Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			$ 13
Cash payments			(24)
Restructuring charges			144
Other			(77)
Restructuring reserve ending balance	$ 56		56
Restructuring charges	105	$ 472	144	$ 516
Gain on sale of assets	(2)	(5)	(4)	(7)
Layoff costs
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			13
Cash payments			(24)
Restructuring charges			131
Other			(64)
Restructuring reserve ending balance	56		56
Restructuring charges	54	$ 15	76	$ 68
Other exit costs
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			0
Cash payments			0
Restructuring charges			13
Other			(13)
Restructuring reserve ending balance	0		0
Restructuring charges	$ 2		5
Other Exit Costs, United Kingdom Pension Settlement Accounting
Restructuring Reserve [Roll Forward]
Restructuring charges			64
Other Exit Costs, Impairments Of Assets
Restructuring Reserve [Roll Forward]
Restructuring charges			6
Other Exit Costs, Post Closing Adjustment
Restructuring Reserve [Roll Forward]
Restructuring charges			6
Other Exit Costs, Other
Restructuring Reserve [Roll Forward]
Restructuring charges			3
Sale of Assets
Restructuring Reserve [Roll Forward]
Gain on sale of assets			$ 2