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Fair Value of Financial Instruments (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
U.S. Government and federally sponsored agency obligations:    
Carrying Amount $ 7,364,281us-gaap_AvailableForSaleSecurities $ 7,158,242us-gaap_AvailableForSaleSecurities
Fair Value 7,364,281hmn_AvailableForSaleSecuritiesFairValue 7,158,242hmn_AvailableForSaleSecuritiesFairValue
Investments, Carrying Amount 7,621,212us-gaap_Investments 7,403,467us-gaap_Investments
Investments, Fair Value 149,965us-gaap_InvestmentsFairValueDisclosure 149,792us-gaap_InvestmentsFairValueDisclosure
Separate Account (variable annuity) assets 1,865,240us-gaap_SeparateAccountAssets [1] 1,813,557us-gaap_SeparateAccountAssets [1]
Separate Account (variable annuity) assets, Fair Value 1,865,240hmn_SeparateAccountAssetsFairValueDisclosure [1] 1,813,557hmn_SeparateAccountAssetsFairValueDisclosure [1]
Recurring [Member]    
U.S. Government and federally sponsored agency obligations:    
Carrying Amount 7,065,799us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 6,893,090us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Fair Value 7,065,799hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 6,893,090hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Short-term investments [Member]    
U.S. Government and federally sponsored agency obligations:    
Investments, Carrying Amount 181,004us-gaap_Investments
/ us-gaap_InvestmentTypeAxis
= us-gaap_ShortTermInvestmentsMember		 142,039us-gaap_Investments
/ us-gaap_InvestmentTypeAxis
= us-gaap_ShortTermInvestmentsMember
Investments, Fair Value 181,004us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= us-gaap_ShortTermInvestmentsMember		 142,039us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_InvestmentTypeAxis
= us-gaap_ShortTermInvestmentsMember
Mortgage-backed securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Carrying Amount 541,360us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 535,726us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Fair Value 541,360hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 535,726hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Other, including U.S. Treasury Securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Carrying Amount 576,469us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherIncludingUsTreasurySecuritiesMember		 538,199us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherIncludingUsTreasurySecuritiesMember
Fair Value 576,469hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherIncludingUsTreasurySecuritiesMember		 538,199hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherIncludingUsTreasurySecuritiesMember
Municipal bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Carrying Amount 1,685,086us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MunicipalBondsMember		 1,647,822us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MunicipalBondsMember
Fair Value 1,685,086hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MunicipalBondsMember		 1,647,822hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MunicipalBondsMember
Foreign government bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Carrying Amount 65,081us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember		 59,536us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember
Fair Value 65,081hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember		 59,536hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember
Corporate bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Carrying Amount 2,841,062us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 2,834,749us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Fair Value 2,841,062hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 2,834,749hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Other mortgage-backed securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Carrying Amount 1,356,741us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesOtherMember		 1,277,058us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesOtherMember
Fair Value 1,356,741hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesOtherMember		 1,277,058hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesOtherMember
Equity securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Carrying Amount 105,066us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 110,655us-gaap_AvailableForSaleSecurities
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Fair Value 105,066hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 110,655hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Other Investment [Member]    
U.S. Government and federally sponsored agency obligations:    
Investments, Carrying Amount 12,412us-gaap_Investments
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherInvestmentMember		 12,458us-gaap_Investments
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherInvestmentMember
Investments, Fair Value 12,412us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherInvestmentMember		 12,458us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherInvestmentMember
Other Policyholders Funds, embedded derivatives [Member] | Recurring [Member]    
U.S. Government and federally sponsored agency obligations:    
Financial Liabilities Other policyholders funds, embedded derivatives, Fair Value 22,040us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherPolicyholdersFundsEmbeddedDerivativesMember		 20,049us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherPolicyholdersFundsEmbeddedDerivativesMember
Financial Liabilities Other policyholders funds, embedded derivatives, Carrying Value 22,040hmn_FinancialLiabilitiesCarryingValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherPolicyholdersFundsEmbeddedDerivativesMember		 20,049hmn_FinancialLiabilitiesCarryingValue
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherPolicyholdersFundsEmbeddedDerivativesMember
Level 1 [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 299,715hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 262,560hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Investments, Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Separate Account (variable annuity) assets, Fair Value 1,865,240hmn_SeparateAccountAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 [1] 1,813,557hmn_SeparateAccountAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member		 [1]
Level 1 [Member] | Recurring [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 28,364hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 28,381hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Level 1 [Member] | Short-term investments [Member]    
U.S. Government and federally sponsored agency obligations:    
Investments, Fair Value 181,004us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_ShortTermInvestmentsMember		 142,039us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_ShortTermInvestmentsMember
Level 1 [Member] | Mortgage-backed securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Level 1 [Member] | Other, including U.S. Treasury Securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 17,995hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherIncludingUsTreasurySecuritiesMember		 17,857hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherIncludingUsTreasurySecuritiesMember
Level 1 [Member] | Municipal bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MunicipalBondsMember		 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MunicipalBondsMember
Level 1 [Member] | Foreign government bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember		 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember
Level 1 [Member] | Corporate bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 10,369hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 10,524hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Level 1 [Member] | Other mortgage-backed securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesOtherMember		 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesOtherMember
