Loans - Delinquency Ratio for Consumer Loan (Detail) (Consumer Loans [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	$ 1,218	$ 1,258
Delinquency Ratio	6.25%	6.01%
Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	1,100	1,101
Delinquency Ratio	7.04%	7.19%
Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	67	99
Delinquency Ratio	2.81%	2.89%
Total residential mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	1,167	1,200
Delinquency Ratio	6.48%	6.41%
Credit Card Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	22	28
Delinquency Ratio	2.76%	2.25%
Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	$ 29	$ 30
Delinquency Ratio	4.26%	3.17%