Note 5 - Debt Securities - Debt Securities Held to Maturity by Credit Rating (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Tax-exempt state and political subdivisions	$ 96,640	$ 98,060	[1]
Standard & Poor's, AAA Rating [Member]
Tax-exempt state and political subdivisions	12,905	15,450
Standard & Poor's, AA Rating [Member]
Tax-exempt state and political subdivisions	76,324	75,119
Standard & Poor's, A Rating [Member]
Tax-exempt state and political subdivisions	7,411	7,491
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