Variable Interest Entities and Securitizations - Carrying Amount of Consolidated and Unconsolidated VIEs (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	$ 5,087	$ 5,038
Carrying Amount of Assets	425,175	421,602
Carrying Amount of Liabilities	363,987	361,398
Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	26,463	26,619
Carrying Amount of Liabilities	12,166	12,436
Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	5,087	5,038
Carrying Amount of Liabilities	1,319	1,240
Affordable housing entities
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	4,676	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	575	596
Affordable housing entities | Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	251	242
Carrying Amount of Liabilities	17	17
Affordable housing entities | Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	4,676	4,602
Carrying Amount of Liabilities	1,319	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	1,999	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	411	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	411	436
Carrying Amount of Liabilities	0	0
Total other VIEs
Variable Interest Entity [Line Items]
Maximum Exposure to Loss	5,087	5,038
Total other VIEs | Consolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	2,250	2,193
Carrying Amount of Liabilities	43	43
Total other VIEs | Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	5,087	5,038
Carrying Amount of Liabilities	1,319	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	22,146	22,066
Carrying Amount of Liabilities	10,339	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	2,067	2,360
Carrying Amount of Liabilities	1,784	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	24,213	24,426
Carrying Amount of Liabilities	12,123	12,393
Total securitization-related VIEs | Unconsolidated
Variable Interest Entity [Line Items]
Carrying Amount of Assets	0	0
Carrying Amount of Liabilities	$ 0	$ 0