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	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Other Real Estate Owned	$ 10.5	$ 20.3
Total Nonperforming Assets	262.2	275.1
Total Loans and Leases	28,862.9	29,504.5
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	12,682.0	12,897.2
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	7,255.6	7,468.5
Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	2,822.9	2,859.8
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,005.6	1,035.0
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,152.7	1,192.3
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	445.2	341.6
Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	16,180.9	16,607.3
Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	10,147.9	10,375.2
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	5,900.0	6,130.1
Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	133.0	102.0
Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Current	28,419.0	29,073.9
30-59 Days Past Due	151.4	96.2
60-89 Days Past Due	29.7	60.6
90 Days or More Past Due	11.1	19.0
Total Loans and Leases	28,611.2	29,249.7
Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Current	12,562.7	12,784.3
30-59 Days Past Due	28.6	13.3
60-89 Days Past Due	10.9	18.6
90 Days or More Past Due	5.0	3.0
Total Loans and Leases	12,607.2	12,819.2
Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Current	7,219.3	7,433.4
30-59 Days Past Due	9.2	6.4
60-89 Days Past Due	3.0	5.5
90 Days or More Past Due	3.0	1.6
Total Loans and Leases	7,234.5	7,446.9
Performing Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	2,739.9	2,782.0
30-59 Days Past Due	19.4	6.9
60-89 Days Past Due	7.9	13.1
90 Days or More Past Due	2.0	1.4
Total Loans and Leases	2,769.2	2,803.4
Performing Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Current	1,005.6	1,035.0
Total Loans and Leases	1,005.6	1,035.0
Performing Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Current	1,152.7	1,192.3
Total Loans and Leases	1,152.7	1,192.3
Performing Financing Receivable | Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Current	445.2	341.6
Total Loans and Leases	445.2	341.6
Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Current	15,856.3	16,289.6
30-59 Days Past Due	122.8	82.9
60-89 Days Past Due	18.8	42.0
90 Days or More Past Due	6.1	16.0
Total Loans and Leases	16,004.0	16,430.5
Performing Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	9,873.4	10,096.3
30-59 Days Past Due	84.8	68.1
60-89 Days Past Due	11.8	25.7
90 Days or More Past Due	4.3	10.5
Total Loans and Leases	9,974.3	10,200.6
Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Current	5,849.9	6,091.3
30-59 Days Past Due	38.0	14.8
60-89 Days Past Due	7.0	16.3
90 Days or More Past Due	1.8	5.5
Total Loans and Leases	5,896.7	6,127.9
Performing Financing Receivable | Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Current	133.0	102.0
Total Loans and Leases	133.0	102.0
Nonperforming Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	251.7	254.8
Nonperforming Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	74.8	78.0
Nonperforming Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	21.1	21.6
Nonperforming Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	53.7	56.4
Nonperforming Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	176.9	176.8
Nonperforming Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	173.6	174.6
Nonperforming Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 3.3	$ 2.2