Note 7 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Assets [Abstract]
Other Assets	$ 347,612		$ 287,360
Investment, Proportional Amortization Method, Elected, Amount	173,000		$ 175,000
Investment Program, Proportional Amortization Method, Elected, Impairment Loss	$ 0	$ 0
Investment, Proportional Amortization Method, Elected, Statement of Financial Position [Extensible Enumeration]	Other Assets		Other Assets
Domestic Tax Jurisdiction [Member]
Open Tax Year			2019 2020 2021 2022 2023
State and Local Jurisdiction [Member]
Open Tax Year			2018 2019 2020 2021 2022 2023

Amount of impairment loss for investment that generates income tax credit and other income tax benefit under tax credit program elected to be accounted for using proportional amortization method. Includes, but is not limited to, investment under tax credit program not meeting condition for accounting under proportional amortization method.

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Amount of investment that generates income tax credit and other income tax benefit under tax credit program elected to be accounted for using proportional amortization method. Includes, but is not limited to, investment under program not meeting condition for accounting under proportional amortization method.

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Tax year that remains open to examination under enacted tax laws, in YYYY format.

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