| Cover | Mar. 10, 2021 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Mar. 10, 2021 |
| Entity Registrant Name | HEXION INC. |
| Entity Incorporation, State or Country Code | NJ |
| Entity File Number | 1-71 |
| Entity Tax Identification Number | 13-0511250 |
| Entity Address, Address Line One | 180 East Broad St., |
| Entity Address, City or Town | Columbus, |
| Entity Address, State or Province | OH |
| Entity Address, Postal Zip Code | 43215-3799 |
| City Area Code | 614 |
| Local Phone Number | 225-4000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Central Index Key | 0000013239 |
| Amendment Flag | false |
| Entity Emerging Growth Company | false |
