Balance Sheets Details (Property and Equipment, net) (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 35,482	$ 35,324
Less: accumulated depreciation and amortization	(33,181)	(32,215)
Property and equipment, net	2,301	3,109
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	20,624	20,503
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	10,395	10,369
Computer equipment and software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	3,284	3,271
Office equipment and furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,178	1,178
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1	$ 3