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Financial Instruments and Risk Management (Fair Value And Presentation in the Balance Sheet) (Details) - Derivatives [member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items]
Financial assets, at fair value		$ 3.3
Financial liabilities, at fair value	$ 4.4
Currency Hedging Derivative Instruments [Member]
Disclosure of detailed information about financial instruments [line items]
Financial assets, at fair value		3.3
Financial liabilities, at fair value	4.3
Fuel Options [Member]
Disclosure of detailed information about financial instruments [line items]
Financial assets, at fair value		0.0
Financial liabilities, at fair value	0.1
Gold Options [Member]
Disclosure of detailed information about financial instruments [line items]
Financial assets, at fair value		$ (0.7)
Financial liabilities, at fair value	$ 0.0

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- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table.

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- Definition

The fair value of financial assets. [Refer: At fair value [member]; Financial assets]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-IssueDate 2020-01-01
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- Definition

The fair value of financial liabilities. [Refer: At fair value [member]; Financial liabilities]

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