Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (22,748)	$ (16,486)	$ (64,683)	$ (56,290)
Change in unrealized gain on short-term investments	13	12	257	45
Comprehensive loss	$ (22,735)	$ (16,474)	$ (64,426)	$ (56,245)