Goodwill and Other Intangible Assets - Other Intangible Rollforward (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite-lived Intangible Assets [Roll Forward]
Other intangible assets balance at December 31, 2017	$ 10,269
Acquisitions		$ 130
Foreign currency translation	15
Amortization of other intangible assets	(69)
Other activity, net	(19)
Other intangible assets balance at March 31, 2018	$ 10,326	$ 10,269