Note 4 - Investment Securities - Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Temporarily impaired securities, fair value	$ 534,854	$ 551,786
Temporarily impaired securities, unrealized losses	(72,007)	(82,424)
Temporarily impaired securities, fair value, less than 12 months	13,468	10,160
Temporarily impaired securities, unrealized losses, less than 12 months	(152)	(130)
Temporarily impaired securities, fair value, 12 months or longer	521,386	541,626
Temporarily impaired securities, unrealized losses, 12 months or longer	(71,855)	(82,294)
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, fair value	37,857	40,779
Temporarily impaired securities, unrealized losses	(10,070)	(10,761)
Temporarily impaired securities, fair value, less than 12 months	0	1,689
Temporarily impaired securities, unrealized losses, less than 12 months	0	(65)
Temporarily impaired securities, fair value, 12 months or longer	37,857	39,090
Temporarily impaired securities, unrealized losses, 12 months or longer	(10,070)	(10,696)
Residential Mortgage-Backed Securities [Member]
Temporarily impaired securities, fair value	369,309	382,042
Temporarily impaired securities, unrealized losses	(43,496)	(51,433)
Temporarily impaired securities, fair value, less than 12 months	5,786	4,138
Temporarily impaired securities, unrealized losses, less than 12 months	(110)	(51)
Temporarily impaired securities, fair value, 12 months or longer	363,523	377,904
Temporarily impaired securities, unrealized losses, 12 months or longer	(43,386)	(51,382)
Commercial Mortgage-Backed Securities [Member]
Temporarily impaired securities, fair value	22,285	21,565
Temporarily impaired securities, unrealized losses	(2,768)	(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	22,285	21,565
Temporarily impaired securities, unrealized losses, 12 months or longer	(2,768)	(3,676)
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, fair value	104,497	101,189
Temporarily impaired securities, unrealized losses	(15,662)	(16,505)
Temporarily impaired securities, fair value, less than 12 months	7,682	1,340
Temporarily impaired securities, unrealized losses, less than 12 months	(42)	(7)
Temporarily impaired securities, fair value, 12 months or longer	96,815	99,849
Temporarily impaired securities, unrealized losses, 12 months or longer	(15,620)	(16,498)
Corporate Debt Securities [Member]
Temporarily impaired securities, fair value	0	4,973
Temporarily impaired securities, unrealized losses	0	(27)
Temporarily impaired securities, fair value, less than 12 months	0	2,993
Temporarily impaired securities, unrealized losses, less than 12 months	0	(7)
Temporarily impaired securities, fair value, 12 months or longer	0	1,980
Temporarily impaired securities, unrealized losses, 12 months or longer	0	(20)
Asset-Backed Securities [Member]
Temporarily impaired securities, fair value	906	1,238
Temporarily impaired securities, unrealized losses	(11)	(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	906	1,238
Temporarily impaired securities, unrealized losses, 12 months or longer	$ (11)	$ (22)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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