Other Expense, Net - Schedule (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Other Income and Expenses [Abstract]
Non-service related net periodic benefit cost	$ 29	$ 28			$ 58	$ 56
Interest income	(6)	(4)			(16)	(10)
Foreign currency (gains) losses, net	(4)	17			(4)	14
Net loss from asset sales	2	2			4	5
Other, net	8	(2)			19	(4)
Total	$ 29	$ 41	$ 61	$ 61	$ 61	$ 61