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	$ 111	$ (357)	$ 1,155
State	0	0	(14)
Foreign	(65)	(105)	(120)
Total current	46	(462)	1,021
Deferred:
Federal	0	0	(4,143)
State	0	0	(548)
Foreign	0	(1,202)	(87)
Total deferred	0	(1,202)	(4,778)
Income tax benefit (expense)	$ 46	$ (1,664)	$ (3,757)