Note 4 - Pooled Trust Preferred Securities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) Bank	Dec. 31, 2022 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Investment securities available-for-sale, amortized cost	$ 576,178	$ 649,217
Investment securities available-for-sale, debt securities	$ 490,182	$ 546,525
PreTSL IV [Member]
Schedule Of Available For Sale Securities [Line Items]
Class	Mezzanine*
Investment securities available-for-sale, amortized cost	$ 60
Investment securities available-for-sale, debt securities	52
Unrealized gains (losses)	(7)
Realized OTTI credit loss	0
Total recognized OTTI credit loss	$ (1)
Moody's ratings	Ba1
Current number of performing banks | Bank	3
Actual deferrals and defaults as a % of total collateral	0.00%
Total performing collateral as a % of outstanding bonds	305.90%