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	Sep. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 268,165	$ 257,721
Accruing 30-89 Days Past Due	976	1,105
Accruing 90 Days or More Past Due	748	831
Nonperforming	1,400	1,192
Total loans, excluding covered loans	267,268	256,253
Total loans	271,289	260,849
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	92,414	87,863
Accruing 30-89 Days Past Due	221	317
Accruing 90 Days or More Past Due	49	48
Nonperforming	517	174
Total loans, excluding covered loans	93,201	88,402
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	43,320	41,907
Accruing 30-89 Days Past Due	36	89
Accruing 90 Days or More Past Due	7	14
Nonperforming	105	127
Total loans, excluding covered loans	43,468	42,137
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	55,310	52,438
Accruing 30-89 Days Past Due	146	170
Accruing 90 Days or More Past Due	159	176
Nonperforming	614	712
Total loans, excluding covered loans	56,229	53,496
Other Retail [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	53,183	50,745
Accruing 30-89 Days Past Due	254	224
Accruing 90 Days or More Past Due	74	75
Nonperforming	153	162
Total loans, excluding covered loans	53,664	51,206
Credit Card [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	20,209	20,532
Accruing 30-89 Days Past Due	264	243
Accruing 90 Days or More Past Due	229	228
Nonperforming	4	9
Total loans, excluding covered loans	20,706	21,012
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	264,436	253,485
Accruing 30-89 Days Past Due	921	1,043
Accruing 90 Days or More Past Due	518	541
Nonperforming	1,393	1,184
Total loans, excluding covered loans	267,268	256,253
Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	3,729	4,236
Accruing 30-89 Days Past Due	55	62
Accruing 90 Days or More Past Due	230	290
Nonperforming	7	8
Total loans	$ 4,021	$ 4,596