Loans and Leases (Delinquency Status) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	$ 34,016.1	$ 33,395.6
TOTAL ACCRUAL	34,220.5	33,628.0
NONACCRUAL	123.8	131.7
TOTAL LOANS AND LEASES	34,344.3	33,759.7
NONACCRUAL WITH NO ALLOWANCE	96.1	98.1
Other Real Estate Owned	1.5	0.7
Total Nonaccrual Assets	125.3	132.4
30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	165.4	209.5
60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	15.0	14.0
90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	24.0	8.9
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	15,745.9	15,038.5
TOTAL ACCRUAL	15,786.5	15,195.4
NONACCRUAL	61.4	66.6
TOTAL LOANS AND LEASES	15,847.9	15,262.0
NONACCRUAL WITH NO ALLOWANCE	42.1	41.4
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	10,024.5	9,877.0
TOTAL ACCRUAL	10,051.8	10,031.9
NONACCRUAL	21.3	26.4
TOTAL LOANS AND LEASES	10,073.1	10,058.3
NONACCRUAL WITH NO ALLOWANCE	9.9	9.1
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	3,660.5	3,516.2
TOTAL ACCRUAL	3,673.8	3,518.2
NONACCRUAL	40.1	40.2
TOTAL LOANS AND LEASES	3,713.9	3,558.4
NONACCRUAL WITH NO ALLOWANCE	32.2	32.3
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	1,771.2	1,345.7
TOTAL ACCRUAL	1,771.2	1,345.7
NONACCRUAL	0.0	0.0
TOTAL LOANS AND LEASES	1,771.2	1,345.7
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	11.3	11.4
TOTAL ACCRUAL	11.3	11.4
NONACCRUAL	0.0	0.0
TOTAL LOANS AND LEASES	11.3	11.4
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	278.4	288.2
TOTAL ACCRUAL	278.4	288.2
NONACCRUAL	0.0	0.0
TOTAL LOANS AND LEASES	278.4	288.2
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | 30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	33.8	155.7
Commercial | 30 – 59 DAYS PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	25.1	153.7
Commercial | 30 – 59 DAYS PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	8.7	2.0
Commercial | 30 – 59 DAYS PAST DUE | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Commercial | 30 – 59 DAYS PAST DUE | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Commercial | 30 – 59 DAYS PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Commercial | 60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	2.2	1.2
Commercial | 60 – 89 DAYS PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	2.2	1.2
Commercial | 60 – 89 DAYS PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Commercial | 60 – 89 DAYS PAST DUE | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Commercial | 60 – 89 DAYS PAST DUE | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Commercial | 60 – 89 DAYS PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Commercial | 90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	4.6	0.0
Commercial | 90 DAYS OR MORE PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Commercial | 90 DAYS OR MORE PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	4.6	0.0
Commercial | 90 DAYS OR MORE PAST DUE | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Commercial | 90 DAYS OR MORE PAST DUE | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Commercial | 90 DAYS OR MORE PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	18,270.2	18,357.1
TOTAL ACCRUAL	18,434.0	18,432.6
NONACCRUAL	62.4	65.1
TOTAL LOANS AND LEASES	18,496.4	18,497.7
NONACCRUAL WITH NO ALLOWANCE	54.0	56.7
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	11,912.3	11,765.4
TOTAL ACCRUAL	12,044.6	11,812.2
NONACCRUAL	2.9	2.9
TOTAL LOANS AND LEASES	12,047.5	11,815.1
NONACCRUAL WITH NO ALLOWANCE	2.9	2.9
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	5,976.1	5,946.0
TOTAL ACCRUAL	6,007.4	5,973.5
NONACCRUAL	59.5	62.2
TOTAL LOANS AND LEASES	6,066.9	6,035.7
NONACCRUAL WITH NO ALLOWANCE	51.1	53.8
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	336.5	596.7
TOTAL ACCRUAL	336.7	597.9
NONACCRUAL	0.0	0.0
TOTAL LOANS AND LEASES	336.7	597.9
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	45.3	49.0
TOTAL ACCRUAL	45.3	49.0
NONACCRUAL	0.0	0.0
TOTAL LOANS AND LEASES	45.3	49.0
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Personal | 30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	131.6	53.8
Personal | 30 – 59 DAYS PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	103.4	29.1
Personal | 30 – 59 DAYS PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	28.0	23.5
Personal | 30 – 59 DAYS PAST DUE | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.2	1.2
Personal | 30 – 59 DAYS PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Personal | 60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	12.8	12.8
Personal | 60 – 89 DAYS PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	11.1	9.9
Personal | 60 – 89 DAYS PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	1.7	2.9
Personal | 60 – 89 DAYS PAST DUE | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Personal | 60 – 89 DAYS PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Personal | 90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	19.4	8.9
Personal | 90 DAYS OR MORE PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	17.8	7.8
Personal | 90 DAYS OR MORE PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	1.6	1.1
Personal | 90 DAYS OR MORE PAST DUE | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	0.0
Personal | 90 DAYS OR MORE PAST DUE | Other
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	$ 0.0	$ 0.0