XML 78 R64.htm IDEA: XBRL DOCUMENT
v2.4.1.9

FAIR VALUE ACCOUNTING (Details) (USD $) | 12 Months Ended | 3 Months Ended |
--- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2014 | Jun. 30, 2014 | Dec. 31, 2013 | Jun. 30, 2013 | Jan. 24, 2012
Liabilities: |  |  |  |  |  |  |  |
Number of shares of common stock required to be issued as a part of settlement | 712,830 mux_NumberOfSharesAgreedToBeIssuedUnderAgreement | 90,300 mux_NumberOfSharesAgreedToBeIssuedUnderAgreement |  |  |  |  |  |
Fair Value of remaining common shares outstanding payable | $ 400,000 mux_FairValueOfRemainingCommonSharesOutstandingPayable | $ 200,000 mux_FairValueOfRemainingCommonSharesOutstandingPayable |  |  |  |  |  |
Ownership interest (as a percent) | 100.00%us-gaap_EquityMethodInvestmentOwnershipPercentage |  |  | 100.00%us-gaap_EquityMethodInvestmentOwnershipPercentage |  |  |  |
Number of shares remaining under agreement | 319,640 mux_NumberOfSharesRemainingUnderAgreement | 90,300 mux_NumberOfSharesRemainingUnderAgreement |  |  |  |  |  |
Investment in MSC | 177,018,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures | 212,947,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures | 273,948,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures | 177,018,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures |  | 212,947,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures |  |
Total Loss | 353,736,000 us-gaap_AssetImpairmentCharges | 62,963,000 us-gaap_AssetImpairmentCharges | 18,468,000 us-gaap_AssetImpairmentCharges |  |  |  |  |
ARGENTINA |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 27,000,000 us-gaap_AssetImpairmentCharges / mux_AllCountriesAxis = country_AR |  |  |  |  |  |  |
Other United States Properties |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss |  |  | 2,900,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_OtherUnitedStatesPropertiesMember |  |  |  |  |
Los Azules Copper Project |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Discount Rate (as a percent) | 35.00%us-gaap_FairValueInputsDiscountRate / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember |  |  | 35.00%us-gaap_FairValueInputsDiscountRate / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember | 35.00%us-gaap_FairValueInputsDiscountRate / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember |  |  |
Total Loss | 228,300,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember |  |  | 107,900,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember | 120,400,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember |  |  |
Tonkin Complex |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 25,400,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_TonkinComplexMember |  |  |  |  |  |  |
Gold Bar Complex |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 31,400,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_GoldBarComplexMember |  |  |  |  |  |  |
North Battle Mountain Complex Located in Nevada, United States |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 1,900,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_NorthBattleMountainComplexLocatedInNevadaUnitedStatesMember |  |  |  |  |  |  |
MSC |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Discount Rate (as a percent) | 20.00%us-gaap_FairValueInputsDiscountRate / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |  |  |  | 40.00%us-gaap_FairValueInputsDiscountRate / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember | 40.00%us-gaap_FairValueInputsDiscountRate / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |
Ownership interest (as a percent) | 49.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember | 49.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember | 49.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember | 49.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  | 49.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  | 49.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember
Investment in MSC | 177,018,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember | 212,947,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember | 273,948,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember | 177,018,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  | 212,947,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |
Total Loss | 21,200,000 us-gaap_AssetImpairmentCharges / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |  |  |  |  |  |
TNR | Los Azules Copper Project |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Back-in Right required to be owned as a percentage of equity | 0.40%mux_LossContingencySettlementBackInRightAsPercentageOfEquity / us-gaap_CounterpartyNameAxis = mux_TNRGoldCorpMember / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember |  |  |  |  |  |  |
Recurring | Total |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Investments | 1,082,000 us-gaap_InvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 2,000 us-gaap_InvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 1,082,000 us-gaap_InvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 2,000 us-gaap_InvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Assets | 1,082,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 2,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 1,082,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 2,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Liabilities: |  |  |  |  |  |  |  |
Accounts payable and accrued liabilities | 355,000 us-gaap_AccountsPayableAndAccruedLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 177,000 us-gaap_AccountsPayableAndAccruedLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 355,000 us-gaap_AccountsPayableAndAccruedLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 177,000 us-gaap_AccountsPayableAndAccruedLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Liabilities | 355,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 177,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 355,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 177,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Recurring | Level 1 |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Investments | 1,082,000 us-gaap_InvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 2,000 us-gaap_InvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 1,082,000 us-gaap_InvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 2,000 us-gaap_InvestmentsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Assets | 1,082,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 2,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 1,082,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 2,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Liabilities: |  |  |  |  |  |  |  |
Accounts payable and accrued liabilities | 355,000 us-gaap_AccountsPayableAndAccruedLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 177,000 us-gaap_AccountsPayableAndAccruedLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 355,000 us-gaap_AccountsPayableAndAccruedLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 177,000 us-gaap_AccountsPayableAndAccruedLiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Liabilities | 355,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember | 177,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 355,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  | 177,000 us-gaap_LiabilitiesFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel1Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsRecurringMember |  |
Nonrecurring |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 308,210,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 152,554,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |  |  |  |  |  |
Nonrecurring | Telken Tenements |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss |  | 13,792,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TelkenTenementsMember |  |  |  |  |  |
Nonrecurring | Other United States Properties |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss |  | 9,497,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_OtherUnitedStatesPropertiesMember |  |  |  |  |  |
Nonrecurring | Este Tenements |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss |  | 2,784,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_EsteTenementsMember |  |  |  |  |  |
Nonrecurring | Piramides Tenements |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss |  | 5,079,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_PiramidesTenementsMember |  |  |  |  |  |
Nonrecurring | Tobias Tenements |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss |  | 6,074,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TobiasTenementsMember |  |  |  |  |  |
Nonrecurring | Los Azules Copper Project |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 228,301,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember |  |  |  |  |  |  |
Nonrecurring | Tonkin Complex |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 31,391,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TonkinComplexMember |  |  |  |  |  |  |
Nonrecurring | Gold Bar Complex |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 25,435,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_GoldBarComplexMember |  |  |  |  |  |  |
Nonrecurring | Limo Complex |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss |  | 19,450,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LimoComplexMember |  |  |  |  |  |
Nonrecurring | North Battle Mountain Complex Located in Nevada, United States |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 1,921,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_NorthBattleMountainComplexLocatedInNevadaUnitedStatesMember |  |  |  |  |  |  |
Nonrecurring | MSC |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 21,162,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember | 95,878,000 us-gaap_AssetImpairmentCharges / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |  |  |  |  |
Nonrecurring | Total |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 454,134,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 262,490,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |  | 454,134,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |  | 262,490,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |  |
Nonrecurring | Total | Telken Tenements |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 26,442,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TelkenTenementsMember |  |  |  | 26,442,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TelkenTenementsMember |  |
Nonrecurring | Total | Other United States Properties |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 9,610,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_OtherUnitedStatesPropertiesMember |  |  |  | 9,610,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_OtherUnitedStatesPropertiesMember |  |
Nonrecurring | Total | Este Tenements |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 5,337,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_EsteTenementsMember |  |  |  | 5,337,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_EsteTenementsMember |  |
Nonrecurring | Total | Piramides Tenements |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 9,736,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_PiramidesTenementsMember |  |  |  | 9,736,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_PiramidesTenementsMember |  |
Nonrecurring | Total | Tobias Tenements |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 11,645,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TobiasTenementsMember |  |  |  | 11,645,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TobiasTenementsMember |  |
Nonrecurring | Total | Los Azules Copper Project |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 202,889,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember |  |  | 202,889,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember |  |  |  |
Nonrecurring | Total | Tonkin Complex |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 20,423,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TonkinComplexMember |  |  | 20,423,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TonkinComplexMember |  |  |  |
