| Document and Entity Information | Dec. 23, 2024 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0002038118 |
| Document Type | 8-K |
| Document Period End Date | Dec. 23, 2024 |
| Entity Registrant Name | FirstEnergy Transmission, LLC |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 333-282554 |
| Entity Tax Identification Number | 20-5763884 |
| Entity Address, Address Line One | 5001 NASA Boulevard |
| Entity Address, City or Town | Fairmont |
| Entity Address, State or Province | WV |
| Entity Address, Postal Zip Code | 26554 |
| City Area Code | (800) |
| Local Phone Number | 736-3402 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
