Business Segment Information - Information by Geographical Area (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
Revenue and property, plant and equipment by geographical area
Revenue	$ 530.5	$ 435.6	$ 414.9	$ 384.9	$ 470.3	$ 393.9	$ 371.7	$ 375.4	$ 1,765.9	$ 1,611.3	$ 1,623.8
Property, plant and equipment, net	266.5				239.1				266.5	239.1
United States
Revenue and property, plant and equipment by geographical area
Revenue									434.7	428.2	380.4
Property, plant and equipment, net	46.2				46.4				46.2	46.4
Germany
Revenue and property, plant and equipment by geographical area
Revenue									200.2	189.5	198.9
Property, plant and equipment, net	140.9				122.5				140.9	122.5
Rest of Europe
Revenue and property, plant and equipment by geographical area
Revenue									465.0	393.4	479.6
Property, plant and equipment, net	71.9				63.3				71.9	63.3
Asia Pacific
Revenue and property, plant and equipment by geographical area
Revenue									514.8	458.1	414.9
Property, plant and equipment, net	5.4				4.4				5.4	4.4
Other
Revenue and property, plant and equipment by geographical area
Revenue									151.2	142.1	$ 150.0
Property, plant and equipment, net	$ 2.1				$ 2.5				$ 2.1	$ 2.5