Property and Equipment, Net - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 29,220	$ 8,762
Less: Accumulated depreciation and amortization	(2,235)	(1,011)
Property and equipment, net	26,985	7,751
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	6,804	4,370
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	971	408
Furniture and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	788	285
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	9,965	1,856
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 10,692	$ 1,843