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STOCK BASED COMPENSATION (Details)
 12 Months Ended
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Dec. 31, 2012
USD ($)
Dec. 31, 2011
USD ($)
Dec. 31, 2013
Minimum
Dec. 31, 2014
Maximum
Dec. 31, 2013
Maximum
Dec. 31, 2012
Maximum
Dec. 31, 2014
Minera Andes
CAD
Dec. 31, 2013
Minera Andes
CAD
Dec. 31, 2014
Certain employees and directors
USD ($)
Dec. 31, 2013
Certain employees and directors
USD ($)
Dec. 31, 2012
Certain employees and directors
USD ($)
Dec. 31, 2012
Certain employees and directors
Minimum
Dec. 31, 2012
Certain employees and directors
Maximum
STOCK BASED COMPENSATION                              
Number of shares of common stock reserved for issuance 13,500,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized                            
Maximum number of shares that may be subject to grants of options to an individual in a calendar year 1,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumNumberOfSharesPerEmployee                            
Shares                              
Balance at the beginning of the period (in shares) (4,841,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 3,561,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 3,870,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber                        
Stock options granted (in shares) 1,731,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 1,728,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross               1,700,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		 1,700,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		 300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		    
Exercised (in shares) (1,499,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised (48,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised (445,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised           (198,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_BusinessAcquisitionAxis
= mux_MineraAndesIncMember		 (45,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_BusinessAcquisitionAxis
= mux_MineraAndesIncMember		          
Forfeited (in shares) (422,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod (400,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod (128,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod                        
Expired (in shares)     (36,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod                        
Balance at the end of the period (in shares) 4,650,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber (4,841,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 3,561,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 3,870,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber                      
Exercisable at the end of the period (in shares) 1,954,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber                            
Weighted Average Exercise Price                              
Balance at the beginning of the period (in dollars per share) $ 2.96us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 3.47us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 3.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice                        
Granted (in dollars per share) $ 2.90us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice $ 2.30us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice $ 5.80us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice               $ 2.90us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		 $ 2.26us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		 $ 5.80us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		    
Exercised (in dollars per share) $ 1.29us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice $ 1.97us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice $ 1.84us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice           1.96us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_BusinessAcquisitionAxis
= mux_MineraAndesIncMember		 1.80us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_BusinessAcquisitionAxis
= mux_MineraAndesIncMember		          
Forfeited (in dollars per share) $ 4.39us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice $ 4.57us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice $ 6.27us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice                        
Expired (in dollars per share)     $ 7.96us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice                        
Balance at the end of the period (in dollars per share) $ 3.35us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 2.96us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 3.47us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 3.24us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice                      
Exercisable (in dollars per share) $ 4.12us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice                            
Weighted Average Remaining Contractual Life                              
Outstanding at the end of the period 4 years 4 months 24 days 5 years 2 months 12 days 6 years 7 months 6 days 7 years 3 months 18 days                      
Exercisable period of options 4 years 6 months                            
Intrinsic Value                              
Exercised (in dollars) $ 438,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue $ 47,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue $ 596,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue                        
Outstanding at the end of the period (in dollars) 11,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue                            
Exercisable at the end of the period (in dollars) 11,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1                            
Granted (in shares) 1,731,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 1,728,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross 300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross               1,700,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		 1,700,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		 300,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		    
Exercise price of options granted (in dollars per share) $ 2.90us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice $ 2.30us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice $ 5.80us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice               $ 2.90us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		 $ 2.26us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		 $ 5.80us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= mux_EmployeesAndDirectorsMember		    
Vesting period of options                     3 years        
Exercise period of options                     5 years     5 years 10 years
Principal assumptions used in applying the Black-Scholes option pricing model for the awards                              
Risk-free interest rate (as a percent)         0.50%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		 1.01%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 0.86%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 0.97%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		              
Volatility factor of the expected market price of common stock (as a percent)         66.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		 70.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 69.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		 75.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		              
Weighted-average expected life of option 3 years 6 months 6 years 6 years 7 months 6 days                        
Weighted-average grant date fair value (in dollars per share) $ 1.45us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 1.02us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 3.80us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue                        
Stock option expense 1,300,000us-gaap_AllocatedShareBasedCompensationExpense 1,400,000us-gaap_AllocatedShareBasedCompensationExpense 3,400,000us-gaap_AllocatedShareBasedCompensationExpense                        
Additional disclosures                              
Unrecognized compensation expense on non-vested stock options (in dollars) $ 1,800,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions $ 1,100,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions                          
Non-vested stock options outstanding (in shares) 2,700,000mux_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptionsNumber 2,000,000mux_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptionsNumber                          
Weighted-average period of recognition 1 year 7 months 6 days 1 year 4 months 24 days