Commonwealth Edison 10-Q 2 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	9 Months Ended
	Sep. 30, 2017shares
Entity Registrant Name	EXELON CORP
Entity Central Index Key	1,109,357
Document Type	10-Q
Document Period End Date	Sep. 30, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
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	960,852,473
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	127,021,214
PECO Energy Co [Member]
Entity Registrant Name	PECO ENERGY CO
Entity Central Index Key	78,100
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	170,478,507
Baltimore Gas and Electric Company [Member]
Entity Registrant Name	BALTIMORE GAS AND ELECTRIC
Entity Central Index Key	9,466
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	1,000
Pepco Holdings LLC [Member]
Entity Registrant Name	PEPCO HOLDINGS LLC
Entity Central Index Key	1,135,971
Entity Filer Category	Non-accelerated Filer
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	9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016		Mar. 23, 2016	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Operating revenues [Abstract]
Operating Revenue	$ 4,456		$ 4,535				$ 12,924		$ 12,243
Regulated Operating Revenue	4,313		4,467				12,225		11,243
Electric operating revenues	4,164	[1]	4,330	[1]			11,318	[2]	10,461	[2]
Natural gas operating revenues	149	[1]	137	[1]			906	[2]	781	[2]
Operating revenues from affiliates	0	[3]	1	[3]			2	[4]	3	[4]
Revenues	8,769		9,002				25,149		23,486
Operating expenses
Competitive businesses purchased power and fuel	2,316		2,584				7,268		6,599
Cost of Purchased Power	1,226		1,170				3,259		2,863
Operating and maintenance	2,300		2,338				7,732		7,677
Depreciation and amortization	1,002		1,195				2,814		2,821
Taxes other than income	456		449				1,313		1,168
Total operating expenses	7,300		7,736				22,386		21,128
Gain (Loss) on Disposition of Other Assets	(1)		1				4		41
Bargain purchase gain	7		0				233		0
Operating income	1,475		1,267				3,000		2,399
Other income and (deductions)
Interest expense, net	(377)		(506)				(1,165)		(1,148)
Interest expense to affiliates	(9)		(10)				(29)		(31)
Other, net	237		120				725		377
Total other income and (deductions)	(149)		(396)				(469)		(802)
Income before income taxes	1,326		871				2,531		1,597
Income taxes	452		340				595		625
Equity in losses of unconsolidated affiliates	(7)		(5)				(25)		(16)
Net income	867		526				1,911		956
Net income attributable to noncontrolling interests and preference stock dividends	43		36				12		26
Net income attributable to common shareholders	824		490				1,899		930
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost	(14)		(12)				(42)		(35)
Actuarial loss reclassified to periodic benefit cost	49		47				147		140
Pension and non-pension postretirement benefit plan valuation adjustment	3		0				(55)		(3)
Unrealized gain (loss) on cash flow hedges	0		3				5		(4)
Other Comprehensive Income Unrealized Income Loss On Equity Investments Arising During Period Net Of Tax	1		(4)				5		(10)
Unrealized gain on foreign currency translation	4		2				7		8
Unrealized gain on marketable securities	1		0				2		0
Other comprehensive income	44		36				69		96
Comprehensive income	911		562				1,980		1,052
Comprehensive income attributable to noncontrolling interests and preference stock dividends	43		31				10		21
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 868		$ 531				$ 1,970		$ 1,031
Average shares of common stock outstanding:
Weighted average common shares outstanding — basic	962		925				941		924
Weighted average common shares outstanding — diluted	965		927				943		926
Earnings per average common share:
Basic	$ 0.86		$ 0.53				$ 2.02		$ 1.01
Diluted	0.85		0.53				2.01		1
Dividends declared per common share	$ 0.33		$ 0.32				$ 0.98		$ 0.95
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating Revenue	$ 4,455		$ 4,533				$ 12,918		$ 12,234
Operating revenues from affiliates	296		502				894		1,129
Revenues	4,751		5,035				13,812		13,363
Operating expenses
Cost of Purchased Power	2,315		2,584				7,267		6,599
Purchased power from affiliate	16		5				19		10
Operating and maintenance	1,203		1,189				4,335		3,855
Operating and maintenance from affiliates	171		147				536		478
Depreciation and amortization	410		632				1,046		1,329
Taxes other than income	141		136				425		380
Total operating expenses	4,256		4,693				13,628		12,651
Gain (Loss) on Disposition of Other Assets	(2)		0				3		31
Bargain purchase gain	7		0				233		0
Operating income	500		342				420		743
Other income and (deductions)
Interest expense, net	(103)		(67)				(313)		(243)
Interest expense to affiliates	(10)		(10)				(29)		(30)
Other, net	209		185				648		395
Total other income and (deductions)	96		108				306		122
Income before income taxes	596		450				726		865
Income taxes	240		173				209		293
Equity in losses of unconsolidated affiliates	(8)		(6)				(26)		(16)
Net income	348		271				491		556
Net income attributable to noncontrolling interests	43		35				12		18
Net income attributable to membership interest	305		236				479		538
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		1
Unrealized gain (loss) on cash flow hedges	0		1				5		(3)
Other Comprehensive Income Unrealized Income Loss On Equity Investments Arising During Period Net Of Tax	0		0				4		(4)
Unrealized gain on foreign currency translation	4		2				7		8
Other comprehensive income	4		4				16		2
Comprehensive income	352		275				507		558
Comprehensive income attributable to noncontrolling interests and preference stock dividends	43		30				10		13
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	309		245				497		545
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Electric operating revenues	1,568		1,493				4,215		4,019
Operating revenues from affiliates	3		4				12		12
Revenues	1,571		1,497				4,227		4,031
Operating expenses
Purchased power	489		435				1,178		1,104
Purchased power from affiliate	40		19				63		37
Operating and maintenance	277		327				897		950
Operating and maintenance from affiliates	69		50				199		163
Depreciation and amortization	212		196				631		574
Taxes other than income	80		82				223		222
Total operating expenses	1,167		1,109				3,191		3,050
Gain (Loss) on Disposition of Other Assets	0		1				0		6
Operating income	404		389				1,036		987
Other income and (deductions)
Interest expense, net	(86)		(194)				(265)		(364)
Interest expense to affiliates	(3)		(3)				(10)		(10)
Other, net	5		(80)				14		(72)
Total other income and (deductions)	(84)		(277)				(261)		(446)
Income before income taxes	320		112				775		541
Income taxes	131		75				328		244
Net income	189		37				447		297
Other comprehensive income (loss), net of income taxes
Comprehensive income	189		37				447		297
PECO Energy Co [Member]
Operating revenues [Abstract]
Electric operating revenues	660		738				1,798		1,966
Natural gas operating revenues	53		48				338		322
Operating revenues from affiliates	2		2				5		5
Revenues	715		788				2,141		2,293
Operating expenses
Purchased power	190		171				483		466
Purchased fuel	14		10				126		110
Purchased power from affiliate	31		91				110		233
Operating and maintenance	161		168				488		501
Operating and maintenance from affiliates	36		31				107		103
Depreciation and amortization	72		67				213		201
Taxes other than income	42		46				116		126
Total operating expenses	546		584				1,643		1,740
Operating income	169		204				498		553
Other income and (deductions)
Interest expense, net	(28)		(27)				(84)		(83)
Interest expense to affiliates	(3)		(3)				(9)		(9)
Other, net	2		2				6		6
Total other income and (deductions)	(29)		(28)				(87)		(86)
Income before income taxes	140		176				411		467
Income taxes	28		54				84		121
Net income	112		122				327		346
Other comprehensive income (loss), net of income taxes
Comprehensive income	112		122				327		346
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues	657		733				1,890		1,993
Natural gas operating revenues	78		72				461		412
Operating revenues from affiliates	3		7				12		16
Revenues	738		812				2,363		2,421
Operating expenses
Purchased power	159		164				407		399
Purchased fuel	13		14				118		109
Purchased power from affiliate	97		182				328		486
Operating and maintenance	138		150				421		494
Operating and maintenance from affiliates	37		28				111		94
Depreciation and amortization	109		101				348		307
Taxes other than income	61		58				180		172
Total operating expenses	614		697				1,913		2,061
Operating income	124		115				450		360
Other income and (deductions)
Interest expense, net	(24)		(24)				(69)		(64)
Interest expense to affiliates	(2)		(4)				(11)		(12)
Other, net	4		5				12		16
Total other income and (deductions)	(22)		(23)				(68)		(60)
Income before income taxes	102		92				382		300
Income taxes	40		36				151		109
Net income	62		56				231		191
Preference stock dividends	0		2				0		8
Net income attributable to common shareholders	62		54				231		183
Other comprehensive income (loss), net of income taxes
Comprehensive income	62		56				231		191
Comprehensive income attributable to noncontrolling interests and preference stock dividends	0		2				0		8
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	62		54				231		183
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	1,280		1,366			$ 2,485	3,417
Natural gas operating revenues	18		17			46	105
Operating revenues from affiliates	12		11			34	35
Revenues	1,310		1,394			2,565	3,557
Operating expenses
Purchased power	354		370			658	901
Purchased fuel	7		6			17	46
Purchased power from affiliate	112		207			362	371
Operating and maintenance	214		200			870	666
Operating and maintenance from affiliates	37		26			51	108
Depreciation and amortization	179		182			355	511
Taxes other than income	122		124			248	344
Total operating expenses	1,025		1,115			2,561	2,947
Gain (Loss) on Disposition of Other Assets	0						1
Operating income	285		279			4	611
Other income and (deductions)
Interest expense, net	(62)		(64)			(135)	(183)
Other, net	13		19			31	40
Total other income and (deductions)	(49)		(45)			(104)	(143)
Income before income taxes	236		234			(100)	468
Income taxes	83		68			(9)	109
Net income	153		166			(91)	359
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	153		166			$ (91)	359
Potomac Electric Power Company [Member]
Operating revenues [Abstract]
Electric operating revenues	603		634				1,645		1,692
Operating revenues from affiliates	1		1				4		3
Revenues	604		635				1,649		1,695
Operating expenses
Purchased power	111		84				268		340
Purchased power from affiliate	57		129				210		223
Operating and maintenance	89		100				296		488
Operating and maintenance from affiliates	14		9				40		20
Depreciation and amortization	82		76				242		221
Taxes other than income	102		105				282		287
Total operating expenses	455		503				1,338		1,579
Gain (Loss) on Disposition of Other Assets	0		0				1		8
Operating income	149		132				312		124
Other income and (deductions)
Interest expense, net	(31)		(30)				(89)		(98)
Other, net	7		12				22		28
Total other income and (deductions)	(24)		(18)				(67)		(70)
Income before income taxes	125		114				245		54
Income taxes	38		35				57		34
Net income	87		79				188		20
Other comprehensive income (loss), net of income taxes
Comprehensive income	87		79				188		20
Delmarva Power and Light Company [Member]
Operating revenues [Abstract]
Electric operating revenues	307		312				860		866
Natural gas operating revenues	18		17				105		102
Operating revenues from affiliates	2		2				6		6
Revenues	327		331				971		974
Operating expenses
Purchased power	75		81				215		297
Purchased fuel	7		6				46		41
Purchased power from affiliate	47		63				138		110
Operating and maintenance	71		50				204		327
Operating and maintenance from affiliates	8		5				23		11
Depreciation and amortization	45		44				124		120
Taxes other than income	15		14				43		42
Total operating expenses	268		263				793		948
Gain (Loss) on Disposition of Other Assets	0		4				0		4
Operating income	59		72				178		30
Other income and (deductions)
Interest expense, net	(13)		(12)				(38)		(37)
Other, net	4		3				10		9
Total other income and (deductions)	(9)		(9)				(28)		(28)
Income before income taxes	50		63				150		2
Income taxes	19		19				43		18
Net income	31		44				107		(16)
Other comprehensive income (loss), net of income taxes
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	31		44				107		(16)
Atlantic City Electric Company [Member]
Operating revenues [Abstract]
Electric operating revenues	370		420				913		979
Operating revenues from affiliates	0		1				2		3
Revenues	370		421				915		982
Operating expenses
Purchased power	169		206				418		491
Purchased power from affiliate	7		15				24		29
Operating and maintenance	66		62				205		336
Operating and maintenance from affiliates	6		5				20		10
Depreciation and amortization	41		49				113		130
Taxes other than income	2		1				6		6
Total operating expenses	291		338				786		1,002
Gain (Loss) on Disposition of Other Assets	0		0				0		1
Operating income	79		83				129		(19)
Other income and (deductions)
Interest expense, net	(15)		(15)				(46)		(47)
Other, net	1		2				6		8
Total other income and (deductions)	(14)		(13)				(40)		(39)
Income before income taxes	65		70				89		(58)
Income taxes	24		23				12		(8)
Net income	41		47				77		(50)
Other comprehensive income (loss), net of income taxes
Comprehensive income							$ 77		$ (50)
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 41		$ 47
[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 19 — Supplemental Financial Information for total utility taxes for the three months ended September 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 19 — Supplemental Financial Information for total utility taxes for the nine months ended September 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	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities
Net income	$ 1,911	$ 956
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	3,999	4,009
Impairment of long-lived assets and losses on regulatory assets	488	274
Gain on sales of assets	(5)	(41)
Bargain purchase gain	(233)	0
Deferred income taxes and amortization of investment tax credits	439	623
Net fair value changes related to derivatives	149	100
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(429)	(243)
Other non-cash operating activities	603	1,224
Changes in assets and liabilities:
Accounts receivable	224	(296)
Inventories	(87)	21
Accounts payable and accrued expenses	(593)	296
Option premiums received (paid), net	35	(24)
Collateral (posted) received, net	(100)	757
Income taxes	167	527
Pension and non-pension postretirement benefit contributions	(344)	(283)
Other assets and liabilities	(547)	(537)
Net cash flows provided by (used in) operating activities	5,677	7,363
Cash flows from investing activities
Capital expenditures	(5,556)	(6,368)
Proceeds from nuclear decommissioning trust fund sales	6,848	7,914
Investment in nuclear decommissioning trust funds	(7,044)	(8,093)
Acquisition of businesses, net	(208)	(6,896)
Proceeds from termination of direct financing lease investment	0	360
Changes in restricted cash	(67)	(75)
Proceeds from sale of long-lived assets	219	49
Other investing activities	(2)	(110)
Net cash flows provided by (used in) investing activities	(5,810)	(13,219)
Cash flows from financing activities
Changes in short-term borrowings	(570)	(1,014)
Proceeds from short-term borrowings with maturities greater than 90 days	621	195
Repayments on short-term borrowings with maturities greater than 90 days	(610)	(452)
Issuance of long-term debt	2,616	4,488
Retirement of long-term debt	(1,728)	(944)
Retirement of long-term debt to financing trust	(250)
Restricted proceeds from issuance of long-term debt	0	(30)
Redemption of preference stock	0	(190)
Dividends paid on common stock	(921)	(873)
Common stock issued from treasury stock	1,150	0
Proceeds from employee stock plans	61	36
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	396
Other financing activities	(64)	35
Net cash flows provided by (used in) financing activities	701	1,251
Increase (Decrease) in cash and cash equivalents	568	(4,605)
Cash and cash equivalents at beginning of period	635	6,502
Cash and cash equivalents at end of period	1,203	1,897
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	491	556
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	2,231	2,516
Impairment of long-lived assets and losses on regulatory assets	485	209
Gain on sales of assets	(3)	(31)
Bargain purchase gain	(233)	0
Deferred income taxes and amortization of investment tax credits	(184)	(133)
Net fair value changes related to derivatives	160	112
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(429)	(243)
Other non-cash operating activities	132	129
Changes in assets and liabilities:
Accounts receivable	106	26
Receivables from and payables to affiliates, net	27	(56)
Inventories	(43)	18
Accounts payable and accrued expenses	(257)	9
Option premiums received (paid), net	35	(24)
Collateral (posted) received, net	(77)	759
Income taxes	154	202
Pension and non-pension postretirement benefit contributions	(122)	(122)
Other assets and liabilities	(203)	(204)
Net cash flows provided by (used in) operating activities	2,270	3,723
Cash flows from investing activities
Capital expenditures	(1,654)	(2,651)
Proceeds from nuclear decommissioning trust fund sales	6,848	7,914
Investment in nuclear decommissioning trust funds	(7,044)	(8,093)
Acquisition of businesses, net	(208)	(255)
Changes in restricted cash	(28)	(39)
Proceeds from sale of long-lived assets	218	30
Other investing activities	(35)	(184)
Net cash flows provided by (used in) investing activities	(1,903)	(3,278)
Cash flows from financing activities
Changes in short-term borrowings	(620)	0
Proceeds from short-term borrowings with maturities greater than 90 days	121	195
Repayments on short-term borrowings with maturities greater than 90 days	(110)	(152)
Issuance of long-term debt	789	338
Retirement of long-term debt	(541)	(164)
Change in Exelon intercompany money pool	91	(785)
Distributions to member	(494)	(167)
Contributions from member	102	142
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	396
Other financing activities	(31)	92
Net cash flows provided by (used in) financing activities	(297)	(501)
Increase (Decrease) in cash and cash equivalents	70	(56)
Cash and cash equivalents at beginning of period	290	431
Cash and cash equivalents at end of period	360	375
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	447	297
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	631	574
Deferred income taxes and amortization of investment tax credits	455	398
Other non-cash operating activities	112	122
Changes in assets and liabilities:
Accounts receivable	31	(55)
Receivables from and payables to affiliates, net	346	(9)
Inventories	6	4
Accounts payable and accrued expenses	(706)	145
Collateral (posted) received, net	(22)	(2)
Income taxes	(205)	206
Pension and non-pension postretirement benefit contributions	(38)	(35)
Other assets and liabilities	63	104
Net cash flows provided by (used in) operating activities	1,120	1,749
Cash flows from investing activities
Capital expenditures	(1,698)	(1,950)
Changes in restricted cash	(50)	0
Other investing activities	17	31
Net cash flows provided by (used in) investing activities	(1,731)	(1,919)
Cash flows from financing activities
Changes in short-term borrowings	0	(284)
Issuance of long-term debt	1,000	1,200
Retirement of long-term debt	(425)	(665)
Dividends paid on common stock	(316)	(275)
Contributions from parent	567	188
Other financing activities	(14)	(17)
Net cash flows provided by (used in) financing activities	812	147
Increase (Decrease) in cash and cash equivalents	201	(23)
Cash and cash equivalents at beginning of period	56	67
Cash and cash equivalents at end of period	257	44
PECO Energy Co [Member]
Cash flows from operating activities
Net income	327	346
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	213	201
Deferred income taxes and amortization of investment tax credits	37	69
Other non-cash operating activities	38	49
Changes in assets and liabilities:
Accounts receivable	45	(50)
Receivables from and payables to affiliates, net	(10)	9
Inventories	(5)	5
Accounts payable and accrued expenses	(41)	(12)
Income taxes	51	43
Pension and non-pension postretirement benefit contributions	(23)	(29)
Other assets and liabilities	(29)	(49)
Net cash flows provided by (used in) operating activities	603	582
Cash flows from investing activities
Capital expenditures	(537)	(448)
Changes in Exelon intercompany money pool	74	0
Other investing activities	6	10
Net cash flows provided by (used in) investing activities	(457)	(438)
Cash flows from financing activities
Issuance of long-term debt	325	300
Restricted proceeds from issuance of long-term debt	0	(30)
Dividends paid on common stock	(216)	(208)
Contributions from parent	16	18
Other financing activities	(4)	(3)
Net cash flows provided by (used in) financing activities	121	77
Increase (Decrease) in cash and cash equivalents	267	221
Cash and cash equivalents at beginning of period	63	295
Cash and cash equivalents at end of period	330	516
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	231	191
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	348	307
Impairment of long-lived assets and losses on regulatory assets	0	52
Deferred income taxes and amortization of investment tax credits	141	54
Other non-cash operating activities	52	109
Changes in assets and liabilities:
Accounts receivable	95	(50)
Receivables from and payables to affiliates, net	(13)	(10)
Inventories	(18)	(7)
Accounts payable and accrued expenses	(25)	43
Income taxes	12	19
Pension and non-pension postretirement benefit contributions	(50)	(46)
Other assets and liabilities	(69)	(2)
Net cash flows provided by (used in) operating activities	704	660
Cash flows from investing activities
Capital expenditures	(615)	(611)
Changes in restricted cash	23	(22)
Other investing activities	6	19
Net cash flows provided by (used in) investing activities	(586)	(614)
Cash flows from financing activities
Changes in short-term borrowings	(45)	(210)
Issuance of long-term debt	300	850
Retirement of long-term debt	(41)	(39)
Retirement of long-term debt to financing trust	(250)	0
Redemption of preference stock	0	(190)
Dividends paid on preference stock	0	(8)
Dividends paid on common stock	(148)	(134)
Contributions from parent	77	28
Other financing activities	(5)	(11)
Net cash flows provided by (used in) financing activities	(112)	286
Increase (Decrease) in cash and cash equivalents	6	332
Cash and cash equivalents at beginning of period	23	9
Cash and cash equivalents at end of period	29	341
Pepco Holdings LLC [Member] | Successor [Member]
Cash flows from operating activities
Net income	359
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	511
Deferred income taxes and amortization of investment tax credits	190
Net fair value changes related to derivatives	0
Other non-cash operating activities	66
Changes in assets and liabilities:
Accounts receivable	(42)
Receivables from and payables to affiliates, net	(13)
Inventories	(29)
Accounts payable and accrued expenses	(49)
Income taxes	82
Pension and non-pension postretirement benefit contributions	(74)
Other assets and liabilities	(204)
Net cash flows provided by (used in) operating activities	797
Cash flows from investing activities
Capital expenditures	(995)
Purchases of investments	0
Changes in restricted cash	(1)
Proceeds from sale of long-lived assets	1
Other investing activities	4
Net cash flows provided by (used in) investing activities	(991)
Cash flows from financing activities
Changes in short-term borrowings	96
Proceeds from short-term borrowings with maturities greater than 90 days	0
Repayments on short-term borrowings with maturities greater than 90 days	(500)
Issuance of long-term debt	202
Retirement of long-term debt	(127)
Common stock issued for the Direct Stock Purchase and Dividend Reinvestment Plan and employee-related compensation	0
Change in Exelon intercompany money pool	1
Distributions to member	(267)
Contributions from member	758
Other financing activities	(2)
Net cash flows provided by (used in) financing activities	161
Increase (Decrease) in cash and cash equivalents	(33)
Cash and cash equivalents at beginning of period	170
Cash and cash equivalents at end of period	137	299
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	188	20
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	242	221
Deferred income taxes and amortization of investment tax credits	90	96
Other non-cash operating activities	8	168
Changes in assets and liabilities:
Accounts receivable	(43)	(105)
Receivables from and payables to affiliates, net	(10)	44
Inventories	(15)	3
Accounts payable and accrued expenses	(24)	7
Income taxes	80	139
Pension and non-pension postretirement benefit contributions	(69)	(6)
Other assets and liabilities	(99)	(83)
Net cash flows provided by (used in) operating activities	348	504
Cash flows from investing activities
Capital expenditures	(439)	(392)
Purchases of investments	0	(32)
Changes in restricted cash	(1)	(31)
Proceeds from sale of long-lived assets	1	12
Other investing activities	0	8
Net cash flows provided by (used in) investing activities	(439)	(435)
Cash flows from financing activities
Changes in short-term borrowings	(23)	(64)
Issuance of long-term debt	202	2
Retirement of long-term debt	(7)	(5)
Dividends paid on common stock	(133)	(92)
Contributions from parent	161	187
Other financing activities	(1)	0
Net cash flows provided by (used in) financing activities	199	28
Increase (Decrease) in cash and cash equivalents	108	97
Cash and cash equivalents at beginning of period	9	5
Cash and cash equivalents at end of period	117	102
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	107	(16)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	124	120
Deferred income taxes and amortization of investment tax credits	61	69
Other non-cash operating activities	6	99
Changes in assets and liabilities:
Accounts receivable	7	8
Receivables from and payables to affiliates, net	0	12
Inventories	(6)	0
Accounts payable and accrued expenses	0	(8)
Collateral (posted) received, net	0	1
Income taxes	33	52
Other assets and liabilities	(40)	(70)
Net cash flows provided by (used in) operating activities	292	267
Cash flows from investing activities
Capital expenditures	(294)	(260)
Proceeds from sale of long-lived assets	0	4
Other investing activities	1	2
Net cash flows provided by (used in) investing activities	(293)	(254)
Cash flows from financing activities
Changes in short-term borrowings	54	(88)
Retirement of long-term debt	(14)	0
Dividends paid on common stock	(82)	(39)
Contributions from parent	0	113
Net cash flows provided by (used in) financing activities	(42)	(14)
Increase (Decrease) in cash and cash equivalents	(43)	(1)
Cash and cash equivalents at beginning of period	46	5
Cash and cash equivalents at end of period	3	4
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	77	(50)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	113	130
Deferred income taxes and amortization of investment tax credits	28	14
Other non-cash operating activities	21	138
Changes in assets and liabilities:
Accounts receivable	(7)	(32)
Receivables from and payables to affiliates, net	(5)	9
Inventories	(7)	(1)
Accounts payable and accrued expenses	9	10
Income taxes	(9)	184
Other assets and liabilities	(62)	(87)
Net cash flows provided by (used in) operating activities	158	315
Cash flows from investing activities
Capital expenditures	(242)	(227)
Changes in restricted cash	1	(4)
Proceeds from sale of long-lived assets	0	2
Other investing activities	0	2
Net cash flows provided by (used in) investing activities	(241)	(227)
Cash flows from financing activities
Changes in short-term borrowings	65	(5)
Retirement of long-term debt	(25)	(35)
Dividends paid on common stock	(53)	(24)
Contributions from parent	0	139
Other financing activities	0	(1)
Net cash flows provided by (used in) financing activities	(13)	74
Increase (Decrease) in cash and cash equivalents	(96)	162
Cash and cash equivalents at beginning of period	101	3
Cash and cash equivalents at end of period	$ 5	$ 165

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Assets, Current [Abstract]
Cash and cash equivalents		$ 1,203	$ 635
Restricted cash and cash equivalents		320	253
Accounts receivable, net
Customer		3,854	4,158
Other		950	1,201
Mark-to-market derivative assets		699	917
Unamortized energy contract assets		81	88
Energy Related Inventory, Other Fossil Fuel		387	364
Inventories, net
Materials and supplies		1,281	1,274
Prepaid Taxes		1,250	1,250
Regulatory assets		1,264	1,342
Other		1,435	930
Total current assets		12,724	12,412
Property, plant and equipment, net		73,067	71,555
Deferred debits and other assets
Regulatory assets		10,238	10,046
Nuclear decommissioning trust funds		12,966	11,061
Investments		634	629
Goodwill		6,677	6,677
Mark-to-market derivative assets		426	492
Pledged assets for Zion Station decommissioning		57	113
Unamortized energy contract assets		407	447
Other		1,277	1,472
Total deferred debits and other assets		32,682	30,937
Total assets		118,473	114,904
Liabilities, Current [Abstract]
Short-term borrowings		710	1,267
Long-term debt due within one year		3,164	2,430
Accounts payable		3,132	3,441
Accrued expenses		3,080	3,460
Payables to affiliates		5	8
Unamortized energy contract liabilities		283	407
Regulatory liabilities		553	602
Mark-to-market derivative liabilities (current liabilities)		178	282
Energy Marketing Accounts Payable		261	428
Accounts Payable and Accrued Liabilities, Current		96	151
Other		933	981
Total current liabilities		12,395	13,457
Long-term debt		31,701	31,575
Long-term debt to financing trusts		389	641
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		19,250	18,138
Asset Retirement Obligations, Noncurrent		9,733	9,111
Pension obligations		4,055	4,248
Non-pension postretirement benefit obligations		1,977	1,848
Spent nuclear fuel obligation		1,142	1,024
Regulatory liabilities		4,549	4,187
Mark-to-market derivative liabilities (noncurrent liabilities)		410	392
Unamortized energy contract liabilities		656	830
Payable for Zion Station decommissioning		0	14
Other		1,899	1,827
Total deferred credits and other liabilities		43,671	41,619
Total liabilities	[1]	88,156	87,292
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		18,862	18,794
Treasury stock, at cost (2 shares and 35 shares at September 30, 2017 and December 31, 2016, respectively)		(123)	(2,327)
Retained earnings		11,950	12,030
Accumulated other comprehensive loss, net		(2,589)	(2,660)
Total shareholders’ equity		28,100	25,837
Member’s equity
Noncontrolling interests		2,217	1,775
Total equity		30,317	27,612
Total liabilities and shareholders’ equity		118,473	114,904
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities	[2]	268	502
Variable Interest Entity, Primary Beneficiary [Member]
Assets, Current [Abstract]
Cash and cash equivalents	[3]	130	150	[4]
Restricted cash and cash equivalents	[3]	85	59	[4]
Accounts receivable, net
Customer	[3]	139	371	[4]
Other	[3]	25	48	[4]
Mark-to-market derivative assets	[3]	0	31	[4]
Inventories, net
Materials and supplies	[3]	196	199	[4]
Other	[3]	56	50	[4]
Total current assets	[3]	631	908	[4]
Property, plant and equipment, net	[3]	6,213	5,415	[4]
Deferred debits and other assets
Nuclear decommissioning trust funds	[3]	2,415	2,185	[4]
Goodwill	[3]	0	47	[4]
Mark-to-market derivative assets	[3]	0	23	[4]
Other	[3]	261	315	[4]
Total assets	[3]	9,520	8,893	[4]
Liabilities, Current [Abstract]
Long-term debt due within one year	[3]	182	181	[4]
Accounts payable	[3]	104	269	[4]
Accrued expenses	[3]	90	119	[4]
Unamortized energy contract liabilities	[3]	17	15	[4]
Mark-to-market derivative liabilities (current liabilities)	[3]	0	60	[4]
Other	[3]	11	30	[4]
Total current liabilities	[3]	404	674	[4]
Long-term debt	[3]	1,172	641	[4]
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent	[3]	2,009	1,904	[4]
Pension obligations	[3],[5]	0	9	[4]
Unamortized energy contract liabilities	[3]	9	22	[4]
Other	[3]	94	106	[4]
Total liabilities	[3]	3,688	3,356	[4]
Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		9,520	8,893
Deferred credits and other liabilities
Total liabilities		3,688	3,356
Exelon Generation Co L L C [Member]
Assets, Current [Abstract]
Cash and cash equivalents		360	290
Restricted cash and cash equivalents		186	158
Accounts receivable, net
Customer		2,339	2,433
Other		275	558
Mark-to-market derivative assets		699	917
Receivables from affiliates		127	156
Unamortized energy contract assets		81	88
Energy Related Inventory, Other Fossil Fuel		298	292
Inventories, net
Materials and supplies		917	935
Other		1,157	701
Total current assets		6,439	6,528
Property, plant and equipment, net		24,793	25,585
Deferred debits and other assets
Nuclear decommissioning trust funds		12,966	11,061
Investments		429	418
Goodwill		47	47
Mark-to-market derivative assets		416	476
Prepaid pension asset		1,535	1,595
Pledged assets for Zion Station decommissioning		57	113
Unamortized energy contract assets		406	447
Deferred Tax Assets, Net, Noncurrent		8	16
Other		648	688
Total deferred debits and other assets		16,512	14,861
Total assets		47,744	46,974
Liabilities, Current [Abstract]
Short-term borrowings		92	699
Long-term debt due within one year		1,659	1,117
Accounts payable		1,492	1,610
Accrued expenses		797	989
Payables to affiliates		136	137
Unamortized energy contract liabilities		52	72
Other Short-term Borrowings		146	55
Mark-to-market derivative liabilities (current liabilities)		158	263
Energy Marketing Accounts Payable		261	428
Other		266	313
Total current liabilities		5,059	5,683
Long-term debt		6,956	7,202
Long-term debt to affiliate		913	922
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		5,596	5,585
Asset Retirement Obligations, Noncurrent		9,548	8,922
Non-pension postretirement benefit obligations		919	930
Spent nuclear fuel obligation		1,142	1,024
Due to Affiliate, Noncurrent		2,972	2,608
Mark-to-market derivative liabilities (noncurrent liabilities)		153	153
Unamortized energy contract liabilities		57	80
Payable for Zion Station decommissioning		0	14
Other		632	595
Total deferred credits and other liabilities		21,019	19,911
Total liabilities	[6]	33,947	33,718
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Retained earnings		2,260	2,275
Accumulated other comprehensive loss, net		(36)	(54)
Member’s equity
Members' Capital		9,357	9,261
Total member's equity		11,581	11,482
Noncontrolling interests		2,216	1,774
Total equity		13,797	13,256
Total liabilities and shareholders’ equity		47,744	46,974
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets, Current [Abstract]
Cash and cash equivalents		130	150
Restricted cash and cash equivalents		76	27
Accounts receivable, net
Customer		139	371
Other		25	48
Mark-to-market derivative assets		0	31
Inventories, net
Materials and supplies		196	199
Other		52	44
Total current assets		618	870
Property, plant and equipment, net		6,213	5,415
Deferred debits and other assets
Nuclear decommissioning trust funds		2,415	2,185
Goodwill		0	47
Mark-to-market derivative assets		0	23
Other		231	277
Total assets		9,477	8,817
Liabilities, Current [Abstract]
Long-term debt due within one year		146	99
Accounts payable		104	269
Accrued expenses		89	116
Unamortized energy contract liabilities		17	15
Mark-to-market derivative liabilities (current liabilities)		0	60
Other		11	30
Total current liabilities		367	589
Long-term debt		1,097	540
Deferred credits and other liabilities
Asset Retirement Obligations, Noncurrent		2,009	1,904
Pension obligations	[5]	0	9
Unamortized energy contract liabilities		9	22
Other		94	106
Total liabilities		3,576	3,170
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		9,477	8,817
Deferred credits and other liabilities
Total liabilities		3,576	3,170
Commonwealth Edison Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		257	56
Restricted cash and cash equivalents		52	2
Accounts receivable, net
Customer		496	528
Other		172	218
Receivables from affiliates		18	356
Inventories, net
Inventories, net		152	159
Regulatory assets		187	190
Other		67	45
Total current assets		1,401	1,554
Property, plant and equipment, net		20,353	19,335
Deferred debits and other assets
Regulatory assets		1,387	977
Investments		6	6
Goodwill		2,625	2,625
Receivable from affiliate		2,438	2,170
Prepaid pension asset		1,236	1,343
Other		203	325
Total deferred debits and other assets		7,895	7,446
Total assets		29,649	28,335
Liabilities, Current [Abstract]
Long-term debt due within one year		840	425
Accounts payable		579	645
Accrued expenses		305	1,250
Payables to affiliates		51	65
Customer deposits		114	121
Regulatory liabilities		249	329
Mark-to-market derivative liabilities (current liabilities)		20	19
Other		88	84
Total current liabilities		2,246	2,938
Long-term debt		6,760	6,608
Long-term debt to financing trusts		205	205
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		6,091	5,364
Asset Retirement Obligations, Noncurrent		110	119
Non-pension postretirement benefit obligations		224	239
Regulatory liabilities		3,735	3,369
Mark-to-market derivative liabilities (noncurrent liabilities)		257	239
Other		577	529
Total deferred credits and other liabilities		10,994	9,859
Total liabilities		20,205	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		6,738	6,150
Retained Earnings, Appropriated		2,757	2,626
Total shareholders’ equity		9,444	8,725
Member’s equity
Total liabilities and shareholders’ equity		29,649	28,335
PECO Energy Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		330	63
Restricted cash and cash equivalents		4	4
Accounts receivable, net
Customer		240	306
Other		125	131
Receivables from affiliates		0	4
Receivable from Exelon intercompany pool		57	131
Energy Related Inventory, Other Fossil Fuel		36	35
Inventories, net
Materials and supplies		31	27
Prepaid Taxes		41	9
Regulatory assets		36	29
Other		16	18
Total current assets		916	757
Property, plant and equipment, net		7,875	7,565
Deferred debits and other assets
Regulatory assets		1,773	1,681
Investments		24	25
Receivable from affiliate		533	438
Prepaid pension asset		347	345
Other		12	20
Total deferred debits and other assets		2,689	2,509
Total assets		11,480	10,831
Liabilities, Current [Abstract]
Long-term debt due within one year		500	0
Accounts payable		285	342
Accrued expenses		132	104
Payables to affiliates		48	63
Customer deposits		64	61
Regulatory liabilities		159	127
Other		28	30
Total current liabilities		1,216	727
Long-term debt		2,402	2,580
Long-term debt to financing trusts		184	184
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		3,170	3,006
Asset Retirement Obligations, Noncurrent		27	28
Non-pension postretirement benefit obligations		289	289
Regulatory liabilities		560	517
Other		90	85
Total deferred credits and other liabilities		4,136	3,925
Total liabilities		7,938	7,416
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		2,489	2,473
Retained earnings		1,052	941
Accumulated other comprehensive loss, net		1	1
Total shareholders’ equity		3,542	3,415
Member’s equity
Total liabilities and shareholders’ equity		11,480	10,831
Baltimore Gas and Electric Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		29	23
Restricted cash and cash equivalents		1	24
Accounts receivable, net
Customer		288	395
Other		86	102
Inventories, net
Energy Related Inventory, Natural Gas in Storage		46	30
Materials and supplies		40	38
Prepaid Taxes		0	15
Regulatory assets		208	208
Other		4	7
Total current assets		702	842
Property, plant and equipment, net		7,418	7,040
Deferred debits and other assets
Regulatory assets		497	504
Investments		5	12
Prepaid pension asset		297	297
Other		4	9
Total deferred debits and other assets		803	822
Total assets	[7]	8,923	8,704
Liabilities, Current [Abstract]
Short-term borrowings		0	45
Long-term debt due within one year		0	41
Accounts payable		218	205
Accrued expenses		147	175
Payables to affiliates		42	55
Customer deposits		114	110
Regulatory liabilities		63	50
Other		28	26
Total current liabilities		612	707
Long-term debt		2,577	2,281
Long-term debt to financing trusts		0	252
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		2,366	2,219
Asset Retirement Obligations, Noncurrent		23	21
Non-pension postretirement benefit obligations		201	205
Regulatory liabilities		84	110
Other		52	61
Total deferred credits and other liabilities		2,726	2,616
Total liabilities	[7]	5,915	5,856
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		1,498	1,421
Retained earnings		1,510	1,427
Total shareholders’ equity		3,008	2,848
Member’s equity
Total liabilities and shareholders’ equity		8,923	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		137	170
Restricted cash and cash equivalents		43	43
Accounts receivable, net
Customer		490	496
Other		209	283
Mark-to-market derivative assets		0	0
Inventories, net
Energy Related Inventory, Natural Gas in Storage		9	6
Materials and supplies		141	116
Regulatory assets		568	653
Other		59	71
Total current assets		1,656	1,838
Property, plant and equipment, net		12,219	11,598
Deferred debits and other assets
Regulatory assets		2,692	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		510	509
Deferred Tax Assets, Net, Noncurrent		6	6
Other		77	81
Total deferred debits and other assets		7,426	7,589
Total assets	[8]	21,301	21,025
Liabilities, Current [Abstract]
Short-term borrowings		118	522
Long-term debt due within one year		159	253
Accounts payable		397	458
Accrued expenses		294	272
Payables to affiliates		79	94
Unamortized energy contract liabilities		231	335
Customer deposits		119	123
Regulatory liabilities		65	79
Other Short-term Borrowings		1
Mark-to-market derivative liabilities (current liabilities)		0	0
Payables to Customers		53	101
Other		41	47
Total current liabilities		1,557	2,284
Long-term debt		5,771	5,645
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		4,003	3,775
Asset Retirement Obligations, Noncurrent		17	14
Non-pension postretirement benefit obligations		128	134
Regulatory liabilities		146	158
Mark-to-market derivative liabilities (noncurrent liabilities)		0	0
Unamortized energy contract liabilities		599	750
Other		214	249
Total deferred credits and other liabilities		5,107	5,080
Total liabilities		12,435	13,009
Stockholders' Equity Attributable to Parent [Abstract]
Retained earnings		31	(61)
Member’s equity
Members' Capital		8,835	8,077
Total member's equity		8,866	8,016
Total equity		8,866	8,016
Total liabilities and shareholders’ equity	[8]	21,301	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]	9	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]	13	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]	30	35
Total assets	[3]	43	49
Liabilities, Current [Abstract]
Long-term debt due within one year	[3]	36	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]	37	42
Long-term debt	[3]	75	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]	112	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		112	143
Potomac Electric Power Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		117	9
Restricted cash and cash equivalents		34	33
Accounts receivable, net
Customer		265	235
Other		92	150
Inventories, net
Materials and supplies		78	63
Regulatory assets		181	162
Other		10	32
Total current assets		777	684
Property, plant and equipment, net		5,866	5,571
Deferred debits and other assets
Regulatory assets		699	690
Investments		102	102
Prepaid pension asset		327	282
Other		4	6
Total deferred debits and other assets		1,132	1,080
Total assets		7,775	7,335
Liabilities, Current [Abstract]
Short-term borrowings		0	23
Long-term debt due within one year		19	16
Accounts payable		168	209
Accrued expenses		153	113
Payables to affiliates		64	74
Customer deposits		53	53
Regulatory liabilities		5	11
Payables to Customers		42	68
Other		20	29
Total current liabilities		524	596
Long-term debt		2,527	2,333
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		2,024	1,910
Non-pension postretirement benefit obligations		37	43
Regulatory liabilities		21	20
Other		126	133
Total deferred credits and other liabilities		2,208	2,106
Total liabilities		5,259	5,035
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		1,470	1,309
Retained earnings		1,046	991
Total shareholders’ equity		2,516	2,300
Member’s equity
Total liabilities and shareholders’ equity		7,775	7,335
Delmarva Power and Light Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		3	46
Accounts receivable, net
Customer		118	136
Other		36	63
Receivables from affiliates		0	3
Inventories, net
Energy Related Inventory, Natural Gas in Storage		9	7
Materials and supplies		35	32
Regulatory assets		69	59
Other		16	24
Total current assets		286	370
Property, plant and equipment, net		3,480	3,273
Deferred debits and other assets
Regulatory assets		300	289
Goodwill		8	8
Prepaid pension asset		197	206
Other		5	7
Total deferred debits and other assets		510	510
Total assets		4,276	4,153
Liabilities, Current [Abstract]
Short-term borrowings		54	0
Long-term debt due within one year		109	119
Accounts payable		95	88
Accrued expenses		52	36
Payables to affiliates		35	38
Customer deposits		35	36
Regulatory liabilities		42	43
Payables to Customers		3	13
Other		7	8
Total current liabilities		432	381
Long-term debt		1,217	1,221
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		1,125	1,056
Non-pension postretirement benefit obligations		17	19
Regulatory liabilities		86	97
Other		48	53
Total deferred credits and other liabilities		1,276	1,225
Total liabilities		2,925	2,827
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		764	764
Retained earnings		587	562
Total shareholders’ equity		1,351	1,326
Member’s equity
Total liabilities and shareholders’ equity		4,276	4,153
Atlantic City Electric Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		5	101
Restricted cash and cash equivalents		9	9
Accounts receivable, net
Customer		107	125
Other		54	44
Inventories, net
Materials and supplies		29	22
Prepaid Taxes		15	0
Regulatory assets		87	96
Other		3	2
Total current assets		309	399
Property, plant and equipment, net		2,662	2,521
Deferred debits and other assets
Regulatory assets		417	405
Notes, Loans and Financing Receivable, Gross, Noncurrent		4	4
Prepaid pension asset		76	84
Other		42	44
Total deferred debits and other assets		539	537
Total assets	[9]	3,510	3,457
Liabilities, Current [Abstract]
Short-term borrowings		65	0
Long-term debt due within one year		32	35
Accounts payable		122	132
Accrued expenses		39	38
Payables to affiliates		24	29
Customer deposits		31	33
Regulatory liabilities		18	25
Payables to Customers		8	20
Other		6	8
Total current liabilities		345	320
Long-term debt		1,098	1,120
Deferred credits and other liabilities
Deferred Income Taxes and Other Tax Liabilities, Noncurrent		951	917
Non-pension postretirement benefit obligations		33	34
Regulatory liabilities		0	0
Other		25	32
Total deferred credits and other liabilities		1,009	983
Total liabilities		2,452	2,423
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		912	912
Retained earnings		146	122
Total shareholders’ equity		1,058	1,034
Member’s equity
Total liabilities and shareholders’ equity	[9]	3,510	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		9	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		9	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		22	23
Total assets		31	32
Liabilities, Current [Abstract]
Long-term debt due within one year		32	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		33	37
Long-term debt		67	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		100	126
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Member’s equity
Noncontrolling Interest in Variable Interest Entity		31	32
Variable Interest Entity, Nonconsolidated, Carrying Amount, Liabilities		$ 100	$ 126
[1]	Exelon’s consolidated assets include $9,520 million and $8,893 million at September 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 $3,688 million and $3,356 million at September 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 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 14 - Retirement Benefits for additional details.
[6]	Generation’s consolidated assets include $9,477 million and $8,817 million at September 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 $3,576 million and $3,170 million at September 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 no longer has interests in any VIEs as of September 30, 2017. See Note 3 - Variable Interest Entities.
[8]	PHI’s consolidated total assets include $43 million and $49 million at September 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 $112 million and $143 million at September 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 $31 million and $32 million at September 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 $100 million and $126 million at September 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	Sep. 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	960,852,473	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]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]	Exelon Generation Co L L C [Member]Membership 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]Undistributed Earnings [Member]	Pepco Holdings LLC [Member]Membership Interest [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		$ 956							$ 556						$ 297					$ 346					$ 191						$ 20			$ (16)			$ (50)
Other Comprehensive Income (Loss), Net of Tax		$ 96				101	[1]		2		7	[1]											0	[1]
Ending balance at Sep. 30, 2016	[1]					(2,523)					(56)												1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from Contributions from Affiliates									142
Net income | Successor [Member]																												$ (91)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																												0
Ending balance at Sep. 30, 2016	[1]					(2,523)					(56)												1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from Contributions from Affiliates | Successor [Member]																												1,088
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	$ (61)	$ 8,077
Beginning Balance at Dec. 31, 2016									13,256	$ 2,275	(54)		$ 1,774	$ 9,261
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income | Successor [Member]																												359	359
Net income		1,911	0	0	1,899	0		12	491	479	0		12		447			447		327		327			231		231				188	0	188	107		107	77		77
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									33					33
Stock Issued During Period, Shares, Share-based Compensation, Gross		2,911
Stock Issued During Period, Value, Share-based Compensation, Gross		$ 43	43	0	0	0		0
Stock Issued During Period, Shares, Employee Stock Purchase Plans		996
Stock Issued During Period, Value, Employee Stock Purchase Plan		$ 61	61	0	0	0		0
Noncontrolling Interest, Period Increase (Decrease)		(11)						(11)	(11)				(11)
Noncontrolling Interest, Increase from Sale of Parent Equity Interest		407	(36)					443	407				443	(36)
Income Tax Effects Allocated Directly to Equity, Other | Successor [Member]																												7		7
Income Tax Effects Allocated Directly to Equity, Other									99					99						(16)
Common stock dividends		(925)	0	0	(925)	0		0												(216)	0	(216)	0		(148)		(148)				(133)	0	(133)	(82)		(82)	(53)		(53)
Other Comprehensive Income (Loss), Net of Tax | Successor [Member]																												0
Other Comprehensive Income (Loss), Net of Tax		69	0	0	0	71	[1]	(2)	16	0	18	[1]	(2)										0	[1]
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared | Successor [Member]																												(267)	(267)
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Declared									(494)	(494)
Employee stock purchase plan issuances		$ 61	61	0	0	0		0
Dividends															(316)				(316)
Adjustments to Additional Paid in Capital, Other | Successor [Member]																												751		751
Adjustments to Additional Paid in Capital, Other															567		567								77	77	0				161	161
Ending Balance (in shares) at Sep. 30, 2017		962,685
Ending balance at Sep. 30, 2017		$ 30,317	$ 18,862	$ (123)	$ 11,950	$ (2,589)	[1]	$ 2,217			(36)	[1]											1	[1]
Ending Balance at Sep. 30, 2017		$ 28,100													9,444	$ 1,588	6,738	(1,639)	2,757	$ 3,542	$ 2,489	$ 1,052	$ 1		$ 3,008	$ 1,498	$ 1,510				$ 2,516	$ 1,470	$ 1,046	$ 1,351	$ 764	$ 587	$ 1,058	$ 912	$ 146
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from Contributions from Affiliates | Successor [Member]																												758
Proceeds from Contributions from Affiliates									102
Ending Balance (Successor [Member]) at Sep. 30, 2017																												$ 8,866	$ 31	$ 8,835
Ending Balance at Sep. 30, 2017									$ 13,797	$ 2,260	$ (36)		$ 2,216	$ 9,357
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained Earnings, Appropriated															(2,757)			$ (447)	$ (447)
Other Additional Capital															$ 21		$ 21
[1]	All amounts are net of tax and noncontrolling interest. Amounts in parenthesis represent a decrease in AOCI.

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation (Exelon, Generation, ComEd, PECO and BGE)	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. The accompanying consolidated financial statements as of September 30, 2017 and 2016 and for the three and nine 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.

New Accounting Standards (All R

New Accounting Standards (All Registrants)	9 Months Ended
	Sep. 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. 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 have assessed the revenue recognition standard and are executing a detailed implementation plan in preparation for adoption on January 1, 2018. The Registrants have also actively participated 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. In coordination with the Industry Task Force, the Registrants have reached conclusions on the following key accounting issues: • 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 concurrent with the delivery of electricity or natural gas, consistent with current practice; • Consistent with current industry practice, revenues recognized from sales of bundled energy commodities (i.e., contracts involving the delivery of multiple energy commodities such as electricity, capacity, ancillary services, etc.) are generally expected to be recognized upon delivery to the customer in an amount based on the invoice price given that it corresponds directly with the value of the commodities transferred to the customer; and • Contributions in aid of construction are 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 have also completed the following key activities in their implementation plan: • Evaluated existing contracts and revenue streams for potential changes in revenue recognition under the new guidance. Based on these assessments, the Registrants have identified the following items that will be accounted for differently under the new revenue guidance as compared to current guidance: • Costs to acquire certain contracts (e.g., sales commissions associated with retail power contracts) will be deferred and amortized ratably over the term of the contract rather than being expensed as incurred; and • Variable consideration within certain contracts (e.g., performance bonuses) will be estimated and recognized as revenue over the term of the contract rather than being recognized when realized Notwithstanding these identified changes, Exelon does not expect the new guidance will have a material impact on the amount and timing of revenue recognition; • Currently expect to apply the new guidance using the full retrospective method; and • Generation expects to disclose disaggregated revenue by operating segment and further differentiation by major products (i.e., electric power and gas) and the Utility Registrants expect to disclose disaggregated revenue by major customer class (i.e., residential and commercial & industrial) separately for electric and gas in the Combined Notes to Consolidated Financial Statements. 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 report the service cost and other non-service cost components of net periodic pension cost and net periodic OPEB cost (together, net benefit cost) separately. Under current GAAP, net benefit cost is recorded as part of income from operations and the components are disclosed in the Retirement Benefits footnote. Service cost will be presented as part of income from operations and the other non-service cost 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). Generation, ComEd, PECO, BGE, BSC, PHI, Pepco, DPL, ACE and PHISCO participate in Exelon’s single employer pension and OPEB plans and apply multi-employer accounting. Multi-employer accounting is not impacted by this standard, so Exelon's subsidiary financial statements will not change. On Exelon’s consolidated financial statements, non-service cost components of pension and OPEB cost capitalizable under a regulatory framework will be reported as regulatory assets (currently, they are capitalizable under pension and OPEB accounting guidance and reported as PP&E). These regulatory assets will be amortized outside of operating income. The standard is effective January 1, 2018 and requires retrospective application for the presentation of the service cost component and the other non-service cost 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. Derivatives and Hedging (Issued September 2017): Allows more financial and nonfinancial hedging strategies to be eligible for hedge accounting. The amendments are intended to more closely align hedge accounting with companies’ risk management strategies, simplify the application of hedge accounting, and increase transparency as to the scope and results of hedging programs. There are also amendments related to effectiveness testing and disclosure requirements. The guidance is effective January 1, 2019 and early adoption is permitted with a modified retrospective transition approach. The Registrants are currently assessing this standard but do not currently expect a significant impact given the limited activity for which the Registrants elect hedge accounting and because the Registrants do not anticipate increasing their use of hedge accounting as a result of this standard. 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 September 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 (or dispositions) should be accounted for as acquisitions/dispositions of assets or as acquisitions/dispositions of businesses. If substantially all the fair value of the assets acquired/disposed of 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/disposed of 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 will likely result in more acquisitions being accounted for as asset acquisitions. The standard is effective January 1, 2018, with early adoption permitted, and must be applied on a prospective basis. 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 requires a modified retrospective transition approach 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). The Registrants 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 do not expect that this guidance will have a significant impact 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 requires a modified retrospective transition approach with a cumulative effect adjustment to retained earnings for initial application of the guidance at the date of adoption. The Registrants will not early adopt this standard. The Registrants do not expect that this guidance will have a significant impact on the Registrants' Consolidated Balance Sheets, Consolidated Statements of Operations and Comprehensive Income, and Consolidated Statements of Cash Flows.
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 original 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 September 30, 2017 , Generation has outstanding commitments to invest in fixed income, middle market lending, private equity and real estate investments of approximately $75 million , $285 million , $240 million , and $95 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 September 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 September 30, 2017 , there were no significant concentrations (generally defined as greater than 10 percent) of risk in Generation's NDT assets. See Note 13 — 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 10 - 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.

Variable Interest Entities (All

Variable Interest Entities (All Registrants)	9 Months Ended
	Sep. 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 September 30, 2017 and December 31, 2016 , Exelon, Generation, BGE, PHI and ACE collectively consolidated six and nine VIEs or VIE groups, respectively, for which the applicable Registrant was the primary beneficiary ( see Consolidated Variable Interest Entities below) . As of September 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 In July 2017, Generation entered into an arrangement to sell a 49% interest in ExGen Renewables Partners, LLC (the Renewable JV) to an outside investor for $400 million of cash plus immaterial working capital and other customary post-closing adjustments. The Renewable JV meets the definition of a VIE because the Renewable JV has a similar structure to a limited partnership and the limited partners do not have kick out rights with respect to the general partner. Additionally, under the VIE guidance Generation is the primary beneficiary because Generation maintains the controlling financial interest; therefore, Generation will continue to consolidate the Renewable JV. Generation owned 90% of a biomass fueled, combined heat and power company. In the second quarter of 2015, the entity was deemed to be a VIE because the entity required additional subordinated financial support in the form of a parental guarantee provided by Generation for up to $275 million in support of the payment obligations related to the Engineering, Procurement and Construction (EPC) contract (see Note 14 - Debt and Credit Agreements for additional details on Albany Green Energy, LLC). During the third quarter of 2017, the ownership of the entity increased to 99% , all payment obligations related to the EPC contract were satisfied, and the parental guarantee provided by Generation was terminated. As a result, the entity is now sufficiently capitalized and no longer meets the definition of a VIE. The entity was previously disclosed in “a group of companies formed by Generation to build, own and operate other generating facilities” as of December 31, 2016 . However, the biomass facility will continue to be consolidated by Generation under the voting interest model. 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. In the second quarter of 2017 the rate stabilization bonds were fully redeemed and BGE remitted its final payment to BondCo. During the nine months ended September 30, 2017 , BGE remitted $22 million to BondCo. During the three and nine months ended September 30, 2016 , BGE remitted $27 million and $64 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. During 2009, Constellation formed a retail gas group to enter into a collateralized gas supply agreement with a third-party gas supplier. 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 met the definition of a VIE and was removed from the list of consolidated VIEs noted below. However, the retail gas group continues to be consolidated by Generation under the voting interest model. As of September 30, 2017 , Exelon's and Generation's consolidated VIEs consist of: • Renewable energy project companies formed by Generation to build, own and operate renewable power facilities, which were previously separated into two separate VIE groups for solar project limited liability companies and wind project companies as of December 31, 2016, • Constellation EG, LLC (a company that operates back-up generation for a third-party), which was previously included in a group of companies formed by Generation to build, own and operate other generating facilities as of December 31, 2016, • 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 As of September 30, 2017 , Exelon's, PHI's and ACE's consolidated VIE consists of: • 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 September 30, 2017 and December 31, 2016 , ComEd, PECO, Pepco and DPL did not have any material consolidated VIEs. As of September 30, 2017 and December 31, 2016 , Exelon and Generation provided the following support to their respective consolidated VIEs: • Generation provides operating and capital funding to the renewable energy project companies and there is limited recourse to Generation related to certain renewable energy project companies. • Generation provides operating and capital funding to Constellation EG, LLC. • Generation provides approximately $31 million in credit support for the retail power and gas companies for which Generation is the sole supplier of energy. • Exelon and Generation, 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 September 30, 2017 , the remaining obligation is $328 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 18 — 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 18 — 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. As of September 30, 2017 and December 31, 2016 , Exelon, PHI and ACE provided the following support to their respective consolidated VIE: • 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 nine months ended September 30, 2017 , ACE transferred $11 million and $39 million to ATF, respectively. During the three and nine months ended September 30, 2016 , ACE transferred $20 million and $47 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 September 30, 2017 and December 31, 2016 are as follows: September 30, 2017 December 31, 2016 Successor Successor Exelon (a) Generation PHI (a) ACE Exelon (a)(b) Generation BGE PHI (a) ACE Current assets $ 657 $ 644 $ 13 $ 9 $ 954 $ 916 $ 23 $ 14 $ 9 Noncurrent assets 9,252 9,222 30 22 8,563 8,525 3 35 23 Total assets $ 9,909 $ 9,866 $ 43 $ 31 $ 9,517 $ 9,441 $ 26 $ 49 $ 32 Current liabilities $ 404 $ 367 $ 37 $ 33 $ 885 $ 802 $ 42 $ 42 $ 37 Noncurrent liabilities 3,290 3,215 75 67 2,713 2,612 — 101 89 Total liabilities $ 3,694 $ 3,582 $ 112 $ 100 $ 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 September 30, 2017 and December 31, 2016 , these assets and liabilities primarily consisted of the following: September 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 $ 130 $ 130 $ — $ — $ 150 $ 150 $ — $ — $ — Restricted cash 85 76 9 9 59 27 23 9 9 Accounts receivable, net Customer 139 139 — — 371 371 — — — Other 25 25 — — 48 48 — — — Mark-to-market derivatives assets — — — — 31 31 — — — Inventory Materials and supplies 196 196 — — 199 199 — — — Other current assets 56 52 4 — 50 44 — 5 — Total current assets 631 618 13 9 908 870 23 14 9 Property, plant and equipment, net 6,213 6,213 — — 5,415 5,415 — — — Nuclear decommissioning trust funds 2,415 2,415 — — 2,185 2,185 — — — Goodwill — — — — 47 47 — — — Mark-to-market derivative assets — — — — 23 23 — — — Other noncurrent assets 261 231 30 22 315 277 3 35 23 Total noncurrent assets 8,889 8,859 30 22 7,985 7,947 3 35 23 Total assets $ 9,520 $ 9,477 $ 43 $ 31 $ 8,893 $ 8,817 $ 26 $ 49 $ 32 Long-term debt due within one year $ 182 $ 146 $ 36 $ 32 $ 181 $ 99 $ 41 $ 40 $ 35 Accounts payable 104 104 — — 269 269 — — — Accrued expenses 90 89 1 1 119 116 1 2 2 Mark-to-market derivative liabilities — — — — 60 60 — — — Unamortized energy contract liabilities 17 17 — — 15 15 — — — Other current liabilities 11 11 — — 30 30 — — — Total current liabilities 404 367 37 33 674 589 42 42 37 Long-term debt 1,172 1,097 75 67 641 540 — 101 89 Asset retirement obligations 2,009 2,009 — — 1,904 1,904 — — — Pension obligation (c) — — — — 9 9 — — — Unamortized energy contract liabilities 9 9 — — 22 22 — — — Other noncurrent liabilities 94 94 — — 106 106 — — — Total noncurrent liabilities 3,284 3,209 75 67 2,682 2,581 — 101 89 Total liabilities $ 3,688 $ 3,576 $ 112 $ 100 $ 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 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 14 - 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. As of September 30, 2017 , Exelon's and Generation's 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 September 30, 2017 and December 31, 2016 , ComEd, PECO, BGE, PHI, Pepco, ACE, and DPL did not have any material unconsolidated VIEs. As of September 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 $17 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 $17 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: September 30, 2017 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 635 $ 519 $ 1,154 Total liabilities (a) 39 229 268 Exelon's ownership interest in VIE (a) — 259 259 Other ownership interests in VIE (a) 596 31 627 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 259 259 Contract intangible asset 9 — 9 Debt and payment guarantees — — — Net assets pledged for Zion Station decommissioning (b) 4 — 4 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 $57 million and $113 million as of September 30, 2017 and December 31, 2016 , respectively; offset by payables to ZionSolutions LLC of $53 million and $104 million as of September 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 13 - 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. BGE The financing trust of BGE, BGE Capital Trust II, was created in 2003 for the purpose of issuing mandatorily redeemable trust preferred securities. In the third quarter of 2017, BGE redeemed the securities pursuant to the optional redemption provisions of the Indenture, under which the subordinated debt securities were issued, and dissolved BGE Capital Trust II. Prior to dissolution the BGE Capital Trust II was not consolidated in Exelon's or BGE's financial statements. BGE concluded it did not have a significant variable interest in BGE Capital Trust II as BGE financed its equity interest in the financing trust through the issuance of subordinated debt and, therefore, had no equity at risk. See Note 14 - Debt and Credit Agreements of the Exelon 2016 Form 10-K for additional information.

Mergers, Acquisitions, and Disp

Mergers, Acquisitions, and Dispositions	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Mergers, Acquisitions and Dispositions	Mergers, Acquisitions and Dispositions (Exelon, Generation, PHI, Pepco and DPL) 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 $289 million , which consisted of a cash purchase price of $110 million and a net cost reimbursement to and on behalf of Entergy of $179 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 September 30, 2017 , Generation had remitted purchase price consideration of $289 million (including $235 million of cash and $54 million of nuclear fuel) to and on behalf of Entergy. 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 in the first quarter of 2017 to determine the fair value of the FitzPatrick assets acquired and liabilities assumed were 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. During the third quarter of 2017, certain modifications were made to the initial preliminary valuation amounts for acquired property, plant and equipment, the decommissioning ARO, pension and OPEB obligations and related deferred tax liabilities, resulting in a $3 million net increase in assets acquired and liabilities assumed. Additionally, in the third quarter a purchase price settlement payment of $4 million was received from Entergy. Consequently, Exelon and Generation recorded an additional after-tax bargain purchase gain of $7 million for the three months ended September 30, 2017 . For the nine months ended September 30, 2017 , the after-tax bargain purchase gain of $233 million is included within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income and primarily reflects differences in strategies between Generation and Entergy for the intended use and ultimate decommissioning of the plant. There are no further adjustments expected to be made to the allocation of the purchase price. See Note 13 - Nuclear Decommissioning and Note 14 - Retirement Benefits for additional information regarding the FitzPatrick decommissioning ARO and pension and OPEB updates. 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 September 30, 2017: Cash paid for purchase price $ 110 Cash paid for net cost reimbursement 125 Nuclear fuel transfer 54 Total consideration transferred $ 289 Identifiable assets acquired and liabilities assumed Current assets $ 60 Property, plant and equipment 298 Nuclear decommissioning trust funds 807 Other assets (a) 114 Total assets $ 1,279 Current liabilities $ 6 Nuclear decommissioning ARO 444 Pension and OPEB obligations 33 Deferred income taxes 149 Spent nuclear fuel obligation 110 Other liabilities 15 Total liabilities $ 757 Total net identifiable assets, at fair value $ 522 Bargain purchase gain (after-tax) $ 233 _________ (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. For the three and nine months ended September 30, 2017 , Exelon and Generation incurred $6 million and $53 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. Acquisition of ConEdison Solutions (Exelon and Generation) On September 1, 2016, Generation acquired the competitive retail electricity and natural gas business of Consolidated Edison Solutions, Inc. (ConEdison Solutions), a subsidiary of Consolidated Edison, Inc. for a purchase price of $257 million including net working capital of $204 million . The renewable energy, sustainable services and energy efficiency businesses of ConEdison Solutions are excluded from the transaction. The fair values of ConEdison Solutions' assets and liabilities were determined based on significant estimates and assumptions that are judgmental in nature, including projected future cash flows (including timing), discount rates reflecting risk inherent in the future cash flows and future power and fuel market prices. The purchase price equaled the estimated fair value of the net assets acquired and the liabilities assumed and, therefore, no goodwill or bargain purchase was recorded as of the acquisition date. The purchase price allocation is now final. The following table summarizes the final acquisition-date fair value of the consideration transferred and the assets and liabilities assumed for the ConEdison Solutions acquisition by Generation: Total consideration transferred $ 257 Identifiable assets acquired and liabilities assumed Working capital assets $ 204 Property, plant and equipment 2 Mark-to-market derivative assets 6 Unamortized energy contract assets 100 Customer relationships 9 Other assets 1 Total assets $ 322 Mark-to-market derivative liabilities $ 65 Total liabilities $ 65 Total net identifiable assets, at fair value $ 257 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, 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 reflected 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. All briefs have been filed and oral arguments were presented to the court on October 10, 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 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 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 September 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 Nine Months Ended 2017 2016 2017 2016 Operating revenues $ 1,347 $ 1,437 $ 3,679 $ 2,656 Net income (loss) 176 169 382 (92 ) For the three and nine months ended September 30, 2017 and 2016 , the Registrants have recognized costs to achieve the PHI acquisition as follows: Three Months Ended Nine Months Ended Acquisition, Integration and Financing Costs (a) 2017 2016 2017 2016 Exelon $ (8 ) $ 20 $ 10 $ 123 Generation 5 9 18 29 ComEd (b) — — 1 (6 ) PECO 1 1 3 3 BGE (c) 1 1 3 (3 ) Pepco (d) (8 ) 3 (6 ) 26 DPL (e) 1 2 (6 ) 18 ACE (f) (8 ) 2 (6 ) 17 Successor Predecessor Acquisition, Integration and Financing Costs (a) Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 Nine Months Ended September 30, 2017 March 24, 2016 to September 30, 2016 January 1, 2016 to March 23, 2016 PHI (g) $ (15 ) $ 7 $ (17 ) $ 63 $ 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) For the nine months ended September 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. (c) For the nine months ended September 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. (d) For the three and nine months ended September 30, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. For the nine months ended September 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $10 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. (e) For the nine months ended September 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 nine months ended September 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. (f) For the three and nine months ended September 30, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at ACE that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. (g) For the three and nine months ended September 30, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $16 million and $24 million , respectively, incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. For the Successor period March 24, 2016 to September 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $13 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 Nine Months Ended Year Ended December 31, 2016 (a) 2016 (a) 2016 (b) Total operating revenues $ 9,002 $ 24,468 $ 32,342 Net income attributable to common shareholders 501 1,346 1,562 Basic earnings per share $ 0.54 $ 1.46 $ 1.69 Diluted earnings per share 0.54 1.45 1.69 _________ (a) The amounts above include adjustments for non-recurring costs directly related to the merger of $20 million and $660 million for the three and nine months ended September 30, 2016 , respectively, and intercompany revenue of $171 million for the nine months ended September 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, Pepco and DPL) 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 are 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 11 - Debt and Credit Agreements for details regarding the nonrecourse debt associated with EGTP. As a result, as of September 30, 2017, 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. See Note 6 - Impairment of Long-Lived Assets for further information. In July 2016, DPL completed the sale of a 9 acre land parcel located on South Madison Street in Wilmington, DE, resulting in a pre-tax gain of approximately $4 million . 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. On June 16, 2016, Generation initiated the sales process of its Upstream business by executing a forbearance agreement with the lenders of the nonrecourse debt. See Note 11 - Debt and Credit Agreements for more information. In December 2016, Generation sold substantially all of the Upstream assets, see Note 4 - Mergers, Acquisitions and Dispositions of the Combined Notes to the Consolidated Financial Statements in the Exelon 2016 Form 10-K for further information. 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. 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 .

Regulatory Matters (All Registr

Regulatory Matters (All Registrants)	9 Months Ended
	Sep. 30, 2017
Regulated Operations [Abstract]
Regulatory Matters (All Registrants)	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 beginning 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 September 11, 2017, the ICC approved the IPA's ZES Procurement Plan filed with the ICC on July 31, 2017. Bidders interested in participating in the procurement process had 14 days following the ICC's approval of the plan to submit the required eligibility information and become qualified bidders. Generation’s Clinton and Quad Cities nuclear plants timely submitted the required eligibility information to the ICC and responded to follow up questions. 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. Illinois utilities will be required to purchase all ZECs delivered by the zero-emissions nuclear-powered generating facilities, subject to annual cost caps. For the initial delivery year, June 1, 2017 - May 31, 2018, the ZEC annual cost 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. ZECs delivered to Illinois utilities in excess of the annual cost cap will be paid in subsequent years if the payments do not exceed the prescribed annual cost cap for that year. On October 27, 2017, the IPA released the schedule for the ZEC procurement event indicating that contracts with zero emission facilities will be fully executed on January 30, 2018. Winning bidders will be entitled to compensation for the sale of ZECs retroactive to the June 1, 2017 effective date of FEJA. To the extent Generation is selected as a winning bidder, revenue retroactive to the effective date of FEJA would be recognized in the period the contracts are executed. Upon the execution of the contracts, ComEd will record an associated obligation and expense for the procurement of ZEC's. 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 $71 million as of September 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 district court granted the motions to dismiss. On July 17, 2017, the plaintiffs appealed the decision to the Seventh Circuit. Plaintiffs-Appellants initial brief was filed on August 28, 2017 and the state’s and Exelon’s briefs were filed on October 27, 2017. Reply briefs are due on December 12, 2017. 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 ComEd's electric distribution formula rate 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 September 30, 2017 , ComEd recorded an increase to its electric distribution services costs regulatory asset of approximately $21 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 September 11, 2017, the ICC approved ComEd's 2018 - 2021 energy efficiency plan with minor modifications filed by ComEd with the ICC on June 30, 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 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. ComEd cancelled its existing energy efficiency rate rider effective June 2, 2017. On August 1, 2017, ComEd filed with the ICC a reconciliation of revenues and costs incurred through the cancellation date. On August 30, 2017, the ICC approved ComEd's request, filed on August 1, 2017, to issue an $80 million credit on retail customers' bills in October 2017 for the majority of the over-recoveries with any final adjustment applicable to the over-recoveries to be billed or credited in the future. As of September 30, 2017 , ComEd’s over-recoveries associated with its former energy efficiency rate rider were $33 million . Initial Energy Efficiency Formula Rate Filing On August 15, 2017, the ICC approved ComEd's new initial energy efficiency formula rate filed with the ICC on June 9, 2017 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. 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. The approved energy efficiency formula rate also provides for revenue decoupling to effectively offset the favorable or unfavorable impacts to ComEd's energy efficiency formula rate revenues associated with variations in delivery volumes associated with above or below normal weather, numbers of customers or usage per customer. As of September 30, 2017 , Exelon and ComEd recorded a regulatory asset of $78 million under the energy efficiency formula, reflecting $83 million of deferred energy efficiency costs partially offset by $5 million of over recoveries for the initial energy efficiency formula rate reconciliation. 2017 Energy Efficiency Formula Rate Filing On September 11, 2017, the ICC approved ComEd's annual energy efficiency formula rate filed with the ICC on June 30, 2017 pursuant to FEJA. The filing establishes the revenue requirement used to set rates that will take effect in January 2018. 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 noncurrent liability, respectively, as of September 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 liability of $7 million as of September 30, 2017 . ComEd also recorded a regulatory liability of $38 million for alternative compliance payments received from RES to purchase RECs on behalf of the RES in the future. As of September 30, 2017, ComEd had received $45 million of over-recovered RPS costs and alternative compliance payments from RES, which are deposited into a separate interest bearing bank account pursuant to FEJA and are classified as Restricted cash on Exelon's and ComEd's 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 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 September 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. Office of Consumer Advocate 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 to increase its annual electric distribution base rates by $69 million , which was updated to $67 million on August 24, 2017, reflecting a requested ROE of 10.1% . The application included a request for an income tax adjustment to reflect full normalization of removal costs associated with pre-1981 property, which accounted for $18 million of the requested increase. On October 20, 2017, the MDPSC approved an increase in Pepco electric distribution rates of $34 million , reflecting a ROE of 9.5% . On October 27, 2017, the MDPSC issued an errata order revising the approved increase in Pepco electric distribution rates to $32 million . The errata order corrected a number of computational errors in the original order but did not alter any of the findings. The new rates became effective for services rendered on or after October 20, 2017. In its decision, the MDPSC denied Pepco’s request regarding the income tax adjustment without prejudice to Pepco filing another similar proposal with additional information. Requests for rehearing are due November 20, 2017. 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 , which was updated to $22 million on September 28, 2017, reflecting a requested ROE of 10.1% . DPL expects a decision in the matter in the first quarter of 2018, but 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 reflecting 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 $5 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. On August 7, 2017, following oral argument by the parties, a decision was issued from the Circuit Court affirming the decision of the MDPSC. On September 5, 2017, the residential consumer advocate filed an appeal of the Circuit Court's decision to the Maryland Court of Special Appeals. 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 September 30, 2017 and December 31, 2016 , the balance of BGE's regulatory asset was $219 million and $230 million , respectively, representing incremental program deployment costs. The current quarter balance of $219 million consists of three major components, including $133 million of unamortized incremental deployment costs of the AMI program, $54 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 September 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 $54 million portion representing the unamortized cost of the retired non-AMI meters and a $32 million portion

Impairment of Long-lived Assets

Impairment of Long-lived Assets (Exelon and Generation)	9 Months Ended
	Sep. 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, as of June 30, 2017, and September 30, 2017, certain of 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. As of June 30, 2017, the fair value analysis was based on an 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 this analysis, in the second quarter 2017, Exelon and Generation recorded a pre-tax impairment charge of $418 million within Operating and maintenance expense on their Consolidated Statements of Operations and Comprehensive Income. In the third quarter 2017, Exelon and Generation recorded an additional pre-tax impairment charge of $40 million within Operating and maintenance expense on their Consolidated Statements of Operations and Comprehensive Income to reflect an indicated decline in fair value based on new information obtained in the quarter through the orderly sales process. See Note 4 - Mergers, Acquisitions and Dispositions and Note 11 - Debt and Credit Agreements , for further 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 12 — Income Taxes for additional information.

Early Nuclear Plant Retirements

Early Nuclear Plant Retirements Early Nuclear Plant Retirements (Exelon, Generation)	9 Months Ended
	Sep. 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 2017, as a result of the plant retirement decision of TMI, Exelon and Generation recognized one-time charges in Operating and maintenance expense of $76 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. During the three and nine months ended September 30, 2017 , both Exelon’s and Generation’s results include an incremental $112 million and $149 million , respectively, of pre-tax expense for these items. Please refer to Note 13 — 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) Q3 2017 YTD 2017 Depreciation and amortization Accelerated depreciation (a) $ 106 $ 141 Accelerated nuclear fuel amortization 6 8 Total $ 112 $ 149 _________ (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 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 New York 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.

Intangibles Intangibles (Exelon

Intangibles Intangibles (Exelon and Generation)	9 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets Disclosure [Text Block]	Intangible Assets (Exelon and PHI) In the third quarter of 2015, PHI entered into a sponsorship agreement with the District of Columbia for future sponsorship rights associated with public property within the District of Columbia and paid the District of Columbia $25 million . The specific sponsorship rights were to be determined over time through future negotiations. As of September 30, 2017 , PHI has recorded the sponsorship agreement as a finite-lived intangible asset with a $25 million carrying amount.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities (All Registrants)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities (All Registrants)	9 . 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 September 30, 2017 and December 31, 2016 : Exelon September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 710 $ — $ 710 $ — $ 710 Long-term debt (including amounts due within one year) (a) 34,865 — 34,686 1,949 36,635 Long-term debt to financing trusts (b) 389 — — 423 423 SNF obligation 1,142 — 857 — 857 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 92 $ — $ 92 $ — $ 92 Long-term debt (including amounts due within one year) (a) 9,528 — 7,915 1,652 9,567 SNF obligation 1,142 — 857 — 857 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 7,600 $ — $ 8,353 $ — $ 8,353 Long-term debt to financing trusts (b) 205 — — 226 226 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,902 $ — $ 3,181 $ — $ 3,181 Long-term debt to financing trusts 184 — — 197 197 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,577 $ — $ 2,817 $ — $ 2,817 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) September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 118 $ — $ 118 $ — $ 118 Long-term debt (including amounts due within one year) (a) 5,930 — 5,729 297 6,026 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,546 $ — $ 3,087 $ 9 $ 3,096 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 54 $ — $ 54 $ — $ 54 Long-term debt (including amounts due within one year) (a) 1,326 — 1,407 — 1,407 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 65 $ — $ 65 $ — $ 65 Long-term debt (including amounts due within one year) (a) 1,130 — 969 288 1,257 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 $196 million , $51 million , $53 million , $17 million , $17 million , $6 million , $32 million , $11 million , and $5 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of September 30, 2017 . Includes unamortized debt issuance costs which are not fair valued of $200 million , $64 million , $46 million , $15 million , $15 million , $2 million , $30 million , $11 million , and $6 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of December 31, 2016 . (b) Includes unamortized debt issuance costs which are not fair valued of $1 million and $1 million for Exelon and ComEd, respectively, as of September 30, 2017 . Includes unamortized debt issuance costs which are not fair valued of $7 million , $1 million , and $6 million for Exelon, ComEd and BGE, respectively, as of December 31, 2016 . 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. The carrying amount also includes $112 million as of September 30, 2017 for 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 nine months ended September 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 September 30, 2017 and December 31, 2016 : Generation Exelon As of September 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) $ 80 $ — $ — $ — $ 80 $ 944 $ — $ — $ — $ 944 NDT fund investments Cash equivalents (b) 149 86 — — 235 149 86 — — 235 Equities 3,935 840 — 2,088 6,863 3,935 840 — 2,088 6,863 Fixed income Corporate debt — 1,651 255 — 1,906 — 1,651 255 — 1,906 U.S. Treasury and agencies 1,951 28 — — 1,979 1,951 28 — — 1,979 Foreign governments — 70 — — 70 — 70 — — 70 State and municipal debt — 246 — — 246 — 246 — — 246 Other (c) — 46 — 509 555 — 46 — 509 555 Fixed income subtotal 1,951 2,041 255 509 4,756 1,951 2,041 255 509 4,756 Middle market lending — — 416 87 503 — — 416 87 503 Private equity — — — 212 212 — — — 212 212 Real estate — — — 449 449 — — — 449 449 NDT fund investments subtotal (d) 6,035 2,967 671 3,345 13,018 6,035 2,967 671 3,345 13,018 Pledged assets for Zion Station decommissioning Cash equivalents 15 — — — 15 15 — — — 15 Generation Exelon As of September 30, 2017 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Middle market lending — — 17 25 42 — — 17 25 42 Pledged assets for Zion Station (e) 15 — 17 25 57 15 — 17 25 57 Rabbi trust investments Cash equivalents 5 — — — 5 77 — — — 77 Mutual funds 22 — — — 22 56 — — — 56 Fixed income — — — — — — 13 — — 13 Life insurance contracts — 21 — — 21 — 68 21 — 89 Rabbi trust investments subtotal 27 21 — — 48 133 81 21 — 235 Commodity derivative assets Economic hedges 487 2,076 1,628 — 4,191 487 2,076 1,628 — 4,191 Proprietary trading 2 41 42 — 85 2 41 42 — 85 Effect of netting and allocation of collateral (f) (g) (501 ) (1,828 ) (837 ) — (3,166 ) (501 ) (1,828 ) (837 ) — (3,166 ) Commodity derivative assets subtotal (12 ) 289 833 — 1,110 (12 ) 289 833 — 1,110 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 10 — — 10 Economic hedges 3 13 — — 16 3 13 — — 16 Effect of netting and allocation of collateral (3 ) (8 ) — — (11 ) (3 ) (8 ) — — (11 ) Interest rate and foreign currency derivative assets subtotal — 5 — — 5 — 15 — — 15 Other investments — — 43 — 43 — — 43 — 43 Total assets 6,145 3,282 1,564 3,370 14,361 7,115 3,352 1,585 3,370 15,422 Liabilities Commodity derivative liabilities Economic hedges (559 ) (2,062 ) (1,189 ) — (3,810 ) (559 ) (2,062 ) (1,466 ) — (4,087 ) Proprietary trading (3 ) (43 ) (27 ) — (73 ) (3 ) (43 ) (27 ) — (73 ) Effect of netting and allocation of collateral (f) (g) 560 2,043 978 — 3,581 560 2,043 978 — 3,581 Commodity derivative liabilities subtotal (2 ) (62 ) (238 ) — (302 ) (2 ) (62 ) (515 ) — (579 ) Interest rate and foreign currency derivative liabilities Economic hedges (2 ) (17 ) — — (19 ) (2 ) (17 ) — — (19 ) Effect of netting and allocation of collateral 2 8 — — 10 2 8 — — 10 Interest rate and foreign currency derivative liabilities subtotal — (9 ) — — (9 ) — (9 ) — — (9 ) Deferred compensation obligation — (35 ) — — (35 ) — (137 ) — — (137 ) Total liabilities (2 ) (106 ) (238 ) — (346 ) (2 ) (208 ) (515 ) — (725 ) Total net assets $ 6,143 $ 3,176 $ 1,326 $ 3,370 $ 14,015 $ 7,113 $ 3,144 $ 1,070 $ 3,370 $ 14,697 Generation Exelon As of December 31, 2016 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 39 $ — $ — $ — $ 39 $ 373 $ — $ — $ — $ 373 NDT fund investments Cash equivalents (b) 110 19 — — 129 110 19 — — 129 Equities 3,551 452 — 2,011 6,014 3,551 452 — 2,011 6,014 Fixed income Corporate debt — 1,554 250 — 1,804 — 1,554 250 — 1,804 U.S. Treasury and agencies 1,291 29 — — 1,320 1,291 29 — — 1,320 Foreign governments — 37 — — 37 — 37 — — 37 State and municipal debt — 264 — — 264 — 264 — — 264 Other (c) — 59 — 493 552 — 59 — 493 552 Fixed income subtotal 1,291 1,943 250 493 3,977 1,291 1,943 250 493 3,977 Middle market lending — — 427 71 498 — — 427 71 498 Private equity — — — 148 148 — — — 148 148 Real estate — — — 326 326 — — — 326 326 NDT fund investments subtotal (d) 4,952 2,414 677 3,049 11,092 4,952 2,414 677 3,049 11,092 Pledged assets for Zion Station decommissioning Cash equivalents 11 — — — 11 11 — — — 11 Equities — 2 — — 2 — 2 — — 2 Fixed Income - U.S. Treasury and agencies 16 1 — — 17 16 1 — — 17 Middle market lending — — 19 64 83 — — 19 64 83 Pledged assets for Zion Station decommissioning subtotal (e) 27 3 19 64 113 27 3 19 64 113 Rabbi trust investments Cash equivalents 2 — — — 2 74 — — — 74 Mutual funds 19 — — — 19 50 — — — 50 Fixed income — — — — — — 16 — — 16 Life insurance contracts — 18 — — 18 — 64 20 — 84 Rabbi trust investments subtotal 21 18 — — 39 124 80 20 — 224 Commodity derivative assets Economic hedges 1,356 2,505 1,229 — 5,090 1,358 2,505 1,229 — 5,092 Proprietary trading 3 50 23 — 76 3 50 23 — 76 Effect of netting and allocation of collateral (f) (g) (1,162 ) (2,142 ) (481 ) — (3,785 ) (1,164 ) (2,142 ) (481 ) — (3,787 ) Commodity derivative assets subtotal 197 413 771 — 1,381 197 413 771 — 1,381 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 16 — — 16 Economic hedges — 28 — — 28 — 28 — — 28 Proprietary trading 3 2 — — 5 3 2 — — 5 Effect of netting and allocation of collateral (2 ) (19 ) — — (21 ) (2 ) (19 ) — — (21 ) Interest rate and foreign currency derivative assets subtotal 1 11 — — 12 1 27 — — 28 Other investments — — 42 — 42 — — 42 — 42 Total assets 5,237 2,859 1,509 3,113 12,718 5,674 2,937 1,529 3,113 13,253 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 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 $282 million and $252 million at September 30, 2017 and December 31, 2016 and restricted cash of $184 million and $157 million at September 30, 2017 and December 31, 2016 . Exelon excludes cash of $382 million and $360 million at September 30, 2017 and December 31, 2016 and restricted cash of $219 million and $180 million at September 30, 2017 and December 31, 2016 and includes long-term restricted cash of $22 million and $25 million at September 30, 2017 and December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) Includes $75 million and $29 million of cash received from outstanding repurchase agreements at September 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 less than $1 million and $(2) million , which have a total notional amount of $885 million and $933 million at September 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 $52 million and $31 million at September 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 September 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 $59 million , $215 million and $141 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of September 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), $27 million represents variation margin on the exchanges as of September 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 September 30, 2017 and December 31, 2016 : ComEd PECO BGE As of September 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) $ 273 $ — $ — $ 273 $ 314 $ — $ — $ 314 $ 18 $ — $ — $ 18 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 273 — — 273 321 10 — 331 23 — — 23 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (10 ) — (10 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (277 ) (277 ) — — — — — — — — Total liabilities — (7 ) (277 ) (284 ) — (10 ) — (10 ) — (4 ) — (4 ) Total net assets (liabilities) $ 273 $ (7 ) $ (277 ) $ (11 ) $ 321 $ — $ — $ 321 $ 23 $ (4 ) $ — $ 19 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 $36 million at September 30, 2017 and December 31, 2016 and restricted cash of $2 million at December 31, 2016 . PECO excludes cash of $20 million and $22 million at September 30, 2017 and December 31, 2016 . BGE excludes cash of $11 million and $13 million at September 30, 2017 and December 31, 2016 and restricted cash of $1 million at September 30, 2017 and includes long-term restricted cash of $2 million at December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) The Level 3 balance consists of the current and noncurrent liability of $20 million and $257 million , respectively, at September 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 September 30, 2017 and December 31, 2016 : Successor As of September 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) $ 184 $ — $ — $ 184 $ 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 72 — — 72 73 — — 73 Fixed income — 13 — 13 — 16 — 16 Life insurance contracts — 23 21 44 — 22 20 42 Rabbi trust investments subtotal 72 36 21 129 73 38 20 131 Total assets 256 36 21 313 290 38 20 348 Liabilities Deferred compensation obligation — (24 ) — (24 ) — (28 ) — (28 ) Total liabilities — (24 ) — (24 ) — (28 ) — (28 ) Total net assets $ 256 $ 12 $ 21 $ 289 $ 290 $ 10 $ 20 $ 320 Pepco DPL ACE As of September 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 $ — $ — $ — $ — $ 31 $ — $ — $ 31 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 — — — — 31 — — 31 Liabilities Deferred compensation obligation — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total liabilities — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 187 $ 32 $ 21 $ 240 $ — $ (1 ) $ — $ (1 ) $ 31 $ — $ — $ 31 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 $18 million and $19 million at September 30, 2017 and December 31, 2016 and includes long-term restricted cash of $22 million and $23 million at September 30, 2017 and December 31, 2016 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $7 million and $9 million at September 30, 2017 and December 31, 2016 . DPL excludes cash of $3 million and $4 million at September 30, 2017 and December 31, 2016 . ACE excludes cash of $5 million and $3 million at September 30, 2017 and December 31, 2016 and includes long-term restricted cash of $22 million and $23 million at September 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 nine months ended September 30, 2017 and 2016 : Successor Generation ComEd PHI Exelon Three Months Ended September 30, 2017 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Total Balance as of June 30, 2017 $ 683 $ 21 $ 589 $ 41 $ 1,334 $ (256 ) $ 20 $ — $ 1,098 Total realized / unrealized gains (losses) Included in net income — — (82 ) (a) 1 (81 ) — 1 — (80 ) Included in payable for Zion Station decommissioning — (4 ) — — (4 ) — — — (4 ) Included in regulatory assets — — — — — (21 ) (b) — — (21 ) Change in collateral — — 11 — 11 — — — 11 Purchases, sales, issuances and settlements Purchases 19 — 57 1 77 — — — 77 Settlements (31 ) — 10 (c) — (21 ) — — — (21 ) Transfers out of Level 3 — — 10 — 10 — — — 10 Balance at September 30, 2017 $ 671 $ 17 $ 595 $ 43 $ 1,326 $ (277 ) $ 21 $ — $ 1,070 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2017 $ — $ — $ 24 $ 1 $ 25 $ — $ 1 $ — $ 26 Successor Generation ComEd PHI Exelon Nine Months Ended September 30, 2017 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives 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 — (110 ) (a) 2 (104 ) — 2 — (102 ) Included in noncurrent payables to affiliates 13 — — — 13 — — (13 ) — Included in payable for Zion Station decommissioning — (3 ) — — (3 ) — — — (3 ) Included in regulatory assets — — — — — (19 ) (b) — 13 (6 ) Change in collateral — — 81 — 81 — — — 81 Purchases, sales, issuances and settlements Purchases 54 1 146 4 205 — — — 205 Sales — — (15 ) — (15 ) — — — (15 ) Issuances — — — — — — (1 ) — (1 ) Settlements (77 ) — (8 ) (c) — (85 ) — — — (85 ) Transfers into Level 3 — — (9 ) — (9 ) — — — (9 ) Transfers out of Level 3 — — 17 (5 ) 12 — — — 12 Balance as of September 30, 2017 $ 671 $ 17 $ 595 $ 43 $ 1,326 $ (277 ) $ 21 $ — $ 1,070 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2017 $ 2 $ — $ 161 $ 2 $ 165 $ — $ 2 $ — $ 167 _________ (a) Includes a reduction for the reclassification of $96 million and $279 million of realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2017 . (b) Includes $ 24 million of decreases in fair value and an increase for realized losses due to settlements of $ 3 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2017 . Includes $ 32 million of decreases in fair value and an increase for realized losses due to settlements of $ 13 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2017 . (c) Exelon includes the settlement value for any open contracts that were net settled prior to their scheduled maturity within this line item. Successor Generation ComEd PHI Exelon Three Months Ended September 30, 2016 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Total Balance as of June 30, 2016 $ 715 $ 25 $ 609 $ 37 $ 1,386 $ (221 ) $ 20 $ — $ 1,185 Total realized / unrealized gains (losses) Included in net income (4 ) — 95 (a) 1 92 — 1 — 93 Included in noncurrent payables to affiliates 6 — — — 6 — — (6 ) — Included in payable for Zion Station decommissioning — (1 ) — — (1 ) — — — (1 ) Included in regulatory assets — — — — — (23 ) (b) — 6 (17 ) Change in collateral — — 31 — 31 — — — 31 Purchases, sales, issuances and settlements Purcha

Derivative Financial Instrument

Derivative Financial Instruments (All Registrants)	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments (All Registrants)	10 . 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 consolidated 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 September 30, 2017 , the percentage of expected generation hedged is 98% - 101% , 79% - 82% , and 45% - 48% 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, BGE, Pepco, DPL, and ACE 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. 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 2,601 GWhs and 6,763 GWhs for the three and nine months ended September 30, 2017 , respectively, and 1,506 GWhs and 4,015 GWhs and for the three and nine months September 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 (All Registrants) 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 September 30, 2017 , Exelon had $800 million of notional amounts of fixed-to-floating hedges outstanding, and Exelon and Generation had $491 million of notional amounts of floating-to-fixed hedges outstanding. 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 September 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) $ — $ 15 $ — $ (10 ) $ 5 $ — $ 5 Mark-to-market derivative assets (noncurrent assets) — 1 — (1 ) — 10 10 Total mark-to-market derivative assets — 16 — (11 ) 5 10 15 Mark-to-market derivative liabilities (current liabilities) — (17 ) — 9 (8 ) — (8 ) Mark-to-market derivative liabilities (noncurrent liabilities) — (2 ) — 1 (1 ) — (1 ) Total mark-to-market derivative liabilities — (19 ) — 10 (9 ) — (9 ) Total mark-to-market derivative net assets (liabilities) $ — $ (3 ) $ — $ (1 ) $ (4 ) $ 10 $ 6 __________ (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 September 30, Income Statement Location 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on Borrowings Exelon Interest expense $ (2 ) $ (8 ) $ 6 $ 14 Nine Months Ended September 30, Income Statement Location 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on Borrowings Exelon Interest expense $ (6 ) $ 15 $ 17 $ (3 ) At September 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 $10 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 nine months ended September 30, 2017 and 2016 , the impact on the results of operations as a result of ineffectiveness from fair value hedges was a $4 million gain, a $11 million gain, a $6 million gain, and a $12 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 11 — 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 11 — Debt and Credit Agreements for additional information. During the three and nine months ended September 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 $491 million as of September 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 September 30, 2017 , the subsidiary had a $6 million derivative liability related to the swap. During the three and nine months ended September 30, 2017 , a gain of $2 million and a loss of $2 million related to the swap, respectively, were recorded to Interest expense. 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 September 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 $111 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 September 30, 2017 and December 31, 2016 , $3 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, including margin on exchange positions, 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 September 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) $ 2,608 $ 55 $ (1,969 ) $ 694 $ — $ — $ — $ — $ — $ 694 Mark-to-market derivative assets (noncurrent assets) 1,583 30 (1,197 ) 416 — — — — — 416 Total mark-to-market derivative assets 4,191 85 (3,166 ) 1,110 — — — — — 1,110 Mark-to-market derivative liabilities (current liabilities) (2,334 ) (46 ) 2,230 (150 ) (20 ) — — — — (170 ) Mark-to-market derivative liabilities (noncurrent liabilities) (1,476 ) (27 ) 1,351 (152 ) (257 ) — — — — (409 ) Total mark-to-market derivative liabilities (3,810 ) (73 ) 3,581 (302 ) (277 ) — — — — (579 ) Total mark-to-market derivative net assets (liabilities) $ 381 $ 12 $ 415 $ 808 $ (277 ) $ — $ — $ — $ — $ 531 _________ (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 $123 million and $61 million , respectively, and current and noncurrent liabilities are shown net of collateral of $138 million and $93 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $415 million at September 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), $27 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 as

Debt and Credit Agreements (All

Debt and Credit Agreements (All Registrants)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Debt and Credit Agreements (All Registrants)	11 . 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 September 30, 2017 and December 31, 2016 : Commercial Paper Borrowings September 30, 2017 December 31, 2016 Exelon $ 118 $ 688 Generation — 620 BGE — 45 PHI 118 23 Pepco — 23 DPL 54 — ACE 65 — 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 nine months ended September 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 $ 14 Albany Green Energy biomass generation development. Generation Energy Efficiency Project Financing 3.90 % February 1, 2018 $ 17 Funding to install energy conservation measures for the Naval Station Great Lakes project. Generation Energy Efficiency Project Financing 2.61 % September 30, 2018 $ 10 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 $ 4 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. ComEd First Mortgage Bonds, Series 122 2.95 % August 15, 2027 $ 350 Refinance maturing first mortgage bonds, to repay a portion of ComEd’s outstanding commercial paper obligations and for general corporate purposes. ComEd First Mortgage Bonds, Series 123 3.75 % August 15, 2047 $ 650 Refinance maturing first mortgage bonds, to repay a portion of ComEd’s outstanding commercial paper obligations and for general corporate purposes. PECO First and Refunding Mortgage Bonds 3.70 % September 15, 2047 $ 325 General corporate purposes. BGE Notes 3.75 % August 15, 2047 $ 300 Redeem $250 million in principal amount of the 6.20% Deferrable Interest Subordinated Debentures due October 15, 2043 issued by BGE's affiliate BGE Capital Trust II, repay commercial paper obligations and for general corporate purposes. Pepco Energy Efficiency Project Financing 3.30 % December 15, 2017 $ 2 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 September 30, 2017 , $660 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 10 — 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 September 30, 2017 . See Note 17 - Earnings Per Share and Equity for further information on the issuance of common stock. Albany Green Energy Project During the third quarter of 2017, upon completion of AGE, Generation retired $228 million of its LIBOR + 1.25% outstanding debt balance, which included $6 million of accumulated interest. Pursuant to the financing terms entered into by AGE in the second quarter of 2015, the entire financing balance plus accumulated interest was due upon substantial completion, but no later than November 17, 2017. See Note 3 - Variable Interest Entities for more details regarding AGE. BGE Redemption of Trust Preferred Securities On August 28, 2017, BGE redeemed all of the outstanding shares of BGE Capital Trust II 6.20% Preferred Securities (“Securities”), pursuant to the optional redemption provisions of the Indenture under which the Securities were issued. The redemption price per share was $25.19 , which equaled the stated value per share plus accrued and unpaid dividends to, but excluding, the redemption date. No dividends on the Securities redeemed were accrued on or after the redemption date, nor did any interest accrue on amounts held to pay the redemption price.

Income Taxes (All Registrants)

Income Taxes (All Registrants)	9 Months Ended
	Sep. 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 September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE 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 2.2 5.6 6.6 (0.1) 5.3 5.1 2.2 5.3 5.6 Qualified nuclear decommissioning trust fund income 2.6 5.8 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.1) (2.2) (0.2) (0.1) (0.1) (0.2) (0.1) (0.2) (0.4) Plant basis differences (2.6) — (0.3) (14.6) (0.8) (4.9) (6.7) (1.9) (3.4) Production tax credits and other credits (2.2) (4.8) — — — — — — — Noncontrolling interests 0.5 1.0 — — — — — — — FitzPatrick bargain purchase gain (0.2) (0.4) — — — — — — — Other (0.1) 0.3 (0.2) (0.2) (0.2) 0.2 — (0.2) 0.1 Effective income tax rate 34.1% 40.3% 40.9% 20.0% 39.2% 35.2% 30.4% 38.0% 36.9% Three Months Ended September 30, 2016 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 3.8 2.6 7.3 2.4 5.2 5.6 5.6 5.2 6.1 Qualified nuclear decommissioning trust fund income 4.0 7.8 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.9) (1.6) (0.6) (0.1) (0.2) (0.1) — (0.2) (0.1) Plant basis differences (3.0) — (1.9) (6.7) (0.5) (5.0) (6.7) (1.3) (4.6) Production tax credits and other credits (2.9) (5.7) (0.1) — — — — — — Noncontrolling interest 0.2 0.5 — — — — — — — Statute of limitations expiration (0.1) 0.3 — — — — — — — Penalties 4.3 — 27.2 — — — — — — Merger expenses (0.6) — — — — (5.7) (2.3) (8.6) (2.9) Other (0.8) (0.5) 0.1 0.1 (0.4) (0.7) (0.9) 0.1 (0.6) Effective income tax rate 39.0% 38.4% 67.0% 30.7% 39.1% 29.1% 30.7% 30.2% 32.9% Nine Months Ended September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 0.7 2.1 5.9 (0.1) 5.2 4.9 3.0 5.1 5.6 Qualified nuclear decommissioning trust fund income 4.0 14.0 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.9) (2.7) (0.2) (0.1) (0.1) (0.2) (0.1) (0.2) (0.4) Plant basis differences (3.4) — (0.3) (14.4) (0.8) (4.6) (6.3) (1.8) (3.4) Production tax credits and other credits (1.8) (6.2) — — — — — — — Noncontrolling interests 0.2 0.7 — — — — — — — Merger expenses (5.4) (2.5) — — — (11.8) (8.0) (10.0) (23.0) FitzPatrick bargain purchase gain (3.2) (11.2) — — — — — — — Like-kind exchange (a) (1.7) — 1.7 — — — — — — Other — (0.4) 0.2 — 0.2 — (0.3) 0.6 (0.3) Effective income tax rate 23.5% 28.8% 42.3% 20.4% 39.5% 23.3% 23.3% 28.7% 13.5% Successor Predecessor Nine Months Ended September 30, 2016 March 24, 2016 to September 30, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL (b) ACE (b) PHI (b) PHI U.S. Federal statutory rate 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit (c) 2.5 2.6 5.4 1.3 4.8 23.0 310.5 5.5 4.4 11.9 Qualified nuclear decommissioning trust fund income 4.8 8.8 — — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.3) (2.0) (0.3) (0.1) (0.2) (0.2) (17.9) 0.5 0.5 (0.9) Plant basis differences (4.5) — (0.6) (8.8) (3.3) (29.0) (98.6) 7.8 17.5 (13.5) Production tax credits and other credits (4.1) (7.6) — — — — — — — — Noncontrolling interest 0.5 0.9 — — — — — — — — Statute of limitations expiration (0.5) (1.7) — — — — — — — — Penalties 2.3 — 5.6 — — — — — — — Merger expenses 6.2 — — — — 36.7 635.9 (35.4) (49.8) 11.1 Other (1.8) (2.1) — (1.5) — (2.5) 35.1 0.4 1.4 3.6 Effective income tax rate 39.1% 33.9% 45.1% 25.9% 36.3% 63.0% 900.0% 13.8% 9.0% 47.2% _________ (a) See Like-Kind Exchange within the Other Income Tax Matters section below for further details. (b) DPL and ACE recognized a loss before income taxes for the nine months ended September 30, 2016 , and PHI recognized a loss before income taxes for the period of March 24, 2016, through September 30, 2016 . As a result, positive percentages represent an income tax benefit for the periods presented. (c) Includes a remeasurement of uncertain state income tax positions for Pepco and DPL. Accounting for Uncertainty in Income Taxes The Registrants have the following unrecognized tax benefits as of September 30, 2017 and December 31, 2016 : Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2017 $ 738 $ 468 $ 2 $ — $ 120 $ 120 $ 59 $ 21 $ 8 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 September 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 September 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 Positions As of September 30, 2017 , Exelon, Generation, BGE, PHI, Pepco, DPL, and ACE have approximately $676 million , $ 469 million , $120 million , $ 88 million , $ 59 million , $ 21 million , and $ 8 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, potential settlements, and the outcomes of pending court cases. Of the above unrecognized tax benefits, Exelon and Generation have $ 462 million that, if recognized, would decrease the effective tax rate. The unrecognized tax benefits related to BGE, DPL, ACE, 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. 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 September of 2017, Exelon appealed this decision to the U.S. Court of Appeals for the Seventh Circuit. 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, an additional $ 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 . As of June 30, 2017, ComEd had a total receivable from Exelon pursuant to the hold harmless agreement of $ 369 million , which was included in Current Receivables from Affiliates on ComEd’s Consolidated Balance Sheet. Exelon expects to pay the tax, penalties and interest of approximately $ 1.3 billion related to the like-kind exchange, including $ 300 million attributable to ComEd, in the fourth quarter of 2017. While Exelon will receive a tax benefit of approximately $ 350 million associated with the deduction for the interest, Exelon currently has a net operating loss carryforward and thus does not expect to realize the cash benefit until 2018. After taking into account these interest deduction tax benefits, the total estimated net cash outflow for the like-kind exchange is approximately $ 950 million , of which approximately $ 300 million is attributable to ComEd after giving consideration to Exelon’s agreement to hold ComEd harmless from any unfavorable impacts on ComEd’s equity from the like-kind exchange position. Following a final appellate decision, which is expected in 2018, 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. Any remaining amounts due to the IRS will be paid by Exelon in the fourth quarter of 2017. 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. In the third quarter of 2017, the $ 300 million payable discussed above attributable to ComEd, net of ComEd’s receivable pursuant to the hold harmless agreement, was settled with Exelon. 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, PHI and Pepco) 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's, PHI's and Pepco's long-term marginal state income tax rate were revised in the first quarter of 2017 as a result of a statutory rate change in Washington, D.C. As a result, Exelon, PHI and Pepco recorded a one-time decrease to Deferred income tax liability of $ 28 million , $ 8 million , and $ 8 million , respectively, on their Consolidated Balance Sheets. Because income taxes are recovered through customer rates, Exelon, PHI and Pepco recorded a corresponding regulatory liability of $ 8 million , in the Consolidated Balance Sheets. In addition, Exelon recorded a decrease to Income tax expense of $ 20 million , net of federal taxes, in the Consolidated Statements of Operations and Comprehensive Income for the three months ended March 31, 2017. In the third quarter of 2017, Exelon reviewed and updated its marginal state income tax rates based on 2016 state apportionment rates. In addition, Exelon, Generation and ComEd recorded the impacts of Illinois’ statutory rate change, which increased the total corporate income tax rate from 7.75% to 9.5% effective July 1, 2017. As a result of the rate changes, in the third quarter of 2017, Exelon, Generation and ComEd recorded a one-time increase to Deferred income taxes of approximately $ 250 million , $ 20 million and $ 270 million , respectively, on their Consolidated Balance Sheets. Because income taxes are recovered through customer rates, each of Exelon and ComEd recorded a corresponding regulatory asset of $ 272 million . Further, Exelon recorded a decrease to Income tax expense of approximately $ 20 million and Generation recorded an increase to Income tax expense of approximately $ 20 million (each net of federal taxes) in their Consolidated Statements of Operations and Comprehensive Income for the three and nine months ended September 30, 2017. The Illinois statutory rate increase is not expected to have a material ongoing impact to Exelon’s, Generation’s or ComEd’s future results of operations.

Nuclear Decommissioning (Exelon

Nuclear Decommissioning (Exelon and Generation)	9 Months Ended
	Sep. 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 September 30, 2017 : Nuclear decommissioning ARO at December 31, 2016 (a) $ 8,734 Acquisition of FitzPatrick 444 Accretion expense 342 Net decrease due to changes in, and timing of, estimated cash flows (148 ) Costs incurred to decommission retired plants (6 ) Nuclear decommissioning ARO at September 30, 2017 (a) $ 9,366 _________ (a) Includes $12 million and $10 million for the current portion of the ARO at September 30, 2017 and December 31, 2016 , respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets. During the nine months ended September 30, 2017 , Generation’s nuclear ARO increased by approximately $632 million . The increase primarily reflects the net impacts of the acquisition of FitzPatrick, the announced early retirement of TMI, year-to-date accretion of the ARO liability due to the passage of time and ARO updates completed during 2017 to reflect changes in amounts and timing of estimated decommissioning cash flows. In the first quarter of 2017, a preliminary estimate of $417 million was recorded for the fair value of FitzPatrick’s ARO. In the third quarter of 2017, an adjustment was recorded to increase the FitzPatrick ARO valuation by $27 million to $444 million to reflect updated cost estimate inputs from a third-party engineering firm. For additional details on the acquisition of FitzPatrick, see Note 4 - Mergers, Acquisitions and Dispositions . The net $148 million decrease due to changes in, and timing of, estimated cash flows was driven by multiple adjustments throughout the period, some with offsetting impacts. These adjustments include a $180 million decrease for refinements in estimated fleet wide labor costs expected to be incurred for certain on-site personnel during decommissioning as well as decreases resulting from updates to the cost studies of Clinton and Quad Cities. These decreases were partially offset by a $138 million increase in TMI's ARO liability associated with the May 30, 2017 announcement to early retire the unit on September 30, 2019. 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 an updated decommissioning cost study. Refer to Note 7 - Early Nuclear Plant Retirements for additional information regarding the announced early retirement of TMI. 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 . 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. On August 8, 2017, the PAPUC approved the filing and the new rates will be effective January 1, 2018. 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. Exelon and Generation had NDT fund investments totaling $12,966 million and $11,061 million at September 30, 2017 and December 31, 2016 , respectively. The increase is primarily driven by improved market performance and the acquisition of FitzPatrick. The following table provides unrealized gains on NDT funds for the three and nine months ended September 30, 2017 and 2016 : Exelon and Generation Exelon and Generation Three Months Ended Nine Months Ended 2017 2016 2017 2016 Net unrealized gains on decommissioning trust funds — Regulatory Agreement Units (a) $ 44 $ 155 $ 253 $ 286 Net unrealized gains on decommissioning trust funds — Non-Regulatory Agreement Units (b)(c) 111 116 347 216 _________ (a) Net unrealized gains related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets. (b) Excludes $4 million and $5 million of net unrealized losses related to the Zion Station pledged assets for the three months ended September 30, 2017 and 2016 respectively. Excludes $5 million and $2 million of net unrealized losses related to the Zion Station pledged assets for the nine months ended September 30, 2017 and 2016 , respectively. Net unrealized 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 $112 million which is included within the nuclear decommissioning ARO at September 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 September 30, 2017 and December 31, 2016 : Exelon and Generation September 30, 2017 December 31, 2016 Carrying value of Zion Station pledged assets $ 57 $ 113 Payable to Zion Solutions (a) 53 104 Current portion of payable to Zion Solutions (b) 53 90 Cumulative withdrawals by Zion Solutions to pay decommissioning costs (c) 928 878 _________ (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 ZionSolutions (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 was approved on August 8, 2017 and 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 necessitate that Exelon post a 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)	9 Months Ended
	Sep. 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 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. During the first quarter of 2017 , in connection with the acquisition of Fitzpatrick, Exelon established a new qualified pension plan and a new OPEB plan, and recorded a provisional obligation for Fitzpatrick employees based on information available at the merger date of $38 million and $11 million , respectively. As permitted by business combinations accounting guidance, during the third quarter of 2017 , Exelon updated those obligations based on a final valuation for Fitzpatrick employees as of the merger date of March 31, 2017. The updated obligations for pension and OPEB were $ 16 million and $ 17 million , respectively. Refer to Note 4 - Mergers, Acquisitions and Dispositions for additional discussion of the acquisition of FitzPatrick. 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 nine months ended September 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 $ 98 $ 92 $ 26 $ 27 Interest cost 211 215 45 47 Expected return on assets (300 ) (293 ) (39 ) (42 ) Amortization of: Prior service (benefit) cost (1 ) 3 (47 ) (48 ) Actuarial loss 152 142 15 18 Settlement charges 1 — — — Net periodic benefit cost $ 161 $ 159 $ — $ 2 Pension Benefits Other Postretirement Benefits 2017 (a) 2016 (b) 2017 (a) 2016 (b) Components of net periodic benefit cost: Service cost $ 290 $ 262 $ 79 $ 80 Interest cost 632 616 136 138 Expected return on assets (898 ) (847 ) (121 ) (121 ) Amortization of: Prior service cost (benefit) — 10 (140 ) (138 ) Actuarial loss 455 411 46 47 Settlement charges 3 — — — Net periodic benefit cost $ 482 $ 452 $ — $ 6 _________ (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 nine months ended September 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 September 30, 2016 , respectively. Three Months Ended September 30, Nine Months Ended September 30, Pension and Other Postretirement Benefit Costs 2017 2016 2017 2016 Exelon $ 161 $ 161 $ 482 $ 458 Generation (a) 57 54 170 163 ComEd 44 41 131 124 PECO 7 8 21 25 BGE 16 17 48 51 BSC (b) 13 13 40 37 Pepco (c) 6 8 19 24 DPL (c) 3 4 10 13 ACE (c) 3 4 10 11 PHISCO (c)(d) 12 12 33 33 Successor Predecessor Pension and Other Postretirement Benefit Costs Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 Nine Months Ended September 30, 2017 March 24, 2016 to September 30, 2016 January 1, 2016 to March 23, 2016 PHI $ 24 $ 28 $ 72 $ 58 $ 23 _________ (a) FitzPatrick net benefit costs are included for the period after acquisition. (b) 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. (c) Pepco's, DPL's, ACE's and PHISCO's pension and postretirement benefit costs for the nine months ended September 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 . (d) These amounts represent amounts billed to Pepco, DPL, and ACE through intercompany allocations. These amounts are not included in Pepco, DPL, or ACE amounts above. 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 nine months ended September 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 September 30, 2016 , respectively. Three Months Ended September 30, Nine Months Ended September 30, Savings Plan Matching Contributions 2017 2016 2017 2016 Exelon $ 34 $ 51 $ 97 $ 107 Generation 14 31 42 56 ComEd 9 10 24 23 PECO 3 3 7 7 BGE 3 2 7 5 BSC (a) 2 2 7 9 Pepco (b) 1 — 3 2 DPL (b) 1 1 2 2 ACE — — 1 1 PHISCO (b)(c) 1 2 4 5 Successor Predecessor Savings Plan Matching Contributions Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 Nine Months Ended September 30, 2017 March 24, 2016 to September 30, 2016 January 1, 2016 to March 23, 2016 PHI $ 3 $ 3 $ 10 $ 7 $ 3 _________ (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 and PHISCO's matching contributions for the nine months ended September 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 nine months ended September 30, 2016 . (c) These amounts represent amounts billed to Pepco, DPL, and ACE through intercompany allocations. These amounts are not included in Pepco, DPL, or ACE amounts above.

Severance (All Registrants)

Severance (All Registrants)	9 Months Ended
	Sep. 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 nine months ended September 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 September 30, 2017 $ 1 $ — $ — $ 1 $ 1 $ — $ — September 30, 2016 8 7 — 1 — — — Nine Months Ended September 30, 2017 $ 10 $ 4 $ 2 $ 4 $ 2 $ 1 $ 1 September 30, 2016 12 10 1 1 — — — _________ (a) The amounts above for Generation include $2 million for amounts billed by BSC through intercompany allocations for the nine months ended September 30, 2017 and $1 million and $2 million for the three and nine months ended September 30, 2016 , respectively. The amounts above for ComEd include $1 million for amounts billed by BSC through intercompany allocations for the three and nine months ended September 30, 2016 . The amounts above for PHI include less than $1 million and $1 million billed by BSC through intercompany allocations for the three and nine months ended September 30, 2017 , respectively, and $1 million for the three and nine months ended September 30, 2016 . Amounts billed by PHISCO to Pepco were $1 million and $2 million for the three and nine months ended September 30, 2017 , respectively. Amounts billed by PHISCO to DPL and ACE were $1 million , each, for the nine months ended September 30, 2017 . Pepco, DPL and ACE did not have any ongoing severance plans for the three and nine months ended September 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 and nine months ended September 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 Three Months Ended September 30, 2017 (a) $ 7 $ 7 $ — $ — $ — September 30, 2016 (b) 1 1 — — — Nine Months Ended September 30, 2017 (a) $ 6 $ 6 $ — $ — $ — September 30, 2016 (b) 18 13 3 1 1 _________ (a) Amounts billed by BSC through intercompany allocations for the nine months ended September 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 nine months ended September 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. For the three and nine months ended September 30, 2017 and the three months ended September 30, 2016 , the PHI Merger severance costs were immaterial. For the nine months ended September 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 Nine Months Ended September 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 $8 million , $2 million , $1 million , $1 million , $19 million , $11 million and $10 million , respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the nine months ended September 30, 2016 . PHI, Pepco, DPL and ACE record regulatory assets for merger related integration costs which include a portion of the severance costs in the table above related to the PHI Merger. These regulatory assets are either currently being recovered in rates or are deemed probable of recovery in future rates. See Note 5 - Regulatory Matters for further information. 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) 33 25 1 — — 3 — — — Payments (24 ) (7 ) (1 ) — — (11 ) — — — Balance at September 30, 2017 $ 97 $ 54 $ 3 $ — $ — $ 21 $ — $ — $ — _________ (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)	9 Months Ended
	Sep. 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 nine months ended September 30, 2017 and 2016 : Nine Months Ended September 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 2 2 (55 ) 7 7 (37 ) Amounts reclassified from AOCI (b) 3 — 105 — — 108 Net current-period OCI 5 2 50 7 7 71 Ending balance $ (12 ) $ 6 $ (2,560 ) $ (23 ) $ — $ (2,589 ) Generation (a) Beginning balance $ (19 ) $ 2 $ — $ (30 ) $ (7 ) $ (54 ) OCI before reclassifications 2 — — 7 6 15 Amounts reclassified from AOCI (b) 3 — — — — 3 Net current-period OCI 5 — — 7 6 18 Ending balance $ (14 ) $ 2 $ — $ (23 ) $ (1 ) $ (36 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 Nine Months Ended September 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 (9 ) — (2 ) 3 (5 ) (13 ) Amounts reclassified from AOCI (b) 5 — 104 5 — 114 Net current-period OCI (4 ) — 102 8 (5 ) 101 Ending balance $ (23 ) $ 3 $ (2,463 ) $ (32 ) $ (8 ) $ (2,523 ) Generation (a) Beginning balance $ (21 ) $ 1 $ — $ (40 ) $ (3 ) $ (63 ) OCI before reclassifications (8 ) 1 — 3 1 (3 ) Amounts reclassified from AOCI (b) 5 — — 5 — 10 Net current-period OCI (3 ) 1 — 8 1 7 Ending balance $ (24 ) $ 2 $ — $ (32 ) $ (2 ) $ (56 ) 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 nine months ended September 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 nine months ended September 30, 2017 and 2016 . Three Months Ended September 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 $ 2 $ 2 Interest expense Total before tax 2 2 Tax benefit (1 ) (1 ) Net of tax $ 1 $ 1 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 23 — Net of tax $ (35 ) $ — Total Reclassifications for the period $ (34 ) $ 1 Comprehensive income Nine Months Ended September 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 $ (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) $ 69 $ — Actuarial losses (b) (243 ) — Total before tax (174 ) — Tax benefit 69 — Net of tax $ (105 ) $ — Total Reclassifications $ (108 ) $ (3 ) Comprehensive income Three Months Ended September 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 Gains and (losses) on cash flow hedges Other cash flow hedges $ (3 ) $ (3 ) Interest expense Total before tax (3 ) (3 ) Tax expense 1 1 Net of tax $ (2 ) $ (2 ) Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 19 $ — Actuarial losses (b) (76 ) — Total before tax (57 ) — Tax benefit 22 — Net of tax $ (35 ) $ — Gains and (losses) on foreign currency translation Other $ (5 ) $ (5 ) Other Income and (deductions) Total before tax (5 ) (5 ) Tax expense — — Net of tax $ (5 ) $ (5 ) Comprehensive income Total Reclassifications for the period $ (42 ) $ (7 ) Comprehensive income Nine Months Ended September 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 $ (8 ) $ (8 ) $ — Interest expense Total before tax (8 ) (8 ) — Tax benefit 3 3 — Net of tax $ (5 ) $ (5 ) $ — Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 57 $ — $ — Actuarial losses (b) (227 ) — (1 ) Total before tax (170 ) — (1 ) Tax benefit 66 — — Net of tax $ (104 ) $ — $ (1 ) Gains and (losses) on foreign currency translation Other $ (5 ) $ (5 ) $ — Other income and (deductions) Total before tax (5 ) (5 ) — Tax expense — — — Net of tax $ (5 ) $ (5 ) $ — Total Reclassifications $ (114 ) $ (10 ) $ (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 14 — 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 nine months ended September 30, 2017 and 2016 : Three Months Ended September 30, Nine Months Ended 2017 2016 2017 2016 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 9 $ 7 $ 27 $ 22 Actuarial loss reclassified to periodic benefit cost (32 ) (29 ) (96 ) (88 ) Pension and non-pension postretirement benefit plans valuation adjustment — 1 2 1 Change in unrealized (loss)/gain on cash flow hedges — (1 ) (3 ) 3 Change in unrealized (loss)/gain on equity investments 1 — (2 ) 3 Change in unrealized (loss)/gain on marketable securities — (1 ) (2 ) (1 ) Total $ (22 ) $ (23 ) $ (74 ) $ (60 ) Generation Change in unrealized (loss)/gain on cash flow hedges $ — $ (2 ) $ (3 ) $ 1 Change in unrealized (loss)/gain on equity investments — — (2 ) 3 Change in unrealized gain on marketable securities — — (1 ) — Total $ — $ (2 ) $ (6 ) $ 4 Predecessor PHI January 1, 2016 to March 23, 2016 Pension and non-pension postretirement benefit plans: Actuarial loss reclassified to periodic cost $ —

Earnings Per Share and Equity (

Earnings Per Share and Equity (Exelon)	9 Months Ended
	Sep. 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 September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Exelon Net income attributable to common shareholders $ 824 $ 490 $ 1,899 $ 930 Weighted average common shares outstanding — basic 962 925 941 924 Assumed exercise and/or distributions of stock-based awards 3 2 2 2 Weighted average common shares outstanding — diluted 965 927 943 926 The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was approximately 7 million and 9 million for the three and nine months ended September 30, 2017 , respectively, and 11 million and 12 million for the three and nine months ended September 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 nine months ended September 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 less than 1 million for the three and nine months ended September 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)	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies (All Registrants)	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 September 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) $ 12 2018 6 2019 3 Total $ 21 Commercial Commitments (All Registrants) The Registrants’ commercial commitments as of September 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) $ 1,276 $ 1,193 $ 14 $ 22 $ 2 $ 1 $ 1 $ — $ — Surety bonds (b) 1,206 1,079 20 40 11 21 13 4 4 Financing trust guarantees 378 — 200 178 — — — — — Guaranteed lease residual values (c) 19 — — — — 19 6 7 5 Total commercial commitments $ 2,879 $ 2,272 $ 234 $ 240 $ 13 $ 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 $49 million , $14 million of which is a guarantee by Pepco, $19 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 September 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 2022. • 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 3 sites, 2 of which remediation has been completed and approved by the MDE or the Delaware Department of Natural Resources and Environmental Control. The remaining site is under study and the required cost at the site is not considered material. 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 September 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: September 30, 2017 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 429 $ 327 Generation 76 — ComEd 294 293 PECO 33 32 BGE 3 2 PHI (Successor) 23 — Pepco 21 — DPL 1 — 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. During the third quarter of 2017, ComEd, PECO, BGE and PHI completed an annual study of their future estimated MGP remediation requirements. The study resulted in a $13 million and $2 million increase to environmental liabilities and related regulatory assets for ComEd and PECO, respectively, and no change at BGE and PHI. 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. 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. This further analysis has focused on a partial excavation remedial option. The PRPs have provided a draft Remedial Investigation and Feasibility Study (RI/FS) report to the EPA for its review and comment. The final RI/FS will form the basis of EPA’s selection of a remedy from among the alternatives of a landfill cover, and partial or complete excavation. 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 on going. The estimated cost of the landfill cover remedy (taking into account the current EPA technical requirements incorporated in the third quarter 2017) is approximately $110 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 a landfill cover, which is included in the table above. 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 has been executed by the Parties and lodged with the U.S. District Court. After publication in the Federal Register there will be 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, Generation has elected to be a non-performing cash-out party and following payment of the allocated cost for its share of the clean-up. Generation will have no remaining liability at the site, except for unknown conditions that could manifest themselves after the settlement. The cash-out payment 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 $1 million which has been fully reserved and included in the table above as of September 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 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 the probable liability; such costs would be shared by the 4 identified PRPs. BGE has accrued an appropriate reserve for its share of the estimated liabilities 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 offsite sample testing produced results that were below the cleanup action level established by MDE and no further investigation is required. MDE has provided BGE with the required clean-up levels for the on-site contamination and BGE is moving forward with the necessary remediation as directed by MDE. BGE has established what it believes is an appropriate reserve based upon the information available to date, and this amount is included in the table above. As the remediation proceeds, 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

Supplemental Financial Informat

Supplemental Financial Information (All Registrants)	9 Months Ended
	Sep. 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 nine months ended September 30, 2017 and 2016 . Three Months Ended September 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 $ 159 $ 159 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 59 59 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 44 44 — — — — — — — Non-regulatory agreement units 111 111 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (4 ) (4 ) — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (161 ) (161 ) — — — — — — — Total decommissioning-related activities 208 208 — — — — — — — Investment income 2 1 — — — 1 1 — — Interest income related to uncertain income tax positions 4 — — — — — — — — AFUDC — Equity 17 — 2 2 4 9 6 2 1 Other 6 — 3 — — 3 — 2 — Other, net $ 237 $ 209 $ 5 $ 2 $ 4 $ 13 $ 7 $ 4 $ 1 Nine Months Ended September 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 $ 439 $ 439 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 165 165 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 253 253 — — — — — — — Non-regulatory agreement units 347 347 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (5 ) (5 ) — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (558 ) (558 ) — — — — — — — Total decommissioning-related activities 641 641 — — — — — — — Investment income 6 4 — — — 2 1 — — Interest income related to uncertain income tax positions 3 — — — — — — — — Benefit related to uncertain income tax positions (c) 2 — — — — — — — — AFUDC — Equity 51 — 6 6 12 27 17 5 5 Other 22 3 8 — — 11 4 5 1 Other, net $ 725 $ 648 $ 14 $ 6 $ 12 $ 40 $ 22 $ 10 $ 6 Three Months Ended September 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 $ 57 $ 57 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 35 35 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 155 155 — — — — — — — Non-regulatory agreement units 116 116 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (5 ) (5 ) — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (168 ) (168 ) — — — — — — — Total decommissioning-related activities 190 190 — — — — — — — Investment income (expense) 2 1 — (1 ) — — — — — Interest income related to uncertain income tax positions 8 — — — — — — — — Penalty related to uncertain income tax positions (c) (106 ) — (86 ) — — — — — — AFUDC — Equity 19 — 5 2 5 7 5 1 1 Other 7 (6 ) 1 1 — 12 7 2 1 Other, net $ 120 $ 185 $ (80 ) $ 2 $ 5 $ 19 $ 12 $ 3 $ 2 Successor Predecessor Nine Months Ended September 30, 2016 March 24, 2016 to September 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 $ 181 $ 181 $ — $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 95 95 — — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 286 286 — — — — — — — — Non-regulatory agreement units 216 216 — — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (2 ) (2 ) — — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (380 ) (380 ) — — — — — — — — Total decommissioning-related activities 396 396 — — — — — — — — Investment income (expense) 14 6 — (1 ) 2 — — — 1 — Long-term lease income 4 — — — — — — — — — Interest income related to uncertain income tax positions 13 — — — — 1 — 1 — — Penalty related to uncertain income tax positions (c) (106 ) — (86 ) — — — — — — — AFUDC — Equity 43 — 8 6 14 14 3 5 15 7 Loss on debt extinguishment (3 ) (2 ) — — — — — — — — Other 16 (5 ) 6 1 — 13 6 2 15 (11 ) Other, net $ 377 $ 395 $ (72 ) $ 6 $ 16 $ 28 $ 9 $ 8 $ 31 $ (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. (c) See Note 12 - Income Taxes for discussion of the penalty related to the Tax Court's decision on Exelon's like-kind exchange tax position. The following utility taxes are included in revenues and expenses for the three and nine months ended September 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 September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 245 $ 35 $ 65 $ 35 $ 22 $ 88 $ 83 $ 5 $ — Nine Months Ended September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 682 $ 97 $ 181 $ 95 $ 69 $ 240 $ 226 $ 14 $ — Three Months Ended September 30, 2016 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 255 $ 35 $ 67 $ 40 $ 21 $ 92 $ 87 $ 5 $ — Successor Predecessor Nine Months Ended September 30, 2016 March 24, 2016 to September 30, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Utility taxes $ 624 $ 90 $ 186 $ 106 $ 66 $ 240 $ 14 $ — $ 176 $ 78 Supplemental Cash Flow Information The following tables provide additional information regarding the Registrants’ Consolidated Statements of Cash Flows for the nine months ended September 30, 2017 and 2016 . Nine Months Ended September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Depreciation, amortization and accretion Property, plant and equipment (a) $ 2,416 $ 1,010 $ 579 $ 194 $ 233 $ 342 $ 153 $ 92 $ 66 Amortization of regulatory assets (a) 355 — 52 19 115 169 89 32 47 Amortization of intangible assets, net (a) 43 36 — — — — — — — Amortization of energy contract assets and liabilities (b) 19 19 — — — — — — — Nuclear fuel (c) 816 816 — — — — — — — ARO accretion (d) 350 350 — — — — — — — Total depreciation, amortization and accretion $ 3,999 $ 2,231 $ 631 $ 213 $ 348 $ 511 $ 242 $ 124 $ 113 Successor Predecessor Nine Months Ended September 30, 2016 March 24, 2016 to September 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) $ 2,490 $ 1,297 $ 524 $ 181 $ 223 $ 128 $ 82 $ 61 $ 215 $ 94 Amortization of regulatory assets (a) 293 — 49 20 84 93 38 69 140 58 Amortization of intangible assets, net (a) 38 32 — — — — — — — — Amortization of energy contract assets and liabilities (b) (7 ) (7 ) — — — — — — — — Nuclear fuel (c) 862 862 — — — — — — — — ARO accretion (d) 333 332 1 — — — — — — — Total depreciation, amortization and accretion $ 4,009 $ 2,516 $ 574 $ 201 $ 307 $ 221 $ 120 $ 130 $ 355 $ 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. Nine Months Ended September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 482 $ 170 $ 131 $ 21 $ 47 $ 72 $ 19 $ 10 $ 10 Loss from equity method investments 26 26 — — — — — — — Provision for uncollectible accounts 103 31 25 17 4 26 11 1 14 Stock-based compensation costs 76 — — — — — — — — Other decommissioning-related activity (a) (213 ) (213 ) — — — — — — — Energy-related options (b) 15 15 — — — — — — — Amortization of regulatory asset related to debt costs 7 — 3 1 — 3 1 1 1 Amortization of rate stabilization deferral (7 ) — — — 7 (14 ) (12 ) (2 ) — Amortization of debt fair value adjustment (13 ) (9 ) — — — (4 ) — — — Discrete impacts from EIMA and FEJA (c) (61 ) — (61 ) — — — — — — Amortization of debt costs 57 33 3 1 1 1 1 — — Provision for excess and obsolete inventory 52 50 1 — — 1 — 1 — Merger-related commitments (d) — — — — — (8 ) (6 ) (2 ) — Severance costs 33 25 — — — 3 — — — Other 46 4 10 (2 ) (7 ) (14 ) (6 ) (3 ) (4 ) Total other non-cash operating activities $ 603 $ 132 $ 112 $ 38 $ 52 $ 66 $ 8 $ 6 $ 21 Non-cash investing and financing activities: Change in capital expenditures not paid $ (101 ) $ 20 $ (79 ) $ (29 ) $ 16 $ (6 ) $ 7 $ 14 $ (18 ) Fair value of pension obligation transferred in connection with the FitzPatrick acquisition — 33 — — — — — — — Change in PPE related to ARO update (141 ) (141 ) — — — — — — — Indemnification of like-kind exchange position (g) — — 21 — — — — — — Non-cash financing of capital projects 16 16 — — — — — — — Dividends on stock compensation 5 — — — — — — — — Dissolution of financing trust due to long-term debt retirement 8 — — — 8 — — — — Fair value adjustment of long-term debt due to retirement (5 ) — — — — — — — — Successor Predecessor Nine Months Ended September 30, 2016 March 24, 2016 to September 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 $ 458 $ 163 $ 124 $ 25 $ 50 $ 24 $ 13 $ 11 $ 58 $ 23 Loss from equity method investments 15 16 — — — — — — — — Provision for uncollectible accounts 107 14 31 24 12 15 12 18 27 16 Stock-based compensation costs 88 — — — — — — — — 3 Other decommissioning-related activity (a) (237 ) (237 ) — — — — — — — — Energy-related options (b) (20 ) (20 ) — — — — — — — — Amortization of regulatory asset related to debt costs 7 — 3 1 — 2 — 1 2 1 Amortization of rate stabilization deferral 62 — — — 62 3 3 — — 5 Amortization of debt fair value adjustment (9 ) (9 ) — — — — — — — — Discrete impacts from EIMA (c) (36 ) — (36 ) — — — — — — — Amortization of debt costs 26 12 (3 ) 2 3 — — — — — Provision for excess and obsolete inventory 74 70 4 — — 1 1 1 — 1 Merger-related commitments (d)(e) 508 3 — — — 125 73 110 308 — Severance costs 130 57 — — — — — — 53 — Asset retirement costs — — — — — — 5 2 — — Lower of cost or net realizable value inventory adjustment 36 36 — — — — — — — — Other 15 24 (1 ) (3 ) (18 ) (2 ) (8 ) (5 ) (7 ) (3 ) Total other non-cash operating activities $ 1,224 $ 129 $ 122 $ 49 $ 109 $ 168 $ 99 $ 138 $ 441 $ 46 Non-cash investing and financing activities: Change in capital expenditures not paid $ (338 ) $ (289 ) $ (42 ) $ (4 ) $ 17 $ 15 $ (10 ) $ 2 $ (5 ) $ 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) — — — — — — — — 129 — 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 476 476 — — — — — — — — Indemnification of like-kind exchange position (g) — — 157 — — — — — — — Non-cash financing of capital projects 84 84 — — — — — — — — 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 12 — 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 September 30, 2017 and December 31, 2016 . Successor September 30, 2017 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Property, plant and equipment: Accumulated depreciation and amortization $ 20,591 (a) $ 11,193 (a) $ 4,191 $ 3,366 $ 3,351 $ 448 $ 3,171 $ 1,231 $ 1,060 Accounts receivable: Allowance for uncollectible accounts $ 339 $ 111 $ 72 $ 57 $ 25 $ 74 $ 29 $ 17 $ 28 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 $3,303 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 September 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 September 30, 2017 of $12 million consists of $3 million and $9 million for 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 September 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)	9 Months Ended
	Sep. 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 nine months ended September 30, 2017 and 2016 is as follows: Three Months Ended September 30, 2017 and 2016 Successor Generation (a) ComEd PECO BGE PHI (b) Other (c) Intersegment Exelon Operating revenues (d) : 2017 Competitive businesses electric revenues $ 4,042 $ — $ — $ — $ — $ — $ (295 ) $ 3,747 Competitive businesses natural gas revenues 460 — — — — — — 460 Competitive businesses other revenues 249 — — — — — — 249 Rate-regulated electric revenues — 1,571 662 658 1,280 — (7 ) 4,164 Rate-regulated natural gas revenues — — 53 80 18 — (2 ) 149 Shared service and other revenues — — — — 12 446 (458 ) — 2016 Competitive businesses electric revenues $ 4,322 $ — $ — $ — $ — $ — $ (499 ) $ 3,823 Competitive businesses natural gas revenues 326 — — — — — — 326 Competitive businesses other revenues 387 — — — — — (1 ) 386 Rate-regulated electric revenues — 1,497 740 735 1,366 — (8 ) 4,330 Rate-regulated natural gas revenues — — 48 77 17 — (5 ) 137 Shared service and other revenues — — — — 11 362 (373 ) — Intersegment revenues (e) : 2017 $ 294 $ 3 $ 2 $ 3 $ 12 $ 445 $ (759 ) $ — 2016 500 4 2 7 11 362 (885 ) 1 Net income (loss): 2017 $ 348 $ 189 $ 112 $ 62 $ 153 $ 3 $ — $ 867 2016 271 37 122 56 166 (125 ) (1 ) 526 Total assets: September 30, 2017 $ 47,744 $ 29,649 $ 11,480 $ 8,923 $ 21,301 $ 10,662 $ (11,286 ) $ 118,473 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 September 30, 2017 include revenue from sales to PECO of $31 million , sales to BGE of $98 million , sales to Pepco of $57 million , sales to DPL of $47 million , and sales to ACE of $7 million in the Mid-Atlantic region, and sales to ComEd of $54 million in the Midwest region. For the three months ended September 30, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $91 million , sales to BGE of $183 million , sales to Pepco of $128 million , sales to DPL of $63 million , and sales to ACE of $15 million in the Mid-Atlantic region, and sales to ComEd of $20 million in the Midwest region. (b) Amounts included represent activity for PHI's successor period, three months ended September 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 19 — Supplemental Financial Information for total utility taxes for the three months ended September 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 September 30, 2017 - Successor Rate-regulated electric revenues $ 604 $ 309 $ 370 $ — $ (3 ) $ 1,280 Rate-regulated natural gas revenues — 18 — — — 18 Shared service and other revenues — — — 12 — 12 Three Months Ended September 30, 2016 - Successor Rate-regulated electric revenues $ 635 $ 314 $ 421 $ — $ (4 ) $ 1,366 Rate-regulated natural gas revenues — 17 — — — 17 Shared service and other revenues — — — 11 — 11 Intersegment revenues: Three Months Ended September 30, 2017 - Successor $ 1 $ 2 $ — $ 13 $ (4 ) $ 12 Three Months Ended September 30, 2016 - Successor 1 2 1 11 (4 ) 11 Net income (loss): Three Months Ended September 30, 2017 - Successor $ 87 $ 31 $ 41 $ (18 ) $ 12 $ 153 Three Months Ended September 30, 2016 - Successor 79 44 47 (15 ) 11 166 Total assets: September 30, 2017 - Successor $ 7,775 $ 4,276 $ 3,510 $ 10,724 $ (4,984 ) $ 21,301 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 19 — Supplemental Financial Information for total utility taxes for the three months ended September 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 September 30, 2017 Three Months Ended September 30, 2016 Revenues (a) Intersegment Total Revenues (a) Intersegment Total Mid-Atlantic $ 1,421 $ 11 $ 1,432 $ 1,813 $ (13 ) $ 1,800 Midwest 1,049 (11 ) 1,038 1,163 1 1,164 New England 482 (1 ) 481 455 (4 ) 451 New York 434 (6 ) 428 331 (8 ) 323 ERCOT 308 6 314 289 6 295 Other Power Regions 348 (13 ) 335 271 (33 ) 238 Total Revenues for Reportable Segments 4,042 (14 ) 4,028 4,322 (51 ) 4,271 Other (b) 709 14 723 713 51 764 Total Generation Consolidated Operating Revenues $ 4,751 $ — $ 4,751 $ 5,035 $ — $ 5,035 _________ (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 $13 million and $21 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 September 30, 2017 and 2016 , respectively, unrealized mark-to-market gain of $52 million and $187 million for the three months ended September 30, 2017 and 2016 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 RNF (a) Intersegment RNF Total RNF RNF (a) Intersegment RNF Total RNF Mid-Atlantic $ 817 $ 38 $ 855 $ 881 $ 6 $ 887 Midwest 697 — 697 782 (1 ) 781 New England 151 (6 ) 145 170 (10 ) 160 New York 296 — 296 195 (1 ) 194 ERCOT 229 (111 ) 118 144 (51 ) 93 Other Power Regions 118 (50 ) 68 143 (66 ) 77 Total Revenues net of purchased power and fuel for Reportable Segments 2,308 (129 ) 2,179 2,315 (123 ) 2,192 Other (b) 112 129 241 131 123 254 Total Generation Revenues net of purchased power and fuel expense $ 2,420 $ — $ 2,420 $ 2,446 $ — $ 2,446 _________ (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 $19 million and $22 million decrease to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the three months ended September 30, 2017 and 2016 , respectively, unrealized mark-to-market gains of $73 million and $88 million for the three months ended September 30, 2017 and 2016 , respectively, accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 7 - Early Nuclear Plant Retirements of the Combined Notes to Consolidated Financial Statements of $6 million and $28 million decrease to revenue net of purchased power and fuel expense for the three months ended September 30, 2017 and 2016, respectively, and the elimination of intersegment revenue net of purchased power and fuel expense. Nine Months Ended September 30, 2017 and 2016 Successor Generation (a) ComEd PECO BGE PHI (b) Other (c) Intersegment Exelon Operating revenues (d) : 2017 Competitive businesses electric revenues $ 11,485 $ — $ — $ — $ — $ — $ (888 ) $ 10,597 Competitive businesses natural gas revenues 1,807 — — — — — — 1,807 Competitive businesses other revenues 520 — — — — — — 520 Rate-regulated electric revenues — 4,227 1,802 1,895 3,417 — (23 ) 11,318 Rate-regulated natural gas revenues — — 339 468 105 — (6 ) 906 Shared service and other revenues — — — — 35 1,316 (1,350 ) 1 2016 Competitive businesses electric revenues $ 11,677 $ — $ — $ — $ — $ — $ (1,118 ) $ 10,559 Competitive businesses natural gas revenues 1,515 — — — — — — 1,515 Competitive businesses other revenues 171 — — — — — (2 ) 169 Rate-regulated electric revenues — 4,031 1,971 1,998 2,485 — (24 ) 10,461 Rate-regulated natural gas revenues — — 322 423 46 — (10 ) 781 Shared service and other revenues — — — — 34 1,166 (1,199 ) 1 Intersegment revenues (e) : 2017 $ 888 $ 12 $ 5 $ 12 $ 35 $ 1,312 $ (2,262 ) $ 2 2016 1,121 12 5 16 34 1,166 (2,351 ) 3 Net income (loss): 2017 $ 491 $ 447 $ 327 $ 231 $ 359 $ 58 $ (2 ) $ 1,911 2016 556 297 346 191 (91 ) (340 ) (3 ) 956 _________ (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 nine months ended September 30, 2017 include revenue from sales to PECO of $111 million , sales to BGE of $330 million , sales to Pepco of $209 million , sales to DPL of $138 million , and sales to ACE of $23 million in the Mid-Atlantic region, and sales to ComEd of $77 million in the Midwest region. For the nine months ended September 30, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $234 million and sales to BGE of $489 million in the Mid-Atlantic region, and sales to ComEd of $38 million in the Midwest region. For the Successor period of March 24, 2016 to September 30, 2016 , intersegment revenues for Generation include revenue from sales to Pepco of $223 million , sales to DPL of $109 million , and sales to ACE of $28 million in the Mid-Atlantic region. (b) Amounts included represent activity for PHI's successor period, nine months ended September 30, 2017 and March 24, 2016 through September 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 19 — Supplemental Financial Information for total utility taxes for the nine months ended September 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) : Nine Months Ended September 30, 2017 - Successor Rate-regulated electric revenues $ 1,649 $ 866 $ 915 $ — $ (13 ) $ 3,417 Rate-regulated natural gas revenues — 105 — — — 105 Shared service and other revenues — — — 37 (2 ) 35 March 24, 2016 to September 30, 2016 - Successor Rate-regulated electric revenues $ 1,184 $ 593 $ 714 $ 3 $ (9 ) $ 2,485 Rate-regulated natural gas revenues — 46 — — — 46 Shared service and other revenues — — — 34 — 34 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: Nine Months Ended September 30, 2017 - Successor $ 4 $ 6 $ 2 $ 37 $ (14 ) $ 35 March 24, 2016 to September 30, 2016 - Successor 2 4 2 35 (9 ) 34 January 1, 2016 to March 23, 2016 - Predecessor 1 2 1 — (4 ) — Net income (loss): Nine Months Ended September 30, 2017 - Successor $ 188 $ 107 $ 77 $ (48 ) $ 35 $ 359 March 24, 2016 to September 30, 2016 - Successor (12 ) (42 ) (55 ) (16 ) 34 (91 ) 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 19 — Supplemental Financial Information for total utility taxes for the nine months ended September 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: Nine Months Ended September 30, 2017 Nine Months Ended September 30, 2016 Revenues (a) Intersegment Total Revenues (a) Intersegment Total Mid-Atlantic $ 4,207 $ 15 $ 4,222 $ 4,776 $ (40 ) $ 4,736 Midwest 3,158 (17 ) 3,141 3,330 13 3,343 New England 1,469 (8 ) 1,461 1,278 (6 ) 1,272 New York 1,095 (14 ) 1,081 906 (33 ) 873 ERCOT 749 4 753 659 6 665 Other Power Regions 807 (28 ) 779 728 (42 ) 686 Total Revenues for Reportable Segments 11,485 (48 ) 11,437 11,677 (102 ) 11,575 Other (b) 2,327 48 2,375 1,686 102 1,788 Total Generation Consolidated Operating Revenues $ 13,812 $ — $ 13,812 $ 13,363 $ — $ 13,363 _________ (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 $30 million and $10 million decrease to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the nine months ended September 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $47 million and $366 million for the nine months ended September 30, 2017 and 2016 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Nine Months Ended September 30, 2017 Nine Months Ended September 30, 2016 RNF from external customers (a) Intersegment RNF Total RNF RNF from external customers (a) Intersegment RNF Total RNF Mid-Atlantic $ 2,330 $ 81 $ 2,411 $ 2,541 $ 15 $ 2,556 Midwest 2,129 11 2,140 2,225 4 2,229 New England 423 (20 ) 403 373 (23 ) 350 New York 679 (1 ) 678 607 (15 ) 592 ERCOT 446 (188 ) 258 335 (104 ) 231 Other Power Regions 359 (139 ) 220 357 (104 ) 253 Total Revenues net of purchased power and fuel expense for Reportable Segments 6,366 (256 ) 6,110 6,438 (227 ) 6,211 Other (b) 160 256 416 316 227 543 Total Generation Revenues net of purchased power and fuel expense $ 6,526 $ — $ 6,526 $ 6,754 $ — $ 6,754 _________ (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 $41 million and $15 million decrease to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the nine months ended September 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $161 million and $113 million for the nine months ended September 30, 2017 and 2016 , respectively, accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 7 - Early Nuclear Plant Retirements of the Combined Notes to Consolidated Financial Statements of $8 million and $38 million decrease to revenue net of purchased power and fuel expense for the nine months ended September 30, 2017 and 2016, respectively, and the elimination of intersegment revenue net of purchased power and fuel expense.

Earnings Per Share and Equity E

Earnings Per Share and Equity Earnings Per Share and Equity (Policies)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
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.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2017
Variable Interest Entity [Abstract]
Schedule of Variable Interest Entities	As of September 30, 2017 and December 31, 2016 , these assets and liabilities primarily consisted of the following: September 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 $ 130 $ 130 $ — $ — $ 150 $ 150 $ — $ — $ — Restricted cash 85 76 9 9 59 27 23 9 9 Accounts receivable, net Customer 139 139 — — 371 371 — — — Other 25 25 — — 48 48 — — — Mark-to-market derivatives assets — — — — 31 31 — — — Inventory Materials and supplies 196 196 — — 199 199 — — — Other current assets 56 52 4 — 50 44 — 5 — Total current assets 631 618 13 9 908 870 23 14 9 Property, plant and equipment, net 6,213 6,213 — — 5,415 5,415 — — — Nuclear decommissioning trust funds 2,415 2,415 — — 2,185 2,185 — — — Goodwill — — — — 47 47 — — — Mark-to-market derivative assets — — — — 23 23 — — — Other noncurrent assets 261 231 30 22 315 277 3 35 23 Total noncurrent assets 8,889 8,859 30 22 7,985 7,947 3 35 23 Total assets $ 9,520 $ 9,477 $ 43 $ 31 $ 8,893 $ 8,817 $ 26 $ 49 $ 32 Long-term debt due within one year $ 182 $ 146 $ 36 $ 32 $ 181 $ 99 $ 41 $ 40 $ 35 Accounts payable 104 104 — — 269 269 — — — Accrued expenses 90 89 1 1 119 116 1 2 2 Mark-to-market derivative liabilities — — — — 60 60 — — — Unamortized energy contract liabilities 17 17 — — 15 15 — — — Other current liabilities 11 11 — — 30 30 — — — Total current liabilities 404 367 37 33 674 589 42 42 37 Long-term debt 1,172 1,097 75 67 641 540 — 101 89 Asset retirement obligations 2,009 2,009 — — 1,904 1,904 — — — Pension obligation (c) — — — — 9 9 — — — Unamortized energy contract liabilities 9 9 — — 22 22 — — — Other noncurrent liabilities 94 94 — — 106 106 — — — Total noncurrent liabilities 3,284 3,209 75 67 2,682 2,581 — 101 89 Total liabilities $ 3,688 $ 3,576 $ 112 $ 100 $ 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 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 14 - Retirement Benefits for additional details. The following tables present summary information about Exelon's and Generation’s significant unconsolidated VIE entities: September 30, 2017 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 635 $ 519 $ 1,154 Total liabilities (a) 39 229 268 Exelon's ownership interest in VIE (a) — 259 259 Other ownership interests in VIE (a) 596 31 627 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 259 259 Contract intangible asset 9 — 9 Debt and payment guarantees — — — Net assets pledged for Zion Station decommissioning (b) 4 — 4 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 $57 million and $113 million as of September 30, 2017 and December 31, 2016 , respectively; offset by payables to ZionSolutions LLC of $53 million and $104 million as of September 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 13 - Nuclear Decommissioning for additional details. The carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in the Registrants' consolidated financial statements at September 30, 2017 and December 31, 2016 are as follows: September 30, 2017 December 31, 2016 Successor Successor Exelon (a) Generation PHI (a) ACE Exelon (a)(b) Generation BGE PHI (a) ACE Current assets $ 657 $ 644 $ 13 $ 9 $ 954 $ 916 $ 23 $ 14 $ 9 Noncurrent assets 9,252 9,222 30 22 8,563 8,525 3 35 23 Total assets $ 9,909 $ 9,866 $ 43 $ 31 $ 9,517 $ 9,441 $ 26 $ 49 $ 32 Current liabilities $ 404 $ 367 $ 37 $ 33 $ 885 $ 802 $ 42 $ 42 $ 37 Noncurrent liabilities 3,290 3,215 75 67 2,713 2,612 — 101 89 Total liabilities $ 3,694 $ 3,582 $ 112 $ 100 $ 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.

Mergers, Acquisitions and Dispo

Mergers, Acquisitions and Dispositions (Tables)	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	Cash paid for purchase price $ 110 Cash paid for net cost reimbursement 125 Nuclear fuel transfer 54 Total consideration transferred $ 289 Identifiable assets acquired and liabilities assumed Current assets $ 60 Property, plant and equipment 298 Nuclear decommissioning trust funds 807 Other assets (a) 114 Total assets $ 1,279 Current liabilities $ 6 Nuclear decommissioning ARO 444 Pension and OPEB obligations 33 Deferred income taxes 149 Spent nuclear fuel obligation 110 Other liabilities 15 Total liabilities $ 757 Total net identifiable assets, at fair value $ 522 Bargain purchase gain (after-tax) $ 233 _________ (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. 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 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 final acquisition-date fair value of the consideration transferred and the assets and liabilities assumed for the ConEdison Solutions acquisition by Generation: Total consideration transferred $ 257 Identifiable assets acquired and liabilities assumed Working capital assets $ 204 Property, plant and equipment 2 Mark-to-market derivative assets 6 Unamortized energy contract assets 100 Customer relationships 9 Other assets 1 Total assets $ 322 Mark-to-market derivative liabilities $ 65 Total liabilities $ 65 Total net identifiable assets, at fair value $ 257
Business Combination, Separately Recognized Transactions [Table Text Block]	The total purchase price consideration of approximately $7.1 billion for the PHI Merger consisted of cash paid to PHI shareholders, cash paid for PHI preferred securities and cash paid for PHI stock-based compensation equity awards as follows: (In millions of dollars, except per share data) Total Consideration Cash paid to PHI shareholders at $27.25 per share (254 million shares outstanding at March 23, 2016) $ 6,933 Cash paid for PHI preferred stock 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. Three Months Ended Nine Months Ended Acquisition, Integration and Financing Costs (a) 2017 2016 2017 2016 Exelon $ (8 ) $ 20 $ 10 $ 123 Generation 5 9 18 29 ComEd (b) — — 1 (6 ) PECO 1 1 3 3 BGE (c) 1 1 3 (3 ) Pepco (d) (8 ) 3 (6 ) 26 DPL (e) 1 2 (6 ) 18 ACE (f) (8 ) 2 (6 ) 17 Successor Predecessor Acquisition, Integration and Financing Costs (a) Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 Nine Months Ended September 30, 2017 March 24, 2016 to September 30, 2016 January 1, 2016 to March 23, 2016 PHI (g) $ (15 ) $ 7 $ (17 ) $ 63 $ 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) For the nine months ended September 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. (c) For the nine months ended September 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. (d) For the three and nine months ended September 30, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. For the nine months ended September 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $10 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. (e) For the nine months ended September 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 nine months ended September 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. (f) For the three and nine months ended September 30, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at ACE that have been deferred and recorded as a regulatory asset for anticipated recovery. See Note 5 — Regulatory Matters for more information. (g) For the three and nine months ended September 30, 2017 , includes the reversal of previously incurred acquisition, integration and financing costs of $16 million and $24 million , respectively, incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. For the Successor period March 24, 2016 to September 30, 2016 , includes the reversal of previously incurred acquisition, integration and financing costs of $13 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 current impact of PHI, including its unregulated businesses, on Exelon's Consolidated Statements of Operations and Comprehensive Income includes: Three Months Ended Nine Months Ended 2017 2016 2017 2016 Operating revenues $ 1,347 $ 1,437 $ 3,679 $ 2,656 Net income (loss) 176 169 382 (92 )
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 Nine Months Ended Year Ended December 31, 2016 (a) 2016 (a) 2016 (b) Total operating revenues $ 9,002 $ 24,468 $ 32,342 Net income attributable to common shareholders 501 1,346 1,562 Basic earnings per share $ 0.54 $ 1.46 $ 1.69 Diluted earnings per share 0.54 1.45 1.69 _________ (a) The amounts above include adjustments for non-recurring costs directly related to the merger of $20 million and $660 million for the three and nine months ended September 30, 2016 , respectively, and intercompany revenue of $171 million for the nine months ended September 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)	9 Months Ended
	Sep. 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 2017 annual 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. The following table illustrates our authorized amounts capitalized for ratemaking purposes related to earnings on shareholders’ investment that are not recognized for financial reporting purposes on our Consolidated Balance Sheets. These amounts will be recognized as revenues in our Consolidated Statements of Operations and Comprehensive Income in the periods they are billable to our customers. Exelon ComEd (a) PECO BGE (b) PHI Pepco (c) DPL (c) ACE September 30, 2017 $ 71 $ 7 $ — $ 54 $ 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 primarily relate to earnings on shareholders' investment on its AMI Programs. (c) 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.
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 September 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 September 30, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory assets Pension and other postretirement benefits (a) $ 4,020 $ — $ — $ — $ — $ — $ — $ — Deferred income taxes (b) 2,423 347 1,678 100 298 195 45 58 AMI programs 660 159 40 219 242 163 79 — Under-recovered distribution service costs (c) 256 256 — — — — — — Energy efficiency costs 78 78 — — — — — — Debt costs 120 38 1 12 75 16 8 5 Fair value of long-term debt 773 — — — 632 — — — Fair value of PHI's unamortized energy contracts 830 — — — 830 — — — Severance 2 — — 2 — — — — Asset retirement obligations 108 73 22 13 — — — — MGP remediation costs 300 277 23 — — — — — Under-recovered uncollectible accounts 70 60 — — 10 — — 10 Renewable energy 277 277 — — — — — — Energy and transmission programs (d)(e)(f)(g)(h)(i) 65 3 — 26 36 6 9 21 Deferred storm costs 31 — — — 31 9 5 17 Electric generation-related regulatory asset 3 — — 3 — — — — Energy efficiency and demand response programs 599 — 1 284 314 233 81 — Merger integration costs (j)(k)(l)(m) 47 — — 7 40 20 11 9 Under-recovered revenue decoupling (n) 72 — — 34 38 33 5 — COPCO acquisition adjustment 6 — — — 6 — 6 — Workers compensation and long-term disability cost 33 — — — 33 33 — — Vacation accrual 38 — 14 — 24 — 14 10 Securitized stranded costs 93 — — — 93 — — 93 CAP arrearage 9 — 9 — — — — — Removal costs 518 — — — 518 144 98 277 Other 71 6 21 5 40 28 8 4 Total regulatory assets 11,502 1,574 1,809 705 3,260 880 369 504 Less: current portion 1,264 187 36 208 568 181 69 87 Total noncurrent regulatory assets $ 10,238 $ 1,387 $ 1,773 $ 497 $ 2,692 $ 699 $ 300 $ 417 Successor September 30, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory liabilities Other postretirement benefits $ 41 $ — $ — $ — $ — $ — $ — $ — Nuclear decommissioning 2,971 2,438 533 — — — — — Removal costs 1,588 1,337 — 119 132 22 110 — Deferred rent 37 — — — 37 — — — Energy efficiency and demand response programs 62 33 29 — — — — — DLC program costs 8 — 8 — — — — — Electric distribution tax repairs 50 — 50 — — — — — Gas distribution tax repairs 14 — 14 — — — — — Energy and transmission programs (d)(e)(f)(g)(h)(i) 139 54 68 — 17 3 9 5 Renewable portfolio standards costs 46 46 — — — — — — Zero emission credit costs 71 71 — — — — — — Other 75 5 17 28 25 1 9 13 Total regulatory liabilities 5,102 3,984 719 147 211 26 128 18 Less: current portion 553 249 159 63 65 5 42 18 Total noncurrent regulatory liabilities $ 4,549 $ 3,735 $ 560 $ 84 $ 146 $ 21 $ 86 $ — 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)(l)(m) 25 — — 10 15 11 4 — Under-recovered revenue decoupling (n) 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 noncurrent 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 noncurrent regulatory liabilities $ 4,187 $ 3,369 $ 517 $ 110 $ 158 $ 20 $ 97 $ — _________ (a) As of September 30, 2017 and December 31, 2016 , the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $969 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 September 30, 2017 , includes transmission-related income tax regulatory assets that require FERC approval separate from the transmission formula rate of $73 million , $42 million , $34 million , $23 million and $21 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 September 30, 2017 , ComEd’s regulatory asset of $256 million was comprised of $200 million for the 2015 - 2017 annual reconciliations and $56 million related to significant one-time events including $11 million of deferred storm costs, $7 million of Constellation and PHI merger and integration related costs, $6 million of emerald ash borer costs, and $32 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 — Mergers, Acquisitions and Dispositions of the Exelon 2016 Form 10-K for further information. (d) As of September 30, 2017 , ComEd’s regulatory liability of $54 million included $22 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 September 30, 2017 , PECO's regulatory liability of $68 million included $34 million related to over-recovered costs under the DSP program, $21 million related to the over-recovered natural gas costs under the PGC and $13 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 September 30, 2017 , BGE's regulatory asset of $26 million included $5 million related to under-recovered electric energy costs, $14 million related to under-recovered natural gas costs, $3 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $4 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 September 30, 2017 , Pepco's regulatory asset of $6 million included $3 million of transmission costs recoverable through its FERC approved formula rate and $3 million of under-recovered electric energy costs. As of September 30, 2017 , Pepco's regulatory liability of $3 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 September 30, 2017 , DPL's regulatory asset of $9 million included $4 million of transmission costs recoverable through its FERC approved formula rate and $5 million related to under-recovered electric energy costs. As of September 30, 2017 , DPL's regulatory liability of $9 million related to over-recovered electric energy costs. 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 September 30, 2017 , ACE's regulatory asset of $21 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $10 million of under-recovered electric energy costs. As of September 30, 2017 , ACE's regulatory liability of $5 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 September 30, 2017 and December 31, 2016 , BGE's regulatory asset of $7 million and $10 million , respectively, included $5 million and $6 million , respectively, of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order. (k) As of September 30, 2017 , Pepco’s regulatory asset of $20 million represents previously incurred PHI acquisition costs, including $11 million authorized for recovery in Maryland and $9 million expected to be recovered in the District of Columbia service territory. As of December 31, 2016 , Pepco's regulatory asset of $11 million represents previously incurred PHI acquisition costs authorized for recovery in Maryland. (l) As of September 30, 2017 , DPL’s regulatory asset of $11 million represents previously incurred PHI acquisition costs, including $4 million authorized for recovery in Maryland, $5 million authorized for recovery in Delaware electric rates, and $2 million expected to be recovered in electric and gas 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 the Maryland service territory. (m) As of September 30, 2017 , ACE’s regulatory asset of $9 million represents previously incurred PHI acquisition costs expected to be recovered in the New Jersey service territory. (n) Represents the electric and natural gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of September 30, 2017 , BGE had a regulatory asset of $24 million related to under-recovered electric revenue decoupling and $10 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 September 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 September 30, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory assets Pension and other postretirement benefits (a) $ 4,020 $ — $ — $ — $ — $ — $ — $ — Deferred income taxes (b) 2,423 347 1,678 100 298 195 45 58 AMI programs 660 159 40 219 242 163 79 — Under-recovered distribution service costs (c) 256 256 — — — — — — Energy efficiency costs 78 78 — — — — — — Debt costs 120 38 1 12 75 16 8 5 Fair value of long-term debt 773 — — — 632 — — — Fair value of PHI's unamortized energy contracts 830 — — — 830 — — — Severance 2 — — 2 — — — — Asset retirement obligations 108 73 22 13 — — — — MGP remediation costs 300 277 23 — — — — — Under-recovered uncollectible accounts 70 60 — — 10 — — 10 Renewable energy 277 277 — — — — — — Energy and transmission programs (d)(e)(f)(g)(h)(i) 65 3 — 26 36 6 9 21 Deferred storm costs 31 — — — 31 9 5 17 Electric generation-related regulatory asset 3 — — 3 — — — — Energy efficiency and demand response programs 599 — 1 284 314 233 81 — Merger integration costs (j)(k)(l)(m) 47 — — 7 40 20 11 9 Under-recovered revenue decoupling (n) 72 — — 34 38 33 5 — COPCO acquisition adjustment 6 — — — 6 — 6 — Workers compensation and long-term disability cost 33 — — — 33 33 — — Vacation accrual 38 — 14 — 24 — 14 10 Securitized stranded costs 93 — — — 93 — — 93 CAP arrearage 9 — 9 — — — — — Removal costs 518 — — — 518 144 98 277 Other 71 6 21 5 40 28 8 4 Total regulatory assets 11,502 1,574 1,809 705 3,260 880 369 504 Less: current portion 1,264 187 36 208 568 181 69 87 Total noncurrent regulatory assets $ 10,238 $ 1,387 $ 1,773 $ 497 $ 2,692 $ 699 $ 300 $ 417 Successor September 30, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Regulatory liabilities Other postretirement benefits $ 41 $ — $ — $ — $ — $ — $ — $ — Nuclear decommissioning 2,971 2,438 533 — — — — — Removal costs 1,588 1,337 — 119 132 22 110 — Deferred rent 37 — — — 37 — — — Energy efficiency and demand response programs 62 33 29 — — — — — DLC program costs 8 — 8 — — — — — Electric distribution tax repairs 50 — 50 — — — — — Gas distribution tax repairs 14 — 14 — — — — — Energy and transmission programs (d)(e)(f)(g)(h)(i) 139 54 68 — 17 3 9 5 Renewable portfolio standards costs 46 46 — — — — — — Zero emission credit costs 71 71 — — — — — — Other 75 5 17 28 25 1 9 13 Total regulatory liabilities 5,102 3,984 719 147 211 26 128 18 Less: current portion 553 249 159 63 65 5 42 18 Total noncurrent regulatory liabilities $ 4,549 $ 3,735 $ 560 $ 84 $ 146 $ 21 $ 86 $ — 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)(l)(m) 25 — — 10 15 11 4 — Under-recovered revenue decoupling (n) 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 noncurrent 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 noncurrent regulatory liabilities $ 4,187 $ 3,369 $ 517 $ 110 $ 158 $ 20 $ 97 $ — _________ (a) As of September 30, 2017 and December 31, 2016 , the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $969 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 September 30, 2017 , includes transmission-related income tax regulatory assets that require FERC approval separate from the transmission formula rate of $73 million , $42 million , $34 million , $23 million and $21 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 September 30, 2017 , ComEd’s regulatory asset of $256 million was comprised of $200 million for the 2015 - 2017 annual reconciliations and $56 million related to significant one-time events including $11 million of deferred storm costs, $7 million of Constellation and PHI merger and integration related costs, $6 million of emerald ash borer costs, and $32 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 — Mergers, Acquisitions and Dispositions of the Exelon 2016 Form 10-K for further information. (d) As of September 30, 2017 , ComEd’s regulatory liability of $54 million included $22 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 September 30, 2017 , PECO's regulatory liability of $68 million included $34 million related to over-recovered costs under the DSP program, $21 million related to the over-recovered natural gas costs under the PGC and $13 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 September 30, 2017 , BGE's regulatory asset of $26 million included $5 million related to under-recovered electric energy costs, $14 million related to under-recovered natural gas costs, $3 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $4 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 September 30, 2017 , Pepco's regulatory asset of $6 million included $3 million of transmission costs recoverable through its FERC approved formula rate and $3 million of under-recovered electric energy costs. As of September 30, 2017 , Pepco's regulatory liability of $3 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 September 30, 2017 , DPL's regulatory asset of $9 million included $4 million of transmission costs recoverable through its FERC approved formula rate and $5 million related to under-recovered electric energy costs. As of September 30, 2017 , DPL's regulatory liability of $9 million related to over-recovered electric energy costs. 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 September 30, 2017 , ACE's regulatory asset of $21 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $10 million of under-recovered electric energy costs. As of September 30, 2017 , ACE's regulatory liability of $5 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 September 30, 2017 and December 31, 2016 , BGE's regulatory asset of $7 million and $10 million , respectively, included $5 million and $6 million , respectively, of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order. (k) As of September 30, 2017 , Pepco’s regulatory asset of $20 million represents previously incurred PHI acquisition costs, including $11 million authorized for recovery in Maryland and $9 million expected to be recovered in the District of Columbia service territory. As of December 31, 2016 , Pepco's regulatory asset of $11 million represents previously incurred PHI acquisition costs authorized for recovery in Maryland. (l) As of September 30, 2017 , DPL’s regulatory asset of $11 million represents previously incurred PHI acquisition costs, including $4 million authorized for recovery in Maryland, $5 million authorized for recovery in Delaware electric rates, and $2 million expected to be recovered in electric and gas 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 the Maryland service territory. (m) As of September 30, 2017 , ACE’s regulatory asset of $9 million represents previously incurred PHI acquisition costs expected to be recovered in the New Jersey service territory. (n) Represents the electric and natural gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of September 30, 2017 , BGE had a regulatory asset of $24 million related to under-recovered electric revenue decoupling and $10 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	The following tables provide information about the purchased receivables of those companies as of September 30, 2017 and December 31, 2016 . Successor As of September 30, 2017 Exelon ComEd PECO BGE PHI Pepco DPL ACE Purchased receivables $ 312 $ 89 $ 68 $ 55 $ 100 $ 66 $ 10 $ 24 Allowance for uncollectible accounts (a) (33 ) (13 ) (5 ) (4 ) (11 ) (6 ) (1 ) (4 ) Purchased receivables, net $ 279 $ 76 $ 63 $ 51 $ 89 $ 60 $ 9 $ 20 Successor As of December 31, 2016 Exelon ComEd PECO BGE PHI Pepco DPL ACE Purchased receivables $ 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.

Early Nuclear Plant Retiremen31

Early Nuclear Plant Retirements Early Nuclear Plant Retirements (Tables)	9 Months Ended
	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Schedule of Other Operating Cost and Expense, by Component [Table Text Block]	Please refer to Note 13 — 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) Q3 2017 YTD 2017 Depreciation and amortization Accelerated depreciation (a) $ 106 $ 141 Accelerated nuclear fuel amortization 6 8 Total $ 112 $ 149 _________ (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 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 Asset32

Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 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 September 30, 2017 and December 31, 2016 : Exelon September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 710 $ — $ 710 $ — $ 710 Long-term debt (including amounts due within one year) (a) 34,865 — 34,686 1,949 36,635 Long-term debt to financing trusts (b) 389 — — 423 423 SNF obligation 1,142 — 857 — 857 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 92 $ — $ 92 $ — $ 92 Long-term debt (including amounts due within one year) (a) 9,528 — 7,915 1,652 9,567 SNF obligation 1,142 — 857 — 857 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 7,600 $ — $ 8,353 $ — $ 8,353 Long-term debt to financing trusts (b) 205 — — 226 226 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,902 $ — $ 3,181 $ — $ 3,181 Long-term debt to financing trusts 184 — — 197 197 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,577 $ — $ 2,817 $ — $ 2,817 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) September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 118 $ — $ 118 $ — $ 118 Long-term debt (including amounts due within one year) (a) 5,930 — 5,729 297 6,026 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,546 $ — $ 3,087 $ 9 $ 3,096 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 54 $ — $ 54 $ — $ 54 Long-term debt (including amounts due within one year) (a) 1,326 — 1,407 — 1,407 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 65 $ — $ 65 $ — $ 65 Long-term debt (including amounts due within one year) (a) 1,130 — 969 288 1,257 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 $196 million , $51 million , $53 million , $17 million , $17 million , $6 million , $32 million , $11 million , and $5 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of September 30, 2017 . Includes unamortized debt issuance costs which are not fair valued of $200 million , $64 million , $46 million , $15 million , $15 million , $2 million , $30 million , $11 million , and $6 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of December 31, 2016 . (b) Includes unamortized debt issuance costs which are not fair valued of $1 million and $1 million for Exelon and ComEd, respectively, as of September 30, 2017 .
Assets and liabilities measured and recorded at fair value on recurring basis	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 September 30, 2017 and December 31, 2016 : Successor As of September 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) $ 184 $ — $ — $ 184 $ 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 72 — — 72 73 — — 73 Fixed income — 13 — 13 — 16 — 16 Life insurance contracts — 23 21 44 — 22 20 42 Rabbi trust investments subtotal 72 36 21 129 73 38 20 131 Total assets 256 36 21 313 290 38 20 348 Liabilities Deferred compensation obligation — (24 ) — (24 ) — (28 ) — (28 ) Total liabilities — (24 ) — (24 ) — (28 ) — (28 ) Total net assets $ 256 $ 12 $ 21 $ 289 $ 290 $ 10 $ 20 $ 320 Pepco DPL ACE As of September 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 $ — $ — $ — $ — $ 31 $ — $ — $ 31 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 — — — — 31 — — 31 Liabilities Deferred compensation obligation — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total liabilities — (4 ) — (4 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 187 $ 32 $ 21 $ 240 $ — $ (1 ) $ — $ (1 ) $ 31 $ — $ — $ 31 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 $18 million and $19 million at September 30, 2017 and December 31, 2016 and includes long-term restricted cash of $22 million and $23 million at September 30, 2017 and December 31, 2016 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $7 million and $9 million at September 30, 2017 and December 31, 2016 . DPL excludes cash of $3 million and $4 million at September 30, 2017 and December 31, 2016 . ACE excludes cash of $5 million and $3 million at September 30, 2017 and December 31, 2016 and includes long-term restricted cash of $22 million and $23 million at September 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 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 September 30, 2017 and December 31, 2016 : Generation Exelon As of September 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) $ 80 $ — $ — $ — $ 80 $ 944 $ — $ — $ — $ 944 NDT fund investments Cash equivalents (b) 149 86 — — 235 149 86 — — 235 Equities 3,935 840 — 2,088 6,863 3,935 840 — 2,088 6,863 Fixed income Corporate debt — 1,651 255 — 1,906 — 1,651 255 — 1,906 U.S. Treasury and agencies 1,951 28 — — 1,979 1,951 28 — — 1,979 Foreign governments — 70 — — 70 — 70 — — 70 State and municipal debt — 246 — — 246 — 246 — — 246 Other (c) — 46 — 509 555 — 46 — 509 555 Fixed income subtotal 1,951 2,041 255 509 4,756 1,951 2,041 255 509 4,756 Middle market lending — — 416 87 503 — — 416 87 503 Private equity — — — 212 212 — — — 212 212 Real estate — — — 449 449 — — — 449 449 NDT fund investments subtotal (d) 6,035 2,967 671 3,345 13,018 6,035 2,967 671 3,345 13,018 Pledged assets for Zion Station decommissioning Cash equivalents 15 — — — 15 15 — — — 15 Generation Exelon As of September 30, 2017 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Middle market lending — — 17 25 42 — — 17 25 42 Pledged assets for Zion Station (e) 15 — 17 25 57 15 — 17 25 57 Rabbi trust investments Cash equivalents 5 — — — 5 77 — — — 77 Mutual funds 22 — — — 22 56 — — — 56 Fixed income — — — — — — 13 — — 13 Life insurance contracts — 21 — — 21 — 68 21 — 89 Rabbi trust investments subtotal 27 21 — — 48 133 81 21 — 235 Commodity derivative assets Economic hedges 487 2,076 1,628 — 4,191 487 2,076 1,628 — 4,191 Proprietary trading 2 41 42 — 85 2 41 42 — 85 Effect of netting and allocation of collateral (f) (g) (501 ) (1,828 ) (837 ) — (3,166 ) (501 ) (1,828 ) (837 ) — (3,166 ) Commodity derivative assets subtotal (12 ) 289 833 — 1,110 (12 ) 289 833 — 1,110 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 10 — — 10 Economic hedges 3 13 — — 16 3 13 — — 16 Effect of netting and allocation of collateral (3 ) (8 ) — — (11 ) (3 ) (8 ) — — (11 ) Interest rate and foreign currency derivative assets subtotal — 5 — — 5 — 15 — — 15 Other investments — — 43 — 43 — — 43 — 43 Total assets 6,145 3,282 1,564 3,370 14,361 7,115 3,352 1,585 3,370 15,422 Liabilities Commodity derivative liabilities Economic hedges (559 ) (2,062 ) (1,189 ) — (3,810 ) (559 ) (2,062 ) (1,466 ) — (4,087 ) Proprietary trading (3 ) (43 ) (27 ) — (73 ) (3 ) (43 ) (27 ) — (73 ) Effect of netting and allocation of collateral (f) (g) 560 2,043 978 — 3,581 560 2,043 978 — 3,581 Commodity derivative liabilities subtotal (2 ) (62 ) (238 ) — (302 ) (2 ) (62 ) (515 ) — (579 ) Interest rate and foreign currency derivative liabilities Economic hedges (2 ) (17 ) — — (19 ) (2 ) (17 ) — — (19 ) Effect of netting and allocation of collateral 2 8 — — 10 2 8 — — 10 Interest rate and foreign currency derivative liabilities subtotal — (9 ) — — (9 ) — (9 ) — — (9 ) Deferred compensation obligation — (35 ) — — (35 ) — (137 ) — — (137 ) Total liabilities (2 ) (106 ) (238 ) — (346 ) (2 ) (208 ) (515 ) — (725 ) Total net assets $ 6,143 $ 3,176 $ 1,326 $ 3,370 $ 14,015 $ 7,113 $ 3,144 $ 1,070 $ 3,370 $ 14,697 Generation Exelon As of December 31, 2016 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 39 $ — $ — $ — $ 39 $ 373 $ — $ — $ — $ 373 NDT fund investments Cash equivalents (b) 110 19 — — 129 110 19 — — 129 Equities 3,551 452 — 2,011 6,014 3,551 452 — 2,011 6,014 Fixed income Corporate debt — 1,554 250 — 1,804 — 1,554 250 — 1,804 U.S. Treasury and agencies 1,291 29 — — 1,320 1,291 29 — — 1,320 Foreign governments — 37 — — 37 — 37 — — 37 State and municipal debt — 264 — — 264 — 264 — — 264 Other (c) — 59 — 493 552 — 59 — 493 552 Fixed income subtotal 1,291 1,943 250 493 3,977 1,291 1,943 250 493 3,977 Middle market lending — — 427 71 498 — — 427 71 498 Private equity — — — 148 148 — — — 148 148 Real estate — — — 326 326 — — — 326 326 NDT fund investments subtotal (d) 4,952 2,414 677 3,049 11,092 4,952 2,414 677 3,049 11,092 Pledged assets for Zion Station decommissioning Cash equivalents 11 — — — 11 11 — — — 11 Equities — 2 — — 2 — 2 — — 2 Fixed Income - U.S. Treasury and agencies 16 1 — — 17 16 1 — — 17 Middle market lending — — 19 64 83 — — 19 64 83 Pledged assets for Zion Station decommissioning subtotal (e) 27 3 19 64 113 27 3 19 64 113 Rabbi trust investments Cash equivalents 2 — — — 2 74 — — — 74 Mutual funds 19 — — — 19 50 — — — 50 Fixed income — — — — — — 16 — — 16 Life insurance contracts — 18 — — 18 — 64 20 — 84 Rabbi trust investments subtotal 21 18 — — 39 124 80 20 — 224 Commodity derivative assets Economic hedges 1,356 2,505 1,229 — 5,090 1,358 2,505 1,229 — 5,092 Proprietary trading 3 50 23 — 76 3 50 23 — 76 Effect of netting and allocation of collateral (f) (g) (1,162 ) (2,142 ) (481 ) — (3,785 ) (1,164 ) (2,142 ) (481 ) — (3,787 ) Commodity derivative assets subtotal 197 413 771 — 1,381 197 413 771 — 1,381 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — — 16 — — 16 Economic hedges — 28 — — 28 — 28 — — 28 Proprietary trading 3 2 — — 5 3 2 — — 5 Effect of netting and allocation of collateral (2 ) (19 ) — — (21 ) (2 ) (19 ) — — (21 ) Interest rate and foreign currency derivative assets subtotal 1 11 — — 12 1 27 — — 28 Other investments — — 42 — 42 — — 42 — 42 Total assets 5,237 2,859 1,509 3,113 12,718 5,674 2,937 1,529 3,113 13,253 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 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 $282 million and $252 million at September 30, 2017 and December 31, 2016 and restricted cash of $184 million and $157 million at September 30, 2017 and December 31, 2016 . Exelon excludes cash of $382 million and $360 million at September 30, 2017 and December 31, 2016 and restricted cash of $219 million and $180 million at September 30, 2017 and December 31, 2016 and includes long-term restricted cash of $22 million and $25 million at September 30, 2017 and December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) Includes $75 million and $29 million of cash received from outstanding repurchase agreements at September 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 less than $1 million and $(2) million , which have a total notional amount of $885 million and $933 million at September 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 $52 million and $31 million at September 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 September 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 $59 million , $215 million and $141 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of September 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), $27 million represents variation margin on the exchanges as of September 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 September 30, 2017 and December 31, 2016 : ComEd PECO BGE As of September 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) $ 273 $ — $ — $ 273 $ 314 $ — $ — $ 314 $ 18 $ — $ — $ 18 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 273 — — 273 321 10 — 331 23 — — 23 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (10 ) — (10 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (277 ) (277 ) — — — — — — — — Total liabilities — (7 ) (277 ) (284 ) — (10 ) — (10 ) — (4 ) — (4 ) Total net assets (liabilities) $ 273 $ (7 ) $ (277 ) $ (11 ) $ 321 $ — $ — $ 321 $ 23 $ (4 ) $ — $ 19 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 $36 million at September 30, 2017 and December 31, 2016 and restricted cash of $2 million at December 31, 2016 . PECO excludes cash of $20 million and $22 million at September 30, 2017 and December 31, 2016 . BGE excludes cash of $11 million and $13 million at September 30, 2017 and December 31, 2016 and restricted cash of $1 million at September 30, 2017 and includes long-term restricted cash of $2 million at December 31, 2016 , which is reported in other deferred debits on the balance sheet. (b) The Level 3 balance consists of the current and noncurrent liability of $20 million and $257 million , respectively, at September 30, 2017 , and $19 million and $239 million , respectively, at December 31, 2016 , related to floating-to-fixed energy swap contracts with unaffiliated suppliers.
Fair value 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 nine months ended September 30, 2017 and 2016 : Successor Generation ComEd PHI Exelon Three Months Ended September 30, 2017 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Total Balance as of June 30, 2017 $ 683 $ 21 $ 589 $ 41 $ 1,334 $ (256 ) $ 20 $ — $ 1,098 Total realized / unrealized gains (losses) Included in net income — — (82 ) (a) 1 (81 ) — 1 — (80 ) Included in payable for Zion Station decommissioning — (4 ) — — (4 ) — — — (4 ) Included in regulatory assets — — — — — (21 ) (b) — — (21 ) Change in collateral — — 11 — 11 — — — 11 Purchases, sales, issuances and settlements Purchases 19 — 57 1 77 — — — 77 Settlements (31 ) — 10 (c) — (21 ) — — — (21 ) Transfers out of Level 3 — — 10 — 10 — — — 10 Balance at September 30, 2017 $ 671 $ 17 $ 595 $ 43 $ 1,326 $ (277 ) $ 21 $ — $ 1,070 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2017 $ — $ — $ 24 $ 1 $ 25 $ — $ 1 $ — $ 26 Successor Generation ComEd PHI Exelon Nine Months Ended September 30, 2017 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives 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 — (110 ) (a) 2 (104 ) — 2 — (102 ) Included in noncurrent payables to affiliates 13 — — — 13 — — (13 ) — Included in payable for Zion Station decommissioning — (3 ) — — (3 ) — — — (3 ) Included in regulatory assets — — — — — (19 ) (b) — 13 (6 ) Change in collateral — — 81 — 81 — — — 81 Purchases, sales, issuances and settlements Purchases 54 1 146 4 205 — — — 205 Sales — — (15 ) — (15 ) — — — (15 ) Issuances — — — — — — (1 ) — (1 ) Settlements (77 ) — (8 ) (c) — (85 ) — — — (85 ) Transfers into Level 3 — — (9 ) — (9 ) — — — (9 ) Transfers out of Level 3 — — 17 (5 ) 12 — — — 12 Balance as of September 30, 2017 $ 671 $ 17 $ 595 $ 43 $ 1,326 $ (277 ) $ 21 $ — $ 1,070 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2017 $ 2 $ — $ 161 $ 2 $ 165 $ — $ 2 $ — $ 167 _________ (a) Includes a reduction for the reclassification of $96 million and $279 million of realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2017 . (b) Includes $ 24 million of decreases in fair value and an increase for realized losses due to settlements of $ 3 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2017 . Includes $ 32 million of decreases in fair value and an increase for realized losses due to settlements of $ 13 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2017 . (c) Exelon includes the settlement value for any open contracts that were net settled prior to their scheduled maturity within this line item. Successor Generation ComEd PHI Exelon Three Months Ended September 30, 2016 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Total Balance as of June 30, 2016 $ 715 $ 25 $ 609 $ 37 $ 1,386 $ (221 ) $ 20 $ — $ 1,185 Total realized / unrealized gains (losses) Included in net income (4 ) — 95 (a) 1 92 — 1 — 93 Included in noncurrent payables to affiliates 6 — — — 6 — — (6 ) — Included in payable for Zion Station decommissioning — (1 ) — — (1 ) — — — (1 ) Included in regulatory assets — — — — — (23 ) (b) — 6 (17 ) Change in collateral — — 31 — 31 — — — 31 Purchases, sales, issuances and settlements Purchases 4 — 207 (c) 3 214 — — — 214 Sales — (5 ) (2 ) — (7 ) — — — (7 ) Issuances — — — — — — — — — Settlements (28 ) — — — (28 ) — — — (28 ) Transfers into Level 3 — — (1 ) 1 — — — — — Transfers out of Level 3 — — (4 ) — (4 ) — — — (4 ) Balance as of September 30, 2016 $ 693 $ 19 $ 935 $ 42 $ 1,689 $ (244 ) $ 21 $ — $ 1,466 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2016 $ 3 $ — $ 285 $ — $ 288 $ — $ — $ — $ 288 Successor Generation ComEd PHI (d) Exelon Nine Months Ended September 30, 2016 NDT Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Total Balance as of December 31, 2015 $ 670 $ 22 $ 1,051 $ 33 $ 1,776 $ (247 ) $ — $ — $ 1,529 Included due to merger — — — — — — 20 — 20 Total realized / unrealized gains (losses) Included in net income 2 — (339 ) (a) 1 (336 ) — 2 — (334 ) Included in noncurrent payables to affiliates 18 — — — 18 — — (18 ) — Included in payable for Zion Station decommissioning — 1 — — 1 — — — 1 Included in regulatory assets — — — — — 3 (b) — 18 21 Change in collateral — — (51 ) — (51 ) — — — (51 ) Purchases, sales, issuances and settlements Purchases 123 1 289 (c) 7 420 — — — 420 Sales (1 ) (5 ) (5 ) — (11 ) — — — (11 ) Issuances — — — — — — (1 ) — (1 ) Settlements (119 ) — — — (119 ) — — — (119 ) Transfers into Level 3 — — 1 1 2 — — — 2 Transfers out of Level 3 — — (11 ) — (11 ) — — — (11 ) Balance as of September 30, 2016 $ 693 $ 19 $ 935 $ 42 $ 1,689 $ (244 ) $ 21 $ — $ 1,466 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2016 $ 7 $ — $ 240 $ — $ 247 $ — $ 1 $ — $ 248 _________ (a) Includes a reduction for the reclassification of $190 million and $579 million of realized gains due to the settlement of derivative contracts recorded in results of operations for the three and nine months ended September 30, 2016 . (b) Includes $25 million of decreases in fair value and an increase for realized losses due to settlements of $2 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2016 . Includes $10 million of decreases in fair value and an increase for realized losses due to settlements of $13 million for the nine months ended September 30, 2016 . (c) Includes $168 million of fair value from contracts acquired as a result of portfolio acquisitions. (d) Successor period represents activity from March 24, 2016 through September 30, 2016 . See tables below for PHI's predecessor periods, as well as activity for Pepco for the three and nine months ended September 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 Nine 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 3 Purchases, sales, issuances and settlements Issuances — — (1 ) (1 ) Ending balance $ 21 $ 21 $ 21 $ 21 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 $ 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 nine months ended September 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 September 30, 2017 $ (3 ) $ (69 ) $ 1 $ 1 $ (3 ) $ (69 ) $ 2 Total gains (losses) included in net income for the nine months ended September 30, 2017 34 (152 ) 6 2 34 (152 ) 8 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended September 30, 2017 47 (23 ) 1 1 47 (23 ) 2 Change in the unrealized gains (losses) relating to assets and liabilities held for the nine months ended September 30, 2017 222 (61 ) 4 2 222 (61 ) 6 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 September 30, 2016 $ 180 $ (85 ) $ (4 ) $ 1 $ 180 $ (85 ) $ (3 ) Total gains (losses) included in net income for the nine months ended September 30, 2016 (232 ) (107 ) 2 2 (232 ) (107 ) 4 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended September 30, 2016 323 (38 ) 3 — 323 (38 ) 3 Change in the unrealized gains (losses) relating to assets and liabilities held for the nine months ended September 30, 2016 303 (63 ) 7 1 303 (63 ) 8 Predecessor PHI Pepco January 1, 2016 to March 23, 2016 Three Months Ended Nine Months Ended 2017 2016 2017 2016 Other, net (a) Other, net (a) Total gains (losses) included in net income $ (17 ) $ 1 $ 1 $ 2 $ 3 Change in the unrealized gains (losses) relating to assets and liabilities held 1 1 — 2 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 September 30, 2017 Valuation Technique Unobservable Input Range Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(b) $ 439 Discounted Forward power $7 - $124 Forward gas $1.84 - $9.43 Option Model Volatility 9% - 114% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ 15 Discounted Forward power $12 - $69 Mark-to-market derivatives (Exelon and ComEd) $ (277 ) Discounted Forward heat (c) 9x - 10x Marketability 3% - 8% Renewable 88% - 125% _________ (a) The valuation techniques, unobservable inputs and ranges are the same for the asset and liability positions. (b) The fair values do not include cash collateral posted on level three positions of $141 million as of September 30, 2017 . (c) 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. Type of trade Fair Value at December 31, 2016 Valuation Technique Unobservable Input Range Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(b) $ 435 Discounted Forward power price $11 - $130 Forward gas price $1.72 - $9.20 Option Model Volatility percentage 8% - 173% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ (3 ) Discounted Forward power price $19 - $79 Mark-to-market derivatives (Exelon and ComEd) $ (258 ) Discounted Cash Flow Forward heat (c) 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) The fair values do not include cash collateral posted on level three positions of $61 million as of December 31, 2016 . (c) 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.
Exelon Generation Co L L C [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	Generation September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 92 $ — $ 92 $ — $ 92 Long-term debt (including amounts due within one year) (a) 9,528 — 7,915 1,652 9,567 SNF obligation 1,142 — 857 — 857 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 7,600 $ — $ 8,353 $ — $ 8,353 Long-term debt to financing trusts (b) 205 — — 226 226 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,902 $ — $ 3,181 $ — $ 3,181 Long-term debt to financing trusts 184 — — 197 197 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,577 $ — $ 2,817 $ — $ 2,817 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) September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 118 $ — $ 118 $ — $ 118 Long-term debt (including amounts due within one year) (a) 5,930 — 5,729 297 6,026 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) (a) $ 2,546 $ — $ 3,087 $ 9 $ 3,096 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 54 $ — $ 54 $ — $ 54 Long-term debt (including amounts due within one year) (a) 1,326 — 1,407 — 1,407 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 September 30, 2017 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 65 $ — $ 65 $ — $ 65 Long-term debt (including amounts due within one year) (a) 1,130 — 969 288 1,257 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 Instrume33

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of the derivative fair value	The following table provides a summary of the derivative fair value balances recorded by the Registrants as of September 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) $ 2,608 $ 55 $ (1,969 ) $ 694 $ — $ — $ — $ — $ — $ 694 Mark-to-market derivative assets (noncurrent assets) 1,583 30 (1,197 ) 416 — — — — — 416 Total mark-to-market derivative assets 4,191 85 (3,166 ) 1,110 — — — — — 1,110 Mark-to-market derivative liabilities (current liabilities) (2,334 ) (46 ) 2,230 (150 ) (20 ) — — — — (170 ) Mark-to-market derivative liabilities (noncurrent liabilities) (1,476 ) (27 ) 1,351 (152 ) (257 ) — — — — (409 ) Total mark-to-market derivative liabilities (3,810 ) (73 ) 3,581 (302 ) (277 ) — — — — (579 ) Total mark-to-market derivative net assets (liabilities) $ 381 $ 12 $ 415 $ 808 $ (277 ) $ — $ — $ — $ — $ 531 _________ (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 $123 million and $61 million , respectively, and current and noncurrent liabilities are shown net of collateral of $138 million and $93 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $415 million at September 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), $27 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. Below is a summary of the interest rate and foreign exchange hedge balances as of September 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) $ — $ 15 $ — $ (10 ) $ 5 $ — $ 5 Mark-to-market derivative assets (noncurrent assets) — 1 — (1 ) — 10 10 Total mark-to-market derivative assets — 16 — (11 ) 5 10 15 Mark-to-market derivative liabilities (current liabilities) — (17 ) — 9 (8 ) — (8 ) Mark-to-market derivative liabilities (noncurrent liabilities) — (2 ) — 1 (1 ) — (1 ) Total mark-to-market derivative liabilities — (19 ) — 10 (9 ) — (9 ) Total mark-to-market derivative net assets (liabilities) $ — $ (3 ) $ — $ (1 ) $ (4 ) $ 10 $ 6 __________ (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. 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 September 30, Income Statement Location 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on Borrowings Exelon Interest expense $ (2 ) $ (8 ) $ 6 $ 14 Nine Months Ended September 30, Income Statement Location 2017 2016 2017 2016 Gain (loss) on Swaps Gain (loss) on Borrowings Exelon Interest expense $ (6 ) $ 15 $ 17 $ (3 )
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 September 30, 2017 Income Statement Location Total Cash Total Cash Flow Hedges Accumulated OCI derivative loss at June 30, 2017 $ (14 ) $ (12 ) Effective portion of changes in fair value 1 1 Reclassifications from AOCI to net income Interest Expense (1 ) (a) (1 ) (a) Accumulated OCI derivative loss at September 30, 2017 $ (14 ) $ (12 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Nine Months Ended September 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 2 2 Reclassifications from AOCI to net income Interest Expense 3 (b) 3 (b) Accumulated OCI derivative loss at September 30, 2017 $ (14 ) $ (12 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Three Months Ended September 30, 2016 Income Statement Location Total Cash Total Cash Flow Hedges Accumulated OCI derivative loss at June 30, 2016 $ (25 ) $ (26 ) Effective portion of changes in fair value 1 3 Accumulated OCI derivative loss at September 30, 2016 $ (24 ) $ (23 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Nine Months Ended September 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 — (1 ) Reclassifications from AOCI to net income Interest Expense (3 ) (c) (3 ) (c) Accumulated OCI derivative loss at September 30, 2016 $ (24 ) $ (23 ) _________ (a) Amount is net of related income tax benefit of $1 million for the three months ended September 30, 2017 . (b) Amount is net of related income tax expense of $2 million for the nine months ended September 30, 2017 . (c) Amount is net of related income tax expense of $2 million for the nine months ended September 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” 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 September 30, 2017 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ 132 $ 45 $ 177 $ 177 Reclassification to realized at settlement of commodity positions (77 ) (24 ) (101 ) (101 ) Net commodity mark-to-market gains (losses) 55 21 76 76 Change in fair value of treasury positions (3 ) — (3 ) (3 ) Reclassification to realized at settlement of treasury positions — — — — Net treasury mark-to-market gains (losses) (3 ) — (3 ) (3 ) Net mark-to-market gains (losses) $ 52 $ 21 $ 73 $ 73 Generation Exelon Nine Months Ended September 30, 2017 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ 123 $ (153 ) $ (30 ) $ (30 ) Reclassification to realized of commodity positions (164 ) 39 (125 ) (125 ) Net commodity mark-to-market gains (losses) (41 ) (114 ) (155 ) (155 ) Change in fair value of treasury positions (4 ) — (4 ) (4 ) Reclassification to realized of treasury positions (2 ) — (2 ) (2 ) Net treasury mark-to-market gains (losses) (6 ) — (6 ) (6 ) Net mark-to-market gains (losses) $ (47 ) $ (114 ) $ (161 ) $ (161 ) Generation Exelon Three Months Ended September 30, 2016 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ 280 $ (73 ) $ 207 $ 207 Reclassification to realized at settlement of commodity positions (92 ) (26 ) (118 ) (118 ) Net commodity mark-to-market gains (losses) 188 (99 ) 89 89 Change in fair value of treasury positions 1 — 1 1 Reclassification to realized at settlement of treasury positions (2 ) — (2 ) (2 ) Net treasury mark-to-market gains (losses) (1 ) — (1 ) (1 ) Net mark-to-market gains (losses) $ 187 $ (99 ) $ 88 $ 88 Generation Exelon Nine Months Ended September 30, 2016 Operating Revenues Purchased Power and Fuel Total Total Change in fair value of commodity positions $ 127 $ 36 $ 163 $ 163 Reclassification to realized of commodity positions (484 ) 217 (267 ) (267 ) Net commodity mark-to-market gains (losses) (357 ) 253 (104 ) (104 ) Change in fair value of treasury positions (3 ) — (3 ) (3 ) Reclassification to realized of treasury positions (6 ) — (6 ) (6 ) Net treasury mark-to-market gains (losses) (9 ) — (9 ) (9 ) Net mark-to-market gains (losses) $ (366 ) $ 253 $ (113 ) $ (113 ) 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 Nine Months Ended 2017 2016 2017 2016 Change in fair value of commodity positions $ 11 $ 4 $ 17 $ 18 Reclassification to realized of commodity positions (6 ) (6 ) (13 ) (17 ) Net commodity mark-to-market gains (losses) 5 (2 ) 4 1 Change in fair value of treasury positions (1 ) — (2 ) (2 ) Reclassification to realized of treasury positions 1 1 1 2 Net treasury mark-to-market gains (losses) — 1 (1 ) — Total net mark-to-market gains (losses) $ 5 $ (1 ) $ 3 $ 1
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 September 30, 2017 December 31, 2016 Gross fair value of derivative contracts containing this feature (a) $ (916 ) $ (960 ) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 638 627 Net fair value of derivative contracts containing this feature (c) $ (278 ) $ (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 September 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 $18 million , $22 million , $22 million , $34 million , $12 million , and $7 million as of September 30, 2017 , respectively. Rating as of September 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 $ 828 $ 9 $ 819 1 $ 278 Non-investment grade 44 4 40 No external ratings Internally rated — investment grade 316 — 316 Internally rated — non-investment grade 100 18 82 Total $ 1,288 $ 31 $ 1,257 1 $ 278 Net Credit Exposure by Type of Counterparty As of Financial institutions $ 48 Investor-owned utilities, marketers, power producers 538 Energy cooperatives and municipalities 525 Other 146 Total $ 1,257 _________ (a) As of September 30, 2017 , credit collateral held from counterparties where Generation had credit exposure included $19 million of cash and $12 million of letters of credit. The credit collateral does not include non-liquid collateral.

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Commercial Paper Borrowings	The Registrants had the following amounts of commercial paper borrowings outstanding as of September 30, 2017 and December 31, 2016 : Commercial Paper Borrowings September 30, 2017 December 31, 2016 Exelon $ 118 $ 688 Generation — 620 BGE — 45 PHI 118 23 Pepco — 23 DPL 54 — ACE 65 —
Schedule of Long-term Debt Instruments [Table Text Block]	During the nine months ended September 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 $ 14 Albany Green Energy biomass generation development. Generation Energy Efficiency Project Financing 3.90 % February 1, 2018 $ 17 Funding to install energy conservation measures for the Naval Station Great Lakes project. Generation Energy Efficiency Project Financing 2.61 % September 30, 2018 $ 10 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 $ 4 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. ComEd First Mortgage Bonds, Series 122 2.95 % August 15, 2027 $ 350 Refinance maturing first mortgage bonds, to repay a portion of ComEd’s outstanding commercial paper obligations and for general corporate purposes. ComEd First Mortgage Bonds, Series 123 3.75 % August 15, 2047 $ 650 Refinance maturing first mortgage bonds, to repay a portion of ComEd’s outstanding commercial paper obligations and for general corporate purposes. PECO First and Refunding Mortgage Bonds 3.70 % September 15, 2047 $ 325 General corporate purposes. BGE Notes 3.75 % August 15, 2047 $ 300 Redeem $250 million in principal amount of the 6.20% Deferrable Interest Subordinated Debentures due October 15, 2043 issued by BGE's affiliate BGE Capital Trust II, repay commercial paper obligations and for general corporate purposes. Pepco Energy Efficiency Project Financing 3.30 % December 15, 2017 $ 2 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.

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 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 September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE 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 2.2 5.6 6.6 (0.1) 5.3 5.1 2.2 5.3 5.6 Qualified nuclear decommissioning trust fund income 2.6 5.8 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.1) (2.2) (0.2) (0.1) (0.1) (0.2) (0.1) (0.2) (0.4) Plant basis differences (2.6) — (0.3) (14.6) (0.8) (4.9) (6.7) (1.9) (3.4) Production tax credits and other credits (2.2) (4.8) — — — — — — — Noncontrolling interests 0.5 1.0 — — — — — — — FitzPatrick bargain purchase gain (0.2) (0.4) — — — — — — — Other (0.1) 0.3 (0.2) (0.2) (0.2) 0.2 — (0.2) 0.1 Effective income tax rate 34.1% 40.3% 40.9% 20.0% 39.2% 35.2% 30.4% 38.0% 36.9% Three Months Ended September 30, 2016 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 3.8 2.6 7.3 2.4 5.2 5.6 5.6 5.2 6.1 Qualified nuclear decommissioning trust fund income 4.0 7.8 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.9) (1.6) (0.6) (0.1) (0.2) (0.1) — (0.2) (0.1) Plant basis differences (3.0) — (1.9) (6.7) (0.5) (5.0) (6.7) (1.3) (4.6) Production tax credits and other credits (2.9) (5.7) (0.1) — — — — — — Noncontrolling interest 0.2 0.5 — — — — — — — Statute of limitations expiration (0.1) 0.3 — — — — — — — Penalties 4.3 — 27.2 — — — — — — Merger expenses (0.6) — — — — (5.7) (2.3) (8.6) (2.9) Other (0.8) (0.5) 0.1 0.1 (0.4) (0.7) (0.9) 0.1 (0.6) Effective income tax rate 39.0% 38.4% 67.0% 30.7% 39.1% 29.1% 30.7% 30.2% 32.9% Nine Months Ended September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 0.7 2.1 5.9 (0.1) 5.2 4.9 3.0 5.1 5.6 Qualified nuclear decommissioning trust fund income 4.0 14.0 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.9) (2.7) (0.2) (0.1) (0.1) (0.2) (0.1) (0.2) (0.4) Plant basis differences (3.4) — (0.3) (14.4) (0.8) (4.6) (6.3) (1.8) (3.4) Production tax credits and other credits (1.8) (6.2) — — — — — — — Noncontrolling interests 0.2 0.7 — — — — — — — Merger expenses (5.4) (2.5) — — — (11.8) (8.0) (10.0) (23.0) FitzPatrick bargain purchase gain (3.2) (11.2) — — — — — — — Like-kind exchange (a) (1.7) — 1.7 — — — — — — Other — (0.4) 0.2 — 0.2 — (0.3) 0.6 (0.3) Effective income tax rate 23.5% 28.8% 42.3% 20.4% 39.5% 23.3% 23.3% 28.7% 13.5% Successor Predecessor Nine Months Ended September 30, 2016 March 24, 2016 to September 30, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL (b) ACE (b) PHI (b) PHI U.S. Federal statutory rate 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% 35.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit (c) 2.5 2.6 5.4 1.3 4.8 23.0 310.5 5.5 4.4 11.9 Qualified nuclear decommissioning trust fund income 4.8 8.8 — — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.3) (2.0) (0.3) (0.1) (0.2) (0.2) (17.9) 0.5 0.5 (0.9) Plant basis differences (4.5) — (0.6) (8.8) (3.3) (29.0) (98.6) 7.8 17.5 (13.5) Production tax credits and other credits (4.1) (7.6) — — — — — — — — Noncontrolling interest 0.5 0.9 — — — — — — — — Statute of limitations expiration (0.5) (1.7) — — — — — — — — Penalties 2.3 — 5.6 — — — — — — — Merger expenses 6.2 — — — — 36.7 635.9 (35.4) (49.8) 11.1 Other (1.8) (2.1) — (1.5) — (2.5) 35.1 0.4 1.4 3.6 Effective income tax rate 39.1% 33.9% 45.1% 25.9% 36.3% 63.0% 900.0% 13.8% 9.0% 47.2% _________ (a) See Like-Kind Exchange within the Other Income Tax Matters section below for further details. (b) DPL and ACE recognized a loss before income taxes for the nine months ended September 30, 2016 , and PHI recognized a loss before income taxes for the period of March 24, 2016, through September 30, 2016 . As a result, positive percentages represent an income tax benefit for the periods presented. (c) Includes a remeasurement of uncertain state income tax positions for Pepco and DPL.
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	The Registrants have the following unrecognized tax benefits as of September 30, 2017 and December 31, 2016 : Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2017 $ 738 $ 468 $ 2 $ — $ 120 $ 120 $ 59 $ 21 $ 8 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE December 31, 2016 $ 916 $ 490 $ (12 ) $ — $ 120 $ 172 $ 80 $ 37 $ 22

Nuclear Decommissioning (Tables

Nuclear Decommissioning (Tables)	9 Months Ended
	Sep. 30, 2017
Schedule Of Nuclear Decommissioning [Line Items]
Schedule of Financial Instruments Owned and Pledged as Collateral [Table Text Block]	The following table provides the pledged assets and payables to ZionSolutions, and withdrawals by ZionSolutions at September 30, 2017 and December 31, 2016 : Exelon and Generation September 30, 2017 December 31, 2016 Carrying value of Zion Station pledged assets $ 57 $ 113 Payable to Zion Solutions (a) 53 104 Current portion of payable to Zion Solutions (b) 53 90 Cumulative withdrawals by Zion Solutions to pay decommissioning costs (c) 928 878 _________ (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 September 30, 2017 : Nuclear decommissioning ARO at December 31, 2016 (a) $ 8,734 Acquisition of FitzPatrick 444 Accretion expense 342 Net decrease due to changes in, and timing of, estimated cash flows (148 ) Costs incurred to decommission retired plants (6 ) Nuclear decommissioning ARO at September 30, 2017 (a) $ 9,366 _________ (a) Includes $12 million and $10 million for the current portion of the ARO at September 30, 2017 and December 31, 2016 , respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets.
Unrealized Gain (Loss) on Investments [Table Text Block]	The following table provides unrealized gains on NDT funds for the three and nine months ended September 30, 2017 and 2016 : Exelon and Generation Exelon and Generation Three Months Ended Nine Months Ended 2017 2016 2017 2016 Net unrealized gains on decommissioning trust funds — Regulatory Agreement Units (a) $ 44 $ 155 $ 253 $ 286 Net unrealized gains on decommissioning trust funds — Non-Regulatory Agreement Units (b)(c) 111 116 347 216 _________ (a) Net unrealized gains related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets. (b) Excludes $4 million and $5 million of net unrealized losses related to the Zion Station pledged assets for the three months ended September 30, 2017 and 2016 respectively. Excludes $5 million and $2 million of net unrealized losses related to the Zion Station pledged assets for the nine months ended September 30, 2017 and 2016 , respectively. Net unrealized 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)	9 Months Ended
	Sep. 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 nine months ended September 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 $ 98 $ 92 $ 26 $ 27 Interest cost 211 215 45 47 Expected return on assets (300 ) (293 ) (39 ) (42 ) Amortization of: Prior service (benefit) cost (1 ) 3 (47 ) (48 ) Actuarial loss 152 142 15 18 Settlement charges 1 — — — Net periodic benefit cost $ 161 $ 159 $ — $ 2 Pension Benefits Other Postretirement Benefits 2017 (a) 2016 (b) 2017 (a) 2016 (b) Components of net periodic benefit cost: Service cost $ 290 $ 262 $ 79 $ 80 Interest cost 632 616 136 138 Expected return on assets (898 ) (847 ) (121 ) (121 ) Amortization of: Prior service cost (benefit) — 10 (140 ) (138 ) Actuarial loss 455 411 46 47 Settlement charges 3 — — — Net periodic benefit cost $ 482 $ 452 $ — $ 6 _________ (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 nine months ended September 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 September 30, 2016 , respectively. Three Months Ended September 30, Nine Months Ended September 30, Pension and Other Postretirement Benefit Costs 2017 2016 2017 2016 Exelon $ 161 $ 161 $ 482 $ 458 Generation (a) 57 54 170 163 ComEd 44 41 131 124 PECO 7 8 21 25 BGE 16 17 48 51 BSC (b) 13 13 40 37 Pepco (c) 6 8 19 24 DPL (c) 3 4 10 13 ACE (c) 3 4 10 11 PHISCO (c)(d) 12 12 33 33 Successor Predecessor Pension and Other Postretirement Benefit Costs Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 Nine Months Ended September 30, 2017 March 24, 2016 to September 30, 2016 January 1, 2016 to March 23, 2016 PHI $ 24 $ 28 $ 72 $ 58 $ 23 _________ (a) FitzPatrick net benefit costs are included for the period after acquisition. (b) 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. (c) Pepco's, DPL's, ACE's and PHISCO's pension and postretirement benefit costs for the nine months ended September 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 . (d) These amounts represent amounts billed to Pepco, DPL, and ACE through intercompany allocations. These amounts are not included in Pepco, DPL, or ACE amounts above.
Schedule Of Defined Contributions	The following table presents the matching contributions to the savings plans during the three and nine months ended September 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 September 30, 2016 , respectively. Three Months Ended September 30, Nine Months Ended September 30, Savings Plan Matching Contributions 2017 2016 2017 2016 Exelon $ 34 $ 51 $ 97 $ 107 Generation 14 31 42 56 ComEd 9 10 24 23 PECO 3 3 7 7 BGE 3 2 7 5 BSC (a) 2 2 7 9 Pepco (b) 1 — 3 2 DPL (b) 1 1 2 2 ACE — — 1 1 PHISCO (b)(c) 1 2 4 5 Successor Predecessor Savings Plan Matching Contributions Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 Nine Months Ended September 30, 2017 March 24, 2016 to September 30, 2016 January 1, 2016 to March 23, 2016 PHI $ 3 $ 3 $ 10 $ 7 $ 3 _________ (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 and PHISCO's matching contributions for the nine months ended September 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 nine months ended September 30, 2016 . (c) These amounts represent amounts billed to Pepco, DPL, and ACE through intercompany allocations. These amounts are not included in Pepco, DPL, or ACE amounts above.

Severance (Tables)

Severance (Tables)	9 Months Ended
	Sep. 30, 2017
Restructuring and Related Activities [Abstract]
Severance	For the three and nine months ended September 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 Three Months Ended September 30, 2017 (a) $ 7 $ 7 $ — $ — $ — September 30, 2016 (b) 1 1 — — — Nine Months Ended September 30, 2017 (a) $ 6 $ 6 $ — $ — $ — September 30, 2016 (b) 18 13 3 1 1 _________ (a) Amounts billed by BSC through intercompany allocations for the nine months ended September 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 nine months ended September 30, 2016 . For the three and nine months ended September 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 September 30, 2017 $ 1 $ — $ — $ 1 $ 1 $ — $ — September 30, 2016 8 7 — 1 — — — Nine Months Ended September 30, 2017 $ 10 $ 4 $ 2 $ 4 $ 2 $ 1 $ 1 September 30, 2016 12 10 1 1 — — — _________ (a) The amounts above for Generation include $2 million for amounts billed by BSC through intercompany allocations for the nine months ended September 30, 2017 and $1 million and $2 million for the three and nine months ended September 30, 2016 , respectively. The amounts above for ComEd include $1 million for amounts billed by BSC through intercompany allocations for the three and nine months ended September 30, 2016 . The amounts above for PHI include less than $1 million and $1 million billed by BSC through intercompany allocations for the three and nine months ended September 30, 2017 , respectively, and $1 million for the three and nine months ended September 30, 2016 . Amounts billed by PHISCO to Pepco were $1 million and $2 million for the three and nine months ended September 30, 2017 , respectively. Amounts billed by PHISCO to DPL and ACE were $1 million , each, for the nine months ended September 30, 2017 . Pepco, DPL and ACE did not have any ongoing severance plans for the three and nine months ended September 30, 2016 . For the three and nine months ended September 30, 2017 and the three months ended September 30, 2016 , the PHI Merger severance costs were immaterial. For the nine months ended September 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 Nine Months Ended September 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 $8 million , $2 million , $1 million , $1 million , $19 million , $11 million and $10 million , respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the nine months ended September 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) 33 25 1 — — 3 — — — Payments (24 ) (7 ) (1 ) — — (11 ) — — — Balance at September 30, 2017 $ 97 $ 54 $ 3 $ — $ — $ 21 $ — $ — $ — _________ (a) Includes salary continuance and health and welfare severance benefits.

