Property and Equipment, Net - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 21,545	$ 20,325
Less: accumulated depreciation	(8,005)	(4,174)
Total property and equipment, net	$ 13,540	16,151
Laboratory equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in Years)	5 years
Property and equipment, gross	$ 10,435	9,409
Furniture and office equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in Years)	4 years
Property and equipment, gross	$ 1,071	1,038
Computer equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Life (in Years)	3 years
Property and equipment, gross	$ 1,505	1,380
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,534	$ 8,498