Stockholders' Equity (Deficit), Convertible Preferred Stock and Tranche Liability - Reconciliation of Preferred Stock Tranche Liability Measured at Fair Value (Details) - Preferred Stock Tranche Liability $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value at issuance of Series A convertible preferred stock	$ 1,050
Change in fair value	17,030
Settlement of preferred stock tranche liability due to issuance of Milestone Shares	$ (18,080)