Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 30, 2019
Document and Entity Information
Trading Symbol	GRA
Entity Registrant Name	W R GRACE & CO.
Entity Address, Address Line One	7500 Grace Drive
Entity Address, City or Town	Columbia
Entity Address, State or Province	Maryland
Entity Address, Postal Zip Code	21044-4098
Entity Central Index Key	0001045309
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		66,914,212
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Local Phone Number	(410) 531-4000