XML 160 R132.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Pension Benefits - Fair Value Plan Assets Measurements (Details) - Pension Plans - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets | $ 0.0 | $ 16.3 | $ 315.8
Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 16.2 |
Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 0.0 |
Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 0.0 |
Limited Liability Companies and Limited Partnerships |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 0.1 |
Limited Liability Companies and Limited Partnerships | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 0.0 |
Limited Liability Companies and Limited Partnerships | Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 0.0 |
Limited Liability Companies and Limited Partnerships | Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 0.0 |
Short-term Investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 16.2 |
Short-term Investments | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 16.2 |
Short-term Investments | Significant Other Observable Inputs (Level 2) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 0.0 |
Short-term Investments | Significant Unobservable Inputs (Level 3) |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 0.0 |
Fair Value, Inputs, Net Asset Value |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 0.1 |
Fair Value, Inputs, Net Asset Value | Limited Liability Companies and Limited Partnerships |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | 0.1 |
Fair Value, Inputs, Net Asset Value | Short-term Investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Pension plan assets |  | $ 0.0 |

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 17 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480482/715-20-55-17 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(02) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Topic 715 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480506/715-20-50-1 + Details
Name: | us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=srt_PartnershipInterestMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ValuationTechniqueAxis=kmpr_FairValueInputsNetAssetValueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |