Note 5 - Financial Instruments and Fair Value Measurements - Measured on Recurring and Non Recurring Basis (Details) - USD ($)	Jun. 30, 2024	Dec. 31, 2023
Available-for-sale securities, fair market value	$ 492,762,000	$ 518,078,000
Equity Securities	3,105,000	3,132,000
US Government Agencies Debt Securities [Member]
Available-for-sale securities, fair market value	102,110,000	80,259,000
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member]
Available-for-sale securities, fair market value	102,110,000	80,259,000
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities, fair market value	0	0
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities, fair market value	102,110,000	80,259,000
US Government Agencies Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities, fair market value	0	0
Collateralized Mortgage Obligations [Member]
Available-for-sale securities, fair market value	16,591,000	8,664,000
Collateralized Mortgage Obligations [Member] | Fair Value, Recurring [Member]
Available-for-sale securities, fair market value	16,591,000	8,664,000
Collateralized Mortgage Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities, fair market value		0
Collateralized Mortgage Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities, fair market value	16,591,000	8,664,000
Collateralized Mortgage Obligations [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities, fair market value		0
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities, fair market value	289,760,000	328,908,000
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member]
Available-for-sale securities, fair market value	289,760,000	328,908,000
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities, fair market value		0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities, fair market value	289,760,000	328,908,000
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities, fair market value		0
SBA Pool [Member]
Available-for-sale securities, fair market value	989,000	1,395,000
SBA Pool [Member] | Fair Value, Recurring [Member]
Available-for-sale securities, fair market value	989,000	1,395,000
SBA Pool [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities, fair market value		0
SBA Pool [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities, fair market value	989,000	1,395,000
SBA Pool [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities, fair market value		0
Corporate Debt Securities [Member]
Available-for-sale securities, fair market value	40,067,000	43,517,000
Corporate Debt Securities [Member] | Fair Value, Recurring [Member]
Available-for-sale securities, fair market value	40,067,000	43,517,000
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities, fair market value		0
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities, fair market value	40,067,000	43,517,000
Corporate Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities, fair market value		0
Asset-Backed Securities [Member]
Available-for-sale securities, fair market value	43,245,000	55,335,000
Asset-Backed Securities [Member] | Fair Value, Recurring [Member]
Available-for-sale securities, fair market value	43,245,000	55,335,000
Asset-Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities, fair market value		0
Asset-Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities, fair market value	43,245,000	55,335,000
Asset-Backed Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities, fair market value		0
Mutual Fund [Member] | Fair Value, Recurring [Member]
Equity Securities	3,105,000	3,132,000
Mutual Fund [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Equity Securities	$ 0	0
Mutual Fund [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Equity Securities		$ 0