Balance Sheet Details (Composition of Property and Equipment) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Property, plant and equipment, gross	$ 2,031,000	$ 1,986,000
Less: accumulated depreciation and amortization	(1,528,000)	(1,170,000)
Property and equipment, net	503,000	816,000
Laboratory Equipment [Member]
Property, plant and equipment, gross	1,771,000	1,727,000
Office and Computer Equipment [Member]
Property, plant and equipment, gross	72,000	71,000
Leasehold Improvements [Member]
Property, plant and equipment, gross	$ 188,000	$ 188,000