Loans - Loans 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, Modifications [Line Items]
TDR loans during previous months which became contractually delinquent	$ 40	$ 57	$ 65	$ 159
Commercial Loan [Member]
Financing Receivable, Modifications [Line Items]
TDR loans during previous months which became contractually delinquent	30	0	30	0
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Modifications [Line Items]
TDR loans during previous months which became contractually delinquent	28	0	28	0
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Modifications [Line Items]
TDR loans during previous months which became contractually delinquent	2	0	2	0
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Modifications [Line Items]
TDR loans during previous months which became contractually delinquent	0	0	0	0
Consumer Loans [Member]
Financing Receivable, Modifications [Line Items]
TDR loans during previous months which became contractually delinquent	10	57	35	159
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
TDR loans during previous months which became contractually delinquent	10	57	35	159
Consumer Loans [Member] | Credit Card Receivables [Member]
Financing Receivable, Modifications [Line Items]
TDR loans during previous months which became contractually delinquent	$ 0	$ 0	$ 0	$ 0