Intangible Assets - Schedule of Goodwill (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill [Line Items]
Goodwill, Impairment Loss		$ 0
Goodwill [Roll Forward]
Goodwill, Gross		4,655	$ 4,655	$ 4,608
Goodwill, Impaired, Accumulated Impairment Loss		1,983	1,983	1,983
Goodwill, beginning balance		2,672	2,625
Goodwill, ending balance		2,672	2,672
Commonwealth Edison Co [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss	[1]	0
Goodwill [Roll Forward]
Goodwill, Gross	[1]	4,608	4,608	4,608
Goodwill, Impaired, Accumulated Impairment Loss		1,983	1,983	1,983
Goodwill, beginning balance		2,625	2,625
Goodwill, ending balance		2,625	2,625
Exelon Generation Co L L C [Member]
Goodwill [Line Items]
Goodwill, Impairment Loss		0
Goodwill [Roll Forward]
Goodwill, Gross		47	47	$ 0
Goodwill, beginning balance		47	0
Goodwill from business combination			47
Goodwill, ending balance		$ 47	$ 47

[1] Reflects goodwill recorded in 2000 from the PECO/Unicom (predecessor parent company of ComEd) merger net of amortization, resolution of tax matters and other non-impairment-related changes as allowed under previous authoritative guidance.