Goodwill (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2013
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 2,625	$ 2,625
Goodwill Impairment Loss		0
Goodwill, ending balance		2,625
Goodwill Gross [Member]
Goodwill [Roll Forward]
Goodwill Impairment Loss		0	[1]
Goodwill, ending balance		4,608	[1]
Goodwill Accumulated Impairment Losses [Member]
Goodwill [Roll Forward]
Goodwill Impairment Loss		0
Goodwill, ending balance		1,983
Commonwealth Edison Co [Member]
Goodwill, Impaired [Abstract]
Annual revenue requirement reduction	14	168
Goodwill [Roll Forward]
Goodwill, beginning balance	2,625	2,625
Goodwill Impairment Loss		0
Goodwill, ending balance		2,625
Commonwealth Edison Co [Member] | Goodwill Gross [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	4,608	4,608
Goodwill Impairment Loss		0	[1]
Goodwill, ending balance		4,608	[1]
Commonwealth Edison Co [Member] | Goodwill Accumulated Impairment Losses [Member]
Goodwill [Roll Forward]
Goodwill, beginning balance	1,983	1,983
Goodwill Impairment Loss		0
Goodwill, ending balance		$ 1,983

[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.