Loans and Leases (Loans and Leases) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	$ 37,406.6	$ 33,759.7
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	16,207.7	15,262.0
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	9,833.8	10,058.3
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	3,943.9	3,558.4
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	2,091.1	1,345.7
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	11.0	11.4
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	327.9	288.2
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	21,198.9	18,497.7
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	14,636.7	11,815.1
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	6,100.6	6,035.7
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	385.5	597.9
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
TOTAL LOANS AND LEASES	$ 76.1	$ 49.0