Composition of Loan Portfolio (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Commercial	$ 57,415	$ 50,734
Lease financing	5,495	5,914
Total commercial	62,910	56,648
Commercial real estate
Commercial mortgages	30,831	29,664
Construction and development	5,982	6,187
Total commercial real estate	36,813	35,851
Residential mortgages	31,504	28,669
Home equity loans, first liens	10,398	8,413
Total residential mortgages	41,902	37,082
Credit card	16,402	17,360
Retail leasing	5,332	5,118
Home equity and second mortgages	17,119	18,131
Revolving credit	3,320	3,344
Installment	5,474	5,348
Automobile	12,431	11,508
Student	4,289	4,658
Total other retail	47,965	48,107
Total loans, excluding covered loans	205,992	195,048
Covered loans	12,158	14,787
Total loans	$ 218,150	$ 209,835
Commercial, Percentage	26.30%	24.20%
Lease financing, Percentage	2.50%	2.80%
Total commercial, Percentage	28.80%	27.00%
Commercial mortgages, Percentage	14.10%	14.10%
Construction and development, Percentage	2.80%	3.00%
Total commercial real estate, Percentage	16.90%	17.10%
Residential mortgages, Percentage	14.40%	13.70%
Home equity loans, first liens, Percentage	4.80%	4.00%
Total residential mortgages, Percentage	19.20%	17.70%
Credit card, Percentage	7.50%	8.30%
Retail leasing, Percentage	2.40%	2.40%
Home equity and second mortgages, Percentage	7.90%	8.60%
Revolving Credit, Percentage	1.50%	1.60%
Installment, Percentage	2.50%	2.60%
Automobile, Percentage	5.70%	5.50%
Student, Percentage	2.00%	2.20%
Total other retail, Percentage	22.00%	22.90%
Total loans, excluding covered loans, Percentage	94.40%	93.00%
Covered loans, Percentage	5.60%	7.00%
Total loans, Percentage	100.00%	100.00%