Segment information - Geographical Sales and Property, pant and equipment, net (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets
Net sales	$ 229.5	$ 264.1	$ 260.3	$ 218.5	$ 210.9	$ 252.4	$ 245.4	$ 199.6	$ 972.4	$ 908.3	$ 958.3
Property, plant and equipment, net	438.5				422.8				438.5	422.8	437.5
North America
Revenues from External Customers and Long-Lived Assets
Net sales									662.9	597.8	623.0
Property, plant and equipment, net	358.4				349.1				358.4	349.1	338.7
Asia Pacific
Revenues from External Customers and Long-Lived Assets
Net sales									142.5	138.8	149.3
Property, plant and equipment, net	79.3				72.7				79.3	72.7	76.9
Europe, Middle East and Africa
Revenues from External Customers and Long-Lived Assets
Net sales									149.2	151.1	155.9
Property, plant and equipment, net	0.7				0.7				0.7	0.7	0.8
South America
Revenues from External Customers and Long-Lived Assets
Net sales									17.8	20.6	30.1
Property, plant and equipment, net	$ 0.1				$ 0.3				$ 0.1	$ 0.3	$ 21.1