Loan and Lease Segment and Class Balances Segregated by Borrower Ratings into "One to Three", "Four to Five" and "Six to Nine" (Watch List) Categories (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 30,719.9	$ 29,385.5
1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	15,208.4	13,955.8
4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	14,818.9	14,620.2
6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	692.6	809.5
Commercial
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	8,212.1	7,375.8
Commercial Real Estate	3,107.7	2,955.8
Lease Financing, net	952.5	975.1
Non-U.S.	1,408.4	954.7
Other	187.9	358.6
Total Loans and Leases	13,868.6	12,620.0
Commercial | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	5,115.4	4,432.5
Commercial Real Estate	1,263.6	1,053.7
Lease Financing, net	572.2	685.7
Non-U.S.	643.7	442.8
Other	137.4	157.7
Total Loans and Leases	7,732.3	6,772.4
Commercial | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	2,983.6	2,801.5
Commercial Real Estate	1,718.2	1,748.7
Lease Financing, net	376.1	285.0
Non-U.S.	763.8	511.9
Other	50.5	200.9
Total Loans and Leases	5,892.2	5,548.0
Commercial | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	113.1	141.8
Commercial Real Estate	125.9	153.4
Lease Financing, net	4.2	4.4
Non-U.S.	0.9
Total Loans and Leases	244.1	299.6
Personal
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	9,872.7	10,271.3
Private Client	6,953.1	6,445.6
Other	25.5	48.6
Total Loans and Leases	16,851.3	16,765.5
Personal | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	2,995.7	3,204.6
Private Client	4,461.8	3,957.6
Other	18.6	21.2
Total Loans and Leases	7,476.1	7,183.4
Personal | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	6,439.9	6,563.6
Private Client	2,479.9	2,481.2
Other	6.9	27.4
Total Loans and Leases	8,926.7	9,072.2
Personal | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	437.1	503.1
Private Client	11.4	6.8
Total Loans and Leases	$ 448.5	$ 509.9