Composition of Certain Balance Sheet Items - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Composition of Certain Balance Sheet Items [Abstract]
Machinery and equipment	$ 9,084	$ 9,078
Leasehold improvements	579	579
Purchased computer software	1,395	1,316
Build-to-suit property	51,760	51,760
Property and equipment, gross	62,818	62,733
Less: accumulated depreciation and amortization	(8,540)	(7,743)
Property and equipment, net	$ 54,278	$ 54,990

Build-to-Suit Property, Gross

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Composition of Certain Balance Sheet Items [Abstract]

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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 amortization of capitalized costs for computer software, including but not limited to, acquired and internally developed computer software.

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Amount before accumulated depreciation of additions or improvements to assets held under a lease arrangement.

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Amount before accumulated depreciation of tangible personal property used to produce goods and services, including, but is not limited to, tools, dies and molds, computer and office equipment.

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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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