XML 123 R97.htm IDEA: XBRL DOCUMENT v3.25.0.1

Pension and Other Postretirement Benefit Plans - Recurring Fair Value Measures (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pension
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	$ 604.1	$ 589.0	$ 568.6
Pension | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	251.3	155.0
Pension | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	334.5	415.1
Pension | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	18.3	18.9
Pension | U.S. Large-cap
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	73.2	83.7
Pension | U.S. Large-cap | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	73.2	0.0
Pension | U.S. Large-cap | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	83.7
Pension | U.S. Large-cap | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Pension | U.S. Mid-cap Growth
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	35.1	69.9
Pension | U.S. Mid-cap Growth | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	35.1	0.0
Pension | U.S. Mid-cap Growth | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	69.9
Pension | U.S. Mid-cap Growth | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Pension | U.S. Small-cap
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	31.6	46.5
Pension | U.S. Small-cap | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	31.6	0.0
Pension | U.S. Small-cap | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	46.5
Pension | U.S. Small-cap | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Pension | International
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	201.6	134.6
Pension | International | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	102.5	134.6
Pension | International | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	99.1	0.0
Pension | International | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Pension | Fixed Income Securities
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	235.4	215.0
Pension | Fixed Income Securities | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Pension | Fixed Income Securities | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	235.4	215.0
Pension | Fixed Income Securities | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Pension | Cash and Cash Equivalents
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	8.9	20.4
Pension | Cash and Cash Equivalents | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	8.9	20.4
Pension | Cash and Cash Equivalents | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Pension | Cash and Cash Equivalents | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Pension | Real Estate
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	18.3	18.9
Pension | Real Estate | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Pension | Real Estate | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Pension | Real Estate | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	18.3	18.9	22.4
Postretirement Health and Life
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	174.2	173.8	$ 162.6
Postretirement Health and Life | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	174.2	173.8
Postretirement Health and Life | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | U.S. Large-cap
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	32.1	30.0
Postretirement Health and Life | U.S. Large-cap | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	32.1	30.0
Postretirement Health and Life | U.S. Large-cap | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | U.S. Large-cap | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | U.S. Mid-cap Growth
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	30.0	28.7
Postretirement Health and Life | U.S. Mid-cap Growth | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	30.0	28.7
Postretirement Health and Life | U.S. Mid-cap Growth | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | U.S. Mid-cap Growth | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | U.S. Small-cap
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	15.7	14.9
Postretirement Health and Life | U.S. Small-cap | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	15.7	14.9
Postretirement Health and Life | U.S. Small-cap | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | U.S. Small-cap | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | International
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	37.9	41.9
Postretirement Health and Life | International | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	37.9	41.9
Postretirement Health and Life | International | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | International | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | Cash and Cash Equivalents
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	2.4	3.2
Postretirement Health and Life | Cash and Cash Equivalents | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	2.4	3.2
Postretirement Health and Life | Cash and Cash Equivalents | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | Cash and Cash Equivalents | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | Mutual Funds
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	56.1	55.1
Postretirement Health and Life | Mutual Funds | Level 1
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	56.1	55.1
Postretirement Health and Life | Mutual Funds | Level 2
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	0.0	0.0
Postretirement Health and Life | Mutual Funds | Level 3
Recurring Fair Value Measures [Line Items]
Fair Value of Assets	$ 0.0	$ 0.0

X

- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480482/715-20-55-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

+ Details

Name:	us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-3

+ Details

Name:	us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ale_USLargeCapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ale_USMidCapGrowthMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ale_USSmallCapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ale_InternationalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_CashAndCashEquivalentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_RealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: