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Available for sale securities debt maturities a percentage of fair value.

No definition available.

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Percentage of fair value of available for sale debt securities maturing after the twentieth rolling twelve months following the latest balance sheet presented.

No definition available.

Name:	hmn_AvailableForSaleSecuritiesDebtMaturitiesRollingAfterTwentyYearsPercentageOfFairValue
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Percentage of fair value of available for sale debt securities maturing in the eleventh rolling twelve months through the twentieth rolling twelve months following the latest balance sheet presented.

No definition available.

Name:	hmn_AvailableForSaleSecuritiesDebtMaturitiesRollingYearElevenThroughTwentyFairValuePercentage
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Percentage of fair value of available for sale debt securities maturing in the sixth rolling twelve months through the tenth rolling twelve months following the latest balance sheet presented.

No definition available.

Name:	hmn_AvailableForSaleSecuritiesDebtMaturitiesRollingYearSixThroughTenFairValuePercentage
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Percentage of fair value of available for sale debt securities maturing in the second rolling twelve months through the fifth rolling twelve months following the latest balance sheet presented.

No definition available.

Name:	hmn_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughFiveFairValuePercentage
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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the eleventh rolling twelve months through the twentieth rolling twelve months following the latest balance sheet presented. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

No definition available.

Name:	hmn_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateRollingAfter10Through20YearsAmortizedCost
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Amount of available-for-sale debt securities at fair value maturing in the eleventh rolling twelve months through the twentieth rolling twelve months following the latest balance sheet presented.

No definition available.

Name:	hmn_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateRollingAfter10Through20YearsFairValue
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Amount of available-for-sale debt securities at cost, net of adjustments, maturing after the twentieth rolling twelve months following the latest balance sheet presented. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, defined) and fair value hedge accounting adjustments.

No definition available.

Name:	hmn_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateRollingAfter20YearsAmortizedCost
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Amount of available-for-sale debt securities at fair value maturing after the twentieth rolling twelve months following the latest balance sheet presented.

No definition available.

Name:	hmn_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateRollingAfter20YearsFairValue
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Percentage of Total Fair Value [Abstract]

No definition available.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Amortized cost of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in rolling sixth through tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

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Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in rolling sixth through tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year through fifth year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

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Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year through fifth year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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- References

No definition available.

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- References

No definition available.

Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateRollingMaturityAbstract
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Amortized cost excluding accrued interest, after allowance for credit loss, 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.

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

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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.