Goodwill and Intangible Assets - Change in Carrying Amount (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Goodwill [Roll Forward]
Goodwill beginning	$ 17,981	$ 839
Goodwill acquired	45	17,150
Effect of currency translation adjustment		(8)
Goodwill ending	$ 18,026	$ 17,981