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Decommissioning Liabilities (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Asset Retirement Obligation Disclosure [Line Items] |  |
Estimated reclamation discount rate | 1.80% | 1.20%
Closure cost obligations discount rate | 10.50% | 10.50%
Provision for decommissioning, restoration and rehabilitation costs | $ 114.9 |
Reclamation expenses | $ 1.2 | $ 3.5
Bottom of range [member] |  |
Asset Retirement Obligation Disclosure [Line Items] |  |
Inflation rate | 1.90% | 1.50%
Top of range [member] |  |
Asset Retirement Obligation Disclosure [Line Items] |  |
Inflation rate | 9.50% | 9.50%
Provision for decommissioning, restoration and rehabilitation costs [member] |  |
Asset Retirement Obligation Disclosure [Line Items] |  |
Asset retirement obligation, undiscounted value |  | $ 76.6
Reclamation expenses | $ 1.2 |

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