Balance Sheet Account Details (Property and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 28,796	$ 28,153
Accumulated depreciation and amortization	(10,407)	(5,886)
Total property and equipment, net	18,389	22,267
Lab equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	9,665	9,047
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,598	2,573
Computer hardware
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	1,296	1,296
Software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	733	733
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 14,504	$ 14,504