Note 3 - Investment Securities - Temporarily Impaired Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Temporarily impaired securities, less than 12 months	$ 21,690	$ 27,809
Temporarily impaired securities, total unrealized losses	(488)	(530)
Temporarily impaired securities, 12 months or longer, fair value	521,140	525,474
Temporarily impaired securities, 12 months or longer, unrealized losses	(66,975)	(73,584)
Debt Securities, Available-for-Sale, Unrealized Loss Position	542,830	553,283
Temporarily impaired securities, total unrealized losses	(67,463)	(74,114)
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, less than 12 months	14,051	14,719
Temporarily impaired securities, total unrealized losses	(441)	(318)
Temporarily impaired securities, 12 months or longer, fair value	116,155	117,168
Temporarily impaired securities, 12 months or longer, unrealized losses	(17,132)	(16,056)
Debt Securities, Available-for-Sale, Unrealized Loss Position	130,206	131,887
Temporarily impaired securities, total unrealized losses	(17,573)	(16,374)
Passthrough Mortgage Securities [Member]
Temporarily impaired securities, less than 12 months	7,639	9,364
Temporarily impaired securities, total unrealized losses	(47)	(179)
Temporarily impaired securities, 12 months or longer, fair value	120,123	119,191
Temporarily impaired securities, 12 months or longer, unrealized losses	(25,321)	(29,178)
Debt Securities, Available-for-Sale, Unrealized Loss Position	127,762	128,555
Temporarily impaired securities, total unrealized losses	(25,368)	(29,357)
Collateralized Debt Obligations [Member]
Temporarily impaired securities, less than 12 months	0	3,726
Temporarily impaired securities, total unrealized losses	0	(33)
Temporarily impaired securities, 12 months or longer, fair value	92,361	92,366
Temporarily impaired securities, 12 months or longer, unrealized losses	(19,365)	(21,517)
Debt Securities, Available-for-Sale, Unrealized Loss Position	92,361	96,092
Temporarily impaired securities, total unrealized losses	(19,365)	(21,550)
Company Agency Obligations [Member]
Temporarily impaired securities, less than 12 months	0	0
Temporarily impaired securities, total unrealized losses	0	0
Temporarily impaired securities, 12 months or longer, fair value	77,636	83,439
Temporarily impaired securities, 12 months or longer, unrealized losses	(1,022)	(1,143)
Debt Securities, Available-for-Sale, Unrealized Loss Position	77,636	83,439
Temporarily impaired securities, total unrealized losses	(1,022)	(1,143)
Corporate Bond Securities [Member]
Temporarily impaired securities, less than 12 months	0	0
Temporarily impaired securities, total unrealized losses	0	0
Temporarily impaired securities, 12 months or longer, fair value	114,865	113,310
Temporarily impaired securities, 12 months or longer, unrealized losses	(4,135)	(5,690)
Debt Securities, Available-for-Sale, Unrealized Loss Position	114,865	113,310
Temporarily impaired securities, total unrealized losses	$ (4,135)	$ (5,690)

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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