Changes in Accumulated Other 39

Changes in Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 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 nine months ended September 30, 2017 and 2016 : Nine Months Ended September 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 2 2 (55 ) 7 7 (37 ) Amounts reclassified from AOCI (b) 3 — 105 — — 108 Net current-period OCI 5 2 50 7 7 71 Ending balance $ (12 ) $ 6 $ (2,560 ) $ (23 ) $ — $ (2,589 ) Generation (a) Beginning balance $ (19 ) $ 2 $ — $ (30 ) $ (7 ) $ (54 ) OCI before reclassifications 2 — — 7 6 15 Amounts reclassified from AOCI (b) 3 — — — — 3 Net current-period OCI 5 — — 7 6 18 Ending balance $ (14 ) $ 2 $ — $ (23 ) $ (1 ) $ (36 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 Nine Months Ended September 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 (9 ) — (2 ) 3 (5 ) (13 ) Amounts reclassified from AOCI (b) 5 — 104 5 — 114 Net current-period OCI (4 ) — 102 8 (5 ) 101 Ending balance $ (23 ) $ 3 $ (2,463 ) $ (32 ) $ (8 ) $ (2,523 ) Generation (a) Beginning balance $ (21 ) $ 1 $ — $ (40 ) $ (3 ) $ (63 ) OCI before reclassifications (8 ) 1 — 3 1 (3 ) Amounts reclassified from AOCI (b) 5 — — 5 — 10 Net current-period OCI (3 ) 1 — 8 1 7 Ending balance $ (24 ) $ 2 $ — $ (32 ) $ (2 ) $ (56 ) 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 nine months ended September 30, 2017 and 2016 . Three Months Ended September 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 $ 2 $ 2 Interest expense Total before tax 2 2 Tax benefit (1 ) (1 ) Net of tax $ 1 $ 1 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 23 — Net of tax $ (35 ) $ — Total Reclassifications for the period $ (34 ) $ 1 Comprehensive income Nine Months Ended September 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 $ (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) $ 69 $ — Actuarial losses (b) (243 ) — Total before tax (174 ) — Tax benefit 69 — Net of tax $ (105 ) $ — Total Reclassifications $ (108 ) $ (3 ) Comprehensive income Three Months Ended September 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 Gains and (losses) on cash flow hedges Other cash flow hedges $ (3 ) $ (3 ) Interest expense Total before tax (3 ) (3 ) Tax expense 1 1 Net of tax $ (2 ) $ (2 ) Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 19 $ — Actuarial losses (b) (76 ) — Total before tax (57 ) — Tax benefit 22 — Net of tax $ (35 ) $ — Gains and (losses) on foreign currency translation Other $ (5 ) $ (5 ) Other Income and (deductions) Total before tax (5 ) (5 ) Tax expense — — Net of tax $ (5 ) $ (5 ) Comprehensive income Total Reclassifications for the period $ (42 ) $ (7 ) Comprehensive income Nine Months Ended September 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 $ (8 ) $ (8 ) $ — Interest expense Total before tax (8 ) (8 ) — Tax benefit 3 3 — Net of tax $ (5 ) $ (5 ) $ — Comprehensive income Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 57 $ — $ — Actuarial losses (b) (227 ) — (1 ) Total before tax (170 ) — (1 ) Tax benefit 66 — — Net of tax $ (104 ) $ — $ (1 ) Gains and (losses) on foreign currency translation Other $ (5 ) $ (5 ) $ — Other income and (deductions) Total before tax (5 ) (5 ) — Tax expense — — — Net of tax $ (5 ) $ (5 ) $ — Total Reclassifications $ (114 ) $ (10 ) $ (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 14 — 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 nine months ended September 30, 2017 and 2016 : Three Months Ended September 30, Nine Months Ended 2017 2016 2017 2016 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 9 $ 7 $ 27 $ 22 Actuarial loss reclassified to periodic benefit cost (32 ) (29 ) (96 ) (88 ) Pension and non-pension postretirement benefit plans valuation adjustment — 1 2 1 Change in unrealized (loss)/gain on cash flow hedges — (1 ) (3 ) 3 Change in unrealized (loss)/gain on equity investments 1 — (2 ) 3 Change in unrealized (loss)/gain on marketable securities — (1 ) (2 ) (1 ) Total $ (22 ) $ (23 ) $ (74 ) $ (60 ) Generation Change in unrealized (loss)/gain on cash flow hedges $ — $ (2 ) $ (3 ) $ 1 Change in unrealized (loss)/gain on equity investments — — (2 ) 3 Change in unrealized gain on marketable securities — — (1 ) — Total $ — $ (2 ) $ (6 ) $ 4 Predecessor PHI January 1, 2016 to March 23, 2016 Pension and non-pension postretirement benefit plans: Actuarial loss reclassified to periodic cost $ —

Earnings Per Share and Equity40

Earnings Per Share and Equity (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Reconciliation of basic and diluted earnings per share	The following table sets forth the components of basic and diluted earnings per share and shows the effect of 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 September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Exelon Net income attributable to common shareholders $ 824 $ 490 $ 1,899 $ 930 Weighted average common shares outstanding — basic 962 925 941 924 Assumed exercise and/or distributions of stock-based awards 3 2 2 2 Weighted average common shares outstanding — diluted 965 927 943 926

Commitments and Contingencies41

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2017
Commitments And Contingencies Tables Disclosure [Line Items]
Other Commitments	Commercial Commitments (All Registrants) The Registrants’ commercial commitments as of September 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) $ 1,276 $ 1,193 $ 14 $ 22 $ 2 $ 1 $ 1 $ — $ — Surety bonds (b) 1,206 1,079 20 40 11 21 13 4 4 Financing trust guarantees 378 — 200 178 — — — — — Guaranteed lease residual values (c) 19 — — — — 19 6 7 5 Total commercial commitments $ 2,879 $ 2,272 $ 234 $ 240 $ 13 $ 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 $49 million , $14 million of which is a guarantee by Pepco, $19 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. As of September 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) $ 12 2018 6 2019 3 Total $ 21
Accrued environmental liabilities	of September 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: September 30, 2017 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 429 $ 327 Generation 76 — ComEd 294 293 PECO 33 32 BGE 3 2 PHI (Successor) 23 — Pepco 21 — DPL 1 — 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 —

Supplemental Financial Inform42

Supplemental Financial Information (Tables)	9 Months Ended
	Sep. 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 nine months ended September 30, 2017 and 2016 . Three Months Ended September 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 $ 159 $ 159 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 59 59 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 44 44 — — — — — — — Non-regulatory agreement units 111 111 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (4 ) (4 ) — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (161 ) (161 ) — — — — — — — Total decommissioning-related activities 208 208 — — — — — — — Investment income 2 1 — — — 1 1 — — Interest income related to uncertain income tax positions 4 — — — — — — — — AFUDC — Equity 17 — 2 2 4 9 6 2 1 Other 6 — 3 — — 3 — 2 — Other, net $ 237 $ 209 $ 5 $ 2 $ 4 $ 13 $ 7 $ 4 $ 1 Nine Months Ended September 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 $ 439 $ 439 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 165 165 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 253 253 — — — — — — — Non-regulatory agreement units 347 347 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (5 ) (5 ) — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (558 ) (558 ) — — — — — — — Total decommissioning-related activities 641 641 — — — — — — — Investment income 6 4 — — — 2 1 — — Interest income related to uncertain income tax positions 3 — — — — — — — — Benefit related to uncertain income tax positions (c) 2 — — — — — — — — AFUDC — Equity 51 — 6 6 12 27 17 5 5 Other 22 3 8 — — 11 4 5 1 Other, net $ 725 $ 648 $ 14 $ 6 $ 12 $ 40 $ 22 $ 10 $ 6 Three Months Ended September 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 $ 57 $ 57 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 35 35 — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 155 155 — — — — — — — Non-regulatory agreement units 116 116 — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (5 ) (5 ) — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (168 ) (168 ) — — — — — — — Total decommissioning-related activities 190 190 — — — — — — — Investment income (expense) 2 1 — (1 ) — — — — — Interest income related to uncertain income tax positions 8 — — — — — — — — Penalty related to uncertain income tax positions (c) (106 ) — (86 ) — — — — — — AFUDC — Equity 19 — 5 2 5 7 5 1 1 Other 7 (6 ) 1 1 — 12 7 2 1 Other, net $ 120 $ 185 $ (80 ) $ 2 $ 5 $ 19 $ 12 $ 3 $ 2 Successor Predecessor Nine Months Ended September 30, 2016 March 24, 2016 to September 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 $ 181 $ 181 $ — $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 95 95 — — — — — — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 286 286 — — — — — — — — Non-regulatory agreement units 216 216 — — — — — — — — Net unrealized losses on pledged assets Zion Station decommissioning (2 ) (2 ) — — — — — — — — Regulatory offset to decommissioning trust fund-related activities (b) (380 ) (380 ) — — — — — — — — Total decommissioning-related activities 396 396 — — — — — — — — Investment income (expense) 14 6 — (1 ) 2 — — — 1 — Long-term lease income 4 — — — — — — — — — Interest income related to uncertain income tax positions 13 — — — — 1 — 1 — — Penalty related to uncertain income tax positions (c) (106 ) — (86 ) — — — — — — — AFUDC — Equity 43 — 8 6 14 14 3 5 15 7 Loss on debt extinguishment (3 ) (2 ) — — — — — — — — Other 16 (5 ) 6 1 — 13 6 2 15 (11 ) Other, net $ 377 $ 395 $ (72 ) $ 6 $ 16 $ 28 $ 9 $ 8 $ 31 $ (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 nine months ended September 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 September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 245 $ 35 $ 65 $ 35 $ 22 $ 88 $ 83 $ 5 $ — Nine Months Ended September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 682 $ 97 $ 181 $ 95 $ 69 $ 240 $ 226 $ 14 $ — Three Months Ended September 30, 2016 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Utility taxes $ 255 $ 35 $ 67 $ 40 $ 21 $ 92 $ 87 $ 5 $ — Successor Predecessor Nine Months Ended September 30, 2016 March 24, 2016 to September 30, 2016 January 1, 2016 to March 23, 2016 Exelon Generation ComEd PECO BGE Pepco DPL ACE PHI PHI Utility taxes $ 624 $ 90 $ 186 $ 106 $ 66 $ 240 $ 14 $ — $ 176 $ 78
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 nine months ended September 30, 2017 and 2016 . Nine Months Ended September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Depreciation, amortization and accretion Property, plant and equipment (a) $ 2,416 $ 1,010 $ 579 $ 194 $ 233 $ 342 $ 153 $ 92 $ 66 Amortization of regulatory assets (a) 355 — 52 19 115 169 89 32 47 Amortization of intangible assets, net (a) 43 36 — — — — — — — Amortization of energy contract assets and liabilities (b) 19 19 — — — — — — — Nuclear fuel (c) 816 816 — — — — — — — ARO accretion (d) 350 350 — — — — — — — Total depreciation, amortization and accretion $ 3,999 $ 2,231 $ 631 $ 213 $ 348 $ 511 $ 242 $ 124 $ 113 Successor Predecessor Nine Months Ended September 30, 2016 March 24, 2016 to September 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) $ 2,490 $ 1,297 $ 524 $ 181 $ 223 $ 128 $ 82 $ 61 $ 215 $ 94 Amortization of regulatory assets (a) 293 — 49 20 84 93 38 69 140 58 Amortization of intangible assets, net (a) 38 32 — — — — — — — — Amortization of energy contract assets and liabilities (b) (7 ) (7 ) — — — — — — — — Nuclear fuel (c) 862 862 — — — — — — — — ARO accretion (d) 333 332 1 — — — — — — — Total depreciation, amortization and accretion $ 4,009 $ 2,516 $ 574 $ 201 $ 307 $ 221 $ 120 $ 130 $ 355 $ 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	Nine Months Ended September 30, 2017 Successor Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 482 $ 170 $ 131 $ 21 $ 47 $ 72 $ 19 $ 10 $ 10 Loss from equity method investments 26 26 — — — — — — — Provision for uncollectible accounts 103 31 25 17 4 26 11 1 14 Stock-based compensation costs 76 — — — — — — — — Other decommissioning-related activity (a) (213 ) (213 ) — — — — — — — Energy-related options (b) 15 15 — — — — — — — Amortization of regulatory asset related to debt costs 7 — 3 1 — 3 1 1 1 Amortization of rate stabilization deferral (7 ) — — — 7 (14 ) (12 ) (2 ) — Amortization of debt fair value adjustment (13 ) (9 ) — — — (4 ) — — — Discrete impacts from EIMA and FEJA (c) (61 ) — (61 ) — — — — — — Amortization of debt costs 57 33 3 1 1 1 1 — — Provision for excess and obsolete inventory 52 50 1 — — 1 — 1 — Merger-related commitments (d) — — — — — (8 ) (6 ) (2 ) — Severance costs 33 25 — — — 3 — — — Other 46 4 10 (2 ) (7 ) (14 ) (6 ) (3 ) (4 ) Total other non-cash operating activities $ 603 $ 132 $ 112 $ 38 $ 52 $ 66 $ 8 $ 6 $ 21 Non-cash investing and financing activities: Change in capital expenditures not paid $ (101 ) $ 20 $ (79 ) $ (29 ) $ 16 $ (6 ) $ 7 $ 14 $ (18 ) Fair value of pension obligation transferred in connection with the FitzPatrick acquisition — 33 — — — — — — — Change in PPE related to ARO update (141 ) (141 ) — — — — — — — Indemnification of like-kind exchange position (g) — — 21 — — — — — — Non-cash financing of capital projects 16 16 — — — — — — — Dividends on stock compensation 5 — — — — — — — — Dissolution of financing trust due to long-term debt retirement 8 — — — 8 — — — — Fair value adjustment of long-term debt due to retirement (5 ) — — — — — — — — Successor Predecessor Nine Months Ended September 30, 2016 March 24, 2016 to September 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 $ 458 $ 163 $ 124 $ 25 $ 50 $ 24 $ 13 $ 11 $ 58 $ 23 Loss from equity method investments 15 16 — — — — — — — — Provision for uncollectible accounts 107 14 31 24 12 15 12 18 27 16 Stock-based compensation costs 88 — — — — — — — — 3 Other decommissioning-related activity (a) (237 ) (237 ) — — — — — — — — Energy-related options (b) (20 ) (20 ) — — — — — — — — Amortization of regulatory asset related to debt costs 7 — 3 1 — 2 — 1 2 1 Amortization of rate stabilization deferral 62 — — — 62 3 3 — — 5 Amortization of debt fair value adjustment (9 ) (9 ) — — — — — — — — Discrete impacts from EIMA (c) (36 ) — (36 ) — — — — — — — Amortization of debt costs 26 12 (3 ) 2 3 — — — — — Provision for excess and obsolete inventory 74 70 4 — — 1 1 1 — 1 Merger-related commitments (d)(e) 508 3 — — — 125 73 110 308 — Severance costs 130 57 — — — — — — 53 — Asset retirement costs — — — — — — 5 2 — — Lower of cost or net realizable value inventory adjustment 36 36 — — — — — — — — Other 15 24 (1 ) (3 ) (18 ) (2 ) (8 ) (5 ) (7 ) (3 ) Total other non-cash operating activities $ 1,224 $ 129 $ 122 $ 49 $ 109 $ 168 $ 99 $ 138 $ 441 $ 46 Non-cash investing and financing activities: Change in capital expenditures not paid $ (338 ) $ (289 ) $ (42 ) $ (4 ) $ 17 $ 15 $ (10 ) $ 2 $ (5 ) $ 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) — — — — — — — — 129 — 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 476 476 — — — — — — — — Indemnification of like-kind exchange position (g) — — 157 — — — — — — — Non-cash financing of capital projects 84 84 — — — — — — — — 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 12 — 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 September 30, 2017 and December 31, 2016 . Successor September 30, 2017 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Property, plant and equipment: Accumulated depreciation and amortization $ 20,591 (a) $ 11,193 (a) $ 4,191 $ 3,366 $ 3,351 $ 448 $ 3,171 $ 1,231 $ 1,060 Accounts receivable: Allowance for uncollectible accounts $ 339 $ 111 $ 72 $ 57 $ 25 $ 74 $ 29 $ 17 $ 28 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 $3,303 million . (b) Includes accumulated amortization of nuclear fuel in the reactor core of $3,186 million

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Analysis and reconciliation of reportable segment information	Nine Months Ended September 30, 2017 and 2016 Successor Generation (a) ComEd PECO BGE PHI (b) Other (c) Intersegment Exelon Operating revenues (d) : 2017 Competitive businesses electric revenues $ 11,485 $ — $ — $ — $ — $ — $ (888 ) $ 10,597 Competitive businesses natural gas revenues 1,807 — — — — — — 1,807 Competitive businesses other revenues 520 — — — — — — 520 Rate-regulated electric revenues — 4,227 1,802 1,895 3,417 — (23 ) 11,318 Rate-regulated natural gas revenues — — 339 468 105 — (6 ) 906 Shared service and other revenues — — — — 35 1,316 (1,350 ) 1 2016 Competitive businesses electric revenues $ 11,677 $ — $ — $ — $ — $ — $ (1,118 ) $ 10,559 Competitive businesses natural gas revenues 1,515 — — — — — — 1,515 Competitive businesses other revenues 171 — — — — — (2 ) 169 Rate-regulated electric revenues — 4,031 1,971 1,998 2,485 — (24 ) 10,461 Rate-regulated natural gas revenues — — 322 423 46 — (10 ) 781 Shared service and other revenues — — — — 34 1,166 (1,199 ) 1 Intersegment revenues (e) : 2017 $ 888 $ 12 $ 5 $ 12 $ 35 $ 1,312 $ (2,262 ) $ 2 2016 1,121 12 5 16 34 1,166 (2,351 ) 3 Net income (loss): 2017 $ 491 $ 447 $ 327 $ 231 $ 359 $ 58 $ (2 ) $ 1,911 2016 556 297 346 191 (91 ) (340 ) (3 ) 956 _________ (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 nine months ended September 30, 2017 include revenue from sales to PECO of $111 million , sales to BGE of $330 million , sales to Pepco of $209 million , sales to DPL of $138 million , and sales to ACE of $23 million in the Mid-Atlantic region, and sales to ComEd of $77 million in the Midwest region. For the nine months ended September 30, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $234 million and sales to BGE of $489 million in the Mid-Atlantic region, and sales to ComEd of $38 million in the Midwest region. For the Successor period of March 24, 2016 to September 30, 2016 , intersegment revenues for Generation include revenue from sales to Pepco of $223 million , sales to DPL of $109 million , and sales to ACE of $28 million in the Mid-Atlantic region. (b) Amounts included represent activity for PHI's successor period, nine months ended September 30, 2017 and March 24, 2016 through September 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 19 — Supplemental Financial Information for total utility taxes for the nine months ended September 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) : Nine Months Ended September 30, 2017 - Successor Rate-regulated electric revenues $ 1,649 $ 866 $ 915 $ — $ (13 ) $ 3,417 Rate-regulated natural gas revenues — 105 — — — 105 Shared service and other revenues — — — 37 (2 ) 35 March 24, 2016 to September 30, 2016 - Successor Rate-regulated electric revenues $ 1,184 $ 593 $ 714 $ 3 $ (9 ) $ 2,485 Rate-regulated natural gas revenues — 46 — — — 46 Shared service and other revenues — — — 34 — 34 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: Nine Months Ended September 30, 2017 - Successor $ 4 $ 6 $ 2 $ 37 $ (14 ) $ 35 March 24, 2016 to September 30, 2016 - Successor 2 4 2 35 (9 ) 34 January 1, 2016 to March 23, 2016 - Predecessor 1 2 1 — (4 ) — Net income (loss): Nine Months Ended September 30, 2017 - Successor $ 188 $ 107 $ 77 $ (48 ) $ 35 $ 359 March 24, 2016 to September 30, 2016 - Successor (12 ) (42 ) (55 ) (16 ) 34 (91 ) 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 19 — Supplemental Financial Information for total utility taxes for the nine months ended September 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 nine months ended September 30, 2017 and 2016 is as follows: Three Months Ended September 30, 2017 and 2016 Successor Generation (a) ComEd PECO BGE PHI (b) Other (c) Intersegment Exelon Operating revenues (d) : 2017 Competitive businesses electric revenues $ 4,042 $ — $ — $ — $ — $ — $ (295 ) $ 3,747 Competitive businesses natural gas revenues 460 — — — — — — 460 Competitive businesses other revenues 249 — — — — — — 249 Rate-regulated electric revenues — 1,571 662 658 1,280 — (7 ) 4,164 Rate-regulated natural gas revenues — — 53 80 18 — (2 ) 149 Shared service and other revenues — — — — 12 446 (458 ) — 2016 Competitive businesses electric revenues $ 4,322 $ — $ — $ — $ — $ — $ (499 ) $ 3,823 Competitive businesses natural gas revenues 326 — — — — — — 326 Competitive businesses other revenues 387 — — — — — (1 ) 386 Rate-regulated electric revenues — 1,497 740 735 1,366 — (8 ) 4,330 Rate-regulated natural gas revenues — — 48 77 17 — (5 ) 137 Shared service and other revenues — — — — 11 362 (373 ) — Intersegment revenues (e) : 2017 $ 294 $ 3 $ 2 $ 3 $ 12 $ 445 $ (759 ) $ — 2016 500 4 2 7 11 362 (885 ) 1 Net income (loss): 2017 $ 348 $ 189 $ 112 $ 62 $ 153 $ 3 $ — $ 867 2016 271 37 122 56 166 (125 ) (1 ) 526 Total assets: September 30, 2017 $ 47,744 $ 29,649 $ 11,480 $ 8,923 $ 21,301 $ 10,662 $ (11,286 ) $ 118,473 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 September 30, 2017 include revenue from sales to PECO of $31 million , sales to BGE of $98 million , sales to Pepco of $57 million , sales to DPL of $47 million , and sales to ACE of $7 million in the Mid-Atlantic region, and sales to ComEd of $54 million in the Midwest region. For the three months ended September 30, 2016 , intersegment revenues for Generation include revenue from sales to PECO of $91 million , sales to BGE of $183 million , sales to Pepco of $128 million , sales to DPL of $63 million , and sales to ACE of $15 million in the Mid-Atlantic region, and sales to ComEd of $20 million in the Midwest region. (b) Amounts included represent activity for PHI's successor period, three months ended September 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 19 — Supplemental Financial Information for total utility taxes for the three months ended September 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 September 30, 2017 - Successor Rate-regulated electric revenues $ 604 $ 309 $ 370 $ — $ (3 ) $ 1,280 Rate-regulated natural gas revenues — 18 — — — 18 Shared service and other revenues — — — 12 — 12 Three Months Ended September 30, 2016 - Successor Rate-regulated electric revenues $ 635 $ 314 $ 421 $ — $ (4 ) $ 1,366 Rate-regulated natural gas revenues — 17 — — — 17 Shared service and other revenues — — — 11 — 11 Intersegment revenues: Three Months Ended September 30, 2017 - Successor $ 1 $ 2 $ — $ 13 $ (4 ) $ 12 Three Months Ended September 30, 2016 - Successor 1 2 1 11 (4 ) 11 Net income (loss): Three Months Ended September 30, 2017 - Successor $ 87 $ 31 $ 41 $ (18 ) $ 12 $ 153 Three Months Ended September 30, 2016 - Successor 79 44 47 (15 ) 11 166 Total assets: September 30, 2017 - Successor $ 7,775 $ 4,276 $ 3,510 $ 10,724 $ (4,984 ) $ 21,301 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 19 — Supplemental Financial Information for total utility taxes for the three months ended September 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: Nine Months Ended September 30, 2017 Nine Months Ended September 30, 2016 Revenues (a) Intersegment Total Revenues (a) Intersegment Total Mid-Atlantic $ 4,207 $ 15 $ 4,222 $ 4,776 $ (40 ) $ 4,736 Midwest 3,158 (17 ) 3,141 3,330 13 3,343 New England 1,469 (8 ) 1,461 1,278 (6 ) 1,272 New York 1,095 (14 ) 1,081 906 (33 ) 873 ERCOT 749 4 753 659 6 665 Other Power Regions 807 (28 ) 779 728 (42 ) 686 Total Revenues for Reportable Segments 11,485 (48 ) 11,437 11,677 (102 ) 11,575 Other (b) 2,327 48 2,375 1,686 102 1,788 Total Generation Consolidated Operating Revenues $ 13,812 $ — $ 13,812 $ 13,363 $ — $ 13,363 _________ (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 $30 million and $10 million decrease to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the nine months ended September 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $47 million and $366 million for the nine months ended September 30, 2017 and 2016 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Nine Months Ended September 30, 2017 Nine Months Ended September 30, 2016 RNF from external customers (a) Intersegment RNF Total RNF RNF from external customers (a) Intersegment RNF Total RNF Mid-Atlantic $ 2,330 $ 81 $ 2,411 $ 2,541 $ 15 $ 2,556 Midwest 2,129 11 2,140 2,225 4 2,229 New England 423 (20 ) 403 373 (23 ) 350 New York 679 (1 ) 678 607 (15 ) 592 ERCOT 446 (188 ) 258 335 (104 ) 231 Other Power Regions 359 (139 ) 220 357 (104 ) 253 Total Revenues net of purchased power and fuel expense for Reportable Segments 6,366 (256 ) 6,110 6,438 (227 ) 6,211 Other (b) 160 256 416 316 227 543 Total Generation Revenues net of purchased power and fuel expense $ 6,526 $ — $ 6,526 $ 6,754 $ — $ 6,754 _________ (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 $41 million and $15 million decrease to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the nine months ended September 30, 2017 and 2016 , respectively, unrealized mark-to-market losses of $161 million and $113 million for the nine months ended September 30, 2017 and 2016 , respectively, accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 7 - Early Nuclear Plant Retirements of the Combined Notes to Consolidated Financial Statements of $8 million and $38 million decrease to revenue net of purchased power and fuel expense for the nine months ended September 30, 2017 and 2016, respectively, and the elimination of intersegment revenue net of purchased power and fuel expense. Generation total revenues: Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 Revenues (a) Intersegment Total Revenues (a) Intersegment Total Mid-Atlantic $ 1,421 $ 11 $ 1,432 $ 1,813 $ (13 ) $ 1,800 Midwest 1,049 (11 ) 1,038 1,163 1 1,164 New England 482 (1 ) 481 455 (4 ) 451 New York 434 (6 ) 428 331 (8 ) 323 ERCOT 308 6 314 289 6 295 Other Power Regions 348 (13 ) 335 271 (33 ) 238 Total Revenues for Reportable Segments 4,042 (14 ) 4,028 4,322 (51 ) 4,271 Other (b) 709 14 723 713 51 764 Total Generation Consolidated Operating Revenues $ 4,751 $ — $ 4,751 $ 5,035 $ — $ 5,035 _________ (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 $13 million and $21 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 September 30, 2017 and 2016 , respectively, unrealized mark-to-market gain of $52 million and $187 million for the three months ended September 30, 2017 and 2016 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Three Months Ended September 30, 2017 Three Months Ended September 30, 2016 RNF (a) Intersegment RNF Total RNF RNF (a) Intersegment RNF Total RNF Mid-Atlantic $ 817 $ 38 $ 855 $ 881 $ 6 $ 887 Midwest 697 — 697 782 (1 ) 781 New England 151 (6 ) 145 170 (10 ) 160 New York 296 — 296 195 (1 ) 194 ERCOT 229 (111 ) 118 144 (51 ) 93 Other Power Regions 118 (50 ) 68 143 (66 ) 77 Total Revenues net of purchased power and fuel for Reportable Segments 2,308 (129 ) 2,179 2,315 (123 ) 2,192 Other (b) 112 129 241 131 123 254 Total Generation Revenues net of purchased power and fuel expense $ 2,420 $ — $ 2,420 $ 2,446 $ — $ 2,446 _________ (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 $19 million and $22 million decrease to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the three months ended September 30, 2017 and 2016 , respectively, unrealized mark-to-market gains of $73 million and $88 million for the three months ended September 30, 2017 and 2016 , respectively, accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 7 - Early Nuclear Plant Retirements of the Combined Notes to Consolidated Financial Statements of $6 million and $28 million decrease to revenue net of purchased power and fuel expense for the three months ended September 30, 2017 and 2016, respectively, and the elimination of intersegment revenue net of purchased power and fuel expense.

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details) $ in Millions		1 Months Ended			3 Months Ended			9 Months Ended
		Jul. 31, 2017USD ($)	Nov. 30, 2015	Jun. 30, 2015	Sep. 30, 2017USD ($)VIE	Jun. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)VIE	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)VIE	Apr. 01, 2014USD ($)
Variable Interest Entity [Line Items]
Number Of Variable Interest Entities Consolidated | VIE					6			6		9
Number of Variable Interest Entities not consolidated by equity holders | VIE					7			7		8
Guarantor Obligations, Maximum Exposure, Undiscounted					$ 49			$ 49
Other Nonconsolidated Variable Interest Entity Ownership Interests	[1]				627			627		$ 455
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount					17			17
Payment Guarantee [Member] | Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted											$ 245
Financial Guarantee [Member] | Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted											165
ExGen Renewables Holdings, LLC [Member]
Variable Interest Entity [Line Items]
Proceeds from Sale of Interest in Partnership Unit		$ 400
ExGen Renewables Holdings, LLC [Member] | Equity interest member [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage		49.00%
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value						$ 75
Variable Interest Entity, Financial or Other Support, Amount								$ 31
Related Party Purchase Of Nuclear Output By Third Party Percentage								50.01%
Guarantor Obligations, Liquidation Proceeds, Percentage								49.99%
Other Nonconsolidated Variable Interest Entity Ownership Interests					17			$ 17
Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Receivables from affiliates					328			328			$ 400
Exelon Generation Co L L C [Member] | Distributed Energy Company [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests					227			227
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value					8			8
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value					637			637
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			275
Exelon Generation Co L L C [Member] | Equity interest member [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage					99.00%	90.00%
Exelon Generation Co L L C [Member] | Payment Guarantee [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value						$ 275
Baltimore Gas and Electric Company [Member] | RSB Bond Co LLC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Financial or Other Support, Amount							$ 27	22	$ 64
2015 ESA Investco, LLC [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage				99.00%
2015 ESA Investco, LLC [Member] | Equity interest member [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage			69.00%	90.00%
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted					$ 13			13
Atlantic City Electric Company [Member] | ATF [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Financial or Other Support, Amount					$ 11		$ 20	$ 39	$ 47
[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		Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Current assets	[1]	$ 657	$ 954	[2]
Noncurrent assets	[1]	9,252	8,563	[2]
Total assets	[1]	9,909	9,517	[2]
Current liabilities	[1]	404	885	[2]
Noncurrent liabilities	[1]	3,290	2,713	[2]
Total liabilities	[1]	3,694	3,598	[2]
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Current assets		644	916
Noncurrent assets		9,222	8,525
Total assets		9,866	9,441
Current liabilities		367	802
Noncurrent liabilities		3,215	2,612
Total liabilities		3,582	3,414
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Current assets			23
Noncurrent assets			3
Total assets			26
Current liabilities			42
Noncurrent liabilities			0
Total liabilities			42
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Current assets	[1]	13	14
Noncurrent assets	[1]	30	35
Total assets	[1]	43	49
Current liabilities	[1]	37	42
Noncurrent liabilities	[1]	75	101
Total liabilities	[1]	112	143
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Current assets		9	9
Noncurrent assets		22	23
Total assets		31	32
Current liabilities		33	37
Noncurrent liabilities		67	89
Total liabilities		$ 100	$ 126
[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		Sep. 30, 2017	Dec. 31, 2016		Sep. 30, 2016	Mar. 23, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 1,203	$ 635		$ 1,897		$ 6,502
Restricted cash		320	253
Accounts receivable, net
Customer		3,854	4,158
Other		950	1,201
Mark-to-market derivatives assets		699	917
Inventory
Materials and supplies		1,281	1,274
Other current assets		1,435	930
Total current assets		12,724	12,412
Property, plant and equipment, net		73,067	71,555
Nuclear decommissioning trust funds		12,966	11,061
Goodwill		6,677	6,677
Mark-to-market derivative assets		426	492
Other noncurrent assets		1,277	1,472
Total assets		118,473	114,904
Long-term debt due within one year		3,164	2,430
Accounts payable		3,132	3,441
Accrued expenses		3,080	3,460
Mark-to-market derivative liabilities		178	282
Unamortized energy contract liabilities		283	407
Other		933	981
Total current liabilities		12,395	13,457
Long-term debt		31,701	31,575
Asset retirement obligations		9,733	9,111
Pension obligation(c)		4,055	4,248
Unamortized energy contract liabilities		656	830
Other noncurrent liabilities		1,899	1,827
Total liabilities	[1]	88,156	87,292
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents	[2]	130	150	[3]
Restricted cash	[2]	85	59	[3]
Accounts receivable, net
Customer	[2]	139	371	[3]
Other	[2]	25	48	[3]
Mark-to-market derivatives assets	[2]	0	31	[3]
Inventory
Materials and supplies	[2]	196	199	[3]
Other current assets	[2]	56	50	[3]
Total current assets	[2]	631	908	[3]
Property, plant and equipment, net	[2]	6,213	5,415	[3]
Nuclear decommissioning trust funds	[2]	2,415	2,185	[3]
Goodwill	[2]	0	47	[3]
Mark-to-market derivative assets	[2]	0	23	[3]
Other noncurrent assets	[2]	261	315	[3]
Total noncurrent assets	[2]	8,889	7,985	[3]
Total assets	[2]	9,520	8,893	[3]
Long-term debt due within one year	[2]	182	181	[3]
Accounts payable	[2]	104	269	[3]
Accrued expenses	[2]	90	119	[3]
Mark-to-market derivative liabilities	[2]	0	60	[3]
Unamortized energy contract liabilities	[2]	17	15	[3]
Other	[2]	11	30	[3]
Total current liabilities	[2]	404	674	[3]
Long-term debt	[2]	1,172	641	[3]
Asset retirement obligations	[2]	2,009	1,904	[3]
Pension obligation(c)	[2],[4]	0	9	[3]
Unamortized energy contract liabilities	[2]	9	22	[3]
Other noncurrent liabilities	[2]	94	106	[3]
Total noncurrent liabilities	[2]	3,284	2,682	[3]
Total liabilities	[2]	3,688	3,356	[3]
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		360	290		375		431
Restricted cash		186	158
Accounts receivable, net
Customer		2,339	2,433
Other		275	558
Mark-to-market derivatives assets		699	917
Inventory
Materials and supplies		917	935
Other current assets		1,157	701
Total current assets		6,439	6,528
Property, plant and equipment, net		24,793	25,585
Nuclear decommissioning trust funds		12,966	11,061
Goodwill		47	47
Mark-to-market derivative assets		416	476
Other noncurrent assets		648	688
Total assets		47,744	46,974
Long-term debt due within one year		1,659	1,117
Accounts payable		1,492	1,610
Accrued expenses		797	989
Mark-to-market derivative liabilities		158	263
Unamortized energy contract liabilities		52	72
Other		266	313
Total current liabilities		5,059	5,683
Long-term debt		6,956	7,202
Asset retirement obligations		9,548	8,922
Unamortized energy contract liabilities		57	80
Other noncurrent liabilities		632	595
Total liabilities	[5]	33,947	33,718
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		130	150
Restricted cash		76	27
Accounts receivable, net
Customer		139	371
Other		25	48
Mark-to-market derivatives assets		0	31
Inventory
Materials and supplies		196	199
Other current assets		52	44
Total current assets		618	870
Property, plant and equipment, net		6,213	5,415
Nuclear decommissioning trust funds		2,415	2,185
Goodwill		0	47
Mark-to-market derivative assets		0	23
Other noncurrent assets		231	277
Total noncurrent assets		8,859	7,947
Total assets		9,477	8,817
Long-term debt due within one year		146	99
Accounts payable		104	269
Accrued expenses		89	116
Mark-to-market derivative liabilities		0	60
Unamortized energy contract liabilities		17	15
Other		11	30
Total current liabilities		367	589
Long-term debt		1,097	540
Asset retirement obligations		2,009	1,904
Pension obligation(c)	[4]	0	9
Unamortized energy contract liabilities		9	22
Other noncurrent liabilities		94	106
Total noncurrent liabilities		3,209	2,581
Total liabilities		3,576	3,170
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		29	23		341		9
Restricted cash		1	24
Accounts receivable, net
Customer		288	395
Other		86	102
Inventory
Materials and supplies		40	38
Other current assets		4	7
Total current assets		702	842
Property, plant and equipment, net		7,418	7,040
Other noncurrent assets		4	9
Total assets	[6]	8,923	8,704
Long-term debt due within one year		0	41
Accounts payable		218	205
Accrued expenses		147	175
Other		28	26
Total current liabilities		612	707
Long-term debt		2,577	2,281
Asset retirement obligations		23	21
Other noncurrent liabilities		52	61
Total liabilities	[6]	5,915	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			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		137	170		299	$ 319
Restricted cash		43	43
Accounts receivable, net
Customer		490	496
Other		209	283
Mark-to-market derivatives assets		0	0
Inventory
Materials and supplies		141	116
Other current assets		59	71
Total current assets		1,656	1,838
Property, plant and equipment, net		12,219	11,598
Goodwill		4,005	4,005
Mark-to-market derivative assets		0	0
Other noncurrent assets		77	81
Total assets	[7]	21,301	21,025
Long-term debt due within one year		159	253
Accounts payable		397	458
Accrued expenses		294	272
Mark-to-market derivative liabilities		0	0
Unamortized energy contract liabilities		231	335
Other		41	47
Total current liabilities		1,557	2,284
Long-term debt		5,771	5,645
Asset retirement obligations		17	14
Unamortized energy contract liabilities		599	750
Other noncurrent liabilities		214	249
Total liabilities		12,435	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]	9	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]	13	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]	30	35
Total noncurrent assets	[2]	30	35
Total assets	[2]	43	49
Long-term debt due within one year	[2]	36	40
Accounts payable	[2]	0	0
Accrued expenses	[2]	1	2
Mark-to-market derivative liabilities	[2]	0	0
Unamortized energy contract liabilities	[2]	0	0
Other	[2]	0	0
Total current liabilities	[2]	37	42
Long-term debt	[2]	75	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]	75	101
Total liabilities	[2]	112	143
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		5	101		$ 165		$ 3
Restricted cash		9	9
Accounts receivable, net
Customer		107	125
Other		54	44
Inventory
Materials and supplies		29	22
Other current assets		3	2
Total current assets		309	399
Property, plant and equipment, net		2,662	2,521
Other noncurrent assets		42	44
Total assets	[8]	3,510	3,457
Long-term debt due within one year		32	35
Accounts payable		122	132
Accrued expenses		39	38
Other		6	8
Total current liabilities		345	320
Long-term debt		1,098	1,120
Other noncurrent liabilities		25	32
Total liabilities		2,452	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		9	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		9	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		22	23
Total noncurrent assets		22	23
Total assets		31	32
Long-term debt due within one year		32	35
Accounts payable		0	0
Accrued expenses		1	2
Mark-to-market derivative liabilities		0	0
Unamortized energy contract liabilities		0	0
Other		0	0
Total current liabilities		33	37
Long-term debt		67	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		67	89
Total liabilities		$ 100	$ 126
[1]	Exelon’s consolidated assets include $9,520 million and $8,893 million at September 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 $3,688 million and $3,356 million at September 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 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 14 - Retirement Benefits for additional details.
[5]	Generation’s consolidated assets include $9,477 million and $8,817 million at September 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 $3,576 million and $3,170 million at September 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 no longer has interests in any VIEs as of September 30, 2017. See Note 3 - Variable Interest Entities.
[7]	PHI’s consolidated total assets include $43 million and $49 million at September 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 $112 million and $143 million at September 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 $31 million and $32 million at September 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 $100 million and $126 million at September 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		Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Total assets	[1]	$ 1,154	$ 1,205
Total liabilities	[1]	268	502
Exelon's ownership interest in VIE	[1]	259	248
Other ownership interests in VIE	[1]	627	455
Registrants' maximum exposure to loss		17
Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		259	264
Contract intangible asset
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Debt and payment guarantees
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	3
Net assets pledged for Zion Station decommissioning(b)
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	4	9
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	635	638
Total liabilities	[1]	39	215
Exelon's ownership interest in VIE	[1]	0	0
Other ownership interests in VIE	[1]	596	423
Commercial Agreement Variable Interest Entities [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Commercial Agreement Variable Interest Entities [Member] | Contract intangible asset
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Commercial Agreement Variable Interest Entities [Member] | Debt and payment guarantees
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Commercial Agreement Variable Interest Entities [Member] | Net assets pledged for Zion Station decommissioning(b)
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	4	9
Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	519	567
Total liabilities	[1]	229	287
Exelon's ownership interest in VIE	[1]	259	248
Other ownership interests in VIE	[1]	31	32
Equity Investment VIE [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		259	264
Equity Investment VIE [Member] | Contract intangible asset
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Equity Investment VIE [Member] | Debt and payment guarantees
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	3
Equity Investment VIE [Member] | Net assets pledged for Zion Station decommissioning(b)
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		17
Held-to-maturity Securities Pledged as Collateral		57	113
Accounts Payable, Interest-bearing, Noncurrent	[3]	$ 53	$ 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 $57 million and $113 million as of September 30, 2017 and December 31, 2016, respectively; offset by payables to ZionSolutions LLC of $53 million and $104 million as of September 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 13 - Nuclear Decommissioning for additional details.
[3]	Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT funds. The NDT funds will be utilized to satisfy the tax obligations as gains and losses are realized.

Mergers, Acquisitions, and Di48

Mergers, Acquisitions, and Dispositions - Narrative (Details) $ / shares in Units, MW in Millions, $ in Millions		Mar. 31, 2017USD ($)	Sep. 01, 2016USD ($)	May 02, 2016USD ($)	Apr. 21, 2016USD ($)	Mar. 23, 2016USD ($)	Jul. 31, 2016USD ($)	Sep. 30, 2017USD ($)MW	Sep. 30, 2016USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)MW	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)	Mar. 24, 2016USD ($)$ / shares
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross											$ 208	$ 6,896
Business Combination, Bargain Purchase, Gain Recognized, Amount								$ 7	$ 0		233	0
Business Combination, Integration Related Costs	[1],[2]							(8)	20		10	123
Other Commitment								2,879			2,879
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
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	[3]					7,142
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
ConEdison Solutions [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross			$ 257
Net Working Capital			204
Goodwill			100
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			$ 257
Fitzpatrick [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 289
Business Combination, Bargain Purchase, Gain Recognized, Amount								7			233
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		522
Fitzpatrick [Member] | Cash and Cash Equivalents [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		110
Business Combination, Consideration Transferred, Other		125
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											208	255
Business Combination, Bargain Purchase, Gain Recognized, Amount								7	0		233	0
Business Combination, Integration Related Costs	[2]							5	9		18	29
Other Commitment								2,272			2,272
Members' Capital								9,357			9,357		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		289
Business Combination, Consideration Transferred, Other		179
Payments to Acquire Businesses, Gross											289
Business Combination, Integration Related Costs								6			53
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net								3			3
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								4			235
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]
Business Combination, Integration Related Costs	[2],[4]							(15)	7	$ 63
Members' Capital								8,835			8,835		$ 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]
Business Combination, Integration Related Costs	[2],[5]							(8)	3		(6)	26
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],[6]							1	2		(6)	18
Other Commitment								11			11
Goodwill								1,100			1,100
Gain (Loss) on Disposition of Property Plant Equipment							$ 4
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]							(8)	2		(6)	17
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]	.
[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]	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.
[4]	For the three and nine months ended September 30, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $16 million and $24 million, respectively, incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. For the Successor period March 24, 2016 to September 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $13 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.
[5]	For the three and nine months ended September 30, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. For the nine months ended September 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $10 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]	For the nine months ended September 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 nine months ended September 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		Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Business Combination, Bargain Purchase, Gain Recognized, Amount			$ 7	$ 0	$ 233	$ 0
Fitzpatrick [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 289
Current assets		60
Property, plant and equipment		298
Nuclear decommissioning trust funds		807
Other assets	[1]	114
Total assets		1,279
Current liabilities		6
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities		444
Pension and OPEB obligations		33
Deferred income taxes		149
Spent nuclear fuel obligation		110
Other liabilities		15
Total liabilities		757
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		522
Business Combination, Bargain Purchase, Gain Recognized, Amount			7		233
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		125
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	Sep. 30, 2017	Dec. 31, 2016
Other Commitments [Line Items]
Other Commitment	$ 2,879
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	Sep. 30, 2017	Sep. 30, 2016
Payments to Acquire Businesses, Gross			$ 208	$ 6,896
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]	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]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities	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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 8,769	$ 9,002	$ 25,149	$ 23,486
Net income	867	526	1,911	956
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues	1,347	1,437	3,679	2,656
Net income	$ 176	$ 169	$ 382	$ (92)

Mergers, Acquisitions, and Di54

Mergers, Acquisitions, and Dispositions Merger Integration Related Costs Table (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended	9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Mar. 23, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Combination, Integration Related Costs	[1],[2]	$ (8)	$ 20			$ 10	$ 123
Exelon Generation Co L L C [Member]
Business Combination, Integration Related Costs	[2]	5	9			18	29
Commonwealth Edison Co [Member]
Business Combination, Integration Related Costs	[2],[3]	0	0			1	(6)
PECO Energy Co [Member]
Business Combination, Integration Related Costs	[2]	1	1			3	3
Baltimore Gas and Electric Company [Member]
Business Combination, Integration Related Costs	[2],[4]	1	1			3	(3)
Potomac Electric Power Company [Member]
Business Combination, Integration Related Costs	[2],[5]	(8)	3			(6)	26
Delmarva Power and Light Company [Member]
Business Combination, Integration Related Costs	[2],[6]	1	2			(6)	18
Atlantic City Electric Company [Member]
Business Combination, Integration Related Costs	[2]	(8)	2			(6)	17
Successor [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs	[2],[7]	(15)	$ 7		$ 63
Predecessor [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs	[2],[7]			$ 29		(17)
Regulatory Assets [Member] | Commonwealth Edison Co [Member]
Business Combination, Integration Related Costs							8
Regulatory Assets [Member] | Baltimore Gas and Electric Company [Member]
Business Combination, Integration Related Costs							6
Regulatory Assets [Member] | Pepco Holdings LLC [Member]
Business Combination, Integration Related Costs		$ 16				24	13
Regulatory Assets [Member] | Potomac Electric Power Company [Member]
Business Combination, Integration Related Costs						8	10
Regulatory Assets [Member] | Delmarva Power and Light Company [Member]
Business Combination, Integration Related Costs						8	$ 3
Regulatory Assets [Member] | Atlantic City Electric Company [Member]
Business Combination, Integration Related Costs						$ 8
[1]	.
[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 nine months ended September 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]	For the nine months ended September 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]	For the three and nine months ended September 30, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $8 million incurred at Pepco that have been deferred and recorded as a regulatory asset for anticipated recovery. For the nine months ended September 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $10 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]	For the nine months ended September 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 nine months ended September 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]	For the three and nine months ended September 30, 2017, includes the reversal of previously incurred acquisition, integration and financing costs of $16 million and $24 million, respectively, incurred at PHI that have been deferred and recorded as a regulatory asset for anticipated recovery. For the Successor period March 24, 2016 to September 30, 2016, includes the reversal of previously incurred acquisition, integration and financing costs of $13 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		9 Months Ended				12 Months Ended
	Sep. 30, 2016		Sep. 30, 2017	[3],[4]	Sep. 30, 2016		Dec. 31, 2016
Business Acquisition, Pro Forma Revenue	$ 9,002	[1]			$ 24,468	[1]	$ 32,342	[2]
Business Acquisition, Pro Forma Net Income (Loss)	$ 501	[1]			$ 1,346	[1]	$ 1,562	[2]
Business Acquisition, Pro Forma Earnings Per Share, Basic	$ 0.54	[1]			$ 1.46	[1]	$ 1.69	[2]
Business Acquisition, Pro Forma Earnings Per Share, Diluted	$ 0.54	[1]			$ 1.45	[1]	$ 1.69	[2]
Noncash Merger Related Costs			$ 0		$ 508
Pepco Holdings LLC [Member]
Noncash Merger Related Costs	$ 20				660		$ 680
Pepco Holdings LLC [Member] | Consolidation, Eliminations [Member]
Business Acquisition, Pro Forma Revenue					$ 171		$ 171
[1]	The amounts above include adjustments for non-recurring costs directly related to the merger of $20 million and $660 million for the three and nine months ended September 30, 2016, respectively, and intercompany revenue of $171 million for the nine months ended September 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.

Mergers, Acquisitions, and Di56

Mergers, Acquisitions, and Dispositions Purchase Price Allocation Table - ConEdison (Details) - USD ($) $ in Millions	Sep. 01, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 208	$ 6,896
ConEdison Solutions [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 257
Net Working Capital	204
Property, plant and equipment	2
Nuclear decommissioning trust funds	6
Goodwill	100
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill	9
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Other	1
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	322
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities	65
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	65
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 257

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details) MWh in Millions, $ in Millions		Dec. 31, 2030	Oct. 27, 2017USD ($)	Oct. 20, 2017USD ($)	Sep. 28, 2017USD ($)	Sep. 11, 2017USD ($)	Sep. 08, 2017USD ($)	Aug. 17, 2017USD ($)	Jul. 25, 2017USD ($)	Jul. 14, 2017USD ($)	Jun. 14, 2017USD ($)	Jun. 09, 2017USD ($)	Apr. 06, 2017USD ($)	Mar. 30, 2017USD ($)	Mar. 24, 2017USD ($)	Mar. 22, 2017USD ($)	Mar. 08, 2017USD ($)	Feb. 15, 2017USD ($)	Feb. 01, 2017USD ($)	Dec. 17, 2016USD ($)	Dec. 06, 2016USD ($)	Jul. 16, 2016USD ($)	May 17, 2016USD ($)	Oct. 22, 2015USD ($)	Jun. 30, 2017USD ($)	Apr. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Sep. 30, 2017USD ($)Monetary_per_DecimalMWh		Sep. 30, 2016USD ($)	Dec. 31, 2017	Dec. 31, 2016USD ($)	Dec. 31, 2030USD ($)	Jun. 01, 2019	Jun. 01, 2018	Aug. 01, 2017USD ($)	Jul. 21, 2017USD ($)	Jun. 01, 2017	Aug. 31, 2010USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											$ 5,102						$ 5,102				$ 4,789
Regulatory Assets																											11,502						11,502				11,388
Regulatory Liability, Current																											553						553				602
Regulatory Liability, Noncurrent																											4,549						4,549				4,187
Other Commitment																											2,879						2,879
Revenues																											8,769			$ 9,002			25,149		$ 23,486
Fair Value, Net Asset (Liability)																											2,400						2,400
AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											660						660				701
Zero Emission Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											71						71
Renewable Portfolio Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											46						46
Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											62						62				185
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation																																										$ 235
Customer Refund Liability, Noncurrent																													$ 20
Other Commitment																											2,272						2,272
Revenues																									$ 12		4,751			5,035			13,812		13,363
License Costs																																	30
Exelon Generation Co L L C [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues																										$ 101
Exelon Generation Co L L C [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation																											3						3
Exelon Generation Co L L C [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Purchase Obligation																											7						7
Exelon Generation Co L L C [Member] | Zero Emission Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenues																											118						191
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]																																11
Public Utilities, Requested Increase (Decrease), Amount												$ 7																					$ 44	[1]
Public Utilities, Approved Rate Increase (Decrease), Amount						$ 12
Public Utilities, Approved Return on Equity, Percentage						8.40%																											11.50%	[1],[2]
Public Utilities, Approved Equity Capital Structure, Percentage						6.47%																											8.43%	[1],[3]
SocialCarbonCost | Monetary_per_Decimal																																	16.5
Purchase Obligation																																										$ 170
Regulatory Liabilities																											3,984						$ 3,984				3,698
DecouplingImpactOnOperatingRevenuesAndRegulatoryAssets																																	21
LowIncomeEnergyAssistanceContributionAnnual																																	$ 10
LowIncomeEnergyAssistanceContributionLength																																	5
Low Income Sector Consumption Reduction Targets Act 129 Phase II																																	0.10%
CumulativeAnnualEnergyEfficiencyGoal | MWh																																	88
Regulatory Assets																											1,574						$ 1,574				1,167
Regulatory Liability, Current																											249						249				329
Regulatory Liability, Noncurrent																											3,735						$ 3,735				$ 3,369
Renewable Energy Resources Cumulatively Increase																																	1.50%
RenewableEnergyRetailLoad																																											50.00%
Other Commitment																											234						$ 234
Revenues																											1,571			1,497			4,227		4,031
Commonwealth Edison Co [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																																	96
Public Utilities, Requested Increase (Decrease), Amount																																	78
Public Utilities, Approved Rate Increase (Decrease), Amount																$ 18					$ 127												$ 18
Public Utilities, Requested Equity Capital Structure, Percentage																																	6.47%
Public Utilities, Requested Rate Increase (Decrease), Percentage																																	8.40%
Public Utilities, Approved Equity Capital Structure, Percentage																																					6.45%
Public Utilities, Approved Rate Increase (Decrease), Percentage																																					8.34%
Commonwealth Edison Co [Member] | Electric Distribution [Member] | 2016 Requirement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount																					134
Commonwealth Edison Co [Member] | Electric Distribution [Member] | 2015 Requirement [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount																					$ 7
Commonwealth Edison Co [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Renewable Energy Resources Cumulatively Increase																																	11.50%
Commonwealth Edison Co [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
ResidentialCustomerRateIncrease | Monetary_per_Decimal																																	0.25
CommercialAndIndustrialCustomerRateIncrease																																	1.30%
Renewable Energy Resources Cumulatively Increase																																	25.00%
Commonwealth Edison Co [Member] | Deferred EE Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											83						$ 83
Commonwealth Edison Co [Member] | Energy Efficiency Program [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											78						78
Commonwealth Edison Co [Member] | Renewable Portfolio Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											7						7
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											159						159				$ 164
Commonwealth Edison Co [Member] | Zero Emission Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											71						71
Commonwealth Edison Co [Member] | Renewable Portfolio Standard [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											46						46
Restricted Cash																											45						45
Regulatory Liability, Current																											10						10
Regulatory Liability, Noncurrent																											20						20
Commonwealth Edison Co [Member] | ACPpayment member [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											38						38
Commonwealth Edison Co [Member] | Over recovered EE Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											(5)						(5)
Commonwealth Edison Co [Member] | EDArefund Member [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											80						80
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											33						33				0
Commonwealth Edison Co [Member] | Subsequent Event [Member]
Regulatory Matters Additional Narrative Information [Line Items]
EnergyEfficiencyAnnualCumulativeSavings		21.50%																																		6.60%
RenewableEnergyRetailLoad																																							100.00%	75.00%
Commonwealth Edison Co [Member] | Subsequent Event [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
FutureEnergyEfficiencySpending																																						$ 250
Commonwealth Edison Co [Member] | Subsequent Event [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
FutureEnergyEfficiencySpending																																						$ 400
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																												$ 22
Public Utilities, Requested Equity Capital Structure, Percentage																												11.00%
Regulatory Liabilities																											719						719				644
Regulatory Assets																											1,809						1,809				1,710
Regulatory Liability, Current																											159						159				127
Regulatory Liability, Noncurrent																											560						560				517
Total Projected Natural Gas LTIIP Spend											$ 762													$ 275
Other Commitment																											240						240
Revenues																											715			788			2,141		2,293
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											40						40				49
PECO Energy Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											29						29				41
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]																																26
Public Utilities, Requested Increase (Decrease), Amount	[1]																																$ 31
Public Utilities, Approved Return on Equity, Percentage	[1],[2]																																10.50%
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[3]																																7.47%
Regulatory Liabilities																											147						$ 147				160
Regulatory Assets																											705						705				712
Regulatory Liability, Current																											63						63				50
Regulatory Liability, Noncurrent																											84						84				110
Estimated number of smart meters to be installed																																												2,000,000
Total smart grid and smart meter investment grant amount																																												$ 480
Reimbursements received from the DOE																																												$ 200
Other Commitment																											13						13
Proposed Capital Expenditure	[1],[4]																																8
Revenues																											738			812			2,363		2,421
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											219						219				230
Amount of Impairment to Carrying Amount of Regulatory Assets																															$ 52
Baltimore Gas and Electric Company [Member] | Unamortized AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											133						133
Baltimore Gas and Electric Company [Member] | Legacy AMI [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											54				56		54
Baltimore Gas and Electric Company [Member] | Recoverable Smart Meter Related Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											32						32
Baltimore Gas and Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											0						0				0
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]																																20
Public Utilities, Requested Increase (Decrease), Amount	[1]																																$ 5
Public Utilities, Approved Return on Equity, Percentage	[1],[2]																																10.50%
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[3]																																7.92%
Regulatory Liabilities																											26						$ 26				31
Regulatory Assets																											880						880				852
Regulatory Liability, Current																											5						5				11
Regulatory Liability, Noncurrent																											21						21				20
Projected Capital Expenditures																											500
Other Commitment																											20						20
Alternative Net Capital Requirement																											250						250
Capital ProjectFundedByBonds																											187.5
CapitalProjectFundedByAgency																											62.5
Revenues																											604			$ 635			1,649		1,695
Potomac Electric Power Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount																			$ 77								67
Public Utilities, Requested Increase (Decrease), Amount															$ 69																$ 86
Public Utilities, Approved Rate Increase (Decrease), Amount									$ 37
Public Utilities, Requested Rate Increase (Decrease), Percentage															10.10%															10.60%
Public Utilities, Approved Rate Increase (Decrease), Percentage									9.50%
TaxAdjustmentIncludedInPublicUtilitiesRequestedRateIncreaseDecreaseAmount															$ 18
Potomac Electric Power Company [Member] | AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											163						163				174
Potomac Electric Power Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											0						0				3
Potomac Electric Power Company [Member] | Subsequent Event [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Approved Rate Increase (Decrease), Amount			$ 32	$ 34
Public Utilities, Approved Rate Increase (Decrease), Percentage				0.00%
Potomac Electric Power Company [Member] | Pepco Holdings [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																											26						26
Potomac Electric Power Company [Member] | Pepco Holdings [Member] | Minimum [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																											6						6
Potomac Electric Power Company [Member] | Pepco Holdings [Member] | Maximum [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Other Commitment																											7						7
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]																																14
Public Utilities, Requested Increase (Decrease), Amount	[1]																																$ 6
Public Utilities, Requested Return on Equity, Percentage								10.10%		10.10%													10.60%
Public Utilities, Approved Return on Equity, Percentage	[1],[2]																																10.50%
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[3]																																7.16%
Regulatory Liabilities																											128						$ 128				140
Regulatory Assets																											369						369				348
Regulatory Liability, Current																											42						42				43
Regulatory Liability, Noncurrent																											86						86				97
Public Utilities, Interim Rate Increase (Decrease), Amount								$ 2.5														$ 2.5
Customer Refund Liability, Noncurrent																																									$ 5
Other Commitment																											11						11
Revenues																											327			$ 331			971		974
Delmarva Power and Light Company [Member] | Gas Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Increase (Decrease), Amount								13															$ 22
Public Utilities, Approved Rate Increase (Decrease), Amount													$ 4.9							$ 10
Public Utilities, Approved Rate Increase (Decrease), Percentage													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					$ 22			31																								$ 32
Public Utilities, Requested Increase (Decrease), Amount								$ 24		$ 27							$ 60						$ 63
Public Utilities, Approved Rate Increase (Decrease), Amount																		$ 38		$ 30									$ 31.5
Public Utilities, Approved Return on Equity, Percentage																		9.60%
Public Utilities, Approved Rate Increase (Decrease), Percentage																													9.70%
Projected Capital Expenditures																		$ 5
Delmarva Power and Light Company [Member] | AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											79						79				84
Delmarva Power and Light Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											0						0				0
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]																																42
Public Utilities, Requested Increase (Decrease), Amount	[1]																																$ 20
Public Utilities, Approved Return on Equity, Percentage	[1],[2]																																10.50%
Public Utilities, Approved Equity Capital Structure, Percentage	[1],[3]																																8.02%
Regulatory Liabilities																											18						$ 18				25
Regulatory Assets																											504						504				501
Regulatory Liability, Current																											18						18				25
Regulatory Liability, Noncurrent																											0						0				0
Projected Capital Expenditures																											79
Other Commitment																											9						9
Proposed Capital Expenditure																			$ 29									$ 32
Revenues																											370			$ 421			915		$ 982
Atlantic City Electric Company [Member] | Electric Distribution [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Increase (Decrease), Amount							$ 43			$ 73				$ 70
Public Utilities, Requested Rate Increase (Decrease), Percentage							9.60%							10.10%
Atlantic City Electric Company [Member] | AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets																											0						0				0
Atlantic City Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities																											$ 0						$ 0				$ 0
[1]	All rates are effective June 2017, subject to review by the FERC and other parties, which is due by fourth quarter 2017.
[2]	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.
[3]	Represents the weighted average debt and equity return on transmission rate bases.
[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 Regulatory M

Regulatory Matters Regulatory Matters - Annual Electric Transmission Fillings (Details) - USD ($) $ in Millions		Sep. 11, 2017	Jun. 09, 2017	Feb. 01, 2017	Jun. 30, 2017	Sep. 30, 2017
Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Initial revenue requirement increase			$ 7			$ 44	[1]
Annual reconciliation (decrease) increase	[1]					(33)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	[1]					$ 11
Public Utilities, Approved Equity Capital Structure, Percentage		6.47%				8.43%	[1],[2]
Public Utilities, Approved Return on Equity, Percentage		8.40%				11.50%	[1],[3]
Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Initial revenue requirement increase	[1]					$ 31
Annual reconciliation (decrease) increase	[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]
Initial revenue requirement increase	[1]					$ 5
Annual reconciliation (decrease) increase	[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]
Initial revenue requirement increase	[1]					$ 6
Annual reconciliation (decrease) increase	[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]
Initial revenue requirement increase	[1]					$ 20
Annual reconciliation (decrease) increase	[1]					22
Proposed Capital Expenditure				$ 29	$ 32
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 Regulatory59

Regulatory Matters Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions		Sep. 30, 2017		Dec. 31, 2016
Regulatory Assets [Line Items]
Regulatory Assets		$ 11,502		$ 11,388
Current		1,264		1,342
Regulatory Assets, Noncurrent		10,238		10,046
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[1]	4,020		4,162
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2,423		2,016
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		660		701
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		256		188
Energy Efficiency Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		78
Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		120		124
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		773		812
Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets		830		1,085
Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2		5
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		108		111
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		300		305
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		70		56
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		277		260
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		65		89
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		31		36
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3		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		599		621
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		47		25
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		72		27
Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6		8
Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		33		34
Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		38		31
Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		93		138
CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9		11
AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		518		477
Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Regulatory Assets		71		49
Under funded Benefit Post Retirement Obligation [Member]
Regulatory Assets [Line Items]
Regulatory Assets		969		995
Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,574		1,167
Current		187		190
Regulatory Assets, Noncurrent		1,387		977
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Commonwealth Edison Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[2]	347		75
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		159		164
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[3]	256		188
Commonwealth Edison Co [Member] | Energy Efficiency Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		78
Commonwealth Edison Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		38		42
Commonwealth Edison Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Commonwealth Edison Co [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Commonwealth Edison Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Commonwealth Edison Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		73		76
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		277		278
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		60		56
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		277		258
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	3		23
Commonwealth Edison Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Commonwealth Edison Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		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
Commonwealth Edison Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets				0
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
Commonwealth Edison Co [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Commonwealth Edison Co [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Commonwealth Edison Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Commonwealth Edison Co [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6		7
Commonwealth Edison Co [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		73		22
Commonwealth Edison Co [Member] | Annual Reconciliations [Member]
Regulatory Assets [Line Items]
Regulatory Assets		200		134
Commonwealth Edison Co [Member] | Recoverable Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		56		54
Commonwealth Edison Co [Member] | Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11		20
Commonwealth Edison Co [Member] | Constellation and PHI Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7		11
Commonwealth Edison Co [Member] | 561710 Exterminating and Pest Control Services [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6
Commonwealth Edison Co [Member] | Advanced Metering Infrastructure Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		32		23
Commonwealth Edison Co [Member] | Constellation Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets				8
Commonwealth Edison Co [Member] | ElectricTransmissionCostsUnderRecovery [Member]
Regulatory Assets [Line Items]
Regulatory Assets				15
PECO Energy Co [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,809		1,710
Current		36		29
Regulatory Assets, Noncurrent		1,773		1,681
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,678		1,583
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		40		49
PECO Energy Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1		1
PECO Energy Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		22		23
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		23		26
PECO Energy Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[5]	0		0
PECO Energy Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0
PECO Energy Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets				0
PECO Energy Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1		1
PECO Energy Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		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
PECO Energy Co [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		14		7
PECO Energy Co [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
PECO Energy Co [Member] | CAP Arrearage [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9		11
PECO Energy Co [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Regulatory Assets		21		9
Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets		705		712
Current		208		208
Regulatory Assets, Noncurrent		497		504
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[2]	100		98
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		219		230
Baltimore Gas and Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Baltimore Gas and Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		12		7
Baltimore Gas and Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		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		2		5
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		13		12
Baltimore Gas and Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		1
Baltimore Gas and Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Baltimore Gas and Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Baltimore Gas and Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[6]	26		38
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		1
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3		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		284		285
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[7]	7		10
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[8]	34		3
Baltimore Gas and Electric Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Baltimore Gas and Electric Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Baltimore Gas and Electric Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Baltimore Gas and Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Baltimore Gas and Electric Company [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5		5
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		42		38
Baltimore Gas and Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5		28
Baltimore Gas and Electric Company [Member] | Under-Recovered Natural Gas Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		14		3
Baltimore Gas and Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3		4
Baltimore Gas and Electric Company [Member] | Abandonment costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4		3
Baltimore Gas and Electric Company [Member] | PHI Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5		6
Baltimore Gas and Electric Company [Member] | Under-Recovered Electric Revenue Decoupling [Member]
Regulatory Assets [Line Items]
Regulatory Assets		24		1
Baltimore Gas and Electric Company [Member] | UnderRecoveredNaturalGasDecouplingRevenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10		2
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3,260		3,504
Current		568		653
Regulatory Assets, Noncurrent		2,692		2,851
Pepco Holdings LLC [Member] | Other Postretirement Benefits [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Pepco Holdings LLC [Member] | Deferred Income Tax Charge [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		298		260
Pepco Holdings LLC [Member] | AMI Expenses [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		242		258
Pepco Holdings LLC [Member] | Under Recovered Distribution Service Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Pepco Holdings LLC [Member] | Loss on Reacquired Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		75		81
Pepco Holdings LLC [Member] | Fair Value Of Long Term Debt [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		632		671
Pepco Holdings LLC [Member] | Fair Value Of Supply Contract [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		830		1,085
Pepco Holdings LLC [Member] | Employee Severance [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Pepco Holdings LLC [Member] | Asset Retirement Obligation Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Pepco Holdings LLC [Member] | Environmental Restoration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Pepco Holdings LLC [Member] | Under Recovered Uncollectible Accounts Expense [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10		0
Pepco Holdings LLC [Member] | Renewable Energy And Associated REC [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		2
Pepco Holdings LLC [Member] | Under Recovered Energy And Transmission Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		36		28
Pepco Holdings LLC [Member] | Deferred Storm Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		31		35
Pepco Holdings LLC [Member] | Electric Generation Related Regulatory Asset [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Pepco Holdings LLC [Member] | Rate Stabilization Deferral [Member] | 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		314		335
Pepco Holdings LLC [Member] | Merger Integration Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		40		15
Pepco Holdings LLC [Member] | Under Recovered Decoupling Revenue [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		38		24
Pepco Holdings LLC [Member] | Deferred Project Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6		8
Pepco Holdings LLC [Member] | Workers Compensation and Long-Term Disability [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		33		34
Pepco Holdings LLC [Member] | Recoverable Vacation Pay [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		24		24
Pepco Holdings LLC [Member] | Stranded Costs [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		93		138
Pepco Holdings LLC [Member] | AssetRemovalCosts [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		518		477
Pepco Holdings LLC [Member] | Other Regulatory Assets (Liabilities) [Member] | Successor [Member]
Regulatory Assets [Line Items]
Regulatory Assets		40		29
Potomac Electric Power Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets		880		852
Current		181		162
Regulatory Assets, Noncurrent		699		690
Potomac Electric Power Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Potomac Electric Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[2]	195		171
Potomac Electric Power Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		163		174
Potomac Electric Power Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Potomac Electric Power Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		16		17
Potomac Electric Power Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		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
Potomac Electric Power Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Potomac Electric Power Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Potomac Electric Power Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Potomac Electric Power Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Potomac Electric Power Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[9]	6		6
Potomac Electric Power Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9		12
Potomac Electric Power Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		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		233		250
Potomac Electric Power Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[10]	20		11
Potomac Electric Power Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		33		21
Potomac Electric Power Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Potomac Electric Power Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		33		34
Potomac Electric Power Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Potomac Electric Power Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Potomac Electric Power Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		144		134
Potomac Electric Power Company [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Regulatory Assets		28		22
Potomac Electric Power Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34		31
Potomac Electric Power Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3		6
Potomac Electric Power Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3
Potomac Electric Power Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[10]	11
Potomac Electric Power Company [Member] | MergerIntegrationCostsToBeRecoveredInDCServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[10]	9
Delmarva Power and Light Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets		369		348
Current		69		59
Regulatory Assets, Noncurrent		300		289
Delmarva Power and Light Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Delmarva Power and Light Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[2]	45		38
Delmarva Power and Light Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		79		84
Delmarva Power and Light Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Delmarva Power and Light Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8		9
Delmarva Power and Light Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		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
Delmarva Power and Light Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Delmarva Power and Light Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Delmarva Power and Light Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Delmarva Power and Light Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Delmarva Power and Light Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[11]	9		5
Delmarva Power and Light Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5		5
Delmarva Power and Light Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		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		81		85
Delmarva Power and Light Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[10]	11		4
Delmarva Power and Light Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5		3
Delmarva Power and Light Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6		8
Delmarva Power and Light Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Delmarva Power and Light Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		14		14
Delmarva Power and Light Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Delmarva Power and Light Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		98		88
Delmarva Power and Light Company [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8		5
Delmarva Power and Light Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		23		20
Delmarva Power and Light Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5		4
Delmarva Power and Light Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4		1
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInMarylandServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4
Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInDelawareServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5
Atlantic City Electric Company [Member]
Regulatory Assets [Line Items]
Regulatory Assets		504		501
Current		87		96
Regulatory Assets, Noncurrent		417		405
Atlantic City Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[2]	58		51
Atlantic City Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5		6
Atlantic City Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Fair Value Of Supply Contract [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10		0
Atlantic City Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		2
Atlantic City Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[12]	21	[11]	17
Atlantic City Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		17		18
Atlantic City Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0
Atlantic City Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets				0
Atlantic City Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9		0
Atlantic City Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Deferred Project Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Workers Compensation and Long-Term Disability [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0		0
Atlantic City Electric Company [Member] | Recoverable Vacation Pay [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10		10
Atlantic City Electric Company [Member] | Stranded Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		93		138
Atlantic City Electric Company [Member] | AssetRemovalCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		277		255
Atlantic City Electric Company [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4		4
Atlantic City Electric Company [Member] | Deferred Income Tax Transmission Related [Member]
Regulatory Assets [Line Items]
Regulatory Assets		21		19
Atlantic City Electric Company [Member] | UnderRecoveredElectricEnergyCosts [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10		11
Atlantic City Electric Company [Member] | TransmissionCost [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11		$ 6
Electric Distribution [Member] | Delmarva Power and Light Company [Member] | MergerIntegrationCostsToBeRecoveredInDelawareServiceTerritory [Member]
Regulatory Assets [Line Items]
Regulatory Assets		$ 2
[1]	As of September 30, 2017 and December 31, 2016, the pension and other postretirement benefits regulatory asset at Exelon includes regulatory assets of $969 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.
[2]	As of September 30, 2017, includes transmission-related income tax regulatory assets that require FERC approval separate from the transmission formula rate of $73 million, $42 million, $34 million, $23 million and $21 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.
[3]	As of September 30, 2017, ComEd’s regulatory asset of $256 million was comprised of $200 million for the 2015 - 2017 annual reconciliations and $56 million related to significant one-time events including $11 million of deferred storm costs, $7 million of Constellation and PHI merger and integration related costs, $6 million of emerald ash borer costs, and $32 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— Mergers, Acquisitions and Dispositions of the Exelon 2016 Form 10-K for further information.
[4]	As of September 30, 2017, ComEd’s regulatory liability of $54 million included $22 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.
[5]	As of September 30, 2017, PECO's regulatory liability of $68 million included $34 million related to over-recovered costs under the DSP program, $21 million related to the over-recovered natural gas costs under the PGC and $13 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.
[6]	As of September 30, 2017, BGE's regulatory asset of $26 million included $5 million related to under-recovered electric energy costs, $14 million related to under-recovered natural gas costs, $3 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $4 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.
[7]	As of September 30, 2017 and December 31, 2016, BGE's regulatory asset of $7 million and $10 million, respectively, included $5 million and $6 million, respectively, of previously incurred PHI acquisition costs as authorized by the June 2016 rate case order.
[8]	Represents the electric and natural gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of September 30, 2017, BGE had a regulatory asset of $24 million related to under-recovered electric revenue decoupling and $10 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.
[9]	As of September 30, 2017, Pepco's regulatory asset of $6 million included $3 million of transmission costs recoverable through its FERC approved formula rate and $3 million of under-recovered electric energy costs. As of September 30, 2017, Pepco's regulatory liability of $3 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.
[10]	As of September 30, 2017, Pepco’s regulatory asset of $20 million represents previously incurred PHI acquisition costs, including $11 million authorized for recovery in Maryland and $9 million expected to be recovered in the District of Columbia service territory. As of December 31, 2016, Pepco's regulatory asset of $11 million represents previously incurred PHI acquisition costs authorized for recovery in Maryland. (l)As of September 30, 2017, DPL’s regulatory asset of $11 million represents previously incurred PHI acquisition costs, including $4 million authorized for recovery in Maryland, $5 million authorized for recovery in Delaware electric rates, and $2 million expected to be recovered in electric and gas 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 the Maryland service territory.
[11]	As of September 30, 2017, DPL's regulatory asset of $9 million included $4 million of transmission costs recoverable through its FERC approved formula rate and $5 million related to under-recovered electric energy costs. As of September 30, 2017, DPL's regulatory liability of $9 million related to over-recovered electric energy costs. 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.
[12]	As of September 30, 2017, ACE's regulatory asset of $21 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $10 million of under-recovered electric energy costs. As of September 30, 2017, ACE's regulatory liability of $5 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 - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions		Sep. 30, 2017		Dec. 31, 2016
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 5,102		$ 4,789
Regulatory Liability, Current		553		602
Regulatory Liability, Noncurrent		4,549		4,187
Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		41		47
Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,971		2,607
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,588		1,601
Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		37		39
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		62		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		50		76
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		14		20
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		139		134
Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		71
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		75		72
Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		46
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3,984		3,698
Regulatory Liability, Current		249		329
Regulatory Liability, Noncurrent		3,735		3,369
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		2,438		2,169
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,337		1,324
Commonwealth Edison Co [Member] | Deferred Lease Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				141
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		33		0
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		54	[1]	60
Commonwealth Edison Co [Member] | Zero Emission Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		71
Commonwealth Edison Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		5		4
Commonwealth Edison Co [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		22		30
Commonwealth Edison Co [Member] | Renewable energy Requirements [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		32		30
Commonwealth Edison Co [Member] | Renewable Portfolio Standard [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		46
Regulatory Liability, Current		10
Regulatory Liability, Noncurrent		20
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		719		644
Regulatory Liability, Current		159		127
Regulatory Liability, Noncurrent		560		517
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		533		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		29		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		50		76
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		14		20
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2]	68		56
PECO Energy Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		17		5
PECO Energy Co [Member] | Default Service Provider Program [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		34		34
PECO Energy Co [Member] | Over Recovered NonBypassable Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		13		10
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		21		8
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		147		160
Regulatory Liability, Current		63		50
Regulatory Liability, Noncurrent		84		110
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		119		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	[3]	0		0
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		28		19
Pepco Holdings LLC [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		211		237
Regulatory Liability, Current		65		79
Regulatory Liability, Noncurrent		146		158
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		132		136
Pepco Holdings LLC [Member] | Deferred Lease Revenue [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		37		39
Pepco Holdings LLC [Member] | Energy Efficiency Demand Response Programs [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		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		17		18
Pepco Holdings LLC [Member] | Regulatory Liabilities Other [Member] | Successor [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		25		41
Potomac Electric Power Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		26		31
Regulatory Liability, Current		5		11
Regulatory Liability, Noncurrent		21		20
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		22		18
Potomac Electric Power Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		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]	3		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 Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3		3
Potomac Electric Power Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				5
Delmarva Power and Light Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		128		140
Regulatory Liability, Current		42		43
Regulatory Liability, Noncurrent		86		97
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		110		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]	9		5
Delmarva Power and Light Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		9		17
Delmarva Power and Light Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				2
Delmarva Power and Light Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				3
Atlantic City Electric Company [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		18		25
Regulatory Liability, Current		18		25
Regulatory Liability, Noncurrent		0		0
Atlantic City Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Atlantic City Electric Company [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Atlantic City Electric Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Atlantic City Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Atlantic City Electric Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Atlantic City Electric Company [Member] | 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]	5		5
Atlantic City Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		13		20
Atlantic City Electric Company [Member] | Over Recovered Electric Supply Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		$ 5		1
Atlantic City Electric Company [Member] | Over Recovered Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				$ 4
[1]	As of September 30, 2017, ComEd’s regulatory liability of $54 million included $22 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 September 30, 2017, PECO's regulatory liability of $68 million included $34 million related to over-recovered costs under the DSP program, $21 million related to the over-recovered natural gas costs under the PGC and $13 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 September 30, 2017, BGE's regulatory asset of $26 million included $5 million related to under-recovered electric energy costs, $14 million related to under-recovered natural gas costs, $3 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $4 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 September 30, 2017, Pepco's regulatory asset of $6 million included $3 million of transmission costs recoverable through its FERC approved formula rate and $3 million of under-recovered electric energy costs. As of September 30, 2017, Pepco's regulatory liability of $3 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 September 30, 2017, DPL's regulatory asset of $9 million included $4 million of transmission costs recoverable through its FERC approved formula rate and $5 million related to under-recovered electric energy costs. As of September 30, 2017, DPL's regulatory liability of $9 million related to over-recovered electric energy costs. 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 September 30, 2017, ACE's regulatory asset of $21 million included $11 million of transmission costs recoverable through its FERC approved formula rate and $10 million of under-recovered electric energy costs. As of September 30, 2017, ACE's regulatory liability of $5 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 Regulatory61

Regulatory Matters Regulatory Matters - Capitalized Ratemaking Amount Not Recognized (Details) - USD ($) $ in Millions		Sep. 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]	7	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]	54	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 primarily 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.

Regulatory Matters Regulatory62

Regulatory Matters Regulatory Matters - Purchase of Receivables Programs (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2017	Dec. 31, 2016
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 312	$ 313
Allowance for Doubtful Accounts Receivable		(33)	(37)
Payments to Acquire Other Receivables, Net		279	276
Commonwealth Edison Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		89	87
Allowance for Doubtful Accounts Receivable	[1]	(13)	(14)
Payments to Acquire Other Receivables, Net		76	73
PECO Energy Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		68	72
Allowance for Doubtful Accounts Receivable		(5)	(6)
Payments to Acquire Other Receivables, Net		63	66
Baltimore Gas and Electric Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		55	59
Allowance for Doubtful Accounts Receivable	[1]	(4)	(4)
Payments to Acquire Other Receivables, Net		51	55
Pepco Holdings LLC [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		100	95
Allowance for Doubtful Accounts Receivable		(11)	(13)
Payments to Acquire Other Receivables, Net		89	82
Potomac Electric Power Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables	[2]	66	63
Allowance for Doubtful Accounts Receivable	[1]	(6)	(7)
Payments to Acquire Other Receivables, Net		60	56
Delmarva Power and Light Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables	[2]	10	10
Allowance for Doubtful Accounts Receivable	[1]	(1)	(2)
Payments to Acquire Other Receivables, Net		9	8
Atlantic City Electric Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		24	22
Allowance for Doubtful Accounts Receivable		(4)	(4)
Payments to Acquire Other Receivables, Net		$ 20	$ 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]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmUzNjkxMjYwMmM4YzRlZjhhNTYwMTZiMDZhYWU5YWI0fFRleHRTZWxlY3Rpb246NjNBREVCNTI0NzdGNThBMkI3N0RCQkUxQUM4MUIxRTcM}

Impairment of Long-Lived Asse63

Impairment of Long-Lived Assets (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Property, plant and equipment, net	$ 73,067				$ 73,067		$ 71,555
Proceeds from Long-term Capital Lease Obligations			$ 360
Capital Leases, Net Investment in Direct Financing Leases, Unguaranteed Residual Values of Leased Property			356
Gain (Loss) on Contract Termination		$ 36	4
Impairment of long-lived assets and losses on regulatory assets					488	$ 274
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
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	$ 40

Early Nuclear Plant Retiremen64

Early Nuclear Plant Retirements Early Nuclear Plant Retirements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2017	Dec. 31, 2016
Facility Closing [Member] | Three Mile Island [Member]
Property, Plant and Equipment [Line Items]
Restructuring Reserve, Accrual Adjustment					$ 76
Restructuring and Related Cost, Incurred Cost	$ 112				$ 149
Facility Closing [Member] | Clinton and Quad Cities [Member]
Property, Plant and Equipment [Line Items]
Restructuring and Related Cost, Incurred Cost		$ 125	$ 338	$ 251		$ 714
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%				42.59%

Early Nuclear Plant Retiremen65

Early Nuclear Plant Retirements Early Nuclear Plant Retirement - Pretax Expense (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended		12 Months Ended
		Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Other, net		$ 237		$ 120		$ 725	$ 377
Facility Closing [Member] | Three Mile Island [Member]
Restructuring and Related Cost, Accelerated Depreciation	[1]	106				141
Nuclear Fuel Amortization		6				8
Restructuring and Related Cost, Incurred Cost		$ 112				$ 149
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)
Restructuring and Related Cost, Incurred Cost			$ 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 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.

Intangibles Intangibles - Narra

Intangibles Intangibles - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2017	Sep. 30, 2015
Finite-Lived Intangible Assets, Gross [Abstract]
Finite-Lived Intangible Assets, Gross	$ 25	$ 25

Fair Value of Financial Asset67

Fair Value of Financial Assets and Liabilities - Fair Value of Financial Liabilities Recorded at the Carrying Amount (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Due to Related Parties, Noncurrent		$ 389	$ 641
Spent Nuclear Fuel Obligation, Noncurrent		1,142	1,024
Deferred Finance Costs, Net		196	200
Financing Trusts [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		1	7
Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		710	1,267
Long-term debt (including amounts due within one year)(a)	[1]	34,865	34,005
Due to Related Parties, Noncurrent	[2]	389	641
Spent Nuclear Fuel Obligation, Noncurrent		1,142	1,024
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value		710	1,267
Long-term debt (including amounts due within one year)(a)	[1]	36,635	34,813
Due to Related Parties, Noncurrent	[2]	423	667
Spent Nuclear Fuel Obligation, Noncurrent		857	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		710	1,267
Long-term debt (including amounts due within one year)(a)	[1]	34,686	31,741
Due to Related Parties, Noncurrent	[2]	0	0
Spent Nuclear Fuel Obligation, Noncurrent		857	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]	1,949	1,959
Due to Related Parties, Noncurrent	[2]	423	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		1,142	1,024
Deferred Finance Costs, Net		51	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		92	699
Long-term debt (including amounts due within one year)(a)	[1]	9,528	9,241
Spent Nuclear Fuel Obligation, Noncurrent		1,142	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		92	699
Long-term debt (including amounts due within one year)(a)	[1]	9,567	9,152
Spent Nuclear Fuel Obligation, Noncurrent		857	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		92	699
Long-term debt (including amounts due within one year)(a)	[1]	7,915	7,482
Spent Nuclear Fuel Obligation, Noncurrent		857	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]	1,652	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		53	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]
Long-term debt (including amounts due within one year)(a)	[1]	7,600	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]
Long-term debt (including amounts due within one year)(a)	[1]	8,353	7,585
Due to Related Parties, Noncurrent	[2]	226	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]
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]
Long-term debt (including amounts due within one year)(a)	[1]	8,353	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]
Long-term debt (including amounts due within one year)(a)	[1]	0	0
Due to Related Parties, Noncurrent	[2]	226	215
PECO Energy Co [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Due to Related Parties, Noncurrent		184	184
Deferred Finance Costs, Net		17	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]	2,902	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]	3,181	2,794
Due to Related Parties, Noncurrent		197	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]	3,181	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		197	192
Baltimore Gas and Electric Company [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Due to Related Parties, Noncurrent		0	252
Deferred Finance Costs, Net		17	15
Baltimore Gas and Electric Company [Member] | Financing Trusts [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net			6
Baltimore Gas and Electric Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt, Fair Value			45
Long-term debt (including amounts due within one year)(a)	[1]	2,577	2,322
Due to Related Parties, Noncurrent	[2]		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			45
Long-term debt (including amounts due within one year)(a)	[1]	2,817	2,467
Due to Related Parties, Noncurrent	[2]		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
Long-term debt (including amounts due within one year)(a)	[1]	0	0
Due to Related Parties, Noncurrent	[2]		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			45
Long-term debt (including amounts due within one year)(a)	[1]	2,817	2,467
Due to Related Parties, Noncurrent	[2]		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
Long-term debt (including amounts due within one year)(a)	[1]	0	0
Due to Related Parties, Noncurrent	[2]		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		118	522
Long-term debt (including amounts due within one year)(a)	[1]	5,930	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		118	522
Long-term debt (including amounts due within one year)(a)	[1]	6,026	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		118	522
Long-term debt (including amounts due within one year)(a)	[1]	5,729	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]	297	289
Potomac Electric Power Company [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Deferred Finance Costs, Net		32	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]	2,546	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]	3,096	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]	3,087	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		54
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		54
Long-term debt (including amounts due within one year)(a)	[1]	1,407	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		54
Long-term debt (including amounts due within one year)(a)	[1]	1,407	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		65
Long-term debt (including amounts due within one year)(a)	[1]	1,130	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		65
Long-term debt (including amounts due within one year)(a)	[1]	1,257	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		65
Long-term debt (including amounts due within one year)(a)	[1]	969	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]	$ 288	$ 280
[1]	Includes unamortized debt issuance costs which are not fair valued of $196 million, $51 million, $53 million, $17 million, $17 million, $6 million, $32 million, $11 million, and $5 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of September 30, 2017. Includes unamortized debt issuance costs which are not fair valued of $200 million, $64 million, $46 million, $15 million, $15 million, $2 million, $30 million, $11 million, and $6 million for Exelon, Generation, ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, as of December 31, 2016.
[2]	Includes unamortized debt issuance costs which are not fair valued of $1 million and $1 million for Exelon and ComEd, respectively, as of September 30, 2017. Includes unamortized debt issuance costs which are not fair valued of $7 million, $1 million, and $6 million for Exelon, ComEd and BGE, respectively, as of December 31, 2016.

Fair Value of Financial Asset68

Fair Value of Financial Assets and Liabilities - Fair Value Measurements of Assets and Liabilities, Recurring and Nonrecurring (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)		$ 178	$ 282
Derivative Liability, Noncurrent		410	392
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative, Collateral, Right to Reclaim Cash		75	29
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		0	(2)
Derivative Asset, Notional Amount		885	933
Margin Deposit Assets		27	(158)
Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		382	360
Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		219	180
Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		22	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		52	31
Pledged Assets For Zion Station Decommissioning [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments		0	0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	[1]	944	373
FinancialAssetsFairValueDisclosure1		15,422	13,253
Deferred Compensation Liability, Current and Noncurrent		(137)	(136)
Financial Liabilities Fair Value Disclosure		(725)	(810)
FinancialAssetLiabilitiesNetFairValueDisclosure1		14,697	12,443
Alternative Investment, Fair Value Disclosure		3,370	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		(579)	(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		(4,087)	(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		(73)	(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]	3,581	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		(9)	(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		(19)	(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)
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	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]	13,018	11,092
Alternative Investment, Fair Value Disclosure	[4]	3,345	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]	235	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		6,863	6,014
Alternative Investment, Fair Value Disclosure		2,088	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		4,756	3,977
Alternative Investment, Fair Value Disclosure		509	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		1,906	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		1,979	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		70	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		246	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]	555	552
Alternative Investment, Fair Value Disclosure	[6]	509	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		503	498
Alternative Investment, Fair Value Disclosure		87	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		212	148
Alternative Investment, Fair Value Disclosure		212	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		449	326
Alternative Investment, Fair Value Disclosure		449	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]	57	113
Alternative Investment, Fair Value Disclosure	[7]	25	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		15	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		42	83
Alternative Investment, Fair Value Disclosure		25	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		235	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		77	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		56	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		89	84
Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		4,191	5,092
Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		85	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]	(3,166)	(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		1,110	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		15	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		10	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		16	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			5
Fair Value, Measurements, Recurring [Member] | Effectsofnettingandallocationofcollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset		(11)	(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		43	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		59	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]	944	373
FinancialAssetsFairValueDisclosure1		7,115	5,674
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(2)	(37)
FinancialAssetLiabilitiesNetFairValueDisclosure1		7,113	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		(2)	(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		(559)	(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		(3)	(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]	560	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		0	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		(2)	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)
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		2	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]	6,035	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]	149	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		3,935	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		1,951	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		1,951	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]	15	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		15	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		133	124
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		77	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		56	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		487	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		2	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]	(501)	(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		(12)	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		3	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
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		215	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		3,352	2,937
Deferred Compensation Liability, Current and Noncurrent		(137)	(136)
Financial Liabilities Fair Value Disclosure		(208)	(237)
FinancialAssetLiabilitiesNetFairValueDisclosure1		3,144	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		(62)	(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		(2,062)	(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		(43)	(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]	2,043	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		(9)	(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		(17)	(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
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		8	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]	2,967	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]	86	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		840	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		2,041	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		1,651	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		28	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		70	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		246	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		81	80
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | 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		68	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		2,076	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		41	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]	(1,828)	(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		289	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		15	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		10	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		13	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			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		(8)	(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		141	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		1,585	1,529
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(515)	(536)
FinancialAssetLiabilitiesNetFairValueDisclosure1		1,070	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		(515)	(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		(1,466)	(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		(27)	(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]	978	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
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]	671	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		416	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]	17	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		17	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		1,628	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		42	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]	(837)	(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		833	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
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		43	42
Exelon Generation Co L L C [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)		158	263
Derivative Liability, Noncurrent		153	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		282	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		184	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]	80	39
FinancialAssetsFairValueDisclosure1		14,361	12,718
Deferred Compensation Liability, Current and Noncurrent		(35)	(34)
Financial Liabilities Fair Value Disclosure		(346)	(450)
FinancialAssetLiabilitiesNetFairValueDisclosure1		14,015	12,268
Alternative Investment, Fair Value Disclosure		3,370	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		(302)	(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		(3,810)	(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		(73)	(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]	3,581	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		(9)	(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		(19)	(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)
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		10	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]	13,018	11,092
Alternative Investment, Fair Value Disclosure	[4]	3,345	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]	235	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		6,863	6,014
Alternative Investment, Fair Value Disclosure		2,088	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		4,756	3,977
Alternative Investment, Fair Value Disclosure		509	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		1,906	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		1,979	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		70	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		246	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]	555	552
Alternative Investment, Fair Value Disclosure	[6]	509	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		503	498
Alternative Investment, Fair Value Disclosure		87	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		212	148
Alternative Investment, Fair Value Disclosure		212	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		449	326
Alternative Investment, Fair Value Disclosure		449	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]	57	113
Alternative Investment, Fair Value Disclosure	[7]	25	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		15	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		42	83
Alternative Investment, Fair Value Disclosure		25	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		48	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		21	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		4,191	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		85	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]	(3,166)	(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		1,110	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		5	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		16	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			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		(11)	(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		43	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]	80	39
FinancialAssetsFairValueDisclosure1		6,145	5,237
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(2)	(37)
FinancialAssetLiabilitiesNetFairValueDisclosure1		6,143	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		(2)	(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		(559)	(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		(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 Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	[2],[3]	560	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		0	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		(2)	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)
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		2	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]	6,035	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]	149	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		3,935	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		1,951	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		1,951	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]	15	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		15	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		487	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		2	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]	(501)	(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		(12)	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		3	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
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		3,282	2,859
Deferred Compensation Liability, Current and Noncurrent		(35)	(34)
Financial Liabilities Fair Value Disclosure		(106)	(135)
FinancialAssetLiabilitiesNetFairValueDisclosure1		3,176	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		(62)	(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		(2,062)	(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		(43)	(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]	2,043	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		(9)	(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		(17)	(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
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		8	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]	2,967	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]	86	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		840	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		2,041	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		1,651	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		28	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		70	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		246	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		21	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		21	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		2,076	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		41	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]	(1,828)	(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		289	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		5	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		13	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			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		(8)	(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		1,564	1,509
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(238)	(278)
FinancialAssetLiabilitiesNetFairValueDisclosure1		1,326	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		(238)	(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		(1,189)	(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		(27)	(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]	978	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
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]	671	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		416	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]	17	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		17	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		1,628	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		42	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]	(837)	(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		833	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
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		43	42
Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)		20	19
Derivative Liability, Noncurrent		257	239
Commonwealth Edison Co [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents		36	36
Commonwealth Edison Co [Member] | Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			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]	273	20
FinancialAssetsFairValueDisclosure1		273	20
Total mark-to-market derivative liabilities	[9]	(277)	(258)
Deferred Compensation Liability, Current and Noncurrent		(7)	(8)
Financial Liabilities Fair Value Disclosure		(284)	(266)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(11)	(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]	273	20
FinancialAssetsFairValueDisclosure1		273	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		273	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]	(277)	(258)
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		(277)	(258)
FinancialAssetLiabilitiesNetFairValueDisclosure1		(277)	(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		20	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]	314	45
FinancialAssetsFairValueDisclosure1		331	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		321	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]	314	45
FinancialAssetsFairValueDisclosure1		321	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		321	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		11	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		1
Baltimore Gas and Electric Company [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents			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]	18	36
FinancialAssetsFairValueDisclosure1		23	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		19	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]	18	36
FinancialAssetsFairValueDisclosure1		23	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		23	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
Mark-to-market derivative liabilities (current liabilities)		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		18	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]	184	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		313	348
Deferred Compensation Liability, Current and Noncurrent		(24)	(28)
Financial Liabilities Fair Value Disclosure		(24)	(28)
FinancialAssetLiabilitiesNetFairValueDisclosure1		289	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		129	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		72	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]	184	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		256	290
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		256	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		72	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		72	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		7	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		3	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
Derivative Asset	[11]		2
Collateral Amount Offset Against Fair Value Of Derivative Current Asset			(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		5	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]	31	130
FinancialAssetsFairValueDisclosure1		31	130
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		31	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]	31	130
Investments, Fair Value Disclosure		0	0
FinancialAssetsFairValueDisclosure1		31	130
Deferred Compensation Liability, Current and Noncurrent		0	0
Financial Liabilities Fair Value Disclosure		0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1		31	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 $282 million and $252 million at September 30, 2017 and December 31, 2016 and restricted cash of $184 million and $157 million at September 30, 2017 and December 31, 2016. Exelon excludes cash of $382 million and $360 million at September 30, 2017 and December 31, 2016 and restricted cash of $219 million and $180 million at September 30, 2017 and December 31, 2016 and includes long-term restricted cash of $22 million and $25 million at September 30, 2017 and December 31, 2016, which is reported in other deferred debits on the balance sheet.
[2]	Collateral posted/(received) from counterparties totaled $59 million, $215 million and $141 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of September 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), $27 million represents variation margin on the exchanges as of September 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 $52 million and $31 million at September 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 $75 million and $29 million of cash received from outstanding repurchase agreements at September 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 less than $1 million and $(2) million, which have a total notional amount of $885 million and $933 million at September 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 September 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 $36 million at September 30, 2017 and December 31, 2016 and restricted cash of $2 million at December 31, 2016. PECO excludes cash of $20 million and $22 million at September 30, 2017 and December 31, 2016. BGE excludes cash of $11 million and $13 million at September 30, 2017 and December 31, 2016 and restricted cash of $1 million at September 30, 2017 and includes long-term restricted cash of $2 million at 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 $20 million and $257 million, respectively, at September 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 $18 million and $19 million at September 30, 2017 and December 31, 2016 and includes long-term restricted cash of $22 million and $23 million at September 30, 2017 and December 31, 2016 which is reported in other deferred debits on the balance sheet. Pepco excludes cash of $7 million and $9 million at September 30, 2017 and December 31, 2016. DPL excludes cash of $3 million and $4 million at September 30, 2017 and December 31, 2016. ACE excludes cash of $5 million and $3 million at September 30, 2017 and December 31, 2016 and includes long-term restricted cash of $22 million and $23 million at September 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 Asset69

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		9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016		Mar. 23, 2016		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016		Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 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		$ 1,070		$ 1,466		$ 20		$ 1,466		$ 1,070		$ 1,466		$ 1,098	$ 993	$ 1,185	$ 1,529
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(80)		93						(102)		(334)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates				0						0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		(4)		(1)						(3)		1
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets		(21)		(17)						(6)		21
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		11		31						81		(51)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		77		214						205		420
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				(7)						(15)		(11)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0						(1)		(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(21)		(28)						(85)		(119)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3				0						(9)		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		10		(4)						12		(11)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		26		288						167		248
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				(6)						(13)		(18)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets		0		6						13		18
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		(96)		(190)						(279)		(579)
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		1,326		1,689				1,689		1,326		1,689		1,334	1,231	1,386	1,776
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(81)		92						(104)		(336)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates				6						13		18
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		(4)		(1)						(3)		1
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		11		31						81		(51)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		77		214						205		420
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				(7)						(15)		(11)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(21)		(28)						(85)		(119)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3				0						(9)		2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		10		(4)						12		(11)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		25		288						165		247
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		671		693				693		671		693		683	677	715	670
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0		(4)						4		2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates				6						13		18
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0		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		4						54		123
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				0						0		(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		(31)		(28)						(77)		(119)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3				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		7
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		17		19				19		17		19		21	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
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		(4)		(1)						(3)		1
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				(5)						0		(5)
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
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		595		935				935		595		935		589	493	609	1,051
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		(82)	[1]	95	[2]					(110)	[1]	(339)	[2]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates				0						0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0		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		11		31						81		(51)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		57		207	[3]					146		289	[3]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				(2)						(15)		(5)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		10	[4]	0						(8)	[4]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3				(1)						(9)		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		10		(4)						17		(11)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		24		285						161		240
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Indefinite-lived Intangible Assets Acquired												168
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		43		42				42		43		42		41	42	37	33
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1		1						2		1
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates				0						0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0		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		3						4		7
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				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				1						0		1
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)		1		0						2		0
Commonwealth Edison Co [Member] | Derivative [Member] | Interest Rate Swap [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Realized Investment Gains (Losses)		3		2						13		13
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		(277)		(244)				(244)		(277)		(244)		(256)	(258)	(221)	(247)
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
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0		0						0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets		(21)	[5]	(23)	[6]					(19)	[5]	3	[6]
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						0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				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
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
Purchases, sales, issuances and settlements
Ending balance				(244)				(244)				(244)
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)		(24)		(25)						(32)		(10)
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	[7]					20
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable				0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member] | Successor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		21		21	[7]	0	[7]	21	[7]	21		21	[7]	20	20	20
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1		1				2	[7]	2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates				0				0	[7]	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0						0	[7]	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Regulatory assets		0		0				0	[7]	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		0		0				0	[7]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0		0				0	[7]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				0				0	[7]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances				0				(1)	[7]	(1)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0		0				0	[7]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3				0				0	[7]	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		0		0				0	[7]	0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		1		0				1	[7]	2
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		21		21				$ 21		21		21		$ 20	$ 20	$ 20	$ 19
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		1		1						2		3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances		0		0						(1)		(1)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		$ 1		$ 0						$ 2		$ 2
[1]	Includes a reduction for the reclassification of $96 million and $279 million of realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2017.
[2]	Includes a reduction for the reclassification of $190 million and $579 million of realized gains due to the settlement of derivative contracts recorded in results of operations for the three and nine months ended September 30, 2016.
[3]	Includes $168 million of fair value from contracts acquired as a result of portfolio acquisitions.
[4]	Exelon includes the settlement value for any open contracts that were net settled prior to their scheduled maturity within this line item.
[5]	Includes $24 million of decreases in fair value and an increase for realized losses due to settlements of $3 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2017. Includes $32 million of decreases in fair value and an increase for realized losses due to settlements of $13 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2017.
[6]	Includes $25 million of decreases in fair value and an increase for realized losses due to settlements of $2 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2016. Includes $10 million of decreases in fair value and an increase for realized losses due to settlements of $13 million for the nine months ended September 30, 2016.
[7]	Successor period represents activity from March 24, 2016 through September 30, 2016. See tables below for PHI's predecessor periods, as well as activity for Pepco for the three and nine months ended September 30, 2017 and 2016.

Fair Value of Financial Asset70

Fair Value of Financial Assets and Liabilities Fair Value of Financial Assets and Liabilities - Narrative (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Spent Nuclear Fuel Obligation, Noncurrent	$ 1,142,000,000	$ 1,024,000,000
Forward Power Basis	2.93
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	1,142,000,000	$ 1,024,000,000
Fixed Income Securities [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	75,000,000
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	285,000,000
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	240,000,000
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	95,000,000
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	$ 112,000,000

Fair Value of Financial Asset71

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		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Mar. 23, 2016	Sep. 30, 2016	[2]	Sep. 30, 2017	Sep. 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		$ 80	$ (93)				$ 102	$ 334
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		26	288				167	248
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		(3)	180				34	(232)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		47	323				222	303
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		(69)	(85)				(152)	(107)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(23)	(38)				(61)	(63)
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]	2	(3)				8	4
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[1]	2	3				6	8
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		81	(92)				104	336
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		25	288				165	247
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		(3)	180				34	(232)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		47	323				222	303
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		(69)	(85)				(152)	(107)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		(23)	(38)				(61)	(63)
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)				6	2
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[1]	1	3				4	7
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]	1	1				2	2
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[1]	1	0				2	1
Pepco Holdings LLC [Member] | Other, net [Member] | Predecessor [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	[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]	1	1				2	3
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	[1]	1	0				2	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		(1)	(1)		$ (2)		(2)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		1	0		$ 1		2
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		(1)	(1)				(2)	(3)
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)		$ 1	$ 0				$ 2	$ 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 September 30, 2016. See tables below for PHI's predecessor periods, as well as activity for Pepco for the three and nine months ended September 30, 2017 and 2016.

Fair Value of Financial Asset72

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 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	460,000,000		$ 347,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Cash Collateral Posted	141,000,000		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	439,000,000	[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	7		11
Forward gas price assets	1.84		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	$ 9.43		$ 9.20
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	9.00%		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	114.00%		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	$ 15,000,000	[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	12		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	69		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	$ (277,000,000)		$ (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	900.00%	[5]	800.00%	[6]
Derivatives Fair Value Footnotes [Abstract]
Fair Value Inputs, Discount for Lack of Marketability	3.00%		3.00%
Fair Value Inputs Renewable Factor	88.00%		89.00%
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward heat rate	1000.00%	[5]	900.00%	[6]
Derivatives Fair Value Footnotes [Abstract]
Fair Value Inputs, Discount for Lack of Marketability	8.00%		8.00%
Fair Value Inputs Renewable Factor	125.00%		121.00%
[1]	The fair values do not include cash collateral posted on level three positions of $141 million as of September 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.
[5]	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.
[6]	Quoted forward natural gas rates are utilized to project the forward power curve for the delivery of energy at specified future dates. The natural gas curve is extrapolated beyond its observable period to the end of the contract’s delivery.

