Percentage of equity method investment acquired.

No definition available.

Name:	ng_EquityMethodInvestmentPercentageAcquired
Namespace Prefix:	ng_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage amount of an equity method investment which has been sold.

+ References

No definition available.

+ Details

Name:	ng_EquityMethodInvestmentPercentageSold
Namespace Prefix:	ng_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents the transaction costs of investments accounted for under the equity method of accounting.

+ References

No definition available.

+ Details

Name:	ng_EquityMethodInvestmentTransactionCosts
Namespace Prefix:	ng_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the total number of directors on the board of an unconsolidated venture, including those selected by the reporting entity and/or the venture partner.

+ References

No definition available.

+ Details

Name:	ng_UnconsolidatedVenturesNumberOfDirectors
Namespace Prefix:	ng_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of directors on the board of unconsolidated ventures, which directors are selected by the reporting entity.

+ References

No definition available.

+ Details

Name:	ng_UnconsolidatedVenturesNumberOfDirectorsSelectedByTheReportingEntity
Namespace Prefix:	ng_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of directors on the board of unconsolidated ventures, which directors are selected by the reporting entity's venture partners.

+ References

No definition available.

+ Details

Name:	ng_UnconsolidatedVenturesNumberOfDirectorsSelectedByVenturePartners
Namespace Prefix:	ng_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the amount of working capital adjustment paid during the period.

+ References

No definition available.

+ Details

Name:	ng_WorkingCapitalAdjustment
Namespace Prefix:	ng_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(12))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_EquityMethodInvestmentAggregateCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Details

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

- Details

Name:	dei_LegalEntityAxis=ng_BarrickMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ng_NovaGoldResourcesAlaskaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=ng_DonlinGoldHoldingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 5 - Investment in Donlin Gold (Details Textual) - Donlin Gold [Member] $ in Thousands	Jun. 03, 2025 USD ($)	Jun. 02, 2025	May 31, 2025 USD ($)
Equity Method Investment, Aggregate Cost			$ 64,000
Equity Method Investment, Ownership Percentage	60.00%	50.00%	60.00%
Unconsolidated Ventures, Number of Directors	4
Unconsolidated Ventures, Number of Directors, Selected By the Reporting Entity	2
Barrick [Member]
Unconsolidated Ventures, Number of Directors Selected By Venture Partners	2
Barrick [Member]
Equity Method Investment, Percentage Sold	50.00%
Equity Method Investment, Aggregate Cost	$ 1,000,000
NovaGold Resources Alaska [Member]
Equity Method Investment, Aggregate Cost	$ 200,000
Equity Method Investment, Percentage Acquired	10.00%
Working Capital Adjustment	$ 980
Equity Method Investment, Transaction Costs	$ 9,070
Equity Method Investment, Ownership Percentage	60.00%
Donlin Gold Holdings [Member]
Equity Method Investment, Aggregate Cost	$ 800,000
Equity Method Investment, Percentage Acquired	40.00%
Equity Method Investment, Ownership Percentage	40.00%