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Segment Information (Identifiable Assets by Business Segment) (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Segment Reporting Information [Line Items]
Identifiable assets	$ 16,945.9	$ 15,274.5
Identifiable assets	83.6	85.7
Property and Casualty [Member]
Segment Reporting Information [Line Items]
Identifiable assets	16,862.3	15,188.8
Assets of Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Identifiable assets	$ 83.6	$ 85.7

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Amount of asset recognized for present right to economic benefit.

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