Balances and Delinquency Status of Performing and Nonperforming Loans and Leases by Segment and Class as well as Total Other Real Estate Owned and Nonperforming Asset Balances (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Other Real Estate Owned	$ 12.6	$ 11.9
Total Nonperforming Assets	241.9	274.7
Total Loans and Leases	30,697.6	29,385.5
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	13,991.4	12,620.0
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	8,042.6	7,375.8
Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,075.5	2,955.8
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	926.4	975.1
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,334.0	954.7
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	612.9	358.6
Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	16,706.2	16,765.5
Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9,992.6	10,271.3
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	6,630.5	6,445.6
Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	83.1	48.6
Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Current	30,313.8	28,889.0
30-59 Days Past Due	96.6	167.5
60-89 Days Past Due	44.8	49.8
90 Days or More Past Due	13.1	16.4
Total Loans and Leases	30,468.3	29,122.7
Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Current	13,864.0	12,501.8
30-59 Days Past Due	39.9	9.1
60-89 Days Past Due	18.1	26.7
90 Days or More Past Due	3.2	10.1
Total Loans and Leases	13,925.2	12,547.7
Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Current	7,977.8	7,332.3
30-59 Days Past Due	30.3	5.0
60-89 Days Past Due	12.4	12.1
90 Days or More Past Due	1.3	3.3
Total Loans and Leases	8,021.8	7,352.7
Performing Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	3,012.9	2,881.1
30-59 Days Past Due	9.6	4.1
60-89 Days Past Due	5.7	14.6
90 Days or More Past Due	1.9	6.8
Total Loans and Leases	3,030.1	2,906.6
Performing Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Current	926.4	975.1
Total Loans and Leases	926.4	975.1
Performing Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Current	1,334.0	954.7
Total Loans and Leases	1,334.0	954.7
Performing Financing Receivable | Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Current	612.9	358.6
Total Loans and Leases	612.9	358.6
Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Current	16,449.8	16,387.2
30-59 Days Past Due	56.7	158.4
60-89 Days Past Due	26.7	23.1
90 Days or More Past Due	9.9	6.3
Total Loans and Leases	16,543.1	16,575.0
Performing Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	9,802.6	9,934.4
30-59 Days Past Due	12.4	129.3
60-89 Days Past Due	11.1	15.6
90 Days or More Past Due	4.8	2.9
Total Loans and Leases	9,830.9	10,082.2
Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Current	6,564.1	6,404.2
30-59 Days Past Due	44.3	29.1
60-89 Days Past Due	15.6	7.5
90 Days or More Past Due	5.1	3.4
Total Loans and Leases	6,629.1	6,444.2
Performing Financing Receivable | Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Current	83.1	48.6
Total Loans and Leases	83.1	48.6
Nonperforming Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	229.3	262.8
Nonperforming Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	66.2	72.3
Nonperforming Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	20.8	23.1
Nonperforming Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	45.4	49.2
Nonperforming Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	163.1	190.5
Nonperforming Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	161.7	189.1
Nonperforming Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 1.4	$ 1.4