Balance Sheet Account Detail - Schedule of Property and Equipment Net of Accumulated Depreciation (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 7,620	$ 7,450
(Less): Accumulated depreciation	(6,702)	(6,045)
Property and equipment, net of accumulated depreciation	918	1,405
Computers and software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	3,785	3,616
Lab and media equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	608	643
Office furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	355	344
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 2,872	$ 2,847