Balance Sheet Details (Property and Equipment) (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 11,759,000	$ 11,102,000
Less: accumulated depreciation	(9,634,000)	(9,055,000)
Property and equipment, net	2,125,000	2,047,000
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	7,079,000	6,547,000
Office and Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	440,000	413,000
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	817,000	719,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,423,000	$ 3,423,000