Consolidated Statements of Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Net sales	$ 429.5	$ 390.5	$ 827.5	$ 753.3
Cost of goods sold	260.2	217.3	505.0	427.4
Gross profit	169.3	173.2	322.5	325.9
Selling, general and administrative expenses	70.3	66.4	136.8	134.4
Research and development expenses	12.9	12.4	26.1	24.1
Provision for environmental remediation, net	13.2	5.3	13.2	7.5
Equity in earnings of unconsolidated affiliate	(6.1)	(2.6)	(13.1)	(9.5)
Restructuring and repositioning expenses	5.4	9.4	7.7	23.0
Interest expense and related financing costs	20.1	19.8	39.6	41.8
Other (income) expense, net	(9.6)	3.1	(11.8)	13.8
Total costs and expenses	106.2	113.8	198.5	235.1
Income (loss) from continuing operations before income taxes	63.1	59.4	124.0	90.8
(Provision for) benefit from income taxes	(19.6)	(21.5)	(37.6)	(42.7)
Income (loss) from continuing operations	43.5	37.9	86.4	48.1
Income (loss) from discontinued operations, net of income taxes	0.0	0.6	0.0	(9.3)
Net income (loss)	43.5	38.5	86.4	38.8
Less: Net (income) loss attributable to noncontrolling interests	0.4	0.2	0.4	0.4
Net income (loss) attributable to W. R. Grace & Co. shareholders	43.9	38.7	86.8	39.2
Amounts Attributable to W. R. Grace & Co. Shareholders:
Income (loss) from continuing operations attributable to W. R. Grace & Co. shareholders	$ 43.9	$ 38.1	$ 86.8	$ 48.5
Basic earnings per share:
Income (loss) from continuing operations	$ 0.64	$ 0.54	$ 1.27	$ 0.69
Income (loss) from discontinued operations, net of income taxes	0.00	0.01	0.00	(0.13)
Net income (loss)	$ 0.64	$ 0.55	$ 1.27	$ 0.56
Weighted average number of basic shares	68.3	70.5	68.3	70.5
Diluted earnings per share:
Income (loss) from continuing operations	$ 0.64	$ 0.54	$ 1.27	$ 0.68
Income (loss) from discontinued operations, net of income taxes	0.00	0.01	0.00	(0.13)
Net income (loss)	$ 0.64	$ 0.55	$ 1.27	$ 0.55
Weighted average number of diluted shares	68.4	70.9	68.5	71.0
Dividends per common share	$ 0.21	$ 0.17	$ 0.42	$ 0.17