v2.4.0.6
Debt (Textuals 1) (Details) (USD $)
3 Months Ended 12 Months Ended
Mar. 31, 2012
Dec. 31, 2011
Debt Instrument [Line Items]    
Upsize Facility Total $ 300,000,000  
Power generation capacity 11,392 11,391
Debt Disclosure [Abstract]    
Early Repayment of Senior Debt   1,200,000,000
Term loan interest rate spread option Federal Funds effective rate 0.50%  
Term loan interest rate spread option Prime Rate 2.25%  
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum 3.25%  
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum 1.25%  
Percentage of principal amount of Term Loan to be paid quarterly 0.25%  
Repricing transaction premium percentage 1.00%  
Percentage of Term Loan amounts held by lenders 50.00%  
Percentage added to Federal Funds Effective Rate to arrive at base rate 0.50%  
Repayment time for drawings under letters of credit 2  
Excess amount of asset sales requiring mandatory prepayments $ 3,000,000,000  
Minimum [Member]
   
Debt Disclosure [Abstract]    
Applicable margin range percentage above base rate 2.00%  
Applicable Margin Range Percentage Above British Bankers' Association Interest Settlement Rates 3.00%  
Unused commitment fee range percentage 0.50%  
Maximum [Member]
   
Debt Disclosure [Abstract]    
Applicable margin range percentage above base rate 2.25%  
Applicable Margin Range Percentage Above British Bankers' Association Interest Settlement Rates 3.25%  
Unused commitment fee range percentage 0.75%  
One Month [Member]
   
Debt Disclosure [Abstract]    
Interest periods for LIBOR rate borrowings 1  
Two Months [Member]
   
Debt Disclosure [Abstract]    
Interest periods for LIBOR rate borrowings 2  
Three Months [Member]
   
Debt Disclosure [Abstract]    
Interest periods for LIBOR rate borrowings 3  
Six Months [Member]
   
Debt Disclosure [Abstract]    
Interest periods for LIBOR rate borrowings 6  
Nine Months [Member]
   
Debt Disclosure [Abstract]    
Interest periods for LIBOR rate borrowings 9  
Twelve Months [Member]
   
Debt Disclosure [Abstract]    
Interest periods for LIBOR rate borrowings 12