Derivative Financial Instruments (Hedged Items In Fair Value Hedges) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Carrying value of the hedged items, available for sale debt securities	$ 7,677.5	$ 7,567.3
Cumulative hedge accounting basis adjustment, available for sale debt securities	104.1	(48.7)
Carrying value of the hedged items, senior notes and long-term subordinated debt	2,596.9	2,507.5
Cumulative hedge accounting basis adjustment, senior notes and long-term subordinated debt	(149.3)	(238.0)
Hedged asset fair value hedge discontinued cumulative increase decrease	1.4	1.8
Hedged liability fair value hedge discontinued cumulative increase decrease	$ 1.4	$ 13.8

Hedged Asset Fair Value Hedge Discontinued Cumulative Increase Decrease

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- Definition

Hedged Liability Fair Value Hedge Discontinued Cumulative Increase Decrease

+ References

No definition available.

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- References

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- Definition

Amount of asset hedged in fair value hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 181
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-181

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EE
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4EE

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk. Excludes cumulative basis adjustment related to foreign exchange risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4EE

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 181
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-181

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- Definition

Amount of liability hedged in fair value hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EE
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4EE

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- Definition

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk. Excludes cumulative basis adjustment related to foreign exchange risk.

+ References

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