XML 51 R37.htm IDEA: XBRL DOCUMENT
v3.21.2

Regulatory Matters - Verso Corporation (Details) - Verso Corporation (Member) $ in Millions | Sep. 30, 2021 USD ($)
--- | ---
Electric Services Agreement |
Schedule of Regulatory Assets and Liabilities [Line Items] |
Outstanding Customer Accounts Receivable | $ 1.2
Steam Services Agreement |
Schedule of Regulatory Assets and Liabilities [Line Items] |
Outstanding Customer Accounts Receivable | $ 2.4

X
- Definition Schedule of Regulatory Assets and Liabilities [Line Items] + References No definition available. + Details
Name: | ale_ScheduleOfRegulatoryAssetsAndLiabilitiesLineItems
Namespace Prefix: | ale_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 954 -SubTopic 310 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=123366838&loc=d3e3073-115593 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(3)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(5)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
Name: | us-gaap_AccountsReceivableNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | ale_ServiceAgreementTypeAxis=ale_ElectricServicesAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=ale_VersoCorporationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | ale_ServiceAgreementTypeAxis=ale_SteamServicesAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |