Balance Sheet Details - Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 7,783	$ 7,373
Less: accumulated depreciation	(3,254)	(2,694)
Total	4,529	4,679
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,760	3,457
Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,002	871
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	737	731
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	736	733
Office Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,548	$ 1,581

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.

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