v3.25.2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - AAA Arbitration Final Award (Details)			1 Months Ended
	Oct. 04, 2024 USD ($)	Sep. 06, 2024 USD ($)	Mar. 31, 2024 item
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Number of members on panel for arbitration \| item			3
Litigation settlement, amount		$ 59,799,977
Litigation settlement, interest		$ (11,385,052)
Litigation settlement, percentage		10.00%
Arbitration award	$ 71,185,029

The number of members appointed to the panel for arbitration.

+ References

No definition available.

+ Details

Name:	msb_ArbitrationNumberOfMembersOnPanel
Namespace Prefix:	msb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage for calculation of interest for litigation settlement award.

+ References

No definition available.

+ Details

Name:	msb_LitigationSettlementInterestPercentage
Namespace Prefix:	msb_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Amount awarded from other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

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

- Definition

Amount of gain from litigation settlement for amount awarded from other party. Excludes claims within an insurance entity's normal claims settlement process.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483049/450-30-50-1

+ Details

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

- Definition

Interest expense (income) directly attributable to an award in settlement of litigation.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(6))
-SubTopic 10
-Topic 220
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

+ Details

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

MESABI TRUST 10-Q