00000055132020FYFALSE--12-31P5YP6YP3YP3YP1YP3YP1YP3YP1YP3YnononoP5YP10YP1YP3Y00000055132020-01-012020-12-310000005513us-gaap:CommonClassAMemberexch:XNYS2020-01-012020-12-310000005513exch:XNYSunm:A6250JuniorSubordinatedNotesDue2058Member2020-01-012020-12-31iso4217:USD00000055132020-12-31xbrli:shares00000055132021-02-1200000055132019-12-31iso4217:USDxbrli:shares00000055132019-01-012019-12-3100000055132018-01-012018-12-310000005513us-gaap:CommonStockMember2019-12-310000005513us-gaap:CommonStockMember2018-12-310000005513us-gaap:CommonStockMember2017-12-310000005513us-gaap:CommonStockMember2020-01-012020-12-310000005513us-gaap:CommonStockMember2019-01-012019-12-310000005513us-gaap:CommonStockMember2018-01-012018-12-310000005513us-gaap:CommonStockMember2020-12-310000005513us-gaap:AdditionalPaidInCapitalMember2019-12-310000005513us-gaap:AdditionalPaidInCapitalMember2018-12-310000005513us-gaap:AdditionalPaidInCapitalMember2017-12-310000005513us-gaap:AdditionalPaidInCapitalMember2020-01-012020-12-310000005513us-gaap:AdditionalPaidInCapitalMember2019-01-012019-12-310000005513us-gaap:AdditionalPaidInCapitalMember2018-01-012018-12-310000005513us-gaap:AdditionalPaidInCapitalMember2020-12-310000005513us-gaap:AccumulatedOtherComprehensiveIncomeMember2019-12-310000005513us-gaap:AccumulatedOtherComprehensiveIncomeMember2018-12-310000005513us-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310000005513srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201601Memberus-gaap:AccumulatedOtherComprehensiveIncomeMember2019-12-310000005513srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201601Memberus-gaap:AccumulatedOtherComprehensiveIncomeMember2018-12-310000005513srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201601Memberus-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310000005513srt:RestatementAdjustmentMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2019-12-310000005513srt:RestatementAdjustmentMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2018-12-310000005513srt:RestatementAdjustmentMemberus-gaap:AccumulatedOtherComprehensiveIncomeMember2017-12-310000005513us-gaap:AccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000005513us-gaap:AccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000005513us-gaap:AccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310000005513us-gaap:AccumulatedOtherComprehensiveIncomeMember2020-12-310000005513us-gaap:RetainedEarningsMember2019-12-310000005513us-gaap:RetainedEarningsMember2018-12-310000005513us-gaap:RetainedEarningsMember2017-12-310000005513srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201613Memberus-gaap:RetainedEarningsMember2019-12-310000005513srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201602Memberus-gaap:RetainedEarningsMember2018-12-310000005513srt:CumulativeEffectPeriodOfAdoptionAdjustmentMemberus-gaap:AccountingStandardsUpdate201601Memberus-gaap:RetainedEarningsMember2017-12-310000005513srt:RestatementAdjustmentMemberus-gaap:RetainedEarningsMember2019-12-310000005513srt:RestatementAdjustmentMemberus-gaap:RetainedEarningsMember2018-12-310000005513srt:RestatementAdjustmentMemberus-gaap:RetainedEarningsMember2017-12-310000005513us-gaap:RetainedEarningsMember2020-01-012020-12-310000005513us-gaap:RetainedEarningsMember2019-01-012019-12-310000005513us-gaap:RetainedEarningsMember2018-01-012018-12-310000005513us-gaap:RetainedEarningsMember2020-12-310000005513us-gaap:TreasuryStockMember2019-12-310000005513us-gaap:TreasuryStockMember2018-12-310000005513us-gaap:TreasuryStockMember2017-12-310000005513us-gaap:TreasuryStockMember2020-01-012020-12-310000005513us-gaap:TreasuryStockMember2019-01-012019-12-310000005513us-gaap:TreasuryStockMember2018-01-012018-12-310000005513us-gaap:TreasuryStockMember2020-12-3100000055132018-12-3100000055132017-12-31unm:Integer00000055132020-01-010000005513us-gaap:AccountingStandardsUpdate201613Member2019-12-310000005513us-gaap:AccountingStandardsUpdate201613Member2020-01-010000005513srt:RestatementAdjustmentMemberus-gaap:AccountingStandardsUpdate201613Member2020-01-01xbrli:pure0000005513us-gaap:FairValueInputsLevel1Member2020-12-310000005513unm:FairValueInputsOtherThanLevel1Member2020-12-310000005513unm:PricingServiceMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513unm:OtherObservableMarketDataMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513unm:FairValueInputsLevel2OrLevel3Member2020-12-310000005513unm:PrivateCreditMemberunm:NotRedeemableMemberus-gaap:PrivateEquityFundsMember2020-12-310000005513unm:Quarterlyafter2yearlockwith90daysnoticeMemberunm:PrivateCreditMemberus-gaap:PrivateEquityFundsMember2020-12-310000005513unm:PrivateCreditMemberus-gaap:PrivateEquityFundsMember2020-12-310000005513unm:PrivateEquityLimitedPartnershipMemberunm:NotRedeemableMemberus-gaap:PrivateEquityFundsMember2020-12-310000005513unm:PrivateEquityLimitedPartnershipMemberunm:QuarterlyAfter55YearLockWith90DaysNoticeMemberus-gaap:PrivateEquityFundsMember2020-12-310000005513unm:PrivateEquityLimitedPartnershipMemberus-gaap:PrivateEquityFundsMember2020-12-310000005513unm:RealAssetsMemberunm:NotRedeemableMemberus-gaap:PrivateEquityFundsMember2020-12-310000005513unm:RealAssetsMemberus-gaap:PrivateEquityFundsMemberunm:QuarterlyMember2020-12-310000005513unm:RealAssetsMemberus-gaap:PrivateEquityFundsMember2020-12-310000005513us-gaap:PrivateEquityFundsMember2020-12-310000005513unm:PrivateCreditMemberunm:NotRedeemableMemberus-gaap:PrivateEquityFundsMember2019-12-310000005513unm:Quarterlyafter2yearlockwith90daysnoticeMemberunm:PrivateCreditMemberus-gaap:PrivateEquityFundsMember2019-12-310000005513unm:PrivateCreditMemberus-gaap:PrivateEquityFundsMember2019-12-310000005513unm:PrivateEquityLimitedPartnershipMemberunm:NotRedeemableMemberus-gaap:PrivateEquityFundsMember2019-12-310000005513unm:RealAssetsMemberunm:NotRedeemableMemberus-gaap:PrivateEquityFundsMember2019-12-310000005513unm:RealAssetsMemberus-gaap:PrivateEquityFundsMemberunm:QuarterlyMember2019-12-310000005513unm:RealAssetsMemberus-gaap:PrivateEquityFundsMember2019-12-310000005513us-gaap:PrivateEquityFundsMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:USTreasuryAndGovernmentMemberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:USTreasuryAndGovernmentMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:USTreasuryAndGovernmentMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:USTreasuryAndGovernmentMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310000005513us-gaap:USTreasuryAndGovernmentMember2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Memberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Memberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000005513us-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMember2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:PublicUtilityBondsMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PublicUtilityBondsMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PublicUtilityBondsMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PublicUtilityBondsMember2020-12-310000005513us-gaap:PublicUtilityBondsMember2020-12-310000005513us-gaap:AssetBackedSecuritiesMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:AssetBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:AssetBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:AssetBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310000005513us-gaap:AssetBackedSecuritiesMember2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310000005513us-gaap:CorporateDebtSecuritiesMember2020-12-310000005513us-gaap:RedeemablePreferredStockMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:RedeemablePreferredStockMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:RedeemablePreferredStockMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:RedeemablePreferredStockMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310000005513us-gaap:RedeemablePreferredStockMember2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CurrencySwapMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Memberus-gaap:CurrencySwapMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Memberus-gaap:CurrencySwapMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:CurrencySwapMember2020-12-310000005513us-gaap:CurrencySwapMember2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:CreditDefaultSwapMemberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:CreditDefaultSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:CreditDefaultSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:CreditDefaultSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310000005513us-gaap:CreditDefaultSwapMember2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:PrivateEquityFundsMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PrivateEquityFundsMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PrivateEquityFundsMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PrivateEquityFundsMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310000005513us-gaap:InterestRateSwapMember2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CurrencySwapMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Memberus-gaap:CurrencySwapMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Memberus-gaap:CurrencySwapMember2020-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:CurrencySwapMember2020-12-310000005513us-gaap:CurrencySwapMember2020-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMember2020-12-310000005513us-gaap:DerivativeMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2020-12-310000005513us-gaap:DerivativeMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:DerivativeMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:DerivativeMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:USTreasuryAndGovernmentMemberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:USTreasuryAndGovernmentMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:USTreasuryAndGovernmentMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:USTreasuryAndGovernmentMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310000005513us-gaap:USTreasuryAndGovernmentMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Memberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Memberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000005513us-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:PublicUtilityBondsMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PublicUtilityBondsMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PublicUtilityBondsMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PublicUtilityBondsMember2019-12-310000005513us-gaap:PublicUtilityBondsMember2019-12-310000005513us-gaap:AssetBackedSecuritiesMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:AssetBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:AssetBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:AssetBackedSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310000005513us-gaap:AssetBackedSecuritiesMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310000005513us-gaap:CorporateDebtSecuritiesMember2019-12-310000005513us-gaap:RedeemablePreferredStockMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:RedeemablePreferredStockMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:RedeemablePreferredStockMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:RedeemablePreferredStockMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310000005513us-gaap:RedeemablePreferredStockMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CurrencySwapMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Memberus-gaap:CurrencySwapMