Investments - Narrative (Details) $ in Millions	12 Months Ended
Dec. 31, 2025 USD ($) investment	Dec. 31, 2024 USD ($) investment
Net Investment Income [Line Items]
Investment grade rating	98.00%
Number of limited partnership investments \| investment		2
Number of limited partnership investments sold \| investment	2
Reverse repurchase agreement, cash to value percentage	95.00%
Securities sold under agreements to repurchase	$ 0.0	$ 12.0
Fair Value	5,714.6	5,387.9
FHLB funding agreements	1,039.5	989.5
FHLB of Chicago
Net Investment Income [Line Items]
Fair Value	1,107.1	1,072.2
Governmental agencies as required by law in various states
Net Investment Income [Line Items]
Fair Value	26.3	27.1
Fair Value
Net Investment Income [Line Items]
Securities sold under agreements to repurchase	0.0	12.4
Fair Value	$ 5,714.6	$ 5,387.9

Represents the federal home loan bank funding agreements.

No definition available.

Name:	hmn_FederalHomeLoanBankFundingAgreements
Namespace Prefix:	hmn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage of fair value of fixed maturity and equity securities with a gross unrealized loss having an investment grade rating at period end.

+ References

No definition available.

+ Details

Name:	hmn_InvestmentGradeRate
Namespace Prefix:	hmn_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Limited Partnership Investments

+ References

No definition available.

+ Details

Name:	hmn_NumberOfLimitedPartnershipInvestments
Namespace Prefix:	hmn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Limited Partnership Investments Sold

+ References

No definition available.

+ Details

Name:	hmn_NumberOfLimitedPartnershipInvestmentsSold
Namespace Prefix:	hmn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Reverse Repurchase Agreement, Cash To Value Percentage

+ References

No definition available.

+ Details

Name:	hmn_ReverseRepurchaseAgreementCashToValuePercentage
Namespace Prefix:	hmn_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(2)(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

+ Details

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

- Definition

Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 20
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-20

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-15

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483444/210-20-55-10

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 210
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483466/210-20-50-3

Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.12-12A(Column A)(Footnote 2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-12(Column A)(Footnote 2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 6
-Subparagraph (SX 210.12-14(Column A)(Footnote 2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-6

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 320
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-12B(Column A)(Footnote 4)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(m)(1)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(m)(1)(ii)(A)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

+ Details

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

- Details

Name:	srt_FederalHomeLoanBankAdvancesBranchOfFHLBBankAxis=hmn_FederalHomeLoansBankOfChicagoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=hmn_GovernmentalAgenciesAsRequiredByLawInVariousStatesMember
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: