Consolidated Statements of Comprehensive Income (Loss) (Unaudited) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Consolidated Statements of Comprehensive Income (Loss) [Abstract]
Net income (loss)	$ 34,755	$ (8,168)	$ 61,015	$ 78,463
Other comprehensive (loss) income:
Realized gain on hedge derivative contract settlements reclassified into earnings from other comprehensive income, net of taxes	(16,724)	(9,602)	(55,791)	(21,726)
Change in unrealized deferred hedging gains, net of taxes	56,993	66,968	74,530	115,293
Total comprehensive income	$ 75,024	$ 49,198	$ 79,754	$ 172,030