Loans and Allowance for Credit Losses - Summary of Loans Modified as TDRs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014 SecurityLoan	Sep. 30, 2013 SecurityLoan	Sep. 30, 2014 SecurityLoan	Sep. 30, 2013 SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans	10,809	10,584	32,941	33,909
Pre-Modification Outstanding Loan Balance	$ 447	$ 559	$ 1,439	$ 1,672
Post-Modification Outstanding Loan Balance	444	529	1,408	1,589
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	448	551	1,633	1,962
Pre-Modification Outstanding Loan Balance	28	62	181	150
Post-Modification Outstanding Loan Balance	26	60	169	140
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	27	48	54	147
Pre-Modification Outstanding Loan Balance	14	76	33	193
Post-Modification Outstanding Loan Balance	13	73	28	186
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	525	338	1,732	1,575
Pre-Modification Outstanding Loan Balance	71	42	232	214
Post-Modification Outstanding Loan Balance	70	42	231	210
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	6,708	6,447	20,040	20,147
Pre-Modification Outstanding Loan Balance	35	39	111	122
Post-Modification Outstanding Loan Balance	36	38	112	122
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	810	847	2,246	3,519
Pre-Modification Outstanding Loan Balance	18	21	52	86
Post-Modification Outstanding Loan Balance	18	21	52	85
Total Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	8,518	8,231	25,705	27,350
Pre-Modification Outstanding Loan Balance	166	240	609	765
Post-Modification Outstanding Loan Balance	163	234	592	743
Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2,273	2,315	7,198	6,450
Pre-Modification Outstanding Loan Balance	278	300	816	822
Post-Modification Outstanding Loan Balance	278	284	803	782
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	18	38	38	109
Pre-Modification Outstanding Loan Balance	3	19	14	85
Post-Modification Outstanding Loan Balance	$ 3	$ 11	$ 13	$ 64