Note 9 - Financial and Off-balance Sheet Instruments (Details) - USD ($)	Mar. 31, 2023	Dec. 31, 2022
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 14,201,000	$ 15,899,000
Available-for-sale	537,904,000	546,525,000
Equity securities	11,908,000	12,056,000
Restricted investment in stocks	2,098,000	5,193,000
Loans held for sale	388,000
Net loans	1,003,765,000	1,028,854,000
Mortgage servicing rights	460,000	469,000
Accrued interest receivable	3,425,000	5,038,000
Deposits	1,424,590,000	1,418,369,000
Short-term borrowings	110,192,000	161,327,000
Long-term debt		10,000,000
Accrued interest payable	923,000	467,000
Cash and cash equivalents	14,201,000	15,899,000
Restricted investment in stocks	2,098,000	5,193,000
Loans held for sale	389,000
Net loans	980,285,000	1,001,103,000
Mortgage servicing rights	621,000	638,000
Accrued interest receivable	3,425,000	5,038,000
Short-term borrowings	110,192,000	161,327,000
Long-term debt		10,000,000
Accrued interest payable	923,000	467,000
Fair Value, Inputs, Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Equity securities	11,908,000	12,056,000
Cash and cash equivalents	14,201,000	15,899,000
Short-term borrowings	110,192,000	161,327,000
Long-term debt		10,000,000
Fair Value, Inputs, Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale	537,852,000	546,472,000
Restricted investment in stocks	2,098,000	5,193,000
Loans held for sale	389,000
Accrued interest receivable	3,425,000	5,038,000
Accrued interest payable	923,000	467,000
Fair Value, Inputs, Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Available-for-sale	52,000	53,000
Net loans	980,285,000	1,001,103,000
Mortgage servicing rights	621,000	638,000
Standby Letters of Credit [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Commitments to extend credit	83,000	69,000
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	83,000	69,000
With No Stated Maturities [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deposits	1,174,574,000	1,242,920,000
Deposits	1,174,574,000	1,242,920,000
With No Stated Maturities [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deposits	1,174,574,000	1,242,920,000
With Stated Maturities [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deposits	250,016,000	175,449,000
Deposits	244,751,000	168,554,000
With Stated Maturities [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deposits	$ 244,751,000	$ 168,554,000