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Supplemental Information on Oil and Natural Gas Operations - Unaudited - Net Costs Incurred on Unevaluated Properties (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Extractive Industries [Abstract]      
Acquisition costs evaluated during the year $ (115,767) $ (42,384) $ 30,271
Exploration costs evaluated during the year (16,315) (186,308) 188,830
Capitalized interest costs evaluated during the year 41,339 45,722 46,860
Total costs incurred during the year, net of divestitures $ (90,743) $ (182,970) $ 265,961