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Commitments, Guarantees and Contingencies - Capacity and Energy Table (Details) - MW	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Manitoba Hydro | Minnesota Power | Manitoba Hydro PPA (Expires 2040)
Power Purchase Agreements [Line Items]
Output being purchased - electric energy (MW)	133
Manitoba Hydro | Minnesota Power | Manitoba Hydro PPA (Expires May 2035)
Power Purchase Agreements [Line Items]
Output being purchased - electric energy and capacity (MW)	250
Tenaska | Minnesota Power | Nobles 2
Power Purchase Agreements [Line Items]
Output being purchased - electric energy and capacity (MW)	250
Oliver Wind | Minnesota Power | Oliver Wind I PPA
Power Purchase Agreements [Line Items]
Output being purchased - electric energy (MW)	50
Oliver Wind | Minnesota Power | Oliver Wind II PPA
Power Purchase Agreements [Line Items]
Output being purchased - electric energy (MW)	48
Basin | Minnesota Power | Basin Power Sales Agreement (Expires May 2028)
Power Purchase Agreements [Line Items]
Output being sold electric - capacity (MW)	100
Great River Energy | Minnesota Power | Great River Energy Power Sales Agreement (Expires May 2025)
Power Purchase Agreements [Line Items]
Output being sold electric - capacity (MW)	100
Oconto Electric Cooperative | Minnesota Power | Oconto Electric Cooperative Power Sales Agreement
Power Purchase Agreements [Line Items]
Output being sold electric - energy and capacity (MW)	25
Basin Electric Power Cooperative | Minnesota Power | Basin Electric Cooperative PSA June 2022 - May 2023
Power Purchase Agreements [Line Items]
Output being sold electric - capacity (MW)	75
Basin Electric Power Cooperative | Minnesota Power | Basin Electric Cooperative PSA June 2023 - May 2025
Power Purchase Agreements [Line Items]
Output being sold electric - capacity (MW)	125
Square Butte | Minnesota Power | Square Butte PPA | Square Butte Coal-fired Unit
Power Purchase Agreements [Line Items]
Expected output entitlement	50.00%
Minnkota Power | Square Butte PPA | Minnkota Sales Agreement | Square Butte Coal-fired Unit
Power Purchase Agreements [Line Items]
Expected output entitlement	37.00%	32.00%	28.00%
Silver Bay Power | Minnesota Power | Silver Bay Power Self-Generation
Power Purchase Agreements [Line Items]
Energy generation owned (MW)	90
Calpine Corporation PPA | Calpine Corporation | Minnesota Power
Power Purchase Agreements [Line Items]
Output being purchased - electric capacity (MW)	25

X

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Generating Capacity Owned (MW)

+ References

No definition available.

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- Definition

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+ References

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- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 10.D)
-SubTopic 10
-Topic 980
-Publisher FASB
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- 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://fasb.org/us-gaap/role/ref/legacyRef
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480114/980-10-S99-1

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