Income and Mining Taxes (Details Textual) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Unrecognized tax benefits	$ 17.4	$ 16.1
Interest and penalties accrued	9.4	$ 6.9
Minimum [Member]
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits is reasonably possible	0.8
Maximum [Member]
Income Tax Contingency [Line Items]
Decrease in unrecognized tax benefits is reasonably possible	$ 1.1

Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 15

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Name Accounting Standards Codification

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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