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ACQUISITIONS - THUNDERHEAD (Details) - Thunderhead - WECI $ in Millions | 1 Months Ended | 9 Months Ended
--- | --- | ---
Feb. 29, 2020 USD ($) | Aug. 31, 2019 USD ($) MW | Sep. 30, 2021
Asset Acquisition [Line Items] |  |  |
Ownership interest of wind generating facility acquired |  | 80.00% |
Capacity of generation unit | MW |  | 300 |
Acquisition purchase price, expected | $ | $ 43.0 | $ 338.0 |
Additional ownership interest acquired | 10.00% |  |
Duration of offtake agreement for the sale of energy produced |  |  | 12 years

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