Acquisitions, Goodwill, and Acquired Intangible Assets - Additional Informaiton (Detail) - USD ($) $ in Millions			9 Months Ended
		Oct. 19, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Business Acquisition [Line Items]
Cash paid, net of cash acquired			$ 340
Indemnification holdback			53
Business Combination, Consideration Transferred			393	$ 862
Goodwill			3,529		$ 3,319
Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Goodwill			239	707
Intangible assets	[1]		186	$ 230
Property and equipment			1
Deferred tax assets			34
Other assets acquired			23
Deferred tax liabilities			(65)
Other liabilities assumed			(25)
Business acquisition, allocation			$ 393
Acquired intangible assets weighted-average amortization period			5 years
Contract-based | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Intangible assets	[1]		$ 1
Technology-based | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Intangible assets	[1]		181
Customer-related | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Intangible assets	[1]		$ 4
Minimum | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Acquired intangible assets estimated useful lives			1 year
Maximum | Series of Individually Immaterial Business Acquisitions [Member]
Business Acquisition [Line Items]
Acquired intangible assets estimated useful lives			6 years
Subsequent Event [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 296

[1] Acquired intangible assets have estimated useful lives of between one and six years, with a weighted-average amortization period of five years.