Quarterly Data (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2014	Sep. 30, 2013	Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013
Earnings Per Share Basic [Abstract]
Average common shares outstanding - basic	860		856	860		856
Earnings Per Share, Basic	$ 0.61		$ 0.57	$ 0.71		$ 0.57
Earnings Per Share Diluted
Average common shares outstanding - diluted	864		860	863		859
Earnings Per Share, Diluted	$ 0.60		$ 0.57	$ 0.71		$ 0.57
Selected Quarterly Financial Information [Line Items]
Revenues	$ 6,024	$ 6,141	$ 6,141	$ 13,261	[1]	$ 12,223	[1]
Operating Income (Loss)	829		1,005	992		1,513
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	557		497			498
Share Price And Dividend [Abstract]
Close	$ 35			$ 35
Exelon Generation Co L L C [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	3,789		4,070	8,179		7,603
Operating Income (Loss)	429		603	41		539
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	372		328	188		310
Commonwealth Edison Co [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	1,128		1,080	2,262		2,239
Operating Income (Loss)	258		232	496		440
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	111		96	209		14
PECO Energy Co [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	656		672	1,649		1,567
Operating Income (Loss)	134		138	283		341
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	84		78	173		200
Baltimore Gas and Electric Company [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	653		653	1,707		1,533
Operating Income (Loss)	55		69	224		233
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 19		$ 25	$ 106		$ 106

[1] 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.