Balance Sheets Components (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 113,716	$ 61,921
Less: accumulated depreciation	(11,063)	(5,472)
Total property and equipment, net	102,653	56,449	[1]
Construction in progress
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	54,080	12,390
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	31,518	29,924
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	21,346	13,117
Computers equipment and purchased software
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	3,992	3,726
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 2,780	$ 2,764

[1] The balance sheet as of December 31, 2019 is derived from the audited financial statements as of that date.