| **Regulatory Matters - Capital Structure and Costs of Capital (Details) - APS - $ / kWh** | Oct. 01, 2021 | May 01, 2020 | Oct. 31, 2019 | May 01, 2019 |
|-------------------------------------------------------------------------------------------|---------------|--------------|---------------|--------------|
| **Cost of Capital**                                                             |          |         |          |         |
| Long-term debt                                                                            |          |         | 4.10%         |         |
| Common stock equity                                                                       |          |         | 10.15%        |         |
| Weighted-average cost of capital                                                          |          |         | 7.41%         |         |
| Retail Rate Case Filing with Arizona Corporation Commission                               |          |         |          |         |
| **Capital Structure**                                                                |          |         |          |         |
| Common stock equity                                                                       |          |         | 54.70%        |         |
| Retail Rate Case Filing with Arizona Corporation Commission | ACC                         |          |         |          |         |
| **Capital Structure**                                                                |          |         |          |         |
| Long-term debt                                                                            |          |         | 45.30%        |         |
| Net Metering | ACC                                                                        |          |         |          |         |
| **Cost of Capital**                                                             |          |         |          |         |
| Second-year export energy price (in dollars per kWh)                                      | 0.094         | 0.094        |          | 0.105        |

| X                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Capital Structure [Abstract]
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| X                                                                                                                                                                                                                               |
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| - Definition
Cost Of Capital [Abstract]
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| X                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Public Utilities, Requested Equity Cost Of Capital, Percentage
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Public Utilities, Requested Long-term Debt Cost Of Capital, Percentage
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                           |
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| - Definition
Public Utilities, Requested Weighted Average Cost Of Capital, Percentage
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                               |
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| - Definition
Rate Matter, Request Second-Year Energy Price for Exported Energy1
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                                       |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of public utility's requested debt to capital, including debt and equity.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Percentage of public utility's requested equity to capital, including debt and equity.
+ References
No definition available.
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| X                                                                                                                                                 |
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