CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Income (Loss)	$ (641)	$ (909)	$ (1,079)
Other comprehensive income (loss), net of tax
Valuation allowance on deferred tax asset	0	(6)	0
Pension and postretirement benefits other than pensions:
Prior service adjustment, net of tax	(2)	0	0
Net gain (loss) adjustment, net of tax expense (benefit)	35	0	(15)
Amortization of net loss and prior service adjustment included in expense, net of tax	5	4	2
Unrealized gains (losses) on derivatives qualified as cash flow hedges:
Unrealized holding gains (losses) arising during periods, net of income tax expense (benefit)	34	(17)	(12)
Reclassification adjustments included in net income (loss), net of income tax benefit	5	(25)	(38)
Other comprehensive income (loss), net of tax	77	(44)	(63)
Comprehensive Income (Loss)	(564)	(953)	(1,142)
Comprehensive (Income) Loss Attributable to Noncontrolling Interests	(29)	(16)	1
Comprehensive Income (Loss)	(593)	(969)	(1,141)
Midwest Generation LLC [Member]
Net Income (Loss)	(633)	(1,464)	(270)
Other comprehensive income (loss), net of tax
Valuation allowance on deferred tax asset	0	(12)	0
Pension and postretirement benefits other than pensions:
Net gain (loss) adjustment, net of tax expense (benefit)	25	(1)	(13)
Amortization of net loss and prior service adjustment included in expense, net of tax	3	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)	(1)	4	23
Reclassification adjustments included in net income (loss), net of income tax benefit	2	(26)	(25)
Other comprehensive income (loss), net of tax	29	(33)	(14)
Comprehensive Income (Loss)	$ (604)	$ (1,497)	$ (284)