Income Taxes - Components of Income Tax Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current income tax expense (benefit):
Federal	$ 13,497	$ 93,540	$ 46,748
State	(619)	104	790
Total	12,878	93,644	47,538
Deferred income tax expense (benefit):
Federal	14,489	(12,219)	(7,786)
State	11,820	8,142	6,419
Total	26,309	(4,077)	(1,367)
Total income tax expense	$ 39,187	$ 89,567	$ 46,171