Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended			12 Months Ended
	Jun. 30, 2012 MMBTU MW		Jun. 30, 2011	Jun. 30, 2012 MMBTU MW		Jun. 30, 2011	Dec. 31, 2011 MMBTU MW
Price Risk Derivatives [Abstract]
Power (MWh)	(21)			(21)			(21)
Natural gas (MMBtu)	(68)			(68)			(200)
Interest rate swaps	$ 1,592	[1]		$ 1,592	[1]		$ 5,639	[1]
Derivative Instruments, Gain (Loss) [Line Items]
Early Repayment of Senior Debt							1,200
Unrealized losses associated with interest rate swap breakage costs	8		7	15		17
Notional Amount Interest Rate Derivative Underlying Debt Repaid During Period							1,000
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net						$ 91	$ 91

[1] Approximately $4.1 billion at December 31, 2011 was related to hedges of our First Lien Credit Facility's variable rate debt that was converted to fixed rate debt. On March 26, 2012, we terminated the interest rate swaps formerly hedging our First Lien Credit Facility.