The amount of cost incurred in review of resources.

No definition available.

Name:	mux_CostIncurredInReviewOfResources
Namespace Prefix:	mux_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The period over which the paychecks protection ("PPP") program funds are fully forgiven so long eligible expenditures are incurred.

+ References

No definition available.

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of income (expense) related to nonoperating activities, classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

+ Details

Name:	us-gaap_OtherNonoperatingIncomeExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=mux_PaycheckProtectionProgramMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=mux_CanadianEmergencyWageSubsidyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

OTHER INCOME (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended
OTHER INCOME (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Costs incurred				$ 500
Other income	$ 2,090	$ 4,773		6,071	$ 6,283
Paycheck Protection Program
Debt Instrument [Line Items]
Amount of relief secured	1,900		$ 1,900	1,900
Period over which paychecks protection ("PPP") program funds are fully forgiven so long eligible expenditures are incurred			168 days
Canadian Emergency Wage Subsidy
Debt Instrument [Line Items]
Amount of relief secured	$ 3,400		$ 3,400	$ 3,400