Loans and Card Member Receivables - Aging (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Card Member Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due	30 days
Financing receivables, gross	$ 142,275	$ 139,674
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	$ 109,160	107,646
Loans over 90 days past due and accruing interest	425	435
Non-accruals	423	464
Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	33,072	31,991
Loans over 90 days past due and accruing interest	139	132
Non-accruals	150	135
Card Member Loans | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	43	37
Loans over 90 days past due and 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	$ 59,598	59,411
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	$ 24,598	25,431
Loans over 90 days past due and accruing interest	0	0
Non-accruals	0	0
Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	18,982	18,619
Loans over 90 days past due and accruing interest	0	0
Non-accruals	0	0
Card Member Receivables | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	16,018	15,361
Loans over 90 days past due and accruing interest	0	0
Non-accruals	0	0
Current | Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	107,714	106,155
Current | Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	32,563	31,510
Current | Card Member Receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	24,407	25,255
Current | Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	18,765	18,400
30 to 59 Days Past Due | Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	432	437
30 to 59 Days Past Due | Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	156	151
30 to 59 Days Past Due | Card Member Receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	65	58
30 to 59 Days Past Due | Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	72	77
60 to 89 Days Past Due | Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	326	329
60 to 89 Days Past Due | Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	114	107
60 to 89 Days Past Due | Card Member Receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	41	39
60 to 89 Days Past Due | Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	48	54
90+ Days Past Due | Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	688	725
90+ Days Past Due | Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	239	223
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	85	79
90+ Days Past Due | Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	97	88
90+ Days Past Due | Card Member Receivables | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 65	$ 65