Restructuring and Other Charges - Activity and Reserve Balances for Restructuring Charges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			$ 54
Cash payments			(37)
Restructuring charges	$ 8	$ 22	22	$ 166
Other			(23)
Restructuring reserve ending balance	16		16
Settlements	3	3	9	67
Restructuring and other charges	8	22	22	166
Pension benefits
Restructuring Reserve [Roll Forward]
Restructuring charges	3	8	9	10
Settlements	3	8	9	72
Restructuring and other charges	3	8	9	$ 10
Layoff costs
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			54
Cash payments			(37)
Restructuring charges		17	10
Other			(11)
Restructuring reserve ending balance	16		16
Restructuring and other charges		$ 17	10
Other exit costs
Restructuring Reserve [Roll Forward]
Restructuring reserve beginning balance			0
Cash payments			0
Restructuring charges			12
Other			(12)
Restructuring reserve ending balance	$ 0		0
Restructuring and other charges			12
Other layoff costs
Restructuring Reserve [Roll Forward]
Restructuring charges			2
Restructuring and other charges			2
Other exit costs, other
Restructuring Reserve [Roll Forward]
Restructuring charges			11
Restructuring and other charges			$ 11