Property and Equipment, Net - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Furniture and fixtures	$ 504	$ 89
Building related to facility lease obligation	10,557
Leasehold improvements	1,338	692
Property, Plant and Equipment, Gross	18,728	4,095
Less: Accumulated depreciation and amortization	(2,438)	(1,751)
Property, Plant and Equipment, Net	16,290	2,344
Computer Equipment
Property, Plant and Equipment [Line Items]
Equipment	500	283
Laboratory Equipment
Property, Plant and Equipment [Line Items]
Equipment	5,723	2,995
Office Equipment
Property, Plant and Equipment [Line Items]
Equipment	$ 106	$ 36