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Income Taxes (Reconciliation Of Income Tax Expense (Benefit)) (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Income Taxes [Abstract]      
Income tax expense (benefit) computed by applying the statutory rate $ 111,651 $ 83,027 $ (30,704)
State income tax, net of federal benefit 8,941 6,030 (2,409)
Statutory depletion and other 2,543 1,680 887
Total income taxes $ 123,135 $ 90,737 $ (32,226)