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v3.19.3.a.u2

Investments Textuals (Details) $ in Millions, $ in Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Apr. 01, 2017 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Aug. 31, 2020 AUD ($) | Feb. 12, 2020 AUD ($) | Dec. 31, 2019 AUD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Changes in tax reserves | $ (9.2) | $ 7.2 | $ 3.0 | $ 2.1 |  |  |
Equity method investment | 0.0 | 0.0 | $ 9.0 | 0.0 |  |  |
Middlemount Mine |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Ownership percentage of equity method investment |  |  | 50.00% |  |  |  | 50.00%
Middlemount Mine |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Intercompany loans |  |  |  |  |  |  | $ 50.0
Financing Receivable, Stated Interest Rate |  |  | 15.00% |  |  |  |
Intercompany loans, carrying value |  |  | $ 17.1 | 0.0 |  |  |
Financing Receivable | Middlemount Mine |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Financing Receivable, Cash received from Equity Interest | 32.7 | 48.1 | $ 14.7 | 106.7 |  |  |
Equity method investment and financing receivables related to Middlemount |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Ownership percentage of equity method investment |  |  | 50.00% |  |  |  | 50.00%
Middlemount Mine |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Equity Method Investment, Summarized Financial Information, Net Income (Loss) |  |  |  | 9.0 |  |  |
Changes in tax reserves |  |  |  | 17.0 |  |  |
Equity Method Investment, Summarized Financial Information, Revenue | $ 60.0 | $ 193.0 | $ 160.0 | 271.0 |  |  |
Equity Method Investment, Summarized Financial Information, Current Assets |  |  | 30.8 | 33.6 |  |  |
Equity Method Investment, Summarized Financial Information, Noncurrent Assets |  |  | 209.7 | 181.8 |  |  |
Equity Method Investment, Summarized Financial Information, Current Liabilities |  |  | 225.8 | 187.9 |  |  |
Equity Method Investment, Summarized Financial Information, Noncurrent Liabilities |  |  | $ 40.1 | $ 35.8 |  |  |
Scenario, Forecast | Middlemount Mine |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |
Intercompany loans |  |  |  |  | $ 50.0 | $ 70.0 |

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