| **Commitments and Contingencies - Environmental Matters and Financial Assurances (Details) - USD ($) $ in Millions**     |        |        | 12 Months Ended |
|--------------------------------------------------------------------------------------------------------------------------|--------|--------|-----------------|
||
| **Financial Assurances**                                                                                                 |   |   |            |
| Equity contribution guarantees                                                                                           |   |   | $ 40.0          |
| Letter of credit | ARIZONA PUBLIC SERVICE COMPANY                                                                        |   |   |            |
| **Financial Assurances**                                                                                                 |   |   |            |
| Outstanding letters of credit                                                                                            |   |   | 1.7             |
| Four Corners | NTEC                                                                                                      |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Option to purchase, ownership interest (as a percent)                                                                    | 7.00%  | 7.00%  |            |
| Payment received for coal supply agreement                                                                               | $ 70.0 |   |            |
| Four Corners | 4CA                                                                                                       |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Percentage share cost of control                                                                                         |   | 7.00%  |            |
| Four Corners | Coal Supply Agreement Arbitration | NTEC                                                                  |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Option to purchase, ownership interest (as a percent)                                                                    |   | 7.00%  |            |
| Four Corners | Coal Supply Agreement Arbitration | 4CA                                                                   |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Asset purchase agreement                                                                                                 |   |   | $ 10.0          |
| Regional Haze Rules | Four Corners Units 4 and 5 | ARIZONA PUBLIC SERVICE COMPANY                                        |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Percentage share cost of control                                                                                         |   |   | 63.00%          |
| Expected environmental cost                                                                                              |   |   | $ 400.0         |
| Regional Haze Rules | Four Corners Units 4 and 5 | Four Corners | ARIZONA PUBLIC SERVICE COMPANY                         |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Additional expected environment cost                                                                                     |   |   | $ 45.0          |
| Regional Haze Rules | Four Corners Units 4 and 5 | Natural Gas Tolling Letter of Credit | ARIZONA PUBLIC SERVICE COMPANY |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Additional percentage share of cost of control                                                                           |   |   | 7.00%           |
| Coal Combustion Waste | Four Corners | ARIZONA PUBLIC SERVICE COMPANY                                                    |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Additional expected environment cost                                                                                     |   |   | $ 22.0          |
| Coal Combustion Waste | Navajo Generating Station | ARIZONA PUBLIC SERVICE COMPANY                                       |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Additional expected environment cost                                                                                     |   |   | 1.0             |
| Coal Combustion Waste | Minimum | Cholla | ARIZONA PUBLIC SERVICE COMPANY                                                |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Additional expected environment cost                                                                                     |   |   | 15.0            |
| Coal Combustion Waste | Minimum | Cholla and Four Corners | ARIZONA PUBLIC SERVICE COMPANY                               |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Additional expected environment cost                                                                                     |   |   | 10.0            |
| Coal Combustion Waste | Maximum | Cholla and Four Corners | ARIZONA PUBLIC SERVICE COMPANY                               |   |   |            |
| **Environmental Matters [Abstract]**                                                                                     |   |   |            |
| Additional expected environment cost                                                                                     |   |   | 15.0            |
| Surety Bonds Expiring in 2020 | ARIZONA PUBLIC SERVICE COMPANY                                                           |   |   |            |
| **Financial Assurances**                                                                                                 |   |   |            |
| Surety bonds expiring, amount                                                                                            |   |   | $ 14.0          |

| X                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Asset Purchase Agreement, Additional Percentage Share of Cost of Control
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Asset Purchase Agreement, Operating and Maintenance Cost Reimbursement Receivable
+ References
No definition available.
+ Details**Name:**pnw_AssetPurchaseAgreementOperatingandMaintenanceCostReimbursementReceivable**Namespace Prefix:**pnw_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Asset Purchase Agreement, Option to Purchase, Ownership Interest, Percentage
+ References
No definition available.
+ Details**Name:**pnw_AssetPurchaseAgreementOptiontoPurchaseOwnershipInterestPercentage**Namespace Prefix:**pnw_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Asset Purchase Agreement, Proceeds from Operating an Maintenance Cost Reimbursement
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Asset Purchase Agreement, Site Contingency, Increase in Loss Exposure Not Accrued, Best Estimate
+ References
No definition available.
+ Details**Name:**pnw_AssetPurchaseAgreementSiteContingencyIncreaseinLossExposureNotAccruedBestEstimate**Namespace Prefix:**pnw_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Environmental Matters [Abstract]
+ References
No definition available.
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| X                                                                                                                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Equity Contribution Guarantees
+ References
No definition available.
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| X                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
No definition available.
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| X                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Represents the percentage of share of the cost of control acquired by the entity.
+ References
No definition available.
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| X                                                                                                                                                                                                                                          |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Surety Bonds Expiring, Amount
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.
+ References
No definition available.
+ Details**Name:**us-gaap_LettersOfCreditOutstandingAmount**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Best estimate of the loss exposure for reasonably possible environmental contingencies at an individual site for which no accrual has been recorded.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 10 -Subparagraph (c),(d)(2) -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 10 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859
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| X                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                  |
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| X                                                                                                                                                        |
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| X                                                                                                                                       |
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| - Details**Name:**dei_LegalEntityAxis=pnw_A4CAcquisitionLLCMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**srt_LitigationCaseAxis=pnw_CoalSupplyAgreementArbitrationMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_EnvironmentalRemediationContingencyAxis=pnw_RegionalHazeRulesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_EnvironmentalRemediationSiteAxis=pnw_NavajoGeneratingStationMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                 |
|---------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_EnvironmentalRemediationSiteAxis=pnw_ChollaandFourCornersMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                      |
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