Loans and Card Member Receivables - Performance (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances		$ 1,733
Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	$ 2,096
30-89 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	176
90+ Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	48
Card Member Loans | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances		781
Card Member Loans | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances		267
Card Member Loans | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances		0
Card Member Loans | Current | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	1,020
Card Member Loans | Current | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	366
Card Member Loans | Current | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	0
Card Member Loans | 30-89 Days Past Due | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	73
Card Member Loans | 30-89 Days Past Due | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	34
Card Member Loans | 30-89 Days Past Due | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	0
Card Member Loans | 90+ Days Past Due | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	20
Card Member Loans | 90+ Days Past Due | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	11
Card Member Loans | 90+ Days Past Due | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	0
Card Member Receivables | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances		257
Card Member Receivables | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances		403
Card Member Receivables | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances		6
Card Member Receivables | Current | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	257
Card Member Receivables | Current | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	402
Card Member Receivables | Current | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	9
Card Member Receivables | 30-89 Days Past Due | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	20
Card Member Receivables | 30-89 Days Past Due | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	43
Card Member Receivables | 30-89 Days Past Due | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	2
Card Member Receivables | 90+ Days Past Due | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	5
Card Member Receivables | 90+ Days Past Due | Small Business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	10
Card Member Receivables | 90+ Days Past Due | Corporate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	1
Other Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances		$ 19
Other Loans | Current
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	42
Other Loans | 30-89 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	4
Other Loans | 90+ Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Account Balances	$ 1