Property and Equipment, Net - Components of Property and Equipment, Net (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 3,898	$ 3,266
Less: accumulated depreciation	(2,552)	(2,056)
Projects in progress	531	365
Property and equipment, net	1,877	1,575
Capitalized software development
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	2,643	2,111
Computer equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	597	658
Furniture and other equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	94	85
Buildings and leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	435	283
Land
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 129	$ 129

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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