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Property and Equipment - Components of Property and Equipment (Detail) - USD ($)
$ in Thousands
Sep. 30, 2015
Dec. 31, 2014
Property, Plant and Equipment [Abstract]    
Proved oil and gas properties, at cost $ 392,160 $ 396,588
Less: Accumulated depletion and depreciation 190,294 188,988
Oil and Gas Properties, Net 201,866 207,600
Field and office equipment 28,313 27,403
Less: Accumulated depreciation 16,603 14,702
Field and Office Equipment, Net 11,710 12,701
Total Property and Equipment, Net $ 213,576 $ 220,301