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Equity Investments Equity Investment in Nobles 2 (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2021 USD ($) MW | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Equity Investments [Line Items] |  |  |  |
Equity Investments |  | $ 318.0 | $ 301.2 |
Cash Investments |  | 17.6 | 99.1 | $ 37.9
Equity Earnings |  | 20.0 | 22.1 | 21.7
Net Loss Attributable to Non-Controlling Interest |  | (31.4) | (12.6) | (0.1)
Nobles 2 [Member] |  |  |  |
Equity Investments [Line Items] |  |  |  |
Net Loss Attributable to Non-Controlling Interest |  | $ 6.6 |  |
Nobles 2 [Member] |  |  |  |
Equity Investments [Line Items] |  |  |  |
Equity Method Investment, Ownership Percentage |  | 49.00% |  |
Equity Investments |  | $ 163.5 | 152.2 |
Cash Investments |  | 17.6 |  |
Equity Earnings | [1] | (1.3) |  |
Distributed Earnings |  | $ (5.0) |  |
ATC [Member] |  |  |  |
Equity Investments [Line Items] |  |  |  |
Equity Method Investment, Ownership Percentage |  | 8.00% |  |
Equity Investments |  | $ 154.5 | 149.0 | $ 141.6
Cash Investments |  | 0.0 | 2.7 |
Expected Additional Investment in 2022 |  | 6.0 |  |
Equity Earnings |  | 21.3 | 22.3 |
Distributed Earnings |  | $ (17.2) | $ (18.9) |
Wind Turbine Generators [Member] | Tenaska [Member] | Minnesota Power [Member] | Nobles 2 PPA [Member] |  |  |  |
Equity Investments [Line Items] |  |  |  |
Contract Term (Years) |  | 20 years |  |
Generating Capacity Counterparty Owned (MW) | MW |  | 250 |  |
[1] | The Company also recorded net loss attributable to non-controlling interest of $6.6 million related to its investment in Nobles 2

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