Loans (Loans) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 42,369.5	$ 42,893.3
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	21,609.7	21,635.6
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	12,750.2	12,415.0
Commercial | Commercial and Institutional | Private Equity Funds
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases		5,600.0	$ 5,500.0
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	4,981.4	4,773.0
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	3,004.3	3,131.1
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	873.8	1,316.5
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	20,759.8	21,257.7
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	13,865.3	14,119.0
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,377.0	6,413.5
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	429.0	510.0
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 88.5	$ 215.2