Loans and Card Member Receivables - Aging (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans over 90 days past due and accruing interest			$ 309
Non-accruals			$ 191
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	$ 139,674	$ 125,995
Threshold period past due for write-off	180 days
Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 107,646	98,111
Loans over 90 days past due and accruing interest	435	393	$ 252
Non-accruals	464	344	155
Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	31,991	27,833
Loans over 90 days past due and accruing interest	132	109	54
Non-accruals	135	95	34
Card Member loans | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	37	51
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	$ 59,411	60,411
Threshold period past due for write-off	180 days
Card Member receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 25,431	25,578
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	18,619	19,286
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	15,361	15,547
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	106,155	96,779
Current | Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	31,510	27,444
Current | Card Member receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	25,255	25,355
Current | Card Member receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	18,400	19,020
30-59 Days Past Due | Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	437	420
30-59 Days Past Due | Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	151	133
30-59 Days Past Due | Card Member receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	58	70
30-59 Days Past Due | Card Member receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	77	104
60-89 Days Past Due | Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	329	298
60-89 Days Past Due | Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	107	85
60-89 Days Past Due | Card Member receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	39	47
60-89 Days Past Due | Card Member receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	54	62
90+ Days Past Due | Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	725	614
90+ Days Past Due | Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	223	171
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	79	106
90+ Days Past Due | Card Member receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	88	100
90+ Days Past Due | Card Member receivables | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 65	$ 67