Anticipated Additional Generating Capacity (MW)

No definition available.

Name:	ale_AnticipatedAdditionalGeneratingCapacityMW
Namespace Prefix:	ale_
Data Type:	dtr-types1:powerItemType
Balance Type:	na
Period Type:	instant

- 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

- 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

- Definition

Solar and Wind Projects, Generating Production

+ References

No definition available.

+ Details

Name:	ale_SolarAndWindProjectsGeneratingProduction
Namespace Prefix:	ale_
Data Type:	dtr-types1:powerItemType
Balance Type:	na
Period Type:	instant

- 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

- 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

- 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

- 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

- 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

- 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

- 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

- 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

- 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

- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 405
-Name Accounting Standards Codification
-Section 25
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477571/980-405-25-1

+ Details

Name:	us-gaap_RegulatoryLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Details

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

- Details

Name:	dei_LegalEntityAxis=ale_MinnesotaPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	ale_GenerationTypeAxis=ale_RenewableGenerationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	ale_GenerationTypeAxis=ale_NewWindEnergyResourcesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ale_GenerationTypeAxis=ale_ExpandingEnergyStorageResourcesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ale_GenerationTypeAxis=ale_NaturalGasCapacityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ale_RateTypeAxis=ale_ElectricRatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_FuelAdjustmentClause2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ale_CustomerClassAxis=ale_RetailCustomersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

REGULATORY MATTERS - Electric Rates (Details) $ in Thousands					3 Months Ended
	Apr. 01, 2025 USD ($)	May 03, 2024 USD ($)	Dec. 19, 2023 USD ($)	Nov. 01, 2023 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Mar. 31, 2024 USD ($)	Mar. 03, 2025 MW	Feb. 01, 2021 MW
Regulatory Matters [Line Items]
Regulatory assets					$ 364,600	$ 371,700
ECO Annual Filing \| MPUC \| Minnesota Power
Regulatory Matters [Line Items]
Revenue from cost recovery riders and other regulatory programs						2,200
ECO Annual Filing \| MPUC \| Minnesota Power \| Subsequent Event
Regulatory Matters [Line Items]
Revenue from cost recovery riders and other regulatory programs	$ 2,600
2021 Integrated Resource Plan \| Minnesota Power
Regulatory Matters [Line Items]
Solar project, generating production (MW) \| MW								700
2021 Integrated Resource Plan \| MPUC \| Renewable Generation \| Maximum
Regulatory Matters [Line Items]
Generating capacity (MW) \| MW									700
2025 Integrated Resource Plan \| Minnesota Power \| New Wind Energy Resources
Regulatory Matters [Line Items]
Wind Project, Generating Production \| MW								400
2025 Integrated Resource Plan \| Minnesota Power \| Expanding Energy Storage Resources
Regulatory Matters [Line Items]
Energy Storage Project, Generating Production \| MW								100
2025 Integrated Resource Plan \| Minnesota Power \| Natural Gas Capacity
Regulatory Matters [Line Items]
Natural Gas Project, Generating Production \| MW								1,000
Electric Rates \| Fuel Adjustment Clause 2023 \| MPUC \| Minnesota Power
Regulatory Matters [Line Items]
Regulatory assets						$ 4,500
Retail Customers \| Electric Rates \| Current Cost Recovery Rider \| MPUC \| Minnesota Power
Regulatory Matters [Line Items]
Revenue from cost recovery riders and other regulatory programs					11,200		$ 8,300
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
Regulatory liabilities					$ 27,900