Gross realized gains (losses) on equity securities.

No definition available.

Name:	mux_AvailableForSaleAndTradingSecuritiesGrossUnrealizedGainLoss
Namespace Prefix:	mux_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

Cash flow for purchase of available for sale and trading securities.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow associated with the sale of equity securities classified as available-for-sale or trading securities. This refers to cash disposals and includes conversions and removals.

+ References

No definition available.

+ Details

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

- Definition

A rollforward 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_TradingSecuritiesRollforward
Namespace Prefix:	mux_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Gross realized gains (losses) on warrants.

+ References

No definition available.

+ Details

Name:	mux_WarrantsGrossUnrealizedGainLoss
Namespace Prefix:	mux_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740

+ Details

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

- Definition

Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

+ Details

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

- Definition

Cash paid to purchase debt and equity securities, classified as operating activities, during the period; includes trading securities and any other investments classified as operating.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3536-108585

+ Details

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

- 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

- Definition

Price of a single share of a number of saleable stocks of a company.

+ References

No definition available.

+ Details

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_StatementEquityComponentsAxis=mux_IssuanceOfFlowThroughCommonSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

INVESTMENTS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Mar. 29, 2019	Dec. 20, 2018	Dec. 19, 2017
Investments rollforward
Opening balance			$ 3,131	$ 7,971	$ 7,971
Additions during the period			264	1,211
Net gain (loss) on securities sold				(767)
Disposals during period				(3,601)
Unrealized gains (loss) on securities held	$ 900	$ (500)	1,752	(2,502)
Fair Value end of the period	5,147	2,312	5,147	2,312	3,131
Fair value of warrants
Proceeds from sale of investments				3,667
Cost of purchase of marketable equity securities			3,100		2,900
Price per unit						$ 1.55
Flow Through Common Shares
Fair value of warrants
Price per unit							$ 2.24	$ 2.50
Marketable equity securities
Investments rollforward
Opening balance			2,718	6,404	6,404
Additions during the period			264	1,211
Net gain (loss) on securities sold				(767)
Disposals during period				(2,899)
Unrealized gains (loss) on securities held	700		1,372	(1,637)
Fair Value end of the period	4,354	2,312	4,354	2,312	2,718
Fair value of warrants
Proceeds from sale of investments		$ 200
Warrants
Investments rollforward
Opening balance			413	1,567	1,567
Disposals during period				(702)
Unrealized gains (loss) on securities held			380	$ (865)
Unrealized gains (loss) on warrants	200
Fair Value end of the period	$ 793		$ 793		$ 413