Segment Information - Reconciliation to Consolidated Financial Statements (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 23, 2016	Mar. 31, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues		$ 7,573		$ 8,830
Competitive Energy Revenue		3,429		4,188
Electric Revenue		2,657		2,574
Other Operating Income		222		318
Revenue from Purchased Oil and Gas		822		1,124
Net income (loss)		123		738
Assets		111,742			$ 95,384
Gas Domestic Regulated Revenue		444		624
Sales Revenue, Services, Other		(1)		2
Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		0		0
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		(266)		(209)
Electric Revenue		(6)		(1)
Other Operating Income		0		(1)
Revenue from Purchased Oil and Gas		0		0
Operating revenues from affiliates		(1)		2
Net income (loss)		(1)		(1)
Assets		(11,653)			(11,728)
Gas Domestic Regulated Revenue		(5)		(7)
Sales Revenue, Services, Other		(418)		(316)
Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue			$ (4)	(4)
Operating revenues from affiliates			(4)	(4)
Net income (loss)			0	0
Assets					(5,238)
Gas Domestic Regulated Revenue			0	0
Sales Revenue, Services, Other			0	0
Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		0
Operating revenues from affiliates		0
Net income (loss)		12
Assets		(4,374)
Gas Domestic Regulated Revenue		0
Sales Revenue, Services, Other		0
Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		3,695		4,397
Electric Revenue		0		0
Other Operating Income		222		319
Revenue from Purchased Oil and Gas		822		1,124
Net income (loss)		257		485
Assets		47,002			46,529
Gas Domestic Regulated Revenue		0		0
Sales Revenue, Services, Other		0		0
Exelon Generation Co L L C [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		266		210
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues		1,095		1,276
Generation Midwest [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	1,089		1,276
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		6		0
Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Electric Revenue		1,249		1,185
Other Operating Income		0		0
Revenue from Purchased Oil and Gas		0		0
Net income (loss)		115		90
Assets		26,887			26,532
Gas Domestic Regulated Revenue		0		0
Sales Revenue, Services, Other		0		0
Commonwealth Edison Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		5		1
PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		0		0
Electric Revenue		644		677
Other Operating Income		0		0
Revenue from Purchased Oil and Gas		0		0
Net income (loss)		124		139
Assets		10,462			10,367
Gas Domestic Regulated Revenue		197		308
Sales Revenue, Services, Other		0		0
PECO Energy Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		1		0
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		0		0
Electric Revenue		680		713
Other Operating Income		0		0
Revenue from Purchased Oil and Gas		0		0
Net income (loss)		101		109
Assets		8,361			8,295
Gas Domestic Regulated Revenue		249		323
Sales Revenue, Services, Other		0		0
Baltimore Gas and Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		5		7
Corporate and Other [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates			0	0
Assets					7,158
Corporate and Other [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		12
Assets		11,077
Corporate and Other [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		0		0
Electric Revenue		0		0
Other Operating Income		0		0
Revenue from Purchased Oil and Gas		0		0
Net income (loss)		(164)		(84)
Assets		9,751			15,389
Gas Domestic Regulated Revenue		0		0
Sales Revenue, Services, Other		405		318
Corporate and Other [Member] | Other Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue			42	58
Net income (loss)			(44)	(14)
Gas Domestic Regulated Revenue			1	0
Sales Revenue, Services, Other			0	0
Corporate and Other [Member] | Other Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		3
Net income (loss)		22
Gas Domestic Regulated Revenue		0
Sales Revenue, Services, Other		12
Corporate and Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		405		317
Segment Elimination [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		(695)		(533)
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues		4,739		5,840
Generation Total Consolidated Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	[1]	4,739		5,840
Generation Total Consolidated Group [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		0		0
PEPCO Holdings Inc [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue			1,096	1,268
Net income (loss)			19	53
Gas Domestic Regulated Revenue			57	86
Sales Revenue, Services, Other			0	0
PEPCO Holdings Inc [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		90
Net income (loss)		(309)
Gas Domestic Regulated Revenue		3
Sales Revenue, Services, Other		12
PEPCO Holdings Inc [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue				0
Electric Revenue				0
Other Operating Income				0
Revenue from Purchased Oil and Gas				0
Operating revenues from affiliates			0	0
Net income (loss)				0
Assets					0
Gas Domestic Regulated Revenue				0
Sales Revenue, Services, Other				0
PEPCO Holdings Inc [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue		0
Electric Revenue		90
Other Operating Income		0
Revenue from Purchased Oil and Gas		0
Operating revenues from affiliates		12
Net income (loss)		(309)
Assets		20,932
Gas Domestic Regulated Revenue		3
Sales Revenue, Services, Other		12
PEPCO Holdings Inc [Member] | Other Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Assets					16,184
PEPCO Holdings Inc [Member] | Other Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Assets		20,932
PEPCO Holdings Inc [Member] | Intersegment Eliminations [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates				0
PEPCO Holdings Inc [Member] | Intersegment Eliminations [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		12
Potomac Electric Power Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue			511	545
Operating revenues from affiliates			1	1
Net income (loss)			32	26
Assets					6,908
Gas Domestic Regulated Revenue			0	0
Sales Revenue, Services, Other			0	0
Potomac Electric Power Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		40
Operating revenues from affiliates		0
Net income (loss)		(140)
Assets		6,877
Gas Domestic Regulated Revenue		0
Sales Revenue, Services, Other		0
Delmarva Power and Light Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue			279	335
Operating revenues from affiliates			2	2
Net income (loss)			26	32
Assets					3,969
Gas Domestic Regulated Revenue			56	86
Sales Revenue, Services, Other			0	0
Delmarva Power and Light Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		24
Operating revenues from affiliates		0
Net income (loss)		(98)
Assets		3,959
Gas Domestic Regulated Revenue		3
Sales Revenue, Services, Other		0
Atlantic City Electric Company [Member] | Operating Segments [Member] | Predecessor [Member]
Segment Reporting Information [Line Items]
Electric Revenue			268	334
Operating revenues from affiliates			1	1
Net income (loss)			5	9
Assets					$ 3,387
Gas Domestic Regulated Revenue			0	0
Sales Revenue, Services, Other			$ 0	0
Atlantic City Electric Company [Member] | Operating Segments [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Electric Revenue		23
Operating revenues from affiliates		0
Net income (loss)		(105)
Assets		3,393
Gas Domestic Regulated Revenue		0
Sales Revenue, Services, Other		0
Operating Segments [Member] | PECO Energy Co Affiliate [Member]
Segment Reporting Information [Line Items]
Revenues		79		63
Operating Segments [Member] | Baltimore Gas And Electric Company Affiliate [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues		173		138
Operating Segments [Member] | Commonwealth Edison Co Affiliate [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues		5		$ 9
Operating Segments [Member] | PotomacElectricPowerCompanyAffiliate [Member] | Generation Midwest [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		6
Operating Segments [Member] | DelmarvaPowerandLightCompanyAffiliate [Member] | Generation Midwest [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		4
Operating Segments [Member] | AtlanticCityElectricCompanyAffiliate [Member] | Generation Midwest [Member] | Successor [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		$ 1

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