Property and Equipment - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment	$ 9,942	$ 12,588
Less accumulated depreciation and amortization	(9,689)	(12,289)
Property and equipment, net	253	299
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	4,363	4,783
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	578	1,144
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	1,446	2,138
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	1,821	2,679
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 1,734	$ 1,844