| **Asset Retirement Obligations (Details) $ in Thousands**              | 12 Months Ended |
|------------------------------------------------------------------------|-----------------|
||
| ARIZONA PUBLIC SERVICE COMPANY                                         |            |   |
| **Change in asset retirement obligations**                             |            |   |
| Asset retirement obligations at the beginning of year                  | $ 624,475       | $ 443,576 |
| **Changes attributable to:**                                           |            |   |
| Accretion expense                                                      | 33,104          | 26,656 |
| Settlements                                                            | 0               | (15,732) |
| Estimated cash flow revisions                                          | 21,950          | 151,046 |
| Newly incurred or acquired obligations                                 | 0               | 18,929 |
| Asset retirement obligations at the end of year                        | 679,529         | $ 624,475 |
| Navajo Generating Station | ARIZONA PUBLIC SERVICE COMPANY             |            |   |
| **Asset Retirement Obligations**                                       |            |   |
| Increase in regulatory asset                                           | 2,000           |   |
| Decrease in regulatory liability                                       | 20,000          |   |
| **Changes attributable to:**                                           |            |   |
| Newly incurred or acquired obligations                                 | $ 22,000        |   |
| Ocotillo Steam Units | ARIZONA PUBLIC SERVICE COMPANY                  |            |   |
| **Asset Retirement Obligations**                                       |            |   |
| Number of constructed turbine units | turbine_unit                     |            | 5 |
| **Changes attributable to:**                                           |            |   |
| Newly incurred or acquired obligations                                 |            | $ 10,000 |
| El Paso's Share of Four Corners Units 4 & 5 | 4CA                  |            |   |
| **Changes attributable to:**                                           |            |   |
| Newly incurred or acquired obligations                                 |            | 9,000 |
| Four Corners | ARIZONA PUBLIC SERVICE COMPANY                          |            |   |
| **Changes attributable to:**                                           |            |   |
| Settlements                                                            |            | (16,000) |
| Palo Verde Nuclear Generating Station | ARIZONA PUBLIC SERVICE COMPANY |            |   |
| **Asset Retirement Obligations**                                       |            |   |
| Decrease in regulatory liability                                       |            | 20,000 |
| Increase in plant services                                             |            | 131,000 |
| **Changes attributable to:**                                           |            |   |
| Estimated cash flow revisions                                          |            | $ 151,000 |

| X                                                                                                                                                                                                                                                                                                |
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Asset Retirement Obligation, Increase in Regulatory Asset
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Property, Plant and Equipment, Number of Constructed Turbine Units
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| - Definition
The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.
+ References
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| - Definition
Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.
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| - Definition
Amount of asset retirement obligations incurred during the period.
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| - Definition
Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.
+ References
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| - Definition
Amount of increase (decrease) in the asset retirement obligation from changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.
+ References
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| - Definition
A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.
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