Loans and Card Member Receivables - Summary (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022
Card Member Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 126,619	$ 125,995
Less: Reserves for credit losses	5,271	5,118	$ 4,053	$ 3,747
Financing receivables, net	121,348	120,877
Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	96,789	98,111
Card Member Loans | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	29,733	27,833
Card Member Loans | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	97	51
Other Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: Reserves for credit losses	136	126
Financing receivables, net	7,465	6,960
Card Member Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	59,775	60,411
Less: Reserves for credit losses	151	174	$ 223	$ 229
Financing receivables, net	59,624	60,237
Card Member Receivables | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	24,015	25,578
Card Member Receivables | Small Business
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	19,084	19,286
Card Member Receivables | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	16,676	15,547
Variable Interest Entity, Primary Beneficiary | Card Member Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	27,325	28,590
Variable Interest Entity, Primary Beneficiary | Card Member Loans | Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	27,300	28,600
Variable Interest Entity, Primary Beneficiary | Card Member Receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	4,851	4,587
Variable Interest Entity, Primary Beneficiary | Card Member Receivables | Corporate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables, gross	$ 4,900	$ 4,600