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, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Number of Contracts	2	7	15	17
Pre- modification Outstanding Recorded Investment	$ 2	$ 520	$ 2,032	$ 1,160
Post- modification Outstanding Recorded Investment	$ 2	$ 221	$ 2,036	$ 1,095
Residential Portfolio Segment [Member]
Number of Contracts	0	0	1	3
Pre- modification Outstanding Recorded Investment	$ 0	$ 0	$ 55	$ 282
Post- modification Outstanding Recorded Investment	$ 0	$ 0	$ 58	$ 514
Consumer Portfolio Segment [Member]
Number of Contracts	2	6	10	13
Pre- modification Outstanding Recorded Investment	$ 2	$ 104	$ 335	$ 462
Post- modification Outstanding Recorded Investment	$ 2	$ 105	$ 336	$ 465
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	1	1
Pre- modification Outstanding Recorded Investment	$ 0	$ 416	$ 70	$ 416
Post- modification Outstanding Recorded Investment	$ 0	$ 116	$ 70	$ 116

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

+ Details

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

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

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

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ 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: