Balance Sheets Details - Property and Equipment, net (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment	$ 37,474	$ 37,852
Less: accumulated depreciation and amortization	(32,939)	(33,093)
Property and equipment, net	4,535	4,759
Equipment retired during period	100	300
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	21,464	21,328
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	10,730	10,359
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	3,663	3,954
Office equipment and furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	1,442	1,272
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 175	$ 939

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 of divestiture of long-lived, 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, furniture and fixtures, and computer 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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