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Property and Equipment - Components of Property and Equipment (Detail) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Property, Plant and Equipment [Abstract]    
Proved oil and gas properties, at cost $ 483,488 $ 476,570
Less: Accumulated depletion and depreciation (267,377) (263,569)
Oil and Gas Properties, Net 216,111 213,001
Field and office equipment 26,188 26,241
Less: Accumulated depreciation (19,417) (19,267)
Field and Office Equipment, Net 6,771 6,974
Total Property and Equipment, Net $ 222,882 $ 219,975