Fair Value of Financial Instruments - Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Level 1
Investments
Other investments	$ 0	$ 0
Deposit asset on reinsurance	0
Financial Liabilities
Investment contract and policy reserves, fixed annuity contracts	0	0
Investment contract and life policy reserves, account values on life contracts	0	0
Other policyholder funds	0	0
Short-term debt	0
Long-term debt	0	0
Level 2
Investments
Other investments	0	0
Deposit asset on reinsurance	0
Financial Liabilities
Investment contract and policy reserves, fixed annuity contracts	0	0
Investment contract and life policy reserves, account values on life contracts	0	0
Other policyholder funds	495,812	626,325
Short-term debt	0
Long-term debt	322,678	291,938
Level 3
Investments
Other investments	167,185	161,449
Deposit asset on reinsurance	2,634,012
Financial Liabilities
Investment contract and policy reserves, fixed annuity contracts	4,609,880	4,478,338
Investment contract and life policy reserves, account values on life contracts	98,332	90,402
Other policyholder funds	57,738	62,962
Short-term debt	135,000
Long-term debt	0	0
Carrying Amount
Investments
Other investments	163,312	156,725
Deposit asset on reinsurance	2,346,166
Financial Liabilities
Investment contract and policy reserves, fixed annuity contracts	4,675,774	4,555,849
Investment contract and life policy reserves, account values on life contracts	93,465	87,229
Other policyholder funds	553,550	689,287
Short-term debt	135,000
Long-term debt	298,025	297,740
Fair Value
Investments
Other investments	167,185	161,449
Deposit asset on reinsurance	2,634,012
Financial Liabilities
Investment contract and policy reserves, fixed annuity contracts	4,609,880	4,478,338
Investment contract and life policy reserves, account values on life contracts	98,332	90,402
Other policyholder funds	553,550	689,287
Short-term debt	135,000
Long-term debt	$ 322,678	$ 291,938

Deposit Asset On Reinsurance Fair Value Disclosure

No definition available.

Name:	hmn_DepositAssetOnReinsuranceFairValueDisclosure
Namespace Prefix:	hmn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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- Definition

Liability for policyholder account balances life fair value.

+ References

No definition available.

+ Details

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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

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- References

No definition available.

+ Details

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- 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/disclosureRef
-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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- References

No definition available.

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- 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

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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

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