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Asset Retirement Obligations - Asset Retirement Obligations (Detail) - USD ($)
$ in Thousands
6 Months Ended
Jun. 30, 2017
Dec. 31, 2016
Asset Retirement Obligation [Abstract]    
Beginning of period $ 257,943  
Acquisition of wells 0  
Liabilities incurred 3,672  
Liabilities settled (3,103)  
Disposition of wells (2,402)  
Accretion expense 7,335  
Change in estimate 148  
End of period 263,593  
Less current portion (7,271) $ (7,271)
Long-term asset retirement obligations $ 256,322