v2.4.0.6
Derivative Instruments (Details) (USD $)
 3 Months Ended 12 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Dec. 31, 2011
Price Risk Derivatives [Abstract]      
Power (MWh) (23)   (21)
Natural gas (MMBtu) (192)   (200)
Interest rate swaps $ 1,550,000,000 [1]   $ 5,639,000,000 [1]
Derivative Instruments, Gain (Loss) [Line Items]      
Early Repayment of Senior Debt     1,200,000,000
Unrealized losses associated with interest rate swap breakage costs 7,000,000 10,000,000  
Notional Amount Interest Rate Derivative Underlying Debt Repaid During Period     1,000,000,000
Gain (Loss) on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net   $ 91,000,000 $ 91,000,000
[1] Approximately $4.1 billion at December 31, 2011 was related to 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.