Loans - Summary of Nonaccrual Loans and Accruing Receivables 90 Days or More Delinquent (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	$ 1,629		$ 1,828
Total accruing loans contractually past due 90 days or more	80		61
Total nonperforming loans	1,709		1,889
Nonaccrual loans held for sale [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	37		91
Commercial Loan [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	463		825
Total accruing loans contractually past due 90 days or more	37		14
Commercial Loan [Member] | Construction and land loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	104		103
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	281		512
Total accruing loans contractually past due 90 days or more	8		1
Commercial Loan [Member] | Business Banking and Middle Markets Enterprises [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	47		58
Total accruing loans contractually past due 90 days or more	28		11
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	18		137
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	13		15
Total accruing loans contractually past due 90 days or more	1		2
Consumer Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	1,129		912
Total accruing loans contractually past due 90 days or more	43		47
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	1,038		815	[1]
Total accruing loans contractually past due 90 days or more	0		0	[1]
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	86		89
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	1,124	[2],[3]	904	[2],[3]
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	15		20
Consumer Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	5		8
Total accruing loans contractually past due 90 days or more	$ 28		$ 27

[1] In 2012, we reclassified $66 million of residential mortgage loans discharged under Chapter 7 bankruptcy and not re-affirmed to nonaccrual, consistent with recently issued regulatory guidance. Interest income reversed on these loans was not material.

[2] Nonaccrual residential mortgages includes all receivables which are 90 or more days contractually delinquent as well as second lien loans where the first lien loan that we own or service is 90 or more days contractually delinquent.

[3] In 2012 we reclassified $66 million of residential mortgage loans discharged under Chapter 7 bankruptcy and not re-affirmed to nonaccrual, consistent with recently issued regulatory guidance. Interest income reversed on these loans was not material.