Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (50,532)	$ (21,310)
Other comprehensive gain (loss):
Unrealized loss on available-for-sale investments	(74)	(149)
Cumulative translation adjustments	(9)	(4)
Comprehensive loss	$ (50,615)	$ (21,463)