Loans and Card Member Receivables - Modifications Subsequently Defaulted (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	$ 74	$ 95	$ 117	$ 134
Interest Rate Reduction and Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	1	2	2	2
Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	59	75	96	108
Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	14	18	19	24
Card Member Loans | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	40	52	65	75
Card Member Loans | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	19	23	31	33
Card Member Loans | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Card Member Loans | Interest Rate Reduction and Term Extension | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Card Member Loans | Interest Rate Reduction and Term Extension | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Card Member Loans | Interest Rate Reduction and Term Extension | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Card Member Loans | Interest Rate Reduction | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	40	52	65	75
Card Member Loans | Interest Rate Reduction | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	19	23	31	33
Card Member Loans | Interest Rate Reduction | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Card Member Receivables | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	5	6	6	8
Card Member Receivables | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	9	12	13	16
Card Member Receivables | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Card Member Receivables | Interest Rate Reduction and Term Extension | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Card Member Receivables | Interest Rate Reduction and Term Extension | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Card Member Receivables | Interest Rate Reduction and Term Extension | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Card Member Receivables | Term Extension | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	5	6	6	8
Card Member Receivables | Term Extension | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	9	12	13	16
Card Member Receivables | Term Extension | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Other Loans
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	1	2	2	2
Other Loans | Interest Rate Reduction and Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	1	2	2	2
Other Loans | Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0	0	0
Other Loans | Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	$ 0	$ 0	$ 0	$ 0