Note 1 - Description of Business and Summary of Significant Accounting Policies - Held to Maturity Securities (Details) - US Treasury Securities [Member] $ in Thousands	Dec. 31, 2023 USD ($)
Held to maturity U.S. Treasury securities, amortized cost	$ 37,548
Held to maturity U.S. Treasury securities, gross unrealized gains	103
Held to maturity U.S. Treasury securities, fair value	$ 37,651