Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (18,852)	$ (14,603)
Change in unrealized gain or loss on short-term investments	9	34
Comprehensive loss	$ (18,843)	$ (14,569)