Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2020	Jun. 30, 2019
Document and Entity Information [Abstract]
Entity Central Index Key	0001045309
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	1-13953
Entity Registrant Name	W. R. GRACE & CO.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	65-0773649
Entity Address, Address Line One	7500 Grace Drive
Entity Address, City or Town	Columbia
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	21044-4098
City Area Code	(410)
Local Phone Number	531-4000
Title of 12(b) Security	Common Stock, $0.01 par value per share
Trading Symbol	GRA
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 4,323,527,569
Entity Bankruptcy Proceedings, Reporting Current	true
Entity Common Stock, Shares Outstanding		66,720,858