Fair Value of Financial Instruments - Schedule of Changes in the Fair Value of Level 3 Financial Instruments (Details) - Level 3 - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Redeemable Convertible Preferred Stock Warrant Liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	$ (49,293)	$ (162)
Change in the fair value included in other income (expense), net	(8,804)	(6,097)
Recognition of preferred stock warrant and tranche liability upon issuance		(691)
Private placement warrant liability acquired as part of the Merger	0
Issuance of preferred stock upon exercise of warrants	58,097
Fair Value, ending balance	0	(6,950)
Redeemable Convertible Preferred Stock Tranche Liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance		0
Recognition of preferred stock warrant and tranche liability upon issuance		(1,610)
Settlement of redeemable convertible preferred stock tranche liability due to the issuance of Series B redeemable convertible preferred stock		1,610
Fair Value, ending balance		0
Private Placement Warrant Liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	0	0
Change in the fair value included in other income (expense), net	8,398	0
Private placement warrant liability acquired as part of the Merger	(19,377)
Issuance of preferred stock upon exercise of warrants	0
Fair Value, ending balance	(10,979)	0
Derivative Liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	0	0
Change in the fair value included in other income (expense), net	0	(5,308)
Extinguishment of derivative liability upon conversion of convertible notes		5,308
Private placement warrant liability acquired as part of the Merger	0
Issuance of preferred stock upon exercise of warrants	0
Fair Value, ending balance	$ 0	$ 0