Property and Equipment - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 12,345	$ 9,795
Accumulated depreciation and amortization	(6,573)	(5,387)
Property and equipment, net	5,772	4,408
Machinery, Manufacturing and Demonstration Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	7,579	5,846
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	2,124	1,875
Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	614	374
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 2,028	$ 1,700