SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Products, Properties and Production of Minerals (Details)	12 Months Ended
Dec. 31, 2023
Maximum
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES.
Option to sell prior to the completion of refining (as a percent)	100.00%

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

No definition available.

Name:	mux_OptionToSellPriorToCompletionOfRefining
Namespace Prefix:	mux_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration