.10%
Requested ROE								10.10%
Subsequent Event [Member] | Delmarva Power and Light Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount								$ 27,000,000
Pepco Holdings [Member] | Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment			25,600,000			25,600,000			25,600,000								25,600,000
Pepco Holdings [Member] | Merger Integration Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets			$ 9,000,000			$ 9,000,000			$ 9,000,000			11,000,000					$ 9,000,000				11,000,000
Business Combination, Integration Related Costs																					8,000,000
Pepco Holdings [Member] | Merger Integration Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[15]											$ 6,000,000									$ 6,000,000
[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 six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $8 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]	All rates are effective June 2017, subject to review by the FERC and other parties, which is due by fourth quarter 2017.
[5]	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, Pepco, DPL and ACE, the rate of return on common equity is 10.50%, inclusive of a 50 basis point incentive adder for being a member of a regional transmission organization.
[6]	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.
[7]	(d)For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $6 million incurred at BGE that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[8]	(e)For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $9 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[9]	(f)For the six months ended June 30, 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. For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $3 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.
[10]	As of June 30, 2017 and December 31, 2016, Pepco’s regulatory asset of $12 million and $11 million, respectively, represents previously incurred PHI acquisition costs authorized for recovery by the November 2016 Maryland distribution rate case order. As of June 30, 2017, DPL’s regulatory asset of $13 million represents previously incurred PHI acquisition costs, including $4 million authorized for recovery by the February 2017 Maryland distribution rate case order, $6 million authorized for recovery by the May 2017 Delaware electric distribution rate case order, and $3 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.
[11]	As of June 30, 2017, ComEd’s regulatory asset of $8 million reflects Constellation merger and integration costs to be recovered upon FERC approval. As of June 30, 2017, ComEd’s regulatory liability of $40 million included $8 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.
[12]	As of June 30, 2017, BGE's regulatory asset of $21 million included $10 million related to under-recovered electric energy costs, $5 million related to under-recovered natural gas costs, $4 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $2 million of abandonment costs to be recovered upon FERC approval. 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.
[13]	As of June 30, 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 June 30, 2017, Pepco's regulatory liability of $2 million related to 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.
[14]	As of June 30, 2017, DPL's regulatory asset of $6 million related to under-recovered electric energy costs. As of June 30, 2017, DPL's regulatory liability of $12 million included $10 million of over-recovered electric energy 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.
[15]	As of June 30, 2017, ACE's regulatory asset of $27 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $16 million of under-recovered electric energy costs. As of June 30, 2017, ACE's regulatory liability of $8 million related to 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.
[16]	As of June 30, 2017 and December 31, 2016, BGE's regulatory asset of $7 million and $10 million, respectively, included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order.
[17]	As of June 30, 2017, ComEd’s regulatory asset of $239 million was comprised of $184 million for the 2015 - 2017 annual reconciliations and $55 million related to significant one-time events including $14 million of deferred storm costs, $9 million of Constellation and PHI merger and integration related costs, $3 million of emerald ash borer costs, and $29 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. See Note 4— Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information.

Regulatory Matters Regulatory M

Regulatory Matters Regulatory Matters - Annual Electric Transmission Fillings (Details) - USD ($) $ in Millions		Jun. 30, 2017	Jun. 09, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2017
Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount		$ 12	$ 7			$ 44	[1]
Prior Year Revenue Adjustment	[1]					(33)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]					$ 11
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[2]					8.43%
Public Utilities, Approved Return on Equity, Percentage	[1],[3]					11.50%
Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[1]					$ 31
Prior Year Revenue Adjustment	[1]					3
Proposed Capital Expenditure	[1],[4]					8
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]					$ 26
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[2]					7.47%
Public Utilities, Approved Return on Equity, Percentage	[1],[3]					10.50%
Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[1]					$ 5
Prior Year Revenue Adjustment	[1]					15
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]					$ 20
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[2]					7.92%
Public Utilities, Approved Return on Equity, Percentage	[1],[3]					10.50%
Delmarva Power and Light Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[1]					$ 6
Prior Year Revenue Adjustment	[1]					8
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]					$ 14
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[2]					7.16%
Public Utilities, Approved Return on Equity, Percentage	[1],[3]					10.50%
Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	[1]					$ 20
Prior Year Revenue Adjustment	[1]					22
Proposed Capital Expenditure				$ 32	$ 29
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]					$ 42
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[2]					8.02%
Public Utilities, Approved Return on Equity, Percentage	[1],[3]					10.50%
[1]	All rates are effective June 2017, subject to review by the FERC and other parties, which is due by fourth quarter 2017.
[2]	Represents the weighted average debt and equity return on transmission rate bases.
[3]	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, Pepco, DPL and ACE, the rate of return on common equity is 10.50%, inclusive of a 50 basis point incentive adder for being a member of a regional transmission organization.
[4]	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.

Regulatory Matters Regulatory58

Regulatory Matters Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions		3 Months Ended					6 Months Ended			12 Months Ended
		Jun. 30, 2017		Jun. 30, 2016	Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017		Jun. 30, 2016	Dec. 31, 2016
Regulatory Assets [Line Items]
Current		$ 1,293					$ 1,293			$ 1,342
Noncurrent		9,945					9,945			10,046
Regulatory Assets		11,238					11,238			11,388
Business Combination, Integration Related Costs	[1],[2]	8		$ 1			17		$ 103
Renewable Portfolio Standard [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19					19
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[3]	4,086					4,086			4,162
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	2,091					2,091			2,016
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		679					679			701
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		239					239			188
Energy Efficiency Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19					19
Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		117					117			124
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		782					782			812
Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets		918					918			1,085
Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3					3			5
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		119					119			111
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		289					289			305
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		55					55			56
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		258					258			260
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		69					69			89
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34					34			36
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5					5			10
Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										7
Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		590					590			621
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		32					32			25
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		74					74			27
Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			8
Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34					34			34
Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		47					47			31
Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		108					108			138
CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10					10			11
AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		500					500			477
Under funded Benefit Post Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[3]	1,025					1,025
Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		55					55			49
Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Current		182					182			190
Noncurrent		1,050					1,050			977
Regulatory Assets		1,232					1,232			1,167
Business Combination, Integration Related Costs	[2],[5]	0		1			1		(7)
Commonwealth Edison Co [Member] | Renewable Portfolio Standard [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19					19
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	[4]	76					76			75
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		163					163			164
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[6]	239					239			188
Commonwealth Edison Co [Member] | Energy Efficiency Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19					19
Commonwealth Edison Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		39					39			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			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		84					84			76
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		266					266			278
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		55					55			56
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		256					256			258
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[7]	8					8			23
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
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
Commonwealth Edison Co [Member] | Merger Integration Costs [Member] | Pepco Holdings [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9					9			11
Business Combination, Integration Related Costs										8
Commonwealth Edison Co [Member] | 561710 Exterminating and Pest Control Services [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3					3
Commonwealth Edison Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets										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] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8					8			7
Business Combination, Integration Related Costs									8
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		22					22			22
Commonwealth Edison Co [Member] | Recoverable Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		55					55			54
Commonwealth Edison Co [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		29					29			23
Commonwealth Edison Co [Member] | Annual Reconciliations [Member]
Regulatory Assets [Line Items]
Regulatory Assets		184					184			134
Commonwealth Edison Co [Member] | ElectricTransmissionCostsUnderRecovery [Member]
Regulatory Assets [Line Items]
Regulatory Assets										15
Commonwealth Edison Co [Member] | Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		14					14			20
PECO Energy Co [Member]
Regulatory Assets [Line Items]
Current		46					46			29
Noncurrent		1,732					1,732			1,681
Regulatory Assets		1,778					1,778			1,710
Business Combination, Integration Related Costs	[2]	1		1			2		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		1,645					1,645			1,583
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		43					43			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]
Regulatory Assets		0					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		23					23			23
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		23					23			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		1					1			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					0
PECO Energy Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										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] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets										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		22					22			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		10					10			11
PECO Energy Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9					9			9
Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Current		197					197			208
Noncurrent		495					495			504
Regulatory Assets		692					692			712
Business Combination, Integration Related Costs	[2],[8]	1		(5)			2		(4)
Baltimore Gas and Electric Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		32					32
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	100					100			98
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Noncurrent		225					225			230
Regulatory Assets		225					225			230
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
Baltimore Gas and Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3					3			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					0			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	[9]	21					21			38
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			1
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5					5			10
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										7
Baltimore Gas and Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		271					271			285
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[10]	7					7			10
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member] | Pepco Holdings [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[11]									6
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[12]	35					35			3
Baltimore Gas and Electric Company [Member] | UnderRecoveredNaturalGasDecouplingRevenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11					11			2
Baltimore Gas and Electric Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets										3
Baltimore Gas and Electric Company [Member] | Under-Recovered Electric Revenue Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets		24					24			1
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] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			5
Business Combination, Integration Related Costs									6
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		41					41			38
Baltimore Gas and Electric Company [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		137					137
Baltimore Gas and Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4					4			4
Baltimore Gas and Electric Company [Member] | Abandonment costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2					2			3
Baltimore Gas and Electric Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10					10			28
Pepco Holdings LLC [Member] | Predecessor [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs	[2],[13]					$ 29	(2)
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Current		605					605			653
Noncurrent		2,715					2,715			2,851
Regulatory Assets		3,320					3,320			3,504
Business Combination, Integration Related Costs	[2],[13]	2		(1)	$ 55
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Pepco Holdings LLC [Member] | Deferred Income Tax Charge [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	270					270			260
Pepco Holdings LLC [Member] | AMI Expenses [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		248					248			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		77					77			81
Pepco Holdings LLC [Member] | Fair Value Of Long Term Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		645					645			671
Pepco Holdings LLC [Member] | Fair Value Of Supply Contract [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		918					918			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		2					2			2
Pepco Holdings LLC [Member] | Under Recovered Energy And Transmission Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		39					39			28
Pepco Holdings LLC [Member] | Deferred Storm Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34					34			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
Pepco Holdings LLC [Member] | Energy Efficiency And Demand Response Programs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		318					318			335
Pepco Holdings LLC [Member] | Merger Integration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		25					25			15
Pepco Holdings LLC [Member] | Under Recovered Decoupling Revenue [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		39					39			24
Pepco Holdings LLC [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6
Pepco Holdings LLC [Member] | Deferred Project Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets										8
Pepco Holdings LLC [Member] | Workers Compensation and Long-Term Disability [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34					34			34
Pepco Holdings LLC [Member] | Recoverable Vacation Pay [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		25					25			24
Pepco Holdings LLC [Member] | Stranded Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		108					108			138
Pepco Holdings LLC [Member] | AssetRemovalCosts [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		500					500			477
Pepco Holdings LLC [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Business Combination, Integration Related Costs							8		12
Pepco Holdings LLC [Member] | Regulatory Assets [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		32					32			29
Potomac Electric Power Company [Member]
Regulatory Assets [Line Items]
Current		165					165			162
Noncurrent		682					682			690
Regulatory Assets		847					847			852
Business Combination, Integration Related Costs	[2],[14]	1		(4)			2		23
Potomac Electric Power Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Potomac Electric Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	176					176			171
Potomac Electric Power Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		167					167			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		16					16			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
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	[15]	6					6			6
Potomac Electric Power Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10					10			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
Potomac Electric Power Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		236					236			250
Potomac Electric Power Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		12		9	9		12		9	11	[16]
Potomac Electric Power Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		31					31			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		34					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		138					138			134
Potomac Electric Power Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		21					21			22
Business Combination, Integration Related Costs									9
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		33					33			31
Potomac Electric Power Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2					2
Potomac Electric Power Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4					4
Delmarva Power and Light Company [Member]
Regulatory Assets [Line Items]
Current		71					71			59
Noncurrent		299					299			289
Regulatory Assets		370					370			348
Business Combination, Integration Related Costs	[2],[17]	0		0			(7)		16
Delmarva Power and Light Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Delmarva Power and Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	41					41			38
Delmarva Power and Light Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		81					81			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		8					8			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
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					1			0
Delmarva Power and Light Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[18]	6					6			5
Delmarva Power and Light Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			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
Delmarva Power and Light Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		82					82			85
Delmarva Power and Light Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		13		3	$ 3		13		3
Delmarva Power and Light Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8					8			3
Delmarva Power and Light Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			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					15			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		95					95			88
Delmarva Power and Light Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8					8			5
Business Combination, Integration Related Costs							8		3
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		22					22			20
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4					4			4	[16]
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInDelawareServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3					3
Delmarva Power and Light Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets										1
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6					6			4
Atlantic City Electric Company [Member]
Regulatory Assets [Line Items]
Current		89					89			96
Noncurrent		406					406			405
Regulatory Assets		495					495			501
Business Combination, Integration Related Costs	[2]	1		$ 2			2		$ 15
Atlantic City Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0			0
Atlantic City Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	53					53			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		1					1			2
Atlantic City Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[11]	27	[18]				27	[18]		17
Atlantic City Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		18					18			18
Atlantic City Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					0
Atlantic City Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets										0
Atlantic City Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0					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] | 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		108					108			138
Atlantic City Electric Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		268					268			255
Atlantic City Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4					4			4
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		20					20			19
Atlantic City Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11					11			6
Atlantic City Electric Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		$ 16					$ 16			$ 11
[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 June 30, 2017 and December 31, 2016, the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $1,025 million and $995 million, respectively, as a result 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]	As of June 30, 2017, includes transmission-related regulatory assets that require FERC approval separate from the transmission formula rate of $22 million, $41 million, $33 million, $22 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.
[5]	For the six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $8 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 June 30, 2017, ComEd’s regulatory asset of $239 million was comprised of $184 million for the 2015 - 2017 annual reconciliations and $55 million related to significant one-time events including $14 million of deferred storm costs, $9 million of Constellation and PHI merger and integration related costs, $3 million of emerald ash borer costs, and $29 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. See Note 4— Merger, Acquisitions, and Dispositions of the Exelon 2016 Form 10-K for further information.
[7]	As of June 30, 2017, ComEd’s regulatory asset of $8 million reflects Constellation merger and integration costs to be recovered upon FERC approval. As of June 30, 2017, ComEd’s regulatory liability of $40 million included $8 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.
[8]	(d)For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $6 million incurred at BGE that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[9]	As of June 30, 2017, BGE's regulatory asset of $21 million included $10 million related to under-recovered electric energy costs, $5 million related to under-recovered natural gas costs, $4 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $2 million of abandonment costs to be recovered upon FERC approval. 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.
[10]	As of June 30, 2017 and December 31, 2016, BGE's regulatory asset of $7 million and $10 million, respectively, included $6 million of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order.
[11]	As of June 30, 2017, ACE's regulatory asset of $27 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $16 million of under-recovered electric energy costs. As of June 30, 2017, ACE's regulatory liability of $8 million related to 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]	Represents the electric and natural gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of June 30, 2017, BGE had a regulatory asset of $24 million related to under-recovered electric revenue decoupling and $11 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.
[13]	(g)For the six months ended June 30, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. For the three months ended June 30, 2016 and the Successor period March 24, 2016 to June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $12 million incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[14]	(e)For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $9 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5—Regulatory Matters for more information.
[15]	As of June 30, 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 June 30, 2017, Pepco's regulatory liability of $2 million related to 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.
[16]	As of June 30, 2017 and December 31, 2016, Pepco’s regulatory asset of $12 million and $11 million, respectively, represents previously incurred PHI acquisition costs authorized for recovery by the November 2016 Maryland distribution rate case order. As of June 30, 2017, DPL’s regulatory asset of $13 million represents previously incurred PHI acquisition costs, including $4 million authorized for recovery by the February 2017 Maryland distribution rate case order, $6 million authorized for recovery by the May 2017 Delaware electric distribution rate case order, and $3 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.
[17]	(f)For the six months ended June 30, 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. For the three and six months ended June 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $3 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.
[18]	As of June 30, 2017, DPL's regulatory asset of $6 million related to under-recovered electric energy costs. As of June 30, 2017, DPL's regulatory liability of $12 million included $10 million of over-recovered electric energy 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 Regulatory59

Regulatory Matters Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions		Jun. 30, 2017		Dec. 31, 2016
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		$ 574		$ 602
Regulatory Liability, Noncurrent		4,398		4,187
Regulatory Liabilities		4,972		4,789
Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		43		47
Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,870		2,607
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,592		1,601
Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		38		39
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		128		185
Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8		8
Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		59		76
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		16		20
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		123		134
Rate Stabilization Deferral [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		22
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		70		72
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		269		329
Regulatory Liability, Noncurrent		3,585		3,369
Regulatory Liabilities		3,854		3,698
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		2,364		2,169
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,332		1,324
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		88		141
Commonwealth Edison Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				0
Commonwealth Edison Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Commonwealth Edison Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Commonwealth Edison Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	40		60
Commonwealth Edison Co [Member] | Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		22
Commonwealth Edison Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8		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		8		30
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		155		127
Regulatory Liability, Noncurrent		544		517
Regulatory Liabilities		699		644
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		506		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		39		41
PECO Energy Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		8		8
PECO Energy Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		59		76
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		16		20
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2]	61		56
PECO Energy Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		10		5
PECO Energy Co [Member] | Over Recovered NonBypassable Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		9
PECO Energy Co [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				4
PECO Energy Co [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		16		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		36		34
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		67		50
Regulatory Liability, Noncurrent		90		110
Regulatory Liabilities		157		160
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		129		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] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Baltimore Gas and Electric Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Baltimore Gas and Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0	[3]	0
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		25		19
Baltimore Gas and Electric Company [Member] | Over-Recovered Natural Gas Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		5
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		68		79
Regulatory Liability, Noncurrent		151		158
Regulatory Liabilities		219		237
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		131		136
Pepco Holdings LLC [Member] | Deferred Lease Revenue [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		38		39
Pepco Holdings LLC [Member] | Energy Efficiency Demand Response Programs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1		3
Pepco Holdings LLC [Member] | Dlc Program Cost [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
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] | 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		22		18
Pepco Holdings LLC [Member] | Regulatory Liabilities Other [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		27		41
Potomac Electric Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		5		11
Regulatory Liability, Noncurrent		17		20
Regulatory Liabilities		22		31
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		18		18
Potomac Electric Power Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1		3
Potomac Electric Power Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Potomac Electric Power Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Potomac Electric Power Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Potomac Electric Power Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[4]	2		8
Potomac Electric Power Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1		2
Potomac Electric Power Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				5
Potomac Electric Power Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2		3
Delmarva Power and Light Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		43		43
Regulatory Liability, Noncurrent		95		97
Regulatory Liabilities		138		140
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		113		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] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Delmarva Power and Light Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Delmarva Power and Light Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[5]	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 Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				3
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		10		2
Atlantic City Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		20		25
Regulatory Liability, Noncurrent		0		0
Regulatory Liabilities		20		25
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] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Atlantic City Electric Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Atlantic City Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[6]	8		5	[5]
Atlantic City Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		12		20
Atlantic City Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				4
Atlantic City Electric Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 8		$ 1
[1]	As of June 30, 2017, ComEd’s regulatory asset of $8 million reflects Constellation merger and integration costs to be recovered upon FERC approval. As of June 30, 2017, ComEd’s regulatory liability of $40 million included $8 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.
[2]	As of June 30, 2017, PECO's regulatory liability of $61 million included $36 million related to over-recovered costs under the DSP program, $16 million related to the over-recovered natural gas costs under the PGC and $9 million related to over-recovered non-bypassable transmission service charges. 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.
[3]	As of June 30, 2017, BGE's regulatory asset of $21 million included $10 million related to under-recovered electric energy costs, $5 million related to under-recovered natural gas costs, $4 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $2 million of abandonment costs to be recovered upon FERC approval. 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.
[4]	As of June 30, 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 June 30, 2017, Pepco's regulatory liability of $2 million related to 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.
[5]	As of June 30, 2017, DPL's regulatory asset of $6 million related to under-recovered electric energy costs. As of June 30, 2017, DPL's regulatory liability of $12 million included $10 million of over-recovered electric energy 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.
[6]	As of June 30, 2017, ACE's regulatory asset of $27 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $16 million of under-recovered electric energy costs. As of June 30, 2017, ACE's regulatory liability of $8 million related to 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.

Regulatory Matters Regulatory60

Regulatory Matters Regulatory Matters - Purchase of Receivables Programs (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2017	Dec. 31, 2016
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 304	$ 313
Allowance for Doubtful Accounts Receivable	[1]	(31)	(37)
Payments to Acquire Other Receivables, Net		273	276
Commonwealth Edison Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		85	87
Allowance for Doubtful Accounts Receivable	[1]	(12)	(14)
Payments to Acquire Other Receivables, Net		73	73
PECO Energy Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		73	72
Allowance for Doubtful Accounts Receivable		(5)	(6)
Payments to Acquire Other Receivables, Net		68	66
Baltimore Gas and Electric Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		53	59
Allowance for Doubtful Accounts Receivable	[1]	(3)	(4)
Payments to Acquire Other Receivables, Net		50	55	[2]
PEPCO Holdings Inc [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		93	95
Allowance for Doubtful Accounts Receivable	[1]	(11)	(13)
Payments to Acquire Other Receivables, Net		82	82
Potomac Electric Power Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables	[3]	61	63
Allowance for Doubtful Accounts Receivable	[1]	(6)	(7)
Payments to Acquire Other Receivables, Net		$ 55	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	[3]	$ 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		$ 22	22
Allowance for Doubtful Accounts Receivable		(3)	(4)
Payments to Acquire Other Receivables, Net		$ 19	$ 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]	As of June 30, 2017, PECO's regulatory liability of $61 million included $36 million related to over-recovered costs under the DSP program, $16 million related to the over-recovered natural gas costs under the PGC and $9 million related to over-recovered non-bypassable transmission service charges. 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.
[3]	Pepco's electric POR program in Maryland included a discount on purchased receivables ranging from 0% to 2% depending on customer class. Pepco's electric POR program in the District of Columbia included a discount on purchased receivables ranging from 0% to 6% through April 6, 2017 and 0% to 2% effective April 7, 2017, depending on customer class. DPL's electric POR program in Maryland included a discount on purchased receivables ranging from 0% to 1% through May 31, 2017 and 0% to 4% effective June 1, 2017, depending on customer class.

Regulatory Matters Regulatory61

Regulatory Matters Regulatory Matters - Capitalized Ratemaking Amount Not Recognized (Details) - USD ($) $ in Millions		Jun. 30, 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	[1]	6	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	[2]	55	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	[3]	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	[3]	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
[1]	Reflects ComEd's unrecognized equity returns earned for ratemaking purposes on its under-recovered distribution services costs regulatory assets.
[2]	BGE's authorized amounts capitalized for ratemaking purposes relate to earnings on shareholders' investment on its AMI Programs.
[3]	Pepco's and DPL's authorized amounts capitalized for ratemaking purposes relate to earnings on shareholders' investment on their respective AMI Programs and Energy Efficiency and Demand Response Programs. The earnings on energy efficiency are on Pepco DC and DPL DE programs only.

Impairment of Long-Lived Asse62

Impairment of Long-Lived Assets (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Property, plant and equipment, net				$ 72,748		$ 71,555
Proceeds from Long-term Capital Lease Obligations			$ 360
Estimated residual value of leased assets			356
Proceeds From Lease Termination				0	$ 360
Impairment of Long-Lived Assets to be Disposed of				418
Gain (Loss) on Contract Termination			4
Impairment of long-lived assets and losses on regulatory assets				445	239
Wind Assets [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Property, plant and equipment, net			$ 60
Property, Plant, and Equipment, Fair Value Disclosure					24
Impairment of long-lived assets and losses on regulatory assets					$ 36
Constellation Energy Group LLC [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Tangible Asset Impairment Charges	$ 15	$ 119
Electricity Generation Plant, Non-Nuclear [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Impairment of Long-Lived Assets to be Disposed of				$ 418

Early Nuclear Plant Retiremen63

Early Nuclear Plant Retirements Early Nuclear Plant Retirements - Narrative (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Facility Closing [Member]
Property, Plant and Equipment [Line Items]
Other Expenses		$ 714
Facility Closing [Member] | Three Mile Island [Member]
Property, Plant and Equipment [Line Items]
Restructuring Reserve, Accrual Adjustment	$ 71
Other Expenses	$ 37
Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	42.59%

Early Nuclear Plant Retiremen64

Early Nuclear Plant Retirements Early Nuclear Plant Retirement - Pretax Expense (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended		12 Months Ended
		Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Other Cost and Expense, Operating		$ 2,971			$ 2,505	$ 5,431	$ 5,341
Other, net		$ 205			144	488	$ 258
Facility Closing [Member]
Other Expenses								$ 714
Facility Closing [Member] | Three Mile Island [Member]
Restructuring and Related Cost, Accelerated Depreciation	[1]					35
Nuclear Fuel Amortization						2
Other Expenses						$ 37
Facility Closing [Member] | Clinton and Quad Cities [Member]
Restructuring and Related Cost, Accelerated Depreciation	[2]		$ 253	$ 344	115			712
Nuclear Fuel Amortization			23	28	9			60
Other Cost and Expense, Operating	[3]		(120)	5	141			26
Accretion Expense, Including Asset Retirement Obligations	[4]		0	2	0			2
Other, net	[4]		(31)	(41)	(14)			(86)
Other Expenses			$ 125	$ 338	$ 251			$ 714
[1]	Reflects incremental accelerated depreciation of plant assets, including any ARC.
[2]	Reflects incremental accelerated depreciation of plant assets, including any ARC, for the period June 2, 2016, through December 6, 2016.
[3]	Primarily includes materials and supplies inventory reserve adjustments, employee related costs and construction work-in-progress (CWIP) impairments.
[4]	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 Asset65

Fair Value of Financial Assets and Liabilities - Fair Value of Financial Liabilities Recorded at the Carrying Amount (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Due to Related Parties, Noncurrent		$ 641	$ 641
Spent Nuclear Fuel Obligation, Noncurrent		1,139	1,024
Deferred Finance Costs, Net		185	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		1,757	1,267
Long-term debt (including amounts due within one year)(a)	[1]	33,934	34,005
Due to Related Parties, Noncurrent	[2]	641	641
Spent Nuclear Fuel Obligation, Noncurrent		1,139	1,024
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		1,757	1,267
Long-term debt (including amounts due within one year)(a)	[1]	35,416	34,813
Due to Related Parties, Noncurrent	[2]	693	667
Spent Nuclear Fuel Obligation, Noncurrent		830	732
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	1,113
Due to Related Parties, Noncurrent	[2]	0	0
Spent Nuclear Fuel Obligation, Noncurrent		0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		1,757	1,267
Long-term debt (including amounts due within one year)(a)	[1]	33,460	31,741
Due to Related Parties, Noncurrent	[2]	0	0
Spent Nuclear Fuel Obligation, Noncurrent		830	732
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]	1,956	1,959
Due to Related Parties, Noncurrent	[2]	693	667
Spent Nuclear Fuel Obligation, Noncurrent		0	0
Exelon Generation Co L L C [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Spent Nuclear Fuel Obligation, Noncurrent		1,139	1,024
Deferred Finance Costs, Net		53	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		716	699
Long-term debt (including amounts due within one year)(a)	[1]	9,754	9,241
Spent Nuclear Fuel Obligation, Noncurrent		1,139	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		716	699
Long-term debt (including amounts due within one year)(a)	[1]	9,722	9,152
Spent Nuclear Fuel Obligation, Noncurrent		830	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		716	699
Long-term debt (including amounts due within one year)(a)	[1]	8,061	7,482
Spent Nuclear Fuel Obligation, Noncurrent		830	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]	1,661	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		44	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		389
Long-term debt (including amounts due within one year)(a)	[1]	7,036	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		389
Long-term debt (including amounts due within one year)(a)	[1]	7,728	7,585
Due to Related Parties, Noncurrent	[2]	223	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		389
Long-term debt (including amounts due within one year)(a)	[1]	7,728	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]	223	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]	2,834	2,794
Due to Related Parties, Noncurrent		199	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]	2,834	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		199	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		85	45
Long-term debt (including amounts due within one year)(a)	[1]	2,282	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		85	45
Long-term debt (including amounts due within one year)(a)	[1]	2,497	2,467
Due to Related Parties, Noncurrent	[2]	271	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		85	45
Long-term debt (including amounts due within one year)(a)	[1]	2,497	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]	271	260
Pepco Holdings LLC [Member] | Successor [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		6	2
Pepco Holdings LLC [Member] | Reported Value Measurement [Member] | Successor [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		67	522
Long-term debt (including amounts due within one year)(a)	[1]	5,952	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		67	522
Long-term debt (including amounts due within one year)(a)	[1]	6,002	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		67	522
Long-term debt (including amounts due within one year)(a)	[1]	5,707	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]	295	289
Potomac Electric Power Company [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		33	30
Potomac Electric Power Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value			23
Long-term debt (including amounts due within one year)(a)	[1]	2,545	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			23
Long-term debt (including amounts due within one year)(a)	[1]	3,074	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
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			23
Long-term debt (including amounts due within one year)(a)	[1]	3,065	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
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]
Short-term Debt, Fair Value		25
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]
Short-term Debt, Fair Value		25
Long-term debt (including amounts due within one year)(a)	[1]	1,398	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]
Short-term Debt, Fair Value		0
Long-term debt (including amounts due within one year)(a)	[1]	0	0
Delmarva Power and Light Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		25
Long-term debt (including amounts due within one year)(a)	[1]	1,398	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]
Short-term Debt, Fair Value		0
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]
Short-term Debt, Fair Value		42
Long-term debt (including amounts due within one year)(a)	[1]	1,138	1,155
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		42
Long-term debt (including amounts due within one year)(a)	[1]	1,266	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]
Short-term Debt, Fair Value		0
Long-term debt (including amounts due within one year)(a)	[1]	0	0
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		42
Long-term debt (including amounts due within one year)(a)	[1]	980	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]
Short-term Debt, Fair Value		0
Long-term debt (including amounts due within one year)(a)	[1]	$ 286	$ 280
[1]	Includes unamortized debt issuance costs which are not fair valued of $185 million, $53 million, $44 million, $15 million, $14 million, $6 million, $33 million, $11 million, and $5 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of June 30, 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 June 30, 2017 and December 31, 2016.

Fair Value of Financial Asset66

Fair Value of Financial Assets and Liabilities - Fair Value Measurements of Assets and Liabilities, Recurring and Nonrecurring (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Current		$ 244	$ 282
Derivative Liability, Noncurrent		417	392
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative, Collateral, Right to Reclaim Cash		48	29
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		(1)	(2)
Derivative Asset, Notional Amount		771	933
Margin Deposit Assets		84	(158)
Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		353	360
Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		203	180
Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		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		29	31
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	257	373
FinancialAssetsFairValueDisclosure1		14,573	13,253
Deferred Compensation Liability, Current and Noncurrent		(131)	(136)
Financial Liabilities Fair Value Disclosure		(792)	(810)
FinancialAssetLiabilitiesNetFairValueDisclosure1		13,781	12,443
Alternative Investment, Fair Value Disclosure		3,355	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		(650)	(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		(4,795)	(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] | 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],[3]	4,222	4,114
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] | 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			(10)
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		(20)	(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		(4)	(4)
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		13	23
Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	12,670	11,092
Alternative Investment, Fair Value Disclosure	[4]	3,322	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	[5]	184	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		6,801	6,014
Alternative Investment, Fair Value Disclosure		2,104	2,011
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		4,541	3,977
Alternative Investment, Fair Value Disclosure		502	493
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		1,911	1,804
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		1,799	1,320
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		51	37
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		232	264
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	[6]	548	552
Alternative Investment, Fair Value Disclosure	[6]	502	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		506	498
Alternative Investment, Fair Value Disclosure		78	71
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		197	148
Alternative Investment, Fair Value Disclosure		197	148
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		441	326
Alternative Investment, Fair Value Disclosure		441	326
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	[7]	75	113
Alternative Investment, Fair Value Disclosure	[7]	33	64
Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, 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			2
Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			17
Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		54	83
Alternative Investment, Fair Value Disclosure		33	64
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		233	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		78	74
Fair Value, Measurements, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		54	50
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		13	16
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		88	84
Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		4,934	5,092
Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		81	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],[3]	(3,737)	(3,787)
Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,278	1,381
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		19	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		11	16
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		17	28
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		(13)	(21)
Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		41	42
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		71	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]	257	373
FinancialAssetsFairValueDisclosure1		6,282	5,674
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(4)	(37)
FinancialAssetLiabilitiesNetFairValueDisclosure1		6,278	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		(3)	(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		(697)	(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		(4)	(3)
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],[3]	698	1,233
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] | 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
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		(4)	(4)
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		3	4
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	5,864	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	[5]	117	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		3,980	3,551
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		1,767	1,291
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] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,767	1,291
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] | 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] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	0	0
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] | 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] | 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] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[7]	21	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]
Investments, 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
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			16
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending 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] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		132	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		78	74
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		54	50
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] | 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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		632	1,358
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		3	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],[3]	(627)	(1,164)
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		8	197
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		0	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 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] | 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		(3)	(2)
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 2 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties		284	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
FinancialAssetsFairValueDisclosure1		3,302	2,937
Deferred Compensation Liability, Current and Noncurrent		(131)	(136)
Financial Liabilities Fair Value Disclosure		(253)	(237)
FinancialAssetLiabilitiesNetFairValueDisclosure1		3,049	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		(112)	(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		(2,691)	(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		(48)	(50)
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],[3]	2,627	2,339
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		(10)	(12)
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			(10)
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		(20)	(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] | 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		10	19
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	2,801	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	[5]	67	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		717	452
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		2,017	1,943
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		1,656	1,554
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		32	29
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		51	37
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		232	264
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	[6]	46	59
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] | 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] | 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] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[7]	0	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]
Investments, 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			2
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
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending 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 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		80	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] | 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] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		13	16
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		67	64
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		2,698	2,505
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		47	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],[3]	(2,343)	(2,142)
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		402	413
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		19	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		11	16
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		17	28
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		(10)	(19)
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 3 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties		130	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
FinancialAssetsFairValueDisclosure1		1,634	1,529
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(535)	(536)
FinancialAssetLiabilitiesNetFairValueDisclosure1		1,099	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		(535)	(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		(1,407)	(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		(25)	(26)
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],[3]	897	542
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] | 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
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] | 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] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	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	[5]	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 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] | 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] | 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] | 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] | 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] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		428	427
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] | 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] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[7]	21	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]
Investments, 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
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
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		21	19
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		21	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] | 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] | 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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		21	20
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		1,604	1,229
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		31	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],[3]	(767)	(481)
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		868	771
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 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] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effectsofnettingandallocationofcollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		41	42
Exelon Generation Co L L C [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Current		225	263
Derivative Liability, Noncurrent		180	153
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		238	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		164	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]	29	39
FinancialAssetsFairValueDisclosure1		14,148	12,718
Deferred Compensation Liability, Current and Noncurrent		(33)	(34)
Financial Liabilities Fair Value Disclosure		(438)	(450)
FinancialAssetLiabilitiesNetFairValueDisclosure1		13,710	12,268
Alternative Investment, Fair Value Disclosure		3,355	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		(394)	(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		(4,539)	(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] | 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],[3]	4,222	4,114
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] | 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			(10)
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		(20)	(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		(4)	(4)
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		13	23
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	[4]	12,670	11,092
Alternative Investment, Fair Value Disclosure	[4]	3,322	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	[5]	184	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		6,801	6,014
Alternative Investment, Fair Value Disclosure		2,104	2,011
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		4,541	3,977
Alternative Investment, Fair Value Disclosure		502	493
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,911	1,804
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		1,799	1,320
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		51	37
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		232	264
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	[6]	548	552
Alternative Investment, Fair Value Disclosure	[6]	502	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		506	498
Alternative Investment, Fair Value Disclosure		78	71
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		197	148
Alternative Investment, Fair Value Disclosure		197	148
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		441	326
Alternative Investment, Fair Value Disclosure		441	326
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	[7]	75	113
Alternative Investment, Fair Value Disclosure	[7]	33	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]
Investments, 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			2
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			17
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		54	83
Alternative Investment, Fair Value Disclosure		33	64
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		5	2
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		22	19
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] | 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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		4,934	5,090
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		81	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],[3]	(3,737)	(3,785)
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		1,278	1,381
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 hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		17	28
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		(13)	(21)
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		41	42
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]	29	39
FinancialAssetsFairValueDisclosure1		5,949	5,237
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(4)	(37)
FinancialAssetLiabilitiesNetFairValueDisclosure1		5,945	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		(3)	(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		(697)	(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		(4)	(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 Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	[2],[3]	698	1,233
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] | 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
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		(4)	(4)
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		3	4
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	5,864	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	[5]	117	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		3,980	3,551
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		1,767	1,291
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] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		1,767	1,291
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] | 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] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	0	0
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] | 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] | 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] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[7]	21	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]
Investments, 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
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure			16
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending 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] | 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		5	2
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		22	19
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] | 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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		632	1,356
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		3	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],[3]	(627)	(1,162)
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		8	197
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		0	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 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] | 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		(3)	(2)
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 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	0	0
FinancialAssetsFairValueDisclosure1		3,231	2,859
Deferred Compensation Liability, Current and Noncurrent		(33)	(34)
Financial Liabilities Fair Value Disclosure		(155)	(135)
FinancialAssetLiabilitiesNetFairValueDisclosure1		3,076	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		(112)	(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		(2,691)	(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		(48)	(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 Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	[2],[3]	2,627	2,339
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		(10)	(12)
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			(10)
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		(20)	(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] | 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		10	19
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	2,801	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	[5]	67	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		717	452
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		2,017	1,943
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		1,656	1,554
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		32	29
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		51	37
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		232	264
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	[6]	46	59
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] | 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] | 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] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[7]	0	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]
Investments, 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			2
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
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending 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 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] | 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] | 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] | 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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		2,698	2,505
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		47	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],[3]	(2,343)	(2,142)
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		402	413
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		8	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 hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		17	28
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		(10)	(19)
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 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	0	0
FinancialAssetsFairValueDisclosure1		1,613	1,509
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(279)	(278)
FinancialAssetLiabilitiesNetFairValueDisclosure1		1,334	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		(279)	(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		(1,151)	(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		(25)	(26)
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],[3]	897	542
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] | 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
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] | 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] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[4]	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	[5]	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | 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] | 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] | 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] | 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] | 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] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[6]	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		428	427
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] | 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] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	[7]	21	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]
Investments, 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
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
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		21	19
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] | 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] | 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] | 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] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		1,604	1,229
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		31	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],[3]	(767)	(481)
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		868	771
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 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] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effectsofnettingandallocationofcollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		41	42
Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Current		19	19
Derivative Liability, Noncurrent		237	239
Commonwealth Edison Co [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		39	36
Commonwealth Edison Co [Member] | Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		12	2
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[8]	0	20
FinancialAssetsFairValueDisclosure1		0	20
Total mark-to-market derivative liabilities	[9]	(256)	(258)
Deferred Compensation Liability, Current and Noncurrent		(7)	(8)
Financial Liabilities Fair Value Disclosure		(263)	(266)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(263)	(246)
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	[8]	0	20
FinancialAssetsFairValueDisclosure1		0	20
Total mark-to-market derivative liabilities	[9]	0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	20
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	[8]	0	0
FinancialAssetsFairValueDisclosure1		0	0
Total mark-to-market derivative liabilities	[9]	0	0
Deferred Compensation Liability, Current and Noncurrent		(7)	(8)
Financial Liabilities Fair Value Disclosure		(7)	(8)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(7)	(8)
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	[8]	0	0
FinancialAssetsFairValueDisclosure1		0	0
Total mark-to-market derivative liabilities	[9]	(256)	(258)
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(256)	(258)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(256)	(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
PECO Energy Co [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		21	22
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[8]	28	45
FinancialAssetsFairValueDisclosure1		45	62
Total mark-to-market derivative liabilities		0	0
Deferred Compensation Liability, Current and Noncurrent		(10)	(11)
Financial Liabilities Fair Value Disclosure		(10)	(11)
FinancialAssetLiabilitiesNetFairValueDisclosure1		35	51
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	[8]	28	45
FinancialAssetsFairValueDisclosure1		35	52
Total mark-to-market derivative liabilities		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		35	52
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	[8]	0	0
FinancialAssetsFairValueDisclosure1		10	10
Total mark-to-market derivative liabilities		0	0
Deferred Compensation Liability, Current and Noncurrent		(10)	(11)
Financial Liabilities Fair Value Disclosure		(10)	(11)
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	(1)
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	[8]	0	0
FinancialAssetsFairValueDisclosure1		0	0
Total mark-to-market derivative liabilities		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		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		12	13
Baltimore Gas and Electric Company [Member] | Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		3
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
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	[8]	5	36
FinancialAssetsFairValueDisclosure1		10	40
Total mark-to-market derivative liabilities		0	0
Deferred Compensation Liability, Current and Noncurrent		(4)	(4)
Financial Liabilities Fair Value Disclosure		(4)	(4)
FinancialAssetLiabilitiesNetFairValueDisclosure1		6	36
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	[8]	5	36
FinancialAssetsFairValueDisclosure1		10	40
Total mark-to-market derivative liabilities		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		10	40
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	[8]	0	0
FinancialAssetsFairValueDisclosure1		0	0
Total mark-to-market derivative liabilities		0	0
Deferred Compensation Liability, Current and Noncurrent		(4)	(4)
Financial Liabilities Fair Value Disclosure		(4)	(4)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(4)	(4)
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	[8]	0	0
FinancialAssetsFairValueDisclosure1		0	0
Total mark-to-market derivative liabilities		0	0
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		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
Pepco Holdings LLC [Member] | Successor [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		0	0
Total mark-to-market derivative liabilities		0	0
Derivative Liability, Current		0	0
Derivative Liability, Noncurrent		0	0
Pepco Holdings LLC [Member] | Successor [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		24	19
Pepco Holdings LLC [Member] | Successor [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		22	23
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	[10]	189	217
Derivative Asset	[11]	0	2
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0	(2)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0	0
FinancialAssetsFairValueDisclosure1		319	348
Deferred Compensation Liability, Current and Noncurrent		(24)	(28)
Financial Liabilities Fair Value Disclosure		(24)	(28)
FinancialAssetLiabilitiesNetFairValueDisclosure1		295	320
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		130	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		73	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		13	16
Pepco Holdings LLC [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		44	42
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	[10]	189	217
Derivative Asset	[11]	0	2
Collateral Amount Offset Against Fair Value Of Derivative Current Asset		0	(2)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0	0
FinancialAssetsFairValueDisclosure1		262	290
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		262	290
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		73	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		73	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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Pepco Holdings LLC [Member] | 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	[10]	0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0	0
FinancialAssetsFairValueDisclosure1		36	38
Deferred Compensation Liability, Current and Noncurrent		(24)	(28)
Financial Liabilities Fair Value Disclosure		(24)	(28)
FinancialAssetLiabilitiesNetFairValueDisclosure1		12	10
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		36	38
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [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		0	0
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		13	16
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Successor [Member] | 6311 Life Insurance [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	[10]	0	0
Derivative Asset	[11]		0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral		0	0
FinancialAssetsFairValueDisclosure1		21	20
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		21	20
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		21	20
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [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		0	0
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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		21	20
Potomac Electric Power Company [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		9
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[10]	144	33
FinancialAssetsFairValueDisclosure1		244	133
Deferred Compensation Liability, Current and Noncurrent		(4)	(5)
Financial Liabilities Fair Value Disclosure		(4)	(5)
FinancialAssetLiabilitiesNetFairValueDisclosure1		240	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		100	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		13	16
Potomac Electric Power Company [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		44	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	[10]	144	33
Investments, Fair Value Disclosure		0
FinancialAssetsFairValueDisclosure1		187	76
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		187	76
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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[10]	0	0
Investments, Fair Value Disclosure			0
FinancialAssetsFairValueDisclosure1		36	38
Deferred Compensation Liability, Current and Noncurrent		(4)	(5)
Financial Liabilities Fair Value Disclosure		(4)	(5)
FinancialAssetLiabilitiesNetFairValueDisclosure1		32	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		36	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		13	16
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		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]
Cash equivalents	[10]	0	0
Investments, Fair Value Disclosure		0	0
FinancialAssetsFairValueDisclosure1		21	19
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		21	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		21	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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		21	19
Delmarva Power and Light Company [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		6	4
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	[10]	0	42
Collateral Amount Offset Against Fair Value Of Derivative Current Asset			(2)
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	[11]		2
FinancialAssetsFairValueDisclosure1		0	42
Deferred Compensation Liability, Current and Noncurrent		(1)	(1)
Financial Liabilities Fair Value Disclosure		(1)	(1)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(1)	41
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[10]	0	42
Investments, Fair Value Disclosure		0	0
Derivative Asset	[11]		2
Collateral Amount Offset Against Fair Value Of Derivative Current Asset			(2)
FinancialAssetsFairValueDisclosure1		0	42
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		0	42
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[10]	0	0
Investments, Fair Value Disclosure		0	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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[10]	0	0
Investments, Fair Value Disclosure		0	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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		7	3
Atlantic City Electric Company [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		22	23
Atlantic City Electric Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[10]	29	130
FinancialAssetsFairValueDisclosure1		29	130
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		29	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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[10]	29	130
Investments, Fair Value Disclosure		0	0
FinancialAssetsFairValueDisclosure1		29	130
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		29	130
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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[10]	0	0
Investments, Fair Value Disclosure		0	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] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[10]	0	0
Investments, Fair Value Disclosure		0	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] | 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 $238 million and $252 million at June 30, 2017 and December 31, 2016 and restricted cash of $164 million and $157 million at June 30, 2017 and December 31, 2016. Exelon excludes cash of $353 million and $360 million at June 30, 2017 and December 31, 2016 and restricted cash of $203 million and $180 million at June 30, 2017 and December 31, 2016 and includes long term restricted cash of $25 million at June 30, 2017 and December 31, 2016, which is reported in other deferred debits on the balance sheet.
[2]	Collateral posted/(received) from counterparties totaled $71 million, $284 million and $130 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of June 30, 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]	Of the collateral posted/(received), $84 million represents variation margin on the exchanges as of June 30, 2017. Of the collateral posted/(received), $(158) million represents variation margin on the exchanges as of December 31, 2016.
[4]	Excludes net liabilities of $29 million and $31 million at June 30, 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.
[5]	Includes $48 million and $29 million of cash received from outstanding repurchase agreements at June 30, 2017 and December 31, 2016, respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (d) below.
[6]	Includes derivative instruments of $(1) million and $(2) million, which have a total notional amount of $771 million and $933 million at June 30, 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.
[7]	Excludes net assets of less than $1 million at June 30, 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.
[8]	ComEd excludes cash of $39 million and $36 million at June 30, 2017 and December 31, 2016 and restricted cash of $12 million and $2 million at June 30, 2017 and December 31, 2016. PECO excludes cash of $21 million and $22 million at June 30, 2017 and December 31, 2016. BGE excludes cash of $12 million and $13 million at June 30, 2017 and December 31, 2016 and restricted cash of $3 million at June 30, 2017 and includes long term restricted cash of $2 million at June 30, 2017 and December 31, 2016, which is reported in other deferred debits on the balance sheet.
[9]	The Level 3 balance consists of the current and noncurrent liability of $19 million and $237 million, respectively, at June 30, 2017, and $19 million and $239 million, respectively, at December 31, 2016, related to floating-to-fixed energy swap contracts with unaffiliated suppliers.
[10]	PHI excludes cash of $24 million and $19 million at June 30, 2017 and December 31, 2016 and includes long term restricted cash of $22 million and $23 million at June 30, 2017 and December 31, 2016 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $9 million at June 30, 2017 and December 31, 2016. DPL excludes cash of $6 million and $4 million at June 30, 2017 and December 31, 2016. ACE excludes cash of $7 million and $3 million at June 30, 2017 and December 31, 2016 and includes long term restricted cash of $22 million and $23 million at June 30, 2017 and December 31, 2016 which is reported in other deferred debits on the balance sheet.
[11]	Represents natural gas futures purchased by DPL as part of a natural gas hedging program approved by the DPSC.

Fair Value of Financial Asset67

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							6 Months Ended
		Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2016		Mar. 23, 2016	Jun. 30, 2017		Jun. 30, 2016		Mar. 31, 2017		Dec. 31, 2016		Mar. 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		$ 1,098		$ 1,185		$ 1,185			$ 1,098		$ 1,185		$ 1,046		$ 993		$ 1,547		$ 20		$ 1,529
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(2)		(423)					(40)		(427)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		0		0					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		1							1		2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets		30		52					15		38
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		31		(32)					69		(82)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		41		109					130		206
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		(13)		(2)					(15)		(4)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				(1)					(1)		(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(24)		(65)					(47)		(91)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		(8)		0					(10)		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(4)		0					3		(7)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		43		(260)					106		(40)
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		(4)		(8)					(13)		(12)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets		4		8					13		12
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		(46)		(164)					(148)		(389)
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)		1		4					7		11
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		1,334		1,386		1,386			1,334		1,386		1,308		1,231		1,792				1,776
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(2)		(424)					(41)		(428)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		4		8					13		12
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		1							1		2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets		0		0					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		31		(32)					69		(82)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		41		109					130		206
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		(13)		(2)					(15)		(4)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(24)		(65)					(47)		(91)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		(8)		0					(10)		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(4)		0					3		(7)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		43		(261)					105		(41)
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)		25		40					(5)		15
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		715		715			683		715		683		677		684				670
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1		4					4		6
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		4		8					13		12
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0							0		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 Liability Gain Loss Change In Collateral		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		19		85					36		119
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		(1)					0		(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(24)		(65)					(47)		(91)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0					0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		3					2		4
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		21		25		25			21		25		20		19		25				22
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		0		0					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		1							1		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 Liability Gain Loss Change In Collateral		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0					1		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0					0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0					0		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		589		609		609			589		609		565		493		1,047				1,051
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(3)	[1]	(428)	[2]				(46)	[1]	(434)	[2]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		0		0					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0							0		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 Liability Gain Loss Change In Collateral		31		(32)					69		(82)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		21		23					90		82
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		(13)		(1)					(15)		(3)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		(8)		0					(10)		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		(4)		0					8		(7)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		43		(264)					102		(45)
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		41		37		37			41		37		40		42		36				33
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		0					1		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		0		0					0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0							0		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 Liability Gain Loss Change In Collateral		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		1		1					3		4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0					0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0					(5)		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		0					1		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		(256)	[3]	(221)	[4]	(221)	[4]		(256)	[3]	(221)	[4]	(282)	[3]	(258)	[3]	(265)	[4]			(247)	[4]
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0	[3]	0	[4]				0	[3]	0	[4]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		0	[3]	0	[4]				0	[3]	0	[4]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0	[3]						0	[3]	0	[4]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets		26	[3]	44	[4]				2	[3]	26	[4]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		0	[3]	0	[4]				0	[3]	0	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0	[3]	0	[4]				0	[3]	0	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0	[3]	0	[4]				0	[3]	0	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0	[3]	0	[4]				0	[3]	0	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0	[3]	0	[4]				0	[3]	0	[4]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0	[3]	0	[4]				0	[3]	0	[4]
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	[3]	0	[4]				0	[3]	0	[4]
Purchases, sales, issuances and settlements
Ending balance	[4]			(221)		(221)					(221)
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	[5]																		20
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	[5]	20	[5]		20		20	[5]	20		20		20		$ 0	[5]
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		1		1	[5]		1
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		0		0		0	[5]		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0				0	[5]		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets		0		0		0	[5]		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		0		0		0	[5]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0		0	[5]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales		0		0		0	[5]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				(1)		(1)	[5]		(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0		0	[5]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3		0		0		0	[5]		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0		0	[5]		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0		1		1	[5]		1
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] | Predecessor [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													19
Total realized / unrealized gains (losses)
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
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Preferred Stock [Member] | Predecessor [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								0													18
Total realized / unrealized gains (losses)
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
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			20		20		$ 20		$ 20		$ 20				$ 19
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		1					1		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances		0		(1)					(1)		(1)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		$ 0		$ 1					$ 0		$ 2
[1]	Includes a reduction for the reclassification of $46 million and $148 million of realized gains due to the settlement of derivative contracts for the three and six months ended June 30, 2017.
[2]	Includes a reduction for the reclassification of $164 million and $389 million of realized gains due to the settlement of derivative contracts recorded in results of operations for the three and six months ended June 30, 2016.
[3]	Includes $25 million of increases in fair value and an increase for realized losses due to settlements of $1 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended June 30, 2017. Includes $5 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 six months ended June 30, 2017.
[4]	Includes $40 million of increases in fair value and an increase for realized losses due to settlements of $4 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended June 30, 2016. Includes $15 million of increases in fair value and an increase for realized losses due to settlements of $11 million for the six months ended June 30, 2016.
[5]	Successor period represents activity from March 24, 2016 through June 30, 2016. See tables below for PHI's predecessor periods, as well as activity for Pepco for the three and six months ended June 30, 2017 and 2016.

Fair Value of Financial Asset68

Fair Value of Financial Assets and Liabilities Fair Value of Financial Assets and Liabilities - Narrative (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spent Nuclear Fuel Obligation, Noncurrent	$ 1,139,000,000	$ 1,024,000,000
Forward Power Basis	2.86
Forward Gas Basis	0.41
Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spent Nuclear Fuel Obligation, Noncurrent	1,139,000,000	$ 1,024,000,000
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	280,000,000
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	218,000,000
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	98,000,000
Fitzpatrick [Member] | Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spent Nuclear Fuel Obligation, Noncurrent	$ 110,000,000

Fair Value of Financial Asset69

Fair Value of Financial Assets and Liabilities - Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Millions		3 Months Ended					6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2016	[2]	Mar. 23, 2016	Jun. 30, 2017	Jun. 30, 2016
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		$ 2	$ 423				$ 40	$ 427
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		43	(260)				106	(40)
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		(51)	(462)				37	(413)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	(274)				140	(20)
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		48	34				(83)	(21)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		43	10				(38)	(25)
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	5				6	7
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[1]	0	4				4	5
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, Gain (Loss) Included in Earnings		2	424				41	428
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		43	(261)				105	(41)
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		(51)	(462)				37	(413)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	(274)				140	(20)
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		48	34				(83)	(21)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		43	10				(38)	(25)
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]	1	4				5	6
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[1]	0	3				3	4
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]	0	1				1	1
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[1]	0	1				1	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	[1]					$ (17)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[1]					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]	0	1				1	2
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[1]	0	1				1	2
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, Gain (Loss) Included in Earnings		0	(1)	$ (1)			(1)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		0	1	$ 1			1
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, Gain (Loss) Included in Earnings						(1)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)						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, Gain (Loss) Included in Earnings		0	(1)				(1)	(2)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		$ 0	$ 1				$ 0	$ 2
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, 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, accrued interest on a convertible promissory note at Generation and the life insurance contracts held by PHI and Pepco.
[2]	Successor period represents activity from March 24, 2016 through June 30, 2016. See tables below for PHI's predecessor periods, as well as activity for Pepco for the three and six months ended June 30, 2017 and 2016.

Fair Value of Financial Asset70

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details) - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2017		Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Cash Collateral Posted	$ 19,000,000
Exelon Generation Co L L C [Member]
Derivatives, Fair Value [Line Items]
Cash Collateral Posted	517,000,000		$ 347,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Cash Collateral Posted	130,000,000		61,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	453,000,000	[1],[2]	435,000,000	[3],[4]
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [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] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	124		130
Forward gas price assets	$ 9.37		$ 9.2
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Volatility percentage	11.00%		8.00%
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Volatility percentage	253.00%		173.00%
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ 6,000,000	[1],[2]	$ (3,000,000)	[3],[4]
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	11		19
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	73		79
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ (256,000,000)		$ (258,000,000)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Forward heat rate	9.00%		8.00%
Derivatives Fair Value Footnotes [Abstract]
Fair Value Inputs, Discount for Lack of Marketability	3.00%		3.00%
Fair Value Inputs Renewable Factor	89.00%		89.00%
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward heat rate	10.00%		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]	The fair values do not include cash collateral posted on level three positions of $130 million as of June 30, 2017.
[2]	The valuation techniques, unobservable inputs and ranges are the same for the asset and liability positions.
[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 Instrume71

Derivative Financial Instruments - Summary of Interest Rate and Foreign Currency Hedges (Details) - USD ($) $ in Millions		Jun. 30, 2017		Dec. 31, 2016
Derivative [Line Items]
Mark-to-market derivatives assets		$ 833		$ 917
Derivative Asset, Noncurrent		464		492
Derivative Liability, Current		(244)		(282)
Derivative Liability, Noncurrent		(417)		(392)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		833		917
Derivative Asset, Noncurrent		453		476
Derivative Liability, Current		(225)		(263)
Derivative Liability, Noncurrent		(180)		(153)
InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		6		8
Derivative Asset, Noncurrent		13		20
Total mark-to-market derivative assets		19		28
Derivative Liability, Current		(10)		(8)
Derivative Liability, Noncurrent		(1)		(4)
Derivative Liability		11		12
Total mark-to-market derivative net assets (liabilities)		8		16
InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		6		8
Derivative Asset, Noncurrent		2		4
Total mark-to-market derivative assets		8		12
Derivative Liability, Current		(10)		(8)
Derivative Liability, Noncurrent		(1)		(4)
Derivative Liability		11		12
Total mark-to-market derivative net assets (liabilities)		(3)		0
Collateral And Netting [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	[1]	(2,429)	[2]	(2,769)	[3]
Derivative Asset, Noncurrent	[1]	(1,308)	[2]	(1,016)	[3]
Total mark-to-market derivative assets	[1]	(3,737)	[2]	(3,785)	[3]
Derivative Liability, Current	[1]	2,732	[2]	2,964	[3]
Derivative Liability, Noncurrent	[1]	1,490	[2]	1,150	[3]
Derivative Liability	[1]	(4,222)	[2]	(4,114)	[3]
Total mark-to-market derivative net assets (liabilities)	[1]	485	[2]	329	[3]
Collateral And Netting [Member] | InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		(11)	[4]	(13)
Derivative Asset, Noncurrent		(2)	[4]	(8)
Total mark-to-market derivative assets		(13)	[4]	(21)
Derivative Liability, Current		11		14
Derivative Liability, Noncurrent		2		9
Derivative Liability		(13)		(23)
Total mark-to-market derivative net assets (liabilities)		0		2
Designated as Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		0		0
Derivative Asset, Noncurrent		0		0
Total mark-to-market derivative assets		0		0
Derivative Liability, Current		0		(7)
Derivative Liability, Noncurrent		0		(3)
Derivative Liability		0		10
Total mark-to-market derivative net assets (liabilities)		0		(10)
Designated as Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member] | Corporate, Non-Segment [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		0		0
Derivative Asset, Noncurrent		11		16
Total mark-to-market derivative assets		11		16
Derivative Liability, Current		0		0
Derivative Liability, Noncurrent		0		0
Derivative Liability		0		0
Total mark-to-market derivative net assets (liabilities)		11		16
Not Designated as Hedging Instrument, Economic Hedge [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		3,198		3,623
Derivative Asset, Noncurrent		1,736		1,467
Total mark-to-market derivative assets		4,934		5,090
Derivative Liability, Current		(2,895)		(3,165)
Derivative Liability, Noncurrent		(1,644)		(1,274)
Derivative Liability		4,539		4,439
Total mark-to-market derivative net assets (liabilities)		395		651
Not Designated as Hedging Instrument, Economic Hedge [Member] | InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		14		17
Derivative Asset, Noncurrent		3		11
Total mark-to-market derivative assets		17		28
Derivative Liability, Current		(17)		(13)
Derivative Liability, Noncurrent		(3)		(8)
Derivative Liability		20		21
Total mark-to-market derivative net assets (liabilities)		(3)		7
Not Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		58		55
Derivative Asset, Noncurrent		23		21
Total mark-to-market derivative assets		81		76
Derivative Liability, Current		(52)		(54)
Derivative Liability, Noncurrent		(25)		(25)
Derivative Liability		77		79
Total mark-to-market derivative net assets (liabilities)		4		(3)
Not Designated as Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		3	[5]	4
Derivative Asset, Noncurrent		1	[5]	1
Total mark-to-market derivative assets		4	[5]	5
Derivative Liability, Current		(4)	[5]	(2)
Derivative Liability, Noncurrent		0	[5]	(2)
Derivative Liability		4	[5]	4
Total mark-to-market derivative net assets (liabilities)		$ 0	[5]	$ 1
[1]	Exelon, Generation, PHI and DPL net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above.
[2]	Of the collateral posted/(received), $84 million represents variation margin on the exchanges.
[3]	Of the collateral posted/(received), $(158) million represents variation margin on the exchanges.
[4]	Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases, Exelon and Generation may have other offsetting 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.
[5]	Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts between the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates.

Derivative Financial Instrume72

Derivative Financial Instruments - Summary of Gains and Losses on Hedges (Details) - Interest Expense [Member] - Fair Value Hedging [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Interest Rate Swap [Member]
Derivative [Line Items]
Gain (loss) on Swaps	$ 1	$ 5	$ (4)	$ 22
Price Risk Derivative [Member]
Derivative [Line Items]
Gain (loss) on Borrowings	$ 2	$ (1)	$ 10	$ (16)

Derivative Financial Instrume73

Derivative Financial Instruments Derivative Financial Instruments - Summary of Derivative Fair Value Balances (Details) - USD ($) $ in Millions		Jun. 30, 2017		Dec. 31, 2016
Derivative [Line Items]
Mark-to-market derivative assets		$ 833		$ 917
Derivative Asset, Noncurrent		464		492
Derivative Liability, Current		(244)		(282)
Derivative Liability, Noncurrent		(417)		(392)
Margin Deposit Assets		(84)		158
Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets		827		909
Derivative Asset, Noncurrent		451		472
Total mark-to-market derivative assets		1,278		1,381
Derivative Liability, Current		(234)		(274)
Derivative Liability, Noncurrent		(416)		(388)
Total mark-to-market derivative liabilities		(650)		(662)
Total mark-to-market derivative net assets (liabilities)		628		719
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets		833		917
Derivative Asset, Noncurrent		453		476
Derivative Liability, Current		(225)		(263)
Derivative Liability, Noncurrent		(180)		(153)
Derivative Liability, Fair Value, Amount Offset Against Collateral	[1]	(601)		(627)
Exelon Generation Co L L C [Member] | Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets	[2]	827		909
Derivative Asset, Noncurrent	[2]	451		472
Total mark-to-market derivative assets	[2]	1,278		1,381
Derivative Liability, Current	[2]	(215)		(255)
Derivative Liability, Noncurrent	[2]	(179)		(149)
Total mark-to-market derivative liabilities	[2]	(394)		(404)
Total mark-to-market derivative net assets (liabilities)	[2]	884		977
Commonwealth Edison Co [Member]
Derivative [Line Items]
Derivative Liability, Current		(19)		(19)
Derivative Liability, Noncurrent		(237)		(239)
Delmarva Power and Light Company [Member] | Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets	[3]	0		0
Derivative Asset, Noncurrent	[3]	0		0
Total mark-to-market derivative assets	[3]	0		0
Derivative Liability, Current	[3]	0		0
Derivative Liability, Noncurrent	[3]	0		0
Total mark-to-market derivative liabilities	[3]	0		0
Total mark-to-market derivative net assets (liabilities)		0		0
Pepco Holdings LLC [Member] | Successor [Member]
Derivative [Line Items]
Mark-to-market derivative assets		0		0
Derivative Asset, Noncurrent		0		0
Total mark-to-market derivative assets		0		0
Derivative Liability, Current		0		0
Derivative Liability, Noncurrent		0		0
Total mark-to-market derivative liabilities		0		0
Total mark-to-market derivative net assets (liabilities)		0		0
Collateral And Netting [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets	[4]	(2,429)	[5]	(2,769)	[6]
Derivative Asset, Noncurrent	[4]	(1,308)	[5]	(1,016)	[6]
Total mark-to-market derivative assets	[4]	(3,737)	[5]	(3,785)	[6]
Derivative Liability, Current	[4]	2,732	[5]	2,964	[6]
Derivative Liability, Noncurrent	[4]	1,490	[5]	1,150	[6]
Total mark-to-market derivative liabilities	[4]	4,222	[5]	4,114	[6]
Total mark-to-market derivative net assets (liabilities)	[4]	485	[5]	329	[6]
Collateral And Netting [Member] | Delmarva Power and Light Company [Member]
Derivative [Line Items]
Mark-to-market derivative assets	[4]	0		(2)
Derivative Asset, Noncurrent	[4]	0		0
Total mark-to-market derivative assets	[4]	0		(2)
Derivative Liability, Current	[4]	0		0
Derivative Liability, Noncurrent	[4]	0		0
Total mark-to-market derivative liabilities	[4]	0		0
Total mark-to-market derivative net assets (liabilities)	[4]	0		(2)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets		3,198		3,623
Derivative Asset, Noncurrent		1,736		1,467
Total mark-to-market derivative assets		4,934		5,090
Derivative Liability, Current		(2,895)		(3,165)
Derivative Liability, Noncurrent		(1,644)		(1,274)
Total mark-to-market derivative liabilities		(4,539)		(4,439)
Total mark-to-market derivative net assets (liabilities)		395		651
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commonwealth Edison Co [Member]
Derivative [Line Items]
Mark-to-market derivative assets	[7]	0		0
Derivative Asset, Noncurrent	[7]	0		0
Total mark-to-market derivative assets	[7]	0		0
Derivative Liability, Current	[7]	(19)		(19)
Derivative Liability, Noncurrent	[7]	(237)		(239)
Total mark-to-market derivative liabilities	[7]	(256)		(258)
Total mark-to-market derivative net assets (liabilities)	[7]	(256)		(258)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Delmarva Power and Light Company [Member]
Derivative [Line Items]
Mark-to-market derivative assets	[8]	0		2
Derivative Asset, Noncurrent	[8]	0		0
Total mark-to-market derivative assets	[8]	0		2
Derivative Liability, Current	[8]	0		0
Derivative Liability, Noncurrent	[8]	0		0
Total mark-to-market derivative liabilities	[8]	0		0
Total mark-to-market derivative net assets (liabilities)	[8]	0		2
Not Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets		58		55
Derivative Asset, Noncurrent		23		21
Total mark-to-market derivative assets		81		76
Derivative Liability, Current		(52)		(54)
Derivative Liability, Noncurrent		(25)		(25)
Total mark-to-market derivative liabilities		(77)		(79)
Total mark-to-market derivative net assets (liabilities)		4		(3)
Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Current assets collateral offset		149		100
Noncurrent assets collateral offset		74		72
Current liabilities collateral offset		155		95
Noncurrent liabilities collateral offset		107		62
Total cash collateral received net of cash collateral posted		485		329
Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member] | Other Current Assets [Member]
Derivative [Line Items]
Margin Deposit Assets		$ 84
Derivative Liability, Fair Value, Amount Offset Against Collateral				$ (158)
[1]	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.
[2]	Current and noncurrent assets are shown net of collateral of $149 million and $74 million, respectively, and current and noncurrent liabilities are shown net of collateral of $155 million and $107 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $485 million at June 30, 2017.
[3]	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.
[4]	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.
[5]	Of the collateral posted/(received), $84 million represents variation margin on the exchanges.
[6]	Of the collateral posted/(received), $(158) million represents variation margin on the exchanges.
[7]	Includes current and noncurrent liabilities relating to floating-to-fixed energy swap contracts with unaffiliated suppliers.
[8]	Represents natural gas futures purchased by DPL as part of a natural gas hedging program approved by the DPSC.

Derivative Financial Instrume74

Derivative Financial Instruments - Summary of AOCI related to Cash Flow Hedges (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative [Line Items]
Beginning Balance				$ (2,660)
Ending Balance		$ (2,633)		(2,633)
Income taxes		(72)	$ 102	143	$ 285
Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning Balance		(11)	(26)		(19)
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net		(1)			(10)
Ending Balance		(12)	(26)	(12)	(26)
Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Income taxes	[1]			(3)	(2)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Beginning Balance				(54)
Ending Balance		(40)		(40)
Income taxes		(158)	(31)	(31)	120
Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning Balance		(13)	(26)		(21)
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net		(1)			(7)
Ending Balance		$ (14)	(25)	$ (14)	(25)
Interest Expense [Member] | Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion			0		3
Interest Expense [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion			$ 1		$ 3
[1]	Amounts in parenthesis represent a decrease in net income.

Derivative Financial Instrume75

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			$ (230)	$ (194)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	$ (184)	$ (304)	(233)	(201)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			(235)	(199)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(184)	(304)	(233)	(201)
Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(143)	(615)	(99)	(553)
Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(41)	311	(134)	352
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	0	(3)	(2)	(4)
Unrealized Gain (Loss) on Derivatives	(2)	(2)	(3)	(8)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(2)	1	(1)	(4)
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	0	0
Unrealized Gain (Loss) on Derivatives	0	0	0	0
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	0	0	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	0	(3)	(2)	(4)
Unrealized Gain (Loss) on Derivatives	(2)	(2)	(3)	(8)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(2)	1	(1)	(4)
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	0	(3)	(2)	(4)
Unrealized Gain (Loss) on Derivatives	(2)	(2)	(3)	(8)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(2)	1	(1)	(4)
Commodity Contract [Member] | Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	(100)	(432)	(9)	(153)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(41)	(181)	(87)	(392)
Unrealized Gain (Loss) on Derivatives	(141)	(613)	(96)	(545)
Commodity Contract [Member] | Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	(62)	235	(197)	109
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	21	76	63	243
Unrealized Gain (Loss) on Derivatives	(41)	311	(134)	352
Commodity Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	(162)	(197)	(206)	(44)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(20)	(105)	(24)	(149)
Unrealized Gain (Loss) on Derivatives	(182)	(302)	(230)	(193)
Commodity Contract [Member] | Interest Expense [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	(162)	(197)	(206)	(44)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(20)	(105)	(24)	(149)
Unrealized Gain (Loss) on Derivatives	$ (182)	$ (302)	$ (230)	$ (193)

Derivative Financial Instrume76

Derivative Financial Instruments - Summary of Proprietary Trading Activities (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			$ (230)	$ (194)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	$ (184)	$ (304)	(233)	(201)
Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	0	(1)	(2)	2
Commodity Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	6	5	6	14
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(6)	(5)	(7)	(11)
Unrealized Gain (Loss) on Derivatives	0	0	(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	0	(1)	0	1
Unrealized Gain (Loss) on Derivatives	0	(1)	(1)	(1)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	$ 0	$ 0	$ (1)	$ (2)

Derivative Financial Instrume77

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Cash Collateral Posted		$ 19
Letters Of Credit Posted		10
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Financial institutions		89
Investor-owned utilities, marketers and power producers		563
Energy Cooperatives And Municipalities		560
Other		134
Cash Collateral Posted		517	$ 347
Letters Of Credit Posted		278	$ 284
Exelon Generation Co L L C [Member] | Total Exposure Before Credit Collateral [Member]
Derivative [Line Items]
Investment grade		878
Non-investment grade		47
No external ratings - internally rated - investment grade		327
No external ratings - internally rated - non-investment grade		123
Total		1,375
Exelon Generation Co L L C [Member] | Credit Collateral [Member]
Derivative [Line Items]
Investment grade		14
Non-investment grade		1
No external ratings - internally rated - investment grade		0
No external ratings - internally rated - non-investment grade		14
Total	[1]	29
Exelon Generation Co L L C [Member] | Net Exposure [Member]
Derivative [Line Items]
Investment grade		864
Non-investment grade		46
No external ratings - internally rated - investment grade		327
No external ratings - internally rated - non-investment grade		109
Total		1,346
Exelon Generation Co L L C [Member] | 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
Exelon Generation Co L L C [Member] | Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Investment grade		299
Non-investment grade		0
No external ratings - internally rated - investment grade		0
No external ratings - internally rated - non-investment grade		0
Total		$ 299
[1]	As of June 30, 2017, credit collateral held from counterparties where Generation had credit exposure included $19 million of cash and $10 million of letters of credit. The credit collateral does not include non-liquid collateral.

Derivative Financial Instrume78

Derivative Financial Instruments - Summary of Credit Risk Related Contingent Features (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Aggregate fair value of derivatives with credit-risk-related contingent features	[1]	$ (942)	$ (960)
Contractual right of offset related to derivative assets	[2]	601	627
Net liability position after contractual right of offset	[3]	$ (341)	$ (333)
[1]	Amount represents the gross fair value of out-of-the-money derivative contracts containing credit-risk related contingent features ignoring the effects of master netting agreements.
[2]	Amount represents the offsetting fair value of in-the-money derivative contracts under legally enforceable master netting agreements with the same counterparty, which reduces the amount of any liability for which a Registrant could potentially be required to post collateral.
[3]	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.

Derivative Financial Instrume79

Derivative Financial Instruments - Narrative (Details) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2017USD ($)GWh	Jun. 30, 2016USD ($)GWh	Jun. 30, 2017USD ($)GWh	Jun. 30, 2016USD ($)GWh	Dec. 31, 2016USD ($)	Mar. 31, 2017USD ($)	Mar. 31, 2016USD ($)
Derivative [Line Items]
Income taxes		$ (72,000)	$ 102,000	$ 143,000	$ 285,000
Derivative, Notional Amount			100,000		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				3,000
Ineffective portion recognized in income		3,000	4,000	7,000	6,000
Mark-to-market derivative liabilities (noncurrent liabilities)		417,000		417,000		$ 392,000
Cash collateral posted		19,000		19,000
Letters of credit posted		10,000		10,000
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes		(158,000)	$ (31,000)	(31,000)	$ 120,000
Mark-to-market derivative liabilities (noncurrent liabilities)		180,000		180,000		153,000
Cash collateral received not offset against net derivative positions		(2,000)		(2,000)		(8,000)
Cash collateral posted		517,000		517,000		347,000
Letters of credit held		21,000		21,000		28,000
Letters of credit posted		278,000		278,000		284,000
Cash collateral held		34,000		34,000		24,000
Incremental collateral for loss of investment grade credit rating		1,800,000		1,800,000		1,900,000
Interest Rate Fair Value Hedge Asset at Fair Value		$ (3,000)		$ (3,000)
Derivative, Nonmonetary Notional Amount, Energy Measure | GWh		2,312	1,289	4,162	2,509
Commonwealth Edison Company [Member]
Derivative [Line Items]
Cash collateral held		$ 13,000		$ 13,000
Commonwealth Edison Co [Member]
Derivative [Line Items]
Income taxes		104,000	$ 91,000	197,000	$ 168,000
Mark-to-market derivative liabilities (noncurrent liabilities)		237,000		237,000		239,000
Cash collateral held		19,000		19,000
Incremental collateral for loss of investment grade credit rating		12,000		12,000
Credit Exposure Under Off System Sales		1,000		1,000
PECO Energy Co [Member]
Derivative [Line Items]
Income taxes		20,000	23,000	$ 55,000	67,000
Estimated percentage of natural gas purchases hedged				20.00%
Incremental collateral for loss of investment grade credit rating		21,000		$ 21,000
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Income taxes		31,000	6,000	111,000	73,000
Incremental collateral for loss of investment grade credit rating		36,000		36,000
Credit Exposure Under Off System Sales		1,000		1,000
Delmarva Power and Light Company [Member]
Derivative [Line Items]
Income taxes		12,000	$ 8,000	24,000	(1,000)
Incremental collateral for loss of investment grade credit rating		10,000		$ 10,000
Minimum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months				96.00%
Expected Generation Hedged In Year Two				71.00%
Expected generation hedged in year three				39.00%
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				99.00%
Expected Generation Hedged In Year Two				74.00%
Expected generation hedged in year three				42.00%
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		$ 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		492,000		492,000
Foreign Exchange Contract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Notional Amount		103,000		103,000
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		628,000		628,000		719,000
Mark-to-market derivative liabilities (noncurrent liabilities)		416,000		416,000		388,000
Derivative [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	[1]	884,000		884,000		977,000
Mark-to-market derivative liabilities (noncurrent liabilities)	[1]	179,000		179,000		149,000
Derivative [Member] | Delmarva Power and Light Company [Member]
Derivative [Line Items]
Derivative, Fair Value, Net		0		0		0
Mark-to-market derivative liabilities (noncurrent liabilities)	[2]	0		0		0
InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Derivative, Fair Value, Net		8,000		8,000		16,000
Mark-to-market derivative liabilities (noncurrent liabilities)		1,000		1,000		4,000
InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Fair Value, Net		(3,000)		(3,000)		0
Mark-to-market derivative liabilities (noncurrent liabilities)		1,000		1,000		4,000
Fair Value Hedging [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		800,000		800,000		800,000
Increase (Decrease) in Fair Value of Interest Rate Fair Value Hedging Instruments				11,000		$ 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		492,000		492,000
ExGen Texas Power [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities (noncurrent liabilities)		8,000		8,000
ExGen Renewables [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount							$ 164,000
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Income taxes	[3]			(3,000)	(2,000)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Income taxes		0
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes		0
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	[3]			3,000	2,000
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes	[3]			3,000	$ 2,000
Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		23,000		23,000
PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from affiliated electric and gas utility		27,000		27,000
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		21,000		21,000
Potomac Electric Power Company [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		41,000		41,000
Delmarva Power and Light Company [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		12,000		12,000
Atlantic City Electric Company [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		$ 6,000		$ 6,000
[1]	Current and noncurrent assets are shown net of collateral of $149 million and $74 million, respectively, and current and noncurrent liabilities are shown net of collateral of $155 million and $107 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $485 million at June 30, 2017.
[2]	Current and noncurrent assets are shown net of collateral of $100 million and $72 million, respectively, and current and noncurrent liabilities are shown net of collateral of $95 million and $62 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $329 million at December 31, 2016.
[3]	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	Jun. 30, 2017	Dec. 31, 2016
Corporate, Non-Segment [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	$ 0	$ 0
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	42	0
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	569	620
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	389	0
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	85	45
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	0	23
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	$ 25	$ 0

Debt and Credit Agreements - Is

Debt and Credit Agreements - Issuance of Long-Term Debt (Details) - USD ($)	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2014
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.497%	2.50%
JSNotes350June2022 [Member] | Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Interest Rate	3.50%
Debt Instrument, Face Amount	$ 1,150,000,000
Exelon Generation Co L L C [Member] | EEPFNotes372April2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.72%
Debt Instrument, Face Amount	$ 3,000,000
Exelon Generation Co L L C [Member] | EEPF261Sep2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	2.61%
Debt Instrument, Face Amount	$ 6,000,000
Exelon Generation Co L L C [Member] | EEPFNotes390Jan2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.90%
Debt Instrument, Face Amount	$ 12,000,000
Exelon Generation Co L L C [Member] | AGEPFNotesNov2017 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 13,000,000
Debt Instrument, Interest Rate Terms	LIBOR + 1.25%
Exelon Generation Co L L C [Member] | SeniorUnsecured295Jan2020 [Member] | Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Interest Rate	2.95%
Debt Instrument, Face Amount	$ 250,000,000
Exelon Generation Co L L C [Member] | EEPF353Apr2019 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.53%
Debt Instrument, Face Amount	$ 8,000,000
Exelon Generation Co L L C [Member] | SeniorUnsecured340Mar2022 [Member] | Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Interest Rate	3.40%
Debt Instrument, Face Amount	$ 500,000,000
Exelon Generation Co L L C [Member] | EGTP475Sep2021 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 6,000,000
Debt Instrument, Interest Rate Terms	LIBOR + 4.75%
Potomac Electric Power Company [Member] | FMB415Mar2043 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate	4.15%
Debt Instrument, Face Amount	$ 200,000,000
Potomac Electric Power Company [Member] | EEPFNotes330December2017 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.30%
Debt Instrument, Face Amount	$ 1,000,000

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

6 Months Ended

9 Months Ended

Jun. 30, 2014

Jun. 30, 2017

Jun. 30, 2017

Jun. 30, 2016

Sep. 30, 2014

Mar. 23, 2017

Jan. 09, 2017

May 26, 2016

Jan. 13, 2016

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

$ 1,150

Extinguishment of Debt, Amount

$ 11

Junior Subordinated Debt [Member]

Debt Instrument [Line Items]

Junior Subordinated Notes

$ 1,150

$ 1,150

Equity Units Issued

23

Debt Instrument, Convertible, Conversion Price

$ 50

Interest Rate

2.50%

3.497%

3.497%

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

33

33

Loss on Reissuance, Treasury Stock

$ 1,050

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

$ 75

Baltimore Gas and Electric Company [Member]

Debt Instrument [Line Items]

Preferred Stock, Par or Stated Value Per Share

$ 25.19

$ 25.19

Preferred Stock, Dividend Rate, Percentage

6.20%

Preferred Stock, Redemption Amount, Future Redeemable Securities

$ 258

$ 258

ExGen Texas Power [Member] | Exelon Generation Co L L C [Member] | Long-term Debt [Member]

Debt Instrument [Line Items]

