Company Restructuring - Changes in the restructuring liability (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Restructuring Reserve
Restructuring liability as of December 31, 2019	$ 22
Expense incurred	260
Adjustments to liability	(1)
Payments and non-cash pension settlements	(209)
Restructuring liability as of December 31, 2020	72
Employee costs
Restructuring Reserve
Restructuring liability as of December 31, 2019	14
Expense incurred	214
Adjustments to liability	3
Payments and non-cash pension settlements	(159)
Restructuring liability as of December 31, 2020	72
Exit costs
Restructuring Reserve
Restructuring liability as of December 31, 2019	8
Expense incurred	46
Adjustments to liability	(4)
Payments and non-cash pension settlements	(50)
Restructuring liability as of December 31, 2020	$ 0