Loans and Accounts Receivable (Details 7) pure in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands)	9	10	11
Aggregated Outstanding Balance Upon Payment Default	$ 46	$ 45	$ 57
Card Member Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands)	6	7	8
Aggregated Outstanding Balance Upon Payment Default	$ 39	$ 41	$ 52
Card Member Receivables [Member]
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands)	3	3	3
Aggregated Outstanding Balance Upon Payment Default	$ 7	$ 4	$ 5