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Note 3 - Debt Securities Available for Sale and Held to Maturity – Schedule of Estimated Fair Value of Investment Securities Portfolio (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Debt securities available for sale, amortized cost	$ 3,447,173	$ 3,634,471
Debt securities available for sale, gross unrealized gains	1,369	790
Debt securities available for sale, gross unrealized losses	(143,218)	(239,451)
Debt securities available for sale	3,305,324	3,395,810
Held to Maturity, Amortized Cost	826,506	844,635
Held to Maturity, Gross Unrealized Gains	2,617	35
Held to Maturity, Gross Unrealized Losses	(11,935)	(36,832)
Held to Maturity, Fair Value	817,188	807,838
Total, amortized cost	4,273,679	4,479,106
Total, gross unrealized gains	3,986	825
Total, gross unrealized losses	(155,153)	(276,283)
Total, fair value	4,122,512	4,203,648
Agency Residential MBS [Member]
Debt securities available for sale, amortized cost	203,929	229,050
Debt securities available for sale, gross unrealized gains	6	1
Debt securities available for sale, gross unrealized losses	(11,445)	(17,991)
Debt securities available for sale	192,490	211,060
Held to Maturity, Amortized Cost	46,433	57,927
Held to Maturity, Gross Unrealized Gains	26	23
Held to Maturity, Gross Unrealized Losses	(2,566)	(4,218)
Held to Maturity, Fair Value	43,893	53,732
Agency Commercial MBS [Member]
Debt securities available for sale, amortized cost	398,586	7,098
Debt securities available for sale, gross unrealized gains	788	0
Debt securities available for sale, gross unrealized losses	(2,210)	(132)
Debt securities available for sale	397,164	6,966
US Government Agencies Debt Securities [Member]
Debt securities available for sale, amortized cost	313,025	311,201
Debt securities available for sale, gross unrealized gains	55	1
Debt securities available for sale, gross unrealized losses	(7,888)	(19,085)
Debt securities available for sale	305,192	292,117
US Treasury Securities [Member]
Debt securities available for sale, amortized cost		4,945
Debt securities available for sale, gross unrealized gains		10
Debt securities available for sale, gross unrealized losses		0
Debt securities available for sale		4,955
US States and Political Subdivisions Debt Securities [Member]
Debt securities available for sale, amortized cost	52,418	63,878
Debt securities available for sale, gross unrealized gains	8	9
Debt securities available for sale, gross unrealized losses	(573)	(1,701)
Debt securities available for sale	51,853	62,186
Held to Maturity, Amortized Cost	39,528	51,261
Held to Maturity, Gross Unrealized Gains	15	12
Held to Maturity, Gross Unrealized Losses	(45)	(377)
Held to Maturity, Fair Value	39,498	50,896
Corporate Debt Securities [Member]
Debt securities available for sale, amortized cost	1,917,181	2,031,144
Debt securities available for sale, gross unrealized gains	0	127
Debt securities available for sale, gross unrealized losses	(119,619)	(195,334)
Debt securities available for sale	1,797,562	1,835,937
Held to Maturity, Amortized Cost	740,545	735,447
Held to Maturity, Gross Unrealized Gains	2,576	0
Held to Maturity, Gross Unrealized Losses	(9,324)	(32,237)
Held to Maturity, Fair Value	733,797	703,210
Collateralized Debt Obligations [Member]
Debt securities available for sale, amortized cost	562,034	987,155
Debt securities available for sale, gross unrealized gains	512	642
Debt securities available for sale, gross unrealized losses	(1,483)	(5,208)
Debt securities available for sale	$ 561,063	$ 982,589

X

- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
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-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
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-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
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Amount excluding accrued interest, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
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+ References

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