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, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Other Real Estate Owned	$ 14.5	$ 20.3
Total Nonperforming Assets	281.2	275.1
Total Loans and Leases	28,810.4	29,504.5
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	12,619.6	12,897.2
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	7,209.6	7,468.5
Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	2,845.0	2,859.8
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	988.7	1,035.0
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,394.2	1,192.3
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	182.1	341.6
Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	16,190.8	16,607.3
Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	10,293.9	10,375.2
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	5,842.6	6,130.1
Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	54.3	102.0
Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Current	28,400.3	29,073.9
30-59 Days Past Due	82.5	96.2
60-89 Days Past Due	42.4	60.6
90 Days or More Past Due	18.5	19.0
Total Loans and Leases	28,543.7	29,249.7
Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Current	12,480.0	12,784.3
30-59 Days Past Due	34.9	13.3
60-89 Days Past Due	15.7	18.6
90 Days or More Past Due	2.5	3.0
Total Loans and Leases	12,533.1	12,819.2
Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Current	7,163.4	7,433.4
30-59 Days Past Due	13.0	6.4
60-89 Days Past Due	6.5	5.5
90 Days or More Past Due	1.7	1.6
Total Loans and Leases	7,184.6	7,446.9
Performing Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	2,751.6	2,782.0
30-59 Days Past Due	21.9	6.9
60-89 Days Past Due	9.2	13.1
90 Days or More Past Due	0.8	1.4
Total Loans and Leases	2,783.5	2,803.4
Performing Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Current	988.7	1,035.0
Total Loans and Leases	988.7	1,035.0
Performing Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Current	1,394.2	1,192.3
Total Loans and Leases	1,394.2	1,192.3
Performing Financing Receivable | Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Current	182.1	341.6
Total Loans and Leases	182.1	341.6
Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Current	15,920.3	16,289.6
30-59 Days Past Due	47.6	82.9
60-89 Days Past Due	26.7	42.0
90 Days or More Past Due	16.0	16.0
Total Loans and Leases	16,010.6	16,430.5
Performing Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	10,075.2	10,096.3
30-59 Days Past Due	12.1	68.1
60-89 Days Past Due	16.4	25.7
90 Days or More Past Due	13.0	10.5
Total Loans and Leases	10,116.7	10,200.6
Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Current	5,790.8	6,091.3
30-59 Days Past Due	35.5	14.8
60-89 Days Past Due	10.3	16.3
90 Days or More Past Due	3.0	5.5
Total Loans and Leases	5,839.6	6,127.9
Performing Financing Receivable | Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Current	54.3	102.0
Total Loans and Leases	54.3	102.0
Nonperforming Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	266.7	254.8
Nonperforming Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	86.5	78.0
Nonperforming Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	25.0	21.6
Nonperforming Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	61.5	56.4
Nonperforming Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	180.2	176.8
Nonperforming Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	177.2	174.6
Nonperforming Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 3.0	$ 2.2