| Cover | Apr. 30, 2021 | Mar. 10, 2021 |
| Document Information [Line Items] | ||
| Document Type | 8-K | |
| Document Period End Date | Apr. 30, 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, Postal Zip Code | 43215-3799 | |
| 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 | |
| Entity Address, Address Line One | 180 East Broad St., | |
| Entity Address, City or Town | Columbus, | |
| Entity Address, State or Province | OH | |
| Local Phone Number | 225-4000 | |
| City Area Code | 614 |
