Balance Sheet Account Details (Property and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 28,153	$ 26,803
Accumulated depreciation and amortization	(5,886)	(2,235)
Total property and equipment, net	22,267	24,568
Lab equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	9,047	7,812
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,573	2,282
Computer hardware
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	1,296	1,238
Software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	733	619
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 14,504	$ 14,852