Loans (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Note to Financial Statements
Accrued interest receivable on loans	$ 44,700		$ 45,000
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Interest and dividends receivable		Interest and dividends receivable
Allowance for credit losses - loans	$ 40,752	$ 38,729	$ 40,161	$ 40,442
Provision for credit losses	$ 600	$ 7,500
Percentage of financing receivable non-performing loans	164.10%		159.60%
Percentage of financing receivable on total loans	0.60%		0.58%