Quarterly report pursuant to Section 13 or 15(d)

Property and Equipment (Narrative) (Details)

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Property and Equipment (Narrative) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Dec. 31, 2016
Property, Plant and Equipment [Line Items]          
Impairment of oil and natural gas properties $ 0 $ 170,621 $ 0 $ 389,612  
Cumulative capitalization of general and administrative costs incurred and capitalized to the full cost pool 146,600   146,600    
Capitalized general and administrative costs 8,300 $ 7,900 16,700 $ 15,000  
Capitalized costs of oil and natural gas properties excluded from amortization $ 3,109,143   $ 3,109,143   $ 1,580,305
Non-producing leases, extension term     5 years    
Minimum          
Property, Plant and Equipment [Line Items]          
Expected number of years amortization will commence     3 years    
Maximum          
Property, Plant and Equipment [Line Items]          
Expected number of years amortization will commence     5 years