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Asset Retirement Obligation (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Changes to the Company's asset retirement obligation liability    
Asset retirement obligation, beginning of period $ 54,970 $ 48,536
Liabilities incurred 466 756
Liabilities settled (5,002) (3,623)
Accretion expense 3,259 2,958
Revisions in estimated cash flows (11,137) 6,343
Asset retirement obligation, end of period 42,556 54,970
Less: current portion of asset retirement obligation (6,015) (2,756)
Long-term asset retirement obligation 36,541 $ 52,214
Woodford And Mississippian Lime    
Changes to the Company's asset retirement obligation liability    
Liabilities settled $ (1,800)