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	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Total Other Real Estate Owned	$ 20.6	$ 21.2
Total Nonperforming Assets	289.6	314.9
Nonperforming	29,542.7	29,063.9
Commercial
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	12,999.6	12,354.3
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	7,316.5	6,918.7
Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	3,002.4	2,981.7
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	1,011.6	978.8
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	1,038.1	1,057.5
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	631.0	417.6
Personal
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	16,543.1	16,709.6
Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	10,435.3	10,708.9
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	5,751.4	5,651.4
Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	356.4	349.3
Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Current	29,115.2	28,601.6
30-59 Days Past Due	75.1	109.2
60-89 Days Past Due	51.3	46.3
90 Days or More Past Due	32.1	13.1
Nonperforming	29,273.7	28,770.2
Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Current	12,856.9	12,201.3
30-59 Days Past Due	26.0	25.8
60-89 Days Past Due	17.4	13.0
90 Days or More Past Due	9.7	3.4
Nonperforming	12,910.0	12,243.5
Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Current	7,268.1	6,869.2
30-59 Days Past Due	9.9	15.0
60-89 Days Past Due	6.5	2.7
90 Days or More Past Due	2.1	0.5
Nonperforming	7,286.6	6,887.4
Performing Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	2,908.1	2,878.2
30-59 Days Past Due	16.1	10.8
60-89 Days Past Due	10.9	10.3
90 Days or More Past Due	7.6	2.9
Nonperforming	2,942.7	2,902.2
Performing Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Current	1,011.6	978.8
Nonperforming	1,011.6	978.8
Performing Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Current	1,038.1	1,057.5
Nonperforming	1,038.1	1,057.5
Performing Financing Receivable | Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Current	631.0	417.6
Nonperforming	631.0	417.6
Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Current	16,258.3	16,400.3
30-59 Days Past Due	49.1	83.4
60-89 Days Past Due	33.9	33.3
90 Days or More Past Due	22.4	9.7
Nonperforming	16,363.7	16,526.7
Performing Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	10,198.9	10,428.0
30-59 Days Past Due	17.3	67.7
60-89 Days Past Due	29.8	27.6
90 Days or More Past Due	12.7	8.0
Nonperforming	10,258.7	10,531.3
Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Current	5,703.0	5,623.0
30-59 Days Past Due	31.8	15.7
60-89 Days Past Due	4.1	5.7
90 Days or More Past Due	9.7	1.7
Nonperforming	5,748.6	5,646.1
Performing Financing Receivable | Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Current	356.4	349.3
Nonperforming	356.4	349.3
Nonperforming Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	269.0	293.7
Nonperforming Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	89.6	110.8
Nonperforming Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	29.9	31.3
Nonperforming Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	59.7	79.5
Nonperforming Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	179.4	182.9
Nonperforming Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	176.6	177.6
Nonperforming Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Nonperforming	$ 2.8	$ 5.3