Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 400	$ 700	$ 3,849	$ 1,981
Decrease in gross balance of property and equipment			(1,800)
Decrease in accumulated depreciation			$ (1,800)
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
Multi-tenant Building under Operating Lease [Member]
Property, Plant and Equipment [Line Items]
Decrease in gross balance of property and equipment			$ (3,300)
Decrease in accumulated depreciation			(1,200)
Depreciated gross balance of property and equipment	2,100		2,100
Sublease Multi Tenant Building Under Operating Lease [Member]
Property, Plant and Equipment [Line Items]
Decrease in gross balance of property and equipment			(900)
Decrease in accumulated depreciation			(400)
Depreciated gross balance of property and equipment	$ 500		$ 500