Loans and Leases - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other U.S. loans and non-U.S. loans, short duration advances	$ 1,900,000,000		$ 1,900,000,000		$ 1,600,000,000
Demand deposits	88,000,000		88,000,000		191,600,000
Loans held for sale	100,000		100,000		9,300,000
Maximum limit of individual homogeneous loans collective evaluation for impairment and excluded from impaired loan disclosures	250,000		250,000
Unfunded loan commitments and standby letters of credit	5,200,000		5,200,000		9,700,000
Total Loans and Leases	29,602,100,000		29,602,100,000		29,063,900,000
Nonperforming Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income recorded for nonperforming loans	2,700,000	3,900,000	5,800,000	8,100,000
Total Loans and Leases	44,200,000		44,200,000		72,200,000
Nonperforming Financing Receivable | Residential Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans modified as TDRs in the previous 12 months which became nonperforming	2		2
Recorded Investment	100,000		100,000
Unpaid Principal Balance	100,000		100,000
Performing Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Loans and Leases	$ 63,000,000		$ 63,000,000		$ 41,100,000