Note 14 - Net Change in Operating Assets and Liabilities - Net Change in Operating Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
Feb. 29, 2024	Feb. 28, 2023
Other assets	$ (925)	$ (179)
Accounts payable and accrued liabilities	(137)	(250)
Accrued payroll and related benefits	(1,881)	(1,890)
Remediation	(48)	(7)
Increase (Decrease) in Operating Capital	$ (2,991)	$ (2,326)

The increase (decrease) during the reporting period in remediation liability.

No definition available.

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

- Definition

The increase (decrease) during the reporting period in the amounts payable to vendors for goods and services received and the amount of obligations and expenses incurred but not paid.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (a)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-28

+ Details

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

- Definition

The increase (decrease) during the reporting period in the aggregate amount of obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits.

+ References

+ Details

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

- Definition

The increase (decrease) during the reporting period of all assets and liabilities used in operating activities.

+ References

+ Details

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

- Definition

Amount of increase (decrease) in operating assets classified as other.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration