Consolidated Statements of Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Net sales	$ 398.0	$ 362.8
Cost of goods sold	244.8	210.1
Gross profit	153.2	152.7
Selling, general and administrative expenses	66.5	68.0
Research and development expenses	13.2	11.7
Provision for environmental remediation, net	0.0	2.2
Equity in earnings of unconsolidated affiliate	(7.0)	(6.9)
Restructuring and repositioning expenses	2.3	13.6
Interest expense and related financing costs	19.5	22.0
Other (income) expense, net	(2.2)	10.7
Total costs and expenses	92.3	121.3
Income (loss) from continuing operations before income taxes	60.9	31.4
(Provision for) benefit from income taxes	(18.0)	(21.2)
Income (loss) from continuing operations	42.9	10.2
Income (loss) from discontinued operations, net of income taxes	0.0	(9.9)
Net income (loss)	42.9	0.3
Less: Net (income) loss attributable to noncontrolling interests	0.0	0.2
Net income (loss) attributable to W. R. Grace & Co. shareholders	42.9	0.5
Amounts Attributable to W. R. Grace & Co. Shareholders:
Income (loss) from continuing operations attributable to W. R. Grace & Co. shareholders	$ 42.9	$ 10.4
Basic earnings per share:
Income (loss) from continuing operations	$ 0.63	$ 0.15
Income (loss) from discontinued operations, net of income taxes	0.00	(0.14)
Net income (loss)	$ 0.63	$ 0.01
Weighted average number of basic shares	68.3	70.6
Diluted earnings per share:
Income (loss) from continuing operations	$ 0.63	$ 0.15
Income (loss) from discontinued operations, net of income taxes	0.00	(0.14)
Net income (loss)	$ 0.63	$ 0.01
Weighted average number of diluted shares	68.5	71.1
Dividends per common share	$ 0.21	$ 0.00