Fair Values - Not Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Card Member Receivables
Fair Values (Textuals)
Financing receivables, gross	$ 58,503	$ 59,411
Card Member Loans
Fair Values (Textuals)
Financing receivables, gross	139,203	139,674
Variable Interest Entity, Primary Beneficiary | Card Member Receivables
Fair Values (Textuals)
Financing receivables, gross	4,205	3,927
Variable Interest Entity, Primary Beneficiary | Card Member Loans
Fair Values (Textuals)
Financing receivables, gross	26,667	28,278
Carrying Value
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	53,000	41,000
Other financial assets	62,000	63,000
Financial assets carried at other than fair value
Card Member and Other loans, less reserves	143,000	143,000
Card Member loans HFS	1,000	1,000
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	160,000	155,000
Financial liabilities carried at other than fair value
Long-term debt	51,000	50,000
Fair Values (Textuals)
Long-term debt	51,000	50,000
Carrying Value | Certificates of Deposit
Financial liabilities carried at other than fair value
Financial liabilities	14,000	12,000
Corresponding Fair Value Amount
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	53,000	41,000
Other financial assets	62,000	63,000
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	160,000	155,000
Corresponding Fair Value Amount | Variable Interest Entity, Primary Beneficiary | Card Member Receivables
Fair Values (Textuals)
Financing receivables, gross	4,200	3,900
Corresponding Fair Value Amount | Level 1
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	51,000	39,000
Other financial assets	0	0
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	0	0
Corresponding Fair Value Amount | Level 2
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	2,000	2,000
Other financial assets	62,000	63,000
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	160,000	155,000
Corresponding Fair Value Amount | Level 3
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	0	0
Other financial assets	0	0
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	0	0
Portion at Other than Fair Value Measurement
Financial assets carried at other than fair value
Card Member and Other loans, less reserves	149,000	149,000
Card Member loans HFS	1,000	1,000
Financial liabilities carried at other than fair value
Long-term debt	52,000	50,000
Fair Values (Textuals)
Long-term debt	52,000	50,000
Portion at Other than Fair Value Measurement | Variable Interest Entity, Primary Beneficiary
Financial liabilities carried at other than fair value
Long-term debt	14,200	14,000
Fair Values (Textuals)
Long-term debt	14,200	14,000
Portion at Other than Fair Value Measurement | Variable Interest Entity, Primary Beneficiary | Card Member Loans
Fair Values (Textuals)
Financing receivables, gross	26,700	28,300
Portion at Other than Fair Value Measurement | Certificates of Deposit
Financial liabilities carried at other than fair value
Financial liabilities	14,000	12,000
Portion at Other than Fair Value Measurement | Level 1
Financial assets carried at other than fair value
Card Member and Other loans, less reserves	0	0
Card Member loans HFS	0	0
Financial liabilities carried at other than fair value
Long-term debt	0	0
Fair Values (Textuals)
Long-term debt	0	0
Portion at Other than Fair Value Measurement | Level 1 | Certificates of Deposit
Financial liabilities carried at other than fair value
Financial liabilities	0	0
Portion at Other than Fair Value Measurement | Level 2
Financial assets carried at other than fair value
Card Member and Other loans, less reserves	0	0
Card Member loans HFS	0	0
Financial liabilities carried at other than fair value
Long-term debt	52,000	50,000
Fair Values (Textuals)
Long-term debt	52,000	50,000
Portion at Other than Fair Value Measurement | Level 2 | Certificates of Deposit
Financial liabilities carried at other than fair value
Financial liabilities	14,000	12,000
Portion at Other than Fair Value Measurement | Level 3
Financial assets carried at other than fair value
Card Member and Other loans, less reserves	149,000	149,000
Card Member loans HFS	1,000	1,000
Financial liabilities carried at other than fair value
Long-term debt	0	0
Fair Values (Textuals)
Long-term debt	0	0
Portion at Other than Fair Value Measurement | Level 3 | Certificates of Deposit
Financial liabilities carried at other than fair value
Financial liabilities	$ 0	$ 0