Level 1 [Member] | Equity securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 90,347hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 92,140hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Level 1 [Member] | Other Investment [Member]    
U.S. Government and federally sponsored agency obligations:    
Investments, Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherInvestmentMember		 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherInvestmentMember
Level 1 [Member] | Other Policyholders Funds, embedded derivatives [Member] | Recurring [Member]    
U.S. Government and federally sponsored agency obligations:    
Financial Liabilities Other policyholders funds, embedded derivatives, Fair Value 0us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherPolicyholdersFundsEmbeddedDerivativesMember		 0us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherPolicyholdersFundsEmbeddedDerivativesMember
Level 2 [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 6,905,803hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 6,724,382hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Investments, Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Separate Account (variable annuity) assets, Fair Value 0hmn_SeparateAccountAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 [1] 0hmn_SeparateAccountAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member		 [1]
Level 2 [Member] | Recurring [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 6,878,678hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 6,693,415hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Level 2 [Member] | Short-term investments [Member]    
U.S. Government and federally sponsored agency obligations:    
Investments, Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_ShortTermInvestmentsMember		 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_ShortTermInvestmentsMember
Level 2 [Member] | Mortgage-backed securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 541,360hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 535,726hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Level 2 [Member] | Other, including U.S. Treasury Securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 558,474hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherIncludingUsTreasurySecuritiesMember		 520,342hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherIncludingUsTreasurySecuritiesMember
Level 2 [Member] | Municipal bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 1,671,201hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MunicipalBondsMember		 1,634,194hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MunicipalBondsMember
Level 2 [Member] | Foreign government bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 65,081hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember		 59,536hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember
Level 2 [Member] | Corporate bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 2,758,415hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 2,749,508hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Level 2 [Member] | Other mortgage-backed securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 1,284,147hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesOtherMember		 1,194,109hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesOtherMember
Level 2 [Member] | Equity securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 14,713hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 18,509hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Level 2 [Member] | Other Investment [Member]    
U.S. Government and federally sponsored agency obligations:    
Investments, Fair Value 12,412us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherInvestmentMember		 12,458us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherInvestmentMember
Level 2 [Member] | Other Policyholders Funds, embedded derivatives [Member] | Recurring [Member]    
U.S. Government and federally sponsored agency obligations:    
Financial Liabilities Other policyholders funds, embedded derivatives, Fair Value 0us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherPolicyholdersFundsEmbeddedDerivativesMember		 0us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherPolicyholdersFundsEmbeddedDerivativesMember
Level 3 [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 158,763hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 171,300hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Investments, Fair Value 149,965us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 149,792us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Separate Account (variable annuity) assets, Fair Value 0hmn_SeparateAccountAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 [1] 0hmn_SeparateAccountAssetsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member		 [1]
Level 3 [Member] | Recurring [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 158,757hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember		 171,294hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
Level 3 [Member] | Short-term investments [Member]    
U.S. Government and federally sponsored agency obligations:    
Investments, Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_ShortTermInvestmentsMember		 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_InvestmentTypeAxis
= us-gaap_ShortTermInvestmentsMember
Level 3 [Member] | Mortgage-backed securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember		 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Level 3 [Member] | Other, including U.S. Treasury Securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherIncludingUsTreasurySecuritiesMember		 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherIncludingUsTreasurySecuritiesMember
Level 3 [Member] | Municipal bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 13,885hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MunicipalBondsMember		 13,628hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MunicipalBondsMember
Level 3 [Member] | Foreign government bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember		 0hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember
Level 3 [Member] | Corporate bonds [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 72,278hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 74,717hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Level 3 [Member] | Other mortgage-backed securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 72,594hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesOtherMember		 82,949hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_MortgageBackedSecuritiesOtherMember
Level 3 [Member] | Equity securities [Member]    
U.S. Government and federally sponsored agency obligations:    
Fair Value 6hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 6hmn_AvailableForSaleSecuritiesFairValue
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Level 3 [Member] | Other Investment [Member]    
U.S. Government and federally sponsored agency obligations:    
Investments, Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherInvestmentMember		 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherInvestmentMember
Level 3 [Member] | Other Policyholders Funds, embedded derivatives [Member] | Recurring [Member]    
U.S. Government and federally sponsored agency obligations:    
Financial Liabilities Other policyholders funds, embedded derivatives, Fair Value $ 22,040us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherPolicyholdersFundsEmbeddedDerivativesMember		 $ 20,049us-gaap_LiabilitiesFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FairValueByMeasurementFrequencyAxis
= us-gaap_FairValueMeasurementsRecurringMember
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= hmn_OtherPolicyholdersFundsEmbeddedDerivativesMember
[1] Separate Account (variable annuity) liabilities are set equal to Separate Account (variable annuity) assets.