Amounts Outstanding for Loans and Leases by Segment and Class (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	$ 32,630.2	$ 31,640.2
Allowance for Credit Losses Assigned to Loans and Leases	(259.0)	(267.0)
Net Loans and Leases	32,371.2	31,373.2
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial and Institutional	9,030.2	8,381.9
Commercial Real Estate	3,500.9	3,333.3
Lease Financing, net	870.6	916.3
Non-U.S.	1,661.6	1,530.6
Other	428.0	191.5
Total Loans and Leases	15,491.3	14,353.6
Allowance for Credit Losses Assigned to Loans and Leases	(139.5)	(143.8)
Personal
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential Real Estate	9,440.2	9,782.6
Private Client	7,615.8	7,466.9
Other	82.9	37.1
Total Loans and Leases	17,138.9	17,286.6
Allowance for Credit Losses Assigned to Loans and Leases	$ (119.5)	$ (123.2)