NATURE OF OPERATIONS AND RECENT ACCOUNTING PRONOUNCEMENTS (Details)	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017
MSC
Ownership interest (as a percent)	49.00%	49.00%
El Gallo 1 mine
Option to sell prior to the completion of refining (as a percent)	90.00%
Period of completion of refining	10 days
Minimum
Period over which concentrates are provisionally priced at the end of a period after delivery to the customer	30 days
Maximum
Period over which concentrates are provisionally priced at the end of a period after delivery to the customer	90 days

Represents the option held by the entity to sell the product prior to completion of refining.

No definition available.

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Namespace Prefix:	mux_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of business days for completion of refining.

+ References

No definition available.

+ Details

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Namespace Prefix:	mux_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period over which concentrates are provisionally priced, whereby the selling price is subject to final adjustments at the end of a period after delivery to the customer.

+ References

No definition available.

+ Details

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Namespace Prefix:	mux_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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