Loans and Allowance for Credit Losses - Loans Modified by Modification Type (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Modified [Line Items]
Modifications	$ 1,631	$ 1,123	$ 2,848	$ 1,879
Percent of Class Total	0.40%	0.30%	0.80%	0.50%
Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 219	$ 106	$ 355	$ 337
Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	483	546	937	869
Term Extension
Financing Receivable, Modified [Line Items]
Modifications	793	368	1,335	511
Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	136	103	221	162
Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Modifications	111	100	189	151
Interest Rate Reduction and Term Extension
Financing Receivable, Modified [Line Items]
Modifications	17	2	20	5
Interest Rate Reduction, Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Modifications	8	1	12	6
Total loans, excluding loans purchased from GNMA mortgage pools
Financing Receivable, Modified [Line Items]
Modifications	$ 926	$ 486	$ 1,562	$ 940
Percent of Class Total	0.20%	0.10%	0.40%	0.20%
Total loans, excluding loans purchased from GNMA mortgage pools | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 219	$ 106	$ 354	$ 337
Total loans, excluding loans purchased from GNMA mortgage pools | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	9	93	29	220
Total loans, excluding loans purchased from GNMA mortgage pools | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	684	282	1,162	364
Total loans, excluding loans purchased from GNMA mortgage pools | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	14	5	17	19
Loans purchased from GNMA mortgage pools
Financing Receivable, Modified [Line Items]
Modifications	$ 705	$ 637	$ 1,286	$ 939
Percent of Class Total	0.60%	0.60%	1.10%	0.80%
Loans purchased from GNMA mortgage pools | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 0	$ 0	$ 1	$ 0
Loans purchased from GNMA mortgage pools | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	474	453	908	649
Loans purchased from GNMA mortgage pools | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	109	86	173	147
Loans purchased from GNMA mortgage pools | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	122	98	204	143
Commercial | Commercial
Financing Receivable, Modified [Line Items]
Modifications	$ 276	$ 149	$ 496	$ 318
Percent of Class Total	0.20%	0.10%	0.40%	0.20%
Commercial | Commercial | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 23	$ 13	$ 44	$ 159
Commercial | Commercial | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	0	0	0	0
Commercial | Commercial | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	253	136	452	159
Commercial | Commercial | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	0	0	0	0
Commercial | Commercial real estate
Financing Receivable, Modified [Line Items]
Modifications	$ 476	$ 101	$ 714	$ 109
Percent of Class Total	0.90%	0.20%	1.40%	0.20%
Commercial | Commercial real estate | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 78	$ 0	$ 78	$ 0
Commercial | Commercial real estate | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	0	0	0	0
Commercial | Commercial real estate | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	391	101	629	109
Commercial | Commercial real estate | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	7	0	7	0
Consumer | Residential mortgages
Financing Receivable, Modified [Line Items]
Modifications	$ 22	$ 89	$ 49	$ 233
Percent of Class Total	0.00%	0.10%	0.00%	0.20%
Consumer | Residential mortgages | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 0	$ 0	$ 0	$ 0
Consumer | Residential mortgages | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	9	79	28	202
Consumer | Residential mortgages | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	7	6	12	15
Consumer | Residential mortgages | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	6	4	9	16
Consumer | Credit card
Financing Receivable, Modified [Line Items]
Modifications	$ 116	$ 91	$ 228	$ 174
Percent of Class Total	0.40%	0.30%	0.80%	0.70%
Consumer | Credit card | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 116	$ 91	$ 228	$ 174
Consumer | Credit card | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	0	0	0	0
Consumer | Credit card | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	0	0	0	0
Consumer | Credit card | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	0	0	0	0
Consumer | Other retail
Financing Receivable, Modified [Line Items]
Modifications	$ 36	$ 56	$ 75	$ 106
Percent of Class Total	0.10%	0.10%	0.20%	0.20%
Consumer | Other retail | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 2	$ 2	$ 4	$ 4
Consumer | Other retail | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	0	14	1	18
Consumer | Other retail | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	33	39	69	81
Consumer | Other retail | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	$ 1	$ 1	$ 1	$ 3