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Asset Retirement Obligations - Asset Retirement Obligations (Detail) - USD ($)
$ in Thousands
6 Months Ended
Jun. 30, 2016
Dec. 31, 2015
Asset Retirement Obligation [Abstract]    
Beginning of period $ 264,137  
Liabilities incurred 921  
Liabilities settled (5,700)  
Disposition of wells (4,731)  
Accretion expense 8,172  
Change in estimate 2,819  
End of period 265,618  
Less current portion (15,071) $ (15,071)
Long-term asset retirement obligations $ 250,547