Note 9 - Allowance for Loan Losses and Credit Quality Information - Financial Effects of Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Number of Contracts	1	2	7	15
Pre- modification Outstanding Recorded Investment	$ 58	$ 2	$ 294	$ 2,032
Post- modification Outstanding Recorded Investment	$ 58	$ 2	$ 299	$ 2,036
Residential Portfolio Segment [Member]
Number of Contracts	0	0	3	1
Pre- modification Outstanding Recorded Investment	$ 0	$ 0	$ 176	$ 55
Post- modification Outstanding Recorded Investment	$ 0	$ 0	$ 181	$ 58
Consumer Portfolio Segment [Member]
Number of Contracts	1	2	4	10
Pre- modification Outstanding Recorded Investment	$ 58	$ 2	$ 118	$ 335
Post- modification Outstanding Recorded Investment	$ 58	$ 2	$ 118	$ 336
Commercial Real Estate Portfolio Segment [Member] \| Real Estate Loan [Member]
Number of Contracts		0		1
Pre- modification Outstanding Recorded Investment		$ 0		$ 54
Post- modification Outstanding Recorded Investment		$ 0		$ 54
Commercial Real Estate Portfolio Segment [Member] \| Commercial Real Estate Other [Member]
Number of Contracts		0		2
Pre- modification Outstanding Recorded Investment		$ 0		$ 1,518
Post- modification Outstanding Recorded Investment		$ 0		$ 1,518
Commercial Portfolio Segment [Member]
Number of Contracts		0		1
Pre- modification Outstanding Recorded Investment		$ 0		$ 70
Post- modification Outstanding Recorded Investment		$ 0		$ 70

Number of financing receivables that have been modified by troubled debt restructurings.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_RealEstateLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=hmnf_CommercialRealEstateOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: