Restructuring Expenses and Repositioning Expenses - Expenses and Asset Impairments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 1.1	$ 1.0
Catalysts Technologies
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.2	0.4
Materials Technologies
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	1.0	0.4
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ (0.1)	$ 0.2