Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (2,510)	$ (5,347)
Other comprehensive income (loss), net of tax:
Foreign currency translation gain (loss)	81
Net unrealized gain (loss) on marketable securities	(22)	(103)
Comprehensive income (loss)	$ (2,451)	$ (5,450)