Derivative Financial Instrume73

Derivative Financial Instruments - Summary of Interest Rate and Foreign Currency Hedges (Details) - USD ($) $ in Millions		Sep. 30, 2017		Dec. 31, 2016
Derivative [Line Items]
Mark-to-market derivatives assets		$ 699		$ 917
Derivative Asset, Noncurrent		426		492
Derivative Liability, Current		(178)		(282)
Derivative Liability, Noncurrent		(410)		(392)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		699		917
Derivative Asset, Noncurrent		416		476
Derivative Liability, Current		(158)		(263)
Derivative Liability, Noncurrent		(153)		(153)
InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		5		8
Derivative Asset, Noncurrent		10		20
Total mark-to-market derivative assets		15		28
Derivative Liability, Current		(8)		(8)
Derivative Liability, Noncurrent		(1)		(4)
Derivative Liability		9		12
Total mark-to-market derivative net assets (liabilities)		6		16
InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		5		8
Derivative Asset, Noncurrent		0		4
Total mark-to-market derivative assets		5		12
Derivative Liability, Current		(8)		(8)
Derivative Liability, Noncurrent		(1)		(4)
Derivative Liability		9		12
Total mark-to-market derivative net assets (liabilities)		(4)		0
Collateral And Netting [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	[1]	(1,969)	[2]	(2,769)	[3]
Derivative Asset, Noncurrent	[1]	(1,197)	[2]	(1,016)	[3]
Total mark-to-market derivative assets	[1]	(3,166)	[2]	(3,785)	[3]
Derivative Liability, Current	[1]	2,230	[2]	2,964	[3]
Derivative Liability, Noncurrent	[1]	1,351	[2]	1,150	[3]
Derivative Liability	[1]	(3,581)	[2]	(4,114)	[3]
Total mark-to-market derivative net assets (liabilities)	[1]	415	[2]	329	[3]
Collateral And Netting [Member] | InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	[4]	(10)		(13)
Derivative Asset, Noncurrent	[4]	(1)		(8)
Total mark-to-market derivative assets	[4]	(11)		(21)
Derivative Liability, Current	[4]	9		14
Derivative Liability, Noncurrent	[4]	1		9
Derivative Liability	[4]	(10)		(23)
Total mark-to-market derivative net assets (liabilities)	[4]	(1)		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		10		16
Total mark-to-market derivative assets		10		16
Derivative Liability, Current		0		0
Derivative Liability, Noncurrent		0		0
Derivative Liability		0		0
Total mark-to-market derivative net assets (liabilities)		10		16
Not Designated as Hedging Instrument, Economic Hedge [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets		2,608		3,623
Derivative Asset, Noncurrent		1,583		1,467
Total mark-to-market derivative assets		4,191		5,090
Derivative Liability, Current		(2,334)		(3,165)
Derivative Liability, Noncurrent		(1,476)		(1,274)
Derivative Liability		3,810		4,439
Total mark-to-market derivative net assets (liabilities)		381		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		15		17
Derivative Asset, Noncurrent		1		11
Total mark-to-market derivative assets		16		28
Derivative Liability, Current		(17)		(13)
Derivative Liability, Noncurrent		(2)		(8)
Derivative Liability		19		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		55		55
Derivative Asset, Noncurrent		30		21
Total mark-to-market derivative assets		85		76
Derivative Liability, Current		(46)		(54)
Derivative Liability, Noncurrent		(27)		(25)
Derivative Liability		73		79
Total mark-to-market derivative net assets (liabilities)		12		(3)
Not Designated as Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	[5]	0		4
Derivative Asset, Noncurrent	[5]	0		1
Total mark-to-market derivative assets	[5]	0		5
Derivative Liability, Current	[5]	0		(2)
Derivative Liability, Noncurrent	[5]	0		(2)
Derivative Liability	[5]	0		4
Total mark-to-market derivative net assets (liabilities)	[5]	$ 0		$ 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), $27 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 Instrume74

Derivative Financial Instruments - Summary of Gains and Losses on Hedges (Details) - Interest Expense [Member] - Fair Value Hedging [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Interest Rate Swap [Member]
Derivative [Line Items]
Gain (loss) on Swaps	$ (2)	$ (8)	$ (6)	$ 15
Price Risk Derivative [Member]
Derivative [Line Items]
Gain (loss) on Borrowings	$ 6	$ 14	$ 17	$ (3)

Derivative Financial Instrume75

Derivative Financial Instruments Derivative Financial Instruments - Summary of Derivative Fair Value Balances (Details) - USD ($) $ in Millions		Sep. 30, 2017		Dec. 31, 2016
Derivative [Line Items]
Mark-to-market derivative assets		$ 699		$ 917
Derivative Asset, Noncurrent		426		492
Derivative Liability, Current		(178)		(282)
Derivative Liability, Noncurrent		(410)		(392)
Derivative, Collateral, Right to Reclaim Cash		75		29
Margin Deposit Assets		(27)		158
Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets		694		909
Derivative Asset, Noncurrent		416		472
Total mark-to-market derivative assets		1,110		1,381
Derivative Liability, Current		(170)		(274)
Derivative Liability, Noncurrent		(409)		(388)
Total mark-to-market derivative liabilities		(579)		(662)
Total mark-to-market derivative net assets (liabilities)		531		719
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets		699		917
Derivative Asset, Noncurrent		416		476
Derivative Liability, Current		(158)		(263)
Derivative Liability, Noncurrent		(153)		(153)
Derivative Liability, Fair Value, Amount Offset Against Collateral	[1]	(638)		(627)
Exelon Generation Co L L C [Member] | Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets		694	[2]	909	[3]
Derivative Asset, Noncurrent		416	[2]	472	[3]
Total mark-to-market derivative assets		1,110	[2]	1,381	[3]
Derivative Liability, Current		(150)	[2]	(255)	[3]
Derivative Liability, Noncurrent		(152)	[2]	(149)	[3]
Total mark-to-market derivative liabilities		(302)	[2]	(404)	[3]
Total mark-to-market derivative net assets (liabilities)		808	[2]	977	[3]
Commonwealth Edison Co [Member]
Derivative [Line Items]
Derivative Liability, Current		(20)		(19)
Derivative Liability, Noncurrent		(257)		(239)
Delmarva Power and Light Company [Member] | Derivative [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
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]	(1,969)	[5]	(2,769)	[6]
Derivative Asset, Noncurrent	[4]	(1,197)	[5]	(1,016)	[6]
Total mark-to-market derivative assets	[4]	(3,166)	[5]	(3,785)	[6]
Derivative Liability, Current	[4]	2,230	[5]	2,964	[6]
Derivative Liability, Noncurrent	[4]	1,351	[5]	1,150	[6]
Total mark-to-market derivative liabilities	[4]	3,581	[5]	4,114	[6]
Total mark-to-market derivative net assets (liabilities)	[4]	415	[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		2,608		3,623
Derivative Asset, Noncurrent		1,583		1,467
Total mark-to-market derivative assets		4,191		5,090
Derivative Liability, Current		(2,334)		(3,165)
Derivative Liability, Noncurrent		(1,476)		(1,274)
Total mark-to-market derivative liabilities		(3,810)		(4,439)
Total mark-to-market derivative net assets (liabilities)		381		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]	(20)		(19)
Derivative Liability, Noncurrent	[7]	(257)		(239)
Total mark-to-market derivative liabilities	[7]	(277)		(258)
Total mark-to-market derivative net assets (liabilities)	[7]	(277)		(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		55		55
Derivative Asset, Noncurrent		30		21
Total mark-to-market derivative assets		85		76
Derivative Liability, Current		(46)		(54)
Derivative Liability, Noncurrent		(27)		(25)
Total mark-to-market derivative liabilities		(73)		(79)
Total mark-to-market derivative net assets (liabilities)		12		(3)
Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Liability, Collateral, Right to Reclaim Cash, Offset		(415)		(329)
Current liabilities collateral offset		138		95
Noncurrent liabilities collateral offset		93		62
Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative, Collateral, Right to Reclaim Cash		123		100
Margin Deposit Assets		27
Derivative Liability, Fair Value, Amount Offset Against Collateral				(158)
Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member] | Other Noncurrent Assets [Member]
Derivative [Line Items]
Derivative, Collateral, Right to Reclaim Cash		$ 61		$ 72
[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 $123 million and $61 million, respectively, and current and noncurrent liabilities are shown net of collateral of $138 million and $93 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $415 million at September 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), $27 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 Instrume76

Derivative Financial Instruments - Summary of AOCI related to Cash Flow Hedges (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative [Line Items]
Beginning Balance					$ (2,660)
Ending Balance		$ (2,589)			(2,589)
Income taxes		452		$ 340	595	$ 625
Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning Balance		(12)		(26)		(19)
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net		1		3		(1)
Ending Balance		(12)		(23)	(12)	(23)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Beginning Balance					(54)
Ending Balance		(36)			(36)
Income taxes		240		173	209	293
Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning Balance		(14)		(25)		(21)
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net		1		1		0
Ending Balance		(14)		(24)	(14)	(24)
Interest Expense [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		(1)	[1]			(3)	[2]
Interest Expense [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net		(1)	[1]			(3)	[2]
Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Income taxes	[3]			0		0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Income taxes		1			(2)	(2)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Derivative [Line Items]
Income taxes	[3]	(1)		1	2	3
Reclassification out of Accumulated Other Comprehensive Income [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes	[3]			0		0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Exelon Generation Co L L C [Member] | Cash Flow Hedging [Member] | Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Derivative [Line Items]
Income taxes	[3]	$ (1)		$ 1	$ 2	$ 3
[1]	Amount is net of related income tax benefit of $1 million for the three months ended September 30, 2017.
[2]	Amount is net of related income tax expense of $2 million for the nine months ended September 30, 2016.
[3]	Amounts in parenthesis represent a decrease in net income.

Derivative Financial Instrume77

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			$ (149)	$ (100)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	$ 73	$ 88	(161)	(113)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			(160)	(112)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	73	88	(161)	(113)
Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	52	187	(47)	(366)
Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	21	(99)	(114)	253
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	(2)	(2)	(6)
Unrealized Gain (Loss) on Derivatives	(3)	(1)	(6)	(9)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(3)	1	(4)	(3)
Foreign Exchange Contract [Member] | Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	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	(2)	(2)	(6)
Unrealized Gain (Loss) on Derivatives	(3)	(1)	(6)	(9)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(3)	1	(4)	(3)
Foreign Exchange Contract [Member] | Interest Expense [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	(2)	(2)	(6)
Unrealized Gain (Loss) on Derivatives	(3)	(1)	(6)	(9)
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	(3)	1	(4)	(3)
Commodity Contract [Member] | Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	132	280	123	127
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(77)	(92)	(164)	(484)
Unrealized Gain (Loss) on Derivatives	55	188	(41)	(357)
Commodity Contract [Member] | Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	45	(73)	(153)	36
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(24)	(26)	39	217
Unrealized Gain (Loss) on Derivatives	21	(99)	(114)	253
Commodity Contract [Member] | Interest Expense [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	177	207	(30)	163
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(101)	(118)	(125)	(267)
Unrealized Gain (Loss) on Derivatives	76	89	(155)	(104)
Commodity Contract [Member] | Interest Expense [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	177	207	(30)	163
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(101)	(118)	(125)	(267)
Unrealized Gain (Loss) on Derivatives	$ 76	$ 89	$ (155)	$ (104)

Derivative Financial Instrume78

Derivative Financial Instruments - Summary of Proprietary Trading Activities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			$ (149)	$ (100)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	$ 73	$ 88	(161)	(113)
Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	5	(1)	3	1
Commodity Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Commodity Contracts	11	4	17	18
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(6)	(6)	(13)	(17)
Unrealized Gain (Loss) on Derivatives	5	(2)	4	1
Foreign Exchange Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	1	1	1	2
Unrealized Gain (Loss) on Derivatives	0	1	(1)	0
Change in Unrealized Gain (Loss) on Hedged Item in Foreign Currency Fair Value Hedge	$ (1)	$ 0	$ (2)	$ (2)

Derivative Financial Instrume79

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Cash Collateral Posted		$ 19
Letters Of Credit Posted		12
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Financial institutions		48
Investor-owned utilities, marketers and power producers		538
Energy Cooperatives And Municipalities		525
Other		146
Cash Collateral Posted		460	$ 347
Letters Of Credit Posted		255	$ 284
Exelon Generation Co L L C [Member] | Total Exposure Before Credit Collateral [Member]
Derivative [Line Items]
Investment grade		828
Non-investment grade		44
No external ratings - internally rated - investment grade		316
No external ratings - internally rated - non-investment grade		100
Total		1,288
Exelon Generation Co L L C [Member] | Credit Collateral [Member]
Derivative [Line Items]
Investment grade		9
Non-investment grade		4
No external ratings - internally rated - investment grade		0
No external ratings - internally rated - non-investment grade		18
Total	[1]	31
Exelon Generation Co L L C [Member] | Net Exposure [Member]
Derivative [Line Items]
Investment grade		819
Non-investment grade		40
No external ratings - internally rated - investment grade		316
No external ratings - internally rated - non-investment grade		82
Total		1,257
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
No external ratings - internally rated - investment grade
No external ratings - internally rated - non-investment grade
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		278
Non-investment grade
No external ratings - internally rated - investment grade
No external ratings - internally rated - non-investment grade
Total		$ 278
[1]	As of September 30, 2017, credit collateral held from counterparties where Generation had credit exposure included $19 million of cash and $12 million of letters of credit. The credit collateral does not include non-liquid collateral.

Derivative Financial Instrume80

Derivative Financial Instruments - Summary of Credit Risk Related Contingent Features (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Aggregate fair value of derivatives with credit-risk-related contingent features	[1]	$ (916)	$ (960)
Contractual right of offset related to derivative assets	[2]	638	627
Net liability position after contractual right of offset	[3]	$ (278)	$ (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 Instrume81

Derivative Financial Instruments - Narrative (Details) $ in Thousands		3 Months Ended			6 Months Ended	9 Months Ended
		Sep. 30, 2017USD ($)GWh		Sep. 30, 2016USD ($)GWh	Jun. 30, 2016USD ($)	Sep. 30, 2017USD ($)GWh		Sep. 30, 2016USD ($)GWh	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)		Mar. 31, 2016USD ($)
Derivative [Line Items]
Income taxes		$ 452,000		$ 340,000		$ 595,000		$ 625,000
Derivative, Notional Amount					$ 100,000							$ 600,000
Derivative, Loss on Derivative					3,000
Derivative Instruments, Loss Recognized in Other Comprehensive Income (Loss), Effective Portion					$ 3,000
Ineffective portion recognized in income		4,000		6,000		11,000		12,000
Mark-to-market derivative liabilities (noncurrent liabilities)		410,000				410,000				$ 392,000
Cash collateral posted		19,000				19,000
Letters of credit posted		12,000				12,000
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes		240,000		$ 173,000		209,000		$ 293,000
Mark-to-market derivative liabilities (noncurrent liabilities)		153,000				153,000				153,000
Cash collateral received not offset against net derivative positions		(3,000)				(3,000)				(8,000)
Cash collateral posted		460,000				460,000				347,000
Letters of credit held		29,000				29,000				28,000
Letters of credit posted		255,000				255,000				284,000
Cash collateral held		49,000				49,000				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		$ (4,000)				$ (4,000)
Derivative, Nonmonetary Notional Amount, Energy Measure | GWh		2,601		1,506		6,763		4,015
Commonwealth Edison Company [Member]
Derivative [Line Items]
Cash collateral held		$ 10,000				$ 10,000
Commonwealth Edison Co [Member]
Derivative [Line Items]
Income taxes		131,000		$ 75,000		328,000		$ 244,000
Mark-to-market derivative liabilities (noncurrent liabilities)		257,000				257,000				239,000
Cash collateral held		21,000				21,000
Incremental collateral for loss of investment grade credit rating		3,000				3,000
Credit Exposure Under Off System Sales		1,000				1,000
PECO Energy Co [Member]
Derivative [Line Items]
Income taxes		28,000		54,000		$ 84,000		121,000
Estimated percentage of natural gas purchases hedged						20.00%
Incremental collateral for loss of investment grade credit rating		20,000				$ 20,000
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Income taxes		40,000		36,000		151,000		109,000
Incremental collateral for loss of investment grade credit rating		28,000				28,000
Credit Exposure Under Off System Sales		1,000				1,000
Delmarva Power and Light Company [Member]
Derivative [Line Items]
Income taxes		19,000		19,000		43,000		18,000
Incremental collateral for loss of investment grade credit rating		9,000				$ 9,000
Minimum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months						98.00%
Expected Generation Hedged In Year Two						79.00%
Expected generation hedged in year three						45.00%
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						101.00%
Expected Generation Hedged In Year Two						82.00%
Expected generation hedged in year three						48.00%
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			$ 164,000
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]
Derivative, Notional Amount		491,000				491,000
Foreign Exchange Contract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Notional Amount		111,000				111,000
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		531,000				531,000				719,000
Mark-to-market derivative liabilities (noncurrent liabilities)		409,000				409,000				388,000
Derivative Asset		1,110,000				1,110,000				1,381,000
Derivative [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Fair Value, Net		808,000	[1]			808,000	[1]			977,000	[2]
Mark-to-market derivative liabilities (noncurrent liabilities)		152,000	[1]			152,000	[1]			149,000	[2]
Derivative Asset		1,110,000	[1]			1,110,000	[1]			1,381,000	[2]
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)		0				0				0
Derivative Asset		0				0				0
InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Derivative, Fair Value, Net		6,000				6,000				16,000
Mark-to-market derivative liabilities (noncurrent liabilities)		1,000				1,000				4,000
Derivative Asset		15,000				15,000				28,000
InterestRateAndForeignExchangeContract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Fair Value, Net		(4,000)				(4,000)				0
Mark-to-market derivative liabilities (noncurrent liabilities)		1,000				1,000				4,000
Derivative Asset		5,000				5,000				12,000
Fair Value Hedging [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		800,000				800,000				800,000
Derivative Asset		10,000				10,000				$ 16,000
ExGen Texas Power [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		491,000				491,000
ExGen Texas Power [Member] | Interest Rate Contract [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities (noncurrent liabilities)		6,000				6,000
Derivative, Gain (Loss) on Derivative, Net		(2,000)				2,000
Sacramento PV Energy [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount												25,000
Constellation Solar Horizons Financing [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount												$ 24,000
Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Income taxes	[3]			0				0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes	[3]			0				0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Income taxes		1,000				(2,000)		(2,000)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Income taxes	[3]	(1,000)		1,000		2,000		3,000
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [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]	(1,000)		$ 1,000		2,000		$ 3,000
Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		18,000				18,000
PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from affiliated electric and gas utility		22,000				22,000
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		22,000				22,000
Potomac Electric Power Company [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		34,000				34,000
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		$ 7,000				$ 7,000
[1]	Current and noncurrent assets are shown net of collateral of $123 million and $61 million, respectively, and current and noncurrent liabilities are shown net of collateral of $138 million and $93 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $415 million at September 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	Sep. 30, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Commercial paper borrowings	$ 118	$ 688
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	65	0
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	0	620
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	0	45
Pepco Holdings LLC [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	118	23
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	$ 54	$ 0

Debt and Credit Agreements - Is

Debt and Credit Agreements - Issuance of Long-Term Debt (Details) - USD ($)		3 Months Ended	9 Months Ended
		Sep. 30, 2017	Sep. 30, 2014	Jun. 30, 2014
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Interest Rate		3.497%		2.50%
JSNotes350June2022 [Member] | Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Interest Rate	[1]	3.50%
Debt Instrument, Face Amount		$ 1,150,000,000
PECO Energy Co [Member] | FRMB370Sep2047 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate		3.70%
Debt Instrument, Face Amount		$ 325,000,000
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		$ 4,000,000
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		$ 10,000,000
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		$ 17,000,000
Exelon Generation Co L L C [Member] | AGEPFNotesNov2017 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 14,000,000
Debt Instrument, Interest Rate Terms		LIBOR + 1.25%
Exelon Generation Co L L C [Member] | SeniorUnsecured295Jan2020 [Member] | Senior 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 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%	LIBOR plus 4.75%
Commonwealth Edison Co [Member] | FMB295Aug2027 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate		2.95%
Debt Instrument, Face Amount		$ 350,000,000
Commonwealth Edison Co [Member] | FMB375Aug2047 [Member] | First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate		3.75%
Debt Instrument, Face Amount		$ 650,000,000
Baltimore Gas and Electric Company [Member] | Notes375Aug2047 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate		3.75%
Debt Instrument, Face Amount		$ 300,000,000
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		$ 2,000,000
[1]	(a)See the Junior Subordinated Notes discussion below for further information.

Debt and Credit Agreements - Na

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

1 Months Ended

3 Months Ended

5 Months Ended

9 Months Ended

Jun. 30, 2014

Sep. 30, 2017

May 26, 2016

Sep. 30, 2017

Sep. 30, 2016

Sep. 30, 2014

Mar. 23, 2017

Jan. 09, 2017

Jun. 30, 2016

Mar. 31, 2016

Jan. 13, 2016

Aug. 10, 2013

Jan. 31, 2013

Aug. 01, 2011

Debt Instrument [Line Items]

Derivative, Notional Amount

$ 100,000,000

$ 600,000,000

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

$ 1,150,000,000

$ 1,150,000,000

Extinguishment of Debt, Amount

$ 11,000,000

Repayments of Long-term Debt

1,728,000,000

944,000,000

Junior Subordinated Debt [Member]

Debt Instrument [Line Items]

Junior Subordinated Notes

$ 1,150,000,000

$ 1,150,000,000

Equity Units Issued

23

Debt Instrument, Convertible, Conversion Price

$ 50

Interest Rate

2.50%

3.497%

3.497%

Loss on Reissuance, Treasury Stock

$ 1,050,000,000

Stock Issued During Period, Shares, Treasury Stock Reissued

33

Revolving Credit Facility [Member]

Debt Instrument [Line Items]

Line of Credit Facility, Maximum Borrowing Capacity

$ 500,000,000

Line of Credit Facility, Increase (Decrease), Net

$ 600,000,000

Corporate, Non-Segment [Member]

Debt Instrument [Line Items]

Short-term Bank Loans and Notes Payable

$ 500,000,000

Debt Instrument, Interest Rate Terms

LIBOR plus 1%

Pepco Holdings LLC [Member]

Debt Instrument [Line Items]

Short-term Bank Loans and Notes Payable

$ 500,000,000

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

$ 1,500,000,000

Line of Credit Facility, Increase (Decrease), Net

$ 900,000,000

Exelon Generation Co L L C [Member]

Debt Instrument [Line Items]

Repayments of Long-term Debt

$ 541,000,000

164,000,000

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

Debt Instrument [Line Items]

Line of Credit Facility, Maximum Borrowing Capacity

$ 100,000,000

$ 75,000,000

Baltimore Gas and Electric Company [Member]

Debt Instrument [Line Items]

Repayments of Long-term Debt

$ 41,000,000

$ 39,000,000

Preferred Stock, Par or Stated Value Per Share

$ 25.19

$ 25.19

Preferred Stock, Dividend Rate, Percentage

6.20%

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

Debt Instrument [Line Items]

Debt Instrument, Face Amount

$ 675,000,000

Derivative, Notional Amount

$ 505,000,000

Derivative, Fixed Interest Rate

2.34%

2.34%

Long-term Debt, Gross

$ 660,000,000

$ 660,000,000

Line of Credit Facility, Maximum Borrowing Capacity

20,000,000

20,000,000

EGTP475Sep2021 [Member] | Exelon Generation Co L L C [Member] | Long-term Debt [Member]

Debt Instrument [Line Items]

Debt Instrument, Face Amount

$ 6,000,000

6,000,000

Debt Instrument, Interest Rate Terms

LIBOR + 4.75%

LIBOR plus 4.75%

AGEPFNotesNov2017 [Member] | Exelon Generation Co L L C [Member] | Long-term Debt [Member]

Debt Instrument [Line Items]

Debt Instrument, Face Amount

$ 14,000,000

$ 14,000,000

Debt Instrument, Interest Rate Terms

LIBOR + 1.25%

AGEPFNotesNov2017 [Member] | AGE Biomass project [Member] | Long-term Debt [Member]

Debt Instrument [Line Items]

Debt Instrument, Interest Rate Terms

LIBOR + 1.25%

Interest Expense, Long-term Debt

$ 6,000,000

Repayments of Long-term Debt

$ 228,000,000

Income Taxes - Reconciliation t

Income Taxes - Reconciliation to Effective Tax Rate (Details)		3 Months Ended			6 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Mar. 23, 2016	Sep. 30, 2016	[3]	Sep. 30, 2017	Sep. 30, 2016
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		2.20%	3.80%				0.70%	2.50%	[1]
Qualified nuclear decommissioning trust fund income		2.60%	4.00%				4.00%	4.80%
Amortization of investment tax credit, including deferred taxes on basis difference		(1.10%)	(0.90%)				(0.90%)	(1.30%)
Plant basis differences		(2.60%)	(3.00%)				(3.40%)	(4.50%)
Production tax credits and other credits		(2.20%)	(2.90%)				(1.80%)	(4.10%)
Noncontrolling interests		0.50%	0.20%				0.20%	0.50%
Statute of limitations expiration			(0.10%)					(0.50%)
EffectiveIncomeTaxRateReconciliationPenalties			4.30%					2.30%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent			(0.60%)				(5.40%)	6.20%
Fitzpatrick bargain purchase gain		(0.20%)					(3.20%)
Like-kind exchange(a)	[2]						(1.70%)
Other		(0.10%)	(0.80%)				(0.00%)	(1.80%)
Effective income tax rate		34.10%	39.00%				23.50%	39.10%
Exelon Generation Co L L C [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		5.60%	2.60%				2.10%	2.60%	[1]
Qualified nuclear decommissioning trust fund income		5.80%	7.80%				14.00%	8.80%
Amortization of investment tax credit, including deferred taxes on basis difference		(2.20%)	(1.60%)				(2.70%)	(2.00%)
Plant basis differences		0.00%	0.00%				0.00%	0.00%
Production tax credits and other credits		(4.80%)	(5.70%)				(6.20%)	(7.60%)
Noncontrolling interests		1.00%	0.50%				0.70%	0.90%
Statute of limitations expiration			0.30%					(1.70%)
EffectiveIncomeTaxRateReconciliationPenalties			0.00%					0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent			0.00%				(2.50%)	0.00%
Fitzpatrick bargain purchase gain		(0.40%)					(11.20%)
Like-kind exchange(a)	[2]						0.00%
Other		0.30%	(0.50%)				(0.40%)	(2.10%)
Effective income tax rate		40.30%	38.40%				28.80%	33.90%
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		6.60%	7.30%				5.90%	5.40%	[1]
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%)	(0.60%)				(0.20%)	(0.30%)
Plant basis differences		(0.30%)	(1.90%)				(0.30%)	(0.60%)
Production tax credits and other credits		0.00%	(0.10%)				0.00%	0.00%
Noncontrolling interests		0.00%	0.00%				0.00%	0.00%
Statute of limitations expiration			0.00%					0.00%
EffectiveIncomeTaxRateReconciliationPenalties			27.20%					5.60%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent			0.00%				0.00%	0.00%
Fitzpatrick bargain purchase gain		0.00%					0.00%
Like-kind exchange(a)	[2]						1.70%
Other		(0.20%)	0.10%				0.20%	(0.00%)
Effective income tax rate		40.90%	67.00%				42.30%	45.10%
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		(0.10%)	2.40%				(0.10%)	1.30%	[1]
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		(14.60%)	(6.70%)				(14.40%)	(8.80%)
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%					0.00%
EffectiveIncomeTaxRateReconciliationPenalties			0.00%					0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent			0.00%				0.00%	0.00%
Fitzpatrick bargain purchase gain		0.00%					0.00%
Like-kind exchange(a)	[2]						0.00%
Other		(0.20%)	0.10%				(0.00%)	(1.50%)
Effective income tax rate		20.00%	30.70%				20.40%	25.90%
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		5.30%	5.20%				5.20%	4.80%	[1]
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%)	(0.20%)				(0.10%)	(0.20%)
Plant basis differences		(0.80%)	(0.50%)				(0.80%)	(3.30%)
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%					0.00%
EffectiveIncomeTaxRateReconciliationPenalties			0.00%					0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent			0.00%				0.00%	0.00%
Fitzpatrick bargain purchase gain		0.00%					0.00%
Like-kind exchange(a)	[2]						0.00%
Other		(0.20%)	(0.40%)				0.20%	(0.00%)
Effective income tax rate		39.20%	39.10%				39.50%	36.30%
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%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit		2.20%	5.60%				3.00%	23.00%	[1]
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%)	(0.00%)				(0.10%)	(0.20%)
Plant basis differences		(6.70%)	(6.70%)				(6.30%)	(29.00%)
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%					0.00%
EffectiveIncomeTaxRateReconciliationPenalties			0.00%					0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent			(2.30%)				(8.00%)	36.70%
Fitzpatrick bargain purchase gain		0.00%					0.00%
Like-kind exchange(a)	[2]						0.00%
Other		(0.00%)	(0.90%)				(0.30%)	(2.50%)
Effective income tax rate		30.40%	30.70%				23.30%	63.00%
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%	[3]
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit		5.30%	5.20%				5.10%	310.50%	[1],[3]
Qualified nuclear decommissioning trust fund income		(0.00%)	(0.00%)				(0.00%)	(0.00%)	[3]
Amortization of investment tax credit, including deferred taxes on basis difference		(0.20%)	(0.20%)				(0.20%)	(17.90%)	[3]
Plant basis differences		(1.90%)	(1.30%)				(1.80%)	(98.60%)	[3]
Production tax credits and other credits		0.00%	0.00%				0.00%	0.00%	[3]
Noncontrolling interests		0.00%	0.00%				0.00%	0.00%	[3]
Statute of limitations expiration			0.00%					0.00%	[3]
EffectiveIncomeTaxRateReconciliationPenalties			0.00%					0.00%	[3]
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent			(8.60%)				(10.00%)	635.90%	[3]
Fitzpatrick bargain purchase gain		0.00%					0.00%
Like-kind exchange(a)	[2]						0.00%
Other		(0.20%)	0.10%				0.60%	35.10%	[3]
Effective income tax rate		38.00%	30.20%				28.70%	900.00%	[3]
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%	[3]
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit		5.60%	6.10%				5.60%	5.50%	[1],[3]
Qualified nuclear decommissioning trust fund income		(0.00%)	(0.00%)				(0.00%)	(0.00%)	[3]
Amortization of investment tax credit, including deferred taxes on basis difference		(0.40%)	(0.10%)				(0.40%)	0.50%	[3]
Plant basis differences		(3.40%)	(4.60%)				(3.40%)	7.80%	[3]
Production tax credits and other credits		0.00%	0.00%				0.00%	0.00%	[3]
Noncontrolling interests		0.00%	0.00%				0.00%	0.00%	[3]
Statute of limitations expiration			0.00%					0.00%	[3]
EffectiveIncomeTaxRateReconciliationPenalties			0.00%					0.00%	[3]
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent			(2.90%)				(23.00%)	(35.40%)	[3]
Fitzpatrick bargain purchase gain		0.00%					0.00%
Like-kind exchange(a)	[2]						0.00%
Other		0.10%	(0.60%)				(0.30%)	0.40%	[3]
Effective income tax rate		36.90%	32.90%				13.50%	13.80%	[3]
Pepco Holdings LLC [Member] | Successor [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		5.10%	5.60%		4.40%	[1]	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%)	(0.10%)		0.50%		(0.20%)
Plant basis differences		(4.90%)	(5.00%)		17.50%		(4.60%)
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%		0.00%
EffectiveIncomeTaxRateReconciliationPenalties			0.00%		0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent			(5.70%)		(49.80%)		(11.80%)
Fitzpatrick bargain purchase gain		0.00%					0.00%
Like-kind exchange(a)	[2]						0.00%
Other		0.20%	(0.70%)		1.40%		(0.00%)
Effective income tax rate		35.20%	29.10%		9.00%		23.30%
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	[1]			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%
EffectiveIncomeTaxRateReconciliationPenalties				0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Other, Percent				11.10%
Other				3.60%
Effective income tax rate				47.20%
[1]	Includes a remeasurement of uncertain state income tax positions for Pepco and DPL.
[2]	See Like-Kind Exchange within the Other Income Tax Matters section below for further details.
[3]	DPL and ACE recognized a loss before income taxes for the nine months ended September 30, 2016, and PHI recognized a loss before income taxes for the period of March 24, 2016, through September 30, 2016. As a result, positive percentages represent an income tax benefit for the periods presented.

Income Taxes Income Tax Unrecog

Income Taxes Income Tax Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 738	$ 916
Exelon Generation Co L L C [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	468	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	120	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	$ 8	$ 22

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2017	Sep. 30, 2017	Jun. 30, 2016	Dec. 31, 2009
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	$ 738		$ 916			$ 738
Unrecognized Tax Benefits, Interest on Income Taxes Expense				$ 94
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				106		90
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
Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	468		490			468
Commonwealth Edison Co [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits	2		(12)			2
Unrecognized Tax Benefits, Interest on Income Taxes Expense				64
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
Decrease in Unrecognized Tax Benefits is Reasonably Possible	2					2
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]
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	120		172			120
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	8		$ 22			8
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]
Deferred Tax Assets, State Taxes	272	$ 8				272
Unrecognized tax benefits that if recognized would affect the effective tax rate	0					0
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities		20
Decrease in Unrecognized Tax Benefits is Reasonably Possible	676					676
Increase (Decrease) in Other Deferred Liability	$ 250	28
Deferred State and Local Income Tax Expense (Benefit)						20
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent	9.50%				7.75%
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	$ 462					462
Decrease in Unrecognized Tax Benefits is Reasonably Possible	469					469
Increase (Decrease) in Other Deferred Liability	20
Deferred State and Local Income Tax Expense (Benefit)						20
State and Local Jurisdiction [Member] | Commonwealth Edison Co [Member]
Income Tax Additional Narrative Information [Line Items]
Deferred Tax Assets, State Taxes	272					272
Increase (Decrease) in Other Deferred Liability	270
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]
Deferred Tax Assets, State Taxes		8
Decrease in Unrecognized Tax Benefits is Reasonably Possible	88					88
Increase (Decrease) in Other Deferred Liability		8
State and Local Jurisdiction [Member] | Potomac Electric Power Company [Member]
Income Tax Additional Narrative Information [Line Items]
Deferred Tax Assets, State Taxes		8
Decrease in Unrecognized Tax Benefits is Reasonably Possible	59					59
Increase (Decrease) in Other Deferred Liability		$ 8
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
State and Local Jurisdiction [Member] | Atlantic City Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 8					$ 8

Nuclear Decommissioning - Rollf

Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended
		Mar. 31, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]			$ 350	$ 333
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]			350	332
Asset Retirement Obligation, Period Increase (Decrease)				632
Asset Retirement Obligation, Period Increase (Decrease)					$ 0
Recovery Stranded Costs		$ 4				$ 24
Current portion of ARO						$ 10
Exelon Generation Co L L C [Member] | Nuclear Decommissioning [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense				342
Asset Retirement Obligation, Period Increase (Decrease)				(148)
Asset Retirement Obligation, Liabilities Settled				(6)
Asset Retirement Obligation, Revision of Estimate			$ 417	444
Current portion of ARO				$ 12
[1]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income

Nuclear Decommissioning (Detail

Nuclear Decommissioning (Details) - USD ($) $ in Millions		1 Months Ended		3 Months Ended	9 Months Ended		12 Months Ended
		May 31, 2017	Mar. 31, 2017	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Nuclear Decommissioning Additional Narrative Information [Line Items]
Increase (Decrease) in Asset Retirement Obligations				$ 27
Decommissioning Liability, Noncurrent				0	$ 0		$ 14
Asset Retirement Obligation, Revision of Estimate						$ 0
Decommissioning Fund Investments				12,966	12,966		11,061
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Recovery Stranded Costs			$ 4				24
Decommissioning Liability, Noncurrent				0	0		14
Asset Retirement Obligation, Period Increase (Decrease)					632
Asset Retirement Obligation, Revision of Estimate						$ 0
Decommissioning Fund Investments				12,966	12,966		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			180
Asset Retirement Obligation, Period Increase (Decrease)					(148)
Proceeds from Customers	[1]			9,366	9,366		$ 8,734
Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent				$ 112	$ 112
[1]	Includes $12 million and $10 million for the current portion of the ARO at September 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		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Unrealized Losses On Nuclear Decommissioning Trust Fund Investment [Line Items]
Unrealized Gain (Loss) on Investments		$ 4	$ 5	$ 5	$ 2
Collateral Pledged [Member] | Regulated Operation [Member]
Unrealized Losses On Nuclear Decommissioning Trust Fund Investment [Line Items]
Unrealized Gain (Loss) on Investments	[1]	44	155	253	286
Collateral Pledged [Member] | Unregulated Operation [Member]
Unrealized Losses On Nuclear Decommissioning Trust Fund Investment [Line Items]
Unrealized Gain (Loss) on Investments	[2],[3]	$ 111	$ 116	$ 347	$ 216
[1]	Net unrealized gains related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets.
[2]	Excludes $4 million and $5 million of net unrealized losses related to the Zion Station pledged assets for the three months ended September 30, 2017 and 2016 respectively. Excludes $5 million and $2 million of net unrealized losses related to the Zion Station pledged assets for the nine months ended September 30, 2017 and 2016, respectively. Net unrealized 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.
[3]	Net unrealized gains related to Generation’s NDT funds with Non-Regulatory Agreement Units are included within Other, net in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income.

Nuclear Decommissioning - Asset

Nuclear Decommissioning - Assets, Payables and Withdrawals by ZionSolutions (Details) - USD ($) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2017	Dec. 31, 2016
Nuclear Decommissioning Additional Narrative Information [Line Items]
Pledged assets for Zion Station decommissioning		$ 57	$ 113
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Held-to-maturity Securities Pledged as Collateral		57	113
Accounts Payable, Interest-bearing, Noncurrent	[1]	53	104
Accounts Payable, Interest-bearing, Current	[2]	53	90
Asset Retirement Obligation, Cash Paid to Settle	[3]	928	878
Pledged assets for Zion Station decommissioning		$ 57	$ 113
[1]	Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT funds. The NDT funds will be utilized to satisfy the tax obligations as gains and losses are realized.
[2]	Included in Other current liabilities within Exelon’s and Generation’s Consolidated Balance Sheets.
[3]	Includes project expenses to decommission Zion Station and estimated tax payments on Zion Station NDT fund earnings.

Retirement Benefits - Narrative

Retirement Benefits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2017
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	$ 16	38
Increase (Decrease) in Obligation, Other Postretirement Benefits	$ 17	$ 11

Retirement Benefits - Calculati

Retirement Benefits - Calculation of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended					9 Months Ended
	Sep. 30, 2017	[1]	Sep. 30, 2016	[2]	Mar. 23, 2016	Sep. 30, 2017	[1]	Sep. 30, 2016	[2]
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 98		$ 92			$ 290		$ 262
Interest cost	211		215			632		616
Expected return on assets	(300)		(293)			(898)		(847)
Amortization of:
Prior service (benefit) cost	(1)		3			0		10
Actuarial loss	152		142			455		411
Settlement charges	1		0			3		0
Net periodic benefit cost	161		159			482		452
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	26		27			79		80
Interest cost	45		47			136		138
Expected return on assets	(39)		(42)			(121)		(121)
Amortization of:
Prior service (benefit) cost	(47)		(48)			(140)		(138)
Actuarial loss	15		18			46		47
Settlement charges	0		0			0		0
Net periodic benefit cost	$ 0		$ 2			$ 0		$ 6
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 (benefit) cost					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 (benefit) cost					(3)
Actuarial loss					2
Net periodic benefit cost					$ 1
[1]	FitzPatrick net benefit costs are included for the period after acquisition.
[2]	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	9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016		Mar. 23, 2016	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		$ 161		$ 161				$ 482		$ 458
Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	[1]	13		13				40		37
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		57	[2]	54				170	[2]	163
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		44		41				131		124
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		7		8				21		25
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		16		17				47		50
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)								48		51
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		6	[3]	8	[3]	$ 7		19	[3]	24	[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		10	[3]	13	[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		10	[3]	11	[3]
Pepco Holdings LLC [Member] | Successor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		24		28			$ 58	72
Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)						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	[3],[4]	$ 12	[3],[4]	$ 9		$ 33	[3],[4]	$ 33	[3],[4]
[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]	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 nine months ended September 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.
[4]	These amounts represent amounts billed to Pepco, DPL, and ACE through intercompany allocations. These amounts are not included in Pepco, DPL, or ACE amounts above.

Retirement Benefits - Defined C

Retirement Benefits - Defined Contribution Savings Plans (Details) - USD ($) $ in Millions		3 Months Ended					6 Months Ended	9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016		Mar. 23, 2016	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		$ 34		$ 51				$ 97		$ 107
Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	2		2				7		9
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		14		31				42		56
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		9		10				24		23
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		3		3				7		7
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		3		2				7		5
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		1	[2]	0	[2]	$ 1		3	[2]	2	[2]
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		1	[2]	1	[2]	1		2	[2]	2	[2]
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		0		0				1		1
Pepco Holdings LLC [Member] | Successor [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		3		3			$ 7	10
Pepco Holdings LLC [Member] | Predecessor [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions						3
Pepco Holdings LLC [Member] | Corporate, Non-Segment [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		$ 1	[2],[3]	$ 2	[2],[3]	$ 1		$ 4	[2],[3]	$ 5	[2],[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]	Pepco's, DPL's and PHISCO's matching contributions for the nine months ended September 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 nine months ended September 30, 2016.
[3]	These amounts represent amounts billed to Pepco, DPL, and ACE through intercompany allocations. These amounts are not included in Pepco, DPL, or ACE amounts above.

Severance - Ongoing Severance P

Severance - Ongoing Severance Plans (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended	9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 1	$ 8		$ 10	$ 12
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	0	7		4	10
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1		2	2
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	0	0		2	1
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1			1
Pepco Holdings LLC [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		0	1		1	1
Pepco Holdings LLC [Member] | Successor [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1	1	$ 1	4
Potomac Electric Power Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	1	0		2	0
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1			2
Delmarva Power and Light Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	0	0		1	0
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs					1
Atlantic City Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]	$ 0	$ 0		1	$ 0
Atlantic City Electric Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs					$ 1
[1]	The amounts above for Generation include $2 million for amounts billed by BSC through intercompany allocations for the nine months ended September 30, 2017 and $1 million and $2 million for the three and nine months ended September 30, 2016, respectively. The amounts above for ComEd include $1 million for amounts billed by BSC through intercompany allocations for the three and nine months ended September 30, 2016. The amounts above for PHI include less than $1 million and $1 million billed by BSC through intercompany allocations for the three and nine months ended September 30, 2017, respectively, and $1 million for the three and nine months ended September 30, 2016. Amounts billed by PHISCO to Pepco were $1 million and $2 million for the three and nine months ended September 30, 2017, respectively. Amounts billed by PHISCO to DPL and ACE were $1 million, each, for the nine months ended September 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and nine months ended September 30, 2016.

Severance Severance - Cost Mana

Severance Severance - Cost Management Program-Related (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 1		$ 8		$ 10		$ 12
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		7	[1]	1	[2]	6	[1]	18	[2]
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[3]	0		7		4		10
Exelon Generation Co L L C [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		7	[1]	1	[2]	6	[1]	13	[2]
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				1		2		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]	0		0		2		1
Commonwealth Edison Co [Member] | Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		0	[1]	0	[2]	0	[1]	3	[2]
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				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]	0	[2]	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]	$ 0	[2]	$ 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 nine months ended September 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 nine months ended September 30, 2016.
[3]	The amounts above for Generation include $2 million for amounts billed by BSC through intercompany allocations for the nine months ended September 30, 2017 and $1 million and $2 million for the three and nine months ended September 30, 2016, respectively. The amounts above for ComEd include $1 million for amounts billed by BSC through intercompany allocations for the three and nine months ended September 30, 2016. The amounts above for PHI include less than $1 million and $1 million billed by BSC through intercompany allocations for the three and nine months ended September 30, 2017, respectively, and $1 million for the three and nine months ended September 30, 2016. Amounts billed by PHISCO to Pepco were $1 million and $2 million for the three and nine months ended September 30, 2017, respectively. Amounts billed by PHISCO to DPL and ACE were $1 million, each, for the nine months ended September 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and nine months ended September 30, 2016.

Severance - PHI Merger (Details

Severance - PHI Merger (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended	9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Severance Costs		$ 1	$ 8		$ 10	$ 12
PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]					55
Exelon Generation Co L L C [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	0	7		4	10
Exelon Generation Co L L C [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]					9
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1		2	2
Exelon Generation Co L L C [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs						8
Commonwealth Edison Co [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	0	0		2	1
Commonwealth Edison Co [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]					2
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			1			1
Commonwealth Edison Co [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs						2
PECO Energy Co [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]					1
PECO Energy Co [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs						1
Baltimore Gas and Electric Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]					1
Baltimore Gas and Electric Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs						1
Pepco Holdings LLC [Member] | Successor [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1	1	$ 1	4
Pepco Holdings LLC [Member] | Successor [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]			$ 42
Pepco Holdings LLC [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		0	1		1	1
Potomac Electric Power Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	1	0		2	0
Potomac Electric Power Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]					20
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		1			2
Potomac Electric Power Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs						19
Delmarva Power and Light Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	0	0		1	0
Delmarva Power and Light Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]					12
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs					1
Delmarva Power and Light Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs						11
Atlantic City Electric Company [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[2]	$ 0	$ 0		1	0
Atlantic City Electric Company [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	[1]					10
Atlantic City Electric Company [Member] | Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs					$ 1
Atlantic City Electric Company [Member] | Corporate, Non-Segment [Member] | PHI Merger [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs						$ 10
[1]	The amounts above for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE include $8 million, $2 million, $1 million, $1 million, $19 million, $11 million and $10 million, respectively, for amounts billed by BSC and/or PHISCO through intercompany allocations for the nine months ended September 30, 2016.
[2]	The amounts above for Generation include $2 million for amounts billed by BSC through intercompany allocations for the nine months ended September 30, 2017 and $1 million and $2 million for the three and nine months ended September 30, 2016, respectively. The amounts above for ComEd include $1 million for amounts billed by BSC through intercompany allocations for the three and nine months ended September 30, 2016. The amounts above for PHI include less than $1 million and $1 million billed by BSC through intercompany allocations for the three and nine months ended September 30, 2017, respectively, and $1 million for the three and nine months ended September 30, 2016. Amounts billed by PHISCO to Pepco were $1 million and $2 million for the three and nine months ended September 30, 2017, respectively. Amounts billed by PHISCO to DPL and ACE were $1 million, each, for the nine months ended September 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and nine months ended September 30, 2016.

Severance - Severance Liabiliti

Severance - Severance Liabilities (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended	9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Reserve [Roll Forward]
Severance Costs		$ 1	$ 8		$ 10	$ 12
Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance					88
Severance Costs	[1]				33
Payments for Restructuring					(24)
Ending Balance		97			97
Exelon Generation Co L L C [Member]
Restructuring Reserve [Roll Forward]
Severance Costs	[2]	0	7		4	10
Exelon Generation Co L L C [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance					36
Severance Costs	[1]				25
Payments for Restructuring					(7)
Ending Balance		54			54
Commonwealth Edison Co [Member]
Restructuring Reserve [Roll Forward]
Severance Costs	[2]	0	0		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		1	1	$ 1	4
Pepco Holdings LLC [Member] | Successor [Member] | Employee Severance [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance					29
Severance Costs	[1]				3
Payments for Restructuring					(11)
Ending Balance		21			21
Potomac Electric Power Company [Member]
Restructuring Reserve [Roll Forward]
Severance Costs	[2]	1	0		2	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]	0	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]	0	$ 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 $2 million for amounts billed by BSC through intercompany allocations for the nine months ended September 30, 2017 and $1 million and $2 million for the three and nine months ended September 30, 2016, respectively. The amounts above for ComEd include $1 million for amounts billed by BSC through intercompany allocations for the three and nine months ended September 30, 2016. The amounts above for PHI include less than $1 million and $1 million billed by BSC through intercompany allocations for the three and nine months ended September 30, 2017, respectively, and $1 million for the three and nine months ended September 30, 2016. Amounts billed by PHISCO to Pepco were $1 million and $2 million for the three and nine months ended September 30, 2017, respectively. Amounts billed by PHISCO to DPL and ACE were $1 million, each, for the nine months ended September 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and nine months ended September 30, 2016.

Severance Severance - Narrative

Severance Severance - Narrative (Details) $ in Millions		1 Months Ended		3 Months Ended				9 Months Ended
		Jun. 30, 2017USD ($)	Aug. 31, 2015	Sep. 30, 2017USD ($)		Sep. 30, 2016USD ($)		Sep. 30, 2017USD ($)		Sep. 30, 2016USD ($)
Restructuring Cost and Reserve [Line Items]
Severance Costs				$ 1		$ 8		$ 10		$ 12
Cost Management Project [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Expected Number of Positions Eliminated			500
Severance Costs				7	[1]	1	[2]	6	[1]	18	[2]
Facility Closing [Member] | Three Mile Island [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]			0		7		4		10
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				$ 7	[1]	1	[2]	6	[1]	13	[2]
Exelon Generation Co L L C [Member] | Facility Closing [Member] | Three Mile Island [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		$ 2		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
[1]	Amounts billed by BSC through intercompany allocations for the nine months ended September 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 nine months ended September 30, 2016.
[3]	The amounts above for Generation include $2 million for amounts billed by BSC through intercompany allocations for the nine months ended September 30, 2017 and $1 million and $2 million for the three and nine months ended September 30, 2016, respectively. The amounts above for ComEd include $1 million for amounts billed by BSC through intercompany allocations for the three and nine months ended September 30, 2016. The amounts above for PHI include less than $1 million and $1 million billed by BSC through intercompany allocations for the three and nine months ended September 30, 2017, respectively, and $1 million for the three and nine months ended September 30, 2016. Amounts billed by PHISCO to Pepco were $1 million and $2 million for the three and nine months ended September 30, 2017, respectively. Amounts billed by PHISCO to DPL and ACE were $1 million, each, for the nine months ended September 30, 2017. Pepco, DPL and ACE did not have any ongoing severance plans for the three and nine months ended September 30, 2016.

Mezzanine Equity Mezzanine Equi

Mezzanine Equity Mezzanine Equity (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Redeemable Noncontrolling Interest [Line Items]
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	$ 407
Preferred Stock, Shares Subscribed but Unissued, Value [Abstract]
Payments to Acquire Businesses, Gross	208	$ 6,896
Exelon Generation Co L L C [Member]
Redeemable Noncontrolling Interest [Line Items]
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	407
Preferred Stock, Shares Subscribed but Unissued, Value [Abstract]
Payments to Acquire Businesses, Gross	$ 208	$ 255

Changes in Accumulated Other102

Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Mar. 23, 2016	Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance							$ 27,612
Amounts reclassified from AOCI(b)	[1]	$ 34	$ 42				108		$ 114
Other comprehensive income		44	36				69		96
Ending balance		30,317					30,317
Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Amounts reclassified from AOCI(b)	[1]	(1)	7				3		10
Other comprehensive income		4	4				16		2
Gains and (losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			$ (19)			(17)		(19)
OCI before reclassifications	[2]						2		(9)
Amounts reclassified from AOCI(b)	[2],[3]						3		5
Other comprehensive income	[2]						5		(4)
Ending balance	[2]	(12)	(23)		$ (23)		(12)		(23)
Gains and (losses) on Cash Flow Hedges | Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			(21)			(19)		(21)
OCI before reclassifications	[2]						2		(8)
Amounts reclassified from AOCI(b)	[2],[3]						3	[4]	5
Other comprehensive income	[2]						5		(3)
Ending balance	[2]	(14)	(24)		(24)		(14)		(24)
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)	(8)	[5]			(8)
OCI before reclassifications	[2]			0
Amounts reclassified from AOCI(b)	[2],[3]			0
Other comprehensive income	[2]			0
Ending balance	[2],[5]			(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],[3]						0		0
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		1
Amounts reclassified from AOCI(b)	[2],[3]						0		0
Other comprehensive income	[2]						0		1
Ending balance	[2]	2	2		2		2		2
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	0	[5]			0
OCI before reclassifications	[2]			0
Amounts reclassified from AOCI(b)	[2],[3]			0
Other comprehensive income	[2]			0
Ending balance	[2],[5]			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]						(55)		(2)
Amounts reclassified from AOCI(b)	[1]	35	35				105	[2],[3]	104	[2],[3]
Other comprehensive income	[2]						50		102
Ending balance	[2]	(2,560)	(2,463)		(2,463)		(2,560)		(2,463)
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]			(28)	(27)	[5]			(28)
OCI before reclassifications	[2]			0
Amounts reclassified from AOCI(b)	[2],[3]			1
Other comprehensive income	[2]			1
Ending balance	[2],[5]			(27)
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			(40)			(30)		(40)
OCI before reclassifications	[2]						7		3
Amounts reclassified from AOCI(b)	[2],[3]						0		5
Other comprehensive income	[2]						7		8
Ending balance	[2]	(23)	(32)		(32)		(23)		(32)
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]						7		3
Amounts reclassified from AOCI(b)	[2],[3]						0		5
Other comprehensive income	[2]						7		8
Ending balance	[2]	(23)	(32)		(32)		(23)		(32)
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	0	[5]			0
OCI before reclassifications	[2]			0
Amounts reclassified from AOCI(b)	[2],[3]			0
Other comprehensive income	[2]			0
Ending balance	[2],[5]			0
AOCI of Equity Investments
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			(3)			(7)		(3)
OCI before reclassifications	[2]						7		(5)
Amounts reclassified from AOCI(b)	[2],[3]						0		0
Other comprehensive income	[2]						7		(5)
Ending balance	[2]	0	(8)		(8)		0		(8)
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		1
Amounts reclassified from AOCI(b)	[2],[3]						0		0
Other comprehensive income	[2]						6		1
Ending balance	[2]	(1)	(2)		(2)		(1)		(2)
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	0	[5]			0
OCI before reclassifications	[2]			0
Amounts reclassified from AOCI(b)	[2],[3]			0
Other comprehensive income	[2]			0
Ending balance	[2],[5]			0
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[2]			(2,624)			(2,660)		(2,624)
OCI before reclassifications	[2]						(37)		(13)
Amounts reclassified from AOCI(b)	[2],[3]						108		114
Other comprehensive income	[2]						71		101
Ending balance	[2]	(2,589)	(2,523)		(2,523)		(2,589)		(2,523)
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]						15		(3)
Amounts reclassified from AOCI(b)	[2],[3]						3		10
Other comprehensive income	[2]						18		7
Ending balance	[2]	(36)	(56)		(56)		(36)		(56)
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]			(36)	$ (35)	[5]			$ (36)
OCI before reclassifications	[2]			0
Amounts reclassified from AOCI(b)	[2],[3]			1
Other comprehensive income	[2]			1
Ending balance	[2],[5]			$ (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]	Amount is net of related income tax expense of $2 million for the nine months ended September 30, 2017.
[5]	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 Other103

Changes in Accumulated Other Comprehensive Income - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Mar. 23, 2016	Sep. 30, 2017		Sep. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other, net		$ 237	$ 120		$ 725		$ 377
Income Tax Expense (Benefit)		452	340		595		625
Amounts reclassified from AOCI	[1]	(34)	(42)		(108)		(114)
Net income		867	526		1,911		956
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other, net	[1]		(5)				(5)
Total before tax	[1]		(5)				(5)
Income Tax Expense (Benefit)	[1]		0				0
Net income	[1]		(5)				(5)
Gains and (losses) on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCI	[2],[3]				(3)		(5)
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		69		57
Actuarial losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of pension and other postretirement benefit plan items	[1],[4]	(81)	(76)		(243)		(227)
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)	(57)		(174)		(170)
Tax benefit	[1]	23	22		69		66
Amounts reclassified from AOCI	[1]	(35)	(35)		(105)	[2],[3]	(104)	[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			(2)		(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	[1]	2	(3)		(5)		(8)
Total before tax	[1]	2	(3)		(5)		(8)
Income Tax Expense (Benefit)	[1]	(1)	1		2		3
Net of tax	[1]	1	(2)		(3)		(5)
Exelon Generation Co L L C [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other, net		209	185		648		395
Income Tax Expense (Benefit)		240	173		209		293
Amounts reclassified from AOCI	[1]	1	(7)		(3)		(10)
Net income		348	271		491		556
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other, net	[1]		(5)				(5)
Total before tax	[1]		(5)				(5)
Income Tax Expense (Benefit)	[1]		0				0
Net income	[1]		(5)				(5)
Exelon Generation Co L L C [Member] | Gains and (losses) on Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amounts reclassified from AOCI	[2],[3]				(3)	[5]	(5)
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
Amounts reclassified from AOCI	[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	[1]	2	(3)		(5)		(8)
Total before tax	[1]	2	(3)		(5)		(8)
Income Tax Expense (Benefit)	[1]	(1)	1		2		3
Net of tax	[1]	$ 1	$ (2)		$ (3)		$ (5)
Pepco Holdings LLC [Member] | Predecessor [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other, net				$ (4)
Income Tax Expense (Benefit)				17
Amounts reclassified from AOCI	[1]			(1)
Net income				19
Pepco Holdings LLC [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Predecessor [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other, net	[1]			0
Total before tax	[1]			0
Income Tax Expense (Benefit)	[1]			0
Net income	[1]			0
Pepco Holdings LLC [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 LLC [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 LLC [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
Amounts reclassified from AOCI	[1]			(1)
Pepco Holdings LLC [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 14 — Retirement Benefits for additional details).
[5]	Amount is net of related income tax expense of $2 million for the nine months ended September 30, 2017.

