Loans and Allowance for Credit Losses - Loans Modified by Modification Type (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Financing Receivable, Modified [Line Items]
Modifications	$ 1,532	$ 899
Percent of Class Total	0.40%	0.20%
Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 155	$ 210
Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	511	384
Term Extension
Financing Receivable, Modified [Line Items]
Modifications	721	216
Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	145	89
Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Modifications	88	52
Interest Rate Reduction and Term Extension
Financing Receivable, Modified [Line Items]
Modifications	53	32
Interest Rate Reduction, Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Modifications	4	5
Total loans, excluding loans purchased from GNMA mortgage pools
Financing Receivable, Modified [Line Items]
Modifications	$ 880	$ 546
Percent of Class Total	0.20%	0.10%
Total loans, excluding loans purchased from GNMA mortgage pools | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 154	$ 210
Total loans, excluding loans purchased from GNMA mortgage pools | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	21	141
Total loans, excluding loans purchased from GNMA mortgage pools | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	653	153
Total loans, excluding loans purchased from GNMA mortgage pools | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	52	42
Loans purchased from GNMA mortgage pools
Financing Receivable, Modified [Line Items]
Modifications	$ 652	$ 353
Percent of Class Total	0.60%	0.30%
Loans purchased from GNMA mortgage pools | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 1	$ 0
Loans purchased from GNMA mortgage pools | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	490	243
Loans purchased from GNMA mortgage pools | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	68	63
Loans purchased from GNMA mortgage pools | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	93	47
Commercial | Commercial
Financing Receivable, Modified [Line Items]
Modifications	$ 353	$ 182
Percent of Class Total	0.30%	0.10%
Commercial | Commercial | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 25	$ 114
Commercial | Commercial | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	0	0
Commercial | Commercial | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	328	68
Commercial | Commercial | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	0	0
Commercial | Commercial real estate
Financing Receivable, Modified [Line Items]
Modifications	$ 332	$ 40
Percent of Class Total	0.60%	0.10%
Commercial | Commercial real estate | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 0	$ 0
Commercial | Commercial real estate | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	0	0
Commercial | Commercial real estate | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	282	12
Commercial | Commercial real estate | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	50	28
Consumer | Residential mortgages
Financing Receivable, Modified [Line Items]
Modifications	$ 27	$ 152
Percent of Class Total	0.00%	0.10%
Consumer | Residential mortgages | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 0	$ 0
Consumer | Residential mortgages | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	20	130
Consumer | Residential mortgages | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	5	10
Consumer | Residential mortgages | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	2	12
Consumer | Credit card
Financing Receivable, Modified [Line Items]
Modifications	$ 126	$ 94
Percent of Class Total	0.50%	0.40%
Consumer | Credit card | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 126	$ 94
Consumer | Credit card | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	0	0
Consumer | Credit card | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	0	0
Consumer | Credit card | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	0	0
Consumer | Other retail
Financing Receivable, Modified [Line Items]
Modifications	$ 42	$ 78
Percent of Class Total	0.10%	0.10%
Consumer | Other retail | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 3	$ 2
Consumer | Other retail | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	1	11
Consumer | Other retail | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	38	63
Consumer | Other retail | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	$ 0	$ 2