Generating Capacity Counterparty Owned (MW)

No definition available.

Name:	ale_GeneratingCapacityCounterpartyOwnedMW
Namespace Prefix:	ale_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

Generating Capacity Jointly Owned (MW)

+ References

No definition available.

+ Details

Name:	ale_GeneratingCapacityJointlyOwnedMW
Namespace Prefix:	ale_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

Capacity of a generating facility, unit, or project in megawatts.

+ References

No definition available.

+ Details

Name:	ale_GeneratingCapacityOwnedMW
Namespace Prefix:	ale_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

Long-Term Contract for Purchase of Electric Power, Share of Plant Output Purchased

+ References

No definition available.

+ Details

Name:	ale_LongTermContractForPurchaseOfElectricPowerShareOfPlantOutputPurchasedMw
Namespace Prefix:	ale_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	duration

- Definition

Share of plant output being purchased under a long-term contract to purchase electricity from a production plant constructed and financed by a public utility district, cooperative, or other organization.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 10.D)
-URI http://asc.fasb.org/extlink&oid=6499423&loc=d3e659339-123030

+ Details

Name:	us-gaap_LongTermContractForPurchaseOfElectricPowerShareOfPlantOutputBeingPurchased
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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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Regulatory Matters - Integrated Resource Plan (Details) - MPUC [Member] - MW	Jul. 28, 2017	Sep. 30, 2017	Dec. 31, 2015
Resource Package [Member] \| Tenaska PPA [Member] \| Wind Turbine Generators [Member] \| Tenaska [Member]
Regulatory Matters [Line Items]
Generating Capacity to be Counterparty Owned (MW)		250
Resource Package [Member] \| Minimum [Member] \| Natural Gas PPA [Member] \| Natural Gas-fired [Member] \| Jointly Owned by ALLETE and Dairyland Power Cooperative [Member] \| Combined-Cycle Natural Gas-fired Generating Facility [Member] \| Jointly Owned Electricity Generation Plant [Member]
Regulatory Matters [Line Items]
Generating Capacity to be Jointly Owned (MW)	525	525
Resource Package [Member] \| Maximum [Member] \| Natural Gas PPA [Member] \| Natural Gas-fired [Member] \| Jointly Owned by ALLETE and Dairyland Power Cooperative [Member] \| Combined-Cycle Natural Gas-fired Generating Facility [Member] \| Jointly Owned Electricity Generation Plant [Member]
Regulatory Matters [Line Items]
Generating Capacity to be Jointly Owned (MW)	550	550
Minnesota Power [Member] \| Integrated Resource Plan [Member] \| Minimum [Member] \| Natural Gas-fired [Member]
Regulatory Matters [Line Items]
Additional Natural Gas-fired Generation (MW)			200
Minnesota Power [Member] \| Integrated Resource Plan [Member] \| Maximum [Member] \| Natural Gas-fired [Member]
Regulatory Matters [Line Items]
Additional Natural Gas-fired Generation (MW)			300
Minnesota Power [Member] \| Resource Package [Member] \| Tenaska PPA [Member] \| Wind Turbine Generators [Member] \| Tenaska [Member]
Regulatory Matters [Line Items]
Generating Capacity to be Counterparty Owned (MW)	250
Minnesota Power [Member] \| Resource Package [Member] \| Solar Energy PPA [Member] \| Solar Energy Generation [Member]
Regulatory Matters [Line Items]
Generating Capacity to be Counterparty Owned (MW)	10
Minnesota Power [Member] \| Resource Package [Member] \| Natural Gas PPA [Member]
Regulatory Matters [Line Items]
Long-Term Contract for Purchase of Electric Power, Share of Plant Output to be Purchased (MW)	250
Minnesota Power [Member] \| Resource Package [Member] \| Natural Gas PPA [Member] \| Natural Gas-fired [Member]
Regulatory Matters [Line Items]
Expected Output Entitlement	50.00%