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Note 4 - Balance Sheet Components (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Accounts Receivable, Allowance for Credit Loss, Current	$ 0		$ 0		$ 0
Depreciation, Total	125,000	$ 121,000	255,000	$ 219,000
Impairment of Property and Equipment			0	0
Amortization of Intangible Assets, Total	675,000	805,000	1,454,000	1,218,000
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)		1,600,000		$ 1,600,000
In Process Research and Development 1 [Member]
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)		$ 1,600,000
Intellectual Property [Member]
Finite-Lived Intangible Asset, Useful Life			20 years
Minimum [Member]
Finite-Lived Intangible Asset, Useful Life			1 year 109 days
Maximum [Member]
Finite-Lived Intangible Asset, Useful Life			11 years 273 days