Note 4 - Loans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Excluding Accrued Interest, after Allowance for Credit Loss	$ 19,936,388	$ 19,203,649
Servicing Asset	166,200	172,200
Financing Receivable, Excluding Accrued Interest, Nonaccrual	112,363	169,161
Financing Receivable, Nonaccrual, Average Recorded Investment	164,882	130,126
Financing Receivable, Nonaccrual, Interest Income	$ 5	$ 197	$ 321
Percentage Of Charge Off To Contractual Balances For Impaired Loans	14.40%	11.70%
Financing Receivable, Excluding Accrued Interest, Modified, Subsequent Default	$ 0	$ 0	$ 0
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	$ 0
Minimum [Member]
Period Loan Is In Payment Default (Day)	60 days
Maximum [Member]
Period Loan Is In Payment Default (Day)	90 days
Real Estate [Member]
Financing Receivable, Excluding Accrued Interest, Nonaccrual	$ 94,900	115,200
Residential Portfolio Segment [Member]
Servicing Asset	54,300	63,300
Repossessed Assets	8,800	6,700
Commercial Portfolio Segment [Member]
Servicing Asset	52,700	41,800
Financing Receivable, Nonaccrual, Average Recorded Investment	47,168	27,236
Financing Receivable, Nonaccrual, Interest Income	5	1
Commercial Real Estate Portfolio Segment [Member]
Servicing Asset	49,000	44,500
Financing Receivable, Nonaccrual, Average Recorded Investment	88,813	66,634
Financing Receivable, Nonaccrual, Interest Income	0	196
Commercial Construction Loans [Member]
Servicing Asset	10,200	22,600
Real Estate Loan [Member] \| Asset Pledged as Collateral [Member] \| Federal Home Loan Bank Advances [Member]
Financing Receivable, Excluding Accrued Interest, after Allowance for Credit Loss	15,110,000	14,550,000
Commercial Loans [Member] \| Asset Pledged as Collateral [Member] \| Federal Reserve Bank’s Discount Window [Member]
Financing Receivable, Excluding Accrued Interest, after Allowance for Credit Loss	$ 1,420,000	$ 474,800

Amount of average recorded investments of financing receivable on nonaccrual status. Excludes net investment in lease.

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Percentage of charge-off to contractual balances for impaired loans.

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Period Loan Is In Payment Default

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Amortized cost excluding accrued interest, after allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

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-Topic 326
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-Section 45
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Amortized cost excluding accrued interest, of financing receivable with payment default in current period and modified within previous 12 months preceding payment default for debtor experiencing financial difficulty.

+ References

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-Topic 310
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Amortized cost excluding accrued interest, of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

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Amount of interest income on financing receivable on nonaccrual status.

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- Definition

Carrying amount as of the balance sheet date of all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings or defeasance; includes real and personal property; equity interests in corporations, partnerships, and joint ventures; and beneficial interests in trusts.

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- Definition

Amount of commitment to lend additional funds to debtor experiencing financial difficulty for which creditor has modified terms of financing receivable.

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- Definition

Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

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