Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (10,805)	$ (12,404)	$ (25,408)	$ (27,298)
Change in unrealized gain or loss on short-term investments	23	(11)	56	14
Comprehensive loss	$ (10,782)	$ (12,415)	$ (25,352)	$ (27,284)