Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (21,418)	$ (18,019)	$ (40,146)	$ (35,186)
Other comprehensive income (loss):
Unrealized gain (loss) on marketable securities	173	54	(12)	94
Total comprehensive loss	$ (21,245)	$ (17,965)	$ (40,158)	$ (35,092)