Derivative Instruments (Details 4) (Details) (USD $)	12 Months Ended			3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2010 Interest rate contract	Dec. 31, 2011 Not Designated as Hedging Instrument Commodity contract Realized and unrealized (gain) loss on derivatives, net	Dec. 31, 2010 Not Designated as Hedging Instrument Commodity contract Realized and unrealized (gain) loss on derivatives, net	Dec. 31, 2009 Not Designated as Hedging Instrument Commodity contract Realized and unrealized (gain) loss on derivatives, net	Dec. 31, 2011 Not Designated as Hedging Instrument Commodity contract Earnings from discontinued operations	Dec. 31, 2010 Not Designated as Hedging Instrument Commodity contract Earnings from discontinued operations	Dec. 31, 2009 Not Designated as Hedging Instrument Commodity contract Earnings from discontinued operations	Dec. 31, 2011 Not Designated as Hedging Instrument Interest rate contract Realized and unrealized (gain) loss on derivatives, net	Dec. 31, 2010 Not Designated as Hedging Instrument Interest rate contract Realized and unrealized (gain) loss on derivatives, net	Dec. 31, 2009 Not Designated as Hedging Instrument Interest rate contract Realized and unrealized (gain) loss on derivatives, net
Derivative Instruments, (gain) loss
(Gain) loss recognized in earnings	$ (13,908,000)	$ 31,847,000	$ 7,756,000	$ 1,900,000	$ (13,900,000)	$ 23,200,000	$ 7,200,000	$ 0	$ 0	$ 500,000
Derivative Instruments, (Gain) Loss Reclassified from AOCL into Income, Effective Portion, Amortization of Frozen Amounts											$ 0	$ 8,600,000	$ 0