Investment Securities - Investments In Private Equity Funds Subject to Lock-Up Periods (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt and Equity Securities, FV-NI [Line Items]
Total	$ 1,895.8	$ 1,488.0
Private equity funds
Debt and Equity Securities, FV-NI [Line Items]
1 – 3 years	4.4
3 – 5 years	72.1
5 – 10 years	148.8
>10 years	13.9
Total	$ 239.2