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COMMITMENTS, GUARANTEES AND CONTINGENCIES - Other Matters (Details) $ in Millions | 1 Months Ended |
--- | --- | ---
Aug. 06, 2024 complaint | Mar. 31, 2025 USD ($)
Guarantor Obligations [Line Items] |  |
Production tax credits sold |  | $ 77.6
Number of complaints | complaint | 3 |
ALLETE, Inc. | Standby Letters of Credit |  |
Guarantor Obligations [Line Items] |  |
Letters of credit outstanding |  | 142.8
ALLETE, Inc. | Surety Bonds |  |
Guarantor Obligations [Line Items] |  |
Letters of credit outstanding |  | 133.2
Regulated Operations |  |
Guarantor Obligations [Line Items] |  |
Standby letters of credit and surety bonds outstanding |  | 37.9
ALLETE Clean Energy |  |
Guarantor Obligations [Line Items] |  |
Standby letters of credit and surety bonds outstanding |  | 86.6
BNI Energy Reclamation Liability |  |
Guarantor Obligations [Line Items] |  |
Estimated obligation |  | 99.5
BNI Energy Reclamation Liability | Surety Bonds |  |
Guarantor Obligations [Line Items] |  |
Collateral |  | 99.7
ALLETE South Wind | Standby Letters of Credit |  |
Guarantor Obligations [Line Items] |  |
Letters of credit outstanding |  | 10.1
South Shore Energy | Standby Letters of Credit |  |
Guarantor Obligations [Line Items] |  |
Letters of credit outstanding |  | 29.7
New Energy | Standby Letters of Credit |  |
Guarantor Obligations [Line Items] |  |
Collateral |  | $ 11.9

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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 -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (a)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482425/460-10-50-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482425/460-10-50-4 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482425/460-10-50-4 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482425/460-10-50-4 + Details
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