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Impairment of Natural Gas and Crude Oil Properties (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Impairment of natural gas and crude oil properties [Line Items]        
Impairment of proved ad unproved properties $ 27,463 $ 1,084 $ 29,565 $ 2,053
Amortization of Individually Insignificant Unproved Properties 103 54 194 86
Impairment of Oil and Gas Properties 27,566 1,138 29,759 2,139
Land and buildings 0 3,032 0 3,032
Impairment of properties and equipment $ 27,566 $ 4,170 $ 29,759 $ 5,171