Loans and Leases (Delinquency Status) (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	$ 30,844.2	$ 32,490.0
Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	13,981.9	15,175.2
Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	8,623.8	8,728.1
Commercial | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	3,227.6	3,228.8
Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	1,478.3	2,701.6
Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	87.6	90.7
Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	564.6	426.0
Personal
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	16,862.3	17,314.8
Personal | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	6,066.3	6,514.0
Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	10,706.6	10,733.3
Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	89.4	67.5
Performing Financing Receivable
Financing Receivable, Credit Quality Indicator [Line Items]
Current	30,660.0	32,213.0
Total Loans and Leases	30,731.1	32,380.7
Performing Financing Receivable | 30-59 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	43.5	112.5
Performing Financing Receivable | 60-89 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	15.6	38.8
Performing Financing Receivable | 90 Days or More Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	12.0	16.4
Performing Financing Receivable | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Current	13,947.9	15,087.6
Total Loans and Leases	13,966.9	15,161.1
Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Current	8,601.3	8,678.2
Total Loans and Leases	8,613.2	8,721.3
Performing Financing Receivable | Commercial | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current	3,216.7	3,191.5
Total Loans and Leases	3,223.8	3,221.9
Performing Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Current	1,477.7	2,701.2
Total Loans and Leases	1,477.7	2,701.2
Performing Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Credit Quality Indicator [Line Items]
Current	87.6	90.7
Total Loans and Leases	87.6	90.7
Performing Financing Receivable | Commercial | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current	564.6	426.0
Total Loans and Leases	564.6	426.0
Performing Financing Receivable | Commercial | 30-59 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	10.5	45.8
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	8.9	37.4
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	1.6	8.4
Performing Financing Receivable | Commercial | 30-59 Days Past Due | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.0	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	3.3	20.1
Performing Financing Receivable | Commercial | 60-89 Days Past Due | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	3.0	4.5
Performing Financing Receivable | Commercial | 60-89 Days Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	0.3	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	5.2	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	5.2	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	16,712.1	17,125.4
Total Loans and Leases	16,764.2	17,219.6
Performing Financing Receivable | Personal | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Current	5,952.4	6,376.8
Total Loans and Leases	5,968.5	6,419.0
Performing Financing Receivable | Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Current	10,670.3	10,681.1
Total Loans and Leases	10,706.3	10,733.1
Performing Financing Receivable | Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Current	89.4	67.5
Total Loans and Leases	89.4	67.5
Performing Financing Receivable | Personal | 30-59 Days Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	33.0	66.7
Performing Financing Receivable | Personal | 30-59 Days Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	5.6	27.2
Performing Financing Receivable | Personal | 30-59 Days Past Due | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	27.4	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	12.3	18.7
Performing Financing Receivable | Personal | 60-89 Days Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	5.8	6.2
Performing Financing Receivable | Personal | 60-89 Days Past Due | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	6.5	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	6.8	8.8
Performing Financing Receivable | Personal | 90 Days or More Past Due | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	4.7	8.8
Performing Financing Receivable | Personal | 90 Days or More Past Due | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Past Due	2.1	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	113.1	109.3
Other Real Estate Owned	3.2	8.4
Total Nonperforming Assets	116.3	117.7
Nonperforming Financing Receivable | Commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	15.0	14.1
Nonperforming Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	10.6	6.8
Nonperforming Financing Receivable | Commercial | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	3.8	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	98.1	95.2
Nonperforming Financing Receivable | Personal | Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	97.8	95.0
Nonperforming Financing Receivable | Personal | Private Client
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	0.3	0.2
Nonperforming Financing Receivable | Personal | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total Loans and Leases	$ 0.0	$ 0.0