Condensed Consolidated Statements Of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Net income (loss)	$ 59,007	$ (19,302)	$ 99,213	$ 33,137
Other comprehensive income (loss), net of taxes:
Change in value of derivative instruments used as cash flow hedges, net of tax of $3,874, $17,256, ($2,504), and $16,214	6,091	27,226	(3,820)	25,490
Reclassification - derivative settlements, net of tax of $317, ($6,106), ($1,177), and ($9,270)	506	(9,564)	(1,831)	(14,576)
Ineffective portion of derivatives, net of tax of ($667), ($537), ($141), and $232	(1,050)	(850)	(227)	374
Comprehensive income (loss)	$ 64,554	$ (2,490)	$ 93,335	$ 44,425