Fair Values (Details 2) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	$ 33	$ 102	$ 200	$ 196
Financial assets carried at other than fair value
Card Member loans, net	634	636
Loans to affiliates and other	9,222	14,136
Financial liabilities carried at other than fair value
Long-term debt	13,448	20,447
Long-term debt to affiliates	10,053	7,523
Carrying Value [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	0	100
Other financial assets	25,200	24,900
Financial assets carried at other than fair value
Card Member loans, net	600	600
Loans to affiliates and other	9,200	14,100
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	8,200	9,000
Financial liabilities carried at other than fair value
Long-term debt	13,400	20,400
Long-term debt to affiliates	10,100	7,500
Estimate of Fair Value Measurement [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	0	100
Other financial assets	25,200	24,900
Financial assets carried at other than fair value
Card Member loans, net	600	600
Loans to affiliates and other	9,300	14,100
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	8,200	9,000
Financial liabilities carried at other than fair value
Long-term debt	13,700	20,500
Long-term debt to affiliates	10,300	7,300
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	100
Other financial assets	100	100
Financial assets carried at other than fair value
Card Member loans, net	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	25,100	24,800
Financial assets carried at other than fair value
Card Member loans, net	0	0
Loans to affiliates and other	2,600	7,400
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	8,200	9,000
Financial liabilities carried at other than fair value
Long-term debt	13,700	20,500
Long-term debt to affiliates	10,300	7,300
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, net	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
Long-term debt	0	0
Long-term debt to affiliates	$ 0	$ 0