Investments Remaining Contractual Maturity of Secruity Lending Agreements (Details) - Overnight and Continuous - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	$ 25.8	$ 63.1
Securities Loaned and Securities Sold under Agreement to Repurchase, Gross Including Not Subject to Master Netting Arrangement	25.8	63.1
Secured Borrowings, Gross, Difference, Amount	0.0	0.0
Public Utilities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	3.7	1.8
All Other Corporate Bonds
Transfer of Certain Financial Assets Accounted for as Secured Borrowings
Securities Loaned, Including Not Subject to Master Netting Arrangement and Assets other than Securities Transferred	$ 22.1	$ 61.3

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Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and financial assets transferred other than securities that qualify as secured borrowings.

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