Acquisitions and Other Investments - Summary of Aggregate Purchase Price Consideration Allocated to Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2016		Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill		$ 756		$ 736		$ 758
Series of Individually Immaterial Business Acquisition
Business Acquisition [Line Items]
Goodwill	[1]	11		17
Intangible assets		14	[2]	25	[3]
Net tangible assets (liabilities)	[4]			(8)
Deferred tax liabilities, net		(2)
Total purchase price consideration	[5]	$ 23		$ 34
Weighted average life of identifiable definite-lived intangible assets acquired		8 years		6 years
Cash acquired from acquisition				$ 4
Assets acquired, accounts receivable				2
Series of Individually Immaterial Business Acquisition | Accrued Expenses
Business Acquisition [Line Items]
Liabilities assumed				3
Series of Individually Immaterial Business Acquisition | Deferred Merchant Payables
Business Acquisition [Line Items]
Liabilities assumed				10
Series of Individually Immaterial Business Acquisition | Trade Names
Business Acquisition [Line Items]
Intangible assets				$ 4
Weighted average life of identifiable definite-lived intangible assets acquired				10 years
Series of Individually Immaterial Business Acquisition | Customer Lists and Supplier Relationships
Business Acquisition [Line Items]
Intangible assets		$ 6		$ 4
Weighted average life of identifiable definite-lived intangible assets acquired		10 years		6 years
Series of Individually Immaterial Business Acquisition | Subscriber Relationships
Business Acquisition [Line Items]
Intangible assets				$ 5
Weighted average life of identifiable definite-lived intangible assets acquired				7 years
Series of Individually Immaterial Business Acquisition | Developed Technology and Other
Business Acquisition [Line Items]
Intangible assets		$ 8		$ 12
Weighted average life of identifiable definite-lived intangible assets acquired		6 years		5 years

[1] Goodwill is not deductible for tax purposes.

[2] Identifiable definite-lived intangible assets acquired during 2018 were comprised of supplier relationships of $6 million with a weighted average life of 10 years and technology and other of $8 million with a weighted average life of approximately 6 years. The overall weighted-average life of the identifiable definite-lived intangible assets acquired in the purchase of this business during 2018 was 8 years, and will be amortized on a straight-line basis over the estimated useful lives from acquisition date.

[3] Identifiable definite-lived intangible assets acquired during 2016 were comprised of trade names of $4 million with a weighted average life of 10 years, customer lists and supplier relationships of $4 million with a weighted average life of 6 years, subscriber relationships of $5 million with a weighted average life of approximately 7 years, and technology and other of $12 million with a weighted average life of approximately 5 years. The overall weighted-average life of the identifiable definite-lived intangible assets acquired in the purchase of these businesses during 2016 was 6 years, and will be amortized on a straight-line basis over their estimated useful lives from acquisition date.

[4] Primarily includes cash acquired of $4 million, accounts receivable of $2 million, and liabilities assumed, including accrued expenses and deferred merchant payables of $3 million and $10 million, respectively, which reflect their respective fair values at acquisition.

[5] Subject to adjustment based on indemnification obligations for general representations and warranties of certain acquired company stockholders.