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Divestiture (Details) - USD ($)
3 Months Ended 6 Months Ended
Apr. 01, 2016
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Proceeds from sale of properties       $ 11,679,000 $ 0
Impairment   $ 23,000 $ 19,516,000 3,585,000 24,837,000
Proved Oil and Gas Properties [Member]          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Impairment   $ 0 $ 0 0 $ 0
Proved Oil and Gas Properties [Member] | Assets disposed of by sale [Member]          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Proceeds from sale of properties $ 12,200,000        
Amount of promissory note $ 4,000,000        
Interest rate of promissory note (as percent) 10.00%        
Impairment       $ 3,600,000