Note 7 - Income Taxes (Details Textual) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2025	Dec. 31, 2024
Investment, Proportional Amortization Method, Elected, Amount	$ 198	$ 185
Investment, Proportional Amortization Method, Elected, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Domestic Tax Jurisdiction [Member]
Open Tax Year	2020 2021 2022 2023 2024
State and Local Jurisdiction [Member]
Open Tax Year	2019 2020 2021 2022 2023 2024

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.

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478156/740-323-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
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-Section 50
-Paragraph 1A
-Subparagraph (b)
-Publisher FASB
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- Definition

Indicates line item in statement of financial position that includes 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 323
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (b)
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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Subparagraph (e)
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