Commitments and Contingencies (Details Textuals) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments And Contingencies (Textuals) [Abstract]
Contingent obligations with co-brand partners	$ 5,000
Amount of rentals subject to subleasing arrangements	14
Future minimum payments on capital leases due, in 2019	4
Future minimum payments on capital leases due, in 2020	4
Future minimum payments on capital leases due, in 2021	1
Future minimum payments on capital leases due, in 2022	1
Future minimum payments on capital leases due, in 2023	2
Future minimum payments on capital leases due, thereafter	8
Total rental expense	142	$ 151	$ 169
Loss Contingencies [Line Items]
Loss Contingency Estimate Of Possible Loss	400
Minimum [Member]
Loss Contingencies [Line Items]
Loss Contingency Estimate Of Possible Loss	$ 0