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Financial Instruments and Risk Management (Fair Value for Assets and Liabilities) (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Disclosure of fair value measurement of assets [line items] |  |
Financial assets (liabilities) | $ (3,621.5) | $ (3,636.5)
Financial liabilities | 885.9 | 785.0
Level 1 [member] | Recurring fair value measurement [member] |  |
Disclosure of fair value measurement of assets [line items] |  |
Fair value, net asset (liability) | 23.9 | 43.7
Level 2 [member] | Recurring fair value measurement [member] |  |
Disclosure of fair value measurement of assets [line items] |  |
Fair value, net asset (liability) | 3.5 | 4.4
Derivatives [member] |  |
Disclosure of fair value measurement of assets [line items] |  |
Financial assets, at fair value | 3.0 | 4.4
Fair value through profit or loss | Gold Options [Member] | Level 2 [member] | Recurring fair value measurement [member] |  |
Disclosure of fair value measurement of assets [line items] |  |
Financial liabilities | 0.5 | 0.0
Fair value through OCI | Currency Hedging Derivative Instruments [Member] | Level 2 [member] | Recurring fair value measurement [member] |  |
Disclosure of fair value measurement of assets [line items] |  |
Financial assets (liabilities) | (2.6) |
Financial liabilities |  | 4.3
Fair value through OCI | Fuel Options [Member] | Level 2 [member] | Recurring fair value measurement [member] |  |
Disclosure of fair value measurement of assets [line items] |  |
Financial liabilities |  | 0.1
Fair value through OCI | Trading securities [member] | Level 1 [member] | Recurring fair value measurement [member] |  |
Disclosure of fair value measurement of assets [line items] |  |
Financial assets (liabilities) | $ (23.9) | $ (43.7)

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