Annual report pursuant to Section 13 and 15(d)

Significant Accounting Policies - Schedule of Oil and Natural Gas Properties and Other, Net at Cost (Details)

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Significant Accounting Policies - Schedule of Oil and Natural Gas Properties and Other, Net at Cost (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Property Plant And Equipment Net [Abstract]    
Oil and natural gas properties and equipment $ 8,102,044 $ 7,932,504
Furniture, fixtures and other 21,831 20,898
Total property and equipment 8,123,875 7,953,402
Less accumulated depreciation, depletion and amortization 7,544,859 7,406,349
Oil and natural gas properties and other, net $ 579,016 $ 547,053