XML 64 R50.htm IDEA: XBRL DOCUMENT
v3.24.1.u1

Commitments, Guarantees and Contingencies - Other Matters (Details) - USD ($) $ in Millions | Apr. 30, 2024 | Mar. 31, 2024
--- | --- | ---
Subsequent Event |  |
Guarantor Obligations [Line Items] |  |
Production tax credits sold | $ 14.0 |
ALLETE, Inc. | Standby Letters of Credit |  |
Guarantor Obligations [Line Items] |  |
Letters of credit outstanding |  | $ 150.1
Regulated Operations | Standby Letters of Credit |  |
Guarantor Obligations [Line Items] |  |
Letters of credit outstanding |  | 25.4
ALLETE Clean Energy | Standby Letters of Credit |  |
Guarantor Obligations [Line Items] |  |
Letters of credit outstanding |  | 80.6
BNI Energy Reclamation Liability |  |
Guarantor Obligations [Line Items] |  |
Estimated obligation |  | 82.1
BNI Energy Reclamation Liability | Surety Bonds |  |
Guarantor Obligations [Line Items] |  |
Collateral |  | 82.4
ALLETE South Wind | Standby Letters of Credit |  |
Guarantor Obligations [Line Items] |  |
Letters of credit outstanding |  | 10.1
South Shore Energy | Standby Letters of Credit |  |
Guarantor Obligations [Line Items] |  |
Letters of credit outstanding |  | $ 29.7

X
- Definition Amount of any assets held either as collateral or by third parties that, upon the occurrence of any triggering event or condition under the guarantee, can be obtained and liquidated to recover all or a portion of the amounts paid under the guarantee. + References No definition available. + Details
Name: | ale_GuarantorObligationsCollateralHeldDirectlyOrByThirdPartiesAmount
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Guarantor Obligations, Production Tax Credits Sold + References No definition available. + Details
Name: | ale_GuarantorObligationsProductionTaxCreditsSold
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482425/460-10-50-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482425/460-10-50-4 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482425/460-10-50-4 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482425/460-10-50-4 + Details
Name: | us-gaap_GuaranteeObligationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482425/460-10-50-4 + Details
Name: | us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
Name: | us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Details
Name: | ale_GuaranteeEntityandTypeAxis=ale_AlleteIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_StandbyLettersOfCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_GuaranteeEntityandTypeAxis=ale_RegulatedOperationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_GuaranteeEntityandTypeAxis=ale_ALLETECleanEnergyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_GuaranteeEntityandTypeAxis=ale_BniCoalReclamationLiabilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_SuretyBondMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_GuaranteeEntityandTypeAxis=ale_ALLETESouthWindMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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