Property and Equipment - (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 26,974	$ 21,849
Less: Accumulated depreciation and amortization	(14,816)	(12,435)
Total property and equipment, net	$ 12,158	9,414
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Useful Life (Years)	5 years
Property and equipment, gross	$ 6,445	4,543
Lease and loaner instruments
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,581	3,318
Less: Accumulated depreciation and amortization	$ (1,500)	(900)
Lease and loaner instruments | Minimum
Property, Plant and Equipment [Line Items]
Useful Life (Years)	1 year
Lease and loaner instruments | Maximum
Property, Plant and Equipment [Line Items]
Useful Life (Years)	5 years
Prototype instruments
Property, Plant and Equipment [Line Items]
Useful Life (Years)	2 years
Property and equipment, gross	$ 2,975	2,956
Computer equipment
Property, Plant and Equipment [Line Items]
Useful Life (Years)	3 years
Property and equipment, gross	$ 1,592	1,847
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Useful Life (Years)	5 years
Property and equipment, gross	$ 1,642	1,390
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,878	5,874
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,861	$ 1,921