Note 9 - Financial and Off-balance Sheet Instruments (Details) - USD ($)	Mar. 31, 2024	Dec. 31, 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 50,963,000	$ 62,657,000
Available-for-sale	481,596,000	490,182,000
Equity securities	6,217,000	5,910,000
Restricted investment in stocks	2,730,000	2,730,000
Loans held for sale		549,000
Net loans	1,113,878,000	1,084,681,000
Mortgage servicing rights	410,000	415,000
Accrued interest receivable	6,184,000	6,101,000
Deposits	1,536,188,000	1,488,713,000
Short-term borrowings	55,088,000	94,094,000
Long-term debt	20,000,000	20,000,000
Accrued interest payable	3,806,000	5,294,000
Cash and cash equivalents	50,963,000	62,657,000
Restricted investment in stocks	2,730,000	2,730,000
Loans held for sale		560,000
Net loans	1,100,014,000	1,077,544,000
Mortgage servicing rights	594,000	585,000
Accrued interest receivable	6,184,000	6,101,000
Short-term borrowings	55,088,000	94,094,000
Long-term debt	19,858,000	19,906,000
Accrued interest payable	3,806,000	5,294,000
Fair Value, Inputs, Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Equity securities	6,217,000	5,910,000
Cash and cash equivalents	50,963,000	62,657,000
Short-term borrowings	55,088,000	94,094,000
Long-term debt	19,858,000	19,906,000
Fair Value, Inputs, Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale	481,544,000	490,130,000
Restricted investment in stocks	2,730,000	2,730,000
Accrued interest receivable	6,184,000	6,101,000
Accrued interest payable	3,806,000	5,294,000
Fair Value, Inputs, Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale	52,000	52,000
Net loans	1,100,014,000	1,077,544,000
Mortgage servicing rights	594,000	585,000
Standby Letters of Credit [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Commitments to extend credit	60,000	79,000
Standby Letters of Credit [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Commitments to extend credit	60,000	79,000
With No Stated Maturities [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deposits	1,178,711,000	1,173,732,000
Deposits	1,178,711,000	1,173,732,000
With No Stated Maturities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deposits	1,178,711,000	1,173,732,000
With Stated Maturities [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deposits	357,477,000	314,981,000
Deposits	352,960,000	311,735,000
With Stated Maturities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deposits	$ 352,960,000	$ 311,735,000