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Note 12 - Share-based Compensation - Summary of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Feb. 28, 2025	Feb. 29, 2024
Share-based Compensation Expense	$ 983	$ 2,409
Share-Based Payment Arrangement, Option [Member]
Share-based Compensation Expense	459	1,322
Performance Share Units [Member]
Share-based Compensation Expense	454	1,027
Deferred Share Units [Member]
Share-based Compensation Expense	$ 70	$ 60

X

- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.F)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479830/718-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

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Balance Type:	debit
Period Type:	duration

X

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_AwardTypeAxis=ng_PerformanceShareUnitsMember
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X

- Details

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Period Type: