Loans and Allowance for Credit Losses - Loan Modifications that Defaulted (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	$ 46	$ 79	$ 96	$ 125
Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	25	61	71	100
Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	160	35	234	75
Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	26	53	92	92
Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	14	29	46	54
Interest Rate Reduction and Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	9	20	37	33
Interest Rate Reduction, Payment Delay and Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	3	4	9	5
Total loans, excluding loans purchased from GNMA mortgage pools \| Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	46	79	96	125
Total loans, excluding loans purchased from GNMA mortgage pools \| Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Total loans, excluding loans purchased from GNMA mortgage pools \| Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	136	6	165	31
Total loans, excluding loans purchased from GNMA mortgage pools \| Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	2	3	4	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	25	61	71	100
Loans purchased from GNMA mortgage pools \| Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	24	29	69	44
Loans purchased from GNMA mortgage pools \| Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	24	50	88	89
Commercial \| Commercial \| Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
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	51	1	52	21
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	0	36	0	36
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	80	0	103	0
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	0	0	0
Consumer \| Residential mortgages \| Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	1	0	2	0
Consumer \| Residential mortgages \| Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	2	3	4	3
Consumer \| Credit card \| Interest Rate Reduction
Financing Receivable, Modified [Line Items]
Loans that defaulted	45	43	95	88
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	1	0	1	1
Consumer \| Other retail \| Payment Delay
Financing Receivable, Modified [Line Items]
Loans that defaulted	0	0	0	0
Consumer \| Other retail \| Term Extension
Financing Receivable, Modified [Line Items]
Loans that defaulted	4	5	8	10
Consumer \| Other retail \| Multiple Modifications
Financing Receivable, Modified [Line Items]
Loans that defaulted	$ 0	$ 0	$ 0	$ 0