ASSET RETIREMENT OBLIGATIONS - Mineral Property Interests (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Mineral Property Interests
Mineral property interests	$ 237,373	$ 287,490	$ 237,245
Income tax recovery	(1,867)	(1,163)
Exploration costs	$ (1,740)	(2,342)
Percentage of annual fees on surety bonds	1.50%
Percentage of upfront deposit on surety bonds	10.00%
MSC
Mineral Property Interests
Income tax recovery	$ 4,603	2,412	$ 15,942
Argentina
Mineral Property Interests
Mineral property interests	191,490	202,889
Exploration costs	(310)	(263)
Mexico
Mineral Property Interests
Mineral property interests	9,086	10,374
Exploration costs	$ (785)	$ (1,599)

Mineral Property Interests [Line Items]

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- Definition

Represents the percentage of annual fees on the value of the surety bonds.

+ References

No definition available.

+ Details

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- Definition

Represents the percentage of upfront deposit on the value of the surety bonds.

+ References

No definition available.

+ Details

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- Definition

Exploration expenses (including prospecting) related to the mining industry would be included in operating expenses. Exploration costs include costs incurred in identifying areas that may warrant examination and in examining specific areas that are considered to have prospects of mineral reserves.

+ References

No definition available.

+ Details

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- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a),(b)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32639-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Income Tax Expense (or Benefit)
-URI http://asc.fasb.org/extlink&oid=6515339

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- Definition

Mineral properties, net of adjustments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 360
-Section 25
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=56951519&loc=d3e64895-109465

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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