Supplemental Oil and Natural Gas Disclosure (Unaudited) - Schedule of Changes in Standardized Measure of Discounted Future Net Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Oil and Gas Exploration and Production Industries Disclosures [Abstract]
Standardized measure, beginning of year	$ 603,015	$ 554,972	$ 1,143,094
Sales, net of production costs	(295,941)	(210,354)	(222,206)
Net changes in prices and production costs related to future production	169,608	(81,456)	(621,065)
Extensions, discoveries and improved recovery, net of future production and development costs	113,199	86,606	165,020
Previously estimated development costs incurred during the period	11,118	28,909	7,084
Revisions of estimated future development costs	2,653	0	669
Revisions of previous quantity estimates, net of related costs	86,228	147,507	(67,911)
Accretion of discount	60,512	55,662	114,309
Purchases of reserves in place, less related costs	107,891	34,751	584
Other	4,366	(13,582)	35,394
Net increase (decrease) in standardized measures	259,634	48,043	(588,122)
Standardized measure, end of year	$ 862,649	$ 603,015	$ 554,972