XML 109 R83.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Income Tax Expense - Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Deferred Income Tax Assets |  |
Deferred Gain - Land Sales | $ 16.5 | $ 8.3
Employee Benefits and Compensation | 20.5 | 29.3
Property-Related | 52.0 | 58.1
NOL Carryforwards | 10.6 | 13.0
Tax Credit Carryforwards | 486.9 | 557.4
Power Sales Agreements | 7.3 | 9.0
Regulatory Liabilities | 84.0 | 89.0
Other | 4.2 | 0.6
Gross Deferred Income Tax Assets | 682.0 | 764.7
Deferred Income Tax Asset Valuation Allowance | (44.9) | (58.0)
Total Deferred Income Tax Assets | 637.1 | 706.7
Deferred Income Tax Liabilities |  |
Deferred Gain | 7.1 | 7.9
Property-Related | 619.7 | 632.0
Regulatory Asset for Benefit Obligations | 46.0 | 48.1
Unamortized Investment Tax Credits | 29.0 | 29.6
Partnership Basis Differences | 164.3 | 156.5
Regulatory Assets | 24.4 | 25.3
Total Deferred Income Tax Liabilities | 890.5 | 899.4
Net Deferred Income Taxes | $ 253.4 | $ 192.7

X
- Definition Deferred ​Tax​ Assets​, Deferred Gain Land Sales + References No definition available. + Details
Name: | ale_DeferredTaxAssetsDeferredGainLandSales
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Deferred Tax Assets, Regulatory Liabilities + References No definition available. + Details
Name: | ale_DeferredTaxAssetsRegulatoryLiabilities
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Deferred Tax Liabilities - Deferred Gain + References No definition available. + Details
Name: | ale_DeferredTaxLiabilitiesDeferredGain
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Deferred Tax Liabilities, Regulatory Assets for Benefit Obligations + References No definition available. + Details
Name: | ale_DeferredTaxLiabilitiesRegulatoryAssetsforBenefitObligations
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Deferred Tax Liability, Partnership Basis Differences + References No definition available. + Details
Name: | ale_DeferredTaxLiabiltyPartnershipBasisDifferences
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Power Purchase Agreements, Deferred Tax Asset + References No definition available. + Details
Name: | ale_PowerPurchaseAgreementsDeferredTaxAsset
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The noncurrent portion of the reserve for accumulated deferred investment tax credits as of the balance sheet date. This is the remaining investment credit, which will reduce the cost of services collected from ratepayers by a ratable portion over the investment's regulatory life. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(26)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 27 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482525/740-10-45-27 + Details
Name: | us-gaap_AccumulatedDeferredInvestmentTaxCredit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of deferred tax liability attributable to taxable temporary differences. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(26)(b)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-2 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(26)(a)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(15)(2)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 + Details
Name: | us-gaap_DeferredIncomeTaxLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-2 + Details
Name: | us-gaap_DeferredTaxAssetsGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-2 + Details
Name: | us-gaap_DeferredTaxAssetsNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_DeferredTaxAssetsNetOfValuationAllowanceAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-6 + Details
Name: | us-gaap_DeferredTaxAssetsOperatingLossCarryforwards
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences, classified as other. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-6 + Details
Name: | us-gaap_DeferredTaxAssetsOther
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from property, plant, and equipment. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-6 + Details
Name: | us-gaap_DeferredTaxAssetsPropertyPlantAndEquipment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-6 + Details
Name: | us-gaap_DeferredTaxAssetsTaxCreditCarryforwards
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from employee compensation. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-6 + Details
Name: | us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeCompensation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-2 + Details
Name: | us-gaap_DeferredTaxAssetsValuationAllowance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-2 + Details
Name: | us-gaap_DeferredTaxLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_DeferredTaxLiabilitiesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-6 + Details
Name: | us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of deferred tax liability attributable to taxable temporary differences from regulatory assets. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 740 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482685/740-10-50-6 + Details
Name: | us-gaap_DeferredTaxLiabilitiesRegulatoryAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant