Balance Sheet Components - Components of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 45,305	$ 34,096
Less: accumulated depreciation and amortization	(12,530)	(7,632)
Total property and equipment, net	32,775	26,464
Laboratory and manufacturing equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	4,783	4,238
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,452	2,315
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	3,822	3,669
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	9,145	7,597
Internal-use software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 25,103	$ 16,277