Supplemental Disclosures (Schedule of Analysis 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 beginning of year	$ 110	$ 96	$ 87
Provision charged to operations	34	31	31
Accounts written-off, net of recoveries	(24)	(17)	(20)
Effect of exchange rate changes and other	(8)	0	(2)
Balance at end of year	$ 112	$ 110	$ 96