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Note 5 - Investment in Donlin Gold (Details Textual) - Donlin Gold [Member] $ in Millions | Nov. 30, 2023 USD ($)
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Equity Method Investment, Ownership Percentage | 50.00%
Unconsolidated Ventures, Number of Directors | 4
Unconsolidated Ventures, Number of Directors, Selected By the Reporting Entity | 2
Equity Method Investment, Aggregate Cost | $ 64
Barrick [Member] |
Unconsolidated Ventures, Number of Directors Selected By Venture Partners | 2
Barrick [Member] |
Equity Method Investment, Ownership Percentage | 50.00%

X
- 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

X
- 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

X
- 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
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Namespace Prefix: | ng_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- 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 -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- 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 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
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- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=ng_DonlinGoldMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CounterpartyNameAxis=ng_BarrickMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=ng_BarrickMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |