Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (9,980)	$ (6,860)	$ (6,191)
Other comprehensive income (loss):
Change in foreign currency translation adjustment	3	(2)
Comprehensive loss	$ (9,977)	$ (6,862)	$ (6,191)