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Properties and Equipment, Net - Components of Net Property and Equipment (Details) - USD ($)
$ in Thousands
Dec. 31, 2018
Dec. 31, 2017
Property, Plant and Equipment [Abstract]    
Proved oil and gas properties $ 5,717,145 $ 4,932,512
Unproved oil and gas properties 194,435 190,474
Gathering and pipeline systems 83 1,569
Land, building and other equipment 94,714 82,670
Properties and equipment, gross, total 6,006,377 5,207,225
Accumulated depreciation, depletion and amortization (2,542,771) (2,135,021)
Properties and equipment, net $ 3,463,606 $ 3,072,204