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Memberus-gaap:CurrencySwapMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:CurrencySwapMember2019-12-310000005513us-gaap:CurrencySwapMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:CreditDefaultSwapMemberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:CreditDefaultSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:CreditDefaultSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:CreditDefaultSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310000005513us-gaap:CreditDefaultSwapMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:PrivateEquityFundsMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PrivateEquityFundsMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PrivateEquityFundsMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PrivateEquityFundsMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310000005513us-gaap:InterestRateSwapMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:CurrencySwapMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Memberus-gaap:CurrencySwapMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Memberus-gaap:CurrencySwapMember2019-12-310000005513us-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:CurrencySwapMember2019-12-310000005513us-gaap:CurrencySwapMember2019-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMember2019-12-310000005513us-gaap:DerivativeMemberus-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsRecurringMember2019-12-310000005513us-gaap:DerivativeMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:DerivativeMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:DerivativeMemberus-gaap:FairValueMeasurementsRecurringMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMember2019-12-310000005513us-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000005513us-gaap:USStatesAndPoliticalSubdivisionsMember2020-01-012020-12-310000005513us-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000005513us-gaap:OtherComprehensiveIncomeMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-01-012020-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-01-012020-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMember2019-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMember2020-12-310000005513us-gaap:OtherComprehensiveIncomeMemberus-gaap:ForeignGovernmentDebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:ForeignGovernmentDebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:PublicUtilityBondsMember2019-12-310000005513us-gaap:PublicUtilityBondsMember2020-01-012020-12-310000005513us-gaap:PublicUtilityBondsMember2020-12-310000005513us-gaap:OtherComprehensiveIncomeMemberus-gaap:PublicUtilityBondsMember2020-01-012020-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:PublicUtilityBondsMember2020-01-012020-12-310000005513us-gaap:AssetBackedSecuritiesMember2019-12-310000005513us-gaap:AssetBackedSecuritiesMember2020-01-012020-12-310000005513us-gaap:AssetBackedSecuritiesMember2020-12-310000005513us-gaap:OtherComprehensiveIncomeMemberus-gaap:AssetBackedSecuritiesMember2020-01-012020-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:AssetBackedSecuritiesMember2020-01-012020-12-310000005513us-gaap:CorporateDebtSecuritiesMember2019-12-310000005513us-gaap:CorporateDebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:CorporateDebtSecuritiesMember2020-12-310000005513us-gaap:OtherComprehensiveIncomeMemberus-gaap:CorporateDebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:CorporateDebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:DebtSecuritiesMember2019-12-310000005513us-gaap:DebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:DebtSecuritiesMember2020-12-310000005513us-gaap:OtherComprehensiveIncomeMemberus-gaap:DebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:DebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:EquitySecuritiesMember2019-12-310000005513us-gaap:EquitySecuritiesMember2020-01-012020-12-310000005513us-gaap:EquitySecuritiesMember2020-12-310000005513us-gaap:OtherComprehensiveIncomeMemberus-gaap:EquitySecuritiesMember2020-01-012020-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:EquitySecuritiesMember2020-01-012020-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMember2020-01-012020-12-310000005513us-gaap:OtherComprehensiveIncomeMemberus-gaap:EmbeddedDerivativeFinancialInstrumentsMember2020-01-012020-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:EmbeddedDerivativeFinancialInstrumentsMember2020-01-012020-12-310000005513us-gaap:USStatesAndPoliticalSubdivisionsMember2018-12-310000005513us-gaap:USStatesAndPoliticalSubdivisionsMember2019-01-012019-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMember2018-12-310000005513us-gaap:ForeignGovernmentDebtSecuritiesMember2019-01-012019-12-310000005513us-gaap:PublicUtilityBondsMember2018-12-310000005513us-gaap:PublicUtilityBondsMember2019-01-012019-12-310000005513us-gaap:AssetBackedSecuritiesMember2018-12-310000005513us-gaap:AssetBackedSecuritiesMember2019-01-012019-12-310000005513us-gaap:CorporateDebtSecuritiesMember2018-12-310000005513us-gaap:CorporateDebtSecuritiesMember2019-01-012019-12-310000005513us-gaap:RedeemablePreferredStockMember2018-12-310000005513us-gaap:RedeemablePreferredStockMember2019-01-012019-12-310000005513us-gaap:RedeemablePreferredStockMember2019-12-310000005513us-gaap:DebtSecuritiesMember2018-12-310000005513us-gaap:DebtSecuritiesMember2019-01-012019-12-310000005513us-gaap:EquitySecuritiesMember2018-12-310000005513us-gaap:EquitySecuritiesMember2019-01-012019-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMember2018-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMember2019-01-012019-12-310000005513us-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Member2020-12-31utr:Rate0000005513srt:MinimumMemberus-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:MeasurementInputEntityCreditRiskMember2020-12-310000005513us-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:MeasurementInputEntityCreditRiskMembersrt:MaximumMember2020-12-310000005513srt:WeightedAverageMemberus-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:MeasurementInputEntityCreditRiskMember2020-12-310000005513us-gaap:MarketApproachValuationTechniqueMemberus-gaap:EquitySecuritiesMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:ValuationTechniqueDiscountedCashFlowMemberus-gaap:FairValueInputsLevel3Memberus-gaap:DerivativeFinancialInstrumentsLiabilitiesMember2020-12-310000005513us-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513srt:MinimumMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Membersrt:MaximumMember2019-12-310000005513srt:WeightedAverageMemberus-gaap:MeasurementInputDiscountForLackOfMarketabilityMemberus-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513srt:MinimumMemberus-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:MeasurementInputEntityCreditRiskMember2019-12-310000005513us-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:MeasurementInputEntityCreditRiskMembersrt:MaximumMember2019-12-310000005513srt:WeightedAverageMemberus-gaap:MarketApproachValuationTechniqueMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:FairValueInputsLevel3Memberus-gaap:MeasurementInputEntityCreditRiskMember2019-12-310000005513us-gaap:MarketApproachValuationTechniqueMemberus-gaap:EquitySecuritiesMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:ValuationTechniqueDiscountedCashFlowMemberus-gaap:FairValueInputsLevel3Memberus-gaap:DerivativeFinancialInstrumentsLiabilitiesMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsNonrecurringMember2020-12-310000005513us-gaap:FairValueMeasurementsNonrecurringMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:FairValueMeasurementsNonrecurringMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:FairValueMeasurementsNonrecurringMember2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:FairValueMeasurementsNonrecurringMember2019-12-310000005513us-gaap:FairValueMeasurementsNonrecurringMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:FairValueMeasurementsNonrecurringMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:FairValueMeasurementsNonrecurringMember2019-12-310000005513us-gaap:AllOtherCorporateBondsMember2020-12-310000005513us-gaap:DebtSecuritiesMember2020-12-310000005513us-gaap:AllOtherCorporateBondsMember2019-12-310000005513us-gaap:DebtSecuritiesMember2019-12-310000005513unm:AvailableForSaleSecuritiesUnrealizedGainPositionFairValueMember2020-12-310000005513unm:AvailableForSaleSecuritiesUnrealizedLossPositionFairValueMember2020-12-310000005513unm:AvailableForSaleSecuritiesUnrealizedGainPositionFairValueMember2019-12-310000005513unm:AvailableForSaleSecuritiesUnrealizedLossPositionFairValueMember2019-12-310000005513us-gaap:ExternalCreditRatingInvestmentGradeMember2020-12-310000005513us-gaap:ExternalCreditRatingNonInvestmentGradeMember2020-12-310000005513us-gaap:AllOtherCorporateBondsMember2020-01-012020-12-310000005513us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember2020-12-310000005513us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberunm:TaxCreditPartnershipMember2020-12-310000005513us-gaap:EquityMethodInvestmentsMemberus-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember2020-12-310000005513us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember2019-12-310000005513us-gaap:VariableInterestEntityNotPrimaryBeneficiaryMemberunm:TaxCreditPartnershipMember2019-12-310000005513us-gaap:EquityMethodInvestmentsMemberus-gaap:VariableInterestEntityNotPrimaryBeneficiaryMember2019-12-310000005513us-gaap:CommercialRealEstateMember2020-12-310000005513us-gaap:CommercialRealEstateMember2019-12-310000005513unm:LoanToValueRatioTotalMemberus-gaap:CommercialRealEstateMember2020-12-310000005513srt:ApartmentBuildingMember2020-12-310000005513srt:ApartmentBuildingMember2019-12-310000005513srt:IndustrialPropertyMember2020-12-310000005513srt:IndustrialPropertyMember2019-12-310000005513srt:OfficeBuildingMember2020-12-310000005513srt:OfficeBuildingMember2019-12-310000005513srt:RetailSiteMember2020-12-310000005513srt:RetailSiteMember2019-12-310000005513srt:OtherPropertyMember2020-12-310000005513srt:OtherPropertyMember2019-12-310000005513unm:NewEnglandMember2020-12-310000005513unm:NewEnglandMember2019-12-310000005513unm:MiddleAtlanticMember2020-12-310000005513unm:MiddleAtlanticMember2019-12-310000005513unm:EastNorthCentralMember2020-12-310000005513unm:EastNorthCentralMember2019-12-310000005513unm:WestNorthCentralMember2020-12-310000005513unm:WestNorthCentralMember2019-12-310000005513unm:SouthAtlanticMember2020-12-310000005513unm:SouthAtlanticMember2019-12-310000005513unm:EastSouthCentralMember2020-12-310000005513unm:EastSouthCentralMember2019-12-310000005513unm:WestSouthCentralMember2020-12-310000005513unm:WestSouthCentralMember2019-12-310000005513unm:MountainMember2020-12-310000005513unm:MountainMember2019-12-310000005513unm:PacificMember2020-12-310000005513unm:PacificMember2019-12-310000005513unm:AACreditRatingMember2020-12-310000005513unm:AACreditRatingMember2019-12-310000005513unm:CreditRatingMember2020-12-310000005513unm:CreditRatingMember2019-12-310000005513unm:BBBCreditRatingMember2020-12-310000005513unm:BBBCreditRatingMember2019-12-310000005513unm:BBCreditRatingMember2020-12-310000005513unm:BBCreditRatingMember2019-12-310000005513unm:BCreditRatingMember2020-12-310000005513unm:BCreditRatingMember2019-12-310000005513unm:TotalMember2020-12-310000005513unm:TotalMember2019-12-310000005513unm:LoanToValueRatioBelowOrEqualTo65PercentMember2020-12-310000005513unm:LoanToValueRatioBelowOrEqualTo65PercentMember2019-12-310000005513unm:LoanToValueRatioAbove65To75PercentMember2020-12-310000005513unm:LoanToValueRatioAbove65To75PercentMember2019-12-310000005513unm:LoanToValueRatioAbove75To85PercentMember2020-12-310000005513unm:LoanToValueRatioAbove75To85PercentMember2019-12-310000005513unm:LoanToValueRatioAbove85PercentMember2020-12-310000005513unm:LoanToValueRatioAbove85PercentMember2019-12-310000005513unm:TotalMember2020-12-310000005513unm:TotalMember2019-12-310000005513unm:AACreditRatingMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:CreditRatingMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:BBBCreditRatingMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:BBCreditRatingMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:BCreditRatingMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:OriginatedFiveOrMoreYearsBeforeLastFiscalYearMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:OriginatedFourYearsBeforeLastFiscalYearMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:OriginatedThreeYearsBeforeLastFiscalYearMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:OriginatedTwoYearsBeforeLastFiscalYearMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:OriginatedInFiscalYearBeforeLatestFiscalYearMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:OriginatedInCurrentFiscalYearMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:OriginatedFiveOrMoreYearsBeforeLastFiscalYearMember2020-12-310000005513unm:OriginatedFourYearsBeforeLastFiscalYearMember2020-12-310000005513unm:OriginatedThreeYearsBeforeLastFiscalYearMember2020-12-310000005513unm:OriginatedTwoYearsBeforeLastFiscalYearMember2020-12-310000005513unm:OriginatedInFiscalYearBeforeLatestFiscalYearMember2020-12-310000005513unm:OriginatedInCurrentFiscalYearMember2020-12-310000005513unm:LoanToValueRatioBelowOrEqualTo65PercentMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:LoanToValueRatioAbove65To75PercentMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:LoanToValueRatioAbove75To85PercentMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:LoanToValueRatioAbove85PercentMemberus-gaap:CommercialRealEstateMember2020-12-310000005513unm:LoanToValueRatioBelowOrEqualTo65PercentMemberus-gaap:CommercialRealEstateMember2020-01-010000005513unm:LoanToValueRatioBelowOrEqualTo65PercentMemberus-gaap:CommercialRealEstateMember2020-01-012020-12-310000005513unm:LoanToValueRatioAbove65To75PercentMemberus-gaap:CommercialRealEstateMember2020-01-010000005513unm:LoanToValueRatioAbove65To75PercentMemberus-gaap:CommercialRealEstateMember2020-01-012020-12-310000005513unm:LoanToValueRatioAbove75To85PercentMemberus-gaap:CommercialRealEstateMember2020-01-010000005513unm:LoanToValueRatioAbove75To85PercentMemberus-gaap:CommercialRealEstateMember2020-01-012020-12-310000005513unm:LoanToValueRatioAbove85PercentMemberus-gaap:CommercialRealEstateMember2020-01-010000005513unm:LoanToValueRatioAbove85PercentMemberus-gaap:CommercialRealEstateMember2020-01-012020-12-310000005513unm:LoanToValueRatioTotalMemberus-gaap:CommercialRealEstateMember2020-01-010000005513unm:LoanToValueRatioTotalMemberus-gaap:CommercialRealEstateMember2020-01-012020-12-310000005513us-gaap:CommercialRealEstateMember2019-01-012019-12-310000005513us-gaap:CommercialRealEstateMember2020-01-012020-12-310000005513us-gaap:CommercialRealEstateMember2018-01-012018-12-310000005513unm:UnfundedMortgageLoanCommitmentsMember2020-12-310000005513unm:InvestmentRealEstateMember2020-01-012020-12-310000005513unm:InvestmentRealEstateMember2018-01-012018-12-310000005513unm:OffBalanceSheetAmountMember2020-12-310000005513unm:OffBalanceSheetAmountMember2019-12-310000005513us-gaap:USTreasuryAndGovernmentMemberus-gaap:MaturityOvernightMember2020-12-310000005513us-gaap:USTreasuryAndGovernmentMemberus-gaap:MaturityOvernightMember2019-12-310000005513us-gaap:MaturityOvernightMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000005513us-gaap:MaturityOvernightMemberus-gaap:USStatesAndPoliticalSubdivisionsMember2019-12-310000005513us-gaap:MaturityOvernightMemberus-gaap:PublicUtilityBondsMember2020-12-310000005513us-gaap:MaturityOvernightMemberus-gaap:PublicUtilityBondsMember2019-12-310000005513us-gaap:MaturityOvernightMemberus-gaap:CorporateBondSecuritiesMember2020-12-310000005513us-gaap:MaturityOvernightMemberus-gaap:CorporateBondSecuritiesMember2019-12-310000005513us-gaap:MaturityOvernightMember2020-12-310000005513us-gaap:MaturityOvernightMember2019-12-310000005513us-gaap:MortgageBackedSecuritiesMember2020-12-310000005513us-gaap:MortgageBackedSecuritiesMember2019-12-310000005513us-gaap:OverTheCounterMember2020-12-310000005513us-gaap:OverTheCounterMember2019-12-310000005513us-gaap:DebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:DebtSecuritiesMember2019-01-012019-12-310000005513us-gaap:DebtSecuritiesMember2018-01-012018-12-310000005513us-gaap:DerivativeMember2020-01-012020-12-310000005513us-gaap:DerivativeMember2019-01-012019-12-310000005513us-gaap:DerivativeMember2018-01-012018-12-310000005513us-gaap:MortgageReceivablesMember2020-01-012020-12-310000005513us-gaap:MortgageReceivablesMember2019-01-012019-12-310000005513us-gaap:MortgageReceivablesMember2018-01-012018-12-310000005513us-gaap:PolicyLoansMember2020-01-012020-12-310000005513us-gaap:PolicyLoansMember2019-01-012019-12-310000005513us-gaap:PolicyLoansMember2018-01-012018-12-310000005513us-gaap:EquitySecuritiesMember2020-01-012020-12-310000005513us-gaap:EquitySecuritiesMember2019-01-012019-12-310000005513us-gaap:EquitySecuritiesMember2018-01-012018-12-310000005513srt:PartnershipInterestMember2020-01-012020-12-310000005513srt:PartnershipInterestMember2019-01-012019-12-310000005513srt:PartnershipInterestMember2018-01-012018-12-310000005513us-gaap:OtherLongTermInvestmentsMember2020-01-012020-12-310000005513us-gaap:OtherLongTermInvestmentsMember2019-01-012019-12-310000005513us-gaap:OtherLongTermInvestmentsMember2018-01-012018-12-310000005513us-gaap:ShortTermInvestmentsMember2020-01-012020-12-310000005513us-gaap:ShortTermInvestmentsMember2019-01-012019-12-310000005513us-gaap:ShortTermInvestmentsMember2018-01-012018-12-310000005513unm:CreditExposureMember2020-12-310000005513unm:CreditExposureMember2019-12-310000005513us-gaap:CashMember2020-12-310000005513us-gaap:CashMember2019-12-310000005513us-gaap:AvailableforsaleSecuritiesMember2020-12-310000005513us-gaap:AvailableforsaleSecuritiesMember2019-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveVariablePayFixedMember2017-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2017-12-310000005513unm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMemberus-gaap:InterestRateSwapMember2017-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:CreditDefaultSwapMember2017-12-310000005513us-gaap:ForwardContractsMember2017-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveVariablePayFixedMember2018-01-012018-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2018-01-012018-12-310000005513unm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMemberus-gaap:InterestRateSwapMember2018-01-012018-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:CreditDefaultSwapMember2018-01-012018-12-310000005513us-gaap:ForwardContractsMember2018-01-012018-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveVariablePayFixedMember2018-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2018-12-310000005513unm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMemberus-gaap:InterestRateSwapMember2018-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:CreditDefaultSwapMember2018-12-310000005513us-gaap:ForwardContractsMember2018-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveVariablePayFixedMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2019-01-012019-12-310000005513unm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMemberus-gaap:InterestRateSwapMember2019-01-012019-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:CreditDefaultSwapMember2019-01-012019-12-310000005513us-gaap:ForwardContractsMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveVariablePayFixedMember2019-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2019-12-310000005513unm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMemberus-gaap:InterestRateSwapMember2019-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:CreditDefaultSwapMember2019-12-310000005513us-gaap:ForwardContractsMember2019-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveVariablePayFixedMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2020-01-012020-12-310000005513unm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMemberus-gaap:InterestRateSwapMember2020-01-012020-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:CreditDefaultSwapMember2020-01-012020-12-310000005513us-gaap:ForwardContractsMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveVariablePayFixedMember2020-12-310000005513us-gaap:InterestRateSwapMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2020-12-310000005513unm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMemberus-gaap:InterestRateSwapMember2020-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:CreditDefaultSwapMember2020-12-310000005513us-gaap:ForwardContractsMember2020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2019-12-310000005513us-gaap:ForwardContractsMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMemberus-gaap:FairValueHedgingMember2020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMemberus-gaap:FairValueHedgingMember2019-12-310000005513unm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMemberus-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:DesignatedAsHedgingInstrumentMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMemberus-gaap:FairValueHedgingMember2020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:AvailableforsaleSecuritiesMemberus-gaap:DesignatedAsHedgingInstrumentMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMemberus-gaap:FairValueHedgingMember2019-12-310000005513us-gaap:LongTermDebtMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMemberus-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2020-12-310000005513us-gaap:LongTermDebtMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMemberus-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:NondesignatedMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:NondesignatedMemberunm:DerivativeFinancialInstrumentsReceiveFixedPayFixedMember2020-12-310000005513us-gaap:CreditDefaultSwapMemberus-gaap:CreditRiskContractMemberus-gaap:NondesignatedMember2020-12-310000005513us-gaap:CreditDefaultSwapMemberus-gaap:CreditRiskContractMemberus-gaap:NondesignatedMember2019-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForwardContractsMember2020-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForwardContractsMember2019-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMemberus-gaap:OtherLongTermInvestmentsMember2020-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:OtherLiabilitiesMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2020-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:OtherLongTermInvestmentsMemberus-gaap:FairValueHedgingMember2020-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:OtherLiabilitiesMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2020-12-310000005513us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:OtherLongTermInvestmentsMember2020-12-310000005513us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:OtherLiabilitiesMember2020-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:NondesignatedMemberus-gaap:OtherLongTermInvestmentsMember2020-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:NondesignatedMemberus-gaap:OtherLiabilitiesMember2020-