Addition to mineral properties.

No definition available.

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- Definition

Represents the amount of deferred income tax recovery on impairment of mineral properties.

+ References

No definition available.

+ Details

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- Definition

Mineral Property Interests [Line Items]

+ References

No definition available.

+ Details

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- Definition

The required payment of gross revenue less allowable deductions to the tiered net smelter return royalty (the “Royalty”) on the El Gallo 1 Mine.

+ References

No definition available.

+ Details

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- Definition

The eventually reduced percentage of required payment of gross revenue less allowable deductions to the tiered net smelter return royalty (the “Royalty”) on the El Gallo 1 Mine.

+ References

No definition available.

+ Details

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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

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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=65882285&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

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash outflow from the purchase of mining and mining related assets during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585

+ Details

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Balance Type:	credit
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- Details

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Namespace Prefix:
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- Details

Name:	mux_MineralPropertyNameAxis=mux_TonkinProjectMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	mux_MineralPropertyNameAxis=mux_GoldBarProjectMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=mux_RoyaltyMember
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- Details

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- Details

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- Details

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- Details

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MINERAL PROPERTY INTEREST AND ASSET RETIREMENT OBLIGATIONS - Mineral Property Interests (Details) - USD ($) $ in Thousands			3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2018	Apr. 19, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Mineral Property Interests
Purchase price					$ 5,950
Mineral property interests			$ 242,350	$ 257,106	242,350	$ 257,106	$ 237,245
Impairment charges				1,198		29,740
Recovery of deferred income tax				10,400		10,400
Income tax recovery			(607)	(1,619)	(3,330)	(15,103)
Exploration costs			(2,166)	(1,830)	$ (5,595)	(7,252)
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			(1,691)	(1,630)	$ (7,825)	(6,282)	$ (15,942)
Tonkin Project
Mineral Property Interests
Impairment charges						8,900
Gold Bar Project
Mineral Property Interests
Impairment charges						20,800
Royalty
Mineral Property Interests
Required payment of gross revenue less allowable deductions to the tiered net smelter return royalty on the El Gallo 1 Mine (as a percent)		3.50%
Eventually reduced percentage of required payment		1
Purchase price	$ 1,000	$ 5,300
Royalty \| Non-current other liabilities
Mineral Property Interests
Purchase price					1,000
Royalty \| El Gallo 1 mine
Mineral Property Interests
Additional to mineral properties		5,100
Royalty \| El Gallo 2 Properties
Mineral Property Interests
Additional to mineral properties		$ 1,200
Argentina
Mineral Property Interests
Mineral property interests			191,490	202,889	191,490	202,889
Exploration costs			(543)	(268)	(1,046)	(1,190)
Mexico
Mineral Property Interests
Mineral property interests			14,062	9,730	14,062	9,730
Exploration costs			$ (1,094)	$ (788)	$ (2,739)	$ (3,662)