| Document and Entity Information | Dec. 14, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Dec. 14, 2020 |
| Entity Registrant Name | Trinseo S.A. |
| Entity Incorporation, State or Country Code | N4 |
| Entity File Number | 001-36473 |
| Entity Tax Identification Number | 00-0000000 |
| Entity Address, Address Line One | 1000 Chesterbrook Boulevard |
| Entity Address, Address Line Two | Suite 300 |
| Entity Address, City or Town | Berwyn |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 19312 |
| City Area Code | 610 |
| Local Phone Number | 240-3200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Title of 12(b) Security | Ordinary Shares, par value $0.01 per share |
| Trading Symbol | TSE |
| Security Exchange Name | NYSE |
| Amendment Flag | false |
| Entity Central Index Key | 0001519061 |
