Impairment of Long-Lived Assets (Details) (Midwest Generation LLC, Will County Station, USD $)	9 Months Ended
	Sep. 30, 2013
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairment Charges	$ 464,000,000
Long Lived Assets, Fair Value Disclosure	0
Level 3 | Minimum
Impaired Long-Lived Assets Held and Used [Line Items]
Fair value per kilowatt hour	0
Level 3 | Maximum
Impaired Long-Lived Assets Held and Used [Line Items]
Fair value per kilowatt hour	$ 169