Annual report pursuant to Section 13 and 15(d)

Property and Equipment - Narrative (Details)

v3.8.0.1
Property and Equipment - Narrative (Details)
12 Months Ended
Dec. 31, 2017
USD ($)
usd_per_mcf
Dec. 31, 2016
USD ($)
usd_per_mcf
Dec. 31, 2015
USD ($)
usd_per_mcf
Property, Plant and Equipment [Line Items]      
Impairment of oil and natural gas properties $ 0 $ 715,495,000 $ 1,440,418,000
Cumulative capitalization of general and administrative costs incurred and capitalized to the full cost pool 165,600,000 129,900,000  
Capitalized general and administrative costs 35,700,000 29,300,000 $ 27,900,000
Capitalized costs of oil and natural gas properties excluded from amortization $ 2,912,974,000 $ 1,580,305,000  
Depletion per Mcf of gas equivalent (usd per Mcfe) | usd_per_mcf 0.90 0.92 1.68
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