Restructuring and other (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring and other	$ 6	$ 34	$ 13	$ 86
Employee severance
Restructuring Cost and Reserve [Line Items]
Restructuring and other	2	16	5	21
Acquisitions and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other	0	0	0	8
Contingent consideration adjustment
Restructuring Cost and Reserve [Line Items]
Restructuring and other	2	0	2	18
Legal and related
Restructuring Cost and Reserve [Line Items]
Restructuring and other	0	10	0	26
Restructuring, integration and other
Restructuring Cost and Reserve [Line Items]
Restructuring and other	$ 2	$ 8	$ 6	$ 13