Changes in Accumulated Other104

Changes in Accumulated Other Comprehensive Income - Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 23, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ (22)	$ (23)		$ (74)	$ (60)
Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	0	(2)		(6)	4
Prior service costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	9	7		27	22
Actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(32)	(29)		(96)	(88)
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	0	1		2	1
Gains and (losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	0	(1)		(3)	3
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	0	(2)		(3)	1
Unrealized Gains and (losses) on Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	0	(1)		(2)	(1)
Change in unrealized (loss)/gain on equity investments	1	0		(2)	3
Unrealized Gains and (losses) on Marketable Securities | Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	0	0		(1)	0
Change in unrealized (loss)/gain on equity investments	$ 0	$ 0		$ (2)	$ 3

Common Stock - Narrative (Detai

Common Stock - Narrative (Details) $ in Millions	Sep. 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		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 824	$ 490	$ 1,899	$ 930
Weighted average common shares outstanding — basic	962	925	941	924
Assumed exercise and/or distributions of stock-based awards	3	2	2	2
Weighted average common shares outstanding — diluted	965	927	943	926

Earnings Per Share and Equit107

Earnings Per Share and Equity - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jun. 01, 2017	Dec. 31, 2016
Statement Of Equity Line Item [Line Items]
Treasury Stock, Shares		1,832,457		1,832,457			34,743,157
Treasury Stock, Value		$ 123		$ 123		$ 2,300	$ 2,327
Equity units issued [Member]
Statement Of Equity Line Item [Line Items]
Stock options not included in the calculation of diluted common shares outstanding			1,000,000
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		7,000,000	11,000,000	9,000,000	12,000,000

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Equity Investment Commitments (Details) $ in Millions	Sep. 30, 2017USD ($)
Guarantor Obligations [Line Items]
Other Commitment	$ 2,879
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment	2,272
Equity Unit Purchase Agreements [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Other Commitment, Due in Next Twelve Months	12
Other Commitment, Due in Second Year	6
Other Commitment, Due in Third Year	3
Other Commitment	$ 21

Commitments and Contingencie109

Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Sep. 30, 2017USD ($)
Other Commitments [Line Items]
Other Commitment	$ 2,879
Guarantor Obligations, Maximum Exposure, Undiscounted	49
Financial Standby Letter of Credit [Member]
Other Commitments [Line Items]
Other Commitment	1,276	[1]
Guarantee of Indebtedness of Others [Member]
Other Commitments [Line Items]
Other Commitment	378
Surety Bond [Member]
Other Commitments [Line Items]
Other Commitment	1,206	[2]
Guarantee Obligations [Member]
Other Commitments [Line Items]
Other Commitment	19	[3]
Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Other Commitment	2,272
Exelon Generation Co L L C [Member] | Financial Standby Letter of Credit [Member]
Other Commitments [Line Items]
Other Commitment	1,193	[1]
Exelon Generation Co L L C [Member] | Guarantee of Indebtedness of Others [Member]
Other Commitments [Line Items]
Other Commitment	0
Exelon Generation Co L L C [Member] | Surety Bond [Member]
Other Commitments [Line Items]
Other Commitment	1,079	[2]
Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Other Commitment	234
Commonwealth Edison Co [Member] | Financial Standby Letter of Credit [Member]
Other Commitments [Line Items]
Other Commitment	14	[1]
Commonwealth Edison Co [Member] | Guarantee of Indebtedness of Others [Member]
Other Commitments [Line Items]
Other Commitment	200
Commonwealth Edison Co [Member] | Surety Bond [Member]
Other Commitments [Line Items]
Other Commitment	20	[2]
PECO Energy Co [Member]
Other Commitments [Line Items]
Other Commitment	240
PECO Energy Co [Member] | Financial Standby Letter of Credit [Member]
Other Commitments [Line Items]
Other Commitment	22	[1]
PECO Energy Co [Member] | Guarantee of Indebtedness of Others [Member]
Other Commitments [Line Items]
Other Commitment	178
PECO Energy Co [Member] | Surety Bond [Member]
Other Commitments [Line Items]
Other Commitment	40	[2]
Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	13
Baltimore Gas and Electric Company [Member] | Financial Standby Letter of Credit [Member]
Other Commitments [Line Items]
Other Commitment	2	[1]
Baltimore Gas and Electric Company [Member] | Guarantee of Indebtedness of Others [Member]
Other Commitments [Line Items]
Other Commitment	0
Baltimore Gas and Electric Company [Member] | Surety Bond [Member]
Other Commitments [Line Items]
Other Commitment	11	[2]
PEPCO Holdings Inc [Member]
Other Commitments [Line Items]
Other Commitment	41
PEPCO Holdings Inc [Member] | Financial Standby Letter of Credit [Member]
Other Commitments [Line Items]
Other Commitment	1	[1]
PEPCO Holdings Inc [Member] | Guarantee of Indebtedness of Others [Member]
Other Commitments [Line Items]
Other Commitment	0
PEPCO Holdings Inc [Member] | Surety Bond [Member]
Other Commitments [Line Items]
Other Commitment	21	[2]
PEPCO Holdings Inc [Member] | Guarantee Obligations [Member]
Other Commitments [Line Items]
Other Commitment	19	[3]
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	20
Guarantor Obligations, Maximum Exposure, Undiscounted	14
Potomac Electric Power Company [Member] | Financial Standby Letter of Credit [Member]
Other Commitments [Line Items]
Other Commitment	1	[1]
Potomac Electric Power Company [Member] | Guarantee of Indebtedness of Others [Member]
Other Commitments [Line Items]
Other Commitment	0
Potomac Electric Power Company [Member] | Surety Bond [Member]
Other Commitments [Line Items]
Other Commitment	13	[2]
Potomac Electric Power Company [Member] | Guarantee Obligations [Member]
Other Commitments [Line Items]
Other Commitment	6	[3]
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	11
Guarantor Obligations, Maximum Exposure, Undiscounted	19
Delmarva Power and Light Company [Member] | Financial Standby Letter of Credit [Member]
Other Commitments [Line Items]
Other Commitment	0	[1]
Delmarva Power and Light Company [Member] | Guarantee of Indebtedness of Others [Member]
Other Commitments [Line Items]
Other Commitment	0
Delmarva Power and Light Company [Member] | Surety Bond [Member]
Other Commitments [Line Items]
Other Commitment	4	[2]
Delmarva Power and Light Company [Member] | Guarantee Obligations [Member]
Other Commitments [Line Items]
Other Commitment	7	[3]
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	9
Guarantor Obligations, Maximum Exposure, Undiscounted	13
Atlantic City Electric Company [Member] | Financial Standby Letter of Credit [Member]
Other Commitments [Line Items]
Other Commitment	0	[1]
Atlantic City Electric Company [Member] | Guarantee of Indebtedness of Others [Member]
Other Commitments [Line Items]
Other Commitment	0
Atlantic City Electric Company [Member] | Surety Bond [Member]
Other Commitments [Line Items]
Other Commitment	4	[2]
Atlantic City Electric Company [Member] | Guarantee Obligations [Member]
Other Commitments [Line Items]
Other Commitment	$ 5	[3]
[1]	(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.
[2]	(b)Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds.
[3]	(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 $49 million, $14 million of which is a guarantee by Pepco, $19 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.

Commitments and Contingencie110

Commitments and Contingencies - Schedule of Accruals for Environmental Matters (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	$ 429	$ 429
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	76	72
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	294	292
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	33	33
Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	3	2
PEPCO Holdings Inc [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	23	30
Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	21	27
Delmarva Power and Light Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	1	2
Atlantic City Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	1	1
Accrual For MGP Investigation And Remediation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	327	325
Accrual For MGP Investigation And Remediation [Member] | Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	0	0
Accrual For MGP Investigation And Remediation [Member] | Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	293	291
Accrual For MGP Investigation And Remediation [Member] | PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	32	31
Accrual For MGP Investigation And Remediation [Member] | Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	2	2
Accrual For MGP Investigation And Remediation [Member] | PEPCO Holdings Inc [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	0	1
Accrual For MGP Investigation And Remediation [Member] | Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	0	0
Accrual For MGP Investigation And Remediation [Member] | Delmarva Power and Light Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	0	1
Accrual For MGP Investigation And Remediation [Member] | Atlantic City Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	$ 0	$ 0

Commitments and Contingencie111

Commitments and Contingencies - Narrative (Details)	1 Months Ended			3 Months Ended		9 Months Ended	12 Months Ended
	Nov. 30, 2015USD ($)	Sep. 23, 2015USD ($)	Aug. 31, 2015gal	Sep. 30, 2017USD ($)MGPSitegal	Dec. 31, 2016USD ($)Open_claim	Sep. 30, 2017USD ($)MGPSiteOpen_claimgalMW	Dec. 31, 2016USD ($)Open_claim	Nov. 29, 2016employee	Jun. 30, 2014USD ($)
Commitments And Contingencies Additional Narrative Information [Line Items]
Commitments and Contingencies									$ 1,000,000,000
BusinessAcquisitionResidualcommitment | MW						55
Guarantor Obligations, Maximum Exposure, Undiscounted				$ 49,000,000		$ 49,000,000
Loss Contingency, Loss in Period						$ 50,000,000
Power Volume | MW						220
Open Asbestos Related Personal Injury Claims | Open_claim					227		227
PEPCO Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Environmental Remediation Expense						$ 10,000,000
Number of Real Estate Properties | MGPSite				9		9
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Consent Decree Penalty						$ 1,600,000
Payments for Legal Settlements						1,600,000
Commitments and Contingencies
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				360,000,000		360,000,000
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
Entity Number of Employees | employee								1,500
Leasehold Improvements, Gross					110,000,000		110,000,000
Costs Incurred, Development Costs				457,000,000
Accrual for Environmental Loss Contingencies, Component Amount				90,000,000		90,000,000
Liability for Asbestos and Environmental Claims, Gross				80,000,000	83,000,000	80,000,000	83,000,000
Liability for Asbestos and Environmental Claims, Net				22,000,000		22,000,000
Liability for Asbestos and Environmental Claims, Net, Payment for Claims				58,000,000
Loss Contingency, Damages Sought, Value							14,000,000
Commonwealth Edison Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Increase (Decrease) in Environmental Liabilities				13,000,000
Commitments and Contingencies
Mgp Site Contingency Approved Cleanup Count | MGPSite				42		42
Mgp Site Contingency Count | MGPSite				19		19
Mgp Site Contingency Monitoring Count | MGPSite				23		23
Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted				$ 14,000,000		$ 14,000,000
QuantityOfMineralOilSPill | gal			6,100
PECO Energy Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Increase (Decrease) in Environmental Liabilities				2,000,000
Commitments and Contingencies
Mgp Site Contingency Approved Cleanup Count | MGPSite				26		26
Mgp Site Contingency Count | MGPSite				17		17
Mgp Site Contingency Monitoring Count | MGPSite				9		9
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
Mgp Site Contingency Approved Cleanup Count | MGPSite				13		13
Mgp Site Contingency Monitoring Count | MGPSite				2		2
Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted				$ 19,000,000		$ 19,000,000
Mgp Site Contingency Approved Cleanup Count | gal				3		3
Mgp Site Contingency Count | MGPSite				2		2
Maximum [Member] | PEPCO Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Loss Contingency, Estimate of Possible Loss				$ 18,000,000		$ 18,000,000
Maximum [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Loss Contingency, New Claims Filed, Number | Open_claim						650,000,000
Maximum [Member] | Calpine Corporation [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Loss Contingency, Estimate of Possible Loss				10,000,000		$ 10,000,000
Maximum [Member] | Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Environmental Exit Costs, Anticipated Cost						6,000,000
Minimum [Member] | PEPCO Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Loss Contingency, Estimate of Possible Loss				7,000,000		$ 7,000,000
Minimum [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Loss Contingency, New Claims Filed, Number | Open_claim						225,000,000
Minimum [Member] | Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Environmental Exit Costs, Anticipated Cost						$ 3,000,000
Nuclear Plant [Member] | Maximum [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Commitments and Contingencies				500,000,000		500,000,000
Nuclear Plant [Member] | Minimum [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Commitments and Contingencies				450,000,000		450,000,000
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				400,000,000		400,000,000
Rossville Ash Site [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Loss Contingency, Estimate of Possible Loss				$ 1,000,000		$ 1,000,000

Supplemental Financial Infor112

Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016		Mar. 23, 2016	Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	$ 159	$ 57	[1]			$ 439		$ 181	[1]
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	59	35	[1]			165		95	[1]
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units	44	155				253		286
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement	111	116				347		216
Net unrealized income (losses) on pledged assets	(4)	(5)				(5)		(2)
Regulatory offset to decommissioning trust fund-related activities	(161)	(168)	[2]			(558)		(380)	[2]
Total decommissioning-related activities	208	190				641		396
Investment income	2	2				6		14
Long-term lease income								4
Unrecognized Tax Benefits Interest Income	(4)	(8)				(3)		(13)
Income Tax Examination, Penalties and Interest Expense		106				(2)		106
AFUDC - equity	17	19				51		43
Gains (Losses) on Extinguishment of Debt								(3)
Other Income	6	7				22		16
Other, net	237	120				725		377
Exelon Generation Co L L C [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	159	57	[1]			439	[1]	181	[1]
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	59	35	[1]			165	[1]	95	[1]
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units	44	155				253		286
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement	111	116				347		216
Net unrealized income (losses) on pledged assets	(4)	(5)				(5)		(2)
Regulatory offset to decommissioning trust fund-related activities	(161)	(168)	[2]			(558)	[2]	(380)	[2]
Total decommissioning-related activities	208	190				641		396
Investment income	1	1				4		6
Long-term lease income								0
Unrecognized Tax Benefits Interest Income	0	0				0		0
Income Tax Examination, Penalties and Interest Expense		0				0		0
Gains (Losses) on Extinguishment of Debt								(2)
Other Income	0	(6)				3		(5)
Other, net	209	185				648		395
Commonwealth Edison Co [Member]
Decommissioning-Related Activities [Abstract]
Investment income	0	0				0		0
Long-term lease income								0
Unrecognized Tax Benefits Interest Income	0	0				0		0
Income Tax Examination, Penalties and Interest Expense		(86)				0		86
AFUDC - equity	2	5				6		8
Other Income	3	1				8		6
Other, net	5	(80)				14		(72)
PECO Energy Co [Member]
Decommissioning-Related Activities [Abstract]
Investment income	0	(1)				0		(1)
Long-term lease income								0
Unrecognized Tax Benefits Interest Income	0	0				0		0
Income Tax Examination, Penalties and Interest Expense		0				0
AFUDC - equity	2	2				6		6
Other Income	0	1				0		1
Other, net	2	2				6		6
Baltimore Gas and Electric Company [Member]
Decommissioning-Related Activities [Abstract]
Investment income	0	0				0		2
Long-term lease income								0
Unrecognized Tax Benefits Interest Income	0	0				0		0
Income Tax Examination, Penalties and Interest Expense		0				0
AFUDC - equity	4	5				12		14
Other Income	0	0				0		0
Other, net	4	5				12		16
Pepco Holdings LLC [Member] | Successor [Member]
Decommissioning-Related Activities [Abstract]
Investment income		0			$ 1	2
Long-term lease income					0
Unrecognized Tax Benefits Interest Income	0	0			0	0
Income Tax Examination, Penalties and Interest Expense		0				0
AFUDC - equity	9				15	27
Other Income	3				15	11
Other, net	13	19			$ 31	40
Pepco Holdings LLC [Member] | Predecessor [Member]
Decommissioning-Related Activities [Abstract]
Investment income				$ 0
Long-term lease income				0
Unrecognized Tax Benefits Interest Income				0
AFUDC - equity				7
Other Income				(11)
Other, net				$ (4)
Potomac Electric Power Company [Member]
Decommissioning-Related Activities [Abstract]
Investment income	1	0				1		0
Long-term lease income								0
Unrecognized Tax Benefits Interest Income	0	0				0		1
Income Tax Examination, Penalties and Interest Expense		0				0
AFUDC - equity	6	5				17		14
Other Income	0	7				4		13
Other, net	7	12				22		28
Delmarva Power and Light Company [Member]
Decommissioning-Related Activities [Abstract]
Investment income	0	0				0		0
Long-term lease income								0
Unrecognized Tax Benefits Interest Income	0	0				0		0
Income Tax Examination, Penalties and Interest Expense		0				0
AFUDC - equity	2	1				5		3
Other Income	2	2				5		6
Other, net	4	3				10		9
Atlantic City Electric Company [Member]
Decommissioning-Related Activities [Abstract]
Investment income	0	0				0		0
Long-term lease income								0
Unrecognized Tax Benefits Interest Income	0	0				0		1
Income Tax Examination, Penalties and Interest Expense		0				0
AFUDC - equity	1	1				5		5
Other Income	0	1				1		2
Other, net	$ 1	$ 2				$ 6		$ 8
[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 Infor113

Supplemental Financial Information Supplemental Financial Information - Utility Taxes (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Mar. 23, 2016	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	$ 245	$ 255			$ 682	$ 624
Exelon Generation Co L L C [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	35	35			97	90
Commonwealth Edison Co [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	65	67			181	186
PECO Energy Co [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	35	40			95	106
Baltimore Gas and Electric Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	22	21			69	66
Pepco Holdings LLC [Member] | Successor [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	88	92		$ 176	240
Pepco Holdings LLC [Member] | Predecessor [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes			$ 78
Potomac Electric Power Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	83	87			226	240
Delmarva Power and Light Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	5	5			14	14
Atlantic City Electric Company [Member]
Supplemental Income Statement Information [Line Items]
Utilities Operating Expense, Taxes	$ 0	$ 0			$ 0	$ 0

Supplemental Financial Infor114

Supplemental Financial Information - Cash Flow (Details) - USD ($) $ in Millions		3 Months Ended					6 Months Ended		9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016		Mar. 23, 2016	Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								$ 2,416		$ 2,490
Regulatory assets	[1]								355		293
Amortization of intangible assets, net	[1]								43		38
Amortization of Power Contracts Emission Credits	[2]								19		(7)
Amortization of Nuclear Fuel Lease	[3]								816		862
Asset Retirement Obligation, Accretion Expense	[4]								350		333
Total depreciation, amortization and accretion									3,999		4,009
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		$ 161		$ 161					482		458
Gain (loss) on equity method investments									26		15
Provision for uncollectible accounts									103		107
Stock-based compensation costs									76		88
Other Decommissioning Related Activity	[5]								(213)		(237)
Energy-related options	[6]								15		(20)
Amortization of regulatory asset related to debt costs									7		7
Amortization of rate stabilization deferral									(7)		62
Amortization of debt fair value adjustment									(13)		(9)
Discrete impacts from EIMA	[7]								(61)		(36)
Amortization of debt costs									57		26
Inventory Write-down									52		74
Merger related commitments									0	[8],[9]	508
Restructuring Costs									33		130
Asset Retirement Obligation, Revision of Estimate											0
InventoryLCMReservePeriodCharge											36
Other									46		15
Total other noncash operating activities									603		1,224
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									(101)		(338)
Non cash Fair Value Adjustment for CENG											0
Business Combination, Contingent Consideration, Liability, Noncurrent		0							0
Payments to Acquire Businesses, Gross									208		6,896
Capitalized Costs, Asset Retirement Costs		(141)		476			$ 476		(141)		476
Contribution of Property	[10]								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									16		84
Stock Issued									5		2
Non Cash Licensing Agreement									8
Exelon Generation Co L L C [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								1,010		1,297
Amortization of intangible assets, net	[1]								36		32
Amortization of Power Contracts Emission Credits	[2]								19		(7)
Amortization of Nuclear Fuel Lease	[3]								816		862
Asset Retirement Obligation, Accretion Expense	[4]								350		332
Total depreciation, amortization and accretion									2,231		2,516
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		57	[11]	54					170	[11]	163
Gain (loss) on equity method investments									26		16
Provision for uncollectible accounts									31		14
Stock-based compensation costs									0		0
Other Decommissioning Related Activity	[5]								(213)		(237)
Energy-related options	[6]								15		(20)
Amortization of regulatory asset related to debt costs									0		0
Amortization of rate stabilization deferral									0		0
Amortization of debt fair value adjustment									(9)		(9)
Discrete impacts from EIMA									0		0
Amortization of debt costs									33		12
Inventory Write-down									50		70
Merger related commitments									0	[9]	3
Restructuring Costs									25		57
Asset Retirement Obligation, Revision of Estimate											0
InventoryLCMReservePeriodCharge											36
Other									4		24
Total other noncash operating activities									132		129
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									20		(289)
Non cash Fair Value Adjustment for CENG											119
Business Combination, Contingent Consideration, Liability, Noncurrent		33							33
Payments to Acquire Businesses, Gross									208		255
Capitalized Costs, Asset Retirement Costs				476			476				476
Contribution of Property	[10]								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									16		84
Stock Issued									0		0
Commonwealth Edison Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								579		524
Regulatory assets	[1]								52		49
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		1
Total depreciation, amortization and accretion									631		574
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		44		41					131		124
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									25		31
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									3		3
Amortization of rate stabilization deferral									0		0
Amortization of debt fair value adjustment									0		0
Discrete impacts from EIMA	[7]								(61)		(36)
Amortization of debt costs									3		(3)
Inventory Write-down									1		4
Merger related commitments									0	[9]	0
Restructuring Costs									0		0
Asset Retirement Obligation, Revision of Estimate											0
InventoryLCMReservePeriodCharge											0
Other									10		(1)
Total other noncash operating activities									112		122
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									(79)		(42)
Non cash Fair Value Adjustment for CENG											0
Business Combination, Contingent Consideration, Liability, Noncurrent		0							0
Capitalized Costs, Asset Retirement Costs		0		0			0		0		0
Contribution of Property	[10]								21		157
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									0		0
Stock Issued									0		0
PECO Energy Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								194		181
Regulatory assets	[1]								19		20
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									213		201
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		7		8					21		25
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									17		24
Stock-based compensation costs									0		0
Other Decommissioning Related Activity									0		0
Energy-related options									0		0
Amortization of regulatory asset related to debt costs									1		1
Amortization of rate stabilization deferral									0		0
Amortization of debt fair value adjustment									0		0
Discrete impacts from EIMA									0		0
Amortization of debt costs									1		2
Inventory Write-down									0		0
Merger related commitments									0	[9]	0
Restructuring Costs									0		0
Asset Retirement Obligation, Revision of Estimate											0
InventoryLCMReservePeriodCharge											0
Other									(2)		(3)
Total other noncash operating activities									38		49
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									(29)		(4)
Non cash Fair Value Adjustment for CENG											0
Business Combination, Contingent Consideration, Liability, Noncurrent		0							0
Capitalized Costs, Asset Retirement Costs		0		0			0		0		0
Contribution of Property	[10]								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									0		0
Stock Issued									0		0
Baltimore Gas and Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								233		223
Regulatory assets	[1]								115		84
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									0		0	[4]
Total depreciation, amortization and accretion									348		307
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		16		17					47		50
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									4		12
Stock-based compensation costs									0		0
Other Decommissioning Related Activity									0		0
Energy-related options									0		0
Amortization of regulatory asset related to debt costs									0		0
Amortization of rate stabilization deferral									7		62
Amortization of debt fair value adjustment									0		0
Discrete impacts from EIMA									0		0
Amortization of debt costs									1		3
Inventory Write-down									0		0
Merger related commitments									0	[9]	0
Restructuring Costs									0		0
Asset Retirement Obligation, Revision of Estimate											0
InventoryLCMReservePeriodCharge											0
Other									(7)		(18)
Total other noncash operating activities									52		109
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									16		17
Non cash Fair Value Adjustment for CENG											0
Business Combination, Contingent Consideration, Liability, Noncurrent		0							0
Capitalized Costs, Asset Retirement Costs		0		0			0		0		0
Contribution of Property	[10]								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									0		0
Stock Issued									0		0
Potomac Electric Power Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								153		128
Regulatory assets	[1]								89		93
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									242		221
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		6	[12]	8	[12]	$ 7			19	[12]	24	[12]
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									11		15
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									(12)		3
Amortization of debt fair value adjustment									0		0
Discrete impacts from EIMA									0		0
Amortization of debt costs									1		0
Inventory Write-down									0		1
Merger related commitments									(6)	[9]	125
Restructuring Costs									0		0
Asset Retirement Obligation, Revision of Estimate											0
InventoryLCMReservePeriodCharge											0
Other									(6)		(2)
Total other noncash operating activities									8		168
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									(7)		15
Non cash Fair Value Adjustment for CENG											0
Business Combination, Contingent Consideration, Liability, Noncurrent		0							0
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed											33
Capitalized Costs, Asset Retirement Costs				0			0				0
Contribution of Property	[10]								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									0		0
Stock Issued									0		0
Delmarva Power and Light Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								92		82
Regulatory assets	[1]								32		38
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									124		120
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		3	[12]	4	[12]	4			10	[12]	13	[12]
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									1		12
Stock-based compensation costs									0		0
Other Decommissioning Related Activity									0		0
Energy-related options									0		0
Amortization of regulatory asset related to debt costs									1		0
Amortization of rate stabilization deferral									(2)		3
Amortization of debt fair value adjustment									0		0
Discrete impacts from EIMA									0		0
Amortization of debt costs									0		0
Inventory Write-down									1		1
Merger related commitments									(2)	[9]	73
Restructuring Costs									0		0
Asset Retirement Obligation, Revision of Estimate											5
InventoryLCMReservePeriodCharge											0
Other									(3)		(8)
Total other noncash operating activities									6		99
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									14		(10)
Non cash Fair Value Adjustment for CENG											0
Business Combination, Contingent Consideration, Liability, Noncurrent		0							0
Capitalized Costs, Asset Retirement Costs				0			0				0
Contribution of Property	[10]								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									0		0
Stock Issued									0		0
Atlantic City Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation	[1]								66		61
Regulatory assets	[1]								47		69
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									113		130
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		3	[12]	4	[12]	3			10	[12]	11	[12]
Gain (loss) on equity method investments									0		0
Provision for uncollectible accounts									14		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									1		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									0		0
Inventory Write-down									0		1
Merger related commitments									0	[9]	110
Restructuring Costs									0		0
Asset Retirement Obligation, Revision of Estimate											2
InventoryLCMReservePeriodCharge											0
Other									(4)		(5)
Total other noncash operating activities									21		138
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid									(18)		2
Non cash Fair Value Adjustment for CENG											0
Business Combination, Contingent Consideration, Liability, Noncurrent		0							0
Capitalized Costs, Asset Retirement Costs				0			0				0
Contribution of Property	[10]								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									0		0
Stock Issued									0		0
Pepco Holdings LLC [Member] | Successor [Member]
Depreciation, Amortization and Accretion [Abstract]
Depreciation							215	[1]	342
Regulatory assets							140	[1]	169
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							355		511
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)		24		28			58		72
Gain (loss) on equity method investments									0
Provision for uncollectible accounts							27		26
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		3
Amortization of rate stabilization deferral							0		(14)
Amortization of debt fair value adjustment							0		(4)
Discrete impacts from EIMA							0		0
Amortization of debt costs							0		1
Inventory Write-down							0		1
Merger related commitments							308		(8)	[9]
Restructuring Costs							53		3
Other							(7)		(14)
Total other noncash operating activities							441		66
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid							(5)		(6)
Business Combination, Contingent Consideration, Liability, Noncurrent		$ 0		$ 53			53		0		53
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed							33
Contribution of Property	[10]								0
Noncash or Part Noncash Acquisition, Fixed Assets Acquired									0		0
Stock Issued									$ 0		0
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)						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
Noncash or Part Noncash Acquisition, Fixed Assets Acquired											0
Stock Issued											$ 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							$ 129
[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]	See Note 12— Income Taxes for discussion of the like-kind exchange tax position
[11]	FitzPatrick net benefit costs are included for the period after acquisition.
[12]	Pepco's, DPL's, ACE's and PHISCO's pension and postretirement benefit costs for the nine months ended September 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 Infor115

Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2017		Dec. 31, 2016
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	$ 20,591	[1]	$ 19,169	[2]
Accounts receivable, net
Allowance for uncollectible accounts	339		334
Exelon Generation Co L L C [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	11,193	[1]	10,562	[2]
Accounts receivable, net
Allowance for uncollectible accounts	111		91
Exelon Generation Co L L C [Member] | Nuclear Fuel [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,303		3,186
Commonwealth Edison Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	4,191		3,937
Accounts receivable, net
Allowance for uncollectible accounts	72		70
PECO Energy Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,366		3,253
Accounts receivable, net
Allowance for uncollectible accounts	57		61
Baltimore Gas and Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,351		3,254
Accounts receivable, net
Allowance for uncollectible accounts	25		32
Pepco Holdings LLC [Member] | Successor [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	448		195
Accounts receivable, net
Allowance for uncollectible accounts	74		80
Potomac Electric Power Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,171		3,050
Accounts receivable, net
Allowance for uncollectible accounts	29		29
Delmarva Power and Light Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	1,231		1,175
Accounts receivable, net
Allowance for uncollectible accounts	17		24
Atlantic City Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	1,060		1,016
Accounts receivable, net
Allowance for uncollectible accounts	$ 28		$ 27
[1]	Includes accumulated amortization of nuclear fuel in the reactor core of $3,303 million
[2]	Includes accumulated amortization of nuclear fuel in the reactor core of $3,186 million

Supplemental Financial Infor116

Supplemental Financial Information - Narrative (Details) - PECO Energy Co [Member] - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net	$ 11	$ 9
Financing Receivable, Allowance for Credit Losses	12	13
Low To Medium Risk [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses		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)	9 Months Ended
	Sep. 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		9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016		Mar. 23, 2016	Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016		Dec. 31, 2016
Segment Reporting Information [Line Items]
Competitive businesses electric revenues		$ 3,747	[1]	$ 3,823	[1]				$ 10,597	[2]	$ 10,559	[2]
Competitive businesses natural gas revenues		460	[1]	326	[1]				1,807	[2]	1,515	[2]
Competitive businesses other revenues		249	[1]	386	[1]				520	[2]	169	[2]
Rate-regulated electric revenues		4,164	[1]	4,330	[1]				11,318	[2]	10,461	[2]
Rate-regulated natural gas revenues		149	[1]	137	[1]				906	[2]	781	[2]
Shared service and other revenues		0	[1]	0	[1]				1	[2]	1	[2]
Operating revenues from affiliates		0	[3]	1	[3]				2	[4]	3	[4]
Net income (loss)		867		526					1,911		956
Assets		118,473							118,473				$ 114,904
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		296		502					894		1,129
Net income (loss)		348		271					491		556
Assets		47,744							47,744				46,974
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive businesses electric revenues		(295)	[1]	(499)	[1]				(888)	[2]	(1,118)	[2]
Competitive businesses natural gas revenues		0	[1]	0	[1]				0	[2]	0	[2]
Competitive businesses other revenues		0	[1]	(1)	[1]				0	[2]	(2)	[2]
Rate-regulated electric revenues		(7)	[1]	(8)	[1]				(23)	[2]	(24)	[2]
Rate-regulated natural gas revenues		(2)	[1]	(5)	[1]				(6)	[2]	(10)	[2]
Shared service and other revenues		(458)	[1]	(373)	[1]				(1,350)	[2]	(1,199)	[2]
Operating revenues from affiliates		(759)	[3]	(885)	[3]				(2,262)	[4]	(2,351)	[4]
Net income (loss)		0		(1)					(2)		(3)
Assets		(11,286)							(11,286)				(11,334)
Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Rate-regulated electric revenues		(3)	[5]	(4)	[5]		$ (9)	[6]	(13)	[6]
Rate-regulated natural gas revenues		0	[5]	0	[5]		0	[6]	0	[6]
Shared service and other revenues		0	[5]	0	[5]		0	[6]	(2)	[6]
Operating revenues from affiliates		(4)		(4)			(9)		(14)
Net income (loss)		12		11			34		35
Assets		(4,984)							(4,984)				(4,724)
Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Rate-regulated electric revenues	[6]					$ (4)
Rate-regulated natural gas revenues	[6]					0
Shared service and other revenues	[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 businesses electric revenues		4,042	[1],[7]	4,322	[1],[7]				11,485	[2],[8]	11,677	[2],[8]
Competitive businesses natural gas revenues		460	[1],[7]	326	[1],[7]				1,807	[2],[8]	1,515	[2],[8]
Competitive businesses other revenues		249	[1],[7]	387	[1],[7]				520	[2],[8]	171	[2],[8]
Rate-regulated electric revenues		0	[1],[7]	0	[1],[7]				0	[2],[8]	0	[2],[8]
Rate-regulated natural gas revenues		0	[1],[7]	0	[1],[7]				0	[2],[8]	0	[2],[8]
Shared service and other revenues		0	[1],[7]	0	[1],[7]				0	[2],[8]	0	[2],[8]
Net income (loss)		348	[7]	271	[7]				491	[8]	556	[8]
Assets	[7]	47,744							47,744				46,974
Exelon Generation Co L L C [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		294	[3],[7]	500	[3],[7]				888	[4],[8]	1,121	[4],[8]
Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses electric revenues		0	[1]	0	[1]				0	[2]	0	[2]
Competitive businesses natural gas revenues		0	[1]	0	[1]				0	[2]	0	[2]
Competitive businesses other revenues		0	[1]	0	[1]				0	[2]	0	[2]
Rate-regulated electric revenues		1,571	[1]	1,497	[1]				4,227	[2]	4,031	[2]
Rate-regulated natural gas revenues		0	[1]	0	[1]				0	[2]	0	[2]
Shared service and other revenues		0	[1]	0	[1]				0	[2]	0	[2]
Net income (loss)		189		37					447		297
Assets		29,649							29,649				28,335
Commonwealth Edison Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		3	[3]	4	[3]				12	[4]	12	[4]
PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses electric revenues		0	[1]	0	[1]				0	[2]	0	[2]
Competitive businesses natural gas revenues		0	[1]	0	[1]				0	[2]	0	[2]
Competitive businesses other revenues		0	[1]	0	[1]				0	[2]	0	[2]
Rate-regulated electric revenues		662	[1]	740	[1]				1,802	[2]	1,971	[2]
Rate-regulated natural gas revenues		53	[1]	48	[1]				339	[2]	322	[2]
Shared service and other revenues		0	[1]	0	[1]				0	[2]	0	[2]
Net income (loss)		112		122					327		346
Assets		11,480							11,480				10,831
PECO Energy Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		2	[3]	2	[3]				5	[4]	5	[4]
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses electric revenues		0	[1]	0	[1]				0	[2]	0	[2]
Competitive businesses natural gas revenues		0	[1]	0	[1]				0	[2]	0	[2]
Competitive businesses other revenues		0	[1]	0	[1]				0	[2]	0	[2]
Rate-regulated electric revenues		658	[1]	735	[1]				1,895	[2]	1,998	[2]
Rate-regulated natural gas revenues		80	[1]	77	[1]				468	[2]	423	[2]
Shared service and other revenues		0	[1]	0	[1]				0	[2]	0	[2]
Net income (loss)		62		56					231		191
Assets		8,923							8,923				8,704
Baltimore Gas and Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		3	[3]	7	[3]				12	[4]	16	[4]
Pepco Holdings LLC [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Competitive businesses electric revenues		0	[1],[9]	0	[1],[9]				0	[2],[10]	0	[2],[10]
Competitive businesses natural gas revenues		0	[1],[9]	0	[1],[9]				0	[2],[10]	0	[2],[10]
Competitive businesses other revenues		0	[1],[9]	0	[1],[9]				0	[2],[10]	0	[2],[10]
Rate-regulated electric revenues		1,280	[1],[5],[9]	1,366	[1],[5],[9]		2,485	[6]	3,417	[2],[6],[10]	2,485	[2],[10]
Rate-regulated natural gas revenues		18	[1],[5],[9]	17	[1],[5],[9]		46	[6]	105	[2],[6],[10]	46	[2],[10]
Shared service and other revenues		12	[1],[5],[9]	11	[1],[5],[9]		34	[6]	35	[2],[6],[10]	34	[2],[10]
Net income (loss)		153	[9]	166	[9]		(91)		359	[10]	(91)	[10]
Assets	[9]	21,301							21,301				21,025
Pepco Holdings LLC [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Rate-regulated electric revenues	[6]					1,096
Rate-regulated natural gas revenues	[6]					57
Shared service and other revenues	[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]	11	[3],[9]		34		35	[4],[10]	34	[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]
Rate-regulated electric revenues		604	[5]	635	[5]		1,184	[6]	1,649	[6]
Rate-regulated natural gas revenues		0	[5]	0	[5]		0	[6]	0	[6]
Shared service and other revenues		0	[5]	0	[5]		0	[6]	0	[6]
Net income (loss)		87		79			(12)		188
Assets		7,775							7,775				7,335
Potomac Electric Power Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Rate-regulated electric revenues	[6]					511
Rate-regulated natural gas revenues	[6]					0
Shared service and other revenues	[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		4
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]
Rate-regulated electric revenues		309	[5]	314	[5]		593	[6]	866	[6]
Rate-regulated natural gas revenues		18	[5]	17	[5]		46	[6]	105	[6]
Shared service and other revenues		0	[5]	0	[5]		0	[6]	0	[6]
Net income (loss)		31		44			(42)		107
Assets		4,276							4,276				4,153
Delmarva Power and Light Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Rate-regulated electric revenues	[6]					279
Rate-regulated natural gas revenues	[6]					56
Shared service and other revenues	[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			4		6
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]
Rate-regulated electric revenues		370	[5]	421	[5]		714	[6]	915	[6]
Rate-regulated natural gas revenues		0	[5]	0	[5]		0	[6]	0	[6]
Shared service and other revenues		0	[5]	0	[5]		0	[6]	0	[6]
Net income (loss)		41		47			(55)		77
Assets		3,510							3,510				3,457
Atlantic City Electric Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Rate-regulated electric revenues	[6]					268
Rate-regulated natural gas revenues	[6]					0
Shared service and other revenues	[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		0		1			2		2
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 businesses electric revenues		0	[1],[11]	0	[1],[11]				0	[2],[12]	0	[2],[12]
Competitive businesses natural gas revenues		0	[1],[11]	0	[1],[11]				0	[2],[12]	0	[2],[12]
Competitive businesses other revenues		0	[1],[11]	0	[1],[11]				0	[2],[12]	0	[2],[12]
Rate-regulated electric revenues		0	[1],[11]	0	[1],[11]				0	[2],[12]	0	[2],[12]
Rate-regulated natural gas revenues		0	[1],[11]	0	[1],[11]				0	[2],[12]	0	[2],[12]
Shared service and other revenues		446	[1],[11]	362	[1],[11]				1,316	[2],[12]	1,166	[2],[12]
Net income (loss)		3	[11]	(125)	[11]				58	[12]	(340)	[12]
Assets	[11]	10,662							10,662				10,369
Corporate and Other [Member] | Corporate, Non-Segment [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Rate-regulated electric revenues		0	[5],[13]	0	[5],[13]		3	[6],[14]	0	[6],[14]
Rate-regulated natural gas revenues		0	[5],[13]	0	[5],[13]		0	[6],[14]	0	[6],[14]
Shared service and other revenues		12	[5],[13]	11	[5],[13]		34	[6],[14]	37	[6],[14]
Net income (loss)		(18)	[13]	(15)	[13]		(16)	[14]	(48)	[14]
Assets	[13]	10,724							10,724				$ 10,804
Corporate and Other [Member] | Corporate, Non-Segment [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Rate-regulated electric revenues	[6],[14]					42
Rate-regulated natural gas revenues	[6],[14]					1
Shared service and other revenues	[6],[14]					0
Net income (loss)	[14]					(44)
Corporate and Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		445	[3],[11]	362	[3],[11]				1,312	[4],[12]	1,166	[4],[12]
Corporate and Other [Member] | Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		13	[13]	11	[13]		35	[14]	37	[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		31		91					111		234
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		98		183					330		489
Generation Mid Atlantic [Member] | PotomacElectricPowerCompanyAffiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		57		128			223		209
Generation Mid Atlantic [Member] | DelmarvaPowerandLightCompanyAffiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		47		63			109		138
Generation Mid Atlantic [Member] | AtlanticCityElectricCompanyAffiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		7		15			$ 28		23
Generation Mid Atlantic [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		11		(13)					15		(40)
Generation Midwest [Member] | Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		54		20					77		38
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		$ (11)		$ 1					$ (17)		$ 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 19 — Supplemental Financial Information for total utility taxes for the three months ended September 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 19 — Supplemental Financial Information for total utility taxes for the nine months ended September 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 19 — Supplemental Financial Information for total utility taxes for the three months ended September 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 19 — Supplemental Financial Information for total utility taxes for the nine months ended September 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 September 30, 2017 include revenue from sales to PECO of $31 million, sales to BGE of $98 million, sales to Pepco of $57 million, sales to DPL of $47 million, and sales to ACE of $7 million in the Mid-Atlantic region, and sales to ComEd of $54 million in the Midwest region. For the three months ended September 30, 2016, intersegment revenues for Generation include revenue from sales to PECO of $91 million, sales to BGE of $183 million, sales to Pepco of $128 million, sales to DPL of $63 million, and sales to ACE of $15 million in the Mid-Atlantic region, and sales to ComEd of $20 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 nine months ended September 30, 2017 include revenue from sales to PECO of $111 million, sales to BGE of $330 million, sales to Pepco of $209 million, sales to DPL of $138 million, and sales to ACE of $23 million in the Mid-Atlantic region, and sales to ComEd of $77 million in the Midwest region. For the nine months ended September 30, 2016, intersegment revenues for Generation include revenue from sales to PECO of $234 million and sales to BGE of $489 million in the Mid-Atlantic region, and sales to ComEd of $38 million in the Midwest region. For the Successor period of March 24, 2016 to September 30, 2016, intersegment revenues for Generation include revenue from sales to Pepco of $223 million, sales to DPL of $109 million, and sales to ACE of $28 million in the Mid-Atlantic region.
[9]	Amounts included represent activity for PHI's successor period, three months ended September 30, 2017 and 2016. PHI includes the three reportable segments: Pepco, DPL and ACE.
[10]	Amounts included represent activity for PHI's successor period, nine months ended September 30, 2017 and March 24, 2016 through September 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				9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 8,769		$ 9,002		$ 25,149		$ 23,486
Operating revenues from affiliates	0	[1]	1	[1]	2	[2]	3	[2]
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,432		1,800		4,222		4,736
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,038		1,164		3,141		3,343
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	481		451		1,461		1,272
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	428		323		1,081		873
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	314		295		753		665
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	335		238		779		686
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,028		4,271		11,437		11,575
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	723	[3]	764	[3]	2,375	[4]	1,788	[4]
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,751		5,035		13,812		13,363
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,421	[5]	1,813	[5]	4,207	[6]	4,776	[6]
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,049	[5]	1,163	[5]	3,158	[6]	3,330	[6]
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	482	[5]	455	[5]	1,469	[6]	1,278	[6]
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	434	[5]	331	[5]	1,095	[6]	906	[6]
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	308	[5]	289	[5]	749	[6]	659	[6]
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	348	[5]	271	[5]	807	[6]	728	[6]
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,042	[5]	4,322	[5]	11,485	[6]	11,677	[6]
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Amortization of intangible assets related to commodity contracts	(13)		(21)		(30)		(10)
Unrealized Gain (Loss) on Securities	52		187		(47)		(366)
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,751	[5]	5,035	[5]	13,812	[6]	13,363	[6]
Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	709	[3],[5]	713	[3],[5]	2,327	[4],[6]	1,686	[4],[6]
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(759)	[1]	(885)	[1]	(2,262)	[2]	(2,351)	[2]
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	11		(13)		15		(40)
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(11)		1		(17)		13
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(1)		(4)		(8)		(6)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(6)		(8)		(14)		(33)
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	6		6		4		6
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(13)		(33)		(28)		(42)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(14)		(51)		(48)		(102)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	14	[3]	51	[3]	48	[4]	102	[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 $13 million and $21 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 September 30, 2017 and 2016, respectively, unrealized mark-to-market gain of $52 million and $187 million for the three months ended September 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 $30 million and $10 million decrease to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the nine months ended September 30, 2017 and 2016, respectively, unrealized mark-to-market losses of $47 million and $366 million for the nine months ended September 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 - Genera120

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	$ 855		$ 887		$ 2,411		$ 2,556
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	697		781		2,140		2,229
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	145		160		403		350
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	296		194		678		592
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	118		93		258		231
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	68		77		220		253
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	2,179		2,192		6,110		6,211
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	241	[1]	254	[1]	416	[2]	543	[2]
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	2,420		2,446		6,526		6,754
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	817	[3]	881	[3]	2,330	[4]	2,541	[4]
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	697	[3]	782	[3]	2,129	[4]	2,225	[4]
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	151	[3]	170	[3]	423	[4]	373	[4]
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	296	[3]	195	[3]	679	[4]	607	[4]
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	229	[3]	144	[3]	446	[4]	335	[4]
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	118	[3]	143	[3]	359	[4]	357	[4]
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	2,308	[3]	2,315	[3]	6,366	[4]	6,438	[4]
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	112	[1],[3]	131	[1],[3]	160	[2],[4]	316	[2],[4]
Amortization Of Intangible Assets Related To Commodity Contracts For Revenue Net Purchased Power And Fuel	(19)		(22)		(41)		(15)
Unrealized Gain on Securities	73		88		(161)		(113)
Nuclear Fuel Amortization	(6)		28		(8)		38
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	2,420	[3]	2,446	[3]	6,526	[4]	6,754	[4]
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	38		6		81		15
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	0		(1)		11		4
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(6)		(10)		(20)		(23)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	0		(1)		(1)		(15)
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(111)		(51)		(188)		(104)
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(50)		(66)		(139)		(104)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(129)		(123)		(256)		(227)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	129	[1]	123	[1]	256	[2]	227	[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 $19 million and $22 million decrease to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the three months ended September 30, 2017 and 2016, respectively, unrealized mark-to-market gains of $73 million and $88 million for the three months ended September 30, 2017 and 2016, respectively, accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 7 - Early Nuclear Plant Retirements of the Combined Notes to Consolidated Financial Statements of $6 million and $28 million decrease to revenue net of purchased power and fuel expense for the three months ended September 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 $41 million and $15 million decrease to RNF for the amortization of intangible assets and liabilities related to commodity contracts for the nine months ended September 30, 2017 and 2016, respectively, unrealized mark-to-market losses of $161 million and $113 million for the nine months ended September 30, 2017 and 2016, respectively, accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 7 - Early Nuclear Plant Retirements of the Combined Notes to Consolidated Financial Statements of $8 million and $38 million decrease to revenue net of purchased power and fuel expense for the nine months ended September 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	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)MW	Sep. 30, 2016USD ($)
Subsequent Event [Line Items]
Power Volume | MW				220
Taxes, Miscellaneous		$ 456	$ 449	$ 1,313	$ 1,168
ExGen Renewables Holdings, LLC [Member]
Subsequent Event [Line Items]
Proceeds from Sale of Interest in Partnership Unit	$ 400

Uncategorized Items - exc-20170

Label	Element	Value
Pepco Holdings LLC [Member] | Successor [Member]
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	$ 237,000,000
Net Cash Provided by (Used in) Financing Activities	us-gaap_NetCashProvidedByUsedInFinancingActivities	65,000,000
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	(3,000,000)
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	(520,000,000)
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	0
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	29,000,000
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	94,000,000
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	0
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	(23,000,000)
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	(20,000,000)
Payment for Pension and Other Postretirement Benefits	us-gaap_PensionAndOtherPostretirementBenefitContributions	13,000,000
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	39,000,000
Increase (Decrease) in Other Operating Assets and Liabilities, Net	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet	248,000,000
Change in Exelon intercompany money pool borrowings	exc_ChangeInExelonIntercompanyMoneyPoolBorrowings	1,000,000
Payments of Distributions to Affiliates	us-gaap_PaymentsOfDistributionsToAffiliates	174,000,000
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	0
Repayments of Short-term Debt, Maturing in More than Three Months	us-gaap_RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths	300,000,000
Proceeds from Short-term Debt, Maturing in More than Three Months	us-gaap_ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths	0
Net Cash Provided by (Used in) Operating Activities	us-gaap_NetCashProvidedByUsedInOperatingActivities	546,000,000
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	0
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(441,000,000)
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	39,000,000
Net Cash Provided by (Used in) Investing Activities	us-gaap_NetCashProvidedByUsedInInvestingActivities	(631,000,000)
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	2,000,000
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	(13,000,000)
Payments to Acquire Property, Plant, and Equipment	us-gaap_PaymentsToAcquirePropertyPlantAndEquipment	624,000,000
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	(57,000,000)
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	19,000,000
Pepco Holdings LLC [Member] | Predecessor [Member]
Deferred Income Taxes and Tax Credits	us-gaap_DeferredIncomeTaxesAndTaxCredits	19,000,000
Net Cash Provided by (Used in) Financing Activities	us-gaap_NetCashProvidedByUsedInFinancingActivities	372,000,000
Proceeds from (Payments for) Other Financing Activities	us-gaap_ProceedsFromPaymentsForOtherFinancingActivities	2,000,000
Proceeds from Contributions from Parent	us-gaap_ProceedsFromContributionsFromParent	0
Proceeds from (Repayments of) Short-term Debt, Maturing in Three Months or Less	us-gaap_ProceedsFromRepaymentsOfShortTermDebtMaturingInThreeMonthsOrLess	(121,000,000)
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan	us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan	2,000,000
Repayments of Long-term Debt	us-gaap_RepaymentsOfLongTermDebt	11,000,000
Increase (Decrease) in Receivables	us-gaap_IncreaseDecreaseInReceivables	28,000,000
Payments to Acquire Marketable Securities	us-gaap_PaymentsToAcquireMarketableSecurities	68,000,000
Cash and Cash Equivalents, at Carrying Value	us-gaap_CashAndCashEquivalentsAtCarryingValue	319,000,000
Increase (Decrease) in Accounts Payable and Accrued Liabilities	us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities	42,000,000
Cash and Cash Equivalents, Period Increase (Decrease)	us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease	293,000,000
Payment for Pension and Other Postretirement Benefits	us-gaap_PensionAndOtherPostretirementBenefitContributions	4,000,000
Increase (Decrease) in Restricted Cash	us-gaap_IncreaseDecreaseInRestrictedCash	(3,000,000)
Increase (Decrease) in Other Operating Assets and Liabilities, Net	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet	8,000,000
Change in Exelon intercompany money pool borrowings	exc_ChangeInExelonIntercompanyMoneyPoolBorrowings	0
Payments of Distributions to Affiliates	us-gaap_PaymentsOfDistributionsToAffiliates	0
Increase (Decrease) in Inventories	us-gaap_IncreaseDecreaseInInventories	4,000,000
Repayments of Short-term Debt, Maturing in More than Three Months	us-gaap_RepaymentsOfShortTermDebtMaturingInMoreThanThreeMonths	0
Proceeds from Short-term Debt, Maturing in More than Three Months	us-gaap_ProceedsFromShortTermDebtMaturingInMoreThanThreeMonths	500,000,000
Net Cash Provided by (Used in) Operating Activities	us-gaap_NetCashProvidedByUsedInOperatingActivities	264,000,000
Unrealized Gain (Loss) on Derivatives	us-gaap_UnrealizedGainLossOnDerivatives	(18,000,000)
Other Noncash Income (Expense)	us-gaap_OtherNoncashIncomeExpense	(46,000,000)
Change Receivables Payables From Affiliates	exc_ChangeReceivablesPayablesFromAffiliates	0
Net Cash Provided by (Used in) Investing Activities	us-gaap_NetCashProvidedByUsedInInvestingActivities	(343,000,000)
Proceeds from Issuance of Long-term Debt	us-gaap_ProceedsFromIssuanceOfLongTermDebt	0
Payments for (Proceeds from) Other Investing Activities	us-gaap_PaymentsForProceedsFromOtherInvestingActivities	5,000,000
Payments to Acquire Property, Plant, and Equipment	us-gaap_PaymentsToAcquirePropertyPlantAndEquipment	273,000,000
Increase (Decrease) in Income Taxes Payable	us-gaap_IncreaseDecreaseInAccruedIncomeTaxesPayable	12,000,000
Proceeds from Sale of Property Held-for-sale	us-gaap_ProceedsFromSaleOfPropertyHeldForSale	0
AOCI Attributable to Parent [Member] | PECO Energy Co [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	0
Common Stock [Member] | PECO Energy Co [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	us-gaap_ProfitLoss	$ 0