Loans and Leases (Loans and Leases) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	$ 33,759.7	$ 31,409.6
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	15,262.0	14,001.3
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	10,058.3	9,091.1
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	3,558.4	3,104.3
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	1,345.7	1,576.3
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	11.4	65.6
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	288.2	164.0
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	18,497.7	17,408.3
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	11,815.1	11,071.4
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	6,035.7	6,095.0
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	597.9	174.8
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	$ 49.0	$ 67.1