| Cover | Feb. 25, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Feb. 25, 2022 |
| Entity Registrant Name | ECOVYST INC. |
| Entity File Number | 001-38221 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 81-3406833 |
| Entity Address, Address Line One | 300 Lindenwood Drive |
| Entity Address, City or Town | Malvern |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 19355 |
| City Area Code | (610) |
| Local Phone Number | 651-4400 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, par value $0.01 per share |
| Trading Symbol | ECVT |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001708035 |
| Amendment Flag | false |
