XML 54 R39.htm IDEA: XBRL DOCUMENT
v3.25.2

REGULATORY MATTERS - Electric Rates (Details) $ in Thousands |  |  |  |  | 3 Months Ended | 6 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Apr. 01, 2025 USD ($) | May 03, 2024 USD ($) | Dec. 19, 2023 USD ($) | Nov. 01, 2023 USD ($) | Dec. 31, 2024 USD ($) | Jun. 30, 2025 USD ($) | Jun. 30, 2024 USD ($) | Aug. 04, 2025 MW | Mar. 03, 2025 MW | Feb. 01, 2021 MW
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  |  |  | $ 371,700 | $ 363,000 |  |  |  |
Total Non-Current Regulatory Liabilities |  |  |  |  | 570,500 | 586,700 |  |  |  |
MPUC | Minnesota Power | New Wind Energy Resources | Subsequent Event |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Wind project, generating production (MW) | MW |  |  |  |  |  |  |  | 200 |  |
ECO Annual Filing | MPUC | Minnesota Power |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Revenue from cost recovery riders and other regulatory programs | $ 2,600 |  |  |  | $ 2,200 |  |  |  |  |
2025 Integrated Resource Plan | Minnesota Power | New Wind Energy Resources |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Wind project, generating production (MW) | MW |  |  |  |  |  |  |  |  | 400 |
2025 Integrated Resource Plan | Minnesota Power | Expanding Energy Storage Resources |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Energy storage project, generating production (MW) | MW |  |  |  |  |  |  |  |  | 100 |
2025 Integrated Resource Plan | Minnesota Power | Natural Gas Capacity |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Natural gas project, generating production (MW) | MW |  |  |  |  |  |  |  |  | 1,000 |
2021 Integrated Resource Plan | Minnesota Power |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Solar and wind projects, generating production (MW) | MW |  |  |  |  |  |  |  |  | 700 |
2021 Integrated Resource Plan | MPUC | Renewable Generation | Maximum |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Generating capacity (MW) | MW |  |  |  |  |  |  |  |  |  | 700
Electric Rates | Fuel Adjustment Clause 2024 | MPUC | Minnesota Power |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Regulatory assets |  |  |  |  |  | 4,500 |  |  |  |
Electric Rates | Fuel Adjustment Clause 2025 | MPUC | Minnesota Power |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Total Non-Current Regulatory Liabilities |  |  |  |  |  | 5,700 |  |  |  |
Retail Customers | Electric Rates | Current Cost Recovery Rider | MPUC | Minnesota Power |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Revenue from cost recovery riders and other regulatory programs |  |  |  |  |  | $ 22,900 | $ 13,300 |  |  |
Retail Customers | Electric Rates | 2024 Minnesota General Rate Case | MPUC | Minnesota Power |  |  |  |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |
Requested rate increase percent |  |  |  | 12.00% |  |  |  |  |  |
Requested return on equity |  | 9.78% |  | 10.30% |  |  |  |  |  |
Requested equity capital structure |  |  |  | 53.00% |  |  |  |  |  |
Annual additional revenue generated from requested final rate increase |  | $ 33,970 |  | $ 89,000 |  |  |  |  |  |
Approved rate increase |  |  | $ 64,000 |  |  |  |  |  |  |

X
- Definition Anticipated Additional Generating Capacity (MW) + References No definition available. + Details
Name: | ale_AnticipatedAdditionalGeneratingCapacityMW
Namespace Prefix: | ale_
Data Type: | dtr-types:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Energy Storage Project, Generating Production + References No definition available. + Details
Name: | ale_EnergyStorageProjectGeneratingProduction
Namespace Prefix: | ale_
Data Type: | dtr-types:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Natural Gas Project, Generating Production + References No definition available. + Details
Name: | ale_NaturalGasProjectGeneratingProduction
Namespace Prefix: | ale_
Data Type: | dtr-types:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Solar and Wind Projects, Generating Production + References No definition available. + Details
Name: | ale_SolarAndWindProjectsGeneratingProduction
Namespace Prefix: | ale_
Data Type: | dtr-types:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Wind Project, Generating Production + References No definition available. + Details
Name: | ale_WindProjectGeneratingProduction
Namespace Prefix: | ale_
Data Type: | dtr-types:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of public utility's approved rate increase (decrease) by regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of public utility's requested equity to capital, including debt and equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedEquityCapitalStructurePercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's requested rate increase (decrease) with regulatory agency. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedRateIncreaseDecreasePercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of public utility's requested return on equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesRequestedReturnOnEquityPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of regulated other operating revenues recognized during the period. + References No definition available. + Details
Name: | us-gaap_RegulatedOperatingRevenueOther
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are not expected to be recovered through revenue sources within one year or the normal operating cycle if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 980 -SubTopic 340 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478742/980-340-50-1 + Details
Name: | us-gaap_RegulatoryAssetsNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount for the individual regulatory noncurrent liability as itemized in a table of regulatory noncurrent liabilities as of the end of the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(24)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_RegulatoryLiabilityNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_RegulatoryAgencyAxis=ale_MPUCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | ale_GenerationTypeAxis=ale_NewWindEnergyResourcesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_ECOAnnualFilingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_A2025IntegratedResourcePlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_GenerationTypeAxis=ale_ExpandingEnergyStorageResourcesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_GenerationTypeAxis=ale_NaturalGasCapacityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_A2021IntegratedResourcePlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_GenerationTypeAxis=ale_RenewableGenerationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_RateTypeAxis=ale_ElectricRatesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_FuelAdjustmentClause2024Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_FuelAdjustmentClause2025Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_CustomerClassAxis=ale_RetailCustomersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_CurrentCostRecoveryRiderMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_A2024MinnesotaGeneralRateCaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |