Fair Value (Details 1) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	$ 556	$ 471
Loans to affiliates and other	14,527	10,659	$ 14,262
Financial liabilities carried at other than fair value [Abstract]
Total Long-term Debt	24,153	20,512
Long Term Debt with Affiliates	270	0	$ 0
Carrying Value [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	200	1,200
Other financial assets	20,600	19,300
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	600	500
Loans to affiliates and other	14,500	10,700
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	8,600	9,100
Financial liabilities carried at other than fair value [Abstract]
Total Long-term Debt	24,200	20,500
Long Term Debt with Affiliates	300	0
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	200	1,200
Other financial assets	20,600	19,300
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	600	500
Loans to affiliates and other	14,400	10,700
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	8,600	9,100
Financial liabilities carried at other than fair value [Abstract]
Total Long-term Debt	24,500	20,700
Long Term Debt with Affiliates	300	0
Level 1 [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	200	200
Other financial assets	100	0
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	0	1,000
Other financial assets	20,500	19,300
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	0	0
Loans to affiliates and other	10,000	7,900
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	8,600	9,100
Financial liabilities carried at other than fair value [Abstract]
Total Long-term Debt	24,500	20,700
Long Term Debt with Affiliates	300	0
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 [Abstract]
Card Member loans, less reserves	600	500
Loans to affiliates and other	4,400	2,800
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