Reserves For Losses (Details Textuals) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Card Member receivables reserves for losses - other	$ 1	$ 5
Card Member loans reserves for losses - other	10	11
Allowance for Card Member Receivables and Reserves, Recoveries of Bad Debts	88	93
Allowance for Card Member Loans, Recoveries of Bad Debts	106	100
Allowance for Card Member Receivables, Recoveries of Bad Debts - TDR	(2)	6
Allowance for Card Member Loans, Recoveries of Bad Debts - TDR	7	12
Foreign Currency Translation Adjustments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Card Member receivables reserves for losses - other	10	9
Card Member loans reserves for losses - other	6	7
Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Card Member receivables reserves for losses - other	(9)	(4)
Card Member loans reserves for losses - other	$ 4	$ 4