v3.25.3

The change in the 2023 Private Warrants liability is presented below: (Details) - Note Warrant [Member] $ in Thousands	3 Months Ended
	Sep. 30, 2025 USD ($)
Subsidiary, Sale of Stock [Line Items]
Fair value as of June 30, 2025	$ 2,532
Fair value adjustment for warrants exchanged	1,217
Exchange of warrants	(2,501)
Change in fair value	3,039
Fair value as of September 30, 2025	$ 4,287

The element represents changes in fair value of initial valuation1.

+ References

No definition available.

+ Details

Name:	niobf_ChangesInFairValueOfInitialValuation1
Namespace Prefix:	niobf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The element represents exchange of warrants.

+ References

No definition available.

+ Details

Name:	niobf_ExchangeOfWarrants
Namespace Prefix:	niobf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of expense (income) related to adjustment to fair value of warrant liability.

+ References

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

+ Details

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

- Definition

Amount of increase (decrease) in fair value from changes in the inputs used to calculate the fair value of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(4)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481229/860-50-50-3

+ Details

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

- 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

No definition available.

+ Details

Name:	us-gaap_SubsidiarySaleOfStockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_SubsidiarySaleOfStockAxis=us-gaap_NoteWarrantMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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