Commitments and Contingencies (Contingencies) (Details) (USD $)	12 Months Ended			1 Months Ended				12 Months Ended						1 Months Ended	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jan. 31, 2011 Homer City owners	Jan. 31, 2011 Homer City Violations of the PSD and Title V provisions of the CAA	Jan. 31, 2012 Midwest Generation LLC [Member] claims	Oct. 31, 2011 Midwest Generation LLC [Member] claims	Dec. 31, 2012 Midwest Generation LLC [Member]	Dec. 31, 2011 Midwest Generation LLC [Member]	Jan. 02, 2014 Midwest Generation LLC [Member]	Dec. 31, 2013 Midwest Generation LLC [Member] sites	Jul. 02, 2013 Midwest Generation LLC [Member]	Jan. 02, 2013 Midwest Generation LLC [Member]	Aug. 31, 2009 Midwest Generation LLC [Member] Violation of certain operating permit requirements sites	Mar. 31, 2011 Midwest Generation LLC [Member] Violation of certain operating permit requirements claims	Dec. 31, 2013 Indemnities under International Asset Sale Agreements	Dec. 31, 2012 Indemnities under International Asset Sale Agreements
Contingencies
Number of coal-fired electric generating stations (in sites)														6
Penalties sought, per violation, per day, minimum end of range					$ 32,500									$ 25,000
Penalties sought, per violation, per day, maximum end of range					37,500									37,500
Number of fully dismissed claims in the complaint filed by the US EPA and the State of Illinois (in claims)															9
Number of claims in the complaint filed by the US EPA and the State of Illinois (in claims)															10
Number of complaints filed asserting claims of nuisance, negligence, trespass, and strict liability (in claims)						2
Similar number of complaints previously filed asserting claims of nuisance, negligence, trespass, and strict liability that were dismissed							2
Number of prior owners of facilities (in owners)				2
Accrued liability for environmental remediation											8,000,000
Identified sites for environmental remediation (in number of sites)											2
Receivable related to insurance claims	1,000,000	3,000,000
Gain related to business interruption insurance coverage	1,000,000		5,000,000						2,000,000
Proceeds from settlement of insurance claims	6,000,000	2,000,000						2,000,000
Liability under indemnities																20,000,000	20,000,000
Lease payments not paid										$ 76,000,000		$ 76,000,000	$ 76,000,000