Note 4 - Investment Securities - Temporarily Impaired Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Temporarily impaired securities, less than 12 months, fair value	$ 1,278,577	$ 1,041
Temporarily impaired securities, less than 12 months, unrealized losses	1,935	1
Temporarily impaired securities, 12 months or longer, fair value	356,345	703,902
Temporarily impaired securities, 12 months or longer, unrealized losses	52,839	78,369
Temporarily impaired securities, total fair value	1,634,922	704,943
Temporarily impaired securities, total unrealized losses	54,774	78,370
Temporarily impaired securities, 12 months or longer, fair value	356,345	703,902
US Treasury Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	936,464
Temporarily impaired securities, less than 12 months, unrealized losses	312
Temporarily impaired securities, 12 months or longer, fair value	0
Temporarily impaired securities, 12 months or longer, unrealized losses	0
Temporarily impaired securities, total fair value	936,464
Temporarily impaired securities, total unrealized losses	312
Temporarily impaired securities, 12 months or longer, fair value	0
US Government Corporations and Agencies Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	0	834
Temporarily impaired securities, less than 12 months, unrealized losses	0	1
Temporarily impaired securities, 12 months or longer, fair value	979	3,585
Temporarily impaired securities, 12 months or longer, unrealized losses	107	117
Temporarily impaired securities, total fair value	979	4,419
Temporarily impaired securities, total unrealized losses	107	118
Temporarily impaired securities, 12 months or longer, fair value	979	3,585
Collateralized Mortgage-Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	342,113	207
Temporarily impaired securities, less than 12 months, unrealized losses	1,623	0
Temporarily impaired securities, 12 months or longer, fair value	295,958	600,658
Temporarily impaired securities, 12 months or longer, unrealized losses	51,322	75,324
Temporarily impaired securities, total fair value	638,071	600,865
Temporarily impaired securities, total unrealized losses	52,945	75,324
Temporarily impaired securities, 12 months or longer, fair value	295,958	600,658
Collateralized Mortgage Obligations [Member]
Temporarily impaired securities, less than 12 months, fair value	0	0
Temporarily impaired securities, less than 12 months, unrealized losses	0	0
Temporarily impaired securities, 12 months or longer, fair value	4,624	22,747
Temporarily impaired securities, 12 months or longer, unrealized losses	1,194	1,706
Temporarily impaired securities, total fair value	4,624	22,747
Temporarily impaired securities, total unrealized losses	1,194	1,706
Temporarily impaired securities, 12 months or longer, fair value	4,624	22,747
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	0	0
Temporarily impaired securities, less than 12 months, unrealized losses	0	0
Temporarily impaired securities, 12 months or longer, fair value	54,784	76,912
Temporarily impaired securities, 12 months or longer, unrealized losses	216	1,222
Temporarily impaired securities, total fair value	54,784	76,912
Temporarily impaired securities, total unrealized losses	216	1,222
Temporarily impaired securities, 12 months or longer, fair value	$ 54,784	$ 76,912

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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