Loans and Allowance for Credit Losses - Carrying Amount of Covered Assets (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Covered Assets [Line Items]
Purchased Impaired Loans	$ 3,463	$ 3,775
Purchased Nonimpaired Loans	2,676	3,087
Other Assets	1,367	1,697
Covered loans	7,448	8,462
Total covered assets	7,506	8,559
Commercial [Member]
Covered Assets [Line Items]
Purchased Impaired Loans
Purchased Nonimpaired Loans	27	32
Other Assets
Covered loans	27	32
Commercial Real Estate [Member]
Covered Assets [Line Items]
Purchased Impaired Loans	533	738
Purchased Nonimpaired Loans	1,206	1,494
Other Assets
Covered loans	1,739	2,232
Residential Mortgages [Member]
Covered Assets [Line Items]
Purchased Impaired Loans	2,930	3,037
Purchased Nonimpaired Loans	811	890
Other Assets
Covered loans	3,741	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	627	666
Other Assets
Covered loans	627	666
Losses Reimbursable by FDIC [Member]
Covered Assets [Line Items]
Purchased Impaired Loans
Purchased Nonimpaired Loans
Other Assets	731	798
Covered loans	731	798
Unamortized Changes in FDIC asset [Member]
Covered Assets [Line Items]
Purchased Impaired Loans
Purchased Nonimpaired Loans
Other Assets	578	802
Covered loans	578	802
Covered Loans [Member]
Covered Assets [Line Items]
Purchased Impaired Loans	3,463	3,775
Purchased Nonimpaired Loans	2,676	3,087
Other Assets	1,309	1,600
Covered loans	7,448	8,462
Foreclosed Real Estate [Member]
Covered Assets [Line Items]
Purchased Impaired Loans
Purchased Nonimpaired Loans
Other Assets	58	97
Total covered assets	$ 58	$ 97