Quarterly report pursuant to Section 13 or 15(d)

Property And Equipment (Narrative) (Details)

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Property And Equipment (Narrative) (Details) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Jun. 30, 2016
Jun. 30, 2015
Dec. 31, 2015
Property, Plant and Equipment [Line Items]          
Impairment of oil and gas properties $ 170,621,000 $ 0 $ 389,612,000 $ 0  
Cumulative capitalization of general and administrative costs incurred and capitalized to the full cost pool 115,600,000   115,600,000    
Capitalized general and administrative costs 7,900,000 $ 6,300,000 15,000,000 $ 13,500,000  
Capitalized costs of oil and natural gas properties excluded from amortization $ 1,762,439,000   $ 1,762,439,000   $ 1,817,701,000
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