Represents the adjusted threshold price per ton as per the collaborative agreement.

No definition available.

Name:	msb_CollaborativeArrangementAdjustedThresholdPricePerTon
Namespace Prefix:	msb_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the minimum advance royalty to be received by the entity on a quarterly basis under the assignment agreement. This amount consists of an annual amount adjusted for inflation and deflation.

+ References

No definition available.

+ Details

Name:	msb_CollaborativeArrangementAdvanceRoyaltyThreshold
Namespace Prefix:	msb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the period within which the related party is obligated to make payments of overriding royalties on product shipments, following the calendar quarter in which such shipments occur, as per the collaborative agreement.

+ References

No definition available.

+ Details

Name:	msb_CollaborativeArrangementObligationToMakePaymentsOfOverridingRoyaltiesOnShipmentProductsPeriod
Namespace Prefix:	msb_
Data Type:	xbrli:durationItemType
Balance Type:	na
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 808
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479402/808-10-50-1

+ Details

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

- Details

Name:	dei_LegalEntityAxis=msb_CyprusNorthshoreMiningCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

ROYALTY AGREEMENT (Details)	12 Months Ended
ROYALTY AGREEMENT (Details)	Dec. 31, 2026 USD ($)	Jan. 31, 2026 USD ($) $ / T	Dec. 31, 2025 USD ($)	Jan. 31, 2025 $ / T	Jan. 31, 2024 $ / T
ROYALTY AGREEMENT
Adjusted threshold price (in dollars per ton)		71.7		69.41	67.75
Cyprus NMC
ROYALTY AGREEMENT
Adjusted threshold price (in dollars per ton)		71.7		69.41	67.75
Cyprus NMC \| Maximum
ROYALTY AGREEMENT
Period for payments of overriding royalties on product shipments		30 days
Cyprus NMC \| Minimum
ROYALTY AGREEMENT
Adjusted threshold price (in dollars per ton)		30
Advance royalty threshold \| $		$ 500,000	$ 1,157,261
Cyprus NMC \| Forecast \| Minimum
ROYALTY AGREEMENT
Advance royalty threshold \| $	$ 1,195,452