Other Expense, Net - Schedule (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Other Income and Expenses [Abstract]
Non-service related net periodic benefit cost	$ 30	$ 27			$ 88	$ 83
Interest income	(5)	(6)			(21)	(16)
Foreign currency losses, net	7	6			3	20
Net loss from asset sales	2	2			6	7
Other, net	(3)	(21)			16	(25)
Total	$ 31	$ 8	$ 92	$ 69	$ 92	$ 69