Loans and Card Member Receivables - Modifications Subsequently Defaulted (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	$ 79	$ 0
Interest Rate Reduction and Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	1
Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	58
Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	20
Card Member Loans | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	40
Card Member Loans | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	18
Card Member Loans | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	0
Card Member Loans | Interest Rate Reduction and Term Extension | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	0
Card Member Loans | Interest Rate Reduction and Term Extension | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	0
Card Member Loans | Interest Rate Reduction and Term Extension | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	0
Card Member Loans | Interest Rate Reduction | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	40
Card Member Loans | Interest Rate Reduction | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	18
Card Member Loans | Interest Rate Reduction | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	0
Card Member Receivables | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	6
Card Member Receivables | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	13
Card Member Receivables | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	1
Card Member Receivables | Interest Rate Reduction and Term Extension | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	0
Card Member Receivables | Interest Rate Reduction and Term Extension | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	0
Card Member Receivables | Interest Rate Reduction and Term Extension | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	0
Card Member Receivables | Term Extension | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	6
Card Member Receivables | Term Extension | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	13
Card Member Receivables | Term Extension | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	1
Other Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	1
Other Loans | Interest Rate Reduction and Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	1
Other Loans | Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	0
Other Loans | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account balance	$ 0