Income Taxes - Summary of Income Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal	$ (9,531)	$ (9,920)	$ 983
State	1,816	(1,848)	(1,397)
Total	(7,715)	(11,768)	(414)
Deferred
Federal	(313,938)	(218,357)	(72,869)
State	(7,175)	(12,350)	(99)
Total	(321,113)	(230,707)	(72,968)
Income tax (benefit) expense	$ (328,828)	$ (242,475)	$ (73,382)