Nonrecurring | Total | Gold Bar Complex |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 51,577,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_GoldBarComplexMember |  |  | 51,577,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_GoldBarComplexMember |  |  |  |
Nonrecurring | Total | Limo Complex |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 23,438,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LimoComplexMember |  |  |  | 23,438,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LimoComplexMember |  |
Nonrecurring | Total | North Battle Mountain Complex Located in Nevada, United States |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 2,227,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_NorthBattleMountainComplexLocatedInNevadaUnitedStatesMember |  |  | 2,227,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_NorthBattleMountainComplexLocatedInNevadaUnitedStatesMember |  |  |  |
Nonrecurring | Total | MSC |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 177,018,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |  | 177,018,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Investment in MSC |  | 176,282,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |  |  | 176,282,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_EstimateOfFairValueFairValueDisclosureMember / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |
Nonrecurring | Level 3 |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 454,134,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember | 262,490,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |  | 454,134,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |  | 262,490,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember |  |
Nonrecurring | Level 3 | Telken Tenements |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 26,442,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TelkenTenementsMember |  |  |  | 26,442,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TelkenTenementsMember |  |
Nonrecurring | Level 3 | Other United States Properties |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 9,610,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_OtherUnitedStatesPropertiesMember |  |  |  | 9,610,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_OtherUnitedStatesPropertiesMember |  |
Nonrecurring | Level 3 | Este Tenements |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 5,337,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_EsteTenementsMember |  |  |  | 5,337,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_EsteTenementsMember |  |
Nonrecurring | Level 3 | Piramides Tenements |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 9,736,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_PiramidesTenementsMember |  |  |  | 9,736,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_PiramidesTenementsMember |  |
Nonrecurring | Level 3 | Tobias Tenements |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 11,645,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TobiasTenementsMember |  |  |  | 11,645,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TobiasTenementsMember |  |
Nonrecurring | Level 3 | Los Azules Copper Project |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 202,889,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember |  |  | 202,889,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember |  |  |  |
Nonrecurring | Level 3 | Los Azules Copper Project | Market Approach Valuation | Weighted Average |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Discount Rate (as a percent) | 35.00%us-gaap_FairValueInputsDiscountRate / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LosAzulesCopperProjectMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ValuationTechniqueAxis = us-gaap_MarketApproachValuationTechniqueMember |  |  |  |  |  |  |
Nonrecurring | Level 3 | Tonkin Complex |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 20,423,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TonkinComplexMember |  |  | 20,423,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_TonkinComplexMember |  |  |  |
Nonrecurring | Level 3 | Gold Bar Complex |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 51,577,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_GoldBarComplexMember |  |  | 51,577,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_GoldBarComplexMember |  |  |  |
Nonrecurring | Level 3 | Limo Complex |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets |  | 23,438,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LimoComplexMember |  |  |  | 23,438,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LimoComplexMember |  |
Nonrecurring | Level 3 | North Battle Mountain Complex Located in Nevada, United States |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 2,227,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_NorthBattleMountainComplexLocatedInNevadaUnitedStatesMember |  |  | 2,227,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_NorthBattleMountainComplexLocatedInNevadaUnitedStatesMember |  |  |  |
Nonrecurring | Level 3 | MSC |  |  |  |  |  |  |  |
Assets: |  |  |  |  |  |  |  |
Assets | 177,018,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |  | 177,018,000 us-gaap_AssetsFairValueDisclosure / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Investment in MSC |  | 176,282,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |  |  | 176,282,000 us-gaap_InvestmentsInAffiliatesSubsidiariesAssociatesAndJointVentures / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember |  |
Nonrecurring | Level 3 | MSC | Market Approach Valuation | Weighted Average | ARGENTINA |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Discount Rate (as a percent) | 20.00%us-gaap_FairValueInputsDiscountRate / mux_AllCountriesAxis = country_AR / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = us-gaap_MarketApproachValuationTechniqueMember |  |  |  |  |  |  |