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForwardContractsMemberus-gaap:OtherLongTermInvestmentsMember2020-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForwardContractsMemberus-gaap:OtherLiabilitiesMember2020-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForeignExchangeContractMemberus-gaap:OtherLongTermInvestmentsMember2020-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForeignExchangeContractMemberus-gaap:OtherLiabilitiesMember2020-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:NondesignatedMemberus-gaap:OtherLongTermInvestmentsMember2020-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:NondesignatedMemberus-gaap:OtherLiabilitiesMember2020-12-310000005513us-gaap:NondesignatedMemberus-gaap:OtherLongTermInvestmentsMember2020-12-310000005513us-gaap:NondesignatedMemberus-gaap:OtherLiabilitiesMember2020-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMemberus-gaap:OtherLongTermInvestmentsMember2019-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:OtherLiabilitiesMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:OtherLongTermInvestmentsMemberus-gaap:FairValueHedgingMember2019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:OtherLiabilitiesMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2019-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:OtherLongTermInvestmentsMemberus-gaap:FairValueHedgingMember2019-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:OtherLiabilitiesMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2019-12-310000005513us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:OtherLongTermInvestmentsMemberus-gaap:FairValueHedgingMember2019-12-310000005513us-gaap:OtherLiabilitiesMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2019-12-310000005513us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:OtherLongTermInvestmentsMember2019-12-310000005513us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:OtherLiabilitiesMember2019-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:NondesignatedMemberus-gaap:OtherLongTermInvestmentsMember2019-12-310000005513us-gaap:CreditRiskContractMemberus-gaap:NondesignatedMemberus-gaap:OtherLiabilitiesMember2019-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForeignExchangeContractMemberus-gaap:OtherLongTermInvestmentsMember2019-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForeignExchangeContractMemberus-gaap:OtherLiabilitiesMember2019-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:NondesignatedMemberus-gaap:OtherLongTermInvestmentsMember2019-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:NondesignatedMemberus-gaap:OtherLiabilitiesMember2019-12-310000005513us-gaap:NondesignatedMemberus-gaap:OtherLongTermInvestmentsMember2019-12-310000005513us-gaap:NondesignatedMemberus-gaap:OtherLiabilitiesMember2019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:InvestmentIncomeMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:GainLossOnInvestmentsMember1us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMemberus-gaap:InterestExpenseMember2020-01-012020-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2020-01-012020-12-310000005513us-gaap:GainLossOnInvestmentsMember1us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2020-01-012020-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMemberus-gaap:InterestExpenseMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:InvestmentIncomeMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:GainLossOnInvestmentsMember1us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:InterestExpenseMemberus-gaap:FairValueHedgingMember2020-01-012020-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2020-01-012020-12-310000005513us-gaap:GainLossOnInvestmentsMember1us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2020-01-012020-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:InterestExpenseMemberus-gaap:FairValueHedgingMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:InvestmentIncomeMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:GainLossOnInvestmentsMember1us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMemberus-gaap:InterestExpenseMember2019-01-012019-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2019-01-012019-12-310000005513us-gaap:GainLossOnInvestmentsMember1us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2019-01-012019-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMemberus-gaap:InterestExpenseMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:InvestmentIncomeMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:GainLossOnInvestmentsMember1us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:InterestExpenseMemberus-gaap:FairValueHedgingMember2019-01-012019-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2019-01-012019-12-310000005513us-gaap:GainLossOnInvestmentsMember1us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2019-01-012019-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:InterestExpenseMemberus-gaap:FairValueHedgingMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:InvestmentIncomeMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2018-01-012018-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:GainLossOnInvestmentsMember1us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2018-01-012018-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMemberus-gaap:InterestExpenseMember2018-01-012018-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2018-01-012018-12-310000005513us-gaap:GainLossOnInvestmentsMember1us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2018-01-012018-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMemberus-gaap:InterestExpenseMember2018-01-012018-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:InvestmentIncomeMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2018-01-012018-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:GainLossOnInvestmentsMember1us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2018-01-012018-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:InterestExpenseMemberus-gaap:FairValueHedgingMember2018-01-012018-12-310000005513us-gaap:InvestmentIncomeMemberus-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2018-01-012018-12-310000005513us-gaap:GainLossOnInvestmentsMember1us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:FairValueHedgingMember2018-01-012018-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:InterestExpenseMemberus-gaap:FairValueHedgingMember2018-01-012018-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2018-01-012018-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2020-01-012020-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2019-01-012019-12-310000005513us-gaap:ForeignExchangeContractMemberus-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2018-01-012018-12-310000005513us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2020-01-012020-12-310000005513us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2019-01-012019-12-310000005513us-gaap:DesignatedAsHedgingInstrumentMemberus-gaap:CashFlowHedgingMember2018-01-012018-12-310000005513us-gaap:NondesignatedMemberus-gaap:CreditDefaultSwapMember2020-01-012020-12-310000005513us-gaap:NondesignatedMemberus-gaap:CreditDefaultSwapMember2019-01-012019-12-310000005513us-gaap:NondesignatedMemberus-gaap:CreditDefaultSwapMember2018-01-012018-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:NondesignatedMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:NondesignatedMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:NondesignatedMember2018-01-012018-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForeignExchangeContractMember2020-01-012020-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForeignExchangeContractMember2019-01-012019-12-310000005513us-gaap:NondesignatedMemberus-gaap:ForeignExchangeContractMember2018-01-012018-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:NondesignatedMember2020-01-012020-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:NondesignatedMember2019-01-012019-12-310000005513us-gaap:EmbeddedDerivativeFinancialInstrumentsMemberus-gaap:NondesignatedMember2018-01-012018-12-310000005513us-gaap:NondesignatedMember2020-01-012020-12-310000005513us-gaap:NondesignatedMember2019-01-012019-12-310000005513us-gaap:NondesignatedMember2018-01-012018-12-310000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2017-12-310000005513us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2017-12-310000005513us-gaap:AccumulatedTranslationAdjustmentMember2017-12-310000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2017-12-310000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMemberus-gaap:AccountingStandardsUpdate201601Member2018-01-010000005513us-gaap:AccountingStandardsUpdate201601Memberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-01-010000005513us-gaap:AccountingStandardsUpdate201601Memberus-gaap:AccumulatedTranslationAdjustmentMember2018-01-010000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMemberus-gaap:AccountingStandardsUpdate201601Member2018-01-010000005513us-gaap:AccountingStandardsUpdate201601Member2018-01-010000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2018-01-012018-12-310000005513us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-01-012018-12-310000005513us-gaap:AccumulatedTranslationAdjustmentMember2018-01-012018-12-310000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2018-01-012018-12-310000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2018-12-310000005513us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-12-310000005513us-gaap:AccumulatedTranslationAdjustmentMember2018-12-310000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2018-12-310000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2019-01-012019-12-310000005513us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-01-012019-12-310000005513us-gaap:AccumulatedTranslationAdjustmentMember2019-01-012019-12-310000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2019-01-012019-12-310000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2019-12-310000005513us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-12-310000005513us-gaap:AccumulatedTranslationAdjustmentMember2019-12-310000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2019-12-310000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2020-01-012020-12-310000005513us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-01-012020-12-310000005513us-gaap:AccumulatedTranslationAdjustmentMember2020-01-012020-12-310000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2020-01-012020-12-310000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2020-12-310000005513us-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-12-310000005513us-gaap:AccumulatedTranslationAdjustmentMember2020-12-310000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMember2020-12-310000005513us-gaap:DebtSecuritiesMember2020-12-310000005513us-gaap:DebtSecuritiesMember2019-12-310000005513us-gaap:DebtSecuritiesMember2018-12-310000005513us-gaap:DebtSecuritiesMember2018-01-010000005513us-gaap:DebtSecuritiesMember2017-12-310000005513us-gaap:DebtSecuritiesMember2020-01-012020-12-310000005513us-gaap:DebtSecuritiesMember2019-01-012019-12-310000005513us-gaap:DebtSecuritiesMember2018-01-012018-12-310000005513us-gaap:OtherInvestmentsMember2020-12-310000005513us-gaap:OtherInvestmentsMember2019-12-310000005513us-gaap:OtherInvestmentsMember2018-12-310000005513us-gaap:OtherInvestmentsMember2018-01-010000005513us-gaap:OtherInvestmentsMember2017-12-310000005513us-gaap:OtherInvestmentsMember2020-01-012020-12-310000005513us-gaap:OtherInvestmentsMember2