XML 72 R44.htm IDEA: XBRL DOCUMENT v3.22.4

Operations and Significant Accounting Policies - Business Segments (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) Customers MW	Dec. 31, 2021
Business Segments [Line Items]
Number of Reportable Segments	2	3
Square Butte [Member] | Square Butte PPA [Member]
Business Segments [Line Items]
Minnesota Power Output Entitlement (MW) | MW	227.5
Nemadji Trail Energy Center [Member]
Business Segments [Line Items]
Estimated Capital Expenditures, Including Past Expenditures | $	$ 700
Square Butte [Member] | Square Butte [Member] | Square Butte PPA [Member]
Business Segments [Line Items]
Generating Capacity Counterparty Owned (MW) | MW	455
Minnesota Power [Member] | Square Butte [Member] | Square Butte [Member] | Square Butte PPA [Member]
Business Segments [Line Items]
Expected Output Entitlement (Percent)	50.00%
South Shore Energy | Nemadji Trail Energy Center [Member]
Business Segments [Line Items]
Capital Cost Spent to Date | $	$ 7
Estimated Capital Expenditures, ALLETE Portion | $	$ 150
New Energy
Business Segments [Line Items]
Discount Rate - Input for Goodwill Analysis	14.00%
Terminal Growth Rate - Input for Goodwill Analysis	3.50%
Regulated Operations [Member] | Minnesota Power [Member] | Retail Customers [Member] | Electric Rates [Member]
Business Segments [Line Items]
Number of Customers	150,000
Regulated Operations [Member] | Minnesota Power [Member] | Municipal Customers [Member] | Electric Rates [Member]
Business Segments [Line Items]
Number of Customers	14
Regulated Operations [Member] | SWL&P [Member] | Retail Customers [Member] | Electric Rates [Member]
Business Segments [Line Items]
Number of Customers	15,000
Regulated Operations [Member] | SWL&P [Member] | Retail Customers [Member] | Natural Gas [Member]
Business Segments [Line Items]
Number of Customers	13,000
Regulated Operations [Member] | SWL&P [Member] | Retail Customers [Member] | Water [Member]
Business Segments [Line Items]
Number of Customers	10,000
ALLETE Clean Energy [Member] | ALLETE Clean Energy [Member]
Business Segments [Line Items]
Energy Generation Owned (MW) | MW	1,200
Generating Capacity Under Construction (MW) | MW	100
Corporate and Other [Member] | BNI Energy [Member]
Business Segments [Line Items]
Number of Customers	2
Corporate and Other [Member] | BNI Energy [Member] | Square Butte [Member]
Business Segments [Line Items]
Number of Customers	1
Nobles 2 [Member]
Business Segments [Line Items]
Ownership Percentage	49.00%
Natural Gas-Fired [Member] | Nemadji Trail Energy Center [Member]
Business Segments [Line Items]
Generating Capacity Jointly Owned (MW) | MW	600
Natural Gas-Fired [Member] | South Shore Energy | Nemadji Trail Energy Center [Member]
Business Segments [Line Items]
Expected Output Entitlement (Percent)	20.00%
Wind Turbine Generators [Member] | Minnesota Power [Member] | Tenaska [Member] | Nobles 2 PPA [Member]
Business Segments [Line Items]
Generating Capacity Counterparty Owned (MW) | MW	250
Contract Term (Years)	20 years

X

- Definition

Capital cost spent to date for project.

+ References

No definition available.

+ Details

Name:	ale_CapitalCostSpentToDate
Namespace Prefix:	ale_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Discount Rate - Input for Goodwill Analysis

+ References

No definition available.

+ Details

Name:	ale_DiscountRateInputForGoodwillAnalysis
Namespace Prefix:	ale_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Estimated Capital Expenditures, ALLETE Portion

+ References

No definition available.

+ Details

Name:	ale_EstimatedCapitalExpendituresALLETEPortion
Namespace Prefix:	ale_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

The estimated amount of certain capital expenditures related to environmental compliance, regulatory matters, or other commitments and/or contingencies. This estimate includes expenditures expected in future periods and expenditures made through the end of the current period.

+ References

No definition available.

+ Details

Name:	ale_EstimatedCapitalExpendituresIncludingPastExpenditures
Namespace Prefix:	ale_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Generating Capacity Counterparty Owned (MW)

+ References

No definition available.

+ Details

Name:	ale_GeneratingCapacityCounterpartyOwnedMW
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

Generating Capacity Owned (MW)

+ References

No definition available.

+ Details

Name:	ale_GeneratingCapacityOwnedMW
Namespace Prefix:	ale_
Data Type:	dtr-types:powerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Generating Capacity Under Construction (MW)

+ References

No definition available.

+ Details

Name:	ale_GeneratingCapacityUnderConstructionMW
Namespace Prefix:	ale_
Data Type:	dtr-types:powerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Long-Term Contract for Purchase of Electric Power, Share of Plant Output Purchased

+ References

No definition available.

+ Details

Name:	ale_LongTermContractForPurchaseOfElectricPowerShareOfPlantOutputPurchasedMw
Namespace Prefix:	ale_
Data Type:	dtr-types:powerItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Term in years of long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization.

+ References

No definition available.

+ Details

Name:	ale_LongtermContractforPurchaseofElectricPowerTermofContractYears
Namespace Prefix:	ale_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Number of Customers

+ References

No definition available.

+ Details

Name:	ale_NumberOfCustomers
Namespace Prefix:	ale_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Terminal Growth Rate - Input for Goodwill Analysis

+ References

No definition available.

+ Details

Name:	ale_TerminalGrowthRateInputForGoodwillAnalysis
Namespace Prefix:	ale_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI https://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
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

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 18
-URI https://asc.fasb.org/extlink&oid=126901519&loc=d3e8672-108599

+ Details

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
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_SegmentReportingInformationLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	ale_GeneratingFacilityAxis=ale_SquareButteCoalFiredUnitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_SquareButtePpaMember
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:	srt_CounterpartyNameAxis=ale_SquareButteMember
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:	dei_LegalEntityAxis=ale_SouthShoreEnergyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ale_RegulatedOperationsMemberMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ale_CustomerClassAxis=us-gaap_RetailMember
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:	ale_CustomerClassAxis=ale_MunicipalCustomersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ale_ALLETECleanEnergyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_CorporateAndOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=ale_Nobles2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ale_GenerationTypeAxis=us-gaap_NaturalGasProcessingPlantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	srt_CounterpartyNameAxis=ale_TenaskaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_TenaskaPPAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: