Restructuring and other (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring and other	$ 11	$ 339	$ 24	$ 424
Employee severance
Restructuring Cost and Reserve [Line Items]
Restructuring and other	3	11	8	32
Acquisitions and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other	0	0	0	7
Contingent consideration adjustment
Restructuring Cost and Reserve [Line Items]
Restructuring and other	0	8	2	26
Legal and related
Restructuring Cost and Reserve [Line Items]
Restructuring and other	0	310	0	336
Restructuring, integration and other
Restructuring Cost and Reserve [Line Items]
Restructuring and other	$ 8	$ 10	$ 14	$ 23