Loans and Allowance for Credit Losses - Loans Modified by Modification Type (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Financing Receivable, Modified [Line Items]
Modifications	$ 1,513	$ 1,532
Percent of Class Total	0.40%	0.40%
Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 163	$ 155
Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	673	511
Term Extension
Financing Receivable, Modified [Line Items]
Modifications	521	721
Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	156	145
Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Modifications	76	88
Interest Rate Reduction and Term Extension
Financing Receivable, Modified [Line Items]
Modifications	65	53
Interest Rate Reduction, Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Modifications	15	4
Total loans, excluding loans purchased from GNMA mortgage pools
Financing Receivable, Modified [Line Items]
Modifications	$ 906	$ 880
Percent of Class Total	0.20%	0.20%
Total loans, excluding loans purchased from GNMA mortgage pools | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 163	$ 154
Total loans, excluding loans purchased from GNMA mortgage pools | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	293	21
Total loans, excluding loans purchased from GNMA mortgage pools | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	417	653
Total loans, excluding loans purchased from GNMA mortgage pools | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	33	52
Loans purchased from GNMA mortgage pools
Financing Receivable, Modified [Line Items]
Modifications	$ 607	$ 652
Percent of Class Total	0.50%	0.60%
Loans purchased from GNMA mortgage pools | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 0	$ 1
Loans purchased from GNMA mortgage pools | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	380	490
Loans purchased from GNMA mortgage pools | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	104	68
Loans purchased from GNMA mortgage pools | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	123	93
Commercial | Commercial
Financing Receivable, Modified [Line Items]
Modifications	$ 193	$ 353
Percent of Class Total	0.10%	0.30%
Commercial | Commercial | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 27	$ 25
Commercial | Commercial | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	2	0
Commercial | Commercial | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	143	328
Commercial | Commercial | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	21	0
Commercial | Commercial real estate
Financing Receivable, Modified [Line Items]
Modifications	$ 245	$ 332
Percent of Class Total	0.50%	0.60%
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	242	282
Commercial | Commercial real estate | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	3	50
Consumer | Residential mortgages
Financing Receivable, Modified [Line Items]
Modifications	$ 288	$ 27
Percent of Class Total	0.20%	0.00%
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	281	20
Consumer | Residential mortgages | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	2	5
Consumer | Residential mortgages | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	5	2
Consumer | Credit card
Financing Receivable, Modified [Line Items]
Modifications	$ 137	$ 126
Percent of Class Total	0.50%	0.50%
Consumer | Credit card | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 134	$ 126
Consumer | Credit card | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	3	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	$ 43	$ 42
Percent of Class Total	0.10%	0.10%
Consumer | Other retail | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Modifications	$ 2	$ 3
Consumer | Other retail | Payment Delay
Financing Receivable, Modified [Line Items]
Modifications	7	1
Consumer | Other retail | Term Extension
Financing Receivable, Modified [Line Items]
Modifications	30	38
Consumer | Other retail | Multiple Modifications
Financing Receivable, Modified [Line Items]
Modifications	$ 4	$ 0