Long-term Debt

662

662

$ 675

Debt Instrument, Interest Rate Terms

LIBOR plus 4.75%

Line of Credit Facility, Maximum Borrowing Capacity

$ 20

$ 20

Non Recourse Debt Interest Rate Swap

$ 505

Interest Rate

2.34%

Income Taxes - Reconciliation t

Income Taxes - Reconciliation to Effective Tax Rate (Details)		Mar. 31, 2016		Jun. 30, 2017		Jun. 30, 2016		Mar. 23, 2016	Jun. 30, 2017	Jun. 30, 2016
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate				35.00%	[1]	35.00%			35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit				(2745.70%)	[1]	2.30%			(1.00%)	0.80%
Qualified nuclear decommissioning trust fund income				3156.60%	[1]	5.70%			5.60%	5.60%
Amortization of investment tax credit, including deferred taxes on basis difference				(528.70%)	[1]	(1.80%)			(0.70%)	(1.70%)
Plant basis differences				(2764.40%)	[1]	(6.90%)			(4.30%)	(6.30%)
Production tax credits and other credits				(1035.70%)	[1]	(5.80%)			(1.40%)	(5.50%)
Noncontrolling interests				84.70%	[1]	0.90%			(0.10%)	0.70%
Statute of limitations expiration						(1.70%)				(1.00%)
Merger expenses						0.20%			(11.40%)	14.50%
Fitzpatrick bargain purchase gain									(6.50%)
Like-kind exchange(c)				(5362.40%)	[2]				(3.70%)
Other				1960.60%	[1]	(3.30%)			0.30%	(2.80%)
Effective income tax rate				(7200.00%)	[1]	24.60%			11.80%	39.30%
Exelon Generation Co L L C [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate				35.00%	[3]	35.00%			35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit				5.60%	[3]	(116.70%)			(13.60%)	2.60%
Qualified nuclear decommissioning trust fund income				(6.30%)	[3]	591.20%			51.20%	9.80%
Amortization of investment tax credit, including deferred taxes on basis difference				0.90%	[3]	(157.80%)			(5.40%)	(2.50%)
Plant basis differences				0.00%	[3]	0.00%			0.00%	0.00%
Production tax credits and other credits				2.00%	[3]	(603.00%)			(12.30%)	(9.60%)
Noncontrolling interests				(0.20%)	[3]	94.40%			(0.50%)	1.20%
Statute of limitations expiration						(410.80%)				(3.90%)
Merger expenses						0.00%			(13.70%)	0.00%
Fitzpatrick bargain purchase gain									(60.00%)
Like-kind exchange(c)				0.00%	[3]				0.00%
Other				1.10%	[3]	(52.30%)			(4.20%)	(3.80%)
Effective income tax rate				38.10%	[3]	(620.00%)	[4]		(23.50%)	28.80%
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate				35.00%		35.00%			35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit				5.80%		4.80%			5.30%	4.90%
Qualified nuclear decommissioning trust fund income				(0.00%)		(0.00%)			(0.00%)	(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference				(0.20%)		(0.20%)			(0.20%)	(0.20%)
Plant basis differences				(0.20%)		(0.40%)			(0.20%)	(0.30%)
Production tax credits and other credits				0.00%		0.00%			0.00%	0.00%
Noncontrolling interests				0.00%		0.00%			0.00%	0.00%
Statute of limitations expiration						0.00%
Merger expenses						0.00%			0.00%	0.00%
Fitzpatrick bargain purchase gain									0.00%
Like-kind exchange(c)				5.90%					2.90%
Other				0.50%		(0.60%)			0.40%	(0.10%)
Effective income tax rate				46.80%		38.60%			43.20%	39.30%
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate				35.00%		35.00%			35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit				(0.60%)		0.30%			(0.10%)	0.70%
Qualified nuclear decommissioning trust fund income				(0.00%)		(0.00%)			(0.00%)	(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference				(0.10%)		(0.10%)			(0.10%)	(0.10%)
Plant basis differences				(16.00%)		(11.30%)			(14.30%)	(10.20%)
Production tax credits and other credits				0.00%		0.00%			0.00%	0.00%
Noncontrolling interests				0.00%		0.00%			0.00%	0.00%
Statute of limitations expiration						0.00%
Merger expenses						0.00%			0.00%	0.00%
Fitzpatrick bargain purchase gain									0.00%
Like-kind exchange(c)				0.00%					0.00%
Other				0.20%		(5.20%)	[5]		(0.10%)	(2.40%)	[5]
Effective income tax rate				18.50%		18.70%			20.40%	23.00%
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate				35.00%		35.00%			35.00%	35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit				5.00%		2.00%			5.10%	4.60%
Qualified nuclear decommissioning trust fund income				(0.00%)		(0.00%)			(0.00%)	(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference				(0.20%)		(0.40%)			(0.10%)	(0.10%)
Plant basis differences				(0.30%)		(20.60%)	[6]		(0.70%)	(4.50%)
Production tax credits and other credits				0.00%		0.00%			0.00%	0.00%
Noncontrolling interests				0.00%		0.00%			0.00%	0.00%
Statute of limitations expiration						0.00%
Merger expenses						0.00%			0.00%	0.00%
Fitzpatrick bargain purchase gain									0.00%
Like-kind exchange(c)				0.00%					0.00%
Other				1.30%		(1.00%)			0.30%	0.10%
Effective income tax rate				40.80%		15.00%	[7]		39.60%	35.10%
Potomac Electric Power Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate				35.00%		35.00%			35.00%	35.00%	[8]
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit				3.20%		3.50%			3.80%	(9.50%)	[9]
Qualified nuclear decommissioning trust fund income				(0.00%)		(0.00%)			(0.00%)	(0.00%)	[8]
Amortization of investment tax credit, including deferred taxes on basis difference				(0.10%)		(0.10%)			(0.10%)	0.10%
Plant basis differences				(6.20%)		(5.70%)			(6.00%)	12.60%	[8]
Production tax credits and other credits				0.00%		0.00%			0.00%	0.00%	[8]
Noncontrolling interests				0.00%		0.00%			0.00%	0.00%	[8]
Statute of limitations expiration	[8]					0.00%
Merger expenses						0.20%			(16.20%)	(36.10%)	[8]
Fitzpatrick bargain purchase gain									0.00%
Like-kind exchange(c)				0.00%					0.00%
Other				(0.20%)		(1.00%)			(0.70%)	(0.50%)	[8]
Effective income tax rate				31.70%		31.90%			15.80%	1.60%	[8]
Delmarva Power and Light Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate				35.00%		35.00%			35.00%	35.00%	[8]
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit				4.60%		4.80%			5.10%	(5.20%)	[9]
Qualified nuclear decommissioning trust fund income				(0.00%)		(0.00%)			(0.00%)	(0.00%)	[8]
Amortization of investment tax credit, including deferred taxes on basis difference				(0.10%)	[8]	(0.60%)			(0.20%)	0.40%	[8]
Plant basis differences				(1.70%)		(3.50%)			(1.80%)	2.00%	[8]
Production tax credits and other credits				0.00%		0.00%			0.00%	0.00%
Noncontrolling interests				0.00%		0.00%			0.00%	0.00%	[8]
Statute of limitations expiration	[8]					0.00%
Merger expenses						3.10%			(15.10%)	(30.50%)	[8]
Fitzpatrick bargain purchase gain									0.00%
Like-kind exchange(c)				0.00%					0.00%
Other				0.90%		1.20%			1.00%	(0.10%)	[8]
Effective income tax rate				38.70%		40.00%			24.00%	1.60%	[8]
Atlantic City Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate				35.00%		35.00%			35.00%	35.00%	[8]
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit				5.60%		5.90%			5.60%	5.90%	[8]
Qualified nuclear decommissioning trust fund income				(0.00%)		(0.00%)			(0.00%)	(0.00%)	[8]
Amortization of investment tax credit, including deferred taxes on basis difference				(0.40%)		(1.60%)			(0.40%)	0.10%	[8]
Plant basis differences				(3.30%)		(7.10%)			(3.30%)	1.00%	[8]
Production tax credits and other credits				0.00%		0.00%			0.00%	0.00%
Noncontrolling interests				0.00%		0.00%			0.00%	0.00%	[8]
Statute of limitations expiration	[8]					0.00%
Merger expenses						0.00%			(85.30%)	(17.70%)	[8]
Fitzpatrick bargain purchase gain									0.00%
Like-kind exchange(c)				0.00%					0.00%
Other				(3.60%)		7.80%			(1.60%)	(0.10%)	[8]
Effective income tax rate				33.30%		40.00%			(50.00%)	24.20%	[8]
Pepco Holdings LLC [Member] | Successor [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate		35.00%	[8]	35.00%		35.00%			35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit		5.20%	[8]	4.30%		6.10%			4.60%
Qualified nuclear decommissioning trust fund income		(0.00%)	[8]	(0.00%)		(0.00%)			(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference		0.10%	[8]	(0.10%)		(0.30%)			(0.20%)
Plant basis differences		1.70%	[8]	(4.80%)		(7.00%)			(4.30%)
Production tax credits and other credits		0.00%		0.00%		0.00%			0.00%
Noncontrolling interests		0.00%	[8]	0.00%		0.00%			0.00%
Statute of limitations expiration		0.00%	[8]			0.00%
Merger expenses		(18.90%)	[8]			1.00%			(23.80%)
Fitzpatrick bargain purchase gain									0.00%
Like-kind exchange(c)				0.00%					0.00%
Other		(0.00%)	[8]	0.90%		1.00%			(0.00%)
Effective income tax rate		23.10%	[8]	35.30%		35.80%			11.30%
Pepco Holdings LLC [Member] | Predecessor [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate								35.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit								11.90%
Qualified nuclear decommissioning trust fund income								(0.00%)
Amortization of investment tax credit, including deferred taxes on basis difference								(0.90%)
Plant basis differences								(13.50%)
Production tax credits and other credits								0.00%
Noncontrolling interests								0.00%
Statute of limitations expiration								0.00%
Merger expenses								11.10%
Other								3.60%
Effective income tax rate								47.20%
[1]	The effective tax rate for the three months ended June 30, 2017 is disproportionately impacted due to the decline in consolidated pre-tax GAAP earnings as compared to the federal and state tax impacts of the Like-kind exchange, tax credits, Plant basis differences, and Qualified nuclear decommissioning trust fund income.
[2]	See Like-Kind Exchange within the Other Income Tax Matters section below for further details.
[3]	Generation recognized a loss before income taxes for the three months ended June 30, 2017. As a result, positive percentages represent an income tax benefit for the period presented.
[4]	The effective tax rate for the three months ended June 30, 2016, is disproportionately impacted due to the decline in pre-tax GAAP earnings as compared to the changes in tax credits and other reconciling items. In three months ended June 30, 2016, due to the expiration of a statute of limitations, Generation recorded an income tax benefit of $16 million. The statute of limitations expired in the third quarter of 2015; therefore, this represents an out of period adjustment.
[5]	At PECO, includes a cumulative adjustment related to an anticipated gas repairs tax return accounting method change.
[6]	At BGE, includes a cumulative adjustment related to a regulatory asset.
[7]	The effective tax rate for the three months ended June 30, 2016 is disproportionately impacted due to the decline in pre-tax GAAP earnings and changes in other reconciling items.
[8]	Pepco, DPL and ACE recognized a loss before income taxes for the six months ended June 30, 2016, and PHI recognized a loss before income taxes for the period of March 24, 2016, through June 30, 2016. As a result, positive percentages represent an income tax benefit for the periods presented.
[9]	Includes a remeasurement of uncertain state income tax positions for Pepco and DPL.

Income Taxes Income Tax Unrecog

Income Taxes Income Tax Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 730	$ 916
Exelon Generation Co L L C [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	467	490
Commonwealth Edison Co [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	2	(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
Potomac Electric Power Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	59	80
Delmarva Power and Light Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	21	37
Atlantic City Electric Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 0	$ 22

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	Jul. 06, 2017	Jul. 06, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2017	Mar. 31, 2016	Dec. 31, 2009
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			$ 730		$ 916		$ 730
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities							21
Subsequent Event [Member]
Income Tax Additional Narrative Information [Line Items]
Increase (Decrease) in Income Taxes		$ 70
Increase (Decrease) in Deferred Income Taxes	$ 180
Like kind exchange [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			50				50
Payments for Other Taxes							950
Unrecognized Tax Benefits, Period Increase (Decrease)							2
Deferred Gain on Sale of Property									$ 1,200
Decrease in Unrecognized Tax Benefits is Reasonably Possible			39				39
IRS asserted penalties for understatement of tax			90			$ 106
Expected non-cash charge to earnings			26				26
Early termination amount					1,250
Taxes Payable, Current			335				335	$ 360
Income Taxes Receivable			60				60
Unrecognized Tax Benefits, Income Tax Penalties Accrued			1,300				1,300
Deferred Income Tax Expense (Benefit)							350
Other [Member]
Income Tax Additional Narrative Information [Line Items]
IRS asserted penalties for understatement of tax						94
Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			467		490		467
Income Taxes Receivable			16				16
Exelon Generation Co L L C [Member] | Subsequent Event [Member]
Income Tax Additional Narrative Information [Line Items]
Increase (Decrease) in Income Taxes		$ 15
Increase (Decrease) in Deferred Income Taxes	15
Commonwealth Edison Co [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			2		(12)		2
Decrease in Unrecognized Tax Benefits is Reasonably Possible			2				2
Commonwealth Edison Co [Member] | Subsequent Event [Member]
Income Tax Additional Narrative Information [Line Items]
Increase (Decrease) in Deferred Income Taxes	$ 250
Commonwealth Edison Co [Member] | Like kind exchange [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			15				15
Payments for Other Taxes							300
Unrecognized Tax Benefits, Period Increase (Decrease)							8
IRS asserted penalties for understatement of tax						86
Expected non-cash charge to earnings			23				23
Taxes Payable, Current						150
Income Taxes Receivable			369				369
Unrecognized Tax Benefits, Income Tax Penalties Accrued			300				300
Commonwealth Edison Co [Member] | Other [Member]
Income Tax Additional Narrative Information [Line Items]
IRS asserted penalties for understatement of tax						$ 64
Income Taxes Receivable			23				23
PECO Energy Co [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			0		0		0
Baltimore Gas and Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			120		120		120
Pepco Holdings LLC [Member] | Successor [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			112		172		112
Potomac Electric Power Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			59		80		59
Delmarva Power and Light Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			21		37		21
Atlantic City Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			0		$ 22		0
Internal Revenue Service (IRS) [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities				$ 146
Internal Revenue Service (IRS) [Member] | Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities				19
Internal Revenue Service (IRS) [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities				59
Internal Revenue Service (IRS) [Member] | Potomac Electric Power Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities				21
Internal Revenue Service (IRS) [Member] | Delmarva Power and Light Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities				16
Internal Revenue Service (IRS) [Member] | Atlantic City Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities				$ 22
State and Local Jurisdiction [Member]
Income Tax Additional Narrative Information [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible			257				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				50
Decrease in Unrecognized Tax Benefits is Reasonably Possible			57				57
State and Local Jurisdiction [Member] | Baltimore Gas and Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible			120				120
State and Local Jurisdiction [Member] | Pepco Holdings LLC [Member] | Successor [Member]
Income Tax Additional Narrative Information [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible			80				80
State and Local Jurisdiction [Member] | Potomac Electric Power Company [Member]
Income Tax Additional Narrative Information [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible			59				59
State and Local Jurisdiction [Member] | Delmarva Power and Light Company [Member]
Income Tax Additional Narrative Information [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible			$ 21				$ 21

Nuclear Decommissioning - Rollf

Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]	$ 231	$ 220
Asset Retirement Obligation, Period Increase (Decrease)			0
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]	229	$ 220
Nuclear Decommissioning ARO, Ending Balance		24
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		225
Asset Retirement Obligation, Liabilities Settled		103
Asset Retirement Obligation, Period Increase (Decrease)		(3)
Asset Retirement Obligation, Revision of Estimate		417
Nuclear Decommissioning ARO, Ending Balance	[2]	9,476
Current portion of ARO		$ 12
[1]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income
[2]	Includes $12 million and $10 million for the current portion of the ARO at June 30, 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	6 Months Ended
		Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017	Dec. 31, 2016
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent		$ 0	$ 0			$ 14
Asset Retirement Obligation, Revision of Estimate				$ 0
Decommissioning Fund Investments		12,641	12,641			11,061
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent		0	0			14
Proceeds from Customers		24	24		$ 4
Decommissioning Fund Investments		12,641	12,641			11,061
Nuclear Decommissioning [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Increase (Decrease) in Asset Retirement Obligations		138
Asset Retirement Obligation, Period Increase (Decrease)			742
Asset Retirement Obligation, Revision of Estimate			(3)
Proceeds from Customers	[1]	9,476	9,476			$ 8,734
Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent		$ 114	$ 114
[1]	Includes $12 million and $10 million for the current portion of the ARO at June 30, 2017 and December 31, 2016, respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets.

Nuclear Decommissioning - Unrea

Nuclear Decommissioning - Unrealized Gains on NDT Funds (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Unrealized Losses On Nuclear Decommissioning Trust Fund Investment [Line Items]
Unrealized Gain Loss Investment Income Pledged Assets		$ (2)	$ 1	$ (2)	$ 3
Nuclear Plant [Member] | Regulated Operation [Member]
Unrealized Losses On Nuclear Decommissioning Trust Fund Investment [Line Items]
Net unrealized gains (losses) on decommissioning trust funds - regulatory agreement units	[1],[2]	52		210	131
Net unrealized gains (losses) on decommissioning trust funds - non-regulatory agreement units	[1],[2]	48		$ 235	$ 100
Unrealized Gain (Loss) on Investments	[1],[2]	(13)
Nuclear Plant [Member] | Unregulated Operation [Member]
Unrealized Losses On Nuclear Decommissioning Trust Fund Investment [Line Items]
Unrealized Gain (Loss) on Investments	[1],[2]	$ 70
[1]	Excludes $(2) million and $1 million of net unrealized gains (losses) related to the Zion Station pledged assets for the three months ended June 30, 2017 and 2016 respectively. Excludes $(2) million and $3 million of net unrealized gains (losses) related to the Zion Station pledged assets for the six months ended June 30, 2017 and 2016, respectively. Net unrealized gains (losses) related to Zion Station pledged assets are included in Other current liabilities and Payable for Zion Station decommissioning on Exelon’s and Generation’s Consolidated Balance Sheets in 2017 and 2016, respectively.
[2]	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		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Nuclear Decommissioning Additional Narrative Information [Line Items]
Pledged assets for Zion Station decommissioning		$ 75		$ 113
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Pledged assets for Zion Station decommissioning		75		113
Payable to Zion Solutions	[1]	69		104
Current portion of payable to Zion Solutions	[2]	69		$ 90
Withdrawals by Zion Solutions to pay decommissioning costs		$ 914	$ 878
[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	6 Months Ended
	Jun. 30, 2017USD ($)
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Obligation, Pension Benefits	$ 92
Increase (Decrease) in Obligation, Other Postretirement Benefits	57
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	59
Defined Benefit Plan Amounts Recognized In Regulatory Assets Before Tax	57
Defined Benefit Plan Amounts Recognized In Regulatory Liabilities Before Tax	$ 4
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%
Fitzpatrick [Member]
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Obligation, Pension Benefits	$ 38
Increase (Decrease) in Obligation, Other Postretirement Benefits	$ 11

Retirement Benefits - Calculati

Retirement Benefits - Calculation of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017	[1]	Jun. 30, 2016	[2]
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 97	$ 91		$ 191		$ 170
Interest cost	211	212		422		403
Expected return on assets	(299)	(292)		(598)		(555)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	2	0		2		0
Amortization of:
Prior service cost (benefit)	1	4		1		7
Actuarial loss	150	142		302		269
Net periodic benefit cost	162	157		320		294
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	28	28		54		54
Interest cost	46	48		91		90
Expected return on assets	(41)	(42)		(82)		(80)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	0	0		0		0
Amortization of:
Prior service cost (benefit)	(47)	(47)		(94)		(91)
Actuarial loss	15	16		31		30
Net periodic benefit cost	$ 1	$ 3		$ 0		$ 3
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
Actuarial 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)
Actuarial loss			2
Net periodic benefit cost			$ 1
[1]	(a)FitzPatrick net benefit costs are included for the period after acquisition.
[2]	(b)PHI net periodic benefit costs for the period prior to the merger are not included in the table above.

Retirement Benefits - Allocated

Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions		3 Months Ended						6 Months Ended
		Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017		Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		$ 163		$ 160				$ 320		$ 297
Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	[1]	13		10				26		24
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		59	[2]	55				113	[2]	109
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		44		42				87		83
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		7		8				14		17
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		16		18				31		33
Baltimore Gas and Electric Company [Member] | Other Pension, Postretirement and Supplemental Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)								32
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		6	[3]	7	[3]		$ 7	13	[3]	16	[3]
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		3	[3]	4	[3]		4	6	[3]	9	[3]
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		3	[3]	4	[3]		3	7	[3]	8	[3]
Pepco Holdings LLC [Member] | Successor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		24				$ 31		48
Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)				27		$ 31	23
Pepco Holdings LLC [Member] | Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		$ 12	[1],[3]	$ 12	[1],[3]		$ 9	$ 22	[1],[3]	$ 21	[1],[3]
[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]	(c)FitzPatrick net benefit costs are included for the period after acquisition.
[3]	Pepco's, DPL's, ACE's and PHISCO's pension and postretirement benefit costs for the six months ended June 30, 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		3 Months Ended						6 Months Ended
		Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017		Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		$ 33		$ 30				$ 63		$ 56
Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	3		2				5		7
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		14		13				28		25
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		8		7				15		13
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		2		2				4		4
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		3		2				4		3
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		1	[2]	1	[2]		$ 1	2	[2]	2	[2]
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		1	[2]	0	[2]		1	1	[2]	1	[2]
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[2]	0		1				1		1
Pepco Holdings LLC [Member] | Successor [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		3						7
Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions				4		$ 4	3
Pepco Holdings LLC [Member] | Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1],[2]	$ 1		$ 2			$ 1	$ 3		$ 3
[1]	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.
[2]	Pepco's, DPL's and PHISCO's matching contributions for the six months ended June 30, 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 six months ended June 30, 2016.

Severance - Ongoing Severance P

Severance - Ongoing Severance Plans (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 5	$ 2	$ 9	$ 4
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1	1	4	3
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1	1	1	2
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1	1	2	1
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1	1	1	1
Pepco Holdings LLC [Member] | Successor [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		3	0	3	0
Potomac Electric Power Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1	0	1	0
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1		1
Delmarva Power and Light Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1	0	1	0
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1		1
Atlantic City Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1	$ 0	1	$ 0
Atlantic City Electric Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 1		$ 1
[1]	The amounts above for Generation include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and $1 million and $2 million for the three and six months ended June 30, 2016, respectively. The amounts above for ComEd include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and less than $1 million and $1 million for the three and six months ended June 30, 2016, respectively. Amounts billed by PHISCO to Pepco, DPL and ACE were $1 million, each, for both three and six months ended June 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and six months ended June 30, 2016.

Severance Severance - Cost Mana

Severance Severance - Cost Management Program-Related (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017		Jun. 30, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 5	$ 2	$ 9		$ 4
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]	1	1	4		3
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	1	1		2
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	1	2		1
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]
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 1	$ 1	1		1
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]	Amounts billed by BSC through intercompany allocations for the six months ended June 30, 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 six months ended June 30, 2016.
[3]	The amounts above for Generation include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and $1 million and $2 million for the three and six months ended June 30, 2016, respectively. The amounts above for ComEd include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and less than $1 million and $1 million for the three and six months ended June 30, 2016, respectively. Amounts billed by PHISCO to Pepco, DPL and ACE were $1 million, each, for both three and six months ended June 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and six months ended June 30, 2016.

Severance - PHI Merger (Details

Severance - PHI Merger (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 5	$ 2	$ 9	$ 4
PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		2		55
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1	1	4	3
Exelon Generation Co L L C [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		(1)		9
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1	1	1	2
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			(1)		8
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1	1	2	1
Commonwealth Edison Co [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		(1)		2
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1	1	1	1
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			(1)		2
PECO Energy Co [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		0		1
PECO Energy Co [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1		1
Baltimore Gas and Electric Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		0		1
Baltimore Gas and Electric Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1		1
Pepco Holdings LLC [Member] | Successor [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		3	0	3	0
Pepco Holdings LLC [Member] | Successor [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		4		42
Potomac Electric Power Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1	0	1	0
Potomac Electric Power Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		2		20
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1		1
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			2		19
Delmarva Power and Light Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1	0	1	0
Delmarva Power and Light Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		1		12
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1		1
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1		11
Atlantic City Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1	0	1	0
Atlantic City Electric Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]		1		10
Atlantic City Electric Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 1		$ 1
Atlantic City Electric Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			$ 1		$ 10
[1]	The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $(1) million, $(1) million, less than $1 million, less than $1 million, $2 million, $1 million and $1 million, respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the three months ended June 30, 2016, and $8 million, $2 million, $1 million, $1 million, $19 million, $11 million and $10 million for the six months ended June 30, 2016.
[2]	The amounts above for Generation include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and $1 million and $2 million for the three and six months ended June 30, 2016, respectively. The amounts above for ComEd include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and less than $1 million and $1 million for the three and six months ended June 30, 2016, respectively. Amounts billed by PHISCO to Pepco, DPL and ACE were $1 million, each, for both three and six months ended June 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and six months ended June 30, 2016.

