Consolidated Statements of Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Net sales	$ 404.5	$ 399.2	$ 1,157.8	$ 1,203.4
Cost of goods sold	236.3	233.1	663.7	722.5
Gross profit	168.2	166.1	494.1	480.9
Selling, general and administrative expenses	67.1	70.5	201.5	221.0
Research and development expenses	12.1	11.8	36.2	36.2
Provision for environmental remediation, net	11.9	4.2	19.4	1.6
Equity in earnings of unconsolidated affiliate	(8.5)	(3.6)	(18.0)	(12.1)
Restructuring and repositioning expenses	5.6	5.2	28.6	14.9
Interest expense and related financing costs	19.8	25.2	61.6	74.5
Other (income) expense, net	(0.5)	1.5	13.3	(4.7)
Total costs and expenses	107.5	114.8	342.6	331.4
Income from continuing operations before income taxes	60.7	51.3	151.5	149.5
Provision for income taxes	(19.4)	(17.7)	(62.1)	(53.1)
Income from continuing operations	41.3	33.6	89.4	96.4
(Loss) income from discontinued operations, net of income taxes	(1.6)	(19.9)	(10.9)	27.4
Net income	39.7	13.7	78.5	123.8
Less: Net (income) loss attributable to noncontrolling interests	(0.1)	0.1	0.3	0.1
Net income attributable to W. R. Grace & Co. shareholders	39.6	13.8	78.8	123.9
Amounts Attributable to W. R. Grace & Co. Shareholders:
Income from continuing operations attributable to W. R. Grace & Co. shareholders	$ 41.2	$ 33.7	$ 89.7	$ 96.5
Basic earnings per share:
Income from continuing operations	$ 0.59	$ 0.47	$ 1.27	$ 1.33
(Loss) income from discontinued operations, net of income taxes	(0.03)	(0.28)	(0.15)	0.38
Net income	$ 0.56	$ 0.19	$ 1.12	$ 1.71
Weighted average number of basic shares	70.3	72.1	70.5	72.5
Diluted earnings per share:
Income from continuing operations	$ 0.58	$ 0.46	$ 1.27	$ 1.32
(Loss) income from discontinued operations, net of income taxes	(0.02)	(0.27)	(0.16)	0.37
Net income	$ 0.56	$ 0.19	$ 1.11	$ 1.69
Weighted average number of diluted shares	70.7	72.7	70.9	73.1
Dividends per common share	$ 0.17	$ 0.00	$ 0.34	$ 0.00