Note 3 - Investments  | 
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| Notes to Financial Statements | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Investment [Text Block] | 
    Note 3 - Investments 
 As of December 31, 2023 the Company had two money market accounts and available-for-sale investments with contractual maturities of 90 days or less categorized as cash equivalents as follows: 
 
 
 As of December 31, 2023 , there were no available-for-sale securities in an unrealized-loss position. There were no U.S. Treasury Bills classified as Investments on the consolidated balance sheet as of December 31, 2023. 
 
 
 
 As of December 31, 2022 there were no available-for-sale securities in an unrealized-loss position and there were no sales of available-for-sale securities made during 2022. U.S. Treasury Bills classified as Investments on the consolidated balance sheet as of December 31, 2022 were $4.9 million. 
 See Note 2 for additional discussion regarding the Company’s fair value measurements. 
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