Loans and Allowance for Credit Losses - Loans Modified as TDRs (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013 SecurityLoan	Sep. 30, 2012 SecurityLoan	Sep. 30, 2013 SecurityLoan	Sep. 30, 2012 SecurityLoan
Financing Receivable, Modifications [Line Items]
Number of Loans	10,584	29,834	33,909	63,784
Pre-Modification Outstanding Loan Balance	$ 559	$ 1,409	$ 1,672	$ 2,905
Post-Modification Outstanding Loan Balance	529	1,332	1,589	2,817
Commercial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	551	1,754	1,962	4,081
Pre-Modification Outstanding Loan Balance	62	54	150	215
Post-Modification Outstanding Loan Balance	60	58	140	195
Commercial Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	48	63	147	245
Pre-Modification Outstanding Loan Balance	76	91	193	416
Post-Modification Outstanding Loan Balance	73	80	186	390
Residential Mortgages [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	338	2,717	1,575	3,788
Pre-Modification Outstanding Loan Balance	42	344	214	529
Post-Modification Outstanding Loan Balance	42	336	210	517
Credit Card [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	6,447	14,137	20,147	39,040
Pre-Modification Outstanding Loan Balance	39	52	122	189
Post-Modification Outstanding Loan Balance	38	67	122	203
Other Retail [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	847	6,231	3,519	8,028
Pre-Modification Outstanding Loan Balance	21	159	86	194
Post-Modification Outstanding Loan Balance	21	156	85	191
Total Loans, Excluding GNMA and Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	8,231	24,902	27,350	55,182
Pre-Modification Outstanding Loan Balance	240	700	765	1,543
Post-Modification Outstanding Loan Balance	234	697	743	1,496
Loans Purchased from GNMA Mortgage Pools [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	2,315	4,859	6,450	8,436
Pre-Modification Outstanding Loan Balance	300	660	822	1,116
Post-Modification Outstanding Loan Balance	284	589	782	1,087
Covered Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans	38	73	109	166
Pre-Modification Outstanding Loan Balance	19	49	85	246
Post-Modification Outstanding Loan Balance	$ 11	$ 46	$ 64	$ 234