Note 5 - Debt Securities - Debt Securities Held to Maturity by Credit Rating (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Tax-exempt state and political subdivisions	$ 93,737	$ 94,227	[1]
Standard & Poor's, AAA Rating [Member]
Tax-exempt state and political subdivisions	14,791	14,866
Standard & Poor's, AA Rating [Member]
Tax-exempt state and political subdivisions	71,697	72,086
Standard & Poor's, A Rating [Member]
Tax-exempt state and political subdivisions	7,249	7,275
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

[1] Derived from audited consolidated financial statements.