Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (10,088)	$ (9,467)	$ (35,496)	$ (36,765)
Change in unrealized gain or loss on short-term investments	(37)	25	19	39
Comprehensive loss	$ (10,125)	$ (9,442)	$ (35,477)	$ (36,726)