Note 7 - Investment Securities - Temporarily Impaired Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Temporarily impaired securities, less than 12 months, fair value	$ 122,474	$ 59,054
Temporarily impaired securities, less than 12 months, unrealized losses	88	1,067
Temporarily impaired securities, 12 months or longer, fair value	761,400	807,644
Temporarily impaired securities, 12 months or longer, unrealized losses	85,626	120,978
Temporarily impaired securities, total fair value	883,874	866,698
Temporarily impaired securities, total unrealized losses	85,714	122,045
Temporarily impaired securities, 12 months or longer, fair value	761,400	807,644
US Treasury Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	108,009
Temporarily impaired securities, less than 12 months, unrealized losses	10
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	108,009
Temporarily impaired securities, total unrealized losses	10
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	4,295	4,199
Temporarily impaired securities, less than 12 months, unrealized losses	9	8
Temporarily impaired securities, 12 months or longer, fair value	2,495	2,108
Temporarily impaired securities, 12 months or longer, unrealized losses	110	119
Temporarily impaired securities, total fair value	6,790	6,307
Temporarily impaired securities, total unrealized losses	119	127
Temporarily impaired securities, 12 months or longer, fair value	2,495	2,108
Collateralized Mortgage-Backed Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	240	29,955
Temporarily impaired securities, less than 12 months, unrealized losses	0	959
Temporarily impaired securities, 12 months or longer, fair value	629,714	653,236
Temporarily impaired securities, 12 months or longer, unrealized losses	81,392	112,237
Temporarily impaired securities, total fair value	629,954	683,191
Temporarily impaired securities, total unrealized losses	81,392	113,196
Temporarily impaired securities, 12 months or longer, fair value	629,714	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	23,302	24,556
Temporarily impaired securities, 12 months or longer, unrealized losses	1,869	3,191
Temporarily impaired securities, total fair value	23,302	24,556
Temporarily impaired securities, total unrealized losses	1,869	3,191
Temporarily impaired securities, 12 months or longer, fair value	23,302	24,556
Corporate Debt Securities [Member]
Temporarily impaired securities, less than 12 months, fair value	9,930	24,900
Temporarily impaired securities, less than 12 months, unrealized losses	69	100
Temporarily impaired securities, 12 months or longer, fair value	105,889	127,744
Temporarily impaired securities, 12 months or longer, unrealized losses	2,255	5,431
Temporarily impaired securities, total fair value	115,819	152,644
Temporarily impaired securities, total unrealized losses	2,324	5,531
Temporarily impaired securities, 12 months or longer, fair value	$ 105,889	$ 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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