XML 58 R41.htm IDEA: XBRL DOCUMENT
v3.4.0.3

Retirement Plans and Other Postretirement Benefits - Narrative (Details) - USD ($) |  | 1 Months Ended | 3 Months Ended
--- | --- | --- | ---
Sep. 30, 2014 | Jul. 31, 2012 | Mar. 31, 2016 | Mar. 31, 2015
Regulatory Assets |  |  |  |
Regulatory asset amortization period |  | 3 years |  |
Amortization of regulatory asset |  |  |  | $ 2,000,000
Pension Benefits |  |  |  |
Contributions |  |  |  |
Voluntary employer contributions to pension plan |  |  | $ 60,000,000 |
Minimum employer contributions for the next three years |  |  | 0 |
Maximum employer contributions for the next two years (up to) |  |  | 300,000,000 |
Other Benefits |  |  |  |
Other Postretirement Benefit Plan Remeasurement |  |  |  |
Other postretirement plan benefit remeasurement, amount seeking approval to move to separate account to Pay Union employee medical costs | $ 140,000,000 |  |  |
Contributions |  |  |  |
2016 (up to) |  |  | 1,000,000 |
2017 (up to) |  |  | 1,000,000 |
2015 |  |  | $ 1,000,000 |

X
- Definition Defined Benefit Plan, Amount Seeking Approval to Move to Separate Account to Pay Union Employee Medical Costs + References No definition available. + Details
Name: | pnw_DefinedBenefitPlanAmountSeekingApprovaltoMovetoSeparateAccounttoPayUnionEmployeeMedicalCosts
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Definition Defined Benefit Plan Estimated Future Employer Contributions in Year Two + References No definition available. + Details
Name: | pnw_DefinedBenefitPlanEstimatedFutureEmployerContributionsinYearTwo
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Defined Benefit Plans Estimated Future Employer Contributions in Year Three + References No definition available. + Details
Name: | pnw_DefinedBenefitPlansEstimatedFutureEmployerContributionsinYearThree
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Defined Benefit Plans Estimated Maximum Future Employer Contributions, Next Three Fiscal Years + References No definition available. + Details
Name: | pnw_DefinedBenefitPlansEstimatedMaximumFutureEmployerContributionsNextThreeFiscalYears
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Defined Benefit Plans Estimated Minimum Future Employer Contributions, Next Three Fiscal Years + References No definition available. + Details
Name: | pnw_DefinedBenefitPlansEstimatedMinimumFutureEmployerContributionsNextThreeFiscalYears
Namespace Prefix: | pnw_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The expense charged against earnings during the period to allocate the capitalized costs of regulatory assets over the periods expected to benefit from such costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.3) -URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688 + Details
Name: | us-gaap_AmortizationOfRegulatoryAsset
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of contributions made by the employer to defined benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(ii) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 35 -Paragraph 123 -Subparagraph B -URI http://asc.fasb.org/extlink&oid=64937487&loc=d3e36068-114959 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 35 -Paragraph 63 -Subparagraph B -URI http://asc.fasb.org/extlink&oid=64937038&loc=d3e12551-114930 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(iv)(01) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Definition Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortization period for the recovery of regulatory asset, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_RegulatoryAssetAmortizationPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |