Restructuring and other (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring and other	$ 7	$ 52
Employee severance
Restructuring Cost and Reserve [Line Items]
Restructuring and other	3	5
Acquisitions and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other	0	8
Contingent consideration adjustment
Restructuring Cost and Reserve [Line Items]
Restructuring and other	0	18
Legal and related
Restructuring Cost and Reserve [Line Items]
Restructuring and other	0	16
Restructuring, integration and other
Restructuring Cost and Reserve [Line Items]
Restructuring and other	$ 4	$ 5