Restructuring and other (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring and other	$ 52.2	$ 9.2
Employee severance
Restructuring Cost and Reserve [Line Items]
Restructuring and other	5.1	2.7
Acquisitions and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other	7.8	3.4
Contingent consideration adjustment
Restructuring Cost and Reserve [Line Items]
Restructuring and other	18.0	0.0
Legal and related
Restructuring Cost and Reserve [Line Items]
Restructuring and other	16.0	0.0
Restructuring, integration and other
Restructuring Cost and Reserve [Line Items]
Restructuring and other	5.3	$ 3.1
NYX | Acquisitions and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other	$ 7.7