Other Assets - Affordable Housing and Other Tax Credit Investment Partnerships (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Affordable housing and other tax credit investment partnership interests
Affordable housing tax credits and other benefits recognized	$ 31.1	$ 26.9	$ 22.7
Provision for income taxes
Affordable housing and other tax credit investment partnership interests
Amortization	23.5	24.4	$ 21.7
Included in other assets
Affordable housing and other tax credit investment partnership interests
Investment partnership interest	$ 206.9	$ 167.4

Amount of affordable housing tax credits and other tax benefits recognized.

Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 323
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481543/323-740-50-2

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- Definition

Amount of investment in qualified affordable housing projects.

+ References

Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 323
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481543/323-740-50-2

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- Definition

Amount of amortization expense of investment in qualified affordable housing projects.

+ References

Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 323
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481543/323-740-50-2

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