Loans and Allowance for Credit Losses - Carrying Amount of Covered Assets (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Covered Assets [Line Items]
Purchased Impaired Loans	$ 3,637	$ 3,775
Purchased Nonimpaired Loans	2,982	3,087
Other Assets	1,553	1,697
Covered loans	8,099	8,462
Total covered assets	8,172	8,559
Commercial [Member]
Covered Assets [Line Items]
Purchased Impaired Loans
Purchased Nonimpaired Loans	28	32
Other Assets
Covered loans	28	32
Commercial Real Estate [Member]
Covered Assets [Line Items]
Purchased Impaired Loans	649	738
Purchased Nonimpaired Loans	1,450	1,494
Other Assets
Covered loans	2,099	2,232
Residential Mortgages [Member]
Covered Assets [Line Items]
Purchased Impaired Loans	2,988	3,037
Purchased Nonimpaired Loans	855	890
Other Assets
Covered loans	3,843	3,927
Credit Card [Member]
Covered Assets [Line Items]
Purchased Impaired Loans
Purchased Nonimpaired Loans	5	5
Other Assets
Covered loans	5	5
Other Retail [Member]
Covered Assets [Line Items]
Purchased Impaired Loans
Purchased Nonimpaired Loans	644	666
Other Assets
Covered loans	644	666
Losses Reimbursable by FDIC [Member]
Covered Assets [Line Items]
Purchased Impaired Loans
Purchased Nonimpaired Loans
Other Assets	772	798
Covered loans	772	798
Unamortized Changes in FDIC asset [Member]
Covered Assets [Line Items]
Purchased Impaired Loans
Purchased Nonimpaired Loans
Other Assets	708	802
Covered loans	708	802
Covered Loans [Member]
Covered Assets [Line Items]
Purchased Impaired Loans	3,637	3,775
Purchased Nonimpaired Loans	2,982	3,087
Other Assets	1,480	1,600
Covered loans	8,099	8,462
Foreclosed Real Estate [Member]
Covered Assets [Line Items]
Purchased Impaired Loans
Purchased Nonimpaired Loans
Other Assets	73	97
Total covered assets	$ 73	$ 97