Consolidated Statements of Comprehensive (Loss) Income (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (2.9)	$ 52.7
Other comprehensive (loss) income:
Defined benefit pension and other postretirement plans, net of income taxes	(0.3)	(0.4)
Currency translation adjustments	(5.4)	(10.8)
Loss from hedging activities, net of income taxes	(3.0)	(1.9)
Total other comprehensive income attributable to noncontrolling interests	2.6	0.1
Total other comprehensive loss	(6.1)	(13.0)
Comprehensive (loss) income	(9.0)	39.7
Less: comprehensive income attributable to noncontrolling interests	(2.4)	(0.1)
Comprehensive (loss) income attributable to W. R. Grace & Co. shareholders	$ (11.4)	$ 39.6