XML 24 R55.htm IDEA: XBRL DOCUMENT
v3.3.0.814

Commitments and Contingencies - Superfund-Related Matters, Southwest Power Outage and Clean Air Act (Details) $ in Millions |  |  |  | 9 Months Ended
--- | --- | --- | --- | ---
Jun. 24, 2015 USD ($) power_plant | Aug. 06, 2013 Defendant | Sep. 08, 2011 kV Customer | Sep. 30, 2015 USD ($)
Arizona Public Service Company |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Capacity of transmission line that tripped out of service (in kV) | kV |  |  | 500 |
Period, after the transmission line went off-line, over which generation and transmission resources for the Yuma area were lost |  |  | 10 minutes |
Number of customers losing service in Yuma area | Customer |  |  | 69,700 |
Arizona Public Service Company | Contaminated groundwater wells |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Costs related to investigation and study under Superfund site |  |  |  | $ 2.0
Number of defendants against whom Roosevelt Irrigation District (RID) filed lawsuit | Defendant |  | 24 |  |
Arizona Public Service Company | Clean Air Act Citizen Lawsuit |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Number of power plants in lawsuit | power_plant | 2 |  |  |
Litigation settlement percent | 15.00% |  |  |
Four Corners | Clean Air Act Citizen Lawsuit |  |  |  |
Loss Contingencies [Line Items] |  |  |  |
Civil penalty amount | $ 1.5 |  |  |
Environmental mitigation project cost | $ 6.2 |  |  |

X
- Definition Costs related to site-wide groundwater remedial investigation and feasibility study work plan because subsidiary has been found to be potentially responsible parties ("PRPs") with liability for cleanup of hazardous substances that contaminates the soil, water or air, under the Comprehensive Environmental Response, Compensation and Liability Act ("Superfund"). + References No definition available. + Details
Name: | pnw_CostsRelatedToInvestigationAndStudyUnderSuperfundSite
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Litigation Settlement, Percent of Settlement + References No definition available. + Details
Name: | pnw_LitigationSettlementPercentofSettlement
Namespace Prefix: | pnw_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Loss Contingency, Civil Penalty Amount + References No definition available. + Details
Name: | pnw_LossContingencyCivilPenaltyAmount
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Loss Contingency, Environmental Mitigation Project Cost + References No definition available. + Details
Name: | pnw_LossContingencyEnvironmentalMitigationProjectCost
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Loss Contingency, Number of Units + References No definition available. + Details
Name: | pnw_LossContingencyNumberofUnits
Namespace Prefix: | pnw_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Power Outage Capacity of Transmission Line that Tripped out of Service + References No definition available. + Details
Name: | pnw_PowerOutageCapacityofTransmissionLinethatTrippedoutofService
Namespace Prefix: | pnw_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of customers losing service after the generation and transmission resources were lost in the power outage. + References No definition available. + Details
Name: | pnw_PowerOutageNumberOfCustomersLosingService
Namespace Prefix: | pnw_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the period, after the transmission line went off-line, until the generation and transmission resources were lost in the power outage. + References No definition available. + Details
Name: | pnw_PowerOutagePeriodOverWhichGenerationAndTransmissionResourcesWereLost
Namespace Prefix: | pnw_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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_LossContingenciesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of defendants named in a legal action. + References No definition available. + Details
Name: | us-gaap_LossContingencyNumberOfDefendants
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=pnw_ArizonaPublicServiceCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LossContingenciesByNatureOfContingencyAxis=pnw_ContaminatedGroundwaterWellsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LitigationCaseAxis=pnw_CleanAirActCitizenLawsuitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=pnw_FourCornersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |