Acquisitions - Other (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Promissory note payable issued in connection with an acquisition	$ 198	$ 0	$ 0
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	18,026	$ 17,981	$ 839
Series of Individually Immaterial Business Acquisitions
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Land acquired	379
Other net tangible assets acquired	12
Deferred tax assets, net	17
Net assets acquired	443
Goodwill	45
Total fair value consideration	488
Series of Individually Immaterial Business Acquisitions | Acquired technology
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Finite-lived intangible assets	$ 30
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	3 years
Series of Individually Immaterial Business Acquisitions | Other
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Finite-lived intangible assets	$ 5
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	3 years