Note 3 - Investment Securities (Details Textual) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025 USD ($) shares	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) shares	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Debt Securities, Trading	$ 1,686		$ 1,686		$ 3,309
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	127		127		131
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	0		0
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss	1,600		1,600		2,000
Debt Securities, Held-to-Maturity, Accrued Interest, after Allowance for Credit Loss	1,200		1,200		1,300
Proceeds from Sale of Debt Securities, Available-for-Sale	0	$ 0	0	$ 0
Proceeds from Calls of Debt Securities, Available-for-Sale	19,000	0	29,000	0
Proceeds from Sale of Held-to-Maturity Securities	0	0	0	$ 0
Debt Securities, Held-to-Maturity, Nonaccrual	0		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	884,632		884,632		$ 962,272
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	$ 0		$ 0
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Interest Receivable		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		Interest Receivable
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	$ 263,833		$ 263,833
Financial Asset, Past Due [Member]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	$ 0		$ 0		$ 0
Preferred Class B [Member] | Visa [Member]
Investment Owned, Conversion Ratio	1.5609		1.5609
Investment Owned, Balance, Shares (in shares) | shares	6,924		6,924
Investment, Tax Basis, Cost	$ 0		$ 0		0
Preferred Class A [Member] | Visa [Member]
Investment Owned, Balance, Shares (in shares) | shares	10,808		10,808
Asset Pledged as Collateral [Member] | Deposits [Member]
Debt Securities, Available-for-Sale and Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	$ 439,100		$ 439,100		$ 340,200