Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (6,830)	$ (21,418)	$ (25,048)	$ (40,146)
Other comprehensive income (loss):
Foreign currency translation adjustment	2		6
Unrealized (loss) gain on marketable securities	(16)	173	(6)	(12)
Total comprehensive loss	$ (6,844)	$ (21,245)	$ (25,048)	$ (40,158)