Note 5 - Debt Securities (Details Textual)	3 Months Ended
	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Accrued Interest Receivable Debt Securities Available for Sale	$ 2,900,000		$ 3,100,000
Debt Securities, Available-for-Sale, Total	490,271,000		502,762,000	[1]
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0
Accrued Interest Receivable Debt Securities Held to Maturity	937,000		1,100,000
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	93,737,000		94,227,000	[1]
Debt Securities, Held-to-Maturity, Nonaccrual	0		0
Debt Securities, Held-to-Maturity, 30 Days or More Past Due, Still Accruing	0		0
Proceeds from Maturities, Prepayments and Calls of Held-to-Maturity Securities	0	$ 0
Debt Securities, Held-to-Maturity, Allowance for Credit Loss	$ 0		$ 0	[1]
Debt Securities, Available-for-Sale [Member]
State and Political Subdivisions Securities Number of States with Highest Volume	5
US States and Political Subdivisions Debt Securities [Member] | Securities Issuers Concentration Risk [Member] | Securities, Total [Member]
Debt Securities, Available-for-Sale, Total	$ 0
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	$ 0
Debt Securities, Held-to-Maturity [Member]
State and Political Subdivisions Securities Number of States with Highest Volume	5

[1] Derived from audited consolidated financial statements.