XML 48 R35.htm IDEA: XBRL DOCUMENT
v3.23.2

Regulatory Matters - Electric Rates (Details) - USD ($) $ in Millions |  |  | 3 Months Ended | 6 Months Ended |
--- | --- | --- | --- | --- | ---
Feb. 28, 2023 | Nov. 01, 2021 | Sep. 30, 2023 | Sep. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2022
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Regulatory Assets |  |  |  |  | $ 454.5 |  | $ 441.0
Regulatory Liabilities |  |  |  |  | 538.0 |  | 526.1
MPUC [Member] | Minnesota Cost Recovery Riders [Member] | Minnesota Power [Member] | Retail Customers [Member] | Electric Rates [Member] |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Revenue from Cost Recovery Riders and Other Regulatory Programs |  |  |  |  | 31.5 | $ 11.9 |
MPUC [Member] | 2022 Minnesota General Rate Review | Minnesota Power [Member] | Retail Customers [Member] | Electric Rates [Member] |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Revenue from Cost Recovery Riders and Other Regulatory Programs | $ 10.0 |  |  |  |  |  |
Annual Additional Revenue Generated from Requested Final Rate Increase |  | $ 108.0 |  |  |  |  |
Requested Rate Increase Percent |  | 18.00% |  |  |  |  |
Requested Return on Equity |  | 10.25% |  |  |  |  |
Requested Equity Capital Structure |  | 53.81% |  |  |  |  |
Customer Refund Liability, Current |  |  |  |  | 31.8 |  | 18.4
Approved Return on Common Equity | 9.65% |  |  |  |  |  |
Public Utilities, Approved Equity Capital Structure, Percentage | 52.50% |  |  |  |  |  |
Public Utilities, Approved Rate Increase (Decrease), Amount | $ 60.0 |  |  |  |  |  |
MPUC [Member] | ECO Annual Filing Member | Minnesota Power [Member] |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Revenue from Cost Recovery Riders and Other Regulatory Programs |  |  |  | $ 1.9 |  |  |
MPUC [Member] | ECO Annual Filing Member | Minnesota Power [Member] | Subsequent Event [Member] |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Revenue from Cost Recovery Riders and Other Regulatory Programs |  |  | $ 2.2 |  |  |  |
MPUC [Member] | Fuel Adjustment Clause 2022 | Minnesota Power [Member] | Electric Rates [Member] |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Regulatory Assets |  |  |  |  | 13.0 |  | $ 13.0
MPUC [Member] | Fuel Adjustment Clause 2023 | Minnesota Power [Member] | Electric Rates [Member] |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Regulatory Liabilities |  |  |  |  | 17.8 |  |
MPUC [Member] | ECO Triennial Filing | Minnesota Power [Member] |  |  |  |  |  |  |
Regulatory Matters [Line Items] |  |  |  |  |  |  |
Conservation Improvement Program Goal, Next Fiscal Year |  |  |  |  | 12.5 |  |
Energy Conservation and Optimization Plan Goal, Second Fiscal Year |  |  |  |  | 12.7 |  |
Energy Conservation and Optimization Plan Goal, Third Fiscal Year |  |  |  |  | $ 12.8 |  |

X
- Definition Energy Conservation and Optimization Plan Goal, Next Fiscal Year + References No definition available. + Details
Name: | ale_EnergyConservationAndOptimizationPlanGoalNextFiscalYear
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Energy Conservation and Optimization Plan Goal, Second Fiscal Year + References No definition available. + Details
Name: | ale_EnergyConservationAndOptimizationPlanGoalSecondFiscalYear
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Energy Conservation and Optimization Plan Goal, Third Fiscal Year + References No definition available. + Details
Name: | ale_EnergyConservationAndOptimizationPlanGoalThirdFiscalYear
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Current regulatory liabilities generally represent obligations to make refunds to customers for various reasons including overpayment. + References No definition available. + Details
Name: | us-gaap_CustomerRefundLiabilityCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

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 Percentage of public utility's approved return on equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
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
- 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//1943274/2147481878/980-340-50-1 + 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 -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -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: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_CurrentCostRecoveryRiderMember
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_CustomerClassAxis=ale_RetailCustomersMember
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_A2022MinnesotaGeneralRateReviewMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_ECOAnnualFilingMemberMember
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_FuelAdjustmentClause2022Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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