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, 2019		Dec. 31, 2018		Dec. 31, 2020
Business Acquisition [Line Items]
Goodwill		$ 840		$ 756		$ 862
Series of Individually Immaterial Business Acquisition
Business Acquisition [Line Items]
Goodwill		88	[1]	11	[2]
Intangible assets		26	[3]	14	[4]
Net tangible assets (liabilities)	[5]	(5)
Total purchase price consideration	[6]	$ 109		$ 23
Weighted average life of preliminary identifiable definite-lived intangible assets acquired		6 years		8 years
Cash acquired from acquisition		$ 2
Assets acquired, accounts receivable		3
Assets acquired, prepaid expenses and other current assets		2
Liabilities assumed		10
Deferred tax liabilities, net				$ (2)
Series of Individually Immaterial Business Acquisition | Trade Names
Business Acquisition [Line Items]
Intangible assets		$ 2
Weighted average life of preliminary identifiable definite-lived intangible assets acquired		2 years
Series of Individually Immaterial Business Acquisition | Customer Lists and Supplier Relationships
Business Acquisition [Line Items]
Intangible assets		$ 10		$ 6
Weighted average life of preliminary identifiable definite-lived intangible assets acquired		8 years		10 years
Series of Individually Immaterial Business Acquisition | Subscriber Relationships
Business Acquisition [Line Items]
Intangible assets		$ 6
Weighted average life of preliminary identifiable definite-lived intangible assets acquired		3 years
Series of Individually Immaterial Business Acquisition | Developed Technology and Other
Business Acquisition [Line Items]
Intangible assets		$ 8		$ 8
Weighted average life of preliminary identifiable definite-lived intangible assets acquired		6 years		6 years
Series of Individually Immaterial Business Acquisition | Not Deductible for Tax Purposes
Business Acquisition [Line Items]
Goodwill not deductible for tax purpose		$ 53

[1] Goodwill of $53 million is not deductible for tax purposes.  

[2] Goodwill is not deductible for tax purposes.

[3] Identifiable definite-lived intangible assets acquired were comprised of trade names of $2 million with a weighted average life of 2 years, customer lists and supplier relationships of $10 million with a weighted average life of 8 years, subscriber relationships of $6 million with a weighted average life of approximately 3 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 these businesses was 6 years, and will be amortized on a straight-line basis over their estimated useful lives from acquisition date.

[4] Identifiable definite-lived intangible assets acquired 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 was 8 years, and will be amortized on a straight-line basis over the estimated useful lives from acquisition date.

[5] Primarily includes cash acquired of $2 million, accounts receivable of $3 million, prepaid expenses and other current assets of $2 million and liabilities assumed of $10 million, including accounts payable, accrued expenses and other current liabilities, and deferred revenue, which reflect their respective fair values at acquisition.

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