Name:	ale_AvailableForSaleSecuritiesFairValueDisclosureDebtSecurities
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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represeent Available-for-sale Securities which consist of all investments in certain equity securities neither classified as trading or held-to-maturity securities. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options and put options, but do not include convertible debt.

No definition available.

Name:	ale_AvailableForSaleSecuritiesFairValueDisclosureEquitySecurities
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This element represents the portion of the balance sheet assertion, Deferred Compensation, valued at fair value by the entity.

No definition available.

Name:	ale_DeferredCompensationFairValueDisclosure
Namespace Prefix:	ale_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Fair Value Activity in Level 3

No definition available.

Name:	ale_FairValueActivityInLevel3
Namespace Prefix:	ale_
Data Type:	xbrli:monetaryItemType
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The amount of transfers in and out of levels 1, 2 and 3 of the fair value hierarchy during the period.

No definition available.

Name:	ale_FairValueHierarchyTransfersAllLevels
Namespace Prefix:	ale_
Data Type:	xbrli:monetaryItemType
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This element represents the portion of the balance sheet Investments line item's cash and cash equivalents, valued at fair value by the entity.

No definition available.

Name:	ale_InvestmentsCashAndCashEquivalentsFairValueDisclosure
Namespace Prefix:	ale_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a recurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Period Type:	instant

- Details

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Fair value of asset after deduction of liability.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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- Details

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Period Type:	duration

Aggregation of the liabilities reported on the balance sheet measured at fair value on a recurring basis by the entity.

No definition available.