Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (21,698)	$ (11,295)	$ (10,347)
Other comprehensive loss:
Unrealized loss on marketable securities	(3)	(1)
Total comprehensive loss	$ (21,701)	$ (11,296)	$ (10,347)