| Document and Entity Information | Sep. 14, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001693415 |
| Current Fiscal Year End Date | --12-31 |
| Document Type | 8-K |
| Document Period End Date | Sep. 14, 2021 |
| Entity Registrant Name | Translate Bio, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38550 |
| Entity Tax Identification Number | 61-1807780 |
| Entity Address, Address Line One | 29 Hartwell Avenue |
| Entity Address, City or Town | Lexington |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 02421 |
| City Area Code | (617) |
| Local Phone Number | 945-7361 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, par value $0.001 per share |
| Trading Symbol | TBIO |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
