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Commitments, Guarantees and Contingencies - Other Matters (Details) $ in Millions | Jun. 30, 2023 USD ($)
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Regulated Operations [Member] | Standby Letters of Credit [Member] |
Guarantor Obligations [Line Items] |
Letters of Credit Outstanding, Amount | $ 22.2
ALLETE Clean Energy [Member] | Standby Letters of Credit [Member] |
Guarantor Obligations [Line Items] |
Letters of Credit Outstanding, Amount | 105.6
BNI Energy Reclamation Liability [Member] |
Guarantor Obligations [Line Items] |
Estimated Obligation | 82.1
BNI Energy Reclamation Liability [Member] | Surety Bonds [Member] |
Guarantor Obligations [Line Items] |
Collateral | 82.4
ALLETE South Wind [Member] | Standby Letters of Credit [Member] |
Guarantor Obligations [Line Items] |
Letters of Credit Outstanding, Amount | 10.1
ALLETE, Inc. [Member] | Standby Letters of Credit [Member] |
Guarantor Obligations [Line Items] |
Letters of Credit Outstanding, Amount | 161.9
South Shore Energy | Standby Letters of Credit [Member] |
Guarantor Obligations [Line Items] |
Letters of Credit Outstanding, Amount | $ 23.9

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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 (b)(1) -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 (c) -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 (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482425/460-10-50-4 + Details
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- Definition 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. + References Reference 1: 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 + Details
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