Property and Equipment, Net - Components of Property and Equipment (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 371	$ 335
Less: accumulated depreciation		(111)	(88)
Total		260	247
Capitalized Software and Website Development
Property Plant And Equipment [Line Items]
Property and equipment, gross		153	127
Total		86	71
Building
Property Plant And Equipment [Line Items]
Property and equipment, gross	[1]	123	123
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross		39	32
Computer Equipment and Purchased Software
Property Plant And Equipment [Line Items]
Property and equipment, gross		37	36
Furniture, Office Equipment and Other
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 19	$ 17

[1] The Company is deemed for accounting purposes to be the owner of its corporate headquarters building under GAAP, and depreciates the asset over its estimated useful life of 40 years on a straight-line basis. Refer to “Note 13 – Commitments and Contingencies,” for additional information on our corporate headquarters lease.