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Oil and Gas Producing Activities - Costs Incurred Related to Oil and Gas Property Acquisition Exploration and Development Activities (Detail) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Property Acquisitions:      
Unproved property acquisitions   $ 12,972 $ 91,960
Proved property acquisitions     2,400
Development costs $ 58,587 221,265 440,848
Exploration costs   12,265 52,080
Costs incurred, acquisition of oil and gas properties, total $ 58,587 $ 246,502 $ 587,288