CONSOLIDATED STATEMENTS OF TOTAL EQUITY (USD $) In Millions, unless otherwise specified		Total USD ($)		Common Stock USD ($)		Additional Paid-in Capital USD ($)		Retained Earnings (Deficit) USD ($)		Accumulated Other Comprehensive Income (Loss) USD ($)		Non-controlling Interest USD ($)		American Bituminous	Midwest Generation LLC USD ($)		Midwest Generation LLC Common Stock USD ($)		Midwest Generation LLC Additional Paid-in Capital USD ($)		Midwest Generation LLC Retained Earnings (Deficit) USD ($)		Midwest Generation LLC Accumulated Other Comprehensive Income (Loss) USD ($)
Balance at Dec. 31, 2009		$ 2,837		$ 64		$ 1,339		$ 1,280		$ 78		$ 76			$ 3,745		$ 0		$ 3,511		$ 180		$ 54
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Impact of consolidation and deconsolidation of variable interest entities	[1]	(61)		0		0		10		0		(71)
Net Income (Loss)		163		0		0		164		0		(1)			215		0		0		215		0
Other comprehensive loss, net of tax		(109)		0		0		0		(109)		0			(57)		0		0		0		(57)
Cash distribution to parent															(125)		0		0		(125)		0
Payments to Edison International for stock purchases related to stock-based compensation		(6)		0		0		(6)		0		0
Excess tax benefits related to stock option exercises		1		0		1		0		0		0
Other stock transactions, net		6		0		6		0		0		0
Purchase of noncontrolling interest		(10)		0		(10)		0		0		0
Ownership interest (as a percentage)														50.00%
Balance at Dec. 31, 2010		2,821		64		1,336		1,448		(31)		4			3,778		0		3,511		270		(3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)		(20)													48
Balance at Mar. 31, 2011
Balance at Dec. 31, 2010		2,821		64		1,336		1,448		(31)		4			3,778		0		3,511		270		(3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)		(1,079)		0		0		(1,078)		0		(1)			(270)		0		0		(270)		0
Other comprehensive loss, net of tax		(63)		0		0		0		(63)		0			(14)		0		0		0		(14)
Cash distribution to parent															(225)		0		0		(225)		0
Payments to Edison International for stock purchases related to stock-based compensation		(5)		0		0		(5)		0		0
Excess tax benefits related to stock option exercises		2		0		2		0		0		0
Other stock transactions, net		4		0		4		0		0		0
Purchase of noncontrolling interest		(16)		0		(15)		0		0		(1)
Balance at Dec. 31, 2011		1,664		64		1,327		365		(94)		2			3,269		0		3,511		(225)		(17)
Balance at Sep. 30, 2011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)		(1,060)	[2]												(357)	[3]
Balance at Dec. 31, 2011		1,664													3,269
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)		(82)													(9)
Balance at Mar. 31, 2012
Balance at Dec. 31, 2011		1,664		64		1,327		365		(94)		2			3,269		0		3,511		(225)		(17)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)		(909)		0		0		(925)		0		16			(1,464)		0		0		(1,464)		0
Other comprehensive loss, net of tax		(44)		0		0		0		(44)		0			(33)		0		0		0		(33)
Non-cash distribution to parent		(222)	[4]	0	[4]	(222)	[4]	0	[4]	0	[4]	0	[4]		(106)	[5]	0	[5]	(106)	[5]	0	[5]	0	[5]
Payments to Edison International for stock purchases related to stock-based compensation		(17)		0		0		(17)		0		0
Excess tax benefits related to stock option exercises		5		0		5		0		0		0
Other stock transactions, net		6		0		6		0		0		0
Contributions from noncontrolling interests	[6]	288		0		0		0		0		288
Distributions to noncontrolling interests		(18)		0		0		0		0		(18)
Transfers of assets to Capistrano Wind Partners	[7]	(21)		0		(21)		0		0		0
Balance at Dec. 31, 2012		732		64		1,095		(577)		(138)		288			1,666		0		3,405		(1,689)		(50)
Balance at Sep. 30, 2012
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss)		(561)													(1,401)
Balance at Dec. 31, 2012		$ 732													$ 1,666

[1] Effective January 1, 2010, EME adopted new accounting guidance issued by the FASB related to the consolidation of VIEs. As a result of this guidance, EME prospectively consolidated a 50% interest in American Bituminous Power Partners, L.P. (Ambit) and deconsolidated the Elkhorn Ridge and San Juan Mesa wind projects. The impact of adopting this guidance resulted in a cumulative effect adjustment that increased retained earnings by $10 million.

[2] Reflects $704 million pre-tax ($424 million after tax) of asset impairment charges. For more information, see Note 13—Asset Impairments and Other Charges. In addition, the amount reflects a $1,032 million pre-tax ($623 million after tax) impairment charge related to Homer City. For more information, see Note 14—Discontinued Operations.

[3] Reflects a $640 million pre-tax ($386 million, after tax) impairment charge. For more information, see Note 13—Asset Impairments and Other Charges.

[4] During the fourth quarter of 2012, EME recorded a non-cash distribution to EIX related to the tax-allocation agreement. See Note 7—Income Taxes—EME—Current and Deferred Taxes.

[5] During 2012, Midwest Generation recorded a non-cash distribution to its parent related to the tax-allocation agreement. See Note 7—Income Taxes—Midwest Generation—Current and Deferred Taxes.

[6] Funds contribution by third-party investors related to the Capistrano Wind equity capital raise are reported in noncontrolling interest. For further information, see Note 3—Variable Interest Entities—Projects or Entities that are Consolidated—Capistrano Wind Equity Capital.

[7] Additional paid in capital was reduced by $21 million due to a new tax basis in the assets transferred to Capistrano Wind Partners. For further information, see Note 3—Variable Interest Entities—Projects or Entities that are Consolidated—Capistrano Wind Equity Capital.