Note 3 - Securities - Securities Available-for-sale (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Securities available-for-sale, amortized costs	$ 697,786	$ 759,917
Securities available-for-sale, gross unrealized gains	0	87
Securities available-for-sale, gross unrealized losses	79,185	103,152
Securities available-for-sale, fair values	618,601	656,852
US Government Agencies Debt Securities [Member]
Securities available-for-sale, amortized costs	353,904	391,538
Securities available-for-sale, gross unrealized gains	0	39
Securities available-for-sale, gross unrealized losses	42,060	55,002
Securities available-for-sale, fair values	311,844	336,575
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, amortized costs	179,507	190,192
Securities available-for-sale, gross unrealized gains	0	26
Securities available-for-sale, gross unrealized losses	29,614	38,018
Securities available-for-sale, fair values	149,893	152,200
Collateralized Mortgage-Backed Securities [Member]
Securities available-for-sale, amortized costs	156,875	170,694
Securities available-for-sale, gross unrealized gains	0	22
Securities available-for-sale, gross unrealized losses	6,724	9,239
Securities available-for-sale, fair values	150,151	161,477
Corporate Debt Securities [Member]
Securities available-for-sale, amortized costs	6,504	6,501
Securities available-for-sale, gross unrealized gains	0	0
Securities available-for-sale, gross unrealized losses	754	837
Securities available-for-sale, fair values	5,750	5,664
US Treasury Securities [Member]
Securities available-for-sale, amortized costs	996	992
Securities available-for-sale, gross unrealized gains	0	0
Securities available-for-sale, gross unrealized losses	33	56
Securities available-for-sale, fair values	$ 963	$ 936