Fair Values (Details 2) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	$ 35	$ 33	$ 65	$ 102
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	588	687
Loans to affiliates and other	13,959	10,345
Financial liabilities carried at other than fair value
Long-term debt	11,074	13,469
Long-term debt to affiliates	981	9,292
Carrying Value [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	0	0
Other financial assets	11,600	26,300
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	600	700
Loans to affiliates and other	14,000	10,300
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	11,700	11,200
Financial liabilities carried at other than fair value
Long-term debt	11,100	13,500
Long-term debt to affiliates	1,000	9,300
Estimate of Fair Value Measurement [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	0	0
Other financial assets	11,500	26,300
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	600	700
Loans to affiliates and other	13,900	10,400
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	11,700	11,200
Financial liabilities carried at other than fair value
Long-term debt	11,200	13,700
Long-term debt to affiliates	900	9,400
Estimate of Fair Value Measurement [Member] | Level 1 [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	0	0
Other financial assets	100	100
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	0	0
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
Estimate of Fair Value Measurement [Member] | Level 2 [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	0	0
Other financial assets	11,400	26,200
Financial assets carried at other than fair value
Card Member loans, less reserves for credit losses	0	0
Loans to affiliates and other	8,100	2,800
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	11,700	11,200
Financial liabilities carried at other than fair value
Long-term debt	11,200	13,700
Long-term debt to affiliates	900	9,400
Estimate of Fair Value Measurement [Member] | Level 3 [Member]
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
Card Member loans, less reserves for credit losses	600	700
Loans to affiliates and other	5,800	7,600
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