Company Restructuring - Changes in the restructuring liability (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Restructuring Reserve
Restructuring liability as of December 31, 2017	$ 45
Expense incurred	49
Adjustments to liability	0
Payments and non-cash pension settlements	(27)
Restructuring liability as of June 30, 2018	67
Employee costs
Restructuring Reserve
Restructuring liability as of December 31, 2017	15
Expense incurred	31
Adjustments to liability	1
Payments and non-cash pension settlements	(6)
Restructuring liability as of June 30, 2018	41
Exit costs
Restructuring Reserve
Restructuring liability as of December 31, 2017	30
Expense incurred	18
Adjustments to liability	(1)
Payments and non-cash pension settlements	(21)
Restructuring liability as of June 30, 2018	$ 26