INCOME TAX EXPENSE (RECOVERY) - Unrecognized deferred tax assets and liabilities and company's non-capital losses (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Reconciliation of changes in deferred tax liability (asset)
Balance at the beginning of the period	$ 296.2	$ 422.5
Recognized in profit/loss	(76.4)	(149.7)
Recognized in OCI	(0.8)	9.5
Other	3.3	13.9
Balance at the end of the period	222.3	296.2
Unrecognized deferred tax assets and liabilities
Aggregated tempoarary differences associated with investments in subsidiaries	6,500.0	6,500.0
Deductible temporary differences	777.0	721.4
Tax losses	505.4	$ 458.5
Canada \| 2018 - 2037
Non-capital losses that can be applied against future taxable profit
Unused tax losses	804.2
United States \| 2018 - 2037
Non-capital losses that can be applied against future taxable profit
Unused tax losses	42.8
Chile \| No expiry
Non-capital losses that can be applied against future taxable profit
Unused tax losses	171.4
Mauritania \| 2018 - 2021
Non-capital losses that can be applied against future taxable profit
Unused tax losses	21.2
Other \| Various
Non-capital losses that can be applied against future taxable profit
Unused tax losses	$ 59.9

The amount of deductible temporary differences for which no deferred tax asset is recognised in the statement of financial position. [Refer: Temporary differences [member]]

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The amount of tax expense or income relating to changes in deferred tax liabilities and deferred tax assets, recognised in profit or loss. [Refer: Deferred tax assets; Deferred tax expense (income); Deferred tax liabilities]

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The amount of deferred tax liabilities or assets. [Refer: Deferred tax liabilities; Deferred tax assets]

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The amount of income tax relating to amounts recognised in other comprehensive income. [Refer: Other comprehensive income]

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The aggregate amount of temporary differences associated with investments in subsidiaries, branches and associates and interests in joint arrangements, for which deferred tax liabilities have not been recognised as a result of satisfying both of the following conditions: (a) the parent, investor, joint venturer or joint operator is able to control the timing of the reversal of the temporary difference; and (b) it is probable that the temporary difference will not reverse in the foreseeable future. [Refer: Associates [member]; Subsidiaries [member]; Temporary differences [member]; Investments in subsidiaries]

+ References

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The amount of unused tax losses for which no deferred tax asset is recognised in the statement of financial position. [Refer: Unused tax losses [member]]

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The amount of other increase decrease in deferred tax liability asset.

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The amount of unused tax losses.

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