Loans and Leases (Delinquency Status) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	$ 37,518.0	$ 31,230.6
TOTAL ACCRUAL	37,733.8	31,326.0
NONACCRUAL	103.9	83.6
Total Loans and Leases	37,837.7	31,409.6
NONACCRUAL WITH NO ALLOWANCE	85.3	70.6
Other Real Estate Owned	1.6	3.2
Total Nonaccrual Assets	105.5	86.8
30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	194.1	59.6
60 – 89 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	14.6	28.4
90 DAYS OR MORE PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	7.1	7.4
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	19,610.3	13,963.8
TOTAL ACCRUAL	19,701.2	13,990.1
NONACCRUAL	35.6	11.2
Total Loans and Leases	19,736.8	14,001.3
NONACCRUAL WITH NO ALLOWANCE	20.6	3.2
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	12,216.7	9,068.3
TOTAL ACCRUAL	12,294.4	9,083.5
NONACCRUAL	32.9	7.6
Total Loans and Leases	12,327.3	9,091.1
NONACCRUAL WITH NO ALLOWANCE	17.9	0.8
Commercial | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	3,069.3	3,089.6
TOTAL ACCRUAL	3,082.5	3,100.7
NONACCRUAL	2.7	3.6
Total Loans and Leases	3,085.2	3,104.3
NONACCRUAL WITH NO ALLOWANCE	2.7	2.4
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	3,923.0	1,576.3
TOTAL ACCRUAL	3,923.0	1,576.3
NONACCRUAL	0.0	0.0
Total Loans and Leases	3,923.0	1,576.3
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	64.8	65.6
TOTAL ACCRUAL	64.8	65.6
NONACCRUAL	0.0	0.0
Total Loans and Leases	64.8	65.6
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	336.5	164.0
TOTAL ACCRUAL	336.5	164.0
NONACCRUAL	0.0	0.0
Total Loans and Leases	336.5	164.0
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Commercial | 30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	79.8	6.4
Commercial | 30 – 59 DAYS PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	71.3	4.1
Commercial | 30 – 59 DAYS PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	8.5	2.3
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	5.4	14.0
Commercial | 60 – 89 DAYS PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	5.4	9.9
Commercial | 60 – 89 DAYS PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.0	4.1
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	5.7	5.9
Commercial | 90 DAYS OR MORE PAST DUE | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	1.0	1.2
Commercial | 90 DAYS OR MORE PAST DUE | Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	4.7	4.7
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	17,907.7	17,266.8
TOTAL ACCRUAL	18,032.6	17,335.9
NONACCRUAL	68.3	72.4
Total Loans and Leases	18,100.9	17,408.3
NONACCRUAL WITH NO ALLOWANCE	64.7	67.4
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	11,522.5	11,027.9
TOTAL ACCRUAL	11,609.4	11,070.9
NONACCRUAL	0.5	0.5
Total Loans and Leases	11,609.9	11,071.4
NONACCRUAL WITH NO ALLOWANCE	0.5	0.5
Personal | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	5,974.1	5,997.7
TOTAL ACCRUAL	6,007.0	6,023.6
NONACCRUAL	67.3	71.4
Total Loans and Leases	6,074.3	6,095.0
NONACCRUAL WITH NO ALLOWANCE	63.7	66.4
Personal | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	341.3	174.1
TOTAL ACCRUAL	346.4	174.3
NONACCRUAL	0.5	0.5
Total Loans and Leases	346.9	174.8
NONACCRUAL WITH NO ALLOWANCE	0.5	0.5
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
CURRENT	69.8	67.1
TOTAL ACCRUAL	69.8	67.1
NONACCRUAL	0.0	0.0
Total Loans and Leases	69.8	67.1
NONACCRUAL WITH NO ALLOWANCE	0.0	0.0
Personal | 30 – 59 DAYS PAST DUE
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	114.3	53.2
Personal | 30 – 59 DAYS PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	77.3	33.2
Personal | 30 – 59 DAYS PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	31.9	19.8
Personal | 30 – 59 DAYS PAST DUE | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	5.1	0.2
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	9.2	14.4
Personal | 60 – 89 DAYS PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	8.4	9.5
Personal | 60 – 89 DAYS PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.8	4.9
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	1.4	1.5
Personal | 90 DAYS OR MORE PAST DUE | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	1.2	0.3
Personal | 90 DAYS OR MORE PAST DUE | Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
PAST DUE	0.2	1.2
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