Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 1,393	$ 1,122	$ 4,182
Purchase commitment, cancelling excess amount committed	4,300
Research and Development Expense [Member]
Property, Plant and Equipment [Line Items]
Purchase commitment, cancelling excess amount committed	28,900
Research and Development Expense [Member] | Biogen Collaboration Agreement [Member]
Property, Plant and Equipment [Line Items]
Reimbursement expense	$ 14,500
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	3 years
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, useful life	5 years