Business Segment Information - Information by Geographical Area (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue and property, plant and equipment by geographical area
Revenue	$ 553.6	$ 466.6	$ 443.7	$ 431.7	$ 530.5	$ 435.6	$ 414.9	$ 384.9	$ 1,895.6	$ 1,765.9	$ 1,611.3
Property, plant and equipment, net	270.6				266.5				270.6	266.5	239.1
United States
Revenue and property, plant and equipment by geographical area
Revenue									489.4	434.7	428.2
Property, plant and equipment, net	44.1				46.2				44.1	46.2	46.4
Germany
Revenue and property, plant and equipment by geographical area
Revenue									201.1	200.2	189.5
Property, plant and equipment, net	137.0				140.9				137.0	140.9	122.5
Rest of Europe
Revenue and property, plant and equipment by geographical area
Revenue									500.2	465.0	393.4
Property, plant and equipment, net	78.7				71.9				78.7	71.9	63.3
Asia Pacific
Revenue and property, plant and equipment by geographical area
Revenue									549.2	514.8	458.1
Property, plant and equipment, net	6.3				5.4				6.3	5.4	4.4
Other
Revenue and property, plant and equipment by geographical area
Revenue									155.7	151.2	142.1
Property, plant and equipment, net	$ 4.5				$ 2.1				$ 4.5	$ 2.1	$ 2.5