Shares received as consideration for disposal group.

No definition available.

Name:	mux_DisposalGroupIncludingDiscontinuedOperationConsiderationSharesReceived
Namespace Prefix:	mux_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Shares received as consideration for disposal group representing percentage of shares issued and outstanding of the acquiree.

+ References

No definition available.

+ Details

Name:	mux_DisposalGroupIncludingDiscontinuedOperationConsiderationSharesReceivedPercentage
Namespace Prefix:	mux_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Warrants received as consideration for disposal group.

+ References

No definition available.

+ Details

Name:	mux_DisposalGroupIncludingDiscontinuedOperationConsiderationWarrantsReceived
Namespace Prefix:	mux_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	mux_InvestmentsRollforward
Namespace Prefix:	mux_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of projects sold.

+ References

No definition available.

+ Details

Name:	mux_NumberOfProjectsSold
Namespace Prefix:	mux_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=123467817&loc=d3e21475-112644

+ Details

Name:	us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

+ References

No definition available.

+ Details

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=mux_ProjectsInNevadaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_AvailableforsaleSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

INVESTMENTS (Details) $ / shares in Units, $ in Thousands		9 Months Ended
INVESTMENTS (Details) $ / shares in Units, $ in Thousands	Jun. 23, 2021 USD ($) property $ / shares shares	Sep. 30, 2021 project	Sep. 30, 2020 USD ($)
Investments rollforward
Number of projects sold \| project		2
Proceeds from sale of investments			$ 1,266
Disposal Group
Investments rollforward
Number of projects sold \| property	2
Disposal Group \| Projects in Nevada
Investments rollforward
Cash consideration received	$ 500
Number of common shares \| shares	4,963,455
Warrants received \| shares	2,481,727
Percentage of common shares received	10.00%
Price per common share for each warrant \| $ / shares	$ 0.60
Marketable equity securities
Investments rollforward
Proceeds from sale of investments			$ 1,300