Loans - Trouble Debt Restructuring Additional Information (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]
Trouble debt restructuring average recorded investment	$ 1,412		$ 1,245		$ 1,375		$ 1,179
Trouble debt restructuring interest income recognized	13		13		37		34
Commercial Loan [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	497		483		453		487
Trouble debt restructuring interest income recognized	5		5		12		12
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	405		364		362		361
Trouble debt restructuring interest income recognized	4		2		9		6
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	39		85		49		92
Trouble debt restructuring interest income recognized	0		0		0		0
Commercial Loan [Member] | Global Banking [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	25		0		13		0
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	28		34		29		34
Trouble debt restructuring interest income recognized	1		3		3		6
Consumer Loans [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	915		762		922		692
Trouble debt restructuring interest income recognized	8		8		25		22
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	904	[1]	745	[1]	910	[1]	676	[1]
Trouble debt restructuring interest income recognized	8		8		24		22
Consumer Loans [Member] | Credit Card Receivables [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	11		17		12		16
Trouble debt restructuring interest income recognized	$ 0		$ 0		$ 1		$ 0

[1] Beginning in the third quarter of 2012, average balances for residential mortgages include loans discharged under Chapter 7 bankruptcy and not re-affirmed.