Loans and Leases (Loans and Leases) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 39,456.6	$ 33,759.7
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	18,445.9	15,262.0
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	11,228.4	10,058.3
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	4,333.8	3,558.4
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	2,522.9	1,345.7
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	11.0	11.4
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	349.8	288.2
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	21,010.7	18,497.7
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	14,613.8	11,815.1
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	5,857.0	6,035.7
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	371.5	597.9
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans and leases	$ 168.4	$ 49.0