| Document and Entity Information | Oct. 28, 2020 |
| Document and Entity Information | |
| Document Type | 8-K |
| Document Period End Date | Oct. 28, 2020 |
| Entity Registrant Name | W. R. GRACE & CO. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-13953 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $.01 par value per share |
| Trading Symbol | GRA |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001045309 |
