Income Taxes - Components of Provision for (Benefit from) Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
U.S. - Federal	$ (1,269)	$ 0	$ 0
U.S. - State	96	73	86
Foreign	1,540	1,200	1,225
Total Current	367	1,273	1,311
Deferred:
Foreign	(512)	(171)	(234)
Total Deferred	(512)	(171)	(234)
Total Provision	$ (145)	$ 1,102	$ 1,077