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