Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (8,099)	$ (7,139)	[1]
Other comprehensive loss
Foreign currency translation adjustment	20
Unrealized gain (loss) on available-for-sale securities	37	(23)
Total comprehensive loss	$ (8,042)	$ (7,162)

[1] See Note 1 for a summary of adjustments