Loans (Loans) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 47,342.6	$ 47,617.0
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	25,417.1	25,412.8
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	10,980.6	11,555.3
Commercial | Commercial and Institutional | Private Equity Funds
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	5,100.0	4,500.0
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	5,333.0	5,134.2
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	2,372.7	2,778.5
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,730.8	5,944.8
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	21,925.5	22,204.2
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	14,092.2	14,360.0
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,315.2	6,327.1
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	387.2	428.8
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 1,130.9	$ 1,088.3