Note 5 - Investment Securities (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2024 USD ($) shares	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Debt Securities, Trading	$ 3,309	$ 0
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	131	213
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss		1,500
Debt Securities, Held-to-Maturity, Accrued Interest, after Allowance for Credit Loss		1,400
Proceeds from Sale of Held-to-Maturity Securities	0	0	$ 0
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	275,716
Debt Securities, Held-to-Maturity, Nonaccrual, Interest Income	0	0	0
Debt Securities, Available-for-Sale and Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	$ 962,272	$ 884,482
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Interest Receivable	Interest Receivable
Debt Securities, Held-to-Maturity, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Interest Receivable	Interest Receivable
Debt Securities, Held-to-Maturity, Nonaccrual		$ 0	$ 0
Preferred Class B [Member] \| Visa [Member]
Investment Owned, Conversion Ratio	1.5653
Investment Owned, Balance, Shares (in shares) \| shares	6,924
Investment, Tax Basis, Cost	$ 0	0
Preferred Class A [Member] \| Visa [Member]
Investment Owned, Balance, Shares (in shares) \| shares	10,838
Asset Pledged as Collateral [Member] \| Deposits [Member]
Debt Securities, Available-for-Sale and Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	$ 340,200	250,000
Financial Asset, Past Due [Member]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	0	$ 0
Available-for-sale Investment Securities [Member]
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss	2,000
Held-to-maturity Investment Securities [Member]
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss	$ 1,300

Conversion ratio for investments owned.

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Amount, after allowance for credit loss, of accrued interest on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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