Property and Equipment Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 12,975	$ 12,601
Accumulated depreciation and amortization	(9,426)	(8,820)
Total property and equipment, net	3,549	3,781
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	5,678	5,638
Machinery and equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	1,603	1,351
Demonstration equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	145	123
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	794	783
Computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	591	663
Computer software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,935	2,913
Consigned equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	1,010	980
Construction-in-progress
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 219	$ 150