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Oil and Gas Producing Activities - Capitalized Costs Related to Oil and Gas Property Acquisition Exploration and Development Activities (Detail) - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Oil And Gas Exploration And Production Industries Disclosures [Abstract]    
Unproved properties   $ 84,144
Proved properties:    
Leasehold costs $ 662,022 982,915
Wells and related equipment and facilities 3,135,079 3,349,307
Accumulated depreciation depletion and amortization (3,009,236) (3,389,786)
Capitalized costs, oil and gas producing activities, net, total $ 787,865 $ 1,026,580