Investment Securities - Investments In Private Equity Funds Subject to Lock-Up Periods (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Debt and Equity Securities, FV-NI [Line Items]
1 – 3 years	$ 57.7
3 – 5 years	8.2
5 – 10 years	157.2
>10 years	23.0
Total	2,589.2	$ 2,150.2
Private equity funds
Debt and Equity Securities, FV-NI [Line Items]
Total	$ 246.1