Property and Equipment - Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property and equipment [Line Items]
Property and equipment, gross	$ 35,243	$ 26,058
Less accumulated depreciation and amortization	(17,819)	(11,967)
Property and equipment, net	17,424	14,091	$ 13,985
Leasehold improvements
Property and equipment [Line Items]
Property and equipment, gross	4,804	3,393
Laboratory and clean room equipment
Property and equipment [Line Items]
Property and equipment, gross	13,787	9,982
Furniture and equipment
Property and equipment [Line Items]
Property and equipment, gross	15,145	10,483
Construction in progress
Property and equipment [Line Items]
Property and equipment, gross	$ 1,507	$ 2,200