Loans and Leases (Delinquency Status) (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	$ 30,982.3	$ 32,490.0
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	14,136.9	15,175.2
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	8,834.9	8,728.1
Commercial | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	3,248.9	3,228.8
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	1,492.7	2,701.6
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	88.5	90.7
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	471.9	426.0
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	16,845.4	17,314.8
Personal | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	6,133.0	6,514.0
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	10,637.7	10,733.3
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	74.7	67.5
Performing Financing Receivable
Financing Receivable, Credit Quality Indicator [Line Items]
Current	30,731.3	32,213.0
Total Loans and Leases	30,867.2	32,380.7
Performing Financing Receivable | 30-59 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	101.5	112.5
Performing Financing Receivable | 60-89 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	28.1	38.8
Performing Financing Receivable | 90 Days or More Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	6.3	16.4
Performing Financing Receivable | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Current	14,097.1	15,087.6
Total Loans and Leases	14,122.5	15,161.1
Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Current	8,815.8	8,678.2
Total Loans and Leases	8,825.1	8,721.3
Performing Financing Receivable | Commercial | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current	3,230.4	3,191.5
Total Loans and Leases	3,244.9	3,221.9
Performing Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,490.5	2,701.2
Total Loans and Leases	1,492.1	2,701.2
Performing Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Current	88.5	90.7
Total Loans and Leases	88.5	90.7
Performing Financing Receivable | Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current	471.9	426.0
Total Loans and Leases	471.9	426.0
Performing Financing Receivable | Commercial | 30-59 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	12.6	45.8
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	6.6	37.4
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	4.4	8.4
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	1.6	0.0
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Performing Financing Receivable | Commercial | 60-89 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	8.0	20.1
Performing Financing Receivable | Commercial | 60-89 Days Past Due | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	2.7	4.5
Performing Financing Receivable | Commercial | 60-89 Days Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	5.3	15.6
Performing Financing Receivable | Commercial | 60-89 Days Past Due | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Performing Financing Receivable | Commercial | 60-89 Days Past Due | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Performing Financing Receivable | Commercial | 60-89 Days Past Due | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Performing Financing Receivable | Commercial | 90 Days or More Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	4.8	7.6
Performing Financing Receivable | Commercial | 90 Days or More Past Due | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	1.2
Performing Financing Receivable | Commercial | 90 Days or More Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	4.8	6.4
Performing Financing Receivable | Commercial | 90 Days or More Past Due | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Performing Financing Receivable | Commercial | 90 Days or More Past Due | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Performing Financing Receivable | Commercial | 90 Days or More Past Due | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Performing Financing Receivable | Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Current	16,634.2	17,125.4
Total Loans and Leases	16,744.7	17,219.6
Performing Financing Receivable | Personal | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current	6,026.8	6,376.8
Total Loans and Leases	6,032.5	6,419.0
Performing Financing Receivable | Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Current	10,532.7	10,681.1
Total Loans and Leases	10,637.5	10,733.1
Performing Financing Receivable | Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current	74.7	67.5
Total Loans and Leases	74.7	67.5
Performing Financing Receivable | Personal | 30-59 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	88.9	66.7
Performing Financing Receivable | Personal | 30-59 Days Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.7	27.2
Performing Financing Receivable | Personal | 30-59 Days Past Due | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	88.2	39.5
Performing Financing Receivable | Personal | 30-59 Days Past Due | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Performing Financing Receivable | Personal | 60-89 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	20.1	18.7
Performing Financing Receivable | Personal | 60-89 Days Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	4.7	6.2
Performing Financing Receivable | Personal | 60-89 Days Past Due | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	15.4	12.5
Performing Financing Receivable | Personal | 60-89 Days Past Due | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Performing Financing Receivable | Personal | 90 Days or More Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	1.5	8.8
Performing Financing Receivable | Personal | 90 Days or More Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.3	8.8
Performing Financing Receivable | Personal | 90 Days or More Past Due | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	1.2	0.0
Performing Financing Receivable | Personal | 90 Days or More Past Due | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	0.0
Nonperforming Financing Receivable
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	115.1	109.3
Other Real Estate Owned	3.8	8.4
Total Nonperforming Assets	118.9	117.7
Nonperforming Financing Receivable | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	14.4	14.1
Nonperforming Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	9.8	6.8
Nonperforming Financing Receivable | Commercial | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	4.0	6.9
Nonperforming Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	0.6	0.4
Nonperforming Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	0.0	0.0
Nonperforming Financing Receivable | Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	0.0	0.0
Nonperforming Financing Receivable | Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	100.7	95.2
Nonperforming Financing Receivable | Personal | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	100.5	95.0
Nonperforming Financing Receivable | Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	0.2	0.2
Nonperforming Financing Receivable | Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	$ 0.0	$ 0.0