Loans and Card Member Receivables - Performance (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Modifications [Line Items]
Account Balances			$ 1,733
Current
Financing Receivable, Modifications [Line Items]
Account Balances	$ 2,863	$ 2,785
30-89 Days Past Due
Financing Receivable, Modifications [Line Items]
Account Balances	220	231
90+ Days Past Due
Financing Receivable, Modifications [Line Items]
Account Balances	89	73
Card Member loans | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances			781
Card Member loans | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances			267
Card Member loans | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances			0
Card Member loans | Current | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances	1,615	1,433
Card Member loans | Current | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	568	489
Card Member loans | Current | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances	0	0
Card Member loans | 30-89 Days Past Due | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances	110	103
Card Member loans | 30-89 Days Past Due | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	56	45
Card Member loans | 30-89 Days Past Due | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances	0	0
Card Member loans | 90+ Days Past Due | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances	45	36
Card Member loans | 90+ Days Past Due | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	22	16
Card Member loans | 90+ Days Past Due | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances	0	0
Card Member receivables | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances			257
Card Member receivables | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances			403
Card Member receivables | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances			6
Card Member receivables | Current | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances	234	314
Card Member receivables | Current | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	357	479
Card Member receivables | Current | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances	10	11
Card Member receivables | 30-89 Days Past Due | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances	16	25
Card Member receivables | 30-89 Days Past Due | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	31	52
Card Member receivables | 30-89 Days Past Due | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances	2	2
Card Member receivables | 90+ Days Past Due | Consumer
Financing Receivable, Modifications [Line Items]
Account Balances	6	7
Card Member receivables | 90+ Days Past Due | Small Business
Financing Receivable, Modifications [Line Items]
Account Balances	13	12
Card Member receivables | 90+ Days Past Due | Corporate
Financing Receivable, Modifications [Line Items]
Account Balances	1	0
Other Loans
Financing Receivable, Modifications [Line Items]
Account Balances			$ 19
Other Loans | Current
Financing Receivable, Modifications [Line Items]
Account Balances	79	59
Other Loans | 30-89 Days Past Due
Financing Receivable, Modifications [Line Items]
Account Balances	5	4
Other Loans | 90+ Days Past Due
Financing Receivable, Modifications [Line Items]
Account Balances	$ 2	$ 2