Note 3 - Investment Securities (Details Textual) - USD ($)		1 Months Ended	3 Months Ended
	Mar. 31, 2022	Sep. 30, 2018	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Debt Securities, Available-for-Sale and Held-to-Maturity, Allowance for Credit Loss			$ 0
Available-for-Sale, Securities in Unrealized Loss Positions, Depreciation from Amortized Cost Percentage			8.20%
Held-to-maturity, Securities in Unrealized Loss Positions, Depreciation from Amortized Cost Percentage			24.30%
Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale, Total			$ 0
Proceeds from Sale of Debt Securities, Available-for-Sale			0	$ 0
Investment, Number of Shares Acquired (in shares)		90,000
Investment Ownership Percentage		5.00%
Payments to Acquire Other Investments		$ 1,900,000
Equity Securities, FV-NI, Unrealized Gain (Loss)			137,000	$ 63,000
Equity Securities, FV-NI, Current			1,600,000		$ 1,500,000
Limited Partnership Interest, Technology Fund [Member]
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Annual Amount	$ 0		0
Limited Partnership Interest, Technology Fund [Member] | Other Assets [Member]
Equity Securities without Readily Determinable Fair Value, Amount			1,000,000.0		1.0
Limited Partnership Interest, Technology Fund [Member] | Other Liabilities [Member]
Investment Company, Financial Support to Investee Contractually Required, Not Provided, Amount			$ 680,000		$ 780,000