Balance Sheet Details (Property and Equipment) (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 10,345,000	$ 11,143,000
Less: accumulated depreciation	(8,158,000)	(7,894,000)
Property and equipment, net	2,187,000	3,249,000
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	6,047,000	6,990,000
Office and Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	323,000	260,000
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	646,000	627,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,329,000	$ 3,266,000