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Income Taxes Tax Examinations (Details) (USD $)
In Thousands, unless otherwise specified
9 Months Ended 3 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Mar. 31, 2009
Internal Revenue Service (IRS) [Member]
Mar. 31, 2008
Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]        
Unrecognized Tax Benefits, Income Tax Penalties Expense $ 4,464 $ 1,001    
Income Tax Reconciliation, Nondeductible Expense, Depletion 20,640 111,104    
Depletion 7,970   2,925 4,493
Effective Income Tax Rate Reconciliation, Deduction, Qualified Production Activity, Amount $ 957 $ 5,875 $ 1,402