Note 3 - Investment Securities - Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Temporarily impaired securities, fair value	$ 572,637	$ 551,786
Temporarily impaired securities, unrealized losses	(96,413)	(82,424)
Temporarily impaired securities, fair value, less than 12 months	58,092	10,160
Temporarily impaired securities, unrealized losses, less than 12 months	(795)	(130)
Temporarily impaired securities, fair value, 12 months or longer	514,545	541,626
Temporarily impaired securities, unrealized losses, 12 months or longer	(95,618)	(82,294)
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, fair value	57,109	40,779
Temporarily impaired securities, unrealized losses	(11,918)	(10,761)
Temporarily impaired securities, fair value, less than 12 months	19,579	1,689
Temporarily impaired securities, unrealized losses, less than 12 months	(129)	(65)
Temporarily impaired securities, fair value, 12 months or longer	37,530	39,090
Temporarily impaired securities, unrealized losses, 12 months or longer	(11,789)	(10,696)
Residential Mortgage-Backed Securities [Member]
Temporarily impaired securities, fair value	373,145	382,042
Temporarily impaired securities, unrealized losses	(60,787)	(51,433)
Temporarily impaired securities, fair value, less than 12 months	15,527	4,138
Temporarily impaired securities, unrealized losses, less than 12 months	(92)	(51)
Temporarily impaired securities, fair value, 12 months or longer	357,618	377,904
Temporarily impaired securities, unrealized losses, 12 months or longer	(60,695)	(51,382)
Commercial Mortgage-Backed Securities [Member]
Temporarily impaired securities, fair value	21,419	21,565
Temporarily impaired securities, unrealized losses	(3,697)	(3,676)
Temporarily impaired securities, fair value, less than 12 months	0	0
Temporarily impaired securities, unrealized losses, less than 12 months	0	0
Temporarily impaired securities, fair value, 12 months or longer	21,419	21,565
Temporarily impaired securities, unrealized losses, 12 months or longer	(3,697)	(3,676)
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, fair value	114,985	101,189
Temporarily impaired securities, unrealized losses	(19,977)	(16,505)
Temporarily impaired securities, fair value, less than 12 months	20,002	1,340
Temporarily impaired securities, unrealized losses, less than 12 months	(558)	(7)
Temporarily impaired securities, fair value, 12 months or longer	94,983	99,849
Temporarily impaired securities, unrealized losses, 12 months or longer	(19,419)	(16,498)
Corporate Debt Securities [Member]
Temporarily impaired securities, fair value	4,978	4,973
Temporarily impaired securities, unrealized losses	(22)	(27)
Temporarily impaired securities, fair value, less than 12 months	2,984	2,993
Temporarily impaired securities, unrealized losses, less than 12 months	(16)	(7)
Temporarily impaired securities, fair value, 12 months or longer	1,994	1,980
Temporarily impaired securities, unrealized losses, 12 months or longer	(6)	(20)
Asset-Backed Securities [Member]
Temporarily impaired securities, fair value	1,001	1,238
Temporarily impaired securities, unrealized losses	(12)	(22)
Temporarily impaired securities, fair value, less than 12 months	0	0
Temporarily impaired securities, unrealized losses, less than 12 months	0	0
Temporarily impaired securities, fair value, 12 months or longer	1,001	1,238
Temporarily impaired securities, unrealized losses, 12 months or longer	$ (12)	$ (22)