Note 11 - Fair Values - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-Sale	$ 592,305,000	$ 602,936,000
Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-Sale	0	0
US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-Sale	384,079,000	388,744,000
Collateralized Mortgage-Backed Securities [Member]
Debt Securities, Available-for-Sale	28,016,000	31,953,000
Municipal General Obligation Bonds [Member]
Debt Securities, Available-for-Sale	153,425,000	154,433,000
Municipal Revenue Bonds [Member]
Debt Securities, Available-for-Sale	26,285,000	27,306,000
Other Debt and Equity Securities [Member]
Debt Securities, Available-for-Sale	500,000	500,000
Fair Value, Recurring [Member]
Total assets	627,365,000	628,633,000
Total liabilities	35,242,000	25,900,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Total assets	0	0
Total liabilities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Total assets	626,825,000	628,055,000
Total liabilities	35,242,000	25,900,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Total assets	540,000	578,000
Total liabilities	0	0
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Debt Securities, Available-for-Sale	384,079,000	388,744,000
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-Sale	0	0
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-Sale	384,079,000	388,744,000
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-Sale	0	0
Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member]
Debt Securities, Available-for-Sale	28,016,000	31,953,000
Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-Sale	0	0
Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-Sale	28,016,000	31,953,000
Fair Value, Recurring [Member] | Collateralized Mortgage-Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-Sale	0	0
Fair Value, Recurring [Member] | Municipal General Obligation Bonds [Member]
Debt Securities, Available-for-Sale	153,425,000	154,433,000
Fair Value, Recurring [Member] | Municipal General Obligation Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-Sale	0	0
Fair Value, Recurring [Member] | Municipal General Obligation Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-Sale	152,885,000	153,855,000
Fair Value, Recurring [Member] | Municipal General Obligation Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-Sale	540,000	578,000
Fair Value, Recurring [Member] | Municipal Revenue Bonds [Member]
Debt Securities, Available-for-Sale	26,285,000	27,306,000
Fair Value, Recurring [Member] | Municipal Revenue Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-Sale	0	0
Fair Value, Recurring [Member] | Municipal Revenue Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-Sale	26,285,000	27,306,000
Fair Value, Recurring [Member] | Municipal Revenue Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-Sale	0	0
Fair Value, Recurring [Member] | Other Debt and Equity Securities [Member]
Debt Securities, Available-for-Sale	500,000	500,000
Fair Value, Recurring [Member] | Other Debt and Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-Sale	0	0
Fair Value, Recurring [Member] | Other Debt and Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-Sale	500,000	500,000
Fair Value, Recurring [Member] | Other Debt and Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-Sale	0	0
Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Interest rate swaps	35,060,000	25,697,000
Interest rate swaps	35,242,000	25,900,000
Fair Value, Recurring [Member] | Interest Rate Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Interest rate swaps	0	0
Interest rate swaps	0	0
Fair Value, Recurring [Member] | Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Interest rate swaps	35,060,000	25,697,000
Interest rate swaps	35,242,000	25,900,000
Fair Value, Recurring [Member] | Interest Rate Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Interest rate swaps	0	0
Interest rate swaps	$ 0	$ 0