Investment in Constellation Energy Nuclear Group, LLC (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended										3 Months Ended			6 Months Ended						0 Months Ended	3 Months Ended		6 Months Ended				12 Months Ended	6 Months Ended		0 Months Ended
	Jun. 30, 2014		Sep. 30, 2013	Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013		May 15, 2014	Dec. 31, 2013		Apr. 02, 2014 CENGMember [Member]	Apr. 02, 2014 CENG [Member] Subsequent Event [Member] FinancialGuaranteeMember	Apr. 02, 2014 CENG [Member] Subsequent Event [Member] Payment Guarantee [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member]		Jun. 30, 2013 Exelon Generation Co L L C [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member]		Jun. 30, 2013 Exelon Generation Co L L C [Member]		Dec. 31, 2013 Exelon Generation Co L L C [Member]		Apr. 02, 2014 Exelon Generation Co L L C [Member] CENGMember [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] CENGMember [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member] CENGMember [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] CENGMember [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member] CENGMember [Member]	Apr. 02, 2014 Exelon Generation Co L L C [Member] CENG [Member] Subsequent Event [Member]	Apr. 02, 2014 Exelon Generation Co L L C [Member] CENG [Member] Subsequent Event [Member] Payment Guarantee [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member] First Distribution [Member] CENG [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Second Distribution [Member] CENG [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] Minimum [Member]	Apr. 02, 2014 Constellation Energy Group LLC [Member] EDFI [Member] Subsequent Event [Member]	Apr. 02, 2014 Constellation Energy Group LLC [Member] GenerationCoMember [Member] Subsequent Event [Member]	Apr. 02, 2014 Electricite De France LLC [Member] CENG [Member] Subsequent Event [Member] FinancialGuaranteeMember
Schedule of Equity Method Investments [Line Items]
Percentage of ownership interest in CENG (as a percent)									67.00%						50.01%			50.01%
Total equity investment earnings (losses) - CENG															$ 19		$ 19
Basis difference in investment in CENG															204			204
Gain on consolidation of CENG	261														261			(268)
Related Party Transaction [Line Items]
BusinessAcquisitionPreexistingRelationshipGainLossRecognized	125				125
BusinessCombinationStepAcquisitionEquityInterestInAcquireeFairValue1	136
Loss on equity method investments	0			(21)	(20)		(30)								(1)		(21)	(20)		(30)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(1,906)	[1]			(1,906)	[1]				(2,040)	[1]	1,500			37	[1]		37	[1]			214	[1]					139
Revenues	6,024		6,141	6,141	13,261	[2]	12,223	[2]							3,789		4,070	8,179		7,603						23	98
Required purchases of power from CENG's nuclear plants not sold to third parties (as a percent)																																	85.00%
Equity Method Investments	0				0					1,925					0			0				1,925						1,900
Purchase of nuclear output by EDF (as a percent)					49.99%													49.99%
Impact Of Transactions Under Agreements [Abstract]
Increase (Decrease) in earnings	0			0											201		352	535		744
Net Income																									76		76
Business Combination, Integration Related Costs																									11		18
Amortization of energy contract assets and liabilities					113	[3]	306	[3]										118	[3]	344	[3]
Distribution From Affiliates																															115	13
Loan Recievable from CENG																													400
Special and Preferred Distributions by CENG																		235		474														400	400
Debt Instrument Interest Rate Stated Percentage																													5.25%
InterestRateOnDistribution																																			8.50%
Maximum exposure related to guarantees	9,839				9,839										6,375			6,375																		145
Due To Affiliate Current And Noncurrent													165	245																205
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net Abstract
Current Assets												499												499
Property, plant and equipment												2,958												2,958
Nuclear Fuel Inventory												482												482
Other Non Current Assets												10												10
Total assets												5,904												5,904
Current liabilities												237												237
Asset Retirement Obligation												1,701												1,701
Unamortized energy contracts												171												171
Pension obligation																									281		281
Deferred credits and other liabilities and preferred securities												114												114
BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities												2,504												2,504
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net												3,400												3,400
Noncontrolling interest acquired					1,548													1,548
ReductionToNetIncomeAttributableToNonControllingInterest																								$ 4

[1] (a) All amounts are net of tax. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.

[2] For the six months ended June 30, 2014 and 2013, utility taxes of $45 million and $39 million, respectively, are included in revenues and expenses for Generation. For the six months ended June 30, 2014 and 2013, utility taxes of $119 million and $117 million, respectively, are included in revenues and expenses for ComEd. For the six months ended June 30, 2014 and 2013, utility taxes of $65 million and $64 million, respectively, are included in revenues and expenses for PECO. For the six months ended June 30, 2014 and 2013, utility taxes of $43 million and $41 million, respectively, are included in revenues and expenses for BGE.

[3] Included in purchased power and fuel expense on the Registrants' Consolidated Statements of Operations and Comprehensive Income