Note 4 - Loans and Allowance for Loan Losses (Details Textual) - USD ($)	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Jun. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Jun. 30, 2023	Dec. 31, 2021
Mortgage Loans in Process of Foreclosure, Amount	$ 0			$ 0		$ 0
Interest Receivable	4,317,000			4,317,000		4,285,000
Financing Receivable, Nonaccrual, Interest Income	0			0
Financing Receivable, Modified in Period, Amount	0	$ 0		0	$ 0
Financing Receivable, Modified, Subsequent Default	0	0	$ 0	0
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	0			0		0
Financing Receivables, Troubled Debt Restructuring, Write-down		0			0
Impaired Financing Receivable, Interest Income, Cash Basis Method		0			0
Financing Receivable, Excluding Accrued Interest, after Allowance for Credit Loss	602,319,000			602,319,000		557,958,000
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	7,786,000	6,566,000	$ 6,394,000	7,786,000	6,566,000	6,772,000	$ 7,515,000	$ 6,083,000
Unfunded Loan Commitment [Member]
Off-Balance-Sheet, Credit Loss, Liability	131,000			131,000
Off-Balance-Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal)	0			0
Financial Asset Acquired with Credit Deterioration [Member]
Financing Receivable, Excluding Accrued Interest, after Allowance for Credit Loss	236,000			236,000		244,000
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	0	$ 0		0	$ 0	0
Accrued Interest Receivable [Member]
Interest Receivable	$ 2,100,000			2,100,000
Residential Real Estate [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Foreclosure				$ 276,000		$ 104,000