Loans - Delinquency Ratio for Consumer Loan (Detail) (Consumer Loans [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	$ 1,285		$ 1,359
Delinquency Ratio	6.54%		6.92%
Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	1,158	[1]	1,233	[1]
Delinquency Ratio	7.23%	[1]	7.78%	[1]
Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	85		75
Delinquency Ratio	3.80%		3.23%
Total residential mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	1,243		1,308
Delinquency Ratio	6.81%		7.20%
Credit Card Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	18		21
Delinquency Ratio	2.40%		2.58%
Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Dollars of Delinquency	$ 24		$ 30
Delinquency Ratio	3.74%		4.52%

[1] At March 31, 2013 and December 31, 2012, residential mortgage loan delinquency includes $1.1 billion and $1.0 billion, respectively, of loans that are carried at the lower of amortized cost or fair value less cost to sell.