Property and Equipment - Components of Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Property Plant And Equipment [Abstract]
Proved oil and gas properties, at cost	$ 383,048	$ 364,123
Less: Accumulated depletion and depreciation	(178,437)	(169,100)
Oil and Gas Properties, Net	204,611	195,023
Field and office equipment	26,689	26,653
Less: Accumulated depreciation	(13,650)	(13,251)
Field and Office Equipment, Net	13,039	13,402
Total Property and Equipment, Net	$ 217,650	$ 208,425