Consolidated Statements of Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income Statement [Abstract]
Net sales	$ 390.5	$ 407.2	$ 753.3	$ 804.2
Cost of goods sold	217.3	239.4	427.4	489.4
Gross profit	173.2	167.8	325.9	314.8
Selling, general and administrative expenses	66.4	73.5	134.4	150.5
Research and development expenses	12.4	12.3	24.1	24.4
Equity in earnings of unconsolidated affiliate	(2.6)	(2.3)	(9.5)	(8.5)
Restructuring and repositioning expenses	9.4	4.2	23.0	9.7
Loss on early extinguishment of debt	0.0	0.0	11.1	0.0
Interest expense and related financing costs	19.8	24.6	41.8	49.3
Other expense (income), net	8.4	5.0	10.2	(8.8)
Total costs and expenses	113.8	117.3	235.1	216.6
Income from continuing operations before income taxes	59.4	50.5	90.8	98.2
Provision for income taxes	(21.5)	(17.9)	(42.7)	(35.4)
Income from continuing operations	37.9	32.6	48.1	62.8
Income (loss) from discontinued operations, net of income taxes	0.6	24.8	(9.3)	47.3
Net income	38.5	57.4	38.8	110.1
Less: Net loss attributable to noncontrolling interests	0.2	0.0	0.4	0.0
Net income attributable to W. R. Grace & Co. shareholders	38.7	57.4	39.2	110.1
Amounts Attributable to W. R. Grace & Co. Shareholders:
Income from continuing operations attributable to W. R. Grace & Co. shareholders	$ 38.1	$ 32.6	$ 48.5	$ 62.8
Basic earnings per share:
Income from continuing operations	$ 0.54	$ 0.45	$ 0.69	$ 0.86
Income (loss) from discontinued operations, net of income taxes	0.01	0.34	(0.13)	0.65
Net income	$ 0.55	$ 0.79	$ 0.56	$ 1.51
Weighted average number of basic shares	70.5	72.6	70.5	72.7
Diluted earnings per share:
Income from continuing operations	$ 0.54	$ 0.45	$ 0.68	$ 0.86
Income (loss) from discontinued operations, net of income taxes	0.01	0.33	(0.13)	0.64
Net income	$ 0.55	$ 0.78	$ 0.55	$ 1.50
Weighted average number of diluted shares	70.9	73.2	71.0	73.3
Dividends per common share	$ 0.17	$ 0.00	$ 0.17	$ 0.00