Loans and Accounts Receivable (Details 6) Account in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) Account M bp	Dec. 31, 2016 USD ($) Account M bp	Dec. 31, 2015 USD ($) Account M bp
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands) | Account	39	40	52
Aggregated Outstanding Balance	$ 307	$ 343	$ 432
Accounts Receivable and Loans Textuals [Abstract]
Difference between pre- and post-modification outstanding balances	$ 0	$ 0	$ 0
U S Consumer Services [Member]
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands) | Account	39	40
Aggregated Outstanding Balance	$ 307	$ 343
Card Member Loans [Member]
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands) | Account	33	31	40
Aggregated Outstanding Balance	$ 224	$ 220	$ 285
Card Member Loans [Member] | U S Consumer Services [Member]
Financing Receivable, Modifications [Line Items]
Average Interest Rate Reduction By Class Of Financial Instrument | bp	10	9	9
Card Member Receivables [Member]
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands) | Account	6	9	12
Aggregated Outstanding Balance	$ 83	$ 123	$ 147
Card Member Receivables [Member] | U S Consumer Services [Member]
Financing Receivable, Modifications [Line Items]
Number of Accounts (in thousands) | Account	6	9
Aggregated Outstanding Balance	$ 83	$ 123
Average Payment Term Extension | M	28	18	12