Fair Value of Financial Instruments (Details 2) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investments
Other investments, Carrying Amount	$ 148,759	$ 145,409
Other investments, Fair Value	153,228	149,792
Financial Liabilities
Investment contract and life policy reserves, fixed annuity contracts, Carrying Amount	4,072,102	3,774,457
Investment contract and life policy reserves, fixed annuity contracts, Fair value	4,049,840	3,691,123
Investment contract and life policy reserves, account values on life contracts, Carrying Amount	77,429	77,415
Investment contract and life policy reserves, account values on life contracts, Fair value	81,360	81,461
Other policyholder funds, Carrying Amount	653,631	586,689
Other policyholder funds, Fair Value	653,631	586,689
Short-term debt, Carrying Amount	0	38,000
Short-term debt, Fair Value	0	38,000
Long-term debt, Carrying Amount	249,346	199,939
Long-term debt, Fair Value	252,700	209,495
Level 1 [Member]
Investments
Other investments, Fair Value	0	0
Financial Liabilities
Investment contract and life policy reserves, fixed annuity contracts, Fair value	0	0
Investment contract and life policy reserves, account values on life contracts, Fair value	0	0
Other policyholder funds, Fair Value	0	0
Short-term debt, Fair Value	0	0
Long-term debt, Fair Value	252,700	209,495
Level 2 [Member]
Investments
Other investments, Fair Value	0	0
Financial Liabilities
Investment contract and life policy reserves, fixed annuity contracts, Fair value	0	0
Investment contract and life policy reserves, account values on life contracts, Fair value	0	0
Other policyholder funds, Fair Value	575,104	500,080
Short-term debt, Fair Value	0	38,000
Long-term debt, Fair Value	0	0
Level 3 [Member]
Investments
Other investments, Fair Value	153,228	149,792
Financial Liabilities
Investment contract and life policy reserves, fixed annuity contracts, Fair value	4,049,840	3,691,123
Investment contract and life policy reserves, account values on life contracts, Fair value	81,360	81,461
Other policyholder funds, Fair Value	78,527	86,609
Short-term debt, Fair Value	0	0
Long-term debt, Fair Value	$ 0	$ 0

Liability for future policy benefits individual and group annuities and supplementary contracts fair value disclosure.

No definition available.

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

- Definition

Liability for policy holder account balances life.

+ References

No definition available.

+ Details

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

- Definition

Liability for policyholder account balances life fair value.

+ References

No definition available.

+ Details

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

- Definition

Fair Value of the liability as of the balance sheet date to the policyholders for funds held that are returnable under the terms of insurance contracts that were not separately reported.

+ References

No definition available.

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Trading Securities
-URI http://asc.fasb.org/extlink&oid=6526789

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Available-for-Sale Securities
-URI http://asc.fasb.org/extlink&oid=6505594

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 1
-Subparagraph a, f, g
-Article 7

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of accrued obligation to policyholders that relates to insured events under individual and group annuities and supplementary insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 25
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=28366191&loc=d3e13145-158430

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.13(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 20, 22
-Article 5

+ Details

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

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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

- Definition

Other investments not otherwise specified in the taxonomy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(f,g))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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

- Definition

Liability as of the balance sheet date to the policyholders for funds held that are returnable under the terms of insurance contracts that were not separately reported.

+ References

+ Details

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

- Definition

Carrying amount at the balance sheet date of borrowings from a bank, not elsewhere enumerated in the taxonomy, with a maturity within one year (or within one operating cycle if longer) from the date of borrowing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents the amount of short-term debt existing as of the balance sheet date.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: