Goodwill and Other Intangible Assets (Changes in Carrying Amount of Goodwill) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill, Beginning of Period		$ 15,599	$ 15,869
Acquisitions	$ 205	139	664
Foreign currency translation and other adjustments	(3)	(71)	(65)
Allocation in the fourth quarter of 2015	0
Goodwill, End of Period	15,869		16,468
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Goodwill [Roll Forward]
Goodwill, Beginning of Period		15,599	15,456
Acquisitions	201	139	625
Foreign currency translation and other adjustments	4	(71)	(54)
Allocation in the fourth quarter of 2015	(416)
Goodwill, End of Period	15,456		16,027
Other Bets
Goodwill [Roll Forward]
Goodwill, Beginning of Period		0	413
Acquisitions	4	0	39
Foreign currency translation and other adjustments	(7)	$ 0	(11)
Allocation in the fourth quarter of 2015	416
Goodwill, End of Period	$ 413		$ 441