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v3.21.2

Business Segments (Details) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2021 USD ($) a | Sep. 30, 2020 USD ($) | Sep. 30, 2021 USD ($) a Segments | Sep. 30, 2020 USD ($) | Dec. 31, 2020 USD ($)
Business Segments [Line Items] |  |  |  |  |
Number of Reportable Segments | Segments |  |  | 2 |  |
Operating Revenue | $ 345.4 | $ 293.9 | $ 1,020.2 | $ 848.7 |
Net Income (Loss) Attributable to ALLETE | 27.6 | 40.7 | 107.3 | 127.1 |
Assets | 6,332.2 |  | $ 6,332.2 |  | $ 6,084.6
Regulated Operations [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Number of Operating Segments | Segments |  |  | 3 |  |
Operating Revenue | 304.8 | 255.1 | $ 888.2 | 721.2 |
Net Income (Loss) Attributable to ALLETE | 32.9 | 42.4 | 99.4 | 111.0 |
Assets | 4,207.4 |  | 4,207.4 |  | 4,196.8
Regulated Operations [Member] | Residential [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | 37.0 | 34.2 | 118.0 | 102.5 |
Regulated Operations [Member] | Commercial [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | 44.3 | 37.1 | 124.7 | 103.2 |
Regulated Operations [Member] | Municipal [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | 14.4 | 11.2 | 38.5 | 30.5 |
Regulated Operations [Member] | Industrial [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | 139.7 | 109.6 | 407.8 | 316.4 |
Regulated Operations [Member] | Other Power Suppliers [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | 41.2 | 30.9 | 116.9 | 96.6 |
Regulated Operations [Member] | Other [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | 25.8 | 29.7 | 79.9 | 69.6 |
Regulated Operations [Member] | CIP Financial Incentive [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | 2.4 | 2.4 | 2.4 | 2.4 |
ALLETE Clean Energy [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | 16.9 | 14.8 | 59.4 | 52.5 |
Net Income (Loss) Attributable to ALLETE | (0.8) | 1.1 | 11.7 | 16.8 |
Assets | 1,691.4 |  | 1,691.4 |  | 1,483.3
ALLETE Clean Energy [Member] | Long-term PSA [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | 14.0 | 11.9 | 50.8 | 44.0 |
ALLETE Clean Energy [Member] | Other [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue, Other Than Customer Revenue | $ 2.9 | 2.9 | $ 8.6 | 8.5 |
Corporate and Other [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Number of Operating Segments | Segments |  |  | 2 |  |
Land in Minnesota (Acres) | a | 4,000 |  | 4,000 |  |
Operating Revenue | $ 23.7 | 24.0 | $ 72.6 | 75.0 |
Net Income (Loss) Attributable to ALLETE | (4.5) | (2.8) | (3.8) | (0.7) |
Assets | 433.4 |  | 433.4 |  | $ 404.5
Corporate and Other [Member] | Long-term Contract [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | 20.3 | 20.7 | 63.4 | 65.6 |
Corporate and Other [Member] | Other [Member] |  |  |  |  |
Business Segments [Line Items] |  |  |  |  |
Operating Revenue | $ 3.4 | $ 3.3 | $ 9.2 | $ 9.4 |

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