Convertible Preferred Stock, Tranche Liability and Warrant Liability - Summary of the Tranche Liability and Warrant Liability Measured at Fair Value using Level 3 Significant Unobservable Inputs (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2021 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, December 31, 2020	$ 5,413
Change in fair value	81,157
Settlement of tranche liability due to issuance of Milestone Shares	(81,190)
Settlement of warrant liability upon exercise of warrant	(5,380)
Balance, June 30, 2021	0
Series A-1 Preferred Stock Warrant
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, December 31, 2020	380
Change in fair value	5,000
Settlement of warrant liability upon exercise of warrant	(5,380)
Balance, June 30, 2021	0
Series B Tranche Rights
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, December 31, 2020	5,033
Change in fair value	76,157
Settlement of tranche liability due to issuance of Milestone Shares	(81,190)
Balance, June 30, 2021	$ 0