Loans and Card Member Receivables - Modifications that Subsequently Defaulted (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	$ 157	$ 97	$ 120
Interest Rate Reduction and Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	2	1
Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	128	73
Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	27	23
Card Member loans
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default			81
Card Member loans | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	88	53
Card Member loans | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	40	20
Card Member loans | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	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
Card Member loans | Interest Rate Reduction and Term Extension | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	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
Card Member loans | Interest Rate Reduction | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	88	53
Card Member loans | Interest Rate Reduction | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	40	20
Card Member loans | Interest Rate Reduction | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0
Card Member receivables
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default			38
Card Member receivables | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	10	9
Card Member receivables | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	17	14
Card Member receivables | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	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
Card Member receivables | Interest Rate Reduction and Term Extension | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	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
Card Member receivables | Term Extension | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	10	9
Card Member receivables | Term Extension | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	17	14
Card Member receivables | Term Extension | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0
Other Loans
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	2	1	$ 1
Other Loans | Interest Rate Reduction and Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	2	1
Other Loans | Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0
Other Loans | Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	$ 0	$ 0