Balance Sheets Details - Property and Equipment, net (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment	$ 37,302	$ 35,069
Less: accumulated depreciation	(32,771)	(32,254)
Property and equipment, net	4,531	2,815
Equipment retired during period	300	200
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	21,184	19,777
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	10,359	10,327
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	3,901	3,695
Office equipment and furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	1,195	1,185
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 663	$ 85

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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