Note 4 - Balance Sheet Components (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Cash, Ending Balance			$ 66,865,000
Money Market Funds, at Carrying Value			60,005,000
Marketable Securities, Total			0
Accounts Receivable, Allowance for Credit Loss, Current	$ 0		$ 0
Depreciation, Total	75,000	$ 19,000
Impairment of Property and Equipment	0	0
Amortization of Intangible Assets, Total	$ 433,000	$ 433,000
Developed Technology Rights [Member]
Finite-Lived Intangible Asset, Remaining Life (Year)	8 years 7 months 6 days
Intellectual Property [Member]
Finite-Lived Intangible Asset, Useful Life (Year)	20 years
Finite-Lived Intangible Asset, Remaining Life (Year)	6 years 9 months
Minimum [Member] \| Developed Technology Rights [Member]
Finite-Lived Intangible Asset, Useful Life (Year)	1 year 3 months 18 days
Maximum [Member] \| Developed Technology Rights [Member]
Finite-Lived Intangible Asset, Useful Life (Year)	11 years 9 months

Amount of allowance for credit loss on accounts receivable, classified as current.

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