Segment Information (Identifiable Assets by Business Segment) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Identifiable assets	$ 14,091.7	$ 13,995.1
Identifiable assets	87.4	84.1
Property and Casualty [Member]
Segment Reporting Information [Line Items]
Identifiable assets	14,004.3	13,911.0
Assets of Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Identifiable assets	$ 87.4	$ 84.1

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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+ Details