Note 4 - Investment Securities (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Security Owned and Pledged as Collateral, Fair Value, Total	$ 153,000		$ 153,000		$ 320,000
Proceeds from Sale of Debt Securities, Available-for-sale	0	$ 3,800,000	0	$ 11,661,000
Debt Securities, Available-for-sale, Realized Gain (Loss), Total	0	52,000	0	$ 210,000
Equity Securities without Readily Determinable Fair Value, Downward Price Adjustment, Annual Amount	5,000	$ 56,000	60,000
Equity Securities without Readily Determinable Fair Value, Amount	$ 14,800,000		$ 14,800,000		$ 14,900,000