Balance Sheet Components - Property and Equipment, net (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,576	$ 1,543
Less: Accumulated depreciation and amortization	(1,544)	(745)
Property and equipment, net	32	798
Equipment and Furniture [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,442	1,409
Buildings, Leasehold and Building Improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 134	$ 134

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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