Other Financial Information - Schedule of Property and Equipment, Leasehold Improvements, and Related Accumulated Depreciation and Amortization (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 12,478	$ 12,106
Less: accumulated depreciation and amortization	(10,323)	(9,601)
Property and equipment, net	2,155	2,505
Manufacturing, clinical and laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	7,500	7,325
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,727	4,450
Office furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	234	220
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 17	$ 111