Loans - Status of Consumer Loan Portfolio (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual Loans	$ 1,790	$ 1,828
Accruing Loans Contractually Past Due 90 days or More	51	61
Total	61,452	51,867	49,600
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	17,761	17,259
Nonaccrual Loans	1,081	912
Accruing Loans Contractually Past Due 90 days or More	42	47
Total	18,884	18,218
Consumer Loans [Member] | Residential Mortgage [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	14,107	13,298
Nonaccrual Loans	979	815
Total	15,086	14,113	13,842
Consumer Loans [Member] | Home Equity Mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	2,290	2,474
Nonaccrual Loans	97	89
Total	2,387	2,563	2,618
Consumer Loans [Member] | Total residential mortgages [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	16,397	15,772
Nonaccrual Loans	1,076	904
Total	17,473	16,676
Consumer Loans [Member] | Credit Card Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	781	808
Accruing Loans Contractually Past Due 90 days or More	15	20
Total	796	828	788
Consumer Loans [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment [Line Items]
Performing Loans	583	679
Nonaccrual Loans	5	8
Accruing Loans Contractually Past Due 90 days or More	27	27
Total	$ 615	$ 714	$ 733