Restructuring Activities (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010
Restructuring Cost and Reserve [Line Items]
Corporate cash and cash equivalents, without contractual dividend restrictions	$ 879,000,000
Cash and cash equivalents	1,175,000,000	1,469,000,000	945,000,000	1,389,000,000
Midwest Generation LLC.
Restructuring Cost and Reserve [Line Items]
Cash and cash equivalents	177,000,000
Edison Mission Energy
Restructuring Cost and Reserve [Line Items]
Unsecured notes outstanding	3,700,000,000
Investment, consolidated subsidiary	1,400,000,000
Edison Mission Energy | Unsecured Notes Maturing June 2013
Restructuring Cost and Reserve [Line Items]
Unsecured notes outstanding	$ 500,000,000