LONG-TERM DEBT (Details) - Term Loan - Gold Bar Complex $ in Millions	Dec. 31, 2019 USD ($)
Scheduled minimum interest payments
2020	$ 4.7
2021	$ 2.0

Amount of long-term debt interest payable for remainder in the second fiscal year.

No definition available.

Name:	mux_LongTermDebtMaturitiesRepaymentsOfInterestInYearTwo
Namespace Prefix:	mux_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant