Variable Interest Entities and Securitizations - Carrying Amount of Consolidated and Unconsolidated VIEs (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	$ 5,186	$ 5,038
Carrying Amount of Assets	425,377	421,602
Carrying Amount of Liabilities	361,833	361,398
Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	24,450	26,619
Carrying Amount of Liabilities	12,812	12,436
Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	5,186	5,038
Carrying Amount of Liabilities	1,496	1,240
Affordable housing entities
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	4,786	4,602
VIE, nonconsolidated, carrying amount of assets included in certain investment structures	2,200	2,300
VIE, nonconsolidated, carrying amount of liabilities included in certain investment structures	602	596
Affordable housing entities | Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	264	242
Carrying Amount of Liabilities	28	17
Affordable housing entities | Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	4,786	4,602
Carrying Amount of Liabilities	1,496	1,240
Entities that provide capital to low-income and rural communities
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	0	0
Entities that provide capital to low-income and rural communities | Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	2,073	1,951
Carrying Amount of Liabilities	26	26
Entities that provide capital to low-income and rural communities | Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	0	0
Other
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	400	436
Other | Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	0	0
Other | Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	400	436
Carrying Amount of Liabilities	0	0
Total other VIEs
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	5,186	5,038
Total other VIEs | Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	2,337	2,193
Carrying Amount of Liabilities	54	43
Total other VIEs | Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	5,186	5,038
Carrying Amount of Liabilities	1,496	1,240
Credit card loan securitizations
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	0	0
Credit card loan securitizations | Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	20,604	22,066
Carrying Amount of Liabilities	11,489	10,338
Credit card loan securitizations | Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	0	0
Auto loan securitizations
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	0	0
Auto loan securitizations | Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	1,509	2,360
Carrying Amount of Liabilities	1,269	2,055
Auto loan securitizations | Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	0	0
Total securitization-related VIEs
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	0	0
Total securitization-related VIEs | Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	22,113	24,426
Carrying Amount of Liabilities	12,758	12,393
Total securitization-related VIEs | Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	$ 0	$ 0