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Note 15 - Supplemental Cash Flow Information (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Feb. 28, 2025	Feb. 29, 2024
Proceeds from Sale, Maturity and Collection of Investments	$ 952	$ 0
Filo Corporation [Member] | BHP Investments Canada Inc. and Lundin [Member]
Proceeds from Sale, Maturity and Collection of Investments	$ 952
Filo Corporation [Member] | BHP Investments Canada Inc. and Lundin [Member] | Lundin Stock [Member]
Investment Owned, Shares Received as Consideration	19,688

X

- Definition

Number of shares received as consideration for sale of investment.

+ References

No definition available.

+ Details

Name:	ng_InvestmentOwnedSharesReceivedAsConsideration
Namespace Prefix:	ng_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The cash inflow associated with the sale, maturity and collection of all investments such as debt, security and so forth during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-12

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=ng_FiloCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_CounterpartyNameAxis=ng_BHPInvestmentsCanadaIncAndLundinMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FinancialInstrumentAxis=ng_LundinStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: