Restructuring Expenses and Repositioning Expenses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring expenses and related asset impairments
Restructuring expenses	$ 14.0	$ 11.5	$ 24.3
Grace Catalysts Technologies
Restructuring expenses and related asset impairments
Restructuring expenses	13.7	3.7	3.4
Grace Materials Technologies
Restructuring expenses and related asset impairments
Restructuring expenses	0.5	(0.1)	15.1
Corporate, Non-Segment [Member]
Restructuring expenses and related asset impairments
Restructuring expenses	$ (0.2)	$ 7.9	$ 5.8