XML 82 R61.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Fair Value - Recurring Fair Value Measures (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Liabilities [Abstract] |  |  |  |
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Fair Value | $ 1.0 |  |  |
Available-for-sale Securities, Debt Maturities, After One Year Through Three Years, Fair Value | 2.3 |  |  |
Available-for-sale Securities, Debt Maturities, After Three Years Through Five Years, Fair Value | 2.1 |  |  |
Available-for-sale Securities, Debt Maturities, After Five Years, Fair Value | 0.8 |  |  |
Recurring Fair Value Measures [Member] |  |  |  |
Investments [Abstract] |  |  |  |
Available-for-sale – Equity Securities | 8.9 | [1] | $ 7.2 | [2]
Available-for-sale – Corporate and Governmental Debt Securities | 6.2 | [1],[3] | 10.4 | [2]
Cash Equivalents | 2.5 | [1] | 5.5 | [2]
Total Fair Value of Assets | 17.6 |  | 23.1 |
Liabilities [Abstract] |  |  |  |
Deferred Compensation | 18.0 | [4] | 21.0 | [5]
Total Fair Value of Liabilities | 18.0 |  | 21.0 |
Total Net Fair Value of Assets (Liabilities) | (0.4) |  | 2.1 |
Fair Value Hierarchy Transfers, All Levels | 0.0 |  | 0.0 |
Recurring Fair Value Measures [Member] | Level 1 [Member] |  |  |  |
Investments [Abstract] |  |  |  |
Available-for-sale – Equity Securities | 8.9 | [1] | 7.2 | [2]
Available-for-sale – Corporate and Governmental Debt Securities | 0.0 | [1],[3] | 0.0 | [2]
Cash Equivalents | 2.5 | [1] | 5.5 | [2]
Total Fair Value of Assets | 11.4 |  | 12.7 |
Liabilities [Abstract] |  |  |  |
Deferred Compensation | 0.0 | [4] | 0.0 | [5]
Total Fair Value of Liabilities | 0.0 |  | 0.0 |
Total Net Fair Value of Assets (Liabilities) | 11.4 |  | 12.7 |
Recurring Fair Value Measures [Member] | Level 2 [Member] |  |  |  |
Investments [Abstract] |  |  |  |
Available-for-sale – Equity Securities | 0.0 | [1] | 0.0 | [2]
Available-for-sale – Corporate and Governmental Debt Securities | 6.2 | [1],[3] | 10.4 | [2]
Cash Equivalents | 0.0 | [1] | 0.0 | [2]
Total Fair Value of Assets | 6.2 |  | 10.4 |
Liabilities [Abstract] |  |  |  |
Deferred Compensation | 18.0 | [4] | 21.0 | [5]
Total Fair Value of Liabilities | 18.0 |  | 21.0 |
Total Net Fair Value of Assets (Liabilities) | (11.8) |  | (10.6) |
Recurring Fair Value Measures [Member] | Level 3 [Member] |  |  |  |
Investments [Abstract] |  |  |  |
Available-for-sale – Equity Securities | 0.0 | [1] | 0.0 | [2]
Available-for-sale – Corporate and Governmental Debt Securities | 0.0 | [1],[3] | 0.0 | [2]
Cash Equivalents | 0.0 | [1] | 0.0 | [2]
Total Fair Value of Assets | 0.0 |  | 0.0 |
Liabilities [Abstract] |  |  |  |
Deferred Compensation | 0.0 | [4] | 0.0 | [5]
Total Fair Value of Liabilities | 0.0 |  | 0.0 |
Total Net Fair Value of Assets (Liabilities) | $ 0.0 |  | $ 0.0 |
[1] | Included in Other Non-Current Assets on the Consolidated Balance Sheet.
[2] | Included in Other Non-Current Assets on the Consolidated Balance Sheet.
[3] | As of December 31, 2021, the aggregate amount of available-for-sale corporate and governmental debt securities maturing in one year or less was $1.0 million, in one year to less than three years was $2.3 million, in three years to less than five years was $2.1 million and in five or more years was $0.8 million.
[4] | Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.
[5] | Included in Other Non-Current Liabilities on the Consolidated Balance Sheet.

X
- Definition Amount of available-for-sale debt securities at fair value maturing in after the fifth fiscal year following the latest fiscal year (maturing in five years or more). + References No definition available. + Details
Name: | ale_AvailableforsaleSecuritiesDebtMaturitiesAfterFiveYearsFairValue
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of available-for-sale debt securities at fair value maturing after the first fiscal year through the third fiscal year following the latest fiscal year (maturing in more than one year to less than three years). + References No definition available. + Details
Name: | ale_AvailableforsaleSecuritiesDebtMaturitiesAfterOneYearThroughThreeYearsFairValue
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of available-for-sale debt securities at fair value maturing after the third fiscal year through the fifth fiscal year following the latest fiscal year (maturing in three years to less than five years). + References No definition available. + Details
Name: | ale_AvailableforsaleSecuritiesDebtMaturitiesAfterThreeYearsThroughFiveYearsFairValue
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of transfers in and out of levels 1, 2, and 3 of the fair value hierarchy during the period. + References No definition available. + Details
Name: | ale_FairValueTransfersBetweenLevelsAllLevels
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_AssetsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -Section 50 -Paragraph 3A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123599081&loc=SL120269850-112803 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27198-111563 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as noncurrent. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=124260329&loc=d3e26626-111562 + Details
Name: | us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements payable beyond one year (or the operating cycle, if longer). + References No definition available. + Details
Name: | us-gaap_DeferredCompensationLiabilityClassifiedNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as noncurrent. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=123594786&loc=SL75136599-209740 + Details
Name: | us-gaap_EquitySecuritiesFVNINoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of asset after deduction of liability. + References No definition available. + Details
Name: | us-gaap_FairValueNetAssetLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258 + Details
Name: | us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Definition Amount of noncurrent assets that are pledged or subject to withdrawal restrictions, classified as other. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 954 -SubTopic 210 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=120413209&loc=SL6242269-115581 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 954 -SubTopic 210 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=120413173&loc=SL6242262-115580 + Details
Name: | us-gaap_OtherRestrictedAssetsNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
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: |