Property and Equipment - Property and Equipment and Related Accumulated Depreciation and Amortization (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	$ 86,095	$ 84,570
Less: accumulated depreciation and amortization	(46,542)	(43,084)
Property and Equipment, Net	39,553	41,486
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	33,750	34,727
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	11,534	11,534
Software [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	6,177	5,429
Furniture and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	3,638	3,638
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	25,541	24,730
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment, Gross	$ 5,455	$ 4,512