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Properties and Equipment, Net - Schedule of PPE (Details) - USD ($)
$ in Thousands
Sep. 30, 2016
Dec. 31, 2015
Property, Plant and Equipment [Abstract]    
Proved oil and gas properties $ 7,669,157 $ 8,821,146
Unproved oil and gas properties 287,007 390,434
Gathering and pipeline systems 189,393 243,672
Land, building and other equipment 81,537 117,848
Properties and equipment, gross, total 8,227,094 9,573,100
Accumulated depreciation, depletion and amortization (3,504,496) (4,596,221)
Properties and equipment, net $ 4,722,598 $ 4,976,879