Loans and Allowance for Loan Losses - Loans in Consumer Portfolio Segment Monitored for Credit Quality (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Jun. 30, 2012	Dec. 31, 2011
Schedule Of Financing Receivables Accrual And Non Accrual Status [Line Items]
Nonaccrual	$ 534		$ 638
Total consumer portfolio	24,829		23,355
Residential mortgage [Member]
Schedule Of Financing Receivables Accrual And Non Accrual Status [Line Items]
Accrual	21,010		19,340
Nonaccrual	325		285
Total consumer portfolio	21,335		19,625
Home equity and other consumer loans [Member]
Schedule Of Financing Receivables Accrual And Non Accrual Status [Line Items]
Accrual	3,442		3,706
Nonaccrual	52	21	24
Total consumer portfolio	3,494		3,730
Consumer portfolio [Member]
Schedule Of Financing Receivables Accrual And Non Accrual Status [Line Items]
Accrual	24,452		23,046
Nonaccrual	377		309
Total consumer portfolio	$ 24,829		$ 23,355