Note 3 - Investments  | 
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| Notes to Financial Statements | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Investment [Text Block] | 
    Note 3 - Investments 
 As of June 30, 2023, the Company had two money market accounts and available-for-sale investments with contractual maturities of one year or less as follows: 
 
 
 As of June 30, 2023, there were no available-for-sale securities in an unrealized-loss position. U.S. Treasury Bills classified as Investments on the condensed consolidated balance sheet as of June 30, 2023 were $3.0 million. 
 As of December 31, 2022 the Company had two money market accounts and available-for-sale investments with contractual maturities of one year or less as follows: 
 
 
 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 condensed 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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