NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2) (Gold equivalents, El Gallo mine)	3 Months Ended	9 Months Ended	12 Months Ended	13 Months Ended
Sep. 30, 2013 oz	Sep. 30, 2013 oz	Dec. 31, 2012 oz	Sep. 30, 2013 oz
Gold equivalents \| El Gallo mine
Nature of Operations and Basis of Presentation
Quantity produced (in ounces)	8,027	23,370	6,949	30,319

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

No definition available.

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