Condensed Consolidated Statements Of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Other Comprehensive Income [Abstract]
Net income	$ 34,232	$ 46,586	$ 133,445	$ 79,723
Other comprehensive income (loss), net of taxes:
Change in value of derivative instruments used as cash flow hedges, net of tax of ($3,013), ($8,838), ($5,517), and $7,377	(4,797)	(14,137)	(8,617)	11,353
Reclassification - derivative settlements, net of tax of $1,240, ($5,523), $63, and ($14,793)	1,970	(8,720)	139	(23,296)
Ineffective portion of derivatives, net of tax of $97, $1,560, ($44), and $1,792	155	2,455	(72)	2,829
Comprehensive income	$ 31,560	$ 26,184	$ 124,895	$ 70,609