Other Financial Data - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at January 1	$ 59	$ 56	$ 58
Provision charged to Other general expenses	24	18	10
Accounts written off, net of recoveries	(25)	(18)	(15)
Foreign currency translation	4	3	3
Balance at December 31	$ 62	$ 59	$ 56