Severance - Severance Liabiliti

Severance - Severance Liabilities (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Restructuring Reserve [Roll Forward]
Severance Costs		$ 5	$ 2	$ 9	$ 4
Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance				88
Severance Costs	[1]			25
Payments for Restructuring				(18)
Ending Balance		95		95
Exelon Generation Co L L C [Member]
Restructuring Reserve [Roll Forward]
Severance Costs	[2]	1	1	4	3
Exelon Generation Co L L C [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance				36
Severance Costs	[1]			17
Payments for Restructuring				(4)
Ending Balance		49		49
Commonwealth Edison Co [Member]
Restructuring Reserve [Roll Forward]
Severance Costs	[2]	1	1	2	1
Commonwealth Edison Co [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance				3
Severance Costs	[1]			1
Payments for Restructuring				(1)
Ending Balance		3		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		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		0
Pepco Holdings LLC [Member] | Successor [Member]
Restructuring Reserve [Roll Forward]
Severance Costs		3	0	3	0
Pepco Holdings LLC [Member] | Successor [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance				29
Severance Costs	[1]			3
Payments for Restructuring				(10)
Ending Balance		22		22
Potomac Electric Power Company [Member]
Restructuring Reserve [Roll Forward]
Severance Costs	[2]	1	0	1	0
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		0
Delmarva Power and Light Company [Member]
Restructuring Reserve [Roll Forward]
Severance Costs	[2]	1	0	1	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		0
Atlantic City Electric Company [Member]
Restructuring Reserve [Roll Forward]
Severance Costs	[2]	1	$ 0	1	$ 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		$ 0
[1]	(a)Includes salary continuance and health and welfare severance benefits.
[2]	The amounts above for Generation include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and $1 million and $2 million for the three and six months ended June 30, 2016, respectively. The amounts above for ComEd include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and less than $1 million and $1 million for the three and six months ended June 30, 2016, respectively. Amounts billed by PHISCO to Pepco, DPL and ACE were $1 million, each, for both three and six months ended June 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and six months ended June 30, 2016.

Severance Severance - Narrative

Severance Severance - Narrative (Details) $ in Millions		1 Months Ended		3 Months Ended		6 Months Ended
		Jun. 30, 2017USD ($)	Aug. 31, 2015	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)		Jun. 30, 2016USD ($)		Dec. 31, 2016USD ($)
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 5	$ 2	$ 9		$ 4
Regulatory Assets		$ 11,238		11,238		11,238				$ 11,388
Merger Integration Costs [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		32		32		32				25
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated			500
Severance Costs						(1)	[1]	17	[2]
Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		(17)
Corporate, Non-Segment [Member] | Cost Management Project [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]
Severance Costs	[3]			1	1	4		3
Exelon Generation Co L L C [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated			250
Severance Costs						(1)	[1]	12	[2]
Exelon Generation Co L L C [Member] | Facility Closing [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		(17)
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				1	1	1		2
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs								7
Potomac Electric Power Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[3]			1	0	1		0
Regulatory Assets		847		847		847				852
Potomac Electric Power Company [Member] | Merger Integration Costs [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		12		12	9	12		9		11	[4]
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				1		1
Delmarva Power and Light Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[3]			1	0	1		0
Regulatory Assets		370		370		370				$ 348
Delmarva Power and Light Company [Member] | Merger Integration Costs [Member]
Restructuring Cost and Reserve [Line Items]
Regulatory Assets		$ 13		13	$ 3	13		$ 3
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 1		$ 1
[1]	Amounts billed by BSC through intercompany allocations for the six months ended June 30, 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 six months ended June 30, 2016.
[3]	The amounts above for Generation include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and $1 million and $2 million for the three and six months ended June 30, 2016, respectively. The amounts above for ComEd include less than $1 million and $1 million for amounts billed by BSC through intercompany allocations for the three and six months ended June 30, 2017, respectively, and less than $1 million and $1 million for the three and six months ended June 30, 2016, respectively. Amounts billed by PHISCO to Pepco, DPL and ACE were $1 million, each, for both three and six months ended June 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and six months ended June 30, 2016.
[4]	As of June 30, 2017 and December 31, 2016, Pepco’s regulatory asset of $12 million and $11 million, respectively, represents previously incurred PHI acquisition costs authorized for recovery by the November 2016 Maryland distribution rate case order. As of June 30, 2017, DPL’s regulatory asset of $13 million represents previously incurred PHI acquisition costs, including $4 million authorized for recovery by the February 2017 Maryland distribution rate case order, $6 million authorized for recovery by the May 2017 Delaware electric distribution rate case order, and $3 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.

Mezzanine Equity Mezzanine Equi

Mezzanine Equity Mezzanine Equity (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Preferred Stock, Shares Subscribed but Unissued, Value [Abstract]
Payments to Acquire Businesses, Gross	$ 212	$ 6,642
Exelon Generation Co L L C [Member]
Redeemable Noncontrolling Interest [Line Items]
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	1
Preferred Stock, Shares Subscribed but Unissued, Value [Abstract]
Payments to Acquire Businesses, Gross	$ 212	$ 1

Changes in Accumulated Other100

Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions		3 Months Ended						6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2016		Mar. 23, 2016		Jun. 30, 2017		Jun. 30, 2016
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance								$ 27,612
Amounts reclassified from AOCI(b)	[1]	$ 34	$ 34					74		$ 72
Other comprehensive income		35	31					25		59
Ending balance		29,290						29,290
Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI(b)	[1]	0	0					4		3
Other comprehensive income		1	0					12		(2)
PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI(b)	[1]					$ 1
Gains and (losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance						(19)	[2]	(17)		(19)	[2]
OCI before reclassifications								1		(10)	[2]
Amounts reclassified from AOCI(b)								4		3	[2],[3]
Other comprehensive income	[2]							5		(7)
Ending balance	[2]	(12)	(26)	$ (26)				(12)		(26)
Gains and (losses) on Cash Flow Hedges | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance						(21)	[2]	(19)		(21)	[2]
OCI before reclassifications								1		(7)	[2]
Amounts reclassified from AOCI(b)								4		3	[2],[3]
Other comprehensive income	[2]							5		(4)
Ending balance	[2]	(14)	(25)	(25)				(14)		(25)
Gains and (losses) on Cash Flow Hedges | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					0		0		0
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	0	0	0				0		0
Gains and (losses) on Cash Flow Hedges | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			(8)	[4]	(8)				(8)
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[2],[3]					0
Other comprehensive income	[2]					0
Ending balance	[2],[4]					(8)
Unrealized Gains and (losses) on Marketable Securities
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					3		4		3
OCI before reclassifications	[2]							2		0
Amounts reclassified from AOCI(b)	[2]							0		0	[3]
Other comprehensive income	[2]							2		0
Ending balance	[2]	6	3	3				6		3
Unrealized Gains and (losses) on Marketable Securities | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					1		2		1
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	2	1	1				2		1
Unrealized Gains and (losses) on Marketable Securities | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					1		1		1
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	1	1	1				1		1
Unrealized Gains and (losses) on Marketable Securities | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			0	[4]	0				0
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[2],[3]					0
Other comprehensive income	[2]					0
Ending balance	[2],[4]					0
Pension and Non-Pension Postretirement Benefit Plan Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(2,565)		(2,610)		(2,565)
OCI before reclassifications	[2]							(58)		(2)
Amounts reclassified from AOCI(b)	[1]	34	34					70	[2],[3]	69	[2],[3]
Other comprehensive income	[2]							12		67
Ending balance	[2]	(2,598)	(2,498)	(2,498)				(2,598)		(2,498)
Pension and Non-Pension Postretirement Benefit Plan Items | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					0		0		0
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[1]	0	0					0	[2],[3]	0	[2],[3]
Other comprehensive income	[2]							0		0
Ending balance	[2]	0	0	0				0		0
Pension and Non-Pension Postretirement Benefit Plan Items | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					0		0		0
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	0	0	0				0		0
Pension and Non-Pension Postretirement Benefit Plan Items | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			(27)	[4]	(28)				(28)
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[1],[2],[3]					1
Other comprehensive income	[2]					1
Ending balance	[2],[4]					(27)
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(40)		(30)		(40)
OCI before reclassifications	[2]							3		6
Amounts reclassified from AOCI(b)	[2]							0		0	[3]
Other comprehensive income	[2]							3		6
Ending balance	[2]	(27)	(34)	(34)				(27)		(34)
Foreign Currency Items | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(40)		(30)		(40)
OCI before reclassifications	[2]							3		6
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							3		6
Ending balance	[2]	(27)	(34)	(34)				(27)		(34)
Foreign Currency Items | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					0		0		0
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	0	0	0				0		0
Foreign Currency Items | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			0	[4]	0				0
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[2],[3]					0
Other comprehensive income	[2]					0
Ending balance	[2],[4]					0
AOCI of Equity Investments
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(3)		(7)		(3)
OCI before reclassifications	[2]							5		(7)
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							5		(7)
Ending balance	[2]	(2)	(10)	(10)				(2)		(10)
AOCI of Equity Investments | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(3)		(7)		(3)
OCI before reclassifications	[2]							6		(4)
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							6		(4)
Ending balance	[2]	(1)	(7)	(7)				(1)		(7)
AOCI of Equity Investments | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					0		0		0
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	0	0	0				0		0
AOCI of Equity Investments | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			0	[4]	0				0
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[2],[3]					0
Other comprehensive income	[2]					0
Ending balance	[2],[4]					0
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(2,624)		(2,660)		(2,624)
OCI before reclassifications	[2]							(47)		(13)
Amounts reclassified from AOCI(b)	[2]							74		72	[3]
Other comprehensive income	[2]							27		59
Ending balance	[2]	(2,633)	(2,565)	(2,565)				(2,633)		(2,565)
Total | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					(63)		(54)		(63)
OCI before reclassifications	[2]							10		(5)
Amounts reclassified from AOCI(b)	[2],[3]							4		3
Other comprehensive income	[2]							14		(2)
Ending balance	[2]	(40)	(65)	(65)				(40)		(65)
Total | PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]					1		1		1
OCI before reclassifications	[2]							0		0
Amounts reclassified from AOCI(b)	[2],[3]							0		0
Other comprehensive income	[2]							0		0
Ending balance	[2]	$ 1	$ 1	1				$ 1		1
Total | PEPCO Holdings Inc [Member] | Predecessor [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			$ (35)	[4]	(36)				$ (36)
OCI before reclassifications	[2]					0
Amounts reclassified from AOCI(b)	[2],[3]					1
Other comprehensive income	[2]					1
Ending balance	[2],[4]					$ (35)
[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]	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.

Changes in Accumulated Other101

Changes in Accumulated Other Comprehensive Income - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017		Jun. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income Tax Expense (Benefit)		$ (72)	$ 102		$ 143		$ 285
Net of tax / Total Reclassification for the period	[1]	(34)	(34)		(74)		(72)
Gains and (losses) on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax / Total Reclassification for the period					(4)		(3)	[2],[3]
Gains and (losses) on Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		0
Income Tax Expense (Benefit)		0
Net of tax		0
Prior service costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and other postretirement benefit plan items	[1],[4]	23	19		46		38
Actuarial losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and other postretirement benefit plan items	[1],[4]	(81)	(75)		(162)		(151)
Pension and Non-Pension Postretirement Benefit Plan Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and other postretirement benefit plan items	[1]	(58)	(56)		(116)		(113)
Tax benefit	[1]	(24)	(22)		(46)		(44)
Net of tax / Total Reclassification for the period	[1]	(34)	(34)		(70)	[2],[3]	(69)	[2],[3]
Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income Tax Expense (Benefit)	[1]				(3)		(2)
Cash Flow Hedging [Member] | Gains and (losses) on Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other cash flow hedges		0			(7)	[1]	(5)	[1]
Total before tax	[1]				(7)		(5)
Income Tax Expense (Benefit)	[1]				3		2
Net of tax	[1]				(4)		(3)
Exelon Generation Co L L C [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income Tax Expense (Benefit)		(158)	(31)		(31)		120
Net of tax / Total Reclassification for the period	[1]	0	0		(4)		(3)
Exelon Generation Co L L C [Member] | Gains and (losses) on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax / Total Reclassification for the period					(4)		(3)	[2],[3]
Exelon Generation Co L L C [Member] | Gains and (losses) on Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax		0
Income Tax Expense (Benefit)		0
Net of tax		0
Exelon Generation Co L L C [Member] | Prior service costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and other postretirement benefit plan items	[1],[4]	0	0		0		0
Exelon Generation Co L L C [Member] | Actuarial losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and other postretirement benefit plan items	[1],[4]	0	0		0		0
Exelon Generation Co L L C [Member] | Pension and Non-Pension Postretirement Benefit Plan Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and other postretirement benefit plan items	[1]	0	0		0		0
Tax benefit	[1]	0	0		0		0
Net of tax / Total Reclassification for the period	[1]	0	$ 0		0	[2],[3]	0	[2],[3]
Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member] | Gains and (losses) on Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other cash flow hedges		$ 0			(7)	[1]	(5)	[1]
Total before tax	[1]				(7)		(5)
Income Tax Expense (Benefit)	[1]				3		2
Net of tax	[1]				$ (4)		$ (3)
PEPCO Holdings Inc [Member] | Predecessor [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax / Total Reclassification for the period	[1]			$ (1)
PEPCO Holdings Inc [Member] | Gains and (losses) on Cash Flow Hedges | Predecessor [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net of tax / Total Reclassification for the period	[2],[3]			0
PEPCO Holdings Inc [Member] | Prior service costs | Predecessor [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and other postretirement benefit plan items	[1],[4]			0
PEPCO Holdings Inc [Member] | Actuarial losses | Predecessor [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and other postretirement benefit plan items	[1],[4]			(1)
PEPCO Holdings Inc [Member] | Pension and Non-Pension Postretirement Benefit Plan Items | Predecessor [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and other postretirement benefit plan items	[1]			(1)
Tax benefit	[1]			0
Net of tax / Total Reclassification for the period	[1],[2],[3]			(1)
PEPCO Holdings Inc [Member] | Cash Flow Hedging [Member] | Gains and (losses) on Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member] | Predecessor [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other cash flow hedges	[1]			0
Total before tax	[1]			0
Income Tax Expense (Benefit)	[1]			0
Net of tax	[1]			$ 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 Other102

Changes in Accumulated Other Comprehensive Income - Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ (24)	$ (21)		$ (50)	$ (37)
Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(2)	2		(5)	6
Prior service costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	9	7		18	15
Actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(32)	(30)		(64)	(60)
Actuarial losses | PEPCO Holdings Inc [Member] | Predecessor [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax			$ 0
Pension and Non-Pension Postretirement Benefit Plan Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	1	0		3	1
Gains and (losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(2)	2		(3)	4
Gains and (losses) on Cash Flow Hedges | Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(2)	1		(3)	3
Unrealized Gains and (losses) on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	0	(1)		(1)	0
Change in unrealized (loss)/gain on equity investments	0	1		(3)	3
Unrealized Gains and (losses) on Marketable Securities | Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in unrealized (loss)/gain on equity investments	$ 0	$ 1		$ (2)	$ 3

Common Stock - Narrative (Detai

Common Stock - Narrative (Details) $ in Millions	Jun. 30, 2017USD ($)
Equity, Class of Treasury Stock [Line Items]
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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 80	$ 267	$ 1,076	$ 440
Weighted average common shares outstanding — basic	934	924	931	923
Assumed exercise and/or distributions of stock-based awards	2	2	1	3
Weighted average common shares outstanding — diluted	936	926	932	926

Earnings Per Share and Equit105

Earnings Per Share and Equity - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 01, 2017	Mar. 31, 2017	Dec. 31, 2016
Statement Of Equity Line Item [Line Items]
Treasury Stock, Value	$ (123)	$ (123)		$ (123)		$ (2,300)	$ 123	$ (2,327)
Treasury Stock, Shares	1,832,457	1,832,457		1,832,457				34,743,157
Equity units issued [Member]
Statement Of Equity Line Item [Line Items]
Stock options not included in the calculation of diluted common shares outstanding			1,000,000		2,000,000
Stock Issued During Period, Shares, Treasury Stock Reissued	33,000,000
Treasury Stock, Shares						35,000,000
Employee Stock Option [Member]
Statement Of Equity Line Item [Line Items]
Stock options not included in the calculation of diluted common shares outstanding		8,000,000	11,000,000	9,000,000	12,000,000

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Equity Investment Commitments (Details) $ in Millions	Jun. 30, 2017USD ($)
Guarantor Obligations [Line Items]
Other Commitment	$ 3,086
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	2,257
Equity Unit Purchase Agreements [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment, Due in Next Twelve Months	8
Other Commitment, Due in Second Year	7
Other Commitment, Due in Third Year	3
Other Commitment	$ 18

Commitments and Contingencie107

Commitments and Contingencies - Commitments Narrative (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2017USD ($)	Jun. 30, 2017USD ($)MW		Jun. 30, 2016USD ($)	Dec. 31, 2016USD ($)	Nov. 29, 2016employee	Jun. 30, 2014USD ($)
Guarantor Obligations [Line Items]
Commitments and Contingencies							$ 1,000
Power Volume | MW		220
Noncash Merger Related Costs		$ 0	[1],[2]	$ 503
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Costs Incurred, Development Costs	457
Consent Decree Penalty		1.6
Commitments and Contingencies
Entity Number of Employees | employee						1,500
Leasehold Improvements, Gross					110
Noncash Merger Related Costs		0	[2]	3
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Commitments and Contingencies
Noncash Merger Related Costs				0
PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Commitments and Contingencies
Noncash Merger Related Costs				0
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Noncash Merger Related Costs				$ 0
Nuclear Plant [Member] | Minimum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Commitments and Contingencies	450	450
Nuclear Plant [Member] | Maximum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Commitments and Contingencies	$ 500	$ 500
[1]	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.
[2]	See Note 4 — Mergers, Acquisitions and Dispositions for additional information related to the merger with PHI.

