Note 5 - Loans and Other Real Estate Owned ("OREO") - Reconciliation of Purchase Price to Par Value (Details) - Northumberland Bancorp [Member] - USD ($) $ in Thousands	Dec. 31, 2025	Aug. 01, 2025
Purchase (Premium) Discount		$ 19,200
Financial Asset Acquired and No Credit Deterioration [Member]
Par value		392,745
N N B [Member]
Par Value		53,676
Purchase (Premium) Discount		(2,157)
Allowance		725
Purchase Price	$ 52,245	52,244
Adjustments	1
N N B [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Par value		392,745
Purchase (Premium) Discount		(17,870)
Purchase Price	374,978	374,875
Adjustments	103
Commercial Portfolio Segment [Member] \| N N B [Member]
Par Value		18,083
Purchase (Premium) Discount		(891)
Allowance		423
Purchase Price	17,615	17,615
Adjustments	0
Commercial Portfolio Segment [Member] \| N N B [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Par value		67,002
Purchase (Premium) Discount		(4,645)
Purchase Price	62,357	62,357
Adjustments	0
Commercial Real Estate Portfolio Segment [Member] \| N N B [Member]
Par Value		14,180
Purchase (Premium) Discount		(860)
Allowance		114
Purchase Price	13,434	13,434
Adjustments	0
Commercial Real Estate Portfolio Segment [Member] \| N N B [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Par value		82,855
Purchase (Premium) Discount		(4,944)
Purchase Price	77,911	77,911
Adjustments	0
Residential Portfolio Segment [Member] \| N N B [Member] \| Real Estate Loan [Member]
Par Value		20,073
Purchase (Premium) Discount		(437)
Allowance		178
Purchase Price	19,814	19,814
Adjustments	0
Residential Portfolio Segment [Member] \| N N B [Member] \| Home Equity Loan [Member]
Par Value		1,077
Purchase (Premium) Discount		48
Allowance		7
Purchase Price	1,133	1,132
Adjustments	1
Residential Portfolio Segment [Member] \| N N B [Member] \| Financial Asset Acquired and No Credit Deterioration [Member] \| Real Estate Loan [Member]
Par value		209,109
Purchase (Premium) Discount		(7,169)
Purchase Price	201,940	201,940
Adjustments	0
Residential Portfolio Segment [Member] \| N N B [Member] \| Financial Asset Acquired and No Credit Deterioration [Member] \| Home Equity Loan [Member]
Par value		28,180
Purchase (Premium) Discount		(971)
Purchase Price	27,312	27,209
Adjustments	103
Consumer Portfolio Segment [Member] \| N N B [Member] \| Consumer, Other [Member]
Par Value		263
Purchase (Premium) Discount		(17)
Allowance		3
Purchase Price	249	249
Adjustments	0
Consumer Portfolio Segment [Member] \| N N B [Member] \| Financial Asset Acquired and No Credit Deterioration [Member] \| Consumer, Other [Member]
Par value		5,599
Purchase (Premium) Discount		(141)
Purchase Price	5,458	$ 5,458
Adjustments	$ 0

The discount (premium) on the acquired receivables.

No definition available.

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Namespace Prefix:	miff_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The purchase price of the acquired receivables.

+ References

No definition available.

+ Details

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Namespace Prefix:	miff_
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Balance Type:	debit
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- Definition

Adjustments to the purchase price of the acquired receivables.

+ References

No definition available.

+ Details

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Namespace Prefix:	miff_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The adjustments to the amount at purchase price of financing receivable purchased with credit deterioration.

+ References

No definition available.

+ Details

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Namespace Prefix:	miff_
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- Definition

Amount of gross contractual receivable purchased without credit deterioration, acquired in business combination. Excludes purchased financial asset with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479907/805-20-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479907/805-20-50-1

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- Definition

Amount of allowance for credit loss at acquisition date of financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 19
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-19

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Balance Type:	credit
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- Definition

Amount at par value of financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 19
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-19

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Amount at purchase price of financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 19
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-19

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Balance Type:	debit
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- Definition

Amount of discount (premium) attributable to other factors on financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 19
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-19

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