Tabular disclosure of the changes in carrying amount of a liability for asset retirement obligations, for changes such as new obligations, changes in estimates of existing obligations, spending on existing obligations, property dispositions, and foreign currency translation.

No definition available.

Name:	nmg_IfrsScheduleOfChangeInAssetRetirementObligationTableTextBlock
Namespace Prefix:	nmg_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration