Fair Value (Details 1) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	$ 492	$ 471
Loans to affiliates and other	12,367	10,659
Financial liabilities carried at other than fair value [Abstract]
Long-term Debt	24,239	20,512
Carrying Value [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	1,300	1,200
Other financial assets	22,600	19,300
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	500	500
Loans to affiliates and other	12,400	10,700
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	9,800	9,100
Financial liabilities carried at other than fair value [Abstract]
Long-term Debt	24,200	20,500
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	1,300	1,200
Other financial assets	22,600	19,300
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	500	500
Loans to affiliates and other	12,200	10,700
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	9,800	9,100
Financial liabilities carried at other than fair value [Abstract]
Long-term Debt	24,600	20,700
Level 1 [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	200	200
Other financial assets	0	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]
Long-term Debt	0	0
Level 2 [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	1,100	1,000
Other financial assets	22,600	19,300
Financial assets carried at other than fair value [Abstract]
Card Member loans, less reserves	0	0
Loans to affiliates and other	9,100	7,900
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	9,800	9,100
Financial liabilities carried at other than fair value [Abstract]
Long-term Debt	24,600	20,700
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	500	500
Loans to affiliates and other	3,100	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]
Long-term Debt	$ 0	$ 0