Acquisitions, Goodwill, and Acquired Intangible Assets - Acquired Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Intangibles, Gross	$ 5,350	$ 4,422
Accumulated Amortization	(1,240)	(1,051)
Acquired Intangibles, Net	$ 4,110	3,371
Weighted Average Life Remaining	15 years 5 months
Amortization expense for acquired intangibles	$ 475	366	$ 287
Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life	1 year
Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life	25 years
Marketing-related
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Intangibles, Gross	$ 2,542	2,486
Accumulated Amortization	(431)	(418)
Acquired Intangibles, Net	$ 2,111	2,068
Weighted Average Life Remaining	21 years 2 months
Contract-based
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Intangibles, Gross	$ 1,430	1,013
Accumulated Amortization	(224)	(213)
Acquired Intangibles, Net	$ 1,206	800
Weighted Average Life Remaining	12 years 4 months
Technology- and content-based
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Intangibles, Gross	$ 941	640
Accumulated Amortization	(377)	(252)
Acquired Intangibles, Net	$ 564	388
Weighted Average Life Remaining	4 years 7 months
Customer-related
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Intangibles, Gross	$ 437	283
Accumulated Amortization	(208)	(168)
Acquired Intangibles, Net	$ 229	$ 115
Weighted Average Life Remaining	4 years 5 months