Loans (Loans) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 43,577.0	$ 42,893.3
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	21,987.3	21,635.6
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	12,061.3	12,415.0
Commercial | Commercial and Institutional | Private Equity Funds
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	4,800.0	5,600.0
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	5,063.1	4,773.0
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	2,857.8	3,131.1
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	2,005.1	1,316.5
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	21,589.7	21,257.7
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	14,068.6	14,119.0
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	6,285.8	6,413.5
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	432.6	510.0
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 802.7	$ 215.2