Nonrecurring | Level 3 | MSC | Discounted Cash Flow | Weighted Average |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Discount Rate (as a percent) | 10.00%us-gaap_FairValueInputsDiscountRate / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = mux_DiscountedCashFlowApproachValuationTechniqueMember | 10.00%us-gaap_FairValueInputsDiscountRate / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = mux_DiscountedCashFlowApproachValuationTechniqueMember |  |  |  |  |  |
Long Term Gold Price (in dollars per ounce) | 1,300 mux_FairValueInputsLongTermGoldPricePerOunce / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = mux_DiscountedCashFlowApproachValuationTechniqueMember | 1,300 mux_FairValueInputsLongTermGoldPricePerOunce / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = mux_DiscountedCashFlowApproachValuationTechniqueMember |  |  |  |  |  |
Long Term Silver Price (in dollars per ounce) | 20.50 mux_FairValueInputsLongTermSilverPricePerOunce / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = mux_DiscountedCashFlowApproachValuationTechniqueMember | 22.75 mux_FairValueInputsLongTermSilverPricePerOunce / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = mux_DiscountedCashFlowApproachValuationTechniqueMember |  |  |  |  |  |
Nonrecurring | Level 3 | MSC | Discounted Cash Flow | Weighted Average | ARGENTINA |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Inflation index (as a percent) | 11.90%mux_FairValueInputsInflationIndex / mux_AllCountriesAxis = country_AR / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = mux_DiscountedCashFlowApproachValuationTechniqueMember | 10.00%mux_FairValueInputsInflationIndex / mux_AllCountriesAxis = country_AR / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = mux_DiscountedCashFlowApproachValuationTechniqueMember |  |  |  |  |  |
Nonrecurring | Level 3 | MSC | Discounted Cash Flow | Weighted Average | UNITED STATES |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Inflation index (as a percent) | 2.10%mux_FairValueInputsInflationIndex / mux_AllCountriesAxis = country_US / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = mux_DiscountedCashFlowApproachValuationTechniqueMember | 1.70%mux_FairValueInputsInflationIndex / mux_AllCountriesAxis = country_US / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = mux_DiscountedCashFlowApproachValuationTechniqueMember |  |  |  |  |  |
Nonrecurring | Level 3 | MSC | La Merced Tenements | Market Approach Valuation | Weighted Average |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Discount Rate (as a percent) |  | 40.00%us-gaap_FairValueInputsDiscountRate / us-gaap_FairValueByFairValueHierarchyLevelAxis = us-gaap_FairValueInputsLevel3Member / us-gaap_FairValueByMeasurementFrequencyAxis = us-gaap_FairValueMeasurementsNonrecurringMember / mux_MineralPropertyNameAxis = mux_LaMercedTenementsMember / us-gaap_RangeAxis = us-gaap_WeightedAverageMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = mux_MineraSantaCruzSAMember / us-gaap_ValuationTechniqueAxis = us-gaap_MarketApproachValuationTechniqueMember |  |  |  |  |  |
Nevada |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 98,400,000 us-gaap_AssetImpairmentCharges / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember |  |  |  |  |  |  |
Nevada | Other United States Properties |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 9,611,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_OtherUnitedStatesPropertiesMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember | 9,497,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_OtherUnitedStatesPropertiesMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember | 2,902,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_OtherUnitedStatesPropertiesMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember |  |  |  |  |
Nevada | Tonkin Complex |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 31,391,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_TonkinComplexMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember |  |  |  |  |  |  |
Nevada | Gold Bar Complex |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 25,435,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_GoldBarComplexMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember |  |  |  |  |  |  |
Nevada | Limo Complex |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 23,438,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_LimoComplexMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember | 19,450,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_LimoComplexMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember |  |  |  |  |  |
Nevada | North Battle Mountain Complex Located in Nevada, United States |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 1,921,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_NorthBattleMountainComplexLocatedInNevadaUnitedStatesMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember |  | 14,044,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_NorthBattleMountainComplexLocatedInNevadaUnitedStatesMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember |  |  |  |  |
Nevada | East Battle Mountain Complex Located in Nevada, United States |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 4,060,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_EastBattleMountainComplexLocatedInNevadaUnitedStatesMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember |  |  |  |  |  |  |
Nevada | West Battle Mountain Complex |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | 2,567,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_WestBattleMountainComplexLocatedInNevadaUnitedStatesMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember | 6,287,000 us-gaap_AssetImpairmentCharges / mux_MineralPropertyNameAxis = mux_WestBattleMountainComplexLocatedInNevadaUnitedStatesMember / us-gaap_SubsegmentsAxis = mux_NevadaSubsegmentMember |  |  |  |  |  |
Non-core Nevada |  |  |  |  |  |  |  |
Liabilities: |  |  |  |  |  |  |  |
Total Loss | $ 39,700,000 us-gaap_AssetImpairmentCharges / us-gaap_SubsegmentsAxis = mux_NonCoreNevadaMember |  |  |  |  |  |  |

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