Goodwill and Intangible Assets, Net - Components of Intangible Assets with Definite Lives (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Cost	$ 2,462	$ 2,436
Accumulated Amortization	(1,870)	(1,606)
Net	592	830
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Cost	659	665
Accumulated Amortization	(419)	(304)
Net	240	361
Supplier relationships
Finite-Lived Intangible Assets [Line Items]
Cost	650	655
Accumulated Amortization	(426)	(368)
Net	224	287
Technology
Finite-Lived Intangible Assets [Line Items]
Cost	544	532
Accumulated Amortization	(510)	(441)
Net	34	91
Domain names
Finite-Lived Intangible Assets [Line Items]
Cost	159	132
Accumulated Amortization	(83)	(70)
Net	76	62
Other
Finite-Lived Intangible Assets [Line Items]
Cost	450	452
Accumulated Amortization	(432)	(423)
Net	$ 18	$ 29