Income Taxes - Components of Income (Loss) Before Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Loss before income taxes	$ (8,137)	$ (17,286)	$ (19,566)
U.S. loss
Operating Loss Carryforwards [Line Items]
Loss before income taxes	(8,056)	(17,066)	(19,302)
Non U.S. loss
Operating Loss Carryforwards [Line Items]
Loss before income taxes	$ (81)	$ (220)	$ (264)