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Note 3 - Basis of Presentation and Summary of Significant Accounting Policies (Details Textual) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Indefinite-lived Intangible Assets (Excluding Goodwill), Ending Balance | $ 8,639,000 | $ 8,639,000
Share-based Payment Arrangement, Option [Member] |  |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (Year) | 10 years |
In-Process Research and Development Asset [Member] |  |
Indefinite-lived Intangible Assets (Excluding Goodwill), Ending Balance | $ 8,600,000 | 8,600,000
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill) | $ 0 | $ 0
Minimum [Member] |  |
Property, Plant and Equipment, Useful Life (Year) | 2 years |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (Year) | 5 years 113 days | 5 years 91 days
Maximum [Member] |  |
Property, Plant and Equipment, Useful Life (Year) | 15 years |
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term (Year) | 10 years | 5 years 281 days

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