Segment Information - Reconciliation to Consolidated Financial Statements (Details) - USD ($) $ in Millions	3 Months Ended						6 Months Ended
	Jun. 30, 2016		Jun. 30, 2016	Mar. 23, 2016	Jun. 30, 2015		Jun. 30, 2016		Jun. 30, 2015		Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 6,910				$ 6,514		$ 14,485		$ 15,345
Competitive Energy Revenue	3,301				3,512		6,732		7,699
Electric Revenue	3,480				2,270		6,136		4,844
Other Operating Income	(434)				137		(213)		460
Revenue from Purchased Oil and Gas	367				431		1,189		1,555
Operating revenues from affiliates	1				1
Net income (loss)	306				633		430		1,372
Assets	112,778		$ 112,778				112,778				$ 95,384
Gas Domestic Regulated Revenue	197				165		641		788
Sales Revenue, Services, Other	(1)				(1)		0		(1)
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue					0		0		0
Electric Revenue	0				0		0		0
Other Operating Income					0		0		0
Revenue from Purchased Oil and Gas					0		0		0
Net income (loss)	(52)				28		(215)		(55)
Assets	10,069		10,069				10,069				15,389
Gas Domestic Regulated Revenue	0				0		0		0
Sales Revenue, Services, Other	398				340		803		657
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	(354)				(151)		(620)		(360)
Electric Revenue	(7)				(1)		(15)		(2)
Other Operating Income	(1)				(1)		(1)		0
Revenue from Purchased Oil and Gas	0				0		0		0
Operating revenues from affiliates	(771)				(493)		2		1
Net income (loss)	(1)				(1)		(2)		(3)
Assets	(12,125)		(12,125)				(12,125)				(11,728)
Gas Domestic Regulated Revenue	(2)				(1)		(5)		(9)
Sales Revenue, Services, Other	(409)				(341)		(826)		(658)
Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	(4)		(5)
Operating revenues from affiliates	(4)		(5)
Net income (loss)	10		23
Assets	(4,652)		(4,652)				(4,652)
Gas Domestic Regulated Revenue	0		0
Sales Revenue, Services, Other	0		0
Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue				$ (4)	0				0
Operating revenues from affiliates				(4)	(4)				(7)
Net income (loss)				0	0				0
Assets											(5,238)
Gas Domestic Regulated Revenue				0	0				0
Sales Revenue, Services, Other				0	0				0
Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	3,655				3,663		7,352		8,059
Electric Revenue	0				0		0		0
Other Operating Income	(433)				138		(212)		460
Revenue from Purchased Oil and Gas	367				431		1,189		1,555
Net income (loss)	28				390		285		875
Assets	46,897		46,897				46,897				46,529
Gas Domestic Regulated Revenue	0				0		0		0
Sales Revenue, Services, Other	0				0		0		0
Exelon Generation Co L L C [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	355				152		621		360
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,083				1,206		2,179		2,482
Generation Midwest [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	1,076	[1]			1,206	[1]	2,166	[2]	2,482	[2]
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	7				0		13		0
Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	0				0		0		0
Electric Revenue	1,286				1,148		2,535		2,333
Other Operating Income	0				0		0		0
Revenue from Purchased Oil and Gas	0				0		0		0
Net income (loss)	145				99		260		189
Assets	28,105		28,105				28,105				26,532
Gas Domestic Regulated Revenue	0				0		0		0
Sales Revenue, Services, Other	0				0		0		0
Commonwealth Edison Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	3				1		8		2
PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	0				0		0		0
Electric Revenue	587				582		1,232		1,259
Other Operating Income	0				0		0		0
Revenue from Purchased Oil and Gas	0				0		0		0
Net income (loss)	100				70		224		209
Assets	10,586		10,586				10,586				10,367
Gas Domestic Regulated Revenue	77				79		273		387
Sales Revenue, Services, Other	0				0		0		0
PECO Energy Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	2				0		4		1
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	0				0		0		0
Electric Revenue	584				541		1,264		1,254
Other Operating Income	0				0		0		0
Revenue from Purchased Oil and Gas	0				0		0		0
Net income (loss)	34				47		135		157
Assets	8,325		8,325				8,325				8,295
Gas Domestic Regulated Revenue	96				87		345		410
Sales Revenue, Services, Other	0				0		0		0
Baltimore Gas and Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	4				1		9		8
Corporate and Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates							803		656
Pepco Holdings LLC [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	1,030		1,120
Net income (loss)	52		(257)
Gas Domestic Regulated Revenue	26		28
Sales Revenue, Services, Other	10		23
Pepco Holdings LLC [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue				1,096	1,094				2,362
Net income (loss)				19
Gas Domestic Regulated Revenue				57	25				111
Sales Revenue, Services, Other				0	0				0
Pepco Holdings LLC [Member] | Corporate, Non-Segment [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	0		3
Operating revenues from affiliates	10		23
Net income (loss)	(22)		0
Assets	11,042		11,042				11,042
Gas Domestic Regulated Revenue	0		(1)
Sales Revenue, Services, Other	10		23
Pepco Holdings LLC [Member] | Corporate, Non-Segment [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue				42	59				115
Operating revenues from affiliates				0	0				0
Net income (loss)				(44)	(3)				(17)
Assets											7,162
Gas Domestic Regulated Revenue				1	0				0
Sales Revenue, Services, Other				0	0				0
Pepco Holdings LLC [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	0						0		0
Electric Revenue	1,030				0		1,120		0
Other Operating Income	0						0		0
Revenue from Purchased Oil and Gas	0						0		0
Operating revenues from affiliates	10		23
Net income (loss)	52				0		(257)		0
Assets	20,921		20,921				20,921				0
Gas Domestic Regulated Revenue	26				0		28		0
Sales Revenue, Services, Other	10				0		23		0
Pepco Holdings LLC [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates				0	0				0
Net income (loss)					53				106
Assets											16,188
Pepco Holdings LLC [Member] | Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	10				0		23		0
Corporate, Non-Segment [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	398				340
Segment Elimination [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates							(1,466)		(1,026)
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	3,589				4,232		8,329		10,074
Generation Total Consolidated Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	3,589	[1]			4,232	[1]	8,329	[2]	10,074	[2]
Generation Total Consolidated Group [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0				0		0		0
Potomac Electric Power Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	509		550
Operating revenues from affiliates	1		2
Net income (loss)	49		(92)
Assets	7,099		7,099				7,099
Gas Domestic Regulated Revenue	0		0
Sales Revenue, Services, Other	0		0
Potomac Electric Power Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue				511	504				1,049
Operating revenues from affiliates				1	1				2
Net income (loss)				32	42				68
Assets											6,908
Gas Domestic Regulated Revenue				0	0				0
Sales Revenue, Services, Other				0	0				0
Delmarva Power and Light Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	255		279
Operating revenues from affiliates	2		2
Net income (loss)	12		(86)
Assets	3,971		3,971				3,971
Gas Domestic Regulated Revenue	26		29
Sales Revenue, Services, Other	0		0
Delmarva Power and Light Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue				279	246				580
Operating revenues from affiliates				2	2				3
Net income (loss)				26	8				40
Assets											3,969
Gas Domestic Regulated Revenue				56	25				111
Sales Revenue, Services, Other				0	0				0
Atlantic City Electric Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue	270		293
Operating revenues from affiliates	1		1
Net income (loss)	3		(102)
Assets	3,461		3,461				3,461
Gas Domestic Regulated Revenue	0		0
Sales Revenue, Services, Other	0		$ 0
Atlantic City Electric Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue				268	285				618
Operating revenues from affiliates				1	1				2
Net income (loss)				5	6				15
Assets											$ 3,387
Gas Domestic Regulated Revenue				0	0				0
Sales Revenue, Services, Other				$ 0	0				0
Operating Segments [Member] | PECO Energy Co Affiliate [Member]
Segment Reporting Information [Line Items]
Revenues					49		143		112
Operating Segments [Member] | PECO Energy Co Affiliate [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	64
Operating Segments [Member] | Baltimore Gas And Electric Company Affiliate [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	135				97		306		235
Operating Segments [Member] | Commonwealth Edison Co Affiliate [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	13				$ 6		$ 18		$ 15
Operating Segments [Member] | PotomacElectricPowerCompanyAffiliate [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	88
Operating Segments [Member] | PotomacElectricPowerCompanyAffiliate [Member] | Generation Midwest [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	94
Operating Segments [Member] | DelmarvaPowerandLightCompanyAffiliate [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	43
Operating Segments [Member] | DelmarvaPowerandLightCompanyAffiliate [Member] | Generation Midwest [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	47
Operating Segments [Member] | AtlanticCityElectricCompanyAffiliate [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	12
Operating Segments [Member] | AtlanticCityElectricCompanyAffiliate [Member] | Generation Midwest [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	$ 13

[1] Three Months Ended June 30, 2016 Three Months Ended June 30, 2015 Revenuesfrom externalcustomers(a)IntersegmentrevenuesTotalRevenuesRevenuesfrom externalcustomers(a)(c)Intersegmentrevenues(c)TotalRevenues(c)Mid-Atlantic$1,432 $(16) $1,416 $1,364 $(18) $1,346Midwest1,076 7 1,083 1,206 — 1,206New England352 (1) 351 367 — 367New York356 (10) 346 222 (4) 218ERCOT207 — 207 194 (2) 192Other Power Regions232 (9) 223 310 (21) 289Total Revenues for Reportable Segments3,655 (29) 3,626 3,663 (45) 3,618Other(b)(66) 29 (37) 569 45 614Total Generation Consolidated Operating Revenues$3,589 $— $3,589 $4,232 $— $4,232

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