Segment Information (Identifiable Assets by Business Segment) (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Segment Reporting Information [Line Items]
Identifiable assets	$ 17,043.7	$ 16,945.9
Identifiable assets	79.5	83.6
Property and Casualty [Member]
Segment Reporting Information [Line Items]
Segment assets	16,964.2	16,862.3
Assets of Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Identifiable assets	$ 79.5	$ 83.6

Amount of asset recognized for present right to economic benefit.

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+ Details

- Definition

Amount classified as assets attributable to disposal group held for sale or disposed of.

+ References + Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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