Note 3 - Investment Securities (Details Textual) $ in Thousands	3 Months Ended
Mar. 31, 2025 USD ($) shares	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)
Debt Securities, Trading	$ 3,047		$ 3,309
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	129		131
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	0
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss	2,000		2,000
Debt Securities, Held-to-Maturity, Accrued Interest, after Allowance for Credit Loss	900		1,300
Proceeds from Sale of Debt Securities, Available-for-Sale	0	$ 0
Proceeds from Calls and Sale of Debt Securities, Available-for-Sale	10,000	0
Proceeds from Sale of Held-to-Maturity Securities	0	0
Debt Securities, Held-to-Maturity, Nonaccrual	0		0
Debt Securities, Held-to-Maturity, Nonaccrual, Interest Income	0	$ 0
Debt Securities, Available-for-Sale and Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	920,764		$ 962,272
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	$ 0
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, Excluding Accrued Interest, before Allowance for Credit Loss	$ 268,760
Financial Asset, Past Due [Member]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	$ 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	$ 509,400		$ 340,200

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