Note 5 - Debt Securities - Debt Securities Held to Maturity by Credit Rating (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Tax-exempt state and political subdivisions	$ 94,227	$ 96,163
Standard & Poor's, AAA Rating [Member]
Tax-exempt state and political subdivisions	14,866	12,846
Standard & Poor's, AA Rating [Member]
Tax-exempt state and political subdivisions	72,086	75,932
Standard & Poor's, A Rating [Member]
Tax-exempt state and political subdivisions	7,275	7,385
Standard & Poor's, BBB Rating [Member]
Tax-exempt state and political subdivisions	0	0
Standard Poors Below Investment Grade Rating [Member]
Tax-exempt state and political subdivisions	$ 0	$ 0