Balance Sheets Details (Property and Equipment, net) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment	$ 34,729	$ 33,806
Less: accumulated depreciation and amortization	(31,977)	(31,651)
Property and equipment, net	2,752	2,155
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	19,412	18,849
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	10,466	10,395
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	3,314	3,267
Office equipment and furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	1,179	1,171
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment	$ 358	$ 124