019-01-012019-12-310000005513us-gaap:OtherInvestmentsMember2018-01-012018-12-310000005513unm:DeferredAcquisitionCostsMember2020-12-310000005513unm:DeferredAcquisitionCostsMember2019-12-310000005513unm:DeferredAcquisitionCostsMember2018-12-310000005513unm:DeferredAcquisitionCostsMember2018-01-010000005513unm:DeferredAcquisitionCostsMember2017-12-310000005513unm:DeferredAcquisitionCostsMember2020-01-012020-12-310000005513unm:DeferredAcquisitionCostsMember2019-01-012019-12-310000005513unm:DeferredAcquisitionCostsMember2018-01-012018-12-310000005513unm:ReserveForFuturePolicyAndContractBenefitsMember2020-12-310000005513unm:ReserveForFuturePolicyAndContractBenefitsMember2019-12-310000005513unm:ReserveForFuturePolicyAndContractBenefitsMember2018-12-310000005513unm:ReserveForFuturePolicyAndContractBenefitsMember2018-01-010000005513unm:ReserveForFuturePolicyAndContractBenefitsMember2017-12-310000005513unm:ReserveForFuturePolicyAndContractBenefitsMember2020-01-012020-12-310000005513unm:ReserveForFuturePolicyAndContractBenefitsMember2019-01-012019-12-310000005513unm:ReserveForFuturePolicyAndContractBenefitsMember2018-01-012018-12-310000005513us-gaap:ReinsuranceRecoverableMember2020-12-310000005513us-gaap:ReinsuranceRecoverableMember2019-12-310000005513us-gaap:ReinsuranceRecoverableMember2018-12-310000005513us-gaap:ReinsuranceRecoverableMember2018-01-010000005513us-gaap:ReinsuranceRecoverableMember2017-12-310000005513us-gaap:ReinsuranceRecoverableMember2020-01-012020-12-310000005513us-gaap:ReinsuranceRecoverableMember2019-01-012019-12-310000005513us-gaap:ReinsuranceRecoverableMember2018-01-012018-12-310000005513us-gaap:DeferredIncomeTaxChargesMember2020-12-310000005513us-gaap:DeferredIncomeTaxChargesMember2019-12-310000005513us-gaap:DeferredIncomeTaxChargesMember2018-12-310000005513us-gaap:DeferredIncomeTaxChargesMember2018-01-010000005513us-gaap:DeferredIncomeTaxChargesMember2017-12-310000005513us-gaap:DeferredIncomeTaxChargesMember2020-01-012020-12-310000005513us-gaap:DeferredIncomeTaxChargesMember2019-01-012019-12-310000005513us-gaap:DeferredIncomeTaxChargesMember2018-01-012018-12-310000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMember2018-01-010000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000005513us-gaap:AccumulatedNetUnrealizedInvestmentGainLossMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-01-012020-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-01-012019-12-310000005513us-gaap:InterestRateSwapMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-01-012018-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:ForeignExchangeContractMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-01-012020-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:ForeignExchangeContractMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-01-012019-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:ForeignExchangeContractMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-01-012018-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:ForwardContractsMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-01-012020-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:ForwardContractsMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-01-012019-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:ForwardContractsMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-01-012018-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2020-01-012020-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2019-01-012019-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember2018-01-012018-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember2020-01-012020-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember2019-01-012019-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember2018-01-012018-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember2020-01-012020-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember2019-01-012019-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberus-gaap:AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember2018-01-012018-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberunm:DefinedBenefitPlanCurtailmentGainLossMember2020-01-012020-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberunm:DefinedBenefitPlanCurtailmentGainLossMember2019-01-012019-12-310000005513us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMemberunm:DefinedBenefitPlanCurtailmentGainLossMember2018-01-012018-12-310000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2020-01-012020-12-310000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2019-01-012019-12-310000005513us-gaap:AccumulatedDefinedBenefitPlansAdjustmentMemberus-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember2018-01-012018-12-310000005513unm:AmountRelatedtoInterestMember2020-01-012020-12-310000005513unm:AmountRelatedtoInterestMember2019-01-012019-12-310000005513unm:AmountRelatedtoInterestMember2018-01-012018-12-310000005513unm:IncurredClaimsMember2020-01-012020-12-310000005513unm:IncurredClaimsMember2019-01-012019-12-310000005513unm:IncurredClaimsMember2018-01-012018-12-310000005513unm:ForeignCurrencyMember2020-01-012020-12-310000005513unm:ForeignCurrencyMember2019-01-012019-12-310000005513unm:ForeignCurrencyMember2018-01-012018-12-310000005513us-gaap:OperatingExpenseMember2020-01-012020-12-310000005513us-gaap:OperatingExpenseMember2019-01-012019-12-310000005513us-gaap:OperatingExpenseMember2018-01-012018-12-310000005513unm:ClosedBlockIndividualDisabilityReinsuranceTransactionMember2020-12-310000005513unm:ClaimReserveMember2020-01-012020-12-310000005513unm:ClaimReserveMember2018-01-012018-12-310000005513us-gaap:HerMajestysRevenueAndCustomsHMRCMemberus-gaap:ForeignCountryMember2020-01-012020-12-310000005513us-gaap:TaxYear2017Member2019-01-012019-12-310000005513unm:SubsidiaryReturnMemberus-gaap:DomesticCountryMember2020-12-310000005513us-gaap:StateAndLocalJurisdictionMember2020-12-310000005513unm:SecuredNotesIssuedin2007Memberus-gaap:SeniorNotesMember2020-12-310000005513unm:SecuredNotesIssuedin2007Memberus-gaap:SeniorNotesMember2019-12-310000005513unm:NotesIssuedin1998with2028MaturityDateMemberus-gaap:SeniorNotesMember2020-12-310000005513unm:NotesIssuedin1998with2028MaturityDateMemberus-gaap:SeniorNotesMember2019-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedin2002Member2020-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedin2002Member2019-12-310000005513unm:NotesPayabledue2042Memberus-gaap:SeniorNotesMember2020-12-310000005513unm:NotesPayabledue2042Memberus-gaap:SeniorNotesMember2019-12-310000005513unm:NotesIssuedin2014Memberus-gaap:SeniorNotesMember2020-12-310000005513unm:NotesIssuedin2014Memberus-gaap:SeniorNotesMember2019-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedin2015Member2020-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedin2015Member2019-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedIn2019Member2020-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedIn2019Member2019-12-310000005513unm:NotesIssuedIn2019Due2049Memberus-gaap:SeniorNotesMember2020-12-310000005513unm:NotesIssuedIn2019Due2049Memberus-gaap:SeniorNotesMember2019-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedIn2020Due2025Member2020-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedIn2020Due2025Member2019-12-310000005513us-gaap:MediumTermNotesMemberunm:NotesIssued1990to1996Member2020-12-310000005513us-gaap:MediumTermNotesMemberunm:NotesIssued1990to1996Member2019-12-310000005513us-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin1998with2038MaturityDateMember2020-12-310000005513us-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin1998with2038MaturityDateMember2019-12-310000005513us-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin2018witha2058MaturityDateMember2020-12-310000005513us-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin2018witha2058MaturityDateMember2019-12-310000005513unm:FairValueHedgeAdjustmentLtDebtMember2020-12-310000005513unm:FairValueHedgeAdjustmentLtDebtMember2019-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedin2010Member2019-12-310000005513unm:NorthwindHoldingsLlcMember2007-01-012007-12-310000005513unm:NorthwindHoldingsLlcMember2020-01-012020-12-310000005513unm:NorthwindHoldingsLlcMember2018-01-012018-12-310000005513unm:NorthwindHoldingsLlcMember2019-01-012019-12-310000005513unm:SecuredNotesIssuedin2007Memberus-gaap:SeniorNotesMember2020-01-012020-12-310000005513unm:Notes5625Due2020Member2020-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedin2010Member2020-12-310000005513unm:A4500SeniorNotesDue2025Memberus-gaap:SeniorNotesMember2020-01-012020-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedIn2020Due2025Member2020-12-310000005513unm:MediumTermNotesPayableDue2028Memberus-gaap:MediumTermNotesMember2019-01-012019-12-310000005513unm:MediumTermNotesPayableDue2028Memberus-gaap:MediumTermNotesMember2019-12-310000005513unm:NotesIssuedin1998with2028MaturityDateMemberus-gaap:SeniorNotesMember2020-01-012020-12-310000005513unm:NotesIssuedin1998with2028MaturityDateMemberus-gaap:SeniorNotesMember2019-12-310000005513us-gaap:SeniorNotesMemberunm:SeniorNotesPayableDue2021Member2019-01-012019-12-310000005513us-gaap:SeniorNotesMemberunm:SeniorNotesPayableDue2021Member2019-12-310000005513unm:NotesIssuedIn2019Due2049Memberus-gaap:SeniorNotesMember2019-01-012019-12-310000005513us-gaap:SeniorNotesMemberunm:NotesIssuedIn2019Member2019-01-012019-12-310000005513srt:ParentCompanyMemberunm:NotesIssuedin1998with2018MaturityDateMember2018-12-310000005513us-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin2018witha2058MaturityDateMember2018-01-012018-12-310000005513us-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin2018witha2058MaturityDateMember2018-12-310000005513us-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin1998with2038MaturityDateMember1998-01-011998-12-310000005513unm:JuniorSubordinatedNotesPayableDue2038Memberus-gaap:JuniorSubordinatedDebtMember2020-12-310000005513unm:CapitalSecuritiesNotesPayableDue2038Member2019-01-012019-12-310000005513unm:JuniorSubordinatedNotesPayableDue2038Memberus-gaap:JuniorSubordinatedDebtMember2019-01-012019-12-310000005513unm:CapitalSecuritiesNotesPayableDue2038Member2019-12-310000005513srt:ParentCompanyMemberunm:FiveYearUnsecuredRevolvingCreditFacilityMember2020-12-310000005513srt:ParentCompanyMemberunm:ThreeYearUnsecuredRevolvingCreditFacilityMember2020-12-310000005513country:USunm:GroupAnnuityContactMemberus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000005513country:USunm:GroupAnnuityContactMemberus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000005513country:USus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000005513country:GBus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000005513country:USus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:PensionPlansDefinedBenefitMember2018-12-310000005513country:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:GBus-gaap:PensionPlansDefinedBenefitMember2018-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2018-12-310000005513country:USus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000005513country:GBus-gaap:PensionPlansDefinedBenefitMember2019-01-012019-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-01-012020-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-01-012019-12-310000005513country:USus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:EquitySecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:DebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:AlternativeInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513unm:DiversifiedGrowthAssetsMembercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:InterestRateContractMembercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:DefinedBenefitPlanEquitySecuritiesSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberus-gaap:DefinedBenefitPlanEquitySecuritiesSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberus-gaap:DefinedBenefitPlanEquitySecuritiesSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:DefinedBenefitPlanEquitySecuritiesSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:DefinedBenefitPlanEquitySecuritiesSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513unm:DefinedBenefitPlanEquitySecuritiesGlobalMembercountry:USus-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513unm:DefinedBenefitPlanEquitySecuritiesGlobalMembercountry:USus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513unm:DefinedBenefitPlanEquitySecuritiesGlobalMembercountry:USus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513unm:DefinedBenefitPlanEquitySecuritiesGlobalMembercountry:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513unm:DefinedBenefitPlanEquitySecuritiesGlobalMembercountry:USus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberunm:DefinedBenefitPlanEquitySecuritiesInternationalMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesInternationalMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesInternationalMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesInternationalMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesInternationalMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberunm:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:USTreasuryAndGovernmentMembercountry:USus-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:USTreasuryAndGovernmentMembercountry:USus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:USTreasuryAndGovernmentMembercountry:USus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:USTreasuryAndGovernmentMembercountry:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:USTreasuryAndGovernmentMembercountry:USus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:CorporateDebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberus-gaap:CorporateDebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberus-gaap:CorporateDebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:CorporateDebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberus-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberus-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberunm:OpportunisticCreditsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:OpportunisticCreditsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:OpportunisticCreditsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:OpportunisticCreditsMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:OpportunisticCreditsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberunm:PrivateEquityFundsPrivateEquityDirectInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberunm:PrivateEquityFundsPrivateEquityDirectInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberunm:PrivateEquityFundsPrivateEquityDirectInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:PrivateEquityFundsPrivateEquityDirectInvestmentsMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USunm:PrivateEquityFundsPrivateEquityDirectInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:USus-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:USus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:USus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:USus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberunm:TotalInvestedAssetsMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberunm:TotalInvestedAssetsMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberunm:TotalInvestedAssetsMember2020-12-310000005513country:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMemberunm:TotalInvestedAssetsMember2020-12-310000005513country:USus-gaap:PensionPlansDefinedBenefitMemberunm:TotalInvestedAssetsMember2020-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:DefinedBenefitPlanEquitySecuritiesUsLargeCapMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:DefinedBenefitPlanEquitySecuritiesSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberus-gaap:DefinedBenefitPlanEquitySecuritiesSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberus-gaap:DefinedBenefitPlanEquitySecuritiesSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:DefinedBenefitPlanEquitySecuritiesSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:DefinedBenefitPlanEquitySecuritiesSmallCapMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513unm:DefinedBenefitPlanEquitySecuritiesGlobalMembercountry:USus-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513unm:DefinedBenefitPlanEquitySecuritiesGlobalMembercountry:USus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513unm:DefinedBenefitPlanEquitySecuritiesGlobalMembercountry:USus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513unm:DefinedBenefitPlanEquitySecuritiesGlobalMembercountry:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513unm:DefinedBenefitPlanEquitySecuritiesGlobalMembercountry:USus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberunm:DefinedBenefitPlanEquitySecuritiesInternationalMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesInternationalMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesInternationalMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesInternationalMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesInternationalMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberunm:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:DefinedBenefitPlanEquitySecuritiesEmergingMarketsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:USTreasuryAndGovernmentMembercountry:USus-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:USTreasuryAndGovernmentMembercountry:USus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:USTreasuryAndGovernmentMembercountry:USus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:USTreasuryAndGovernmentMembercountry:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:USTreasuryAndGovernmentMembercountry:USus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:CorporateDebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberus-gaap:CorporateDebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberus-gaap:CorporateDebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:CorporateDebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:CorporateDebtSecuritiesMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberus-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberus-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:USStatesAndPoliticalSubdivisionsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberunm:OpportunisticCreditsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:OpportunisticCreditsMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:OpportunisticCreditsMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:OpportunisticCreditsMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:OpportunisticCreditsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:DefinedBenefitPlanRealEstateMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberunm:PrivateEquityFundsPrivateEquityDirectInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberunm:PrivateEquityFundsPrivateEquityDirectInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberunm:PrivateEquityFundsPrivateEquityDirectInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:PrivateEquityFundsPrivateEquityDirectInvestmentsMemberus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USunm:PrivateEquityFundsPrivateEquityDirectInvestmentsMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:USus-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:USus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:USus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:USus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel1Memberus-gaap:PensionPlansDefinedBenefitMemberunm:TotalInvestedAssetsMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel2Memberus-gaap:PensionPlansDefinedBenefitMemberunm:TotalInvestedAssetsMember2019-12-310000005513country:USus-gaap:FairValueInputsLevel3Memberus-gaap:PensionPlansDefinedBenefitMemberunm:TotalInvestedAssetsMember2019-12-310000005513country:USus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMemberunm:TotalInvestedAssetsMember2019-12-310000005513country:USus-gaap:PensionPlansDefinedBenefitMemberunm:TotalInvestedAssetsMember2019-12-310000005513srt:MinimumMemberus-gaap:PrivateEquityFundsMembercountry:USus-gaap:PensionPlansDefinedBenefitMember2020-01-012020-12-310000005513us-gaap:PrivateEquityFundsMembercountry:USus-gaap:PensionPlansDefinedBenefitMembersrt:MaximumMember2020-01-012020-12-310000005513unm:DiversifiedGrowthAssetsMemberus-gaap:FairValueInputsLevel1Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513unm:DiversifiedGrowthAssetsMemberus-gaap:FairValueInputsLevel2Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513unm:DiversifiedGrowthAssetsMemberus-gaap:FairValueInputsLevel3Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513unm:DiversifiedGrowthAssetsMembercountry:GBus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:FairValueInputsLevel1Membercountry:GBus-gaap:PensionPlansDefinedBenefitMemberunm:FixedInterestandIndexlinkedSecuritiesMember2020-12-310000005513us-gaap:FairValueInputsLevel2Membercountry:GBus-gaap:PensionPlansDefinedBenefitMemberunm:FixedInterestandIndexlinkedSecuritiesMember2020-12-310000005513us-gaap:FairValueInputsLevel3Membercountry:GBus-gaap:PensionPlansDefinedBenefitMemberunm:FixedInterestandIndexlinkedSecuritiesMember2020-12-310000005513country:GBus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMemberunm:FixedInterestandIndexlinkedSecuritiesMember2020-12-310000005513country:GBus-gaap:PensionPlansDefinedBenefitMemberunm:FixedInterestandIndexlinkedSecuritiesMember2020-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:FairValueInputsLevel1Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:FairValueInputsLevel2Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:FairValueInputsLevel3Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:GBus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:FairValueInputsLevel1Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:FairValueInputsLevel2Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513us-gaap:FairValueInputsLevel3Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513country:GBus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2020-12-310000005513unm:DiversifiedGrowthAssetsMemberus-gaap:FairValueInputsLevel1Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513unm:DiversifiedGrowthAssetsMemberus-gaap:FairValueInputsLevel2Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513unm:DiversifiedGrowthAssetsMemberus-gaap:FairValueInputsLevel3Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513unm:DiversifiedGrowthAssetsMembercountry:GBus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513unm:DiversifiedGrowthAssetsMembercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:FairValueInputsLevel1Membercountry:GBus-gaap:PensionPlansDefinedBenefitMemberunm:FixedInterestandIndexlinkedSecuritiesMember2019-12-310000005513us-gaap:FairValueInputsLevel2Membercountry:GBus-gaap:PensionPlansDefinedBenefitMemberunm:FixedInterestandIndexlinkedSecuritiesMember2019-12-310000005513us-gaap:FairValueInputsLevel3Membercountry:GBus-gaap:PensionPlansDefinedBenefitMemberunm:FixedInterestandIndexlinkedSecuritiesMember2019-12-310000005513country:GBus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMemberunm:FixedInterestandIndexlinkedSecuritiesMember2019-12-310000005513country:GBus-gaap:PensionPlansDefinedBenefitMemberunm:FixedInterestandIndexlinkedSecuritiesMember2019-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:FairValueInputsLevel1Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:FairValueInputsLevel2Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMemberus-gaap:FairValueInputsLevel3Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:GBus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:DefinedBenefitPlanCashAndCashEquivalentsMembercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:FairValueInputsLevel1Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:FairValueInputsLevel2Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:FairValueInputsLevel3Membercountry:GBus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513country:GBus-gaap:FairValueMeasuredAtNetAssetValuePerShareMemberus-gaap:PensionPlansDefinedBenefitMember2019-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel2Member2020-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel3Member2020-12-310000005513us-gaap:FairValueInputsLevel1Memberus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel2Member2019-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel3Member2019-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel3Memberunm:LifeInsuranceContractsMember2019-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel3Memberunm:LifeInsuranceContractsMember2020-01-012020-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel3Memberunm:LifeInsuranceContractsMember2020-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel3Memberunm:LifeInsuranceContractsMember2018-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMemberus-gaap:FairValueInputsLevel3Memberunm:LifeInsuranceContractsMember2019-01-012019-12-310000005513country:USus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000005513country:GBus-gaap:PensionPlansDefinedBenefitMember2018-01-012018-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2018-01-012018-12-310000005513country:USus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2020-01-012020-12-31iso4217:GBP0000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembercountry:GB2020-01-012020-12-310000005513country:USus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2019-01-012019-12-310000005513country:USus-gaap:OtherPostretirementBenefitPlansDefinedBenefitMember2018-01-012018-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembercountry:GB2019-01-012019-12-310000005513us-gaap:OtherPostretirementBenefitPlansDefinedBenefitMembercountry:GB2018-01-012018-12-310000005513unm:RepurchaseProgramAuthorizedInMay2019Member2020-12-310000005513unm:RepurchaseProgramAuthorizedinMay2018Member2020-12-310000005513unm:OpenMarketRepurchaseMember2020-01-012020-12-310000005513unm:OpenMarketRepurchaseMember2019-01-012019-12-310000005513unm:OpenMarketRepurchaseMember2018-01-012018-12-310000005513unm:StockIncentivePlan2017Domain2020-12-310000005513unm:StockIncentivePlan2017Domain2020-01-012020-12-310000005513unm:StockIncentivePlan2012Domain2020-12-310000005513unm:StockIncentivePlan2012Domain2020-01-012020-12-310000005513unm:StockSuccessUnitMember2020-01-012020-12-310000005513unm:StockSuccessUnitMember2019-12-310000005513unm:StockSuccessUnitMember2020-12-310000005513us-gaap:PerformanceSharesMember2020-01-012020-12-310000005513us-gaap:PerformanceSharesMember2019-12-310000005513us-gaap:PerformanceSharesMember2020-12-310000005513us-gaap:PerformanceSharesMember2019-01-012019-12-310000005513us-gaap:PerformanceSharesMember2018-01-012018-12-310000005513srt:MinimumMemberus-gaap:PerformanceSharesMember2020-12-310000005513us-gaap:PerformanceSharesMembersrt:MaximumMember2020-12-310000005513us-gaap:RestrictedStockUnitsRSUMember2020-01-012020-12-310000005513us-gaap:RestrictedStockUnitsRSUMember2019-12-310000005513us-gaap:RestrictedStockUnitsRSUMember2020-12-310000005513us-gaap:RestrictedStockUnitsRSUMember2019-01-012019-12-310000005513us-gaap:RestrictedStockUnitsRSUMember2018-01-012018-12-310000005513srt:MinimumMemberus-gaap:RestrictedStockUnitsRSUMember2020-01-012020-12-310000005513us-gaap:RestrictedStockUnitsRSUMembersrt:MaximumMember2020-01-012020-12-310000005513unm:CashSettledRSUsMember2020-01-012020-12-310000005513unm:CashSettledRSUsMember2019-12-310000005513unm:CashSettledRSUsMember2020-12-310000005513srt:MinimumMemberunm:CashSettledRSUsMember2020-01-012020-12-310000005513unm:CashSettledRSUsMembersrt:MaximumMember2020-01-012020-12-310000005513us-gaap:EmployeeStockOptionMember2020-01-012020-12-310000005513us-gaap:EmployeeStockOptionMember2019-12-310000005513us-gaap:EmployeeStockOptionMember2020-12-310000005513srt:MinimumMemberus-gaap:EmployeeStockOptionMember2020-01-012020-12-310000005513us-gaap:EmployeeStockOptionMembersrt:MaximumMember2020-01-012020-12-310000005513unm:RestrictedstockunitsandcashsettledawardsDomain2020-01-012020-12-310000005513unm:RestrictedstockunitsandcashsettledawardsDomain2019-01-012019-12-310000005513unm:RestrictedstockunitsandcashsettledawardsDomain2018-01-012018-12-310000005513unm:StockSuccessUnitMember2019-01-012019-12-310000005513unm:StockSuccessUnitMember2018-01-012018-12-310000005513us-gaap:EmployeeStockOwnershipPlanESOPPlanDomain2020-01-012020-12-310000005513us-gaap:EmployeeStockOwnershipPlanESOPPlanDomain2019-01-012019-12-310000005513us-gaap:EmployeeStockOwnershipPlanESOPPlanDomain2018-01-012018-12-310000005513us-gaap:EmployeeStockOptionMember2019-01-012019-12-310000005513us-gaap:EmployeeStockOptionMember2018-01-012018-12-310000005513unm:ClosedBlockIndividualDisabilityReinsuranceTransactionMember2020-01-012020-12-310000005513unm:ClosedBlockIndividualDisabilityReinsuranceTransactionMember2020-12-160000005513us-gaap:ReinsurerConcentrationRiskMemberus-gaap:ReinsuranceRecoverableMemberunm:CommonwealthAnnuityAndLifeInsuranceCompanyMembersrt:AMBestARatingMember2020-01-012020-12-310000005513unm:Top9ReinsurersMemberus-gaap:ReinsurerConcentrationRiskMemberus-gaap:ReinsuranceRecoverableMembersrt:AMBestARatingMember2020-01-012020-12-310000005513unm:OtherReinsurersMemberus-gaap:ReinsurerConcentrationRiskMemberus-gaap:ReinsuranceRecoverableMembersrt:AMBestAMinusRatingMember2020-01-012020-12-310000005513unm:OtherReinsurersMemberus-gaap:ReinsurerConcentrationRiskMemberus-gaap:ReinsuranceRecoverableMemberunm:AMBestBelowAorNotRatedMember2020-01-012020-12-310000005513us-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:JaiminiHealthInc.Member2018-11-010000005513unm:JaiminiHealthInc.Member2018-01-012018-12-310000005513unm:UnumPolandMember2018-10-010000005513unm:UnumPolandMember2018-01-012018-12-310000005513unm:LeavelogicInc.Member2018-01-010000005513unm:LeavelogicInc.Member2018-01-012018-12-310000005513us-gaap:SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember2017-01-012017-12-310000005513us-gaap:SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember2018-12-310000005513us-gaap:SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember2018-01-012018-12-310000005513unm:GroupLongTermDisabilityMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:GroupLongTermDisabilityMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:GroupLongTermDisabilityMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:UnumUsMemberunm:GroupShortTermDisabilityMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:UnumUsMemberunm:GroupShortTermDisabilityMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:UnumUsMemberunm:GroupShortTermDisabilityMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:GroupLifeMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:GroupLifeMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:GroupLifeMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:UnumUsMemberunm:AccidentalDeathDismembermentMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:UnumUsMemberunm:AccidentalDeathDismembermentMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:UnumUsMemberunm:AccidentalDeathDismembermentMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:IndividualDisabilityInsuranceMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:IndividualDisabilityInsuranceMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:IndividualDisabilityInsuranceMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:VoluntaryBenefitsMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:VoluntaryBenefitsMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:VoluntaryBenefitsMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:DentalandVisionMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:DentalandVisionMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:DentalandVisionMemberunm:UnumUsMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:UnumUsMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:UnumUsMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:UnumUsMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:UnumInternationalMemberunm:GroupLongTermDisabilityMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:UnumInternationalMemberunm:GroupLongTermDisabilityMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:UnumInternationalMemberunm:GroupLongTermDisabilityMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:UnumInternationalMemberunm:GroupLifeMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:UnumInternationalMemberunm:GroupLifeMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:UnumInternationalMemberunm:GroupLifeMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:UnumInternationalMemberunm:SupplementalandVoluntaryInsuranceMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:UnumInternationalMemberunm:SupplementalandVoluntaryInsuranceMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:UnumInternationalMemberunm:SupplementalandVoluntaryInsuranceMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:UnumPolandMemberunm:UnumInternationalMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:UnumPolandMemberunm:UnumInternationalMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:UnumPolandMemberunm:UnumInternationalMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:UnumInternationalMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:UnumInternationalMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:UnumInternationalMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513us-gaap:AccidentAndHealthInsuranceSegmentMemberunm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513us-gaap:AccidentAndHealthInsuranceSegmentMemberunm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513us-gaap:AccidentAndHealthInsuranceSegmentMemberunm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:ColonialLifeMemberus-gaap:OperatingSegmentsMemberus-gaap:LifeInsuranceSegmentMember2020-01-012020-12-310000005513unm:ColonialLifeMemberus-gaap:OperatingSegmentsMemberus-gaap:LifeInsuranceSegmentMember2019-01-012019-12-310000005513unm:ColonialLifeMemberus-gaap:OperatingSegmentsMemberus-gaap:LifeInsuranceSegmentMember2018-01-012018-12-310000005513unm:CancerAndCriticalIllnessColonialMemberunm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:CancerAndCriticalIllnessColonialMemberunm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:CancerAndCriticalIllnessColonialMemberunm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:ClosedBlockMemberus-gaap:OperatingSegmentsMemberunm:LongTermCareMember2020-01-012020-12-310000005513unm:ClosedBlockMemberus-gaap:OperatingSegmentsMemberunm:LongTermCareMember2019-01-012019-12-310000