Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (16,033)	$ (12,706)	$ (37,334)	$ (41,568)
Other comprehensive (loss) income:
Unrealized (loss) gain on available-for-sale debt securities	(33)	(26)	(26)	35
Total comprehensive loss	$ (16,066)	$ (12,732)	$ (37,360)	$ (41,533)