Average date to calculate variable rate under debt instrument.

No definition available.

Name:	miff_DebtInstrumentVariableRateAverageDay
Namespace Prefix:	miff_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
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+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-SubTopic 470
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicates type of variable interest rate on debt instrument.

+ References

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Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of maximum advances or credit lines available from the Federal Home Loan Bank (FHLB).

+ References

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-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SubordinatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 7 - Borrowings and Subordinated Debt (Details Textual) $ in Millions		1 Months Ended
	Jul. 01, 2026	Jun. 30, 2022 USD ($)	Sep. 30, 2025 USD ($)
Forecast [Member]
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]	Secured Overnight Financing Rate (SOFR) [Member]
Subordinated Debt [Member]
Debt Instrument, Face Amount		$ 10
Debt Instrument, Term (Year)		10 years
Debt Instrument, Interest Rate, Stated Percentage		4.50%
Debt Instrument, Interest Rate, Effective Percentage			4.70%
Subordinated Debt [Member] \| Forecast [Member]
Debt Instrument, Variable Rate, Average Day	90
Debt Instrument, Basis Spread on Variable Rate	3.82%
Debt Instrument, Redemption Price, Percentage	100.00%
Federal Home Loan Bank of Pittsburgh [Member]
Federal Home Loan Bank, Advances, General Debt Obligations, Maximum Amount Available			$ 472