Loans and Allowance for Credit Losses - Summary of Loans by Portfolio Type and Delinquency Status of those that Continue to Accrue Interest and are Nonperforming (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 251,776	$ 244,327
Accruing 30-89 Days Past Due	948	1,113
Accruing 90 Days or More Past Due	825	945
Nonperforming	1,242	1,466
Total loans, excluding covered loans	250,000	242,570
Total loans	254,791	247,851
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	85,119	79,977
Accruing 30-89 Days Past Due	207	247
Accruing 90 Days or More Past Due	44	41
Nonperforming	169	112
Total loans, excluding covered loans	85,539	80,377
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	42,252	42,406
Accruing 30-89 Days Past Due	62	110
Accruing 90 Days or More Past Due	20	20
Nonperforming	144	259
Total loans, excluding covered loans	42,478	42,795
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	51,262	50,330
Accruing 30-89 Days Past Due	181	221
Accruing 90 Days or More Past Due	171	204
Nonperforming	735	864
Total loans, excluding covered loans	52,349	51,619
Credit Card [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	18,132	18,046
Accruing 30-89 Days Past Due	235	229
Accruing 90 Days or More Past Due	204	210
Nonperforming	12	30
Total loans, excluding covered loans	18,583	18,515
Other Retail [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	50,607	48,764
Accruing 30-89 Days Past Due	202	238
Accruing 90 Days or More Past Due	71	75
Nonperforming	171	187
Total loans, excluding covered loans	51,051	49,264
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	247,372	239,523
Accruing 30-89 Days Past Due	887	1,045
Accruing 90 Days or More Past Due	510	550
Nonperforming	1,231	1,452
Total loans, excluding covered loans	250,000	242,570
Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	4,404	4,804
Accruing 30-89 Days Past Due	61	68
Accruing 90 Days or More Past Due	315	395
Nonperforming	11	14
Total loans	$ 4,791	$ 5,281