Company Restructuring - Changes in the restructuring liability (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)
Restructuring Reserve
Balance as of December 31, 2017	$ 45
Expense incurred	19
Adjustments to liability	(1)
Payments applied against liability	(3)
Balance as of March 31, 2018	60
Restructuring, incurred cost	3
Employee costs
Restructuring Reserve
Balance as of December 31, 2017	15
Expense incurred	13
Adjustments to liability	0
Payments applied against liability	0
Balance as of March 31, 2018	28
Exit costs
Restructuring Reserve
Balance as of December 31, 2017	30
Expense incurred	6
Adjustments to liability	(1)
Payments applied against liability	(3)
Balance as of March 31, 2018	$ 32