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	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	$ 9,800.0	$ 10,300.0
Commercial Real Estate	3,333.3	2,955.8
Lease Financing, net	916.3	975.1
Total Loans and Leases	31,640.2	29,385.5
1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	16,322.9	13,955.8
4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	14,680.4	14,620.2
6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	636.9	809.5
Commercial
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	8,381.9	7,375.8
Commercial Real Estate	3,333.3	2,955.8
Lease Financing, net	916.3	975.1
Non-U.S.	1,530.6	954.7
Other	191.5	358.6
Total Loans and Leases	14,353.6	12,620.0
Commercial | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	5,340.9	4,432.5
Commercial Real Estate	1,371.7	1,053.7
Lease Financing, net	552.5	685.7
Non-U.S.	636.8	442.8
Other	108.1	157.7
Total Loans and Leases	8,010.0	6,772.4
Commercial | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	2,947.3	2,801.5
Commercial Real Estate	1,861.8	1,748.7
Lease Financing, net	360.3	285.0
Non-U.S.	892.9	511.9
Other	83.4	200.9
Total Loans and Leases	6,145.7	5,548.0
Commercial | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	93.7	141.8
Commercial Real Estate	99.8	153.4
Lease Financing, net	3.5	4.4
Non-U.S.	0.9
Total Loans and Leases	197.9	299.6
Personal
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	9,782.6	10,271.3
Private Client	7,466.9	6,445.6
Other	37.1	48.6
Total Loans and Leases	17,286.6	16,765.5
Personal | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	3,148.0	3,204.6
Private Client	5,143.8	3,957.6
Other	21.1	21.2
Total Loans and Leases	8,312.9	7,183.4
Personal | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	6,207.0	6,563.6
Private Client	2,311.7	2,481.2
Other	16.0	27.4
Total Loans and Leases	8,534.7	9,072.2
Personal | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	427.6	503.1
Private Client	11.4	6.8
Total Loans and Leases	$ 439.0	$ 509.9