XML 52 R38.htm IDEA: XBRL DOCUMENT
v3.25.1

OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES - Other Income (Expense) (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2025 | Mar. 31, 2024
Other Income (Expense) |  |
Total Other Income | $ 4.6 | $ 8.6
Pension and Other Postretirement Benefit Plan Non-Service Credits |  |
Other Income (Expense) |  |
Total Other Income | 1.8 | 4.3
Interest and Investment Income |  |
Other Income (Expense) |  |
Total Other Income | 1.9 | 1.9
AFUDC - Equity |  |
Other Income (Expense) |  |
Total Other Income | 1.4 | 1.2
Other Income (Expense) |  |
Other Income (Expense) |  |
Total Other Income | $ (0.5) | $ 1.2

X
- Definition [Line Items] for Other Income (Expense) - Other [Table] + References No definition available. + Details
Name: | ale_OtherIncomeExpenseOtherLineItems
Namespace Prefix: | ale_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of income (expense) related to nonoperating activities, classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 220 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(9)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2 + Details
Name: | us-gaap_OtherNonoperatingIncomeExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | ale_ComponentofOtherIncomeExpenseOtherAxis=ale_PensionandOtherPostretirementBenefitPlansNonServiceCreditMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_ComponentofOtherIncomeExpenseOtherAxis=ale_InterestandInvestmentEarningsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_ComponentofOtherIncomeExpenseOtherAxis=ale_AFUDCEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_ComponentofOtherIncomeExpenseOtherAxis=ale_OtherIncomeExpenseOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |