Consolidated Statements of Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net sales	$ 431.5	$ 398.0
Cost of goods sold	262.0	244.8
Gross profit	169.5	153.2
Selling, general and administrative expenses	69.3	65.5
Research and development expenses	14.7	13.9
Provision for environmental remediation, net	0.1	0.0
Equity in earnings of unconsolidated affiliate	(5.4)	(7.0)
Restructuring and repositioning expenses	5.6	2.3
Interest expense and related financing costs	19.3	19.5
Other (income) expense, net	2.3	1.9
Total costs and expenses	101.3	92.3
Income (loss) before income taxes	68.2	60.9
(Provision for) benefit from income taxes	(24.8)	(18.0)
Net income (loss)	43.4	42.9
Less: Net (income) loss attributable to noncontrolling interests	0.2	0.0
Net income (loss) attributable to W. R. Grace & Co. shareholders	$ 43.6	$ 42.9
Basic earnings per share:
Net income (loss)	$ 0.64	$ 0.63
Weighted average number of basic shares	67.6	68.3
Diluted earnings per share:
Net income (loss)	$ 0.64	$ 0.63
Weighted average number of diluted shares	67.7	68.5
Dividends per common share	$ 0.24	$ 0.21