Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 15,149	$ 14,451
Accumulated depreciation	(13,106)	(12,035)
Property and equipment, net	2,043	2,416
Building and Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,917	1,884
Furniture, Fixtures and Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,771	2,002
Plant and Machinery
Property Plant And Equipment [Line Items]
Property and equipment, gross	9,411	8,848
Purchased Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,050	$ 1,717