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v3.19.1

Business Segments (Details) $ in Millions | 3 Months Ended |
--- | --- | ---
Mar. 31, 2019 USD ($) a Segments | Mar. 31, 2018 USD ($) | Dec. 31, 2018 USD ($)
Business Segments [Line Items] |  |  |  |
Number of Reportable Segments | Segments |  | 3 |  |
Operating Revenue |  | $ 357.2 | $ 358.2 |
Net Income (Loss) |  | 70.5 | 51.0 |
Approximate Gain on Sale of U.S. Water Services, After-tax |  | 10.0 |  |
Assets |  | $ 5,218.8 |  | $ 5,165.0
Regulated Operations [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Number of Operating Segments | Segments |  | 3 |  |
Operating Revenue |  | $ 282.2 | 270.2 |
Net Income (Loss) |  | 51.5 | 43.9 |
Assets |  | 3,962.7 |  | 3,952.5
Regulated Operations [Member] | Residential [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue |  | 45.2 | 40.7 |
Regulated Operations [Member] | Commercial [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue |  | 38.9 | 36.6 |
Regulated Operations [Member] | Municipal [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue |  | 15.4 | 14.0 |
Regulated Operations [Member] | Industrial [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue |  | 121.6 | 114.9 |
Regulated Operations [Member] | Other Power Suppliers [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue |  | 39.4 | 43.7 |
Regulated Operations [Member] | Other [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue |  | 21.7 | 20.3 |
ALLETE Clean Energy [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue |  | 17.5 | 24.6 |
Net Income (Loss) |  | 5.8 | 8.1 |
Assets |  | 643.8 |  | 606.6
ALLETE Clean Energy [Member] | Long-term PSA [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue |  | 14.6 | 18.6 |
ALLETE Clean Energy [Member] | Other [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue, Other Than Customer Revenue |  | 2.9 | 6.0 |
U.S. Water Services [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue | [1] | 33.4 | 38.2 |
Net Income (Loss) |  | (1.1) | (1.4) |
Assets | [2] | 0.0 |  | 295.8
U.S. Water Services [Member] | Point-in-Time [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue | [1] | 19.0 | 22.3 |
U.S. Water Services [Member] | Contract [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue | [1] | 9.2 | 9.5 |
U.S. Water Services [Member] | Capital Project [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue | [1] | $ 5.2 | 6.4 |
Corporate and Other [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Number of Operating Segments | Segments |  | 2 |  |
Land in Minnesota (Acres) | a |  | 4,000 |  |
Operating Revenue |  | $ 24.1 | 25.2 |
Net Income (Loss) |  | 14.3 | 0.4 |
Assets |  | 612.3 |  | $ 310.1
Corporate and Other [Member] | Long-term Contract [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue |  | 20.2 | 20.0 |
Corporate and Other [Member] | Other [Member] |  |  |  |
Business Segments [Line Items] |  |  |  |
Operating Revenue |  | $ 3.9 | $ 5.2 |
[1] | On March 26, 2019, ALLETE completed the sale of U.S. Water Services. The Company recognized a gain on the sale of approximately $10 million after-tax reflected in Corporate and Other in 2019. (See Note 1. Operations and Significant Accounting Policies.)
[2] | On March 26, 2019, ALLETE completed the sale of U.S. Water Services. (See Note 1. Operations and Significant Accounting Policies.)

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