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Regulatory Matters - Four Corners, Cholla and Navajo Plant (Details) - APS - USD ($) $ in Millions |  | 1 Months Ended | 3 Months Ended |
--- | --- | --- | --- | ---
Nov. 02, 2021 | Sep. 30, 2018 | Apr. 30, 2018 | Mar. 31, 2022 | Aug. 02, 2021
Navajo Nation, Economic Development Organization | Coal Community Transition Plan | Retail Rate Case Filing with Arizona Corporation Commission | ACC |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Disallowance of annual amortization percentage |  |  |  |  | 15.00%
SCE | Four Corners Units 4 and 5 |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Settlement agreement, ACC approved rate adjustment, annualized customer impact |  | $ 58.5 | $ 67.5 |  |
Disallowance of plant investments | $ 194.0 |  |  |  |
Cost deferrals | $ 215.5 |  |  |  |
Amount not recoverable |  |  |  | $ 154.4 |
Retired power plant costs |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Net book value |  |  |  | 40.6 |
Navajo Plant |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Net book value |  |  |  | 59.8 |
Navajo Plant, Coal Reclamation Regulatory Asset |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Net book value |  |  |  | $ 16.1 |

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