Note 4 - Investment Securities (Details Textual) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Proceeds from Sale of Debt Securities, Available-for-Sale	$ 0	$ 0	$ 0	$ 0
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss	839,000		839,000		$ 810,000
Debt Securities, Available-for-Sale, Realized Gain (Loss)	0	$ 0	0	$ 0
Equity Securities without Readily Determinable Fair Value, Downward Price Adjustment, Annual Amount			22,200,000		22,200,000
Asset Pledged as Collateral [Member]
Financial Instruments, Owned, at Fair Value	93,100,000		93,100,000
Asset Pledged as Collateral [Member] \| Deposits [Member]
Financial Instruments, Owned, at Fair Value	$ 63,000		$ 63,000		$ 76,000

Amount, after allowance for credit loss, of accrued interest on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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The aggregate fair value as of the balance sheet date of financial instruments and other positions owned by the entity including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Includes both pledged and unpledged holdings.

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