005513unm:ClosedBlockMemberus-gaap:OperatingSegmentsMemberunm:LongTermCareMember2018-01-012018-12-310000005513unm:IndividualDisabilityInsuranceMemberunm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:IndividualDisabilityInsuranceMemberunm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:IndividualDisabilityInsuranceMemberunm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513us-gaap:OtherInsuranceProductLineMemberunm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513us-gaap:OtherInsuranceProductLineMemberunm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513us-gaap:OtherInsuranceProductLineMemberunm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513us-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513us-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513us-gaap:CorporateAndOtherMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513us-gaap:CorporateAndOtherMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513us-gaap:CorporateAndOtherMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:UnumUsMemberus-gaap:OperatingSegmentsMember2019-12-310000005513unm:UnumInternationalMemberus-gaap:OperatingSegmentsMember2019-12-310000005513unm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2019-12-310000005513us-gaap:OperatingSegmentsMember2019-12-310000005513unm:UnumUsMemberus-gaap:OperatingSegmentsMember2020-12-310000005513unm:UnumInternationalMemberus-gaap:OperatingSegmentsMember2020-12-310000005513unm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2020-12-310000005513us-gaap:OperatingSegmentsMember2020-12-310000005513unm:UnumUsMemberus-gaap:OperatingSegmentsMember2018-12-310000005513unm:UnumInternationalMemberus-gaap:OperatingSegmentsMember2018-12-310000005513unm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2018-12-310000005513us-gaap:OperatingSegmentsMember2018-12-310000005513unm:UnumUsMemberus-gaap:OperatingSegmentsMember2017-12-310000005513unm:UnumInternationalMemberus-gaap:OperatingSegmentsMember2017-12-310000005513unm:ColonialLifeMemberus-gaap:OperatingSegmentsMember2017-12-310000005513us-gaap:OperatingSegmentsMember2017-12-310000005513unm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2020-12-310000005513unm:ClosedBlockMemberus-gaap:OperatingSegmentsMember2019-12-310000005513us-gaap:CorporateAndOtherMemberus-gaap:OperatingSegmentsMember2020-12-310000005513us-gaap:CorporateAndOtherMemberus-gaap:OperatingSegmentsMember2019-12-310000005513unm:UnumUsMember2020-12-310000005513unm:UnumUsMember2019-12-310000005513unm:UnumInternationalMember2020-12-310000005513unm:UnumInternationalMember2019-12-310000005513unm:ColonialLifeMember2019-12-310000005513unm:ColonialLifeMember2020-12-310000005513unm:ClosedBlockIndividualDisabilityReinsuranceTransactionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:ClosedBlockIndividualDisabilityReinsuranceTransactionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:ClosedBlockIndividualDisabilityReinsuranceTransactionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513unm:UnrelatedToSignificantTransactionMemberus-gaap:OperatingSegmentsMember2020-01-012020-12-310000005513unm:UnrelatedToSignificantTransactionMemberus-gaap:OperatingSegmentsMember2019-01-012019-12-310000005513unm:UnrelatedToSignificantTransactionMemberus-gaap:OperatingSegmentsMember2018-01-012018-12-310000005513srt:MinimumMemberus-gaap:LandAndBuildingMember2020-12-310000005513us-gaap:LandAndBuildingMembersrt:MaximumMember2020-12-310000005513srt:MinimumMemberus-gaap:MachineryAndEquipmentMember2020-12-310000005513us-gaap:MachineryAndEquipmentMembersrt:MaximumMember2020-12-310000005513unm:UnumLifeInsuranceCompanyOfAmericaMember2018-12-310000005513unm:UnumLifeInsuranceCompanyOfAmericaMember2020-01-012020-12-310000005513unm:FairwindInsuranceCompanyMember2020-01-012020-12-310000005513unm:FairwindInsuranceCompanyMember2019-01-012019-12-310000005513unm:UnitedStatesTraditionalInsuranceSubsidiariesMember2020-01-012020-12-310000005513unm:UnitedStatesTraditionalInsuranceSubsidiariesMember2019-01-012019-12-310000005513unm:UnitedStatesTraditionalInsuranceSubsidiariesMember2018-01-012018-12-310000005513unm:CaptiveReinsurersMember2020-01-012020-12-310000005513unm:CaptiveReinsurersMember2019-01-012019-12-310000005513unm:CaptiveReinsurersMember2018-01-012018-12-310000005513unm:UnitedStatesTraditionalInsuranceSubsidiariesMember2020-12-310000005513unm:UnitedStatesTraditionalInsuranceSubsidiariesMember2019-12-310000005513unm:CaptiveReinsurersMember2020-12-310000005513unm:CaptiveReinsurersMember2019-12-310000005513unm:UnumLimitedMember2019-01-012019-12-310000005513unm:UnumLimitedMember2019-12-310000005513unm:UnumLimitedMember2020-12-3100000055132020-10-012020-12-3100000055132020-07-012020-09-3000000055132020-04-012020-06-3000000055132020-01-012020-03-3100000055132019-10-012019-12-3100000055132019-07-012019-09-3000000055132019-04-012019-06-3000000055132019-01-012019-03-310000005513us-gaap:USTreasuryAndGovernmentMember2020-12-310000005513us-gaap:USStatesAndPoliticalSubdivisionsMember2020-12-310000005513us-gaap:ForeignGovernmentDebtMember2020-12-310000005513us-gaap:PublicUtilityBondsMember2020-12-310000005513us-gaap:AssetBackedSecuritiesMember2020-12-310000005513us-gaap:AllOtherCorporateBondsMember2020-12-310000005513us-gaap:MandatorilyRedeemablePreferredStockMember2020-12-310000005513us-gaap:FixedMaturitiesMember2020-12-310000005513us-gaap:MortgagesMember2020-12-310000005513us-gaap:PolicyLoansMember2020-12-310000005513us-gaap:DerivativeMember2020-12-310000005513us-gaap:EquitySecuritiesInvestmentSummaryMember2020-12-310000005513us-gaap:PrivateEquityFundsMember2020-12-310000005513us-gaap:OtherLongTermInvestmentsMember2020-12-310000005513us-gaap:ShortTermInvestmentsMember2020-12-310000005513srt:ParentCompanyMember2020-01-012020-12-310000005513srt:ParentCompanyMember2020-12-310000005513srt:ParentCompanyMember2019-12-310000005513srt:ParentCompanyMember2019-01-012019-12-310000005513srt:ParentCompanyMember2018-01-012018-12-310000005513unm:NotesIssuedin1998with2028MaturityDateMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2020-12-310000005513unm:NotesIssuedin1998with2028MaturityDateMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2019-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedin2002Member2020-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedin2002Member2019-12-310000005513srt:ParentCompanyMemberunm:NotesIssuedin2012and2016Memberus-gaap:SeniorNotesMember2020-12-310000005513srt:ParentCompanyMemberunm:NotesIssuedin2012and2016Memberus-gaap:SeniorNotesMember2019-12-310000005513srt:ParentCompanyMemberunm:NotesIssuedin2014Memberus-gaap:SeniorNotesMember2020-12-310000005513srt:ParentCompanyMemberunm:NotesIssuedin2014Memberus-gaap:SeniorNotesMember2019-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedin2015Member2020-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedin2015Member2019-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedIn2019Member2020-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedIn2019Member2019-12-310000005513srt:ParentCompanyMemberunm:NotesIssuedIn2019Due2049Memberus-gaap:SeniorNotesMember2020-12-310000005513srt:ParentCompanyMemberunm:NotesIssuedIn2019Due2049Memberus-gaap:SeniorNotesMember2019-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedIn2020Due2025Member2020-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedIn2020Due2025Member2019-12-310000005513srt:ParentCompanyMemberus-gaap:MediumTermNotesMemberunm:NotesIssued1990to1996Member2020-12-310000005513srt:ParentCompanyMemberus-gaap:MediumTermNotesMemberunm:NotesIssued1990to1996Member2019-12-310000005513srt:ParentCompanyMemberus-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin1998with2038MaturityDateMember2020-12-310000005513srt:ParentCompanyMemberus-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin1998with2038MaturityDateMember2019-12-310000005513srt:ParentCompanyMemberus-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin2018witha2058MaturityDateMember2020-12-310000005513srt:ParentCompanyMemberus-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin2018witha2058MaturityDateMember2019-12-310000005513srt:ParentCompanyMemberunm:FairValueHedgeAdjustmentLtDebtMember2020-12-310000005513srt:ParentCompanyMemberunm:FairValueHedgeAdjustmentLtDebtMember2019-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedin2010Member2020-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedin2010Member2019-12-310000005513srt:ParentCompanyMemberunm:NotesIssuedin2010Memberus-gaap:SeniorNotesMember2020-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedIn2020Due2025Member2020-01-012020-12-310000005513srt:ParentCompanyMemberunm:MediumTermNotesPayableDue2028Memberus-gaap:MediumTermNotesMember2019-01-012019-12-310000005513srt:ParentCompanyMemberunm:MediumTermNotesPayableDue2028Memberus-gaap:MediumTermNotesMember2019-12-310000005513unm:NotesIssuedin1998with2028MaturityDateMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2019-01-012019-12-310000005513unm:NotesIssuedin1998with2028MaturityDateMembersrt:ParentCompanyMemberus-gaap:SeniorNotesMember2019-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:SeniorNotesPayableDue2021Member2019-01-012019-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:SeniorNotesPayableDue2021Member2019-12-310000005513srt:ParentCompanyMemberunm:NotesIssuedIn2019Due2049Memberus-gaap:SeniorNotesMember2019-01-012019-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedIn2019Member2019-01-012019-12-310000005513srt:ParentCompanyMemberus-gaap:SeniorNotesMemberunm:NotesIssuedin1998with2018MaturityDateMember2018-12-310000005513unm:DerivativeFinancialInstrumentsReceiveFixedPayVariableMembersrt:ParentCompanyMemberus-gaap:InterestRateSwapMember2019-12-310000005513srt:ParentCompanyMemberus-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin2018witha2058MaturityDateMember2018-01-012018-12-310000005513srt:ParentCompanyMemberus-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin2018witha2058MaturityDateMember2018-12-310000005513srt:ParentCompanyMemberus-gaap:JuniorSubordinatedDebtMemberunm:NotesIssuedin1998with2038MaturityDateMember1998-01-011998-12-310000005513srt:ParentCompanyMemberunm:JuniorSubordinatedNotesPayableDue2038Memberus-gaap:JuniorSubordinatedDebtMember2020-12-310000005513srt:ParentCompanyMemberunm:CapitalSecuritiesNotesPayableDue2038Member2020-01-012020-12-310000005513srt:ParentCompanyMemberunm:JuniorSubordinatedNotesPayableDue2038Memberus-gaap:JuniorSubordinatedDebtMember2020-01-012020-12-310000005513unm:ClosedBlockMember2020-12-310000005513unm:ClosedBlockMember2019-12-310000005513unm:UnumUsMember2020-01-012020-12-310000005513unm:UnumInternationalMember2020-01-012020-12-310000005513unm:ColonialLifeMember2020-01-012020-12-310000005513unm:ClosedBlockMember2020-01-012020-12-310000005513us-gaap:CorporateAndOtherMember2020-01-012020-12-310000005513unm:UnumUsMember2019-01-012019-12-310000005513unm:UnumInternationalMember2019-01-012019-12-310000005513unm:ColonialLifeMember2019-01-012019-12-310000005513unm:ClosedBlockMember2019-01-012019-12-310000005513us-gaap:CorporateAndOtherMember2019-01-012019-12-310000005513unm:UnumUsMember2018-01-012018-12-310000005513unm:UnumInternationalMember2018-01-012018-12-310000005513unm:ColonialLifeMember2018-01-012018-12-310000005513unm:ClosedBlockMember2018-01-012018-12-310000005513us-gaap:CorporateAndOtherMember2018-01-012018-12-310000005513us-gaap:LifeInsuranceSegmentMember2020-01-012020-12-310000005513us-gaap:AccidentAndHealthInsuranceSegmentMember2020-01-012020-12-310000005513us-gaap:LifeInsuranceSegmentMember2019-01-012019-12-310000005513us-gaap:AccidentAndHealthInsuranceSegