Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ (555)	$ 227	$ 551
State	(273)	587	(21)
Foreign	139	322	220
Total	(689)	1,136	750
Deferred:
Federal	(23,245)	(4,114)	(1,819)
State	(10,684)	(866)	8
Foreign	117	(342)	267
Total	(33,812)	(5,322)	(1,544)
Total income tax benefit	$ (34,501)	$ (4,186)	$ (794)