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CAPITALIZATION - Long-term Debt Redemption and Issuance (Details) - USD ($) $ in Millions |  | 1 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Apr. 30, 2024 | Dec. 31, 2024 | Nov. 30, 2024 | Sep. 30, 2024 | Aug. 31, 2024 | May 31, 2024 | Apr. 30, 2024 | Mar. 31, 2024 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 05, 2024 | Sep. 05, 2024
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Debt issuances |  |  |  |  |  |  |  |  | $ 2,100 | $ 3,150 | $ 700 |  |
Repayments of debt |  |  |  |  |  |  |  |  | $ 2,760 | $ 537 | $ 3,005 |  |
7.375% Unsecured Notes Due April, 2034 | Unsecured Notes | FE |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate | 7.375% |  |  |  |  |  | 7.375% |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  | $ 463 |  |  |  |  |  |
Make-whole premium | $ 80 |  |  |  |  |  | 80 |  |  |  |  |  |
Losses on deferred cash flows | 4 |  |  |  |  |  |  |  |  |  |  |  |
Losses on deferred cash flows, net | 3 |  |  |  |  |  |  |  |  |  |  |  |
Unamortized debt issuance expense | 1 |  |  |  |  |  | 1 |  |  |  |  |  |
Make-whole premium, net | $ 63 |  |  |  |  |  | $ 63 |  |  |  |  |  |
4.70% Secured Senior Notes Maturing 2024 | Unsecured Notes | JCP&L |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate | 4.70% |  |  |  |  |  | 4.70% |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  | $ 500 |  |  |  |  |  |
4.10% Secured Senior Notes Maturing 2024 | First Mortgage Bond | MP |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate | 4.10% |  |  |  |  |  | 4.10% |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  | $ 400 |  |  |  |  |  |
5.50% Unsecured Senior Notes Maturing 2024 | First Mortgage Bond | CEI |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate |  |  |  |  | 5.50% |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  | $ 300 |  |  |  |  |  |  |  |
4.00% Unsecured Senior Notes Maturing 2025 | Unsecured Notes | FE PA |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate |  | 4.00% |  |  |  |  |  |  | 4.00% |  |  |  |
Repayments of debt |  | $ 250 |  |  |  |  |  |  |  |  |  |  |
4.15% Unsecured Senior Notes Maturing 2025 | Unsecured Notes | FE PA |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate |  | 4.15% |  |  |  |  |  |  | 4.15% |  |  |  |
Repayments of debt |  | $ 200 |  |  |  |  |  |  |  |  |  |  |
4.35% Unsecured Senior Notes Maturing 2025 | Unsecured Notes | FET |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate |  | 4.35% |  | 4.35% |  |  |  |  | 4.35% |  |  |  |
Repayments of debt |  | $ 600 |  | $ 600 |  |  |  |  |  |  |  |  |
5.63% Secured Senior Notes Maturing 2034 | Unsecured Notes | ATSI |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate |  |  |  |  |  |  |  | 5.63% |  |  |  |  |
Debt issuances |  |  |  |  |  |  |  | $ 150 |  |  |  |  |
5.94% Secured Senior Notes Maturing 2031 | Unsecured Notes | MAIT |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate |  |  |  |  |  | 5.94% |  |  |  |  |  |  |
Debt issuances |  |  |  |  |  | $ 250 |  |  |  |  |  |  |
4.55% Unsecured Senior Notes Maturing 2031 | Unsecured Notes | FET |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate |  |  |  | 4.55% |  |  |  |  |  |  |  |  |
Face amount of loan |  |  |  |  |  |  |  |  |  |  |  |  | $ 400
Debt issuances |  |  |  | $ 400 |  |  |  |  |  |  |  |  |
5.15%, 300 Million Notes Maturing 2026 | Unsecured Notes | FET |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate |  |  |  | 5.00% |  |  |  |  |  |  |  |  |
Debt issuances |  |  |  | $ 400 |  |  |  |  |  |  |  |  |
5.15%, 300 Million Notes Maturing 2026 | Senior Notes | FET |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Face amount of loan |  |  |  |  |  |  |  |  |  |  |  |  | $ 400
5.17% Unsecured Senior Notes Maturing 2035 | Unsecured Notes | KATCo |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate |  |  | 5.17% |  |  |  |  |  |  |  |  |  |
Debt issuances |  |  | $ 200 |  |  |  |  |  |  |  |  |  |
5.10% Unsecured Senior Notes Maturing 2035 | Unsecured Notes | JCP&L |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |
Issuance interest rate |  | 5.10% |  |  |  |  |  |  | 5.10% |  |  |  |
Face amount of loan |  |  |  |  |  |  |  |  |  |  |  | $ 700 |
Debt issuances |  | $ 700 |  |  |  |  |  |  |  |  |  |  |

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