Fair Values (Details 2) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	$ 30,442	$ 25,208	$ 33,767	$ 22,762
Financial liabilities carried at other than fair value
Certificates of deposit	15,298
Long-term debt	51,945	46,990
Fair Values (Textuals) [Abstract]
Accounts receivable, less reserves	48,930	46,841
Card Member loans, net	64,651	64,042
Variable Interest Enterprise [Member]
Financial liabilities carried at other than fair value
Long-term debt	16,002	15,113
Carrying Value [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	30,000	25,000
Other financial assets	52,000	51,000
Financial assets carried at other than fair value
Loans, net	67,000	65,000
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	67,000	67,000
Financial liabilities carried at other than fair value
Certificates of deposit	15,000	12,000
Long-term debt	52,000	47,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	30,000	25,000
Other financial assets	52,000	51,000
Financial assets carried at other than fair value
Loans, net	67,000	66,000
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	67,000	67,000
Financial liabilities carried at other than fair value
Certificates of deposit	15,000	12,000
Long-term debt	53,000	48,000
Estimate of Fair Value, Fair Value Disclosure [Member] | Variable Interest Enterprise [Member]
Financial liabilities carried at other than fair value
Long-term debt	16,100	15,200
Fair Values (Textuals) [Abstract]
Accounts receivable, less reserves	7,900	8,800
Card Member loans, net	24,400	26,000
Level 1 [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	28,000	22,000
Other financial assets	0	0
Financial assets carried at other than fair value
Loans, net	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
Certificates of deposit	0	0
Long-term debt	0	0
Level 2 [Member]
Financial assets for which carrying values equal or approximate fair value
Cash and cash equivalents	2,000	3,000
Other financial assets	52,000	51,000
Financial assets carried at other than fair value
Loans, net	0	0
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	67,000	67,000
Financial liabilities carried at other than fair value
Certificates of deposit	15,000	12,000
Long-term debt	53,000	48,000
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
Loans, net	67,000	66,000
Financial Liabilities:
Financial liabilities for which carrying values equal or approximate fair value	0	0
Financial liabilities carried at other than fair value
Certificates of deposit	0	0
Long-term debt	$ 0	$ 0