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, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 29,156.3	$ 29,063.9
Total Other Real Estate	22.4	21.2
Total Nonperforming Assets	284.5	314.9
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	12,685.5	12,354.3
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	7,088.4	6,918.7
Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	2,997.4	2,981.7
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,018.2	978.8
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,110.9	1,057.5
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	470.6	417.6
Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	16,470.8	16,709.6
Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	10,612.7	10,708.9
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	5,409.6	5,651.4
Personal | Other Member
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	448.5	349.3
Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Current	28,686.6	28,601.6
30 - 59 Days Past Due	124.9	109.2
60 - 89 Days Past Due	61.8	46.3
90 Days or More Past Due	20.9	13.1
Total Loans and Leases	28,894.2	28,770.2
Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Current	12,513.5	12,201.3
30 - 59 Days Past Due	39.9	25.8
60 - 89 Days Past Due	21.9	13.0
90 Days or More Past Due	11.8	3.4
Total Loans and Leases	12,587.1	12,243.5
Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Current	7,025.0	6,869.2
30 - 59 Days Past Due	16.6	15.0
60 - 89 Days Past Due	12.4	2.7
90 Days or More Past Due	5.8	0.5
Total Loans and Leases	7,059.8	6,887.4
Performing Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	2,889.8	2,878.2
30 - 59 Days Past Due	22.3	10.8
60 - 89 Days Past Due	9.5	10.3
90 Days or More Past Due	6.0	2.9
Total Loans and Leases	2,927.6	2,902.2
Performing Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Current	1,017.2	978.8
30 - 59 Days Past Due	1.0
Total Loans and Leases	1,018.2	978.8
Performing Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Current	1,110.9	1,057.5
Total Loans and Leases	1,110.9	1,057.5
Performing Financing Receivable | Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Current	470.6	417.6
Total Loans and Leases	470.6	417.6
Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Current	16,173.1	16,400.3
30 - 59 Days Past Due	85.0	83.4
60 - 89 Days Past Due	39.9	33.3
90 Days or More Past Due	9.1	9.7
Total Loans and Leases	16,307.1	16,526.7
Performing Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	10,365.8	10,428.0
30 - 59 Days Past Due	74.8	67.7
60 - 89 Days Past Due	4.2	27.6
90 Days or More Past Due	7.9	8.0
Total Loans and Leases	10,452.7	10,531.3
Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Current	5,358.8	5,623.0
30 - 59 Days Past Due	10.2	15.7
60 - 89 Days Past Due	35.7	5.7
90 Days or More Past Due	1.2	1.7
Total Loans and Leases	5,405.9	5,646.1
Performing Financing Receivable | Personal | Other Member
Financing Receivable, Recorded Investment [Line Items]
Current	448.5	349.3
Total Loans and Leases	448.5	349.3
Nonperforming Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	262.1	293.7
Nonperforming Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	98.4	110.8
Nonperforming Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	28.6	31.3
Nonperforming Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	69.8	79.5
Nonperforming Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	163.7	182.9
Nonperforming Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	160.0	177.6
Nonperforming Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 3.7	$ 5.3