Loans and Card Member Receivables - Modifications Subsequently Defaulted (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	$ 84	$ 79
Interest Rate Reduction and Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	1	1
Interest Rate Reduction
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	67	58
Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	16	20
Card Member Loans | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	45	40
Card Member Loans | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	22	18
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	45	40
Card Member Loans | Interest Rate Reduction | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	22	18
Card Member Loans | Interest Rate Reduction | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	0
Card Member Receivables | Consumer
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	5	6
Card Member Receivables | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	11	13
Card Member Receivables | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	1
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	5	6
Card Member Receivables | Term Extension | Small Business
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	11	13
Card Member Receivables | Term Extension | Corporate
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	0	1
Other Loans
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	1	1
Other Loans | Interest Rate Reduction and Term Extension
Financing Receivable, Modifications [Line Items]
Account balance, modified and subsequent default	1	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