Fair Value of Financial Instruments - Schedule of Change in Preferred Stock Purchase Right Liability (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Balance, December 31, 2019		$ 1,478
Change in fair value of preferred stock purchase right liability	$ (3,383)	40,163	$ (3,383)
Reclassification of preferred stock purchase right liability to equity upon issuance of convertible preferred stock		$ (41,641)