Loans and Card Member Receivables - Card Member and other Loans (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Card Member loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 139,674	$ 125,995
Financing receivables, reserves for credit losses	5,679	5,118	$ 3,747	$ 3,305
Financing receivables, net	133,995	120,877
Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	107,646	98,111
Card Member loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	31,991	27,833
Card Member loans | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	37	51
Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, reserves for credit losses	194	126
Financing receivables, net	9,038	6,960
Variable Interest Entity, Primary Beneficiary | Card Member loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	28,278	28,590
Variable Interest Entity, Primary Beneficiary | Card Member loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 28,300	$ 28,600