Acquisitions, Goodwill, and Acquired Intangible Assets - Goodwill Activity (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017 USD ($)
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	$ 3,784
New acquisitions (1)	9,431
Other adjustments (2)	56
Goodwill, balance at end of period	13,271
North America
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	2,044
New acquisitions (1)	9,056
Other adjustments (2)	5
Goodwill, balance at end of period	11,105
International
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	694
New acquisitions (1)	357
Other adjustments (2)	40
Goodwill, balance at end of period	1,091
AWS
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	1,046
New acquisitions (1)	18
Other adjustments (2)	11
Goodwill, balance at end of period	$ 1,075