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	Jun. 30, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 245,685	$ 244,327
Accruing 30-89 Days Past Due	914	1,113
Accruing 90 Days or More Past Due	801	945
Nonperforming	1,239	1,466
Total loans, excluding covered loans	243,655	242,570
Total loans	248,639	247,851
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	84,292	79,977
Accruing 30-89 Days Past Due	195	247
Accruing 90 Days or More Past Due	43	41
Nonperforming	90	112
Total loans, excluding covered loans	84,620	80,377
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	42,011	42,406
Accruing 30-89 Days Past Due	52	110
Accruing 90 Days or More Past Due	20	20
Nonperforming	175	259
Total loans, excluding covered loans	42,258	42,795
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	50,217	50,330
Accruing 30-89 Days Past Due	195	221
Accruing 90 Days or More Past Due	156	204
Nonperforming	769	864
Total loans, excluding covered loans	51,337	51,619
Credit Card [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	17,383	18,046
Accruing 30-89 Days Past Due	206	229
Accruing 90 Days or More Past Due	183	210
Nonperforming	16	30
Total loans, excluding covered loans	17,788	18,515
Other Retail [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	47,214	48,764
Accruing 30-89 Days Past Due	193	238
Accruing 90 Days or More Past Due	67	75
Nonperforming	178	187
Total loans, excluding covered loans	47,652	49,264
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	241,117	239,523
Accruing 30-89 Days Past Due	841	1,045
Accruing 90 Days or More Past Due	469	550
Nonperforming	1,228	1,452
Total loans, excluding covered loans	243,655	242,570
Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	4,568	4,804
Accruing 30-89 Days Past Due	73	68
Accruing 90 Days or More Past Due	332	395
Nonperforming	11	14
Total loans	$ 4,984	$ 5,281