Note 6 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Less than 12 months, fair value	$ 36,978	$ 312,398
Less than 12 months, gross unrealized losses	1,320	20,007
12 months or greater, fair value	708,113	505,752
12 months or greater, gross unrealized losses	84,361	75,144
Total, fair value	745,091	818,150
Total, gross unrealized losses	85,681	95,151
US Treasury Securities [Member]
Less than 12 months, fair value	0	9,702
Less than 12 months, gross unrealized losses	0	374
12 months or greater, fair value	16,239	20,413
12 months or greater, gross unrealized losses	1,451	2,294
Total, fair value	16,239	30,115
Total, gross unrealized losses	1,451	2,668
US Government Agencies Debt Securities [Member]
Less than 12 months, fair value	0	24,405
Less than 12 months, gross unrealized losses	0	595
12 months or greater, fair value	9,410	22,967
12 months or greater, gross unrealized losses	848	2,321
Total, fair value	9,410	47,372
Total, gross unrealized losses	848	2,916
Corporate Debt Securities [Member]
Less than 12 months, fair value	7,529	19,564
Less than 12 months, gross unrealized losses	362	1,359
12 months or greater, fair value	36,106	6,385
12 months or greater, gross unrealized losses	5,408	1,137
Total, fair value	43,635	25,949
Total, gross unrealized losses	5,770	2,496
Collateralized Mortgage-Backed Securities [Member]
Less than 12 months, fair value	21,436	115,692
Less than 12 months, gross unrealized losses	895	7,473
12 months or greater, fair value	375,891	324,043
12 months or greater, gross unrealized losses	48,919	47,740
Total, fair value	397,327	439,735
Total, gross unrealized losses	49,814	55,213
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months, fair value	8,013	143,035
Less than 12 months, gross unrealized losses	63	10,206
12 months or greater, fair value	270,467	131,944
12 months or greater, gross unrealized losses	27,735	21,652
Total, fair value	278,480	274,979
Total, gross unrealized losses	$ 27,798	$ 31,858