Commitments and Contingencie108

Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Jun. 30, 2017USD ($)
Guarantor Obligations [Line Items]
Other Commitment	$ 3,086
Guarantor Obligations, Maximum Exposure, Undiscounted	48
Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,326
Guarantee of Indebtedness of Others [Member]
Guarantor Obligations [Line Items]
Other Commitment	628
Surety Bond [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,113
Guarantee Obligations [Member]
Guarantor Obligations [Line Items]
Other Commitment	19
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	2,257
Exelon Generation Co L L C [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	1,243
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	1,014
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	226
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	12
PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Other Commitment	219
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	18
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	263
Baltimore Gas and Electric Company [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Other Commitment	2
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	41
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	21
PEPCO Holdings Inc [Member] | Guarantee Obligations [Member]
Guarantor Obligations [Line Items]
Other Commitment	19
Potomac Electric Power Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	20
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	13
Potomac Electric Power Company [Member] | Guarantee Obligations [Member]
Guarantor Obligations [Line Items]
Other Commitment	6
Atlantic City Electric Company [Member]
Guarantor Obligations [Line Items]
Other Commitment	9
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	4
Atlantic City Electric Company [Member] | Guarantee Obligations [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	18
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] | Guarantee Obligations [Member]
Guarantor Obligations [Line Items]
Other Commitment	$ 7

Commitments and Contingencie109

Commitments and Contingencies - Contingencies Narrative (Details)	1 Months Ended		3 Months Ended		6 Months Ended
	Nov. 30, 2015USD ($)	Sep. 23, 2015USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)	Jun. 30, 2017USD ($)MW
Commitments And Contingencies Additional Narrative Information [Line Items]
BusinessAcquisitionResidualcommitment | MW					55
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 48,000,000		$ 48,000,000
Loss Contingency, Loss in Period					0
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Estimated Insurance Recoveries			3,200,000,000		3,200,000,000
Accrued Insurance, Current			13,400,000,000		13,400,000,000
Prepaid Reinsurance Premiums			360		360
Loss Contingency, Undiscounted Amount of Insurance-related Assessment Liability			450,000,000
Maximum liability per nuclear incident			13,000,000,000		13,000,000,000
Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			14,000,000		14,000,000
Baltimore Gas and Electric Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Occupancy, Net	$ 42,000,000	$ 12,000,000
Operating Leases, Income Statement, Initial Direct Costs				$ 25,000,000
Oil and Gas Property, Lease Operating Expense				29,000,000
Operating Expenses				$ 28,000,000
Nuclear Insurance Premiums [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Nuclear financial protection pool value			2,800,000,000		2,800,000,000
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		$ 0

Commitments and Contingencie110

Commitments and Contingencies - Environmental Issues Narrative (Details) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended
	Aug. 31, 2015gal	Jun. 30, 2017USD ($)MGPSitegal	Jun. 30, 2017USD ($)MGPSiteOpen_claimgal
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total number of MGP sites | MGPSite		19	19
Mgp Site Contingency Monitoring Count | MGPSite		23	23
Approved clean-up | MGPSite		42	42
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total number of MGP sites | MGPSite		17	17
Mgp Site Contingency Monitoring Count | MGPSite		9	9
Approved clean-up | MGPSite		26	26
Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Approved clean-up | MGPSite		13	13
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Component Amount		$ 90	$ 90
Payments for Legal Settlements			1.6
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	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	7
PEPCO Holdings Inc [Member] | Maximum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		$ 18	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	2
Calpine Corporation [Member] | Maximum [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		$ 10	$ 10
Rossville Ash Site [Member] | Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss		2	2
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	$ 1.7

Commitments and Contingencie111

Commitments and Contingencies - Litigation and Regulatory Matters (Details) $ in Millions	3 Months Ended	12 Months Ended
	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)Open_claim
Asbestos Loss Contingency [Abstract]
Open asbestos liability claims | Open_claim		224
Exelon Generation Co L L C [Member]
Asbestos Loss Contingency [Abstract]
Liability for Asbestos and Environmental Claims, Gross	$ 81	$ 83
Liability for Asbestos and Environmental Claims, Net, Payment for Claims	59
Liability for Asbestos and Environmental Claims, Net	$ 21
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency, Damages Sought, Value		$ 14

Commitments and Contingencie112

Commitments and Contingencies - Schedule of Accruals for Environmental Matters (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	$ 315	$ 325
Accrual for Environmental Loss Contingencies, Gross	412	429
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	0
Accrual for Environmental Loss Contingencies, Gross	67	72
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	282	291
Accrual for Environmental Loss Contingencies, Gross	284	292
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	31	31
Accrual for Environmental Loss Contingencies, Gross	32	33
Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	2	2
Accrual for Environmental Loss Contingencies, Gross	3	2
PEPCO Holdings Inc [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	1
Accrual for Environmental Loss Contingencies, Gross	26	30
Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	0
Accrual for Environmental Loss Contingencies, Gross	23	27
Delmarva Power and Light Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	1
Accrual for Environmental Loss Contingencies, Gross	2	2
Atlantic City Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	0
Accrual for Environmental Loss Contingencies, Gross	$ 1	$ 1

Supplemental Financial Infor113

Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended					6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016		Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017		Jun. 30, 2016
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	$ 211	$ 90	[1]			$ 280		$ 122	[1]
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	74	39	[1]			106		61	[1]
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units	(13)	52				210		131
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement	70	48				235		100
Net unrealized income (losses) on pledged assets	(2)	1				(2)		3
Regulatory offset to decommissioning trust fund-related activities	(160)	(117)	[2]			(396)		(211)	[2]
Total decommissioning-related activities	180	113				433		206
Investment income	2	6				4		12
Long-term lease income								4
Unrecognized Tax Benefits Interest Income	(1)	(4)						(5)
Income Tax Examination, Penalties and Interest Expense	1					2
AFUDC - equity	17	15				33		24
Gains (Losses) on Extinguishment of Debt								(3)
Other Income	6	6				16		10
Other, net	205	144				488		258
Exelon Generation Co L L C [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	211	90	[1]			280	[1]	122	[1]
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	74	39	[1]			106	[1]	61	[1]
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units	(13)	52				210		131
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement	70	48				235		100
Net unrealized income (losses) on pledged assets	(2)	1				(2)		3
Regulatory offset to decommissioning trust fund-related activities	(160)	(117)	[2]			(396)	[2]	(211)	[2]
Total decommissioning-related activities	180	113				433		206
Investment income	1	5				3		5
Unrecognized Tax Benefits Interest Income	0	0						0
Gains (Losses) on Extinguishment of Debt								(2)
Other Income	0	(1)				4		1
Other, net	181	117				440		210
Commonwealth Edison Co [Member]
Decommissioning-Related Activities [Abstract]
Investment income								0
Unrecognized Tax Benefits Interest Income								0
Income Tax Examination, Penalties and Interest Expense	0					0
AFUDC - equity	2	1				4		3
Other Income	2	2				4		4
Other, net	4	3				8		7
PECO Energy Co [Member]
Decommissioning-Related Activities [Abstract]
Investment income						(1)		(1)
Unrecognized Tax Benefits Interest Income								0
AFUDC - equity	2	2				4		4
Other Income	0	0				0		1
Other, net	2	2				3		4
Baltimore Gas and Electric Company [Member]
Decommissioning-Related Activities [Abstract]
Investment income								2
Unrecognized Tax Benefits Interest Income								0
AFUDC - equity	4	5				8		9
Other Income	0	0				0		0
Other, net	4	5				8		11
Pepco Holdings LLC [Member] | Successor [Member]
Decommissioning-Related Activities [Abstract]
Investment income						1
Unrecognized Tax Benefits Interest Income				$ 0
AFUDC - equity	9	7		8		17
Other Income	4	4		4		8
Other, net	13	11		$ 12		26
Pepco Holdings LLC [Member] | Predecessor [Member]
Decommissioning-Related Activities [Abstract]
Unrecognized Tax Benefits Interest Income					$ 0
AFUDC - equity					7
Other Income					(11)
Other, net					$ (4)
Potomac Electric Power Company [Member]
Decommissioning-Related Activities [Abstract]
Investment income						1
Unrecognized Tax Benefits Interest Income								(1)
AFUDC - equity	5	5				11		9
Other Income	2	1				3		4
Other, net	7	6				15		14
Delmarva Power and Light Company [Member]
Decommissioning-Related Activities [Abstract]
Unrecognized Tax Benefits Interest Income								0
AFUDC - equity	2	1				3		2
Other Income	1	2				3		4
Other, net	3	3				6		6
Atlantic City Electric Company [Member]
Decommissioning-Related Activities [Abstract]
Unrecognized Tax Benefits Interest Income								(1)
AFUDC - equity	2	1				3		3
Other Income	0	1				1		1
Other, net	$ 2	$ 2				$ 4		$ 5
[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.

Supplemental Financial Infor114

Supplemental Financial Information Supplemental Financial Information - Utility Taxes (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2017	Jun. 30, 2016
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	$ 213	$ 217			$ 438	$ 369
Exelon Generation Co L L C [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	30	27			63	55
Commonwealth Edison Co [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	57	60			116	119
PECO Energy Co [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	29	32			60	66
Baltimore Gas and Electric Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	21	21			47	45
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	76	77	$ 84		152
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes				$ 77
Potomac Electric Power Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	72	73			143	152
Delmarva Power and Light Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	4	4			9	9
Atlantic City Electric Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	$ 0	$ 0			$ 0	$ 0

Supplemental Financial Infor115

Supplemental Financial Information - Cash Flow (Details) - USD ($) $ in Millions		3 Months Ended							6 Months Ended
		Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2016		Mar. 23, 2016	Jun. 30, 2017		Jun. 30, 2016
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								$ 1,545		$ 1,432
Regulatory assets	[1]								238		166
Amortization of intangible assets, net	[1]								28		28
Amortization of Power Contracts Emission Credits	[2]								20		(7)
Amortization of Nuclear Fuel Lease	[3]								529		557
Asset Retirement Obligation, Accretion Expense	[4]								231		220
Total depreciation, amortization and accretion									2,591		2,396
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		$ 163		$ 160					320		297
Gain (loss) on equity method investments									19		10
Provision for uncollectible accounts									52		51
Stock-based compensation costs									57		67
Other Decommissioning Related Activity	[5]								(144)		(123)
Energy-related options	[6]								11		(17)
Amortization of regulatory asset related to debt costs									4		4
Amortization of rate stabilization deferral									(8)		34
Amortization of debt fair value adjustment									9		(6)
Discrete impacts from EIMA	[7]								(51)		(21)
Amortization of debt costs									49		14
Inventory Write-down									51		68
Merger related commitments									0	[8],[9]	503
Restructuring Costs									25		122
Asset Retirement Obligation, Revision of Estimate											0
InventoryLCMReservePeriodCharge											36
Other									39		17
Total other noncash operating activities									415		1,056
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									(105)		(364)
Non cash Fair Value Adjustment for CENG											0
Payments to Acquire Businesses, Gross									212		6,642
Capitalized Costs, Asset Retirement Costs		103		471		$ 471			103		471
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									13		60
Stock Issued									3		2
Exelon Generation Co L L C [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								612		674
Amortization of intangible assets, net	[1]								25		23
Amortization of Power Contracts Emission Credits	[2]								20		(7)
Amortization of Nuclear Fuel Lease	[3]								529		557
Asset Retirement Obligation, Accretion Expense	[4]								229		220
Total depreciation, amortization and accretion									1,415		1,467
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		59	[10]	55					113	[10]	109
Gain (loss) on equity method investments									19		11
Provision for uncollectible accounts									19		13
Stock-based compensation costs									0		0
Other Decommissioning Related Activity	[5]								(144)		(123)
Energy-related options	[6]								11		(17)
Amortization of regulatory asset related to debt costs									0		0
Amortization of rate stabilization deferral									0		0
Amortization of debt fair value adjustment									6		6
Discrete impacts from EIMA									0		0
Amortization of debt costs									30		10
Inventory Write-down									49		66
Merger related commitments									0	[9]	3
Restructuring Costs									17		50
InventoryLCMReservePeriodCharge											36
Other									13		17
Total other noncash operating activities									121		169
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									48		(317)
Non cash Fair Value Adjustment for CENG											119
Payments to Acquire Businesses, Gross									212		1
Capitalized Costs, Asset Retirement Costs				471		471					471
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									13		60
Commonwealth Edison Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								384		345
Regulatory assets	[1]								35		34
Amortization of intangible assets, net	[1]								0
Amortization of Power Contracts Emission Credits	[2]								0
Amortization of Nuclear Fuel Lease	[3]								0
Asset Retirement Obligation, Accretion Expense	[4]								0
Total depreciation, amortization and accretion									419		379
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		44		42					87		83
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									15		18
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									2		2
Amortization of rate stabilization deferral									0		0
Amortization of debt fair value adjustment									0		0
Discrete impacts from EIMA	[7]								(51)		(21)
Amortization of debt costs									2		2
Inventory Write-down									1		2
Merger related commitments											0
InventoryLCMReservePeriodCharge											0
Other									2		(3)
Total other noncash operating activities									58		83
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									(82)		(21)
Non cash Fair Value Adjustment for CENG											0
Capitalized Costs, Asset Retirement Costs		0		0		0			0		0
Contribution of Property	[11]								23		5
PECO Energy Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								129		121
Regulatory assets	[1]								12		13
Amortization of intangible assets, net	[1]								0
Amortization of Power Contracts Emission Credits	[2]								0
Amortization of Nuclear Fuel Lease	[3]								0
Asset Retirement Obligation, Accretion Expense	[4]								0
Total depreciation, amortization and accretion									141		134
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		7		8					14		17
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									9		10
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		0
Amortization of debt fair value adjustment									0		0
Discrete impacts from EIMA									0		0
Amortization of debt costs									1		1
Inventory Write-down									0		0
Merger related commitments											0
InventoryLCMReservePeriodCharge											0
Other									(2)		(2)
Total other noncash operating activities									22		27
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									(44)		(12)
Non cash Fair Value Adjustment for CENG											0
Capitalized Costs, Asset Retirement Costs		0		0		0			0		0
Baltimore Gas and Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								155		150
Regulatory assets	[1]								84		56
Amortization of intangible assets, net	[1]								0
Amortization of Power Contracts Emission Credits	[2]								0
Amortization of Nuclear Fuel Lease	[3]								0
Asset Retirement Obligation, Accretion Expense									0
Total depreciation, amortization and accretion									239		206
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		16		18					31		33
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									3		3
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		34
Amortization of debt fair value adjustment									0		0
Discrete impacts from EIMA									0		0
Amortization of debt costs									1		2
Inventory Write-down									0		0
Merger related commitments											0
InventoryLCMReservePeriodCharge											0
Other									(7)		(12)
Total other noncash operating activities									35		60
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									6		2
Non cash Fair Value Adjustment for CENG											0
Capitalized Costs, Asset Retirement Costs		0		0		0			0		0
Potomac Electric Power Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								101		85
Regulatory assets	[1]								59		59
Amortization of intangible assets, net	[1]								0		0
Amortization of Power Contracts Emission Credits	[2]								0		0
Amortization of Nuclear Fuel Lease	[3]								0		0
Asset Retirement Obligation, Accretion Expense	[4]								0		0
Total depreciation, amortization and accretion									160		144
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		6	[12]	7	[12]			$ 7	13	[12]	16	[12]
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									4		8
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									(10)		(2)
Amortization of debt fair value adjustment									0		0
Discrete impacts from EIMA									0		0
Amortization of debt costs									0		0
Inventory Write-down									0		1
Merger related commitments									(6)	[9]	138
Other									(2)		(4)
Total other noncash operating activities									0		158
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									0		11
Non cash Fair Value Adjustment for CENG											0
Payments to Acquire Businesses, Gross											33
Capitalized Costs, Asset Retirement Costs				0		0					0
Delmarva Power and Light Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								61		55
Regulatory assets	[1]								18		21
Amortization of intangible assets, net	[1]								0		0
Amortization of Power Contracts Emission Credits	[2]								0		0
Amortization of Nuclear Fuel Lease	[3]								0		0
Asset Retirement Obligation, Accretion Expense	[4]								0		0
Total depreciation, amortization and accretion									79		76
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		3	[12]	4	[12]			4	6	[12]	9	[12]
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									0		8
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		0
Amortization of rate stabilization deferral									(5)		2
Amortization of debt fair value adjustment									0		0
Discrete impacts from EIMA									0		0
Amortization of debt costs									0		0
Inventory Write-down									0		1
Merger related commitments									(2)	[9]	100
Asset Retirement Obligation, Revision of Estimate											4
Other									(3)		(3)
Total other noncash operating activities									(3)		121
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									15		(9)
Non cash Fair Value Adjustment for CENG											0
Capitalized Costs, Asset Retirement Costs				0		0					0
Atlantic City Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								44		40
Regulatory assets	[1]								28		41
Amortization of intangible assets, net	[1]								0		0
Amortization of Power Contracts Emission Credits	[2]								0		0
Amortization of Nuclear Fuel Lease	[3]								0		0
Asset Retirement Obligation, Accretion Expense	[4]								0		0
Total depreciation, amortization and accretion									72		81
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		3	[12]	4	[12]			3	7	[12]	8	[12]
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									2		10
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
Inventory Write-down									0		1
Merger related commitments									0	[9]	120
Asset Retirement Obligation, Revision of Estimate											2
Other									(2)		(3)
Total other noncash operating activities									7		138
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									(14)		6
Non cash Fair Value Adjustment for CENG											0
Capitalized Costs, Asset Retirement Costs				0		0					0
Pepco Holdings LLC [Member] | Successor [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation						111	[1]		227
Regulatory assets						63	[1]		105
Amortization of intangible assets, net						0	[1]		0
Amortization of Power Contracts Emission Credits						0	[2]		0
Amortization of Nuclear Fuel Lease						0	[3]		0
Asset Retirement Obligation, Accretion Expense						0	[4]		0
Total depreciation, amortization and accretion						174			332
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		24				31			48
Gain (loss) on equity method investments									0
Provision for uncollectible accounts						7			6
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			2
Amortization of rate stabilization deferral						0			(15)
Amortization of debt fair value adjustment						0			3
Discrete impacts from EIMA						0			0
Amortization of debt costs						0			0
Inventory Write-down						0			1
Merger related commitments						358			(8)	[9]
Restructuring Costs						54			3
Other						(7)			(6)
Total other noncash operating activities						444			28
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid						(4)			(8)
Business Combination, Contingent Consideration, Liability, Noncurrent		$ 0		53		53			$ 0		$ 53
Payments to Acquire Businesses, Gross						33
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
Amortization of Nuclear Fuel Lease	[3]							0
Asset Retirement Obligation, Accretion Expense	[4]							0
Total depreciation, amortization and accretion								152
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)				$ 27		31		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
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid								11
Non cash Fair Value Adjustment for CENG								$ 0
Pepco Holdings LLC [Member] | Deferred Compensation, Share-based Payments [Member] | Successor [Member]
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Payments to Acquire Businesses, Gross						29
Pepco Holdings LLC [Member] | Fair Value Measurement [Domain] | Successor [Member]
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						$ 127
[1]	Included in Depreciation and amortization on the Registrants' Consolidated Statements of Operations and Comprehensive Income.
[2]	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]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income
[5]	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
[6]	Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded in Operating revenues.
[7]	Reflects the change in distribution rates pursuant to EIMA and FEJA, which allows for the recovery of distribution costs by a utility through a pre-established performance-based formula rate tariff. Beginning June 1, 2017, also reflects the change in energy efficiency rates pursuant to FEJA, which allows for the recovery of energy efficiency costs by a utility through a pre-established performance-based formula rate tariff. See Note 5 — Regulatory Matters for more information
[8]	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.
[9]	See Note 4 — Mergers, Acquisitions and Dispositions for additional information related to the merger with PHI.
[10]	(c)FitzPatrick net benefit costs are included for the period after acquisition.
[11]	See Note 11— Income Taxes for discussion of the like-kind exchange tax position
[12]	Pepco's, DPL's, ACE's and PHISCO's pension and postretirement benefit costs for the six months ended June 30, 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 Infor116

Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2017		Dec. 31, 2016
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	$ 19,735	[1]	$ 19,169	[2]
Accounts receivable, net
Allowance for uncollectible accounts	322		334
Exelon Generation Co L L C [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	10,550	[1]	10,562	[2]
Accounts receivable, net
Allowance for uncollectible accounts	102		91
Exelon Generation Co L L C [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,016		3,186
Commonwealth Edison Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	4,122		3,937
Accounts receivable, net
Allowance for uncollectible accounts	71		70
PECO Energy Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,330		3,253
Accounts receivable, net
Allowance for uncollectible accounts	59		61
Baltimore Gas and Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,358		3,254
Accounts receivable, net
Allowance for uncollectible accounts	26		32
Pepco Holdings LLC [Member] | Successor [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	360		195
Accounts receivable, net
Allowance for uncollectible accounts	64		80
Potomac Electric Power Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,131		3,050
Accounts receivable, net
Allowance for uncollectible accounts	25		29
Delmarva Power and Light Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	1,212		1,175
Accounts receivable, net
Allowance for uncollectible accounts	19		24
Atlantic City Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	1,042		1,016
Accounts receivable, net
Allowance for uncollectible accounts	$ 20		$ 27
[1]	Includes accumulated amortization of nuclear fuel in the reactor core of $3,016 million
[2]	Includes accumulated amortization of nuclear fuel in the reactor core of $3,186 million

Supplemental Financial Infor117

Supplemental Financial Information - Narrative (Details) - PECO Energy Co [Member] - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net	$ 11	$ 9
Financing Receivable, Allowance for Credit Losses	13	13
Low To Medium Risk [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses	1	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	$ 9	$ 9

Segment Information - Narrative

Segment Information - Narrative (Details)	6 Months Ended
	Jun. 30, 2017Reportable_segment
Segment Reporting Information [Line Items]
Number of reportable segments	12
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	6
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	3

