Generating Capacity Counterparty Owned (MW)

No definition available.

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Namespace Prefix:	ale_
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Balance Type:	na
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- Definition

Term in years of long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization.

+ References

No definition available.

+ Details

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Namespace Prefix:	ale_
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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
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-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

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- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
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-Section 50
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-Publisher FASB
-Name Accounting Standards Codification
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of distribution received from equity method investee for return of investment, classified as investing activities. Excludes distribution for return on investment, classified as operating activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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- Details

Name:	ale_GenerationTypeAxis=ale_WindTurbineGeneratorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=ale_ResourcePackageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=ale_TenaskaMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_RegulatoryAgencyAxis=ale_MPUCMember
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- Details

Name:	dei_LegalEntityAxis=ale_MinnesotaPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongTermContractForPurchaseOfElectricPowerAxis=ale_TenaskaPPAMember
Namespace Prefix:
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Balance Type:
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Equity Investments Investment in Nobles 2 (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($) MW	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Investment in Nobles 2 [Line Items]
Equity Method Investment Balance	$ 154.8		$ 161.1
Return of Capital From Equity Investments	$ 8.3	$ 0.0
Nobles 2 [Member]
Investment in Nobles 2 [Line Items]
Ownership Percentage	49.00%
Equity Method Investment Balance	$ 24.8		$ 33.0
Return of Capital From Equity Investments	$ 8.3
Wind Turbine Generators [Member] \| Resource Package [Member] \| Tenaska [Member] \| MPUC [Member] \| Minnesota Power [Member] \| Tenaska PPA [Member]
Investment in Nobles 2 [Line Items]
Generating Capacity Counterparty Owned (MW) \| MW	250
Long-term Contract for Purchase of Electric Power, Term of Contract (Years)	20 years