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Equity Investments - Investment in Nobles 2 (Details) $ in Millions | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2021 USD ($) MW | Sep. 30, 2020 USD ($) | Sep. 30, 2021 USD ($) MW | Sep. 30, 2020 USD ($) | Dec. 31, 2020 USD ($)
Investment in Nobles 2 [Line Items] |  |  |  |  |  |
Equity Investment Balance |  | $ 317.8 |  | $ 317.8 |  | $ 301.2
Cash Investments |  |  |  | 17.4 | $ 91.0 |
Equity Earnings |  | 4.4 | $ 5.1 | 14.3 | 16.7 |
Net Loss Attributable to Non-Controlling Interest |  | $ (3.5) | $ (1.9) | $ (18.1) | $ (6.9) |
Nobles 2 [Member] |  |  |  |  |  |
Investment in Nobles 2 [Line Items] |  |  |  |  |  |
Ownership Percentage |  | 49.00% |  | 49.00% |  |
Equity Investment Balance |  | $ 164.8 |  | $ 164.8 |  | $ 152.2
Cash Investments |  |  |  | 17.4 |  |
Distributed Earnings |  |  |  | (3.3) |  |
Equity Earnings | [1] |  |  | (1.5) |  |
Net Loss Attributable to Non-Controlling Interest |  |  |  | $ 4.4 |  |
Wind Turbine Generators [Member] | Tenaska [Member] | Minnesota Power [Member] | Tenaska PPA [Member] |  |  |  |  |  |
Investment in Nobles 2 [Line Items] |  |  |  |  |  |
Generating Capacity Counterparty Owned (MW) | MW |  | 250 |  | 250 |  |
Long-term Contract for Purchase of Electric Power, Term of Contract (Years) |  |  |  | 20 years |  |
[1] | The Company also recorded net loss attributable to non-controlling interest of $4.4 million related to its investment in Nobles 2.

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