CONDENSED STATEMENTS OF COMPREHENSIVE LOSS - 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	$ (19,651)	$ (15,180)	$ (51,830)	$ (39,478)
Net unrealized (loss) gain on marketable securities	(19)	(42)	38	422
Comprehensive loss	$ (19,670)	$ (15,222)	$ (51,792)	$ (39,056)