XML 31 R10.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Operations and Significant Accounting Policies - Supplemental Statement of Cash Flow Information - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Supplemental Cash Flow Information [Abstract] |  |  |  |
Cash Paid During the Period for Interest – Net of Amounts Capitalized |  | $ 66.8 | $ 62.0 | $ 63.5
Recognition of Right-of-use Assets and Lease Liabilities | [1] | 0.0 | 0.0 | 28.7
Noncash Investing and Financing Activities [Abstract] |  |  |  |
Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment |  | (14.0) | (67.0) | 33.9
Reclassification of Redeemable Non-Controlling Interest to Current Liabilities | [2] | 30.6 | 0.0 | 0.0
Capitalized Asset Retirement Costs |  | 16.9 | 4.1 | 20.7
AFUDC–Equity |  | $ 2.6 | $ 1.9 | $ 2.3
[1] | Amount of the right-of-use asset and lease liability recognized with the adoption of an accounting standards update for leases.
[2] | Amount reclassified to Current Liabilities resulting from the exercise of an option to buy out a non-controlling interest.

X
- Definition Amount of asset retirement obligation costs incurred that were capitalized during the period. This may include liabilities incurred and revisions in cash flow estimates. + References No definition available. + Details
Name: | ale_CostsIncurredCapitalizedAssetRetirementObligationCosts
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment + References No definition available. + Details
Name: | ale_IncreaseDecreaseinAccountsPayableforCapitalAdditionstoPropertyPlantandEquipment
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Non-Cash Reclassification of Redeemable Non-Controlling Interest to Current Liabilities + References No definition available. + Details
Name: | ale_NonCashReclassificationOfRedeemableNonControllingInterestToCurrentLiabilities
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Non Cash Impact From the Recognition of Right-of-use Assets and Lease Liabilities + References No definition available. + Details
Name: | ale_RecognitionofRightofuseAssetsandLeaseLiabilities
Namespace Prefix: | ale_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Definition The increase (decrease) during the reporting period in the capitalized cost of equity (based on assumed rate of return) and / or borrowed funds (based on interest rate) used to finance construction of regulated assets, which is expected to be recovered through rate adjustments. As a result of this capitalization, net income is increased. This element pertains to certain regulated industries, such as public utilities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585 + Details
Name: | us-gaap_IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of cash paid for interest, excluding capitalized interest, classified as operating activity. Includes, but is not limited to, payment to settle zero-coupon bond for accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=123431023&loc=d3e4297-108586 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 17 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3367-108585 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3536-108585 + Details
Name: | us-gaap_InterestPaidNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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