Loans - Trouble Debt Restructuring Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	$ 1,251		$ 1,178		$ 1,305		$ 1,153
Trouble debt restructuring interest income recognized	12		11		24		20
Commercial Loan [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	349		491		386		486
Trouble debt restructuring interest income recognized	4		4		7		7
Commercial Loan [Member] | Construction and Other Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	290		360		307		354
Trouble debt restructuring interest income recognized	3		2		5		4
Commercial Loan [Member] | Business and Corporate Banking [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	30		96		49		96
Trouble debt restructuring interest income recognized	0		0		0		0
Commercial Loan [Member] | Other Commercial [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	29		35		30		36
Trouble debt restructuring interest income recognized	1		2		2		3
Consumer Loans [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	902		687		919		667
Trouble debt restructuring interest income recognized	8		7		17		13
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	890	[1]	669	[1]	906	[1]	648	[1]
Trouble debt restructuring interest income recognized	8		7		17		13
Consumer Loans [Member] | Credit Card Receivables [Member]
Financing Receivable, Modifications [Line Items]
Trouble debt restructuring average recorded investment	12		18		13		19
Trouble debt restructuring interest income recognized	$ 0		$ 0		$ 0		$ 0

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