Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (5,430)	$ (1,427)	$ (9,977)	$ (3,895)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	(2)		2
Total comprehensive loss	$ (5,432)	$ (1,427)	$ (9,975)	$ (3,895)