Acquisitions, Goodwill, and Acquired Intangible Assets Allocation of Aggregate Purchase Price of Acquisitions (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allocation
Goodwill		$ 3,784	$ 3,759	$ 3,319
Acquired intangibles weighted average amortization period	[1]	4 years 4 months
Minimum
Allocation
Intangible assets, estimated useful life		1 year
Maximum
Allocation
Intangible assets, estimated useful life		20 years
Marketing-related
Allocation
Acquired intangibles weighted average amortization period		4 years 7 months
Contract-based
Allocation
Acquired intangibles weighted average amortization period		4 years 4 months
Technology-based
Allocation
Acquired intangibles weighted average amortization period		4 years 7 months
Customer-related
Allocation
Acquired intangibles weighted average amortization period		2 years 8 months
2014 Acquisitions
Purchase Price
Aggregate purchase price				20
Series of Individually Immaterial Business Acquisitions
Purchase Price
Cash paid, net of cash acquired		$ 81	599	813
Stock options and restricted stock assumed		0	5	44
Indemnification holdback		22	86	5
Aggregate purchase price		103	690	862
Allocation
Goodwill		60	482	707
Intangible assets		57	230	230
Property and equipment		3	4	16
Deferred tax assets		17	55	64
Other assets acquired		10	53	34
Deferred tax liabilities		(18)	(85)	(88)
Other liabilities assumed		(26)	(49)	(101)
Business acquisition, allocation		$ 103	$ 690	$ 862
Acquired intangibles weighted average amortization period		5 years	5 years	5 years
Series of Individually Immaterial Business Acquisitions | Minimum
Allocation
Intangible assets, estimated useful life		1 year	1 year	1 year
Series of Individually Immaterial Business Acquisitions | Maximum
Allocation
Intangible assets, estimated useful life		7 years	6 years	5 years
Series of Individually Immaterial Business Acquisitions | Marketing-related
Allocation
Intangible assets		$ 2	$ 3	$ 23
Series of Individually Immaterial Business Acquisitions | Contract-based
Allocation
Intangible assets		1	1	1
Series of Individually Immaterial Business Acquisitions | Technology-based
Allocation
Intangible assets		53	208	33
Series of Individually Immaterial Business Acquisitions | Customer-related
Allocation
Intangible assets		$ 1	$ 18	$ 173

[1] Intangible assets have estimated useful lives of between one and twenty years.