Loans - Summary of Receivables which were Modified and as Result Became Classified as TDR Loans (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Financing Receivable, Impaired [Line Items]
Total	$ 87	$ 52	$ 134	$ 200
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Total	37	0	41	92
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Total	32	0	32	70
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Impaired [Line Items]
Total	5	0	9	22
Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
Total	50	52	93	108
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Total	49	52	92	108
Consumer Loans [Member] | Credit Card Receivables [Member]
Financing Receivable, Impaired [Line Items]
Total	$ 1	$ 0	$ 1	$ 0