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Quarterly Financial Data (Unaudited) | 12 Months Ended
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Dec. 31, 2021
Selected Quarterly Financial Information [Abstract] |
Quarterly Financial Data (Unaudited) [Text Block] | QUARTERLY FINANCIAL DATA (UNAUDITED) Information for any one quarterly period is not necessarily indicative of the results which may be expected for the year.
Quarter Ended | Mar. 31 | Jun. 30 | Sept. 30 | Dec. 31
Millions Except Earnings Per Share |  |  |  |
2021 |  |  |  |
Operating Revenue | $339.2 |  | $335.6 |  | $345.4 |  | $399.0 |
Operating Income | $42.0 |  | $28.2 |  | $31.1 |  | $50.0 |
Net Income Attributable to ALLETE | $51.8 |  | $27.9 |  | $27.6 |  | $61.9 |
Earnings Per Share of Common Stock |  |  |  |
Basic | $0.99 |  | $0.53 |  | $0.53 |  | $1.18 |
Diluted | $0.99 |  | $0.53 |  | $0.53 |  | $1.18 |
2020 |  |  |  |
Operating Revenue | $311.6 |  | $243.2 |  | $293.9 |  | $320.4 |
Operating Income | $60.2 |  | $12.7 |  | $41.6 |  | $36.4 |
Net Income Attributable to ALLETE | $66.3 |  | $20.1 |  | $40.7 |  | $47.1 |
Earnings Per Share of Common Stock |  |  |  |
Basic | $1.28 |  | $0.39 |  | $0.78 |  | $0.91 |
Diluted | $1.28 |  | $0.39 |  | $0.78 |  | $0.90 |
2019 |  |  |  |
Operating Revenue | $357.2 |  | $290.4 |  | $288.3 |  | $304.6 |
Operating Income | $56.8 |  | $36.2 |  | $37.0 |  | $49.8 |
Net Income Attributable to ALLETE | $70.5 |  | $34.2 |  | $31.2 |  | $49.7 |
Earnings Per Share of Common Stock |  |  |  |
Basic | $1.37 |  | $0.66 |  | $0.60 |  | $0.96 |
Diluted | $1.37 |  | $0.66 |  | $0.60 |  | $0.96 |

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- Definition The entire disclosure for quarterly financial data. Includes, but is not limited to, tabular presentation of financial information for fiscal quarters, effect of year-end adjustments, and an explanation of matters or transactions that affect comparability of the information. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -URI http://asc.fasb.org/topic&trid=2126967 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=124502072&loc=SL124452896-108306 + Details
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- References No definition available. + Details
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