Income Taxes - Income Tax Benefit (Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current (expense) benefit:
State	$ (85)	$ (6)	$ (32)
International	55	(22)	(23)
Deferred (expense) benefit:
Federal	(22)
State	(5)
International	94	38
Total income tax benefit (expense)	$ 37	$ 10	$ (55)