Segment information - Revenue And Operating Profits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 849.7	$ 805.9	$ 1,728.8	$ 1,594.3
Operating Profit	61.7	48.3	126.5	119.2
Foreign currency transaction gains (losses)			2.2	(8.4)
Reportable segments
Segment Reporting Information [Line Items]
Revenues	824.1	759.6	1,677.4	1,499.9
Operating Profit	98.4	78.6	200.2	153.4
Corporate expenses
Segment Reporting Information [Line Items]
General, administrative and other expenses	(20.9)	(18.3)	(52.0)	(37.5)
Foreign currency transaction gains (losses)	(1.7)	1.4	(2.2)	0.2
Reconciliation of segment policies to GAAP	0.4	(0.9)	1.7	(1.8)
Other items not allocated to segments
Segment Reporting Information [Line Items]
Acquisitions and dispositions, Revenues	0.0	0.0	0.0	0.0
Reorganization and Restructuring	(4.5)	(5.6)	(8.2)	(9.7)
Acquisitions and dispositions, Operating profit	(7.4)	(2.4)	(13.9)	(2.0)
Reporting compliance	(1.4)		(1.4)
Other items not allocated to segments | Venezuela operations
Segment Reporting Information [Line Items]
Revenues	25.6	46.3	51.4	94.4
Operating Profit	(1.2)	(4.5)	2.3	16.6
North America | Reportable segments
Segment Reporting Information [Line Items]
Revenues	324.0	311.0	644.1	615.6
Operating Profit	26.1	16.8	46.7	27.0
South America | Reportable segments
Segment Reporting Information [Line Items]
Revenues	233.3	204.6	488.1	406.8
Operating Profit	46.1	36.4	101.7	75.6
Rest of World | Reportable segments
Segment Reporting Information [Line Items]
Revenues	266.8	244.0	545.2	477.5
Operating Profit	$ 26.2	$ 25.4	$ 51.8	$ 50.8