Annual report pursuant to Section 13 and 15(d)

Income Taxes - Narrative (Details)

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Income Taxes - Narrative (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Operating Loss Carryforwards [Line Items]      
Valuation allowance of deferred tax assets $ 298,830,000 $ 645,841,000 $ 303,246,000
Preliminary tax provision net benefit 500,000    
Impairment of oil and natural gas properties 0 $ 715,495,000 $ 1,440,418,000
Federal      
Operating Loss Carryforwards [Line Items]      
Net operating loss carryforward 574,400,000    
State      
Operating Loss Carryforwards [Line Items]      
Net operating loss carryforward 121,300,000    
Foreign Tax Authority      
Operating Loss Carryforwards [Line Items]      
Net operating loss carryforward $ 2,100,000