Balance Sheet Details (Composition of Property and Equipment) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Property, plant and equipment, gross	$ 1,986,000	$ 2,004,000
Less: accumulated depreciation and amortization	(1,170,000)	(932,000)
Property and equipment, net	816,000	1,072,000
Laboratory Equipment [Member]
Property, plant and equipment, gross	1,727,000	1,747,000
Office and Computer Equipment [Member]
Property, plant and equipment, gross	71,000	69,000
Leasehold Improvements [Member]
Property, plant and equipment, gross	$ 188,000	$ 188,000