Note 2 - Investment Securities (Details Textual) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Oct. 31, 2021
Available-for-Sale, Securities in Unrealized Loss Positions, Depreciation from Amortized Cost Percentage		10.60%		10.60%
Held-to-maturity, Securities in Unrealized Loss Positions, Depreciation from Amortized Cost Percentage		19.70%		19.70%
Other-than-temporary Impairment Loss, Debt Securities, Available-for-sale, Total				$ 0
Debt Securities, Available-for-sale, Realized Gain					$ 12,000
Debt Securities, Available-for-sale, Realized Loss					5,000
Proceeds from Sale of Debt Securities, Available-for-Sale		$ 0	$ 0	0	1,798,000
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), Total		(229,000)	(67,000)	(265,000)	360,000
Equity Securities, FV-NI, Current		1,600,000		1,600,000		$ 1,900,000
Limited Partnership Interest, Technology Fund [Member]
Equity Securities without Readily Determinable Fair Value, Impairment Loss, Annual Amount		0	$ 0	0	$ 0
Limited Partnership Interest, Technology Fund [Member] | Other Assets [Member]
Equity Securities without Readily Determinable Fair Value, Amount							$ 1,000,000.0
Limited Partnership Interest, Technology Fund [Member] | Other Liabilities [Member]
Investment Company, Financial Commitment to Investee, Future Amount		$ 780,000		$ 780,000		$ 880,000