Investments - Securities Lending Transactions (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Fair value of securities lent	$ 56.4	$ 64.5
Non-cash collateral that is not permitted to be sold or repledged	3.9	4.5
Available-for-sale securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Fair value of securities lent	42.3	44.4
Equity securities
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Fair value of securities lent	14.1	20.1
Cash equivalents
Transfer of Certain Financial Assets Accounted for as Secured Borrowings [Line Items]
Fair value of cash collateral	$ 54.3	$ 61.9

Fair value of collateral permitted, by contact or custom, to be sold or re-pledged.

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 860
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-Section 55
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-URI https://asc.fasb.org/1943274/2147481395/860-30-55-4

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- Definition

The carrying value as of the balance sheet date of the assets received as collateral against securities loaned to other broker-dealers. Borrowers of securities generally are required to provide collateral to the lenders of securities, commonly cash but sometimes other securities or standby letters of credit, with a value slightly higher than that of the securities borrowed. In instances where the entity is permitted to sell or re-pledge these securities, the entity reports the fair value of the collateral received and the related obligation to return the collateral as a liability.

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