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Note 3 - Debt Securities Available for Sale and Held to Maturity (Details Textual) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	$ 1	$ 1	$ 1	$ 1
Total, fair value	4,122,512	4,203,648
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Nonaccrual	0
Corporate Debt Securities [Member]
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	0
Asset Pledged as Collateral [Member] | Public Deposits and Short-term Borrowed Funds [Member]
Total, fair value	$ 1,858,958	$ 2,049,954

X

- Definition

Amount, excluding accrued interest, of allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount excluding accrued interest, of investment in debt security measured at amortized cost (held-to-maturity) on nonaccrual status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-16

+ Details

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X

- Definition

Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

No definition available.

+ Details

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X

- Details

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Namespace Prefix:
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X

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

X

- Details

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