Note 4 - Investment Securities - Securities in an Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Temporarily impaired securities, fair value	$ 1,261,844	$ 600,311
Temporarily impaired securities, unrealized losses	(136,137)	(70,409)
Temporarily impaired securities, fair value, less than 12 months	854,483	119,093
Temporarily impaired securities, unrealized losses, less than 12 months	(36,526)	(410)
Temporarily impaired securities, fair value, 12 months or longer	407,361	481,218
Temporarily impaired securities, unrealized losses, 12 months or longer	(99,611)	(69,999)
US Government Agencies Debt Securities [Member]
Temporarily impaired securities, fair value	249,528	135,103
Temporarily impaired securities, unrealized losses	(16,457)	(9,669)
Temporarily impaired securities, fair value, less than 12 months	206,723	101,610
Temporarily impaired securities, unrealized losses, less than 12 months	(4,883)	(246)
Temporarily impaired securities, fair value, 12 months or longer	42,805	33,493
Temporarily impaired securities, unrealized losses, 12 months or longer	(11,574)	(9,423)
Residential Mortgage-Backed Securities [Member]
Temporarily impaired securities, fair value	784,661	331,799
Temporarily impaired securities, unrealized losses	(87,088)	(43,058)
Temporarily impaired securities, fair value, less than 12 months	514,760	5,547
Temporarily impaired securities, unrealized losses, less than 12 months	(24,763)	(45)
Temporarily impaired securities, fair value, 12 months or longer	269,901	326,252
Temporarily impaired securities, unrealized losses, 12 months or longer	(62,325)	(43,013)
Commercial Mortgage-Backed Securities [Member]
Temporarily impaired securities, fair value	29,379	26,969
Temporarily impaired securities, unrealized losses	(5,629)	(3,155)
Temporarily impaired securities, fair value, less than 12 months	5,071	5,421
Temporarily impaired securities, unrealized losses, less than 12 months	(394)	(96)
Temporarily impaired securities, fair value, 12 months or longer	24,308	21,548
Temporarily impaired securities, unrealized losses, 12 months or longer	(5,235)	(3,059)
US States and Political Subdivisions Debt Securities [Member]
Temporarily impaired securities, fair value	174,388	103,918
Temporarily impaired securities, unrealized losses	(26,346)	(14,521)
Temporarily impaired securities, fair value, less than 12 months	104,295	4,276
Temporarily impaired securities, unrealized losses, less than 12 months	(5,870)	(20)
Temporarily impaired securities, fair value, 12 months or longer	70,093	99,642
Temporarily impaired securities, unrealized losses, 12 months or longer	(20,476)	(14,501)
Corporate Debt Securities [Member]
Temporarily impaired securities, fair value	23,634	1,997
Temporarily impaired securities, unrealized losses	(616)	(3)
Temporarily impaired securities, fair value, less than 12 months	23,634	1,997
Temporarily impaired securities, unrealized losses, less than 12 months	(616)	(3)
Temporarily impaired securities, fair value, 12 months or longer	0	0
Temporarily impaired securities, unrealized losses, 12 months or longer	0	0
Asset-Backed Securities [Member]
Temporarily impaired securities, fair value	254	525
Temporarily impaired securities, unrealized losses	(1)	(3)
Temporarily impaired securities, fair value, less than 12 months	0	242
Temporarily impaired securities, unrealized losses, less than 12 months	0	0
Temporarily impaired securities, fair value, 12 months or longer	254	283
Temporarily impaired securities, unrealized losses, 12 months or longer	$ (1)	$ (3)

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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