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Schedule II | 12 Months Ended
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Dec. 31, 2021
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] |
Schedule II [Text Block] | Schedule II ALLETE Valuation and Qualifying Accounts and Reserves
| Balance at Beginning of Period | Additions | Deductions from Reserves (a) | Balance at End of Period
| Charged to Income | Other Charges
Millions |  |  |  |  |
Reserve Deducted from Related Assets |  |  |  |  |
Reserve For Uncollectible Accounts |  |  |  |  |
2019 Trade Accounts Receivable | $1.7 |  | $(0.1) | — |  | $0.7 |  | $0.9 |
Finance Receivables – Long-Term | — |  | — |  | — |  | — |  | — |
2020 Trade Accounts Receivable | $0.9 |  | $2.7 | — |  | $1.1 |  | $2.5 |
Finance Receivables – Long-Term | — |  | — |  | — |  | — |  | — |
2021 Trade Accounts Receivable | $2.5 |  | $1.2 |  | — |  | $1.9 |  | $1.8 |
Finance Receivables – Long-Term | — |  | — |  | — |  | — |  | — |
Deferred Asset Valuation Allowance |  |  |  |  |
2019 Deferred Tax Assets | $66.5 |  | $3.5 | — |  | — |  | $70.0 |
2020 Deferred Tax Assets | $70.0 |  | $(0.1) | — |  | — |  | $69.9 |
2021 Deferred Tax Assets | $69.9 |  | $(0.9) | — |  | — |  | $69.0 |
(a) Includes uncollectible accounts written-off.

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- Definition The entire disclosure for valuation and qualifying accounts and reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 09 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24092-122690 + Details
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