Fair Value of Financial Instruments - Financial Instrument Not Carried at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Level 1
Investments
Other investments	$ 0	$ 0
Deposit asset on reinsurance	0	0
Financial Liabilities
Investment contract and policy reserves, fixed annuity contracts	0	0
Investment contract and policy reserves, account values on life contracts	0	0
Other policyholder funds	0	0
Short-term debt	0	0
Long-term debt	0	0
Level 2
Investments
Other investments	0	0
Deposit asset on reinsurance	0	0
Financial Liabilities
Investment contract and policy reserves, fixed annuity contracts	0	0
Investment contract and policy reserves, account values on life contracts	0	0
Other policyholder funds	570,806	495,812
Short-term debt	0	0
Long-term debt	313,516	322,678
Level 3
Investments
Other investments	167,127	167,185
Deposit asset on reinsurance	2,421,012	2,634,012
Financial Liabilities
Investment contract and policy reserves, fixed annuity contracts	4,618,673	4,609,880
Investment contract and policy reserves, account values on life contracts	99,601	98,332
Other policyholder funds	58,006	57,738
Short-term debt	135,000	135,000
Long-term debt	0	0
Carrying Amount
Investments
Other investments	163,360	163,312
Deposit asset on reinsurance	2,356,253	2,346,166
Financial Liabilities
Investment contract and policy reserves, fixed annuity contracts	4,708,953	4,675,774
Investment contract and policy reserves, account values on life contracts	94,784	93,465
Other policyholder funds	628,812	553,550
Short-term debt	135,000	135,000
Long-term debt	298,098	298,025
Fair Value
Investments
Other investments	167,127	167,185
Deposit asset on reinsurance	2,421,012	2,634,012
Financial Liabilities
Investment contract and policy reserves, fixed annuity contracts	4,618,673	4,609,880
Investment contract and policy reserves, account values on life contracts	99,601	98,332
Other policyholder funds	628,812	553,550
Short-term debt	135,000	135,000
Long-term debt	$ 313,516	$ 322,678

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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Balance Type:	credit
Period Type:	instant

- Definition

Liability for policyholder account balances life fair value.

+ References

No definition available.

+ Details

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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

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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

+ Details

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- References

No definition available.

+ Details

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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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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

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