Restructuring Expenses and Repositioning Expenses - Expenses and Asset Impairments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 0.2	$ 2.4	$ 3.2	$ 4.4
Catalysts Technologies
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.1	2.2	2.2	3.7
Materials Technologies
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.0	0.1	1.2	0.5
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 0.1	$ 0.1	$ (0.2)	$ 0.2