CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net Income (Loss)	$ (909)	$ (1,079)	$ 163
Other comprehensive income (loss), net of tax
Valuation allowance on deferred tax asset	(6)	0	0
Pension and postretirement benefits other than pensions:
Prior service adjustment, net of tax	0	0	(7)
Net gain (loss) adjustment, net of tax expense (benefit)	0	(15)	(14)
Amortization of net loss and prior service adjustment included in expense, net of tax	4	2	1
Unrealized gains (losses) on derivatives qualified as cash flow hedges:
Unrealized holding gains (losses) arising during periods, net of income tax expense (benefit)	(17)	(12)	55
Reclassification adjustments included in net income (loss), net of income tax benefit	(25)	(38)	(144)
Other comprehensive loss, net of tax	(44)	(63)	(109)
Comprehensive Income (Loss)	(953)	(1,142)	54
Comprehensive Income Attributable to Noncontrolling Interests	(16)	1	1
Comprehensive Income (Loss)	(969)	(1,141)	55
Midwest Generation LLC
Net Income (Loss)	(1,464)	(270)	215
Other comprehensive income (loss), net of tax
Valuation allowance on deferred tax asset	(12)	0	0
Pension and postretirement benefits other than pensions:
Prior service adjustment, net of tax	0	0	(6)
Net gain (loss) adjustment, net of tax expense (benefit)	(1)	(13)	(6)
Amortization of net loss and prior service adjustment included in expense, net of tax	2	1	0
Unrealized gains (losses) on derivatives qualified as cash flow hedges:
Unrealized holding gains (losses) arising during periods, net of income tax expense (benefit)	4	23	45
Reclassification adjustments included in net income (loss), net of income tax benefit	(26)	(25)	(90)
Other comprehensive loss, net of tax	(33)	(14)	(57)
Comprehensive Income (Loss)	$ (1,497)	$ (284)	$ 158