BORROWINGS (Details) - CAD ($) $ in Thousands	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023
BORROWINGS
Opening balance	$ 1,758	$ 1,988
Repayments	(744)	(282)
Interest		52
Ending balance	1,014	1,758
Current portion	250	480
Non-current portion	$ 764	$ 1,278

The amount of outstanding funds that the entity is obligated to repay.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2024-01-01
-Paragraph 55
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_55&doctype=Standard
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_Borrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	ifrs-full_BorrowingsAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The current portion of non-current borrowings. [Refer: Borrowings]

+ References

+ Details

Name:	ifrs-full_CurrentPortionOfLongtermBorrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The non-current portion of non-current borrowings. [Refer: Borrowings]

+ References

+ Details

Name:	ifrs-full_LongtermBorrowings
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash outflow to settle borrowings, classified as financing activities. [Refer: Borrowings]

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 7
-IssueDate 2024-01-01
-Paragraph 17
-Subparagraph d
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=7&code=ifrs-tx-2024-en-r&anchor=para_17_d&doctype=Standard
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_RepaymentsOfBorrowingsClassifiedAsFinancingActivities
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of interest capitalized on borrowings.

+ References

No definition available.

+ Details

Name:	nmg_InterestCapitalizedBorrowings
Namespace Prefix:	nmg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration