Balance Sheet Components - Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 49,627	$ 47,743
Less: accumulated depreciation and amortization	(12,852)	(9,861)
Property and equipment, net	36,775	37,882
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	13,649	11,922
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	3,241	3,023
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	32,281	32,281
Construction-in-Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 456	$ 517