Supplemental Income Statement Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Income Statement Information
Interest expense		$ 350	$ 322	$ 199
Interest income		(70)	(50)	(29)
Loss on extinguishment of debt	$ 96
Pension and postretirement net periodic benefit cost (benefit)		(73)	(128)	(196)
Total		$ 207	$ 144	$ (26)