Note 7 - Investment Securities - Temporarily Impaired Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Temporarily impaired securities, less than 12 months, fair value	$ 422,891	$ 59,054
Temporarily impaired securities, less than 12 months, unrealized losses	389	1,067
Temporarily impaired securities, 12 months or longer, fair value	795,682	807,644
Temporarily impaired securities, 12 months or longer, unrealized losses	102,024	120,978
Temporarily impaired securities, total fair value	1,218,573	866,698
Temporarily impaired securities, total unrealized losses	102,413	122,045
Temporarily impaired securities, 12 months or longer, fair value	795,682	807,644
US Treasury Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	394,431
Temporarily impaired securities, less than 12 months, unrealized losses	29
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	394,431
Temporarily impaired securities, total unrealized losses	29
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	3,587	4,199
Temporarily impaired securities, less than 12 months, unrealized losses	5	8
Temporarily impaired securities, 12 months or longer, fair value	3,071	2,108
Temporarily impaired securities, 12 months or longer, unrealized losses	109	119
Temporarily impaired securities, total fair value	6,658	6,307
Temporarily impaired securities, total unrealized losses	114	127
Temporarily impaired securities, 12 months or longer, fair value	3,071	2,108
Collateralized Mortgage-Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	14,888	29,955
Temporarily impaired securities, less than 12 months, unrealized losses	340	959
Temporarily impaired securities, 12 months or longer, fair value	648,958	653,236
Temporarily impaired securities, 12 months or longer, unrealized losses	95,454	112,237
Temporarily impaired securities, total fair value	663,846	683,191
Temporarily impaired securities, total unrealized losses	95,794	113,196
Temporarily impaired securities, 12 months or longer, fair value	648,958	653,236
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	24,663	24,556
Temporarily impaired securities, 12 months or longer, unrealized losses	2,286	3,191
Temporarily impaired securities, total fair value	24,663	24,556
Temporarily impaired securities, total unrealized losses	2,286	3,191
Temporarily impaired securities, 12 months or longer, fair value	24,663	24,556
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	9,985	24,900
Temporarily impaired securities, less than 12 months, unrealized losses	15	100
Temporarily impaired securities, 12 months or longer, fair value	118,990	127,744
Temporarily impaired securities, 12 months or longer, unrealized losses	4,175	5,431
Temporarily impaired securities, total fair value	128,975	152,644
Temporarily impaired securities, total unrealized losses	4,190	5,531
Temporarily impaired securities, 12 months or longer, fair value	$ 118,990	$ 127,744

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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