Fair Value 1 (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents per Consolidated Balance Sheets	$ 65	$ 102	$ 191	$ 196
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	637	636
Loans to affiliates and other	14,235	14,136
Financial liabilities carried at other than fair value [Abstract]
Total Long-term Debt	18,259	20,447
Long Term Debt with Affiliates	10,581	7,523
Carrying Value [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents per Consolidated Balance Sheets	100	100
Other financial assets	26,000	24,900
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	600	600
Loans to affiliates and other	14,200	14,100
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	8,900	9,000
Financial liabilities carried at other than fair value [Abstract]
Total Long-term Debt	18,300	20,400
Long Term Debt with Affiliates	10,600	7,500
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents per Consolidated Balance Sheets	100	100
Other financial assets	26,000	24,900
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	600	600
Loans to affiliates and other	14,300	14,100
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	8,900	9,000
Financial liabilities carried at other than fair value [Abstract]
Total Long-term Debt	18,500	20,500
Long Term Debt with Affiliates	10,600	7,300
Level 1 [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents per Consolidated Balance Sheets	100	100
Other financial assets	100	100
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	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 [Abstract]
Total Long-term Debt	0	0
Long Term Debt with Affiliates	0	0
Level 2 [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents per Consolidated Balance Sheets	0	0
Other financial assets	25,900	24,800
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	0	0
Loans to affiliates and other	7,600	7,400
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	8,900	9,000
Financial liabilities carried at other than fair value [Abstract]
Total Long-term Debt	18,500	20,500
Long Term Debt with Affiliates	10,600	7,300
Level 3 [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents per Consolidated Balance Sheets	0	0
Other financial assets	0	0
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	600	600
Loans to affiliates and other	6,700	6,700
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	0	0
Financial liabilities carried at other than fair value [Abstract]
Total Long-term Debt	0	0
Long Term Debt with Affiliates	$ 0	$ 0