Fair Values (Details 2) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Financial assets carried at other than fair value
Loans to affiliates and other	$ 10,859	$ 10,890
Financial liabilities carried at other than fair value
Long-term debt	6,982	7,037
Long-term debt to affiliates	849	822
Card Member Loans
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	435	480
Carrying Value
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	700	600
Other financial assets	11,600	12,100
Financial assets carried at other than fair value
Loans to affiliates and other	10,900	10,900
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	12,100	12,600
Financial liabilities carried at other than fair value
Long-term debt	7,000	7,000
Long-term debt to affiliates	800	800
Carrying Value | Card Member Loans
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	400	500
Corresponding Fair Value Amount
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	700	600
Other financial assets	11,600	12,100
Financial assets carried at other than fair value
Loans to affiliates and other	11,100	11,100
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	12,100	12,600
Financial liabilities carried at other than fair value
Long-term debt	7,300	7,400
Long-term debt to affiliates	900	800
Corresponding Fair Value Amount | Card Member Loans
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	500	500
Corresponding Fair Value Amount | Level 1
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	700	600
Other financial assets	0	0
Financial assets carried at other than fair value
Loans to affiliates and other	0	0
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	0	0
Financial liabilities carried at other than fair value
Long-term debt	0	0
Long-term debt to affiliates	0	0
Corresponding Fair Value Amount | Level 1 | Card Member Loans
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	0	0
Corresponding Fair Value Amount | Level 2
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	0	0
Other financial assets	11,600	12,100
Financial assets carried at other than fair value
Loans to affiliates and other	5,500	5,000
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	12,100	12,600
Financial liabilities carried at other than fair value
Long-term debt	7,300	7,400
Long-term debt to affiliates	900	800
Corresponding Fair Value Amount | Level 2 | Card Member Loans
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	0	0
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 assets carried at other than fair value
Loans to affiliates and other	5,600	6,100
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	0	0
Financial liabilities carried at other than fair value
Long-term debt	0	0
Long-term debt to affiliates	0	0
Corresponding Fair Value Amount | Level 3 | Card Member Loans
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	$ 500	$ 500