Loans and Allowance for Credit Losses - Loan Modifications that Defaulted (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	$ 79	$ 38	$ 125	$ 73
Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	61	67	100	110
Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	35	54	75	81
Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	53	30	92	60
Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	29	29	54	58
Interest Rate Reduction and Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	20	1	33	1
Interest Rate Reduction, Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	4		5	1
Total loans, excluding loans purchased from GNMA mortgage pools | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	79	38	125	73
Total loans, excluding loans purchased from GNMA mortgage pools | Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	9	0	14
Total loans, excluding loans purchased from GNMA mortgage pools | Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	6	30	31	38
Total loans, excluding loans purchased from GNMA mortgage pools | Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	3	1	3	3
Loans purchased from GNMA mortgage pools | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Loans purchased from GNMA mortgage pools | Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	61	58	100	96
Loans purchased from GNMA mortgage pools | Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	29	24	44	43
Loans purchased from GNMA mortgage pools | Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	50	29	89	57
Commercial | Commercial | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	9	7	19	13
Commercial | Commercial | Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Commercial | Commercial | Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	1	0	21	0
Commercial | Commercial | Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Commercial | Commercial real estate | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	36	0	36	0
Commercial | Commercial real estate | Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Commercial | Commercial real estate | Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	24	0	24
Commercial | Commercial real estate | Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Consumer | Residential mortgages | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Consumer | Residential mortgages | Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	9	0	13
Consumer | Residential mortgages | Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	1	0	4
Consumer | Residential mortgages | Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	3	1	3	3
Consumer | Credit card | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	34	30	69	59
Consumer | Credit card | Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Consumer | Credit card | Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Consumer | Credit card | Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Consumer | Other retail | Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	1	1	1
Consumer | Other retail | Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	1
Consumer | Other retail | Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	5	5	10	10
Consumer | Other retail | Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	$ 0	$ 0	$ 0	$ 0