Note 3 - Securities - Securities Available-for-sale (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Securities available-for-sale, amortized costs	$ 693,378	$ 697,786
Securities available-for-sale, gross unrealized gains	6	0
Securities available-for-sale, gross unrealized losses	83,416	79,185
Securities available-for-sale, fair values	609,968	618,601
US Government Agencies Debt Securities [Member]
Securities available-for-sale, amortized costs	352,961	353,904
Securities available-for-sale, gross unrealized gains	0	0
Securities available-for-sale, gross unrealized losses	44,972	42,060
Securities available-for-sale, fair values	307,989	311,844
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, amortized costs	179,343	179,507
Securities available-for-sale, gross unrealized gains	0	0
Securities available-for-sale, gross unrealized losses	31,344	29,614
Securities available-for-sale, fair values	147,999	149,893
Collateralized Mortgage-Backed Securities [Member]
Securities available-for-sale, amortized costs	153,572	156,875
Securities available-for-sale, gross unrealized gains	6	0
Securities available-for-sale, gross unrealized losses	6,255	6,724
Securities available-for-sale, fair values	147,323	150,151
Corporate Debt Securities [Member]
Securities available-for-sale, amortized costs	6,505	6,504
Securities available-for-sale, gross unrealized gains	0	0
Securities available-for-sale, gross unrealized losses	817	754
Securities available-for-sale, fair values	5,688	5,750
US Treasury Securities [Member]
Securities available-for-sale, amortized costs	997	996
Securities available-for-sale, gross unrealized gains	0	0
Securities available-for-sale, gross unrealized losses	28	33
Securities available-for-sale, fair values	$ 969	$ 963