Merger and Acquisitions (Details) (USD $)	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2012
Business Acquisition, Impact Of Merger [Abstract]
Revenues	$ 7,237,000,000	[1]	$ 6,082,000,000	[1]
Net income	93,000,000		1,000,000
Business Acquisition, Regulatory Matters [Abstract]
Business Acquisition Potential Cash Payment	40,000,000
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start	53,000,000
Payments	12,000,000
Restructuring Reserve, Period End	41,000,000
Business Acquisition, Costs Recognized Post Merger [Abstract]
Length of years for charitable contributions at $7 million per year	10 years
Business Acquisition Charitable Contributions Per Year	7,000,000
Exelon Generation Co L L C [Member]
Business Acquisition, Impact Of Merger [Abstract]
Revenues	4,390,000,000		3,533,000,000
Net income	(185,000,000)		(17,000,000)
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start	10,000,000
Payments	1,000,000
Restructuring Reserve, Period End	9,000,000
Exelon Generation Co L L C [Member] | Minimum [Member]
Business Acquisition, Regulatory Matters [Abstract]
Business Acquisition, Construction Cost			95,000,000
Business Acquisition, Development Of New Generation Cost	600,000,000
Business Acquisition, Expected New Generation Mwh	285
Exelon Generation Co L L C [Member] | Maximum [Member]
Business Acquisition, Regulatory Matters [Abstract]
Business Acquisition, Construction Cost			120,000,000
Business Acquisition, Development Of New Generation Cost	650,000,000
Business Acquisition, Expected New Generation Mwh	300
Commonwealth Edison Co [Member]
Business Acquisition, Impact Of Merger [Abstract]
Revenues	1,134,000,000		1,160,000,000
Net income	98,000,000		(81,000,000)
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start	0
Payments	0
Restructuring Reserve, Period End	0
PECO Energy Co [Member]
Business Acquisition, Impact Of Merger [Abstract]
Revenues	993,000,000		895,000,000
Net income	89,000,000		122,000,000
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start	0
Payments	0
Restructuring Reserve, Period End	0
Baltimore Gas and Electric Company [Member]
Business Acquisition, Impact Of Merger [Abstract]
Revenues	1,054,000,000		880,000,000
Net income	88,000,000		80,000,000
Regulatory Assets Transfer Changes	8,000,000
Business Acquisition, Regulatory Matters [Abstract]
Business Acquisition, Direct Investment With State And Local Governments Due To Settlement					1,000,000,000
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start	6,000,000
Payments	2,000,000
Restructuring Reserve, Period End	$ 4,000,000
Customer Relationships [Member] | Constellation Energy Group Acquisition [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Asset Weighted Average Useful Life	12 years 4 months 26 days
Trade Names [Member] | Constellation Energy Group Acquisition [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Asset Weighted Average Useful Life	10 years
Power Supply Contracts [Member] | Constellation Energy Group Acquisition [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite Lived Intangible Asset Weighted Average Useful Life	1 year 6 months 3 days

[1] For the ##D<curmonth> months ended ##D<cyperiod> and ##D<pyfiscal>, utility taxes of $##D<gcytdutiltax> million and $##D<gpytdutiltax> million, respectively, are included in revenues and expenses for Generation. For the ##D<curmonth> months ended ##D<cyperiod> and ##D<pyfiscal>, utility taxes of $##D<ccytdutiltax> million and $##D<cpytdutiltax> million, respectively, are included in revenues and expenses for ComEd. For the ##D<curmonth> months ended ##D<cyperiod> and ##D<pyfiscal>, utility taxes of $##D<pcytdutiltax> million and $##D<ppytdutiltax> million, respectively, are included in revenues and expenses for PECO. For the ##D<curmonth> months ended ##D<cyperiod> and period of March 12, 2012 through ##D<pyperiod>, utility taxes of $##D<bcytdutiltax> million and $##D<bpytdutiltax> million, respectively, are included in revenues and expenses for BGE.