Restructuring Expenses and Repositioning Expenses - Expenses and Asset Impairments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 5.3	$ 1.8	$ 10.1	$ 18.2
Grace Catalysts Technologies [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	2.4	1.6	2.8	2.7
Grace Materials Technologies [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	0.2	(0.1)	0.5	15.1
Corporate, Non-Segment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 2.7	$ 0.3	$ 6.8	$ 0.4