Quarterly report pursuant to Section 13 or 15(d)

Property and Equipment (Narrative) (Details)

v3.8.0.1
Property and Equipment (Narrative) (Details)
3 Months Ended
Mar. 31, 2018
USD ($)
usd_per_mcf
Mar. 31, 2017
USD ($)
usd_per_mcf
Dec. 31, 2017
USD ($)
Property, Plant and Equipment [Line Items]      
Impairment of oil and natural gas properties $ 0 $ 0  
Cumulative capitalization of general and administrative costs incurred and capitalized to the full cost pool 174,400,000    
Capitalized general and administrative costs $ 8,800,000 $ 8,400,000  
Depletion per Mcf of gas equivalent (usd per Mcfe) | usd_per_mcf 0.93 0.84  
Capitalized costs of oil and natural gas properties excluded from amortization $ 2,971,119,000   $ 2,912,974,000
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