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v3.25.2

The Company incurred lease costs as follows: (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Jun. 30, 2025 | Jun. 30, 2024
Leases |  |
Fixed rent expense | $ 94 | $ 90
Variable rent expense | 13 | 14
Short term lease cost | 10 | 9
Sublease income | (41) | (32)
Net lease cost – other operating expense | $ 76 | $ 81

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- References No definition available. + Details
Name: | niobf_DisclosureLeasesAbstract
Namespace Prefix: | niobf_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition The element represents fixed rent expense. + References No definition available. + Details
Name: | niobf_FixedRentExpense
Namespace Prefix: | niobf_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of lease cost recognized by lessee for lease contract. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 53 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479589/842-20-55-53 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-4 + Details
Name: | us-gaap_LeaseCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of short-term lease cost, excluding expense for lease with term of one month or less. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 53 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479589/842-20-55-53 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-4 + Details
Name: | us-gaap_ShortTermLeaseCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of sublease income excluding finance and operating lease expense. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 53 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479589/842-20-55-53 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-4 + Details
Name: | us-gaap_SubleaseIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Amount of variable lease cost, excluded from lease liability, recognized when obligation for payment is incurred for finance and operating leases. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 53 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479589/842-20-55-53 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 842 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478964/842-20-50-4 + Details
Name: | us-gaap_VariableLeaseCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration