Loans and Card Member Receivables - Aging by Origination Year (Details) - Other Loans - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due	30 days
2025/2024	$ 1,726	$ 4,964
2024/2023	4,063	1,591
2023/2022	1,235	362
2022/2021	214	10
2021/2020	9	14
Prior	68	58
Revolving Loans	2,363	2,233
Total	9,678	9,232
2025/2024, gross write-offs	0	13
2024/2023, gross write-offs	17	59
2023/2022, gross write-offs	15	42
2022/2021, gross write-offs	6	6
2021/2020, gross write-offs	0	0
Prior, gross write-offs	0	0
Revolving Loans, gross write-offs	24	87
Total gross write-offs	62	207
Loans over 90 days past due and accruing interest	6	6
Non-accruals	17	19
Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025/2024	1,726	4,950
2024/2023	4,047	1,578
2023/2022	1,223	356
2022/2021	210	10
2021/2020	9	14
Prior	66	57
Revolving Loans	2,339	2,209
Total	9,620	9,174
30 to 59 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025/2024	0	5
2024/2023	6	5
2023/2022	6	2
2022/2021	2	0
2021/2020	0	0
Prior	1	0
Revolving Loans	11	10
Total	26	22
60 to 89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025/2024	0	5
2024/2023	6	4
2023/2022	3	2
2022/2021	1	0
2021/2020	0	0
Prior	0	0
Revolving Loans	7	7
Total	17	18
90+ Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
2025/2024	0	4
2024/2023	4	4
2023/2022	3	2
2022/2021	1	0
2021/2020	0	0
Prior	1	1
Revolving Loans	6	7
Total	$ 15	$ 18