Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net Income (Loss) Attributable to Parent [Abstract]
Net income (loss)	$ 9,782	$ (40,264)
Other comprehensive income (loss)
Reclassification adjustment for hedge (gains) losses included in net income (loss)	(12,423)	6,755
Income tax expense (benefit) related to other comprehensive income (loss)	4,744	(2,568)
Other comprehensive income (loss), net of tax	(7,679)	4,187
Comprehensive income (loss)	$ 2,103	$ (36,077)