Consolidated Statements of Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Net sales	$ 362.8	$ 397.0
Cost of goods sold	210.1	250.0
Gross profit	152.7	147.0
Selling, general and administrative expenses	68.0	77.0
Research and development expenses	11.7	12.1
Interest expense and related financing costs	22.0	24.7
Repositioning expenses	5.1	0.3
Equity in earnings of unconsolidated affiliate	(6.9)	(6.2)
Loss on early extinguishment of debt	11.1	0.0
Other expense (income), net	10.3	(8.6)
Total costs and expenses	121.3	99.3
Income from continuing operations before income taxes	31.4	47.7
Provision for income taxes	(24.4)	(17.5)
Income from continuing operations	7.0	30.2
(Loss) income from discontinued operations, net of income taxes	(9.9)	22.5
Net (loss) income	(2.9)	52.7
Less: Net loss attributable to noncontrolling interests	0.2	0.0
Net (loss) income attributable to W. R. Grace & Co. shareholders	(2.7)	52.7
Amounts Attributable to W. R. Grace & Co. Shareholders:
Income from continuing operations attributable to W. R. Grace & Co. shareholders	$ 7.2	$ 30.2
Basic earnings per share:
Income from continuing operations (in USD per share)	$ 0.10	$ 0.41
(Loss) income from discontinued operations, net of income taxes (in USD per share)	(0.14)	0.31
Net income (in USD per share)	$ (0.04)	$ 0.72
Weighted average number of basic shares (in shares)	70.6	72.8
Diluted earnings per share:
Income from continuing operations (in USD per share)	$ 0.10	$ 0.41
(Loss) income from discontinued operations (in USD per share)	(0.14)	0.31
Net income (loss) attributable to W. R. Grace & Co. shareholders (in USD per share)	$ (0.04)	$ 0.72
Weighted average number of diluted shares (in shares)	70.6	73.5