Variable Interest Entities and Securitizations - Carrying Amount of Consolidated and Unconsolidated VIEs (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	$ 5,348	$ 5,413
Carrying Amount of Assets	421,296	390,365
Carrying Amount of Liabilities	365,251	332,354
Affordable housing entities
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	4,553	4,559
VIE, nonconsolidated, carrying amount of assets included in certain investment structures	2,300	2,300
VIE, nonconsolidated, carrying amount of liabilities included in certain investment structures	652	741
Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	0	0
Other
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	476	502
Total other VIEs
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	5,029	5,061
Credit card loan securitizations
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	0	0
Auto loan securitizations
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	0	0
Home loan
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	319	352
Total securitization-related VIEs
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	319	352
Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	30,404	35,519
Carrying Amount of Liabilities	15,890	18,201
Consolidated | Affordable housing entities
Variable Interest Entity [Line Items]
Carrying Amount of Assets	248	236
Carrying Amount of Liabilities	18	7
Consolidated | Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Carrying Amount of Assets	2,030	1,889
Carrying Amount of Liabilities	69	69
Consolidated | Other
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	0	0
Consolidated | Total other VIEs
Variable Interest Entity [Line Items]
Carrying Amount of Assets	2,278	2,125
Carrying Amount of Liabilities	87	76
Consolidated | Credit card loan securitizations
Variable Interest Entity [Line Items]
Carrying Amount of Assets	25,119	31,112
Carrying Amount of Liabilities	13,141	16,113
Consolidated | Auto loan securitizations
Variable Interest Entity [Line Items]
Carrying Amount of Assets	3,007	2,282
Carrying Amount of Liabilities	2,662	2,012
Consolidated | Home loan
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	0	0
Consolidated | Total securitization-related VIEs
Variable Interest Entity [Line Items]
Carrying Amount of Assets	28,126	33,394
Carrying Amount of Liabilities	15,803	18,125
Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	5,085	5,127
Carrying Amount of Liabilities	1,262	1,289
Unconsolidated | Affordable housing entities
Variable Interest Entity [Line Items]
Carrying Amount of Assets	4,553	4,559
Carrying Amount of Liabilities	1,262	1,289
Unconsolidated | Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	0	0
Unconsolidated | Other
Variable Interest Entity [Line Items]
Carrying Amount of Assets	476	502
Carrying Amount of Liabilities	0	0
Unconsolidated | Total other VIEs
Variable Interest Entity [Line Items]
Carrying Amount of Assets	5,029	5,061
Carrying Amount of Liabilities	1,262	1,289
Unconsolidated | Credit card loan securitizations
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	0	0
Unconsolidated | Auto loan securitizations
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	0	0
Unconsolidated | Home loan
Variable Interest Entity [Line Items]
Carrying Amount of Assets	56	66
Carrying Amount of Liabilities	0	0
Unconsolidated | Total securitization-related VIEs
Variable Interest Entity [Line Items]
Carrying Amount of Assets	56	66
Carrying Amount of Liabilities	$ 0	$ 0