Other Financial Data - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of period	$ 62	$ 59	$ 59	$ 56
Provision charged to Other general expenses	9	5	21	16
Accounts written off, net of recoveries	(8)	0	(17)	(10)
Foreign currency translation and other	3	(5)	3	(3)
Balance at end of period	$ 66	$ 59	$ 66	$ 59