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Asset Retirement Obligations - Asset Retirement Obligations (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Asset Retirement Obligation [Abstract]    
Beginning of period $ 276,855 $ 257,943
Liabilities incurred 3,376 7,724
Acquisitions 13,438  
Liabilities settled (5,052) (7,965)
Disposition of wells (13,332) (8,078)
Accretion expense 25,456 14,711
Change in estimate 12,013 12,520
End of period 312,754 276,855
Less current portion (5,485) (6,327)
Long-term asset retirement obligations $ 307,269 $ 270,528