Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (56,957)	$ (30,832)
Other comprehensive income:
Unrealized gains related to short-term investments	26
Total other comprehensive income	26
Comprehensive loss	$ (56,931)	$ (30,832)