Allowance for Credit Losses (Accrued Interest) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Receivables [Abstract]
Loans	$ 241.7	$ 203.1
Debt Securities
Held to Maturity	72.0	63.2
Available for Sale	129.2	147.1
Other Financial Assets	86.0	43.8
Interest Receivable	$ 528.9	$ 457.2
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets
Debt Securities, Held-to-Maturity, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets