SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Movement in Valuation and qualifying accounts
Balance at Beginning of Year	$ 5		$ 5	$ 50
Charged to Costs and Expenses	438		0	0
Charged to Other Accounts	6		0	3
Deductions	0		0	48
Balance at End of Year	449		5	5
Customers
Movement in Valuation and qualifying accounts
Balance at Beginning of Year	5		5	2
Charged to Costs and Expenses	0		0	0
Charged to Other Accounts	0		0	3	[1]
Deductions	0		0	0
Balance at End of Year	5		5	5
All Others
Movement in Valuation and qualifying accounts
Balance at Beginning of Year	0		0	48
Charged to Costs and Expenses	0		0	0
Charged to Other Accounts	0		0	0
Deductions	0		0	48	[2]
Balance at End of Year	0		0	0
Deferred tax valuation allowance
Movement in Valuation and qualifying accounts
Balance at Beginning of Year	0
Charged to Costs and Expenses	438	[3]
Charged to Other Accounts	6
Deductions	0
Balance at End of Year	444
Midwest Generation LLC
Movement in Valuation and qualifying accounts
Balance at Beginning of Year	0		0	48
Charged to Costs and Expenses	1,899		0	0
Charged to Other Accounts	12		0	0
Deductions	0		0	48
Balance at End of Year	1,911		0	0
Midwest Generation LLC | All Others
Movement in Valuation and qualifying accounts
Balance at Beginning of Year	0		0	48
Charged to Costs and Expenses	1,378	[4]	0	0
Charged to Other Accounts	0		0	0
Deductions	0		0	48	[5]
Balance at End of Year	1,378		0	0
Midwest Generation LLC | All Others | Lehman Brothers
Movement in Valuation and qualifying accounts
Deductions				48	[2]
Midwest Generation LLC | Deferred tax valuation allowance
Movement in Valuation and qualifying accounts
Balance at Beginning of Year	0
Charged to Costs and Expenses	521	[6]
Charged to Other Accounts	12	[6]
Deductions	0
Balance at End of Year	$ 533

[1] Represents the consolidation of one coal project effective January 1, 2010.

[2] EME filed bankruptcy claims in the amount of $48 million related to the contracts terminated with Lehman Brothers through the termination provisions of its master netting agreements with a Lehman Brothers subsidiary. Such claims were fully reserved and were included net in prepaid expenses and other on EME's consolidated balance sheet. In 2010, EME sold its bankruptcy claims.

[3] EME recorded a deferred tax valuation allowance during the fourth quarter of 2012 due to uncertainty in future tax-sharing payments. For further discussion, see "Item 8. Combined Notes to Consolidated Financial Statements—Note 7. Income Taxes."

[4] Midwest Generation recorded a full valuation allowance during the fourth quarter of 2012 relating to the impairment of its intercompany loan with EME. For further discussion, see "Item 8. Combined Notes to Consolidated Financial Statements—Note 15. Related Party Transactions."

[5] Midwest Generation filed bankruptcy claims in the amount of $48 million related to the contracts terminated with Lehman Brothers through the termination provisions of its master netting agreements with a Lehman Brothers subsidiary. Such claims were fully reserved and were included net in other current assets on Midwest Generation's consolidated balance sheet. In 2010, Midwest Generation sold its bankruptcy claims.

[6] Midwest Generation recorded a deferred tax valuation allowance during the fourth quarter of 2012 related to the impairment of its intercompany loan with EME. For further discussion, see "Item 8. Combined Notes to Consolidated Financial Statements—Note 7. Income Taxes."