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Acquisitions - ACE Wind (Details) $ in Millions | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Feb. 28, 2014 USD ($) | Jan. 31, 2014 USD ($) MW | Dec. 31, 2014 USD ($) | Dec. 31, 2015 USD ($)
Liabilities Assumed [Abstract] |  |  |  |  |
Power Purchase Agreements - Non-Current Liability | [1] |  |  | $ 110.7 | $ 138.1
Goodwill |  |  |  | 2.9 | 130.6
Power Purchase Agreements - Current Liability | [2] |  |  | 19.4 | $ 23.3
Armenia Mountain [Member] |  |  |  |  |
Liabilities Assumed [Abstract] |  |  |  |  |
Purchase Option |  |  | $ 0.3 |  |
ACE Wind [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Date of Acquisition |  |  | January 2014 |  |
Payments to Acquire Businesses |  |  | $ 26.9 |  |
Number of Wind Energy Facilities Acquired |  |  | 3 |  |
Assets Acquired [Abstract] |  |  |  |  |
Cash and Cash Equivalents |  |  | $ 3.8 |  |
Other Current Assets |  |  | 14.3 |  |
Property, Plant and Equipment |  |  | 156.9 |  |
Other Non-Current Assets | [3] |  | 7.5 |  |
Total Assets Acquired |  |  | 182.5 |  |
Liabilities Assumed [Abstract] |  |  |  |  |
Current Liabilities | [4] |  | 15.2 |  |
Long-Term Debt Due Within One Year |  |  | 2.2 |  |
Long-Term Debt |  |  | 21.1 |  |
Power Purchase Agreements - Non-Current Liability |  |  | 99.4 |  |
Other Non-Current Liabilities |  |  | 10.6 |  |
Non-Controlling Interest | [5] |  | 7.1 |  |
Total Liabilities and Non-Controlling Interest Assumed |  |  | 155.6 |  |
Net Identifiable Assets Acquired |  |  | 26.9 |  |
Goodwill |  |  | 2.9 |  |
Deductible Goodwill |  |  | 0.0 |  |
Power Purchase Agreements - Current Liability |  |  | $ 12.4 |  |
Acquisition-Related Costs |  |  |  | $ 1.4 |
Purchase of Non-Controlling Interest |  | $ 6.0 |  |  |
Storm Lake II [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Name of Acquired Entity |  |  | Storm Lake II |  |
Generating Capacity (MW) | MW |  |  | 77 |  |
Lake Benton [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Name of Acquired Entity |  |  | Lake Benton |  |
Generating Capacity (MW) | MW |  |  | 104 |  |
Condon [Member] |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |
Name of Acquired Entity |  |  | Condon |  |
Generating Capacity (MW) | MW |  |  | 50 |  |
[1] | Power Purchase Agreements acquired in conjunction with the ALLETE Clean Energy wind energy facilities acquisitions. (See Note 7. Acquisitions.)
[2] | Power Purchase Agreements acquired in conjunction with the ALLETE Clean Energy wind energy facilities acquisitions. (See Note 7. Acquisitions.)
[3] | Included in Other Non-Current Assets was $0.3 million for the option to purchase Armenia Mountain, and goodwill of $2.9 million. For tax purposes, the purchase price allocation resulted in no allocation to goodwill.
[4] | Current Liabilities included $12.4 million related to the current portion of Power Purchase Agreements.
[5] | The purchase price accounting valued the non-controlling interest related to Lake Benton, Storm Lake II and Condon at fair value using the discounted cash flow method.

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