Revenue Recognition - Adoption of ASC 606 (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues
Oil, natural gas liquids and natural gas sales	$ 380,884	$ 249,114	$ 1,110,317	$ 644,212
Operating Costs and Expenses [Abstract]
Oil, natural gas liquids and natural gas production	55,078	44,549	165,671	129,746
Net income	(26,572)	$ (18,486)	160,617	$ 44,398
As computed under ASC 605
Revenues
Oil, natural gas liquids and natural gas sales	382,611		1,114,892
Operating Costs and Expenses [Abstract]
Oil, natural gas liquids and natural gas production	56,805		170,246
Net income	(26,572)		160,617
Accounting Standards Update 2014-09 | Increase (Decrease)
Revenues
Oil, natural gas liquids and natural gas sales	(1,727)		(4,575)
Operating Costs and Expenses [Abstract]
Oil, natural gas liquids and natural gas production	(1,727)		(4,575)
Net income	$ 0		$ 0