Note 5 - Fair Value of Financial Instruments - Estimated Fair Value of Company's Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial assets:
Securities available for sale	$ 79,932	$ 79,980
Loans receivable, net	599,462	586,688
Reported Value Measurement [Member]
Financial assets:
Cash and cash equivalents	15,121	20,709
Securities available for sale	79,932	79,980
Loans held for sale	3,292	3,444
Loans receivable, net	599,462	578,978
Federal Home Loan Bank stock	853	867
Accrued interest receivable	2,326	2,356
Financial liabilities:
Deposits	626,592	617,722
Accrued interest payable	332	346
Off-balance sheet financial instruments:
Commitments to extend credit	99	40
Commitments to sell loans	(54)	(56)
Estimate of Fair Value Measurement [Member]
Financial assets:
Cash and cash equivalents	15,121	20,709
Securities available for sale	79,932
Loans held for sale	3,292
Loans receivable, net	593,230
Federal Home Loan Bank stock	853
Accrued interest receivable	2,326
Financial liabilities:
Deposits	620,967
Accrued interest payable	332
Off-balance sheet financial instruments:
Commitments to extend credit	99
Commitments to sell loans	(54)
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and cash equivalents	15,121
Securities available for sale		79,980
Loans held for sale		3,444
Loans receivable, net		578,978
Federal Home Loan Bank stock		867
Accrued interest receivable		2,356
Financial liabilities:
Deposits		617,722
Accrued interest payable		346
Off-balance sheet financial instruments:
Commitments to extend credit
Commitments to sell loans
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 2 [Member]
Financial assets:
Cash and cash equivalents
Securities available for sale	79,932
Loans held for sale	3,292
Loans receivable, net	593,230
Federal Home Loan Bank stock	853
Accrued interest receivable	2,326
Financial liabilities:
Deposits	620,967
Accrued interest payable	332
Off-balance sheet financial instruments:
Commitments to extend credit		146,978
Commitments to sell loans		$ 7,289
Estimate of Fair Value Measurement [Member] \| Fair Value, Inputs, Level 3 [Member]
Financial assets:
Cash and cash equivalents
Securities available for sale
Loans held for sale
Loans receivable, net
Federal Home Loan Bank stock
Accrued interest receivable
Financial liabilities:
Deposits
Accrued interest payable
Off-balance sheet financial instruments:
Commitments to extend credit	157,000
Commitments to sell loans	9,757
Portion at Other than Fair Value Measurement [Member]
Financial assets:
Cash and cash equivalents	20,709
Securities available for sale	79,980
Loans held for sale	3,444
Loans receivable, net	586,688
Federal Home Loan Bank stock	867
Accrued interest receivable	2,356
Financial liabilities:
Deposits	623,352
Accrued interest payable	346
Off-balance sheet financial instruments:
Commitments to extend credit	40
Commitments to sell loans	$ (56)

Fair value portion of accrued interest payable.

No definition available.

Name:	hmnf_AccruedInterestPayableFairValueDisclosure
Namespace Prefix:	hmnf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of accrued interest receivable.

+ References

No definition available.

+ Details

Name:	hmnf_AccruedInterestReceivableFairValueDisclosure
Namespace Prefix:	hmnf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The face amount of financial liabilities related to commitments to sell, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

No definition available.

+ Details

Name:	hmnf_FairValueDisclosureOffbalanceSheetRisksFaceAmountLiabilityCommitmentsToSellLoans
Namespace Prefix:	hmnf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	hmnf_OffbalanceSheetFinancialInstrumentsAbstract
Namespace Prefix:	hmnf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

No definition available.

+ Details

Name:	us-gaap_CashAndCashEquivalentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of deposit liabilities held by the entity, including, but not limited to, foreign and domestic, interest and noninterest bearing, demand deposits, saving deposits, negotiable orders of withdrawal (NOW) and time deposits.

+ References

No definition available.

+ Details

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

- Definition

The face amount of financial assets, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueDisclosureOffbalanceSheetRisksFaceAmountAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Fair value portion of investments in Federal Home Loan Bank (FHLBank) stock.

+ References

No definition available.

+ Details

Name:	us-gaap_InvestmentInFederalHomeLoanBankStockFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LoansAndLeasesReceivableNetReportedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

+ References

No definition available.

+ Details

Name:	us-gaap_LoansHeldForSaleFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_CarryingReportedAmountFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_PortionAtOtherThanFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: