Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 15,517	$ 15,149
Accumulated depreciation	(13,505)	(13,106)
Property and equipment, net	2,012	2,043
Building and Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	2,050	1,917
Furniture, Fixtures and Office Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,800	1,771
Plant and Machinery
Property Plant And Equipment [Line Items]
Property and equipment, gross	9,514	9,411
Purchased Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,153	$ 2,050