Loans and Card Member Receivables - Aging by Origination Year (Details) - Other Loans - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due	30 days
2025/2024	$ 3,191	$ 4,964
2024/2023	3,339	1,591
2023/2022	936	362
2022/2021	120	10
2021/2020	8	14
Prior	64	58
Revolving Loans	2,445	2,233
Total	10,103	9,232
2025/2024, gross write-offs	2	13
2024/2023, gross write-offs	36	59
2023/2022, gross write-offs	28	42
2022/2021, gross write-offs	9	6
2021/2020, gross write-offs	0	0
Prior, gross write-offs	0	0
Revolving Loans, gross write-offs	46	87
Total gross write-offs	121	207
Loans over 90 days past due and accruing interest	6	6
Non-accruals	19	19
Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025/2024	3,189	4,950
2024/2023	3,321	1,578
2023/2022	928	356
2022/2021	117	10
2021/2020	8	14
Prior	62	57
Revolving Loans	2,418	2,209
Total	10,043	9,174
30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025/2024	1	5
2024/2023	7	5
2023/2022	2	2
2022/2021	1	0
2021/2020	0	0
Prior	1	0
Revolving Loans	10	10
Total	22	22
60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025/2024	1	5
2024/2023	6	4
2023/2022	3	2
2022/2021	1	0
2021/2020	0	0
Prior	0	0
Revolving Loans	8	7
Total	19	18
90+ Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025/2024	0	4
2024/2023	5	4
2023/2022	3	2
2022/2021	1	0
2021/2020	0	0
Prior	1	1
Revolving Loans	9	7
Total	$ 19	$ 18