Loans and Card Member Receivables - Aging (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans over 90 days past due and accruing interest		$ 309	$ 169
Non-accruals		$ 191	96
Threshold period past due 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	$ 125,995	$ 107,964
Threshold period past due for write-off	180 days
Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 98,111	84,964
Loans over 90 days past due and accruing interest	393	252	149
Non-accruals	344	155	82
Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	27,833	22,947
Loans over 90 days past due and accruing interest	109	54	19
Non-accruals	95	34	14
Card Member loans | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	51	53
Loans over 90 days past due and accruing interest	0	0	0
Non-accruals	$ 0	0	0
Card Member receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due	30 days
Financing receivables, gross	$ 60,411	57,613
Threshold period past due for write-off	180 days
Card Member receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 25,578	22,885
Loans over 90 days past due and accruing interest	0	0	0
Non-accruals	0	0	0
Card Member receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	19,286	19,629
Loans over 90 days past due and accruing interest	0	0	0
Non-accruals	0	0	0
Card Member receivables | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	15,547	15,099
Loans over 90 days past due and accruing interest	0	0	0
Non-accruals	0	0	$ 0
Current | Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	96,779	84,102
Current | Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	27,444	22,731
Current | Card Member receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	25,355	22,634
Current | Card Member receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	19,020	19,330
30-59 Days Past Due | Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	420	281
30-59 Days Past Due | Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	133	81
30-59 Days Past Due | Card Member receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	70	83
30-59 Days Past Due | Card Member receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	104	120
60-89 Days Past Due | Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	298	198
60-89 Days Past Due | Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	85	49
60-89 Days Past Due | Card Member receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	47	56
60-89 Days Past Due | Card Member receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	62	69
90+ Days Past Due | Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	614	383
90+ Days Past Due | Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	171	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	106	112
90+ Days Past Due | Card Member receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	100	110
90+ Days Past Due | Card Member receivables | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 67	$ 85