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, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Other Real Estate Owned	$ 10.7	$ 11.9
Total Nonperforming Assets	231.2	274.7
Total Loans and Leases	30,719.9	29,385.5
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	13,868.6	12,620.0
Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	8,212.1	7,375.8
Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	3,107.7	2,955.8
Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	952.5	975.1
Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	1,408.4	954.7
Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	187.9	358.6
Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	16,851.3	16,765.5
Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	9,872.7	10,271.3
Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	6,953.1	6,445.6
Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	25.5	48.6
Performing Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Current	30,392.4	28,889.0
30-59 Days Past Due	47.0	167.5
60-89 Days Past Due	34.9	49.8
90 Days or More Past Due	25.1	16.4
Total Loans and Leases	30,499.4	29,122.7
Performing Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Current	13,747.0	12,501.8
30-59 Days Past Due	18.0	9.1
60-89 Days Past Due	18.5	26.7
90 Days or More Past Due	13.5	10.1
Total Loans and Leases	13,797.0	12,547.7
Performing Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Current	8,153.8	7,332.3
30-59 Days Past Due	10.2	5.0
60-89 Days Past Due	13.3	12.1
90 Days or More Past Due	3.1	3.3
Total Loans and Leases	8,180.4	7,352.7
Performing Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	3,044.4	2,881.1
30-59 Days Past Due	7.8	4.1
60-89 Days Past Due	5.2	14.6
90 Days or More Past Due	10.4	6.8
Total Loans and Leases	3,067.8	2,906.6
Performing Financing Receivable | Commercial | Lease Financing, net
Financing Receivable, Recorded Investment [Line Items]
Current	952.5	975.1
Total Loans and Leases	952.5	975.1
Performing Financing Receivable | Commercial | Non-U.S.
Financing Receivable, Recorded Investment [Line Items]
Current	1,408.4	954.7
Total Loans and Leases	1,408.4	954.7
Performing Financing Receivable | Commercial | Other
Financing Receivable, Recorded Investment [Line Items]
Current	187.9	358.6
Total Loans and Leases	187.9	358.6
Performing Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Current	16,645.4	16,387.2
30-59 Days Past Due	29.0	158.4
60-89 Days Past Due	16.4	23.1
90 Days or More Past Due	11.6	6.3
Total Loans and Leases	16,702.4	16,575.0
Performing Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Current	9,702.1	9,934.4
30-59 Days Past Due	7.9	129.3
60-89 Days Past Due	9.0	15.6
90 Days or More Past Due	6.4	2.9
Total Loans and Leases	9,725.4	10,082.2
Performing Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Current	6,917.8	6,404.2
30-59 Days Past Due	21.1	29.1
60-89 Days Past Due	7.4	7.5
90 Days or More Past Due	5.2	3.4
Total Loans and Leases	6,951.5	6,444.2
Performing Financing Receivable | Personal | Other
Financing Receivable, Recorded Investment [Line Items]
Current	25.5	48.6
Total Loans and Leases	25.5	48.6
Nonperforming Financing Receivable
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	220.5	262.8
Nonperforming Financing Receivable | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	71.6	72.3
Nonperforming Financing Receivable | Commercial | Commercial and Institutional
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	31.7	23.1
Nonperforming Financing Receivable | Commercial | Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	39.9	49.2
Nonperforming Financing Receivable | Personal
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	148.9	190.5
Nonperforming Financing Receivable | Personal | Residential Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	147.3	189.1
Nonperforming Financing Receivable | Personal | Private Client
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 1.6	$ 1.4