Reserves For Losses (Details Textuals) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2016	Sep. 30, 2017	Sep. 30, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Card Member receivables reserves for losses - other		$ 3	$ (3)
Card Member loans reserves for losses - other		26	70
Allowance for Card Member Receivables and Reserves, Recoveries of Bad Debts		271	301
Allowance for Card Member Loans, Recoveries of Bad Debts		307	280
Allowance for Card Member Receivables, Recoveries of Bad Debts - TDR		2	16
Allowance for Card Member Loans, Recoveries of Bad Debts - TDR		25	24
Foreign Currency Translation Adjustments [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Card Member receivables reserves for losses - other		18	0
Card Member loans reserves for losses - other		14	(3)
Other Items [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Card Member receivables reserves for losses - other		(15)	(3)
Card Member loans reserves for losses - other		$ 12	6
CardMember loans transferred from HFS to held for investment	$ 0		265
CardMember reserves associated with loans held for investments	$ 0		$ 67