Evangeline Transactions (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Mar. 02, 2010	Feb. 26, 2010	Feb. 25, 2010	Feb. 22, 2010
Bonds Transferred from JPMVEC to Evangeline [Abstract]
Senior Secured bonds transferred and retired						$ 126,600,000
Stated interest rate of bonds transferred and retired (in hundredths)						8.82%
Accrued interest on transferred bonds eliminated						5,300,000
Payment by JPMVEC to Evangeline							56,700,000
Cancellation of letter of credit				15,000,000
Gain recorded on termination of operating lease	0	148,402,000	0
Redemption of remaining bonds [Abstract]
Face amount of remaining Senior Secured bonds						35,200,000
Accrued interest paid to debtholders						1,500,000
Make-whole payment on bond redemption						10,200,000
Deferred debt issuance costs						2,100,000
Restricted cash released upon redemption of bonds					$ 30,100,000
Short-term RFP [Member]
Servicing Assets at Fair Value [Line Items]
Capacity and energy	250
Long-term RFP [Member]
Servicing Assets at Fair Value [Line Items]
Capacity and energy	730