Investments - Principal Investments in CLOs and Other Investments (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Debt and Equity Securities, FV-NI [Line Items]
Fair value of assets	$ 14,139.4
Level III
Debt and Equity Securities, FV-NI [Line Items]
Fair value of assets	12,280.4	$ 11,479.4
Level III \| Other
Debt and Equity Securities, FV-NI [Line Items]
Fair value of assets	33.3	37.5
CLO Senior and Subordinated Notes and Derivative Instruments
Debt and Equity Securities, FV-NI [Line Items]
Trading securities	$ 293.2	$ 349.0

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.

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading).

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+ Details