XML 71 R60.htm IDEA: XBRL DOCUMENT
v3.3.0.814

Fair Value Measurements - Significant Unobservable Inputs Used to Value Level 3 Instruments (Details 2) $ in Millions | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2015 USD ($) $ / MMBTU $ / MWh | Dec. 31, 2014 USD ($) $ / MMBTU $ / MWh
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments |  |
Assets | $ 29 | $ 33
Liabilities | 70 | 74
Electricity forward contracts |  |
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments |  |
Assets | 27 | 30
Liabilities | $ 56 | $ 56
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 | 17.37 | 19.51
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 | 40.62 | 56.72
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 | 28.25 | 35.27
Option Contracts |  |
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments |  |
Assets | $ 0 | $ 0
Liabilities | $ 7 | $ 15
Option Contracts | Minimum | Option model |  |
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments |  |
Electricity forward price (per MWh) | $ / MWh | 28.36 | 32.14
Electricity price volatilities (as a percent) | 48.00% | 23.00%
Natural gas price volatilities (as a percent) | 30.00% | 23.00%
Natural gas forward price (per MMbtu) | $ / MMBTU |  | 3.18
Option Contracts | Maximum | Option model |  |
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments |  |
Electricity forward price (per MWh) | $ / MWh | 46.50 | 66.09
Electricity price volatilities (as a percent) | 61.00% | 63.00%
Natural gas price volatilities (as a percent) | 47.00% | 41.00%
Natural gas forward price (per MMbtu) | $ / MMBTU |  | 3.29
Option Contracts | Weighted Average | Option model |  |
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments |  |
Electricity forward price (per MWh) | $ / MWh | 35.55 | 45.83
Electricity price volatilities (as a percent) | 55.00% | 41.00%
Natural gas price volatilities (as a percent) | 34.00% | 31.00%
Natural gas forward price (per MMbtu) | $ / MMBTU |  | 3.25
Natural gas forward contracts |  |
Information regarding the entity's internally developed significant unobservable inputs used to value its level 3 instruments |  |
Assets | $ 2 | $ 3
Liabilities | $ 7 | $ 3
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 | 2.32 | 2.98
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 | 3.17 | 4.13
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 |  |
Natural gas forward price (per MMbtu) | $ / MMBTU | 2.73 | 3.45

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 Represents the percentage of implied electricity volatilities. + References No definition available. + Details
Name: | pnw_FairValueInputsImpliedElectricityVolatilities
Namespace Prefix: | pnw_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the percentage of implied electricity natural gas price volatilities. + References No definition available. + Details
Name: | pnw_FairValueInputsImpliedGasPriceVolatilities
Namespace Prefix: | pnw_
Data Type: | num:percentItemType
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=36462937&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=36462937&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=us-gaap_CommodityOptionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ValuationTechniqueAxis=pnw_OptionModelValuationTechniqueMember
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: |