Quarterly report pursuant to Section 13 or 15(d)

Property and Equipment (Narrative) (Details)

v3.10.0.1
Property and Equipment (Narrative) (Details)
 3 Months Ended 6 Months Ended
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2018
USD ($)
usd_per_mcf
Jun. 30, 2017
USD ($)
usd_per_mcf
Dec. 31, 2017
USD ($)
Property, Plant and Equipment [Line Items]          
Impairment of oil and gas properties     $ 0 $ 0  
Cumulative capitalization of general and administrative costs incurred and capitalized to the full cost pool $ 183,800,000   183,800,000    
Capitalized general and administrative costs 9,400,000 $ 8,300,000 $ 18,200,000 $ 16,700,000  
Depletion per Mcf of gas equivalent (usd per Mcfe) | usd_per_mcf     0.96 0.85  
Capitalized costs of oil and natural gas properties excluded from amortization $ 2,957,361,000   $ 2,957,361,000   $ 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