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	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	$ 28,810.4	$ 29,504.5
1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	13,181.5	13,332.0
4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	14,629.9	15,240.4
6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Total Loans and Leases	999.0	932.1
Commercial
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	7,209.6	7,468.5
Commercial Real Estate	2,845.0	2,859.8
Lease Financing, net	988.7	1,035.0
Non-U.S.	1,394.2	1,192.3
Other	182.1	341.6
Total Loans and Leases	12,619.6	12,897.2
Commercial | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	4,111.3	4,291.8
Commercial Real Estate	957.8	888.6
Lease Financing, net	615.4	647.1
Non-U.S.	465.7	542.7
Other	95.0	167.2
Total Loans and Leases	6,245.2	6,537.4
Commercial | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	2,899.2	3,040.6
Commercial Real Estate	1,669.9	1,710.9
Lease Financing, net	368.7	382.3
Non-U.S.	927.8	646.6
Other	87.1	174.4
Total Loans and Leases	5,952.7	5,954.8
Commercial | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Commercial and Institutional	199.1	136.1
Commercial Real Estate	217.3	260.3
Lease Financing, net	4.6	5.6
Non-U.S.	0.7	3.0
Total Loans and Leases	421.7	405.0
Personal
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	10,293.9	10,375.2
Private Client	5,842.6	6,130.1
Other	54.3	102.0
Total Loans and Leases	16,190.8	16,607.3
Personal | 1 to 3 Category
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	3,264.6	3,003.3
Private Client	3,643.3	3,741.3
Other	28.4	50.0
Total Loans and Leases	6,936.3	6,794.6
Personal | 4 to 5 Category
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	6,475.6	6,868.2
Private Client	2,175.7	2,365.4
Other	25.9	52.0
Total Loans and Leases	8,677.2	9,285.6
Personal | 6 to 9 Category (Watch List)
Financing Receivable, Recorded Investment [Line Items]
Residential Real Estate	553.7	503.7
Private Client	23.6	23.4
Total Loans and Leases	$ 577.3	$ 527.1