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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 4)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014
Maximum
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Shares issued	2,500,000mux_SharesIssuedDuringPeriodForNoncashConsideration / us-gaap_RangeAxis = us-gaap_MaximumMember
Gold and Silver | El Gallo mine
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Option to sell prior to the completion of refining (as a percent)		90.00%mux_OptionToSellPriorToCompletionOfRefining / mux_MineralPropertyNameAxis = mux_ElGalloComplexMember / us-gaap_ProductOrServiceAxis = mux_GoldAndSilverMember
Period of completion of refining		15 days
Gold and gold equivalents | El Gallo 1 mine and El Gallo 2 project | NSR royalty agreement
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Net smelter return (as a percent)		3.50%mux_NetSmelterReturnFromRoyaltyAgreement / mux_MineralPropertyNameAxis = mux_ElGalloOneMineAndElGalloTwoProjectMember / us-gaap_ProductOrServiceAxis = mux_GoldAndGoldEquivalentsMember / us-gaap_TypeOfArrangementAxis = mux_NetSmelterRoyaltyAgreementMember
Quantity produced (in ounces)		148,000mux_ExplorationAndProductionPhysicalCommoditiesQuantityProduced / mux_MineralPropertyNameAxis = mux_ElGalloOneMineAndElGalloTwoProjectMember / us-gaap_ProductOrServiceAxis = mux_GoldAndGoldEquivalentsMember / us-gaap_TypeOfArrangementAxis = mux_NetSmelterRoyaltyAgreementMember
Gold and gold equivalents | El Gallo 1 mine and El Gallo 2 project | Production up to 30000 ounces | NSR royalty agreement
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Net smelter return (as a percent)		1.00%mux_NetSmelterReturnFromRoyaltyAgreement / mux_MineralPropertyNameAxis = mux_ElGalloOneMineAndElGalloTwoProjectMember / mux_ProductionOfMineralsAxis = mux_ProductionUpto30000OuncesMember / us-gaap_ProductOrServiceAxis = mux_GoldAndGoldEquivalentsMember / us-gaap_TypeOfArrangementAxis = mux_NetSmelterRoyaltyAgreementMember
Gold and gold equivalents | El Gallo 1 mine and El Gallo 2 project | Production up to 30000 ounces | NSR royalty agreement | Maximum
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Production quantity used to determine net smelter return		30,000mux_ExplorationAndProductionPhysicalCommoditiesQuantityVariablePerAgreement / mux_MineralPropertyNameAxis = mux_ElGalloOneMineAndElGalloTwoProjectMember / mux_ProductionOfMineralsAxis = mux_ProductionUpto30000OuncesMember / us-gaap_ProductOrServiceAxis = mux_GoldAndGoldEquivalentsMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_TypeOfArrangementAxis = mux_NetSmelterRoyaltyAgreementMember
Gold and gold equivalents | El Gallo 1 mine and El Gallo 2 project | Production between 30001 to 380000 ounces | NSR royalty agreement
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Net smelter return (as a percent)		3.50%mux_NetSmelterReturnFromRoyaltyAgreement / mux_MineralPropertyNameAxis = mux_ElGalloOneMineAndElGalloTwoProjectMember / mux_ProductionOfMineralsAxis = mux_ProductionBetween30001To380000OuncesMember / us-gaap_ProductOrServiceAxis = mux_GoldAndGoldEquivalentsMember / us-gaap_TypeOfArrangementAxis = mux_NetSmelterRoyaltyAgreementMember
Gold and gold equivalents | El Gallo 1 mine and El Gallo 2 project | Production between 30001 to 380000 ounces | NSR royalty agreement | Minimum
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Production quantity used to determine net smelter return		30,001mux_ExplorationAndProductionPhysicalCommoditiesQuantityVariablePerAgreement / mux_MineralPropertyNameAxis = mux_ElGalloOneMineAndElGalloTwoProjectMember / mux_ProductionOfMineralsAxis = mux_ProductionBetween30001To380000OuncesMember / us-gaap_ProductOrServiceAxis = mux_GoldAndGoldEquivalentsMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_TypeOfArrangementAxis = mux_NetSmelterRoyaltyAgreementMember
Gold and gold equivalents | El Gallo 1 mine and El Gallo 2 project | Production between 30001 to 380000 ounces | NSR royalty agreement | Maximum
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Production quantity used to determine net smelter return		380,000mux_ExplorationAndProductionPhysicalCommoditiesQuantityVariablePerAgreement / mux_MineralPropertyNameAxis = mux_ElGalloOneMineAndElGalloTwoProjectMember / mux_ProductionOfMineralsAxis = mux_ProductionBetween30001To380000OuncesMember / us-gaap_ProductOrServiceAxis = mux_GoldAndGoldEquivalentsMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_TypeOfArrangementAxis = mux_NetSmelterRoyaltyAgreementMember
Gold and gold equivalents | El Gallo 1 mine and El Gallo 2 project | Production above 380000 ounces | NSR royalty agreement
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Net smelter return (as a percent)		1.00%mux_NetSmelterReturnFromRoyaltyAgreement / mux_MineralPropertyNameAxis = mux_ElGalloOneMineAndElGalloTwoProjectMember / mux_ProductionOfMineralsAxis = mux_ProductionAbove380000OuncesMember / us-gaap_ProductOrServiceAxis = mux_GoldAndGoldEquivalentsMember / us-gaap_TypeOfArrangementAxis = mux_NetSmelterRoyaltyAgreementMember

X

- Definition

Represents the quantity of physical commodities produced by the entity during the period.

+ References

No definition available.

+ Details

Name:	mux_ExplorationAndProductionPhysicalCommoditiesQuantityProduced
Namespace Prefix:	mux_
Data Type:	num:massItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Represents the production quantity of physical commodities used as a basis to determine the net smelter return ("NSR") per the terms of the royalty agreement.

+ References

No definition available.

+ Details

Name:	mux_ExplorationAndProductionPhysicalCommoditiesQuantityVariablePerAgreement
Namespace Prefix:	mux_
Data Type:	num:massItemType
Balance Type:	na
Period Type:	duration

X

- Details

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

X

- Definition

Represents the net smelter return from the royalty agreement with a third party.

+ References

No definition available.

+ Details

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

X

- Definition

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

+ References

No definition available.

+ Details

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

X

- Definition

Represents the number of business days for completion of refining.

+ References

No definition available.

+ Details

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

X

- Definition

Number of shares issued for noncash consideration during period.

+ References

No definition available.

+ Details

Name:	mux_SharesIssuedDuringPeriodForNoncashConsideration
Namespace Prefix:	mux_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_ProductOrServiceAxis=mux_GoldAndGoldEquivalentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_ProductOrServiceAxis=mux_GoldAndSilverMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: