Balance Sheet Details - Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 8,006	$ 7,843
Less: accumulated depreciation	(4,123)	(3,847)
Total	3,883	3,996
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,799	3,772
Manufacturing Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,017	1,017
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	906	770
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	736	736
Office Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,548	$ 1,548

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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