Loans - Summary of Nonaccrual Loans and Accruing Receivables 90 Days or More Delinquent (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	$ 1,403		$ 1,629
Total accruing loans contractually past due 90 days or more	40		80
Total nonperforming loans	1,443		1,709
Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	246		463
Total accruing loans contractually past due 90 days or more	8		37
Commercial Loan [Member] | Construction and land loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	47		104
Total accruing loans contractually past due 90 days or more	0		0
Commercial Loan [Member] | Other real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	132		281
Total accruing loans contractually past due 90 days or more	1		8
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	44		47
Total accruing loans contractually past due 90 days or more	6		28
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	18		18
Total accruing loans contractually past due 90 days or more	0		0
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	5		13
Total accruing loans contractually past due 90 days or more	1		1
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	1,107		1,129
Total accruing loans contractually past due 90 days or more	32		43
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	1,013		1,038
Total accruing loans contractually past due 90 days or more	0		0
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	89		86
Total accruing loans contractually past due 90 days or more	0		0
Consumer Loans [Member] | Total residential mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	1,102	[1]	1,124	[1]
Total accruing loans contractually past due 90 days or more	0		0
Consumer Loans [Member] | Credit Card Receivable [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total accruing loans contractually past due 90 days or more	11		15
Consumer Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	5		5
Total accruing loans contractually past due 90 days or more	21		28
Nonaccrual Loans Held For Sale [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	$ 50		$ 37

[1] Nonaccrual residential mortgages includes all receivables which are 90 or more days contractually delinquent as well as loans discharged under Chapter 7 bankruptcy and not re-affirmed and second lien loans where the first lien loan that we own or service is 90 or more days contractually delinquent.