Note 4 - Investment Securities (Details Textual) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($) shares	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) shares	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Debt Securities, Trading	$ 2,708		$ 2,708		$ 0
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest	137		137		213
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		1,500
Debt Securities, Held-to-Maturity, Accrued Interest, after Allowance for Credit Loss	900		900		1,400
Proceeds from Sale of Debt Securities, Available-for-Sale	0	$ 0	0	$ 0
Proceeds from Sale of Held-to-Maturity Securities	0	0	0	$ 0
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	282,050		282,050
Debt Securities, Held-to-Maturity, Nonaccrual	0		0		0
Debt Securities, Held-to-Maturity, Nonaccrual, Interest Income		$ 0
Investment, Tax Basis, Cost	$ 0		$ 0		0
Preferred Class B [Member]
Investment Owned, Balance, Shares (in shares) | shares	6,924		6,924
Common Class A [Member]
Investment Owned, Balance, Shares (in shares) | shares	10,992		10,992
Visa Class B Restricted Shares to Class A Common Shares [Member]
Preferred Stock, Convertible, Conversion Ratio	1.5875		1.5875
Asset Pledged as Collateral [Member] | Deposits [Member]
Debt Securities, Available-for-Sale, Restricted	$ 335,900		$ 335,900		250,000
Financial Asset, Past Due [Member]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss	$ 0		$ 0		$ 0