Quarterly Data (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Earnings Per Share Basic [Abstract]
Average common shares outstanding - basic	858		855
Earnings Per Share, Basic	$ 0.10		$ (0.01)
Earnings Per Share Diluted
Average common shares outstanding - diluted	861		855
Earnings Per Share, Diluted	$ 0.10		$ (0.01)
Selected Quarterly Financial Information [Line Items]
Revenues	$ 7,237	[1]	$ 6,082	[1]
Operating Income (Loss)	163		508
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	93		1
Exelon Generation Co L L C [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	4,390		3,533
Operating Income (Loss)	(389)		(64)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	(185)		(17)
Commonwealth Edison Co [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	1,134		1,160
Operating Income (Loss)	238		209
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	98		(81)
PECO Energy Co [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	993		895
Operating Income (Loss)	149		203
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	89		122
Baltimore Gas and Electric Company [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	1,054		880
Operating Income (Loss)	169		163
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 88		$ 80

[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.