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	Mar. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	$ 261,408	$ 257,721
Accruing 30-89 Days Past Due	885	1,105
Accruing 90 Days or More Past Due	804	831
Nonperforming	1,425	1,192
Total loans, excluding covered loans	260,093	256,253
Total loans	264,522	260,849
Commercial [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	90,561	87,863
Accruing 30-89 Days Past Due	195	317
Accruing 90 Days or More Past Due	48	48
Nonperforming	473	174
Total loans, excluding covered loans	91,277	88,402
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	42,541	41,907
Accruing 30-89 Days Past Due	82	89
Accruing 90 Days or More Past Due	16	14
Nonperforming	104	127
Total loans, excluding covered loans	42,743	42,137
Residential Mortgages [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	53,975	52,438
Accruing 30-89 Days Past Due	134	170
Accruing 90 Days or More Past Due	169	176
Nonperforming	677	712
Total loans, excluding covered loans	54,955	53,496
Other Retail [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	50,734	50,745
Accruing 30-89 Days Past Due	195	224
Accruing 90 Days or More Past Due	75	75
Nonperforming	157	162
Total loans, excluding covered loans	51,161	51,206
Credit Card [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	19,511	20,532
Accruing 30-89 Days Past Due	219	243
Accruing 90 Days or More Past Due	220	228
Nonperforming	7	9
Total loans, excluding covered loans	19,957	21,012
Total Loans, Excluding Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	257,322	253,485
Accruing 30-89 Days Past Due	825	1,043
Accruing 90 Days or More Past Due	528	541
Nonperforming	1,418	1,184
Total loans, excluding covered loans	260,093	256,253
Covered Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	4,086	4,236
Accruing 30-89 Days Past Due	60	62
Accruing 90 Days or More Past Due	276	290
Nonperforming	7	8
Total loans	$ 4,429	$ 4,596