Note 4 - Investment Securities (Details Textual)	12 Months Ended
	Dec. 31, 2023 USD ($) Security	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Investment Securities [Line Items]
Proceeds from sale of investment securities	$ 33,213,000	$ 7,551,000	$ 282,000
Other than temporary impairment charges recognized for debt securities	0	0	0
Other than temporary impairment, credit losses recognized in earnings	0	0	0
Available-for-sale securities pledged as collateral	$ 289,935,000	$ 237,645,000
Debt Securities, Available-for-Sale, Restriction Type [Extensible Enumeration]	us-gaap:AssetPledgedAsCollateralMember	us-gaap:AssetPledgedAsCollateralMember
Investment equity securities	$ 5,910,000	$ 12,056,000
Unrealized (gains) losses, net of tax	(12,947,000)	77,497,000	9,375,000
Proceeds from sale of investment equity securities	8,556,000	1,594,000	7,768,000
Debt Securities [Member]
Investment Securities [Line Items]
Income tax expense (benefit) related to net realized gains (losses) on sales of securities	$ (432,000)	(29,000)	4,000
PreTSL IV [Member]
Investment Securities [Line Items]
Number of trust preferred securities | Security	1
Equity Securities [Member]
Investment Securities [Line Items]
Income tax expense (benefit) related to net realized gains (losses) on sales of securities	$ 67,000	$ (179,000)	$ 784,000