Property and Equipment - (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 32,101	$ 31,305
Less: Accumulated depreciation and amortization	(16,930)	(17,248)
Total property and equipment, net	$ 15,171	14,057
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Useful Life (Years)	5 years
Property and equipment, gross	$ 10,625	8,395
Lease and loaner instruments
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,305	4,106
Less: Accumulated depreciation and amortization	$ (2,400)	(1,900)
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	$ 975	2,938
Computer equipment
Property, Plant and Equipment [Line Items]
Useful Life (Years)	3 years
Property and equipment, gross	$ 2,095	2,067
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Useful Life (Years)	5 years
Property and equipment, gross	$ 1,456	1,670
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	11,960	11,971
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 685	$ 158

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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