| **Fair Value Measurements - Level 3 Quantitative Information (Details) $ in Thousands**                                           | 12 Months Ended |
|-----------------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| **Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments** |            |   |
| Assets                                                                                                                            | $ 1,036         | $ 11,076 |
| Liabilities                                                                                                                       | 19,292          | 58,482 |
| Electricity forward contracts                                                                                                     |            |   |
| **Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments** |            |   |
| Assets                                                                                                                            | 21              | 10,648 |
| Liabilities                                                                                                                       | $ 15,485        | $ 32,042 |
| Electricity forward contracts | Minimum | Discounted cash flows                                                                   |            |   |
| **Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments** |            |   |
| Electricity forward price (per MWh) | $ / MWh                                                                                     | 18.51           | 16.43 |
| Electricity forward contracts | Maximum | Discounted cash flows                                                                   |            |   |
| **Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments** |            |   |
| Electricity forward price (per MWh) | $ / MWh                                                                                     | 38.75           | 41.07 |
| Electricity forward contracts | Weighted Average | Discounted cash flows                                                          |            |   |
| **Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments** |            |   |
| Electricity forward price (per MWh) | $ / MWh                                                                                     | 27.89           | 29.86 |
| Natural gas forward contracts                                                                                                     |            |   |
| **Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments** |            |   |
| Assets                                                                                                                            | $ 1,015         | $ 428 |
| Liabilities                                                                                                                       | $ 3,807         | $ 26,440 |
| Natural gas forward contracts | Minimum | Discounted cash flows                                                                   |            |   |
| **Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments** |            |   |
| Natural gas forward price (per MMbtu) | $ / MMBTU                                                                                 | 2.33            | 2.32 |
| Natural gas forward contracts | Maximum | Discounted cash flows                                                                   |            |   |
| **Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments** |            |   |
| Natural gas forward price (per MMbtu) | $ / MMBTU                                                                                 | 3.11            | 3.60 |
| Natural gas forward contracts | Weighted Average | Discounted cash flows                                                          |            |   |
| **Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments** |            |   |
| Electricity forward price (per MWh) | $ / MWh                                                                                     | 2.71            |   |
| Natural gas forward price (per MMbtu) | $ / MMBTU                                                                                 |            | 2.81 |

| X                                                                                                                                                                                                                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Represents the electricity forward price per Megawatt Hours, used as an input to measure fair value.
+ References
No definition available.
+ Details**Name:**pnw_FairValueInputsElectricityForwardPricePerMegawattHours**Namespace Prefix:**pnw_**Data Type:**us-types:perUnitItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Represents the gas price per Metric Million British Thermal Units, used as an input to measure fair value.
+ References
No definition available.
+ Details**Name:**pnw_FairValueInputsGasForwardPricePerMetricMillionBritishThermalUnits**Namespace Prefix:**pnw_**Data Type:**us-types:perUnitItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258
+ Details**Name:**us-gaap_AssetsFairValueDisclosure**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
+ Details**Name:**us-gaap_FairValueInputsLiabilitiesQuantitativeInformationLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value of financial and nonfinancial obligations.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258
+ Details**Name:**us-gaap_LiabilitiesFairValueDisclosure**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FairValueByLiabilityClassAxis=pnw_ElectricityContractsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RangeAxis=us-gaap_MinimumMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_ValuationTechniqueAxis=us-gaap_MarketApproachValuationTechniqueMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RangeAxis=us-gaap_MaximumMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                       |
|-----------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_RangeAxis=us-gaap_WeightedAverageMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FairValueByLiabilityClassAxis=pnw_NaturalGasContractsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |