Consolidated Statements of Operations (unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 469.5	$ 431.5
Cost of goods sold	280.9	262.0
Gross profit	188.6	169.5
Selling, general and administrative expenses	73.2	68.4
Research and development expenses	17.0	14.7
Costs related to legacy matters	46.9	2.0
Equity in earnings of unconsolidated affiliate	(4.1)	(5.4)
Restructuring and repositioning expenses	2.3	5.6
Interest expense and related financing costs	20.0	19.3
Other (income) expense, net	(2.2)	(3.3)
Total costs and expenses	153.1	101.3
Income (loss) before income taxes	35.5	68.2
(Provision for) benefit from income taxes	(10.9)	(24.8)
Net income (loss)	24.6	43.4
Less: Net (income) loss attributable to noncontrolling interests	0.1	0.2
Net income (loss) attributable to W. R. Grace & Co. shareholders	$ 24.7	$ 43.6
Basic earnings per share:
Net income (loss) (in dollars per share)	$ 0.37	$ 0.64
Weighted average number of basic shares (in shares)	66.8	67.6
Diluted earnings per share:
Net income (loss) (in dollars per shares)	$ 0.37	$ 0.64
Weighted average number of diluted shares (in shares)	66.9	67.7
Dividends per common share (in dollars per shares)	$ 0.27	$ 0.24