Balance Sheets Details - Property and Equipment, net (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment	$ 35,098	$ 33,806
Less: accumulated depreciation and amortization	(32,288)	(31,651)
Property and equipment, net	2,810	2,155
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	19,682	18,849
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	10,503	10,395
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	3,678	3,267
Office equipment and furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	1,185	1,171
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 50	$ 124