XML 86 R58.htm IDEA: XBRL DOCUMENT
v3.22.4

Regulatory Matters - Integrated Resource Plan (Details) - MW | 12 Months Ended |
--- | --- | ---
Dec. 31, 2022 | Feb. 01, 2021
Natural Gas-Fired [Member] | Nemadji Trail Energy Center [Member] |  |
Regulatory Matters [Line Items] |  |
Generating Capacity Jointly Owned (MW) | 600 |
Natural Gas-Fired [Member] | South Shore Energy | Nemadji Trail Energy Center [Member] |  |
Regulatory Matters [Line Items] |  |
Expected Output Entitlement (Percent) | 20.00% |
MPUC [Member] | Renewable Generation [Member] | Maximum [Member] | 2021 Integrated Resource Plan [Member] |  |
Regulatory Matters [Line Items] |  |
Generating Capacity (MW) |  | 700

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 Generating Capacity Jointly Owned (MW) + References No definition available. + Details
Name: | ale_GeneratingCapacityJointlyOwnedMW
Namespace Prefix: | ale_
Data Type: | dtr-types:powerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Share of plant output being purchased under a long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 10.D) -URI https://asc.fasb.org/extlink&oid=122136240&loc=d3e659339-123030 + Details
Name: | us-gaap_LongTermContractForPurchaseOfElectricPowerShareOfPlantOutputBeingPurchased
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
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
- Details
Name: | ale_GenerationTypeAxis=us-gaap_NaturalGasProcessingPlantMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_GeneratingFacilityAxis=ale_NemadjiTrailEnergyCenterMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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