Segment Information - Reportable Segment Data (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment	Jun. 30, 2018 USD ($)
Operating segment information
Number of reportable segments | segment			2
Net Sales
Revenues	$ 513.6	$ 485.7	$ 983.1	$ 917.2
Adjusted EBIT
Total	126.7	119.5	231.1	215.3
Reconciliation of operating segment data to financial statements
Costs related to legacy matters	(1.5)	(2.2)	(48.4)	(4.2)
Restructuring and repositioning expenses	(6.4)	(18.8)	(8.7)	(24.4)
Adjusted EBIT inventory write-off	(3.6)	0.0	(3.6)	0.0
Third-party acquisition-related costs	(1.0)	(5.8)	(1.3)	(6.7)
Amortization of acquired inventory fair value adjustment	0.0	(4.6)	0.0	(4.6)
Loss on early extinguishment of debt	0.0	(4.8)	0.0	(4.8)
Interest expense, net	(19.2)	(19.5)	(38.5)	(38.4)
Net income (loss) attributable to noncontrolling interests	0.2	(0.2)	0.1	(0.4)
Income (loss) before income taxes	95.2	63.6	$ 130.7	131.8
Catalysts Technologies
Operating segment information
Number of reportable segments | segment			1
Number of operating segments | segment			2
Net Sales
Revenues	395.7	364.4	$ 745.4	680.2
Materials Technologies
Net Sales
Revenues	117.9	121.3	237.7	237.0
Corporate
Adjusted EBIT
Operating income	(18.0)	(19.8)	(34.2)	(36.4)
Certain pension costs	(4.6)	(4.0)	(9.4)	(7.8)
Operating Segments | Catalysts Technologies
Net Sales
Revenues	395.7	364.4	745.4	680.2
Adjusted EBIT
Operating income	125.2	113.7	226.6	205.8
Operating Segments | Materials Technologies
Net Sales
Revenues	117.9	121.3	237.7	237.0
Adjusted EBIT
Operating income	$ 24.1	$ 29.6	$ 48.1	$ 53.7