Property and Equipment - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property and Equipment
Total property and equipment	$ 71,841	$ 71,591
Less accumulated depreciation	(68,716)	(68,159)
Property and equipment, net	3,125	3,432
Lab equipment and machinery
Property and Equipment
Total property and equipment	59,645	59,413
Leasehold improvements
Property and Equipment
Total property and equipment	6,429	6,420
Computer equipment and software
Property and Equipment
Total property and equipment	4,516	4,512
Furniture and fixtures
Property and Equipment
Total property and equipment	221	221
Construction in progress
Property and Equipment
Total property and equipment	$ 1,030	$ 1,025

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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