Investment Securities - Fair Value of Investments In Private Equity Funds Subject to Lock-Up Periods (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Debt and Equity Securities, FV-NI [Line Items]
1 – 3 years	$ 48.5
3 – 5 years	7.4
5 – 10 years	201.2
>10 years	0.0
Total	3,417.5	$ 2,958.5
Private equity funds
Debt and Equity Securities, FV-NI [Line Items]
Total	$ 257.1

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.

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