Property and Equipment - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 17,633	$ 15,674
Accumulated depreciation and amortization	(11,573)	(10,968)
Property and equipment, net	6,060	4,706
Machinery, manufacturing and demonstration equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	12,398	10,421
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,317	2,321
Furniture
Property, Plant and Equipment [Line Items]
Property and equipment, gross	632	637
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 2,286	$ 2,295