Loans and Card Member Receivables - Aging (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
90+ days past due and still accruing interest		$ 309
Non-accruals		$ 191
Loans and receivables threshold period for write off		180 days
Card Member Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due	30 days
Financing receivables, gross	$ 117,978	$ 107,964
Loans and receivables threshold period for write off	180 days
Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 90,900	84,964
90+ days past due and still accruing interest	369	252
Non-accruals	272	155
Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	27,022	22,947
90+ days past due and still accruing interest	109	54
Non-accruals	73	34
Card Member Loans | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	56	53
90+ days past due and still accruing interest	0	0
Non-accruals	$ 0	0
Card Member Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due	30 days
Financing receivables, gross	$ 58,825	57,613
Loans and receivables threshold period for write off	180 days
Card Member Receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 22,239	22,885
90+ days past due and still accruing interest	0	0
Non-accruals	0	0
Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	19,575	19,629
90+ days past due and still accruing interest	0	0
Non-accruals	0	0
Card Member Receivables | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	17,011	15,099
90+ days past due and still accruing interest	0	0
Non-accruals	0	0
Current | Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	89,751	84,102
Current | Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	26,678	22,731
Current | Card Member Receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	22,018	22,634
Current | Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	19,327	19,330
30 to 59 Days Past Due | Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	363	281
30 to 59 Days Past Due | Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	114	81
30 to 59 Days Past Due | Card Member Receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	74	83
30 to 59 Days Past Due | Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	93	120
60 to 89 Days Past Due | Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	258	198
60 to 89 Days Past Due | Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	72	49
60 to 89 Days Past Due | Card Member Receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	49	56
60 to 89 Days Past Due | Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	53	69
90+ Days Past Due | Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	528	383
90+ Days Past Due | Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	158	86
90+ Days Past Due | Card Member Loans | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	0	0
90+ Days Past Due | Card Member Receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	98	112
90+ Days Past Due | Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	102	110
90+ Days Past Due | Card Member Receivables | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 79	$ 85