Acquisitions and Dispositions - Summary of Aggregate Purchase Price Consideration Allocated to Fair Value of Assets Acquired and Liabilities Assumed (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Business Acquisition [Line Items]
Cash acquired from acquisition					$ 62
Goodwill expected to be deductible for tax purposes					5
Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Intangible assets	$ 25	[1]	$ 12	[2]	$ 194	[3]
Weighted average life of identifiable definite-lived intangible assets acquired	6 years		6 years		7 years
Cash acquired from acquisition	$ 4				$ 7
Assets acquired, accounts receivable	2				25
Liabilities assumed, deferred revenue					5
Series of Individually Immaterial Business Acquisitions | Accrued Expenses
Business Acquisition [Line Items]
Liabilities assumed	3				15
Series of Individually Immaterial Business Acquisitions | Deferred Merchant Payables
Business Acquisition [Line Items]
Liabilities assumed	10				76
Series of Individually Immaterial Business Acquisitions | Trade Names
Business Acquisition [Line Items]
Intangible assets	$ 4		$ 2		$ 44
Weighted average life of identifiable definite-lived intangible assets acquired	10 years		10 years		10 years
Series of Individually Immaterial Business Acquisitions | Customer Lists and Supplier Relationships
Business Acquisition [Line Items]
Intangible assets	$ 4		$ 7		$ 82
Weighted average life of identifiable definite-lived intangible assets acquired	6 years		6 years		7 years
Series of Individually Immaterial Business Acquisitions | Subscriber Relationships
Business Acquisition [Line Items]
Intangible assets	$ 5				$ 25
Weighted average life of identifiable definite-lived intangible assets acquired	7 years				6 years
Series of Individually Immaterial Business Acquisitions | Developed Technology and Other
Business Acquisition [Line Items]
Intangible assets	$ 12		$ 3		$ 43
Weighted average life of identifiable definite-lived intangible assets acquired	5 years		2 years		5 years

[1] 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.

[2] Identifiable definite-lived intangible assets acquired during 2015 were comprised of trade names of $2 million with a weighted average life of approximately 10 years, customer lists and supplier relationships of $7 million with a weighted average life of approximately 6 years and technology and other of $3 million with a weighted average life of approximately 2 years. The overall weighted-average life of the identifiable definite-lived intangible assets acquired in the purchase of these businesses during 2015 was 6 years, and will be amortized on a straight-line basis over their estimated useful lives from acquisition date.

[3] Identifiable definite-lived intangible assets acquired during 2014 were comprised of trade names of $44 million with a weighted average life of 10 years, customer lists and supplier relationships of $82 million with an approximate weighted average life of 7 years, subscriber relationships of $25 million with a weighted average life of 6 years and developed technology and other of $43 million with an approximate weighted average life of 5 years. The overall weighted-average life of the identifiable definite-lived intangible assets acquired in the purchase of the companies during 2014 was approximately 7 years, and will be amortized on a straight-line basis over their estimated useful lives from acquisition date.