Loans (Loans) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 42,135.2	$ 47,617.0
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	20,834.0	25,412.8
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	10,812.1	11,555.3
Commercial | Commercial and Institutional | Private Equity Funds
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	4,300.0	4,500.0
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	5,266.8	5,134.2
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	2,464.0	2,778.5
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	2,291.1	5,944.8
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	21,301.2	22,204.2
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	14,416.5	14,360.0
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,209.0	6,327.1
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	437.8	428.8
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 237.9	$ 1,088.3