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Regulation - Nature of Regulation Schedule (Details) - company |  |  |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | ---
Sep. 30, 2024 | Feb. 01, 2024 | Sep. 01, 2023 | Oct. 31, 2024 | Jul. 31, 2024 | Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
ITC |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Approved cost-based formula, annual true-up (period) |  |  |  |  |  |  | 2 years |
FortisOntario |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Number of utilities |  |  |  |  |  |  | 3 |
Franchise agreement term |  |  |  |  |  |  | 35 years |
FortisOntario | Electric Utilities, Following COS Regulation |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Number of utilities |  |  |  |  |  |  | 2 |
Fortis Turks and Caicos |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Number of utilities |  |  |  |  |  |  | 2 |
FERC | ITC |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  |  |  |  |  |  | 60.00% |
Allowed ROE (percent) | 10.02% |  |  | 9.98% |  |  | 10.73% | 10.77%
Allowed ROE, incentive adders (percent) |  |  |  | 0.75% |  |  |  |
Approved cost-based formula, annual true-up (period) |  |  |  |  |  |  | 2 years |
FERC | ITC | Maximum |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed ROE (percent) |  |  |  | 12.58% |  |  |  |
FERC | TEP |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed ROE (percent) |  |  |  |  |  |  | 9.79% | 9.79%
ACC | TEP |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  |  | 54.30% |  |  |  | 54.30% |
Allowed ROE (percent) |  |  | 9.55% |  |  |  | 9.55% | 9.55%
ACC | UNS Electric |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  | 53.70% |  |  |  |  | 53.70% |
Allowed ROE (percent) |  | 9.75% |  |  |  |  | 9.75% | 9.50%
ACC | UNS Gas |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  |  |  |  |  |  | 50.80% |
Allowed ROE (percent) |  |  |  |  |  |  | 9.75% | 9.75%
PSC | Central Hudson |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  |  |  |  |  |  | 48.00% |
Allowed ROE (percent) |  |  |  |  |  |  | 9.50% | 9.00%
PSC | Central Hudson | General rate application |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed ROE (percent) |  |  |  |  | 9.50% |  |  |
BCUC | FortisBC Energy |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  |  |  |  |  |  | 45.00% |
Allowed ROE (percent) |  |  |  |  |  |  | 9.65% | 9.65%
BCUC | FortisBC Electric |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  |  |  |  |  |  | 41.00% |
Allowed ROE (percent) |  |  |  |  |  |  | 9.65% | 9.65%
AUC | FortisAlberta |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  |  |  |  |  |  | 37.00% |
Allowed ROE (percent) |  |  |  |  |  |  | 9.28% | 8.50%
AUC | FortisAlberta | Forecast |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed ROE (percent) |  |  |  |  |  | 8.97% |  |
Newfoundland and Labrador Board of Commissioners of Public Utilities | Newfoundland Power |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  |  |  |  |  |  | 45.00% |
Allowed ROE (percent) |  |  |  |  |  |  | 8.50% | 8.50%
Island Regulatory and Appeals Commission | Maritime Electric |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  |  |  |  |  |  | 40.00% |
Allowed ROE (percent) |  |  |  |  |  |  | 9.35% | 9.35%
Ontario Energy Board | FortisOntario |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed common equity |  |  |  |  |  |  | 40.00% |
Ontario Energy Board | FortisOntario | Minimum |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed ROE (percent) |  |  |  |  |  |  | 8.52% | 8.52%
Ontario Energy Board | FortisOntario | Maximum |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed ROE (percent) |  |  |  |  |  |  | 9.30% | 9.30%
Utility Regulation and Competition Office | Caribbean Utilities |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Transmission and distribution license period |  |  |  |  |  |  | 20 years |
Non-exclusive generation license period |  |  |  |  |  |  | 25 years |
Utility Regulation and Competition Office | Caribbean Utilities | Minimum |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed ROA (percent) |  |  |  |  |  |  | 8.25% | 7.50%
Utility Regulation and Competition Office | Caribbean Utilities | Maximum |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed ROA (percent) |  |  |  |  |  |  | 10.25% | 9.50%
Government of the Turks and Caicos Islands | Fortis Turks and Caicos | Minimum |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed ROA (percent) |  |  |  |  |  |  | 15.00% | 15.00%
License period |  |  |  |  |  |  | 25 years |
Government of the Turks and Caicos Islands | Fortis Turks and Caicos | Maximum |  |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |  |
Allowed ROA (percent) |  |  |  |  |  |  | 17.50% | 17.50%
License period |  |  |  |  |  |  | 50 years |

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