Loans - Summary of Nonaccrual Loans and Accruing Receivables 90 Days or More Delinquent (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	$ 1,072		$ 1,305
Total accruing loans contractually past due 90 days or more	25		34
Total nonperforming loans	1,097		1,339
Commercial Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	92		254
Total accruing loans contractually past due 90 days or more	4		6
Commercial Loans [Member] | Construction and Land Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	11		44
Commercial Loans [Member] | Other real estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	54		122
Commercial Loans [Member] | Business and Corporate Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	25		21
Total accruing loans contractually past due 90 days or more	3		5
Commercial Loans [Member] | Global Banking [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	0		65
Total accruing loans contractually past due 90 days or more	0		0
Commercial Loans [Member] | Other Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	2		2
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	919		1,026
Total accruing loans contractually past due 90 days or more	21		28
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	851		949
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	68		77
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	919	[1],[2],[3]	1,026	[1],[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	10		14
Consumer Loans [Member] | Other consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	0		0
Total accruing loans contractually past due 90 days or more	11		14
Nonaccrual Loans Held For Sale [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total nonaccruing loans	$ 61		$ 25

[1] Residential mortgage nonaccrual loans for all periods does not include guaranteed loans purchased from the Government National Mortgage Association ("GNMA"). Repayment of these loans are predominantly insured by the Federal Housing Administration and as such, these loans have different risk characteristics from the rest of our customer loan portfolio.

[2] 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.

[3] At September 30, 2014 and December 31, 2013, residential mortgage loan nonaccrual balances include $827 million and $841 million, respectively, of loans that are carried at the lower of amortized cost or fair value of the collateral less cost to sell.