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 (Detail) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	$ 28,691.4	$ 28,132.0
Total Other Real Estate Owned	30.4	45.5
Total Nonperforming Assets	337.9	378.5
Commercial | Performing Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	14.3	40.5
60 - 89 Days Past Due	25.8	23.9
90 Days or More Past Due	6.9	10.2
Current	12,052.8	11,364.4
Total Loans and Leases	12,099.8	11,439.0
Commercial | Performing Financing Receivable | Commercial and Institutional
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	8.0	16.3
60 - 89 Days Past Due	18.4	8.2
90 Days or More Past Due	1.6	0.8
Current	6,394.5	5,831.2
Total Loans and Leases	6,422.5	5,856.5
Commercial | Performing Financing Receivable | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	6.3	24.2
60 - 89 Days Past Due	7.4	15.7
90 Days or More Past Due	5.3	9.4
Current	2,855.2	3,076.7
Total Loans and Leases	2,874.2	3,126.0
Commercial | Performing Financing Receivable | Lease Financing, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,014.1	1,063.7
Total Loans and Leases	1,014.1	1,063.7
Commercial | Performing Financing Receivable | Non-U.S.
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	1,315.2	1,046.2
Total Loans and Leases	1,315.2	1,046.2
Commercial | Performing Financing Receivable | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	473.8	346.6
Total Loans and Leases	473.8	346.6
Personal | Performing Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	32.7	111.8
60 - 89 Days Past Due	42.7	30.2
90 Days or More Past Due	5.5	2.8
Current	16,203.2	16,215.2
Total Loans and Leases	16,284.1	16,360.0
Personal | Performing Financing Receivable | Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	16.2	76.1
60 - 89 Days Past Due	31.8	17.2
90 Days or More Past Due	4.7	0.9
Current	10,537.8	10,607.4
Total Loans and Leases	10,590.5	10,701.6
Personal | Performing Financing Receivable | Private Client
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	16.5	35.7
60 - 89 Days Past Due	10.9	13.0
90 Days or More Past Due	0.8	1.9
Current	5,393.4	5,367.8
Total Loans and Leases	5,421.6	5,418.4
Personal | Performing Financing Receivable | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	272.0	240.0
Total Loans and Leases	272.0	240.0
Performing Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
30 - 59 Days Past Due	47.0	152.3
60 - 89 Days Past Due	68.5	54.1
90 Days or More Past Due	12.4	13.0
Current	28,256.0	27,579.6
Total Loans and Leases	28,383.9	27,799.0
Commercial | Nonperforming Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	119.5	174.4
Commercial | Nonperforming Financing Receivable | Commercial and Institutional
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	35.5	58.0
Commercial | Nonperforming Financing Receivable | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	84.0	116.4
Personal | Nonperforming Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	188.0	158.6
Personal | Nonperforming Financing Receivable | Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	181.9	153.3
Personal | Nonperforming Financing Receivable | Private Client
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	6.1	5.3
Nonperforming Financing Receivable
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	307.5	333.0
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	12,219.3	11,613.4
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	6,458.0	5,914.5
Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	2,958.2	3,242.4
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	1,014.1	1,063.7
Commercial | Non-U.S.
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	1,315.2	1,046.2
Commercial | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	473.8	346.6
Personal
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	16,472.1	16,518.6
Personal | Residential Real Estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	10,772.4	10,854.9
Personal | Private Client
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	5,427.7	5,423.7
Personal | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans and Leases	$ 272.0	$ 240.0