Loans and Accounts Receivable (Details 6) pure in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) M bp	Jun. 30, 2017 USD ($) M bp	Jun. 30, 2018 USD ($) M bp	Jun. 30, 2017 USD ($) M bp
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands)	13	8	25	18
Aggregated Outstanding Balance	$ 113	$ 64	$ 223	$ 149
Card Member Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands)	12	7	23	15
Aggregated Outstanding Balance	$ 88	$ 46	$ 169	$ 103
Average Interest Rate Reduction By Class Of Financial Instrument | bp	12	10	12	11
Card Member Receivables [Member]
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands)	1	1	2	3
Aggregated Outstanding Balance	$ 25	$ 18	$ 54	$ 46
Average payment term extension | M	28	32	28	26