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Asset Retirement Obligations (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]    
Beginning asset retirement obligations $ 2,354 $ 6,013
Liabilities acquired 298 359
Liabilities incurred 102 77
Property dispositions (766) (4,401)
Liabilities settled (79) (9)
Accretion expense 169 434
Revision of estimates 151 (119)
Ending asset retirement obligations $ 2,229 $ 2,354