Loans and Allowance for Credit Losses - Composition of Loan Portfolio (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Accounts Notes And Loans Receivable Classified [Abstract]
Commercial	$ 62,910	$ 60,742
Lease financing	5,275	5,481
Total commercial	68,185	66,223
Commercial Real Estate
Commercial mortgages	31,630	31,005
Construction and development	6,668	5,948
Total commercial real estate	38,298	36,953
Residential mortgages	34,651	32,648
Home equity loans, first liens	13,102	11,370
Total residential mortgages	47,753	44,018
Credit Card	16,649	17,115
Retail leasing	5,802	5,419
Home equity and second mortgages	15,816	16,726
Revolving credit	3,260	3,332
Installment	5,635	5,463
Automobile	12,807	12,593
Student	3,785	4,179
Total other retail	47,105	47,712
Total loans, excluding covered loans	217,990	212,021
Covered loans	9,985	11,308
Total loans	$ 227,975	$ 223,329
Commercial, Percentage	27.60%	27.20%
Lease financing, Percentage	2.30%	2.50%
Total commercial, Percentage	29.90%	29.70%
Commercial mortgages, Percentage	13.90%	13.90%
Construction and development, Percentage	2.90%	2.60%
Total commercial real estate, Percentage	16.80%	16.50%
Residential mortgages, Percentage	15.20%	14.60%
Home equity loans, first liens, Percentage	5.70%	5.10%
Total residential mortgages, Percentage	20.90%	19.70%
Credit Card, Percentage	7.30%	7.70%
Retail leasing, Percentage	2.60%	2.40%
Home equity and second mortgages, Percentage	6.90%	7.50%
Revolving credit, Percentage	1.40%	1.50%
Installment, Percentage	2.50%	2.40%
Automobile, Percentage	5.60%	5.60%
Student, Percentage	1.70%	1.90%
Total other retail, Percentage	20.70%	21.30%
Total loans, excluding covered loans, Percentage	95.60%	94.90%
Covered Loans, Percentage	4.40%	5.10%
Total loans, Percentage	100.00%	100.00%