Loans and Allowance for Credit Losses - Summary of Loans by Portfolio Class and Delinquency Status of those that Continue to Accrue Interest and are Nonperforming (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 270,623	$ 269,994
Accruing 30-89 Days Past Due	946	1,081
Accruing 90 Days or More Past Due	718	764
Nonperforming	1,290	1,368
Total loans, excluding covered loans	269,942	269,371
Total loans	273,577	273,207
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	93,784	92,588
Accruing 30-89 Days Past Due	216	263
Accruing 90 Days or More Past Due	52	52
Nonperforming	439	483
Total loans, excluding covered loans	94,491	93,386
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	42,653	42,922
Accruing 30-89 Days Past Due	65	44
Accruing 90 Days or More Past Due	4	8
Nonperforming	110	124
Total loans, excluding covered loans	42,832	43,098
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	57,429	56,372
Accruing 30-89 Days Past Due	120	151
Accruing 90 Days or More Past Due	142	156
Nonperforming	575	595
Total loans, excluding covered loans	58,266	57,274
Other Retail [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	53,486	53,340
Accruing 30-89 Days Past Due	248	284
Accruing 90 Days or More Past Due	75	83
Nonperforming	157	157
Total loans, excluding covered loans	53,966	53,864
Credit Card [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	19,882	21,209
Accruing 30-89 Days Past Due	252	284
Accruing 90 Days or More Past Due	251	253
Nonperforming	2	3
Total loans, excluding covered loans	20,387	21,749
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	267,234	266,431
Accruing 30-89 Days Past Due	901	1,026
Accruing 90 Days or More Past Due	524	552
Nonperforming	1,283	1,362
Total loans, excluding covered loans	269,942	269,371
Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,389	3,563
Accruing 30-89 Days Past Due	45	55
Accruing 90 Days or More Past Due	194	212
Nonperforming	7	6
Total loans	$ 3,635	$ 3,836