Acquisitions, Goodwill, and Acquired Intangible Assets - Goodwill Activity (Details) $ in Millions	6 Months Ended
	Jun. 30, 2017 USD ($)
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	$ 3,784
New acquisitions	425
Other adjustments	45
Goodwill, balance at end of period	4,254
North America
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	2,044
New acquisitions	80
Other adjustments	4
Goodwill, balance at end of period	2,128
International
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	694
New acquisitions	327
Other adjustments	28
Goodwill, balance at end of period	1,049
AWS
Goodwill [Roll Forward]
Goodwill, balance at beginning of period	1,046
New acquisitions	18
Other adjustments	13
Goodwill, balance at end of period	$ 1,077