Restructuring Expenses and Repositioning Expenses - Expenses and Asset Impairments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 2.9	$ 1.9	$ 3.1	$ 3.0
Catalysts Technologies
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	2.8	1.9	2.8	2.1
Materials Technologies
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.1	0.2	0.3	1.2
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 0.0	$ (0.2)	$ 0.0	$ (0.3)