Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (20,307)	$ (18,033)	$ (45,355)	$ (58,179)
Other comprehensive income (loss):
Foreign currency translation adjustment	(10)	5	(4)	5
Unrealized gain (loss) on marketable securities	1	(24)	(5)	(36)
Total comprehensive loss	$ (20,316)	$ (18,052)	$ (45,364)	$ (58,210)