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		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Financing Receivable, Impaired [Line Items]
Total	$ 144	$ 260	$ 256	$ 458
Commercial Loan [Member]
Financing Receivable, Impaired [Line Items]
Total	80	39	100	127
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Total	0	38	15	105
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Impaired [Line Items]
Total	29	1	34	22
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Impaired [Line Items]
Total	51	0	51	0
Consumer Loans [Member]
Financing Receivable, Impaired [Line Items]
Total	64	221	156	331
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Impaired [Line Items]
Total	64	220	155	328
Consumer Loans [Member] | Credit Card Receivables [Member]
Financing Receivable, Impaired [Line Items]
Total	$ 0	$ 1	$ 1	$ 3