Note 20 - Fair Value Measurement - Assets Measured at Fair Value on Nonrecurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Loans held for sale, Total gains (losses)	$ (40)	$ 45
Mortgage servicing rights, net, Total gains (losses)	0	0
Impaired loans, Total gains (losses)	(28)	(97)
Real estate, net, Total gains (losses)	0	0
Total, Total gains (losses)	(68)	(52)
Fair Value, Nonrecurring [Member]
Loans held for sale	3,606	3,444
Mortgage servicing rights, net	2,172	1,855
Impaired loans	3,126	2,902
Real estate, net	580	414
Total	9,484	8,615
Fair Value, Nonrecurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Loans held for sale	0	0
Mortgage servicing rights, net	0	0
Impaired loans	0	0
Real estate, net	0	0
Total	0	0
Fair Value, Nonrecurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Loans held for sale	3,606	3,444
Mortgage servicing rights, net	2,172	1,855
Impaired loans	3,126	2,902
Real estate, net	580	414
Total	9,484	8,615
Fair Value, Nonrecurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Loans held for sale	0	0
Mortgage servicing rights, net	0	0
Impaired loans	0	0
Real estate, net	0	0
Total	$ 0	$ 0

Represents the amount of gain (loss) on fair value adjustments of loans during the period.

No definition available.

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

Represents the amount of gain (loss) on fair value adjustments of loans held for sale during the period.

+ References

No definition available.

+ Details

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- Definition

Represents the amount of gain (loss) on fair value adjustments of mortgage servicing rights during the period.

+ References

No definition available.

+ Details

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- Definition

Represents the amount of gain (loss) on fair value adjustments of repossessed assets during the period.

+ References

No definition available.

+ Details

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Namespace Prefix:	hmnf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the fair value portion of loans receivable adjustments based on appraised value of collateral.

+ References

No definition available.

+ Details

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Namespace Prefix:	hmnf_
Data Type:	xbrli:monetaryItemType
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- Definition

Represents the fair value portion of repossessed assets.

+ References

No definition available.

+ Details

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of gain (loss) from the difference between the sale price or salvage price and the book value of an asset that was sold or retired, and gain (loss) from the write down of assets from their carrying value to fair value.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6469459&loc=d3e122501-111745

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122625-111746

+ Details

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Period Type:	instant

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