Segment Information - Reconcili

Segment Information - Reconciliation to Consolidated Financial Statements (Details) - USD ($) $ in Millions		3 Months Ended							6 Months Ended
		Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2016		Mar. 23, 2016	Jun. 30, 2017		Jun. 30, 2016		Dec. 31, 2016
Segment Reporting Information [Line Items]
Competitive Energy Revenue		$ 3,453	[1]	$ 3,301	[1]				$ 6,845	[2]	$ 6,732	[2]
Revenue from Purchased Oil and Gas		430	[1]	367	[1]				1,348	[2]	1,189	[2]
Other Operating Income		25	[1]	(434)	[1]				275	[2]	(213)	[2]
Electric Revenue		3,511	[1]	3,480	[1]				7,156	[2]	6,136	[2]
Gas Domestic Regulated Revenue		204	[1]	197	[1]				757	[2]	641	[2]
Sales Revenue, Services, Other		0	[1]	(1)	[1]				0	[2]	0	[2]
Operating revenues from affiliates		0	[3]	1	[3]				0	[4]	2	[4]
Net income (loss)		64		306					1,046		430
Assets		117,104							117,104				$ 114,904
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		268		358					598		627
Net income (loss)		(266)		28					144		285
Assets		48,130							48,130				46,974
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		(266)	[1]	(354)	[1]				(592)	[2]	(620)	[2]
Revenue from Purchased Oil and Gas		0	[1]	0	[1]				0	[2]	0	[2]
Other Operating Income		0	[1]	(1)	[1]				(1)	[2]	(1)	[2]
Electric Revenue		(7)	[1]	(7)	[1]				(16)	[2]	(15)	[2]
Gas Domestic Regulated Revenue		(1)	[1]	(2)	[1]				(4)	[2]	(5)	[2]
Sales Revenue, Services, Other		(461)	[1]	(409)	[1]				(893)	[2]	(826)	[2]
Operating revenues from affiliates		(734)	[3]	(771)	[3]				(1,503)	[4]	(1,466)	[4]
Net income (loss)		0		(1)					0		(2)
Assets		(11,986)							(11,986)				(11,334)
Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		(4)	[5]	(4)	[5]	$ (5)	[6]		(9)	[6]
Gas Domestic Regulated Revenue		0	[5]	0	[5]	0	[6]		0	[6]
Sales Revenue, Services, Other		(1)	[5]	0	[5]	0	[6]		(2)	[6]
Operating revenues from affiliates		(5)		(4)		(5)			(9)
Net income (loss)		12		10		23			23
Assets		(4,971)							(4,971)				(4,724)
Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	[6]							$ (4)
Gas Domestic Regulated Revenue	[6]							0
Sales Revenue, Services, Other	[6]							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		3,719	[1],[7]	3,655	[1],[7]				7,437	[2],[8]	7,352	[2],[8]
Revenue from Purchased Oil and Gas		430	[1],[7]	367	[1],[7]				1,348	[2],[8]	1,189	[2],[8]
Other Operating Income		25	[1],[7]	(433)	[1],[7]				276	[2],[8]	(212)	[2],[8]
Electric Revenue		0	[1],[7]	0	[1],[7]				0	[2],[8]	0	[2],[8]
Gas Domestic Regulated Revenue		0	[1],[7]	0	[1],[7]				0	[2],[8]	0	[2],[8]
Sales Revenue, Services, Other		0	[1],[7]	0	[1],[7]				0	[2],[8]	0	[2],[8]
Net income (loss)		(266)	[7]	28	[7]				144	[8]	285	[8]
Assets	[7]	48,130							48,130				46,974
Exelon Generation Co L L C [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		266	[3],[7]	355	[3],[7]				594	[4],[8]	621	[4],[8]
Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		0	[1]	0	[1]				0	[2]	0	[2]
Revenue from Purchased Oil and Gas		0	[1]	0	[1]				0	[2]	0	[2]
Other Operating Income		0	[1]	0	[1]				0	[2]	0	[2]
Electric Revenue		1,357	[1]	1,286	[1]				2,656	[2]	2,535	[2]
Gas Domestic Regulated Revenue		0	[1]	0	[1]				0	[2]	0	[2]
Sales Revenue, Services, Other		0	[1]	0	[1]				0	[2]	0	[2]
Net income (loss)		118		145					259		260
Assets		29,160							29,160				28,335
Commonwealth Edison Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		3	[3]	3	[3]				9	[4]	8	[4]
PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		0	[1]	0	[1]				0	[2]	0	[2]
Revenue from Purchased Oil and Gas		0	[1]	0	[1]				0	[2]	0	[2]
Other Operating Income		0	[1]	0	[1]				0	[2]	0	[2]
Electric Revenue		550	[1]	587	[1]				1,140	[2]	1,232	[2]
Gas Domestic Regulated Revenue		80	[1]	77	[1]				286	[2]	273	[2]
Sales Revenue, Services, Other		0	[1]	0	[1]				0	[2]	0	[2]
Net income (loss)		88		100					215		224
Assets		11,041							11,041				10,831
PECO Energy Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		2	[3]	2	[3]				3	[4]	4	[4]
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		0	[1]	0	[1]				0	[2]	0	[2]
Revenue from Purchased Oil and Gas		0	[1]	0	[1]				0	[2]	0	[2]
Other Operating Income		0	[1]	0	[1]				0	[2]	0	[2]
Electric Revenue		571	[1]	584	[1]				1,237	[2]	1,264	[2]
Gas Domestic Regulated Revenue		103	[1]	96	[1]				388	[2]	345	[2]
Sales Revenue, Services, Other		0	[1]	0	[1]				0	[2]	0	[2]
Net income (loss)		45		34					169		135
Assets		8,786							8,786				8,704
Baltimore Gas and Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		3	[3]	4	[3]				8	[4]	9	[4]
Pepco Holdings LLC [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		0	[1],[9]	0	[1],[9]				0	[2],[10]	0	[2],[10]
Revenue from Purchased Oil and Gas		0	[1],[9]	0	[1],[9]				0	[2],[10]	0	[2],[10]
Other Operating Income		0	[1],[9]	0	[1],[9]				0	[2],[10]	0	[2],[10]
Electric Revenue		1,040	[1],[5],[9]	1,030	[1],[5],[9]	1,120	[6]		2,138	[2],[6],[10]	1,120	[2],[10]
Gas Domestic Regulated Revenue		22	[1],[5],[9]	26	[1],[5],[9]	28	[6]		87	[2],[6],[10]	28	[2],[10]
Sales Revenue, Services, Other		12	[1],[5],[9]	10	[1],[5],[9]	23	[6]		23	[2],[6],[10]	23	[2],[10]
Net income (loss)		66	[9]	52	[9]	(257)			205	[10]	(257)	[10]
Assets	[9]	21,190							21,190				21,025
Pepco Holdings LLC [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	[6]							1,096
Gas Domestic Regulated Revenue	[6]							57
Sales Revenue, Services, Other	[6]							0
Net income (loss)								19
Pepco Holdings LLC [Member] | Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		12	[3],[9]	10	[3],[9]	23			23	[4],[10]	23	[4],[10]
Pepco Holdings LLC [Member] | Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates								0
Potomac Electric Power Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		514	[5]	509	[5]	550	[6]		1,045	[6]
Gas Domestic Regulated Revenue		0	[5]	0	[5]	0	[6]		0	[6]
Sales Revenue, Services, Other		0	[5]	0	[5]	0	[6]		0	[6]
Net income (loss)		43		49		(92)			101
Assets		7,648							7,648				7,335
Potomac Electric Power Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	[6]							511
Gas Domestic Regulated Revenue	[6]							0
Sales Revenue, Services, Other	[6]							0
Net income (loss)								32
Potomac Electric Power Company [Member] | Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		1		1		2			3
Potomac Electric Power Company [Member] | Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates								1
Delmarva Power and Light Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		260	[5]	255	[5]	279	[6]		557	[6]
Gas Domestic Regulated Revenue		22	[5]	26	[5]	29	[6]		87	[6]
Sales Revenue, Services, Other		0	[5]	0	[5]	0	[6]		0	[6]
Net income (loss)		19		12		(86)			76
Assets		4,235							4,235				4,153
Delmarva Power and Light Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	[6]							279
Gas Domestic Regulated Revenue	[6]							56
Sales Revenue, Services, Other	[6]							0
Net income (loss)								26
Delmarva Power and Light Company [Member] | Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		2		2		2			4
Delmarva Power and Light Company [Member] | Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates								2
Atlantic City Electric Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		270	[5]	270	[5]	293	[6]		544	[6]
Gas Domestic Regulated Revenue		0	[5]	0	[5]	0	[6]		0	[6]
Sales Revenue, Services, Other		0	[5]	0	[5]	0	[6]		0	[6]
Net income (loss)		8		3		(102)			36
Assets		3,478							3,478				3,457
Atlantic City Electric Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	[6]							268
Gas Domestic Regulated Revenue	[6]							0
Sales Revenue, Services, Other	[6]							0
Net income (loss)								5
Atlantic City Electric Company [Member] | Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		1		1		1			1
Atlantic City Electric Company [Member] | Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates								1
Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		0	[1],[11]	0	[1],[11]				0	[2],[12]	0	[2],[12]
Revenue from Purchased Oil and Gas		0	[1],[11]	0	[1],[11]				0	[2],[12]	0	[2],[12]
Other Operating Income		0	[1],[11]	0	[1],[11]				0	[2],[12]	0	[2],[12]
Electric Revenue		0	[1],[11]	0	[1],[11]				1	[2],[12]	0	[2],[12]
Gas Domestic Regulated Revenue		0	[1],[11]	0	[1],[11]				0	[2],[12]	0	[2],[12]
Sales Revenue, Services, Other		449	[1],[11]	398	[1],[11]				870	[2],[12]	803	[2],[12]
Net income (loss)		13	[11]	(52)	[11]				54	[12]	(215)	[12]
Assets	[11]	10,783							10,783				10,369
Corporate and Other [Member] | Corporate, Non-Segment [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		0	[5],[13]	0	[5],[13]	3	[6],[14]		1	[6],[14]
Gas Domestic Regulated Revenue		0	[5],[13]	0	[5],[13]	(1)	[6],[14]		0	[6],[14]
Sales Revenue, Services, Other		13	[5],[13]	10	[5],[13]	23	[6],[14]		25	[6],[14]
Net income (loss)		(16)	[13]	(22)	[13]	0	[14]		(31)	[14]
Assets	[13]	10,800							10,800				$ 10,804
Corporate and Other [Member] | Corporate, Non-Segment [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	[6],[14]							42
Gas Domestic Regulated Revenue	[6],[14]							1
Sales Revenue, Services, Other	[6],[14]							0
Net income (loss)	[14]							(44)
Corporate and Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		448	[3],[11]	398	[3],[11]				866	[4],[12]	803	[4],[12]
Corporate and Other [Member] | Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		13	[13]	10	[13]	23	[14]		24	[14]
Corporate and Other [Member] | Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[14]							$ 0
Generation Mid Atlantic [Member] | PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		34		64					79		143
Generation Mid Atlantic [Member] | Baltimore Gas And Electric Company Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		99		135					233		306
Generation Mid Atlantic [Member] | PotomacElectricPowerCompanyAffiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		68		88		94			152
Generation Mid Atlantic [Member] | DelmarvaPowerandLightCompanyAffiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		40		43		47			91
Generation Mid Atlantic [Member] | AtlanticCityElectricCompanyAffiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		7		12		$ 13			16
Generation Mid Atlantic [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		9		(16)					5		(28)
Generation Midwest [Member] | Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		18		13					23		18
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		$ (8)		$ 7					$ (5)		$ 13
[1]	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 June 30, 2017 and 2016.
[2]	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 six months ended June 30, 2017 and 2016.
[3]	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.
[4]	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.
[5]	Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 18 — Supplemental Financial Information for total utility taxes for the three months ended June 30, 2017 and 2016.
[6]	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 six months ended June 30, 2017 and 2016.
[7]	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 June 30, 2017 include revenue from sales to PECO of $34 million, sales to BGE of $99 million, sales to Pepco of $68 million, sales to DPL of $40 million, and sales to ACE of $7 million in the Mid-Atlantic region, and sales to ComEd of $18 million in the Midwest region. For the three months ended June 30, 2016, intersegment revenues for Generation include revenue from sales to PECO of $64 million, sales to BGE of $135 million, sales to Pepco of $88 million, sales to DPL of $43 million, and sales to ACE of $12 million in the Mid-Atlantic region, and sales to ComEd of $13 million in the Midwest region.
[8]	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 six months ended June 30, 2017 include revenue from sales to PECO of $79 million, sales to BGE of $233 million, sales to Pepco of $152 million, sales to DPL of $91 million, and sales to ACE of $16 million in the Mid-Atlantic region, and sales to ComEd of $23 million in the Midwest region. For the six months ended June 30, 2016, intersegment revenues for Generation include revenue from sales to PECO of $143 million and sales to BGE of $306 million in the Mid-Atlantic region, and sales to ComEd of $18 million in the Midwest region. For the Successor period of March 24, 2016 to June 30, 2016, intersegment revenues for Generation include revenue from sales to Pepco of $94 million, sales to DPL of $47 million, and sales to ACE of $13 million in the Mid-Atlantic region.
[9]	Amounts included represent activity for PHI's successor period, three months ended June 30, 2017 and 2016. PHI includes the three reportable segments: Pepco, DPL and ACE.
[10]	Amounts included represent activity for PHI's successor period, six months ended June 30, 2017 and March 24, 2016 through June 30, 2016. PHI includes the three reportable segments: Pepco, DPL and ACE. See tables below for PHI's predecessor period, including Pepco, DPL and ACE, for January 1, 2016 to March 23, 2016.
[11]	Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities.
[12]	Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities.
[13]	Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities.
[14]	Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities. For the predecessor period presented, Other includes the activity of PHI’s unregulated businesses which were distributed to Exelon and Generation as a result of the PHI Merger.

Segment Information - Generatio

Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ (7,623)		$ (6,910)		$ (16,381)		$ (14,485)
Operating revenues from affiliates	0	[1]	1	[1]	0	[2]	2	[2]
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(1,365)		(1,416)		(2,790)		(2,936)
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	(1,050)		(1,083)		(2,102)		(2,179)
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	(433)		(351)		(980)		(821)
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(347)		(346)		(654)		(549)
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	(247)		(207)		(438)		(370)
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	(259)		(223)		(443)		(447)
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	(3,701)		(3,626)		(7,407)		(7,302)
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(473)	[3]	(37)	[3]	(1,654)	[4]	(1,027)	[4]
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	(4,174)		(3,589)		(9,061)		(8,329)
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(1,356)	[5]	(1,432)	[5]	(2,785)	[6]	(2,964)	[6]
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	(1,058)	[5]	(1,076)	[5]	(2,107)	[6]	(2,166)	[6]
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	(438)	[5]	(352)	[5]	(987)	[6]	(823)	[6]
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(352)	[5]	(356)	[5]	(662)	[6]	(573)	[6]
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	(247)	[5]	(207)	[5]	(439)	[6]	(370)	[6]
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	(268)	[5]	(232)	[5]	(457)	[6]	(456)	[6]
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	(3,719)	[5]	(3,655)	[5]	(7,437)	[6]	(7,352)	[6]
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Amortization of intangible assets related to commodity contracts	(15)		(9)		(17)		11
Unrealized Gain (Loss) on Securities	(143)		(615)		(98)		(553)
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	(4,174)	[5]	(3,589)	[5]	(9,061)	[6]	(8,329)	[6]
Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(455)	[3],[5]	66	[3],[5]	(1,624)	[4],[6]	(977)	[4],[6]
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(734)	[1]	(771)	[1]	(1,503)	[2]	(1,466)	[2]
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	9		(16)		5		(28)
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(8)		7		(5)		13
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(5)		(1)		(7)		(2)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(5)		(10)		(8)		(24)
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	0		0		(1)		0
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(9)		(9)		(14)		(9)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(18)		(29)		(30)		(50)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	18	[3]	29	[3]	30	[4]	50	[4]
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	$ 0		$ 0		$ 0		$ 0
[1]	Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
[2]	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.
[3]	Other represents activities not allocated to a region. See text above for a description of included activities. Includes a $15 million and $9 million decrease to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the three months ended June 30, 2017 and 2016, respectively, unrealized mark-to-market losses of $143 million and $615 million for the three months ended June 30, 2017 and 2016, respectively, and elimination of intersegment revenues.
[4]	Other represents activities not allocated to a region. See text above for a description of included activities. Includes a $17 million decrease to revenues and an $11 million increase to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the six months ended June 30, 2017 and 2016, respectively, unrealized mark-to-market losses of $98 million and $553 million for the six months ended June 30, 2017 and 2016, respectively, and elimination of intersegment revenues.
[5]	Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants.
[6]	Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants.

Segment Information - Genera121

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	$ 783		$ 828		$ 1,557		$ 1,669
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	728		728		1,443		1,449
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	147		110		257		191
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	230		267		385		395
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	70		77		138		138
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	90		96		152		174
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	2,048		2,106		3,932		4,016
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	(31)	[1]	(94)	[1]	174	[2]	293	[2]
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	2,017		2,012		4,106		4,309
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	757	[3]	830	[3]	1,513	[4]	1,661	[4]
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	728	[3]	724	[3]	1,431	[4]	1,443	[4]
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	157	[3]	118	[3]	271	[4]	204	[4]
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	230	[3]	270	[3]	385	[4]	408	[4]
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	121	[3]	111	[3]	214	[4]	192	[4]
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	134	[3]	123	[3]	240	[4]	211	[4]
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	2,127	[3]	2,176	[3]	4,054	[4]	4,119	[4]
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	(110)	[1],[3]	(164)	[1],[3]	52	[2],[4]	190	[2],[4]
Amortization Of Intangible Assets Related To Commodity Contracts For Revenue Net Purchased Power And Fuel	(20)		(12)		(22)		7
Unrealized Gain on Securities	(184)		(304)		(233)		(201)
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	2,017	[3]	2,012	[3]	4,106	[4]	4,309	[4]
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	26		(2)		44		8
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	0		4		12		6
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(10)		(8)		(14)		(13)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	0		(3)		0		(13)
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(51)		(34)		(76)		(54)
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(44)		(27)		(88)		(37)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(79)		(70)		(122)		(103)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	79	[1]	70	[1]	122	[2]	103	[2]
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	$ 0		$ 0		$ 0		$ 0
[1]	Other represents activities not allocated to a region. See text above for a description of included activities. Includes a $20 million and $12 million decrease to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the three months ended June 30, 2017 and 2016, respectively, unrealized mark-to-market losses of $184 million and $304 million for the three months ended June 30, 2017 and 2016, respectively, and the elimination of intersegment revenue net of purchased power and fuel expense.
[2]	Other represents activities not allocated to a region. See text above for a description of included activities. Includes a $22 million decrease to RNF and a $7 million increase to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the six months ended June 30, 2017 and 2016, respectively, unrealized mark-to-market losses of $233 million and $201 million for the six months ended June 30, 2017 and 2016, respectively, and the elimination of intersegment revenue net of purchased power and fuel expense.
[3]	Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants.
[4]	Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants.

Subsequent Event (Details)

Subsequent Event (Details) $ in Millions	Jul. 06, 2017USD ($)MW	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)MW	Jun. 30, 2016USD ($)
Subsequent Event [Line Items]
Power Volume | MW				220
Taxes, Miscellaneous		$ 420	$ 394	$ 857	$ 720
Subsequent Event [Member] | ExGen Renewables Holdings, LLC [Member]
Subsequent Event [Line Items]
Proceeds from Sale of Interest in Partnership Unit	$ 400
PartnersCapitalPercentageSold	49.00%
Power Volume | MW	1,296
Taxes, Miscellaneous	$ 120

Uncategorized Items - exc-20170

Label	Element	Value
Pepco Holdings LLC [Member] | Predecessor [Member]
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	$ 2,000,000
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	0
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	293,000,000
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	(18,000,000)
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(46,000,000)
Proceeds from Contributions from Parent	us-gaap_ProceedsFromContributionsFromParent	0
Payments of Distributions to Affiliates	us-gaap_PaymentsOfDistributionsToAffiliates	0
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	28,000,000
Change in Exelon intercompany money pool borrowings	exc_ChangeInExelonIntercompanyMoneyPoolBorrowings	0
Cash and Cash Equivalents, at Carrying Value	us-gaap_CashAndCashEquivalentsAtCarryingValue	319,000,000
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	11,000,000
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	(3,000,000)
Payments to Acquire Property, Plant, and Equipment	us-gaap_PaymentsToAcquirePropertyPlantAndEquipment	273,000,000
Gain (Loss) on Disposition of Assets	us-gaap_GainLossOnDispositionOfAssets1	0
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	0
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	5,000,000
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	42,000,000
Increase (Decrease) in Other Operating Assets and Liabilities, Net	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet	8,000,000
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	12,000,000
Repayments of Debt, Maturing in More than Three Months	us-gaap_RepaymentsOfDebtMaturingInMoreThanThreeMonths	0
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	19,000,000
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	68,000,000
Net Cash Provided by (Used in) Financing Activities	us-gaap_NetCashProvidedByUsedInFinancingActivities	372,000,000
Proceeds from Short-term Debt, Maturing in More than Three Months	us-gaap_ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths	500,000,000
Payment for Pension and Other Postretirement Benefits	us-gaap_PensionAndOtherPostretirementBenefitContributions	4,000,000
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	0
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	(121,000,000)
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	4,000,000
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	2,000,000
Pepco Holdings LLC [Member] | Successor [Member]
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	(3,000,000)
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	1,000,000
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	(25,000,000)
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	0
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(444,000,000)
Payments of Distributions to Affiliates	us-gaap_PaymentsOfDistributionsToAffiliates	124,000,000
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	(56,000,000)
Change in Exelon intercompany money pool borrowings	exc_ChangeInExelonIntercompanyMoneyPoolBorrowings	28,000,000
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	16,000,000
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	34,000,000
Payments to Acquire Property, Plant, and Equipment	us-gaap_PaymentsToAcquirePropertyPlantAndEquipment	339,000,000
Gain (Loss) on Disposition of Assets	us-gaap_GainLossOnDispositionOfAssets1	0
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	39,000,000
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	(8,000,000)
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	(35,000,000)
Increase (Decrease) in Other Operating Assets and Liabilities, Net	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet	237,000,000
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	22,000,000
Repayments of Debt, Maturing in More than Three Months	us-gaap_RepaymentsOfDebtMaturingInMoreThanThreeMonths	300,000,000
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	(16,000,000)
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	0
Net Cash Provided by (Used in) Financing Activities	us-gaap_NetCashProvidedByUsedInFinancingActivities	137,000,000
Proceeds from Short-term Debt, Maturing in More than Three Months	us-gaap_ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths	0
Payment for Pension and Other Postretirement Benefits	us-gaap_PensionAndOtherPostretirementBenefitContributions	2,000,000
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	15,000,000
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	(537,000,000)
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	0
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	0
Common Stock [Member] | PECO Energy Co [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	0
AOCI Attributable to Parent [Member] | PECO Energy Co [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	$ 0