Reserves For Losses (Details Textuals) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Card Member receivables net write-offs	$ (661)	$ (548)
Allowance for Card Member Receivables, Recoveries of Bad Debts	266	271
Allowance for Card Member Loans, Recoveries of Bad Debts	330	307
Allowance for Card Member Receivables, Recoveries of Bad Debts - TDR	1	(2)
Allowance for Card Member Loans, Recoveries of Bad Debts - TDR	(21)	(25)
Other	9	26
Other	(17)	3
Foreign Currency Translation Adjustments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other	(4)	14
Other	0	18
Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other	13	12
Other	$ (17)	$ (15)