Loans and Accounts Receivable (Details 6) Account in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) Account M bp	Dec. 31, 2017 USD ($) Account M bp	Dec. 31, 2016 USD ($) Account M bp
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands) | Account	57	39	40
Aggregated Outstanding Balance | $	$ 487	$ 307	$ 343
Card Member Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands) | Account	51	33	31
Aggregated Outstanding Balance | $	$ 377	$ 224	$ 220
Average Interest Rate Reduction By Class Of Financial Instrument | bp	12	10	9
Card Member Receivables [Member]
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands) | Account	6	6	9
Aggregated Outstanding Balance | $	$ 110	$ 83	$ 123
Average Payment Term Extension | M	28	28	18