Note 4 - Loans and the Allowance for Credit Losses (Details Textual) - USD ($) $ in Thousands		12 Months Ended
Jan. 01, 2021	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		$ 8,351,841	$ 8,109,161
Financing Receivable, after Allowance for Credit Loss		$ 8,263,171	8,009,176
Allowance for Loan Losses Included in Unallocated	$ 6,600
Financing Receivable, Modified, Weighted Average Term Increase from Modification (Year)		13 years
Financing Receivable, Modified, Weighted Average Interest Rate Decrease from Modification		1.90%
Financing Receivable, Modified, Subsequent Default, Number of Contracts		0
Asset Pledged as Collateral [Member] \| Federal Home Loan Bank Advances [Member]
Financing Receivable, after Allowance for Credit Loss		$ 5,800,000	2,700,000
Commercial Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		1,578,730	1,472,734
Commercial Portfolio Segment [Member] \| Paycheck Protection Program CARES Act [Member]
Financing Receivable, before Allowance for Credit Loss, Fee and Loan in Process		$ 9,000	$ 11,000

Provision for loan losses associated with impacts of the COVID-19 pandemic.

No definition available.

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Period Type:	duration

- Definition

Number of financing receivable contracts modified within previous 12 months, with subsequent payment default.

+ References

No definition available.

+ Details

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- Definition

Amortized cost, before allowance for credit loss, fee, and loan in process, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-5

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481990/310-10-45-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(7))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of decrease in weighted average contractual interest rate of financing receivable modified for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12A
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481933/310-10-55-12A

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of increase in weighted average maturity of financing receivable modified for debtor experiencing financial difficulty, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-04(5)(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479617/946-210-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481990/310-10-45-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-5

+ Details

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- Details

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- Details

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- Details

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- Details

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