Loans and Leases (Delinquency Status) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 33,378.4	$ 31,640.2
Other Real Estate Owned	8.9	16.6
Total Nonperforming Assets	207.5	232.3
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	15,517.4	14,353.6
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9,478.6	8,381.9
Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,814.6	3,333.3
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	807.2	916.3
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,250.2	1,530.6
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	166.8	191.5
Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	17,861.0	17,286.6
Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9,077.5	9,782.6
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	8,751.3	7,466.9
Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	32.2	37.1
Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Current	33,120.9	31,242.6
Total Loans and Leases	33,179.8	31,424.5
Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Current	15,453.1	14,253.2
Total Loans and Leases	15,471.9	14,301.5
Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Current	9,445.4	8,340.5
Total Loans and Leases	9,458.3	8,366.9
Performing Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	3,783.5	3,274.3
Total Loans and Leases	3,789.4	3,296.2
Performing Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Current	807.2	916.3
Past Due	0.0	0.0
Total Loans and Leases	807.2	916.3
Performing Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Current	1,250.2	1,530.6
Past Due	0.0	0.0
Total Loans and Leases	1,250.2	1,530.6
Performing Financing Receivable | Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Current	166.8	191.5
Past Due	0.0	0.0
Total Loans and Leases	166.8	191.5
Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Current	17,667.8	16,989.4
Total Loans and Leases	17,707.9	17,123.0
Performing Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	8,911.3	9,556.3
Total Loans and Leases	8,924.9	9,620.2
Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Current	8,724.3	7,396.0
Total Loans and Leases	8,750.8	7,465.7
Performing Financing Receivable | Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Current	32.2	37.1
Past Due	0.0	0.0
Total Loans and Leases	32.2	37.1
Nonperforming Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	198.6	215.7
Nonperforming Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	45.5	52.1
Nonperforming Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	20.3	15.0
Nonperforming Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	25.2	37.1
Nonperforming Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	153.1	163.6
Nonperforming Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	152.6	162.4
Nonperforming Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	0.5	1.2
30-59 Days Past Due | Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Past Due	38.3	129.6
30-59 Days Past Due | Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Past Due	15.4	24.1
30-59 Days Past Due | Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Past Due	11.7	14.5
30-59 Days Past Due | Performing Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	3.7	9.6
30-59 Days Past Due | Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Past Due	22.9	105.5
30-59 Days Past Due | Performing Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	2.9	49.5
30-59 Days Past Due | Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Past Due	20.0	56.0
60-89 Days Past Due | Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Past Due	18.3	29.6
60-89 Days Past Due | Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Past Due	3.0	13.8
60-89 Days Past Due | Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Past Due	0.8	4.0
60-89 Days Past Due | Performing Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	2.2	9.8
60-89 Days Past Due | Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Past Due	15.3	15.8
60-89 Days Past Due | Performing Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	9.6	9.9
60-89 Days Past Due | Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Past Due	5.7	5.9
90 Days or More Past Due | Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Past Due	2.3	22.7
90 Days or More Past Due | Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Past Due	0.4	10.4
90 Days or More Past Due | Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Past Due	0.4	7.9
90 Days or More Past Due | Performing Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	0.0	2.5
90 Days or More Past Due | Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Past Due	1.9	12.3
90 Days or More Past Due | Performing Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Past Due	1.1	4.5
90 Days or More Past Due | Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Past Due	$ 0.8	$ 7.8