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Note 3 - Short-term Investments - Short-term Investments (Details) - USD ($) $ in Thousands | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Total, amortized cost | $ 189 | $ 2,853
Total, gross unrealized gains | 4 | 19
Total, gross unrealized losses | 0 | 0
Total, fair value | 193 | 2,872
Trading Debt Securities [Member] |  |
Trading debt securities, amortized cost |  | 2,853
Trading debt securities, gross unrealized gains |  | 19
Trading debt securities, gross unrealized losses |  | 0
Trading debt securities, fair value |  | $ 2,872
Available-for-sale debt securities, amortized cost | 189 |
Available-for-sale debt securities, gross unrealized gains | 4 |
Available-for-sale debt securities, gross unrealized losses | 0 |
Available-for-sale debt securities, fair value | $ 193 |

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