The element represents capital loss caryforward.

No definition available.

Name:	niobf_CapitalLossCaryforward
Namespace Prefix:	niobf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible loss carryforwards, classified as other.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-6

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-2

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
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-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-Paragraph 12
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of current and deferred federal tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, current and deferred national tax expense (benefit) for non-US (United States of America) jurisdiction.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
-Name Accounting Standards Codification
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-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-10

+ Details

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

- Details

Name:	srt_CurrencyAxis=currency_CAD
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_DomesticCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

INCOME TAXES (Details Narrative) - USD ($) $ in Thousands	12 Months Ended
INCOME TAXES (Details Narrative) - USD ($) $ in Thousands	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2019	Jun. 30, 2018
Effective Income Tax Rate Reconciliation [Line Items]
Federal Income Tax Expense (Benefit), Continuing Operations	$ 443
Valuation allowance	$ 28,181	$ 32,159
Canada, Dollars
Effective Income Tax Rate Reconciliation [Line Items]
Net operating loss carryforwards		3,378
Domestic Tax Jurisdiction [Member]
Effective Income Tax Rate Reconciliation [Line Items]
Tax losses incurred			$ 5,645	$ 981
Net operating loss carryforwards		$ 8,742