Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ (18)	$ 111	$ (357)
State	(13)	0	0
Foreign	0	(65)	(105)
Total current	(31)	46	(462)
Deferred:
Federal	(2)	534	0
State	0		0
Foreign	0		(1,202)
Total deferred	(2)	534	(1,202)
Income tax benefit (expense)	$ (33)	$ 580	$ (1,664)