Income Taxes - Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Federal:
Current	$ 2,200	$ (12)	$ 49
Deferred	15,310	(3,248)	95,259
Total Federal	17,510	(3,260)	95,308
State:
Current	(995)	(2,118)	(3,099)
Deferred (included in Federal above)	0	0	0
Total State	(995)	(2,118)	(3,099)
Total	$ (16,515)	$ 5,378	$ (92,209)