CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Statement of Income and Comprehensive Income [Abstract]
Net Income (Loss)	$ (1,079)	$ 163	$ 194
Pension and postretirement benefits other than pensions
Prior service adjustment, net of tax	0	(7)	1
Net gain (loss) adjustment, net of tax expense (benefit) of $(10), $(10) and $6 for 2011, 2010 and 2009, respectively	(15)	(14)	10
Amortization of net loss and prior service adjustment included in expense, net of tax	2	1	2
Unrealized gains (losses) on derivatives qualified as cash flow hedges
Unrealized holding gains (losses) arising during period, net of income tax expense (benefit) of $(7), $37 and $36 for 2011, 2010 and 2009, respectively	(12)	55	43
Reclassification adjustments included in net income (loss), net of income tax benefit of $25, $96 and $124 for 2011, 2010 and 2009, respectively	(38)	(144)	(178)
Other comprehensive loss, net of tax	(63)	(109)	(122)
Comprehensive Income (Loss)	(1,142)	54	72
Comprehensive Loss Attributable to Noncontrolling Interests	1	1	3
Comprehensive Income (Loss) Attributable to Edison Mission Energy Common Shareholder	$ (1,141)	$ 55	$ 75