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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Interest rate of capital improvement revenue and special assessment bonds used to fund real estate development projects.

No definition available.

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Data Type:	num:percentItemType
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Period Type:	instant

Term (in years) of capital improvement revenue and special assessment bonds used to fund real estate development projects.

No definition available.

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Period Type:	instant

Original principal amount of special assessment bonds used to fund real estate development projects which are not included in Long-term Debt on the Consolidated Balance Sheet.

No definition available.

Name:	ale_CommunityDevelopmentDistrictObligationOriginalPrincipal
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Ownership percentage of property benefitied by a real estate development project funded by municipal capital improvement revenue and special assessment bonds.

No definition available.

Name:	ale_CommunityDevelopmentDistrictObligationOwnershipOfPropertyBenefited
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Data Type:	num:percentItemType
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Amount of any assets held either as collateral or by third parties that, upon the occurence of any triggering event or condition under the guarantee, can be obtained and liquidated to recover all or a portion of the amounts paid under the guarantee.

No definition available.

Name:	ale_GuarantorObligationsCollateralHeldDirectlyorbyThirdPartiesAmount
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Data Type:	xbrli:monetaryItemType
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Name:	us-gaap_GuaranteeObligationsLineItems
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Data Type:	xbrli:stringItemType
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Period Type:	duration

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)(1)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

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Namespace Prefix:
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Namespace Prefix:
Data Type:	na
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Period Type:

Name:	ale_GuaranteeEntityandTypeAxis=ale_TownCenterCommunityDevelopmentDistrictMember
Namespace Prefix:
Data Type:	na
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