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]
Beginning Balance	$ 109	$ 77	$ 70
Provision charged to expense	18	32	16
Accounts written off	(12)	(10)	(9)
Acquisitions, currency translation and other	2	10
Ending Balance	$ 117	$ 109	$ 77