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ACQUISITIONS AND DISPOSITIONS - Schedule of Construction Projects (Details) - Southern Power $ in Millions | 1 Months Ended | 5 Months Ended | 7 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Nov. 30, 2021 MW | Dec. 31, 2020 | Nov. 30, 2020 USD ($) MW | Jun. 30, 2020 USD ($) | May 31, 2020 MW | Mar. 31, 2022 MW | Mar. 31, 2022 MW | Dec. 31, 2021 | Dec. 31, 2019 | Dec. 31, 2018
Tranquility Solar Storage |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Nameplate capacity placed in service (in MWs) | 32 |  |  |  |  |  |  |  |  |
Tranquility Solar Storage | Scenario, Forecast |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Approximate Nameplate Capacity (MW) |  |  |  |  |  | 72 | 72 |  |  |
PPA Contract Period |  |  |  |  |  | 20 years |  |  |  |
Garland Solar Storage | Scenario, Forecast |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Approximate Nameplate Capacity (MW) |  |  |  |  |  | 88 | 88 |  |  |
PPA Contract Period |  |  |  |  |  |  | 20 years |  |  |
Glass Sands |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Approximate Nameplate Capacity (MW) | 118 |  |  |  |  |  |  |  |  |
PPA Contract Period | 12 years |  |  |  |  |  |  |  |  |
Skookumchuck |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Approximate Nameplate Capacity (MW) |  |  | 136 |  |  |  |  |  |  |
PPA Contract Period |  |  | 20 years |  |  |  |  |  |  |
Reading |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Approximate Nameplate Capacity (MW) |  |  |  |  | 200 |  |  |  |  |
PPA Contract Period |  |  |  |  | 12 years |  |  |  |  |
Tranquility Solar Storage | Class B Membership Interest | Tranquility Solar Storage |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Noncontrolling ownership percentage sold by parent |  | 100.00% |  |  |  |  |  |  |  |
Garland Solar Storage | Class B Membership Interest | Garland Solar Storage |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Noncontrolling ownership percentage sold by parent |  | 100.00% |  |  |  |  |  |  |  |
Glass Sands | Glass Sands |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Noncontrolling ownership percentage held by parent |  | 100.00% |  |  |  |  |  |  |  |
Skookumchuck | Skookumchuck |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Noncontrolling ownership percentage held by parent |  |  |  |  |  |  |  |  | 100.00% |
Proceeds from tax equity transaction | $ |  |  | $ 121 |  |  |  |  |  |  |
Skookumchuck | Class B Membership Interest | Skookumchuck |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Noncontrolling ownership percentage held by parent |  |  | 100.00% |  |  |  |  |  |  |
Reading | Reading |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Noncontrolling ownership percentage held by parent |  |  |  |  |  |  |  |  |  | 100.00%
Proceeds from tax equity transaction | $ |  |  |  | $ 156 |  |  |  |  |  |
Reading | Class B Membership Interest | Reading |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |
Noncontrolling ownership percentage held by parent |  |  |  |  |  |  |  | 100.00% |  |

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