Balance Sheet Details (Property and Equipment) (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 13,691,000	$ 11,143,000
Less: accumulated depreciation	(10,259,000)	(7,894,000)
Property and equipment, net	3,432,000	3,249,000
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	9,204,000	6,990,000
Office and Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	347,000	260,000
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	627,000	627,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,513,000	$ 3,266,000