Loans and Allowance for Loan Losses - Loans in Consumer Portfolio Segment Monitored for Credit Quality (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule Of Financing Receivables Accrual And Non Accrual Status [Line Items]
Total consumer portfolio	$ 23,835	$ 22,705
Total consumer portfolio	3,456	3,647
Nonaccrual	520	505
Total consumer portfolio	27,291	26,352
Residential mortgage [Member]
Schedule Of Financing Receivables Accrual And Non Accrual Status [Line Items]
Total consumer portfolio	23,835	22,705
Accrual	23,520	22,399
Nonaccrual	315	306
Home equity and other consumer loans [Member]
Schedule Of Financing Receivables Accrual And Non Accrual Status [Line Items]
Total consumer portfolio	3,456	3,647
Accrual	3,406	3,591
Nonaccrual	50	56
Consumer [Member]
Schedule Of Financing Receivables Accrual And Non Accrual Status [Line Items]
Accrual	26,926	25,990
Nonaccrual	365	362
Total consumer portfolio	27,291	26,352
Purchased Credit Impaired [Member]
Schedule Of Financing Receivables Accrual And Non Accrual Status [Line Items]
Accrual	270	288
Nonaccrual	1
Total consumer portfolio	271	288
Consumer portfolio [Member]
Schedule Of Financing Receivables Accrual And Non Accrual Status [Line Items]
Accrual	27,196	26,278
Nonaccrual	366	362
Total consumer portfolio	$ 27,562	$ 26,640