Summary of Significant Accounting Policies (Comprehensive (Loss) Earnings) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Comprehensive earnings (loss):
Net (loss) earnings	$ (414,733)	$ 134,001	$ 105,166	$ (52,497)	$ (21,145)	$ (3,023)	$ 89,023	$ 17,669	$ (228,063)	$ 82,524	$ 54,030
Unrealized gain (loss) on derivatives, net of income taxes of $0, $0, and ($79,240), respectively									0	0	(129,287)
Reclassification of realized (gain) loss on derivatives included in net income, net of income taxes of $0, $0, ($27,447)									0	0	(44,782)
Amortization of Accumulated other comprehensive loss related to de-designated hedges, net of taxes of $23,467, $10,153, and $0, respectively									38,289	16,566
Total comprehensive (loss) earnings									(189,774)	99,090	(120,039)
Unrealized gains (losses) on derivatives, income tax expense (benefit)									0	0	(79,240)
Reclassifications of realized (gain) loss on derivatives included in Net (loss) earnings, income tax expense (benefit)									0	0	(27,447)
Amortization of Accumulated other comprehensive loss related to de-designated hedges, income tax benefit									$ 23,467	$ 10,153	$ 0