XML 139 R102.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Pension Plans and Other Postretirement Benefit Plans - Schedule of Fair Value Hierarchy of pension Plan's Assets (Details) - Pension Plan and SERP [Member] - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | $ 608 | [1] | $ 590 | [1] | $ 541
Cash Equivalents [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 8 |  | 7 |  |
Fixed Income Securities [Member] | US Government Debt Securities [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 37 |  | 19 |  |
Fixed Income Securities [Member] | Domestic Corporate Debt Securities [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 213 |  | 175 |  |
Fixed Income Securities [Member] | Debt Security, Government, Non-US [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 33 |  | 27 |  |
Fixed Income Securities [Member] | Municipal Bonds [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 11 |  | 14 |  |
Mutual Funds [Member] | U.S Equity Securities [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 160 |  | 170 |  |
Mutual Funds [Member] | International Equity Securities [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 63 |  | 75 |  |
Common/Collective Trusts [Member] | Real Estate [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 24 |  | 25 |  |
Partnership And Closely Held Investments [Member] | International Equity Securities [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 52 |  | 71 |  |
Partnership And Closely Held Investments [Member] | Real Estate [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 7 |  | 7 |  |
Level 1 [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 223 |  | 245 |  |
Level 1 [Member] | Mutual Funds [Member] | U.S Equity Securities [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 160 |  | 170 |  |
Level 1 [Member] | Mutual Funds [Member] | International Equity Securities [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 63 |  | 75 |  |
Level 2 [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 302 |  | 242 |  |
Level 2 [Member] | Cash Equivalents [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 8 |  | 7 |  |
Level 2 [Member] | Fixed Income Securities [Member] | US Government Debt Securities [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 37 |  | 19 |  |
Level 2 [Member] | Fixed Income Securities [Member] | Domestic Corporate Debt Securities [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 213 |  | 175 |  |
Level 2 [Member] | Fixed Income Securities [Member] | Debt Security, Government, Non-US [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | 33 |  | 27 |  |
Level 2 [Member] | Fixed Income Securities [Member] | Municipal Bonds [Member] |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |
Fair value of plan assets | $ 11 |  | $ 14 |  |
[1] | As of December 31, 2024, the SERP had a projected benefit obligation of $27 million and an accumulated benefit obligation of $26 million, with no plan assets.

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

X
- Definition Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_USGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_MunicipalBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_MutualFundMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ava_USEquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ava_InternationalEquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ava_CommonAndCollectiveTrustsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_RealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_PartnershipMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |