XML 1114 R89.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Commitments and Contingencies Commitments and Contingencies - Environmental Matters and Financial Assurances (Details) $ in Millions |  |  | 12 Months Ended
--- | --- | --- | ---
Jun. 13, 2017 USD ($) | Jul. 06, 2016 guarantee | Dec. 31, 2017 USD ($)
Payment Guarantee |  |  |
Financial Assurances |  |  |
Number of parental guarantees | guarantee |  | 4 |
Letter of credit | ARIZONA PUBLIC SERVICE COMPANY |  |  |
Financial Assurances |  |  |
Outstanding letters of credit |  |  | $ 5
Equity Lessors Sale Leaseback Letter of Credit | ARIZONA PUBLIC SERVICE COMPANY |  |  |
Financial Assurances |  |  |
Outstanding letters of credit |  |  | 62
Four Corners | NTEC |  |  |
Environmental Matters [Abstract] |  |  |
Option to purchase, ownership interest (as a percent) |  | 7.00% |
Four Corners | 4CA |  |  |
Environmental Matters [Abstract] |  |  |
Percentage share cost of control |  | 7.00% |
Four Corners | Coal Supply Agreement Arbitration |  |  |
Environmental Matters [Abstract] |  |  |
Damages sought | $ 30 |  |
Four Corners | Coal Supply Agreement Arbitration | ARIZONA PUBLIC SERVICE COMPANY |  |  |
Environmental Matters [Abstract] |  |  |
Damages sought | $ 17 |  |
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] |  |  |
Payment received for coal supply agreement |  |  | 10
Operating and maintenance cost reimbursement receivable |  |  | 20
Regional Haze Rules | Navajo Generating Station | ARIZONA PUBLIC SERVICE COMPANY |  |  |
Environmental Matters [Abstract] |  |  |
Expected environmental cost |  |  | $ 200
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
Regional Haze Rules | Four Corners Units 4 and 5 | Four Corners | ARIZONA PUBLIC SERVICE COMPANY |  |  |
Environmental Matters [Abstract] |  |  |
Additional expected environment cost |  |  | $ 45
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
Coal Combustion Waste | Navajo Generating Station | ARIZONA PUBLIC SERVICE COMPANY |  |  |
Environmental Matters [Abstract] |  |  |
Additional expected environment cost |  |  | 1
Coal Combustion Waste | Minimum | Cholla | ARIZONA PUBLIC SERVICE COMPANY |  |  |
Environmental Matters [Abstract] |  |  |
Additional expected environment cost |  |  | $ 20
El Paso's Interest in Four Corners | 4CA |  |  |
Financial Assurances |  |  |
Ownership interest acquired (as a percent) |  | 7.00% | 7.00%

X
- Definition Asset Purchase Agreement, Additional Percentage Share of Cost of Control + References No definition available. + Details
Name: | pnw_AssetPurchaseAgreementAdditionalPercentageShareofCostofControl
Namespace Prefix: | pnw_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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. + Details
Name: | pnw_AssetPurchaseAgreementProceedsfromOperatinganMaintenanceCostReimbursement
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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. + Details
Name: | pnw_EnvironmentalMattersAbstract
Namespace Prefix: | pnw_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | pnw_FinancialAssurancesAbstract
Namespace Prefix: | pnw_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Guarantor Obligations, Number of Parental Guarantees + References No definition available. + Details
Name: | pnw_GuarantorObligationsNumberofParentalGuarantees
Namespace Prefix: | pnw_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the percentage of share of the cost of control acquired by the entity. + References No definition available. + Details
Name: | pnw_PercentageOfShareOfCostOfControl
Namespace Prefix: | pnw_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of voting equity interests acquired at the acquisition date in the business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
Name: | us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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 The value (monetary amount) of the award the plaintiff seeks in the legal matter. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14557-108349 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349 + Details
Name: | us-gaap_LossContingencyDamagesSoughtValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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://www.xbrl.org/2003/role/presentationRef -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=d3e13237-110859 + Details
Name: | us-gaap_SiteContingencyLossExposureNotAccruedBestEstimate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_PaymentGuaranteeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_CreditFacilityAxis=pnw_EquityLessorsSaleLeasebackLetterOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

X
- Details
Name: | dei_LegalEntityAxis=pnw_A4CAcquisitionLLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_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
- Details
Name: | us-gaap_EnvironmentalRemediationSiteAxis=pnw_NavajoGeneratingStationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_JointlyOwnedUtilityPlantAxis=pnw_FourCornersUnits4And5Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_CreditFacilityAxis=pnw_NaturalGasTollingLetterOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EnvironmentalRemediationContingencyAxis=pnw_CoalCombustionWasteMember
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_EnvironmentalRemediationSiteAxis=pnw_ChollaMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=pnw_ElPasosInterestinFourCornersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |