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Financial Instruments and Risk Management (Fair Value And Presentation in the Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Disclosure of detailed information about financial instruments [line items]
Financial assets, at fair value	$ 0.4
Financial liabilities, at fair value		$ (2.4)
Derivatives [member] | Currency Hedging Derivative Instruments [Member]
Disclosure of detailed information about financial instruments [line items]
Financial assets, at fair value	5.0	0.0
Derivatives [member] | Gold Options [Member]
Disclosure of detailed information about financial instruments [line items]
Financial assets, at fair value	0.5	3.3
Derivatives [member] | Currency Derivative Instruments [Member]
Disclosure of detailed information about financial instruments [line items]
Financial assets, at fair value	0.0
Financial liabilities, at fair value		3.3
Derivatives [member] | Share Purchase Warrants [Member]
Disclosure of detailed information about financial instruments [line items]
Financial liabilities, at fair value	$ (0.1)	$ (2.4)

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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.

+ References

No definition available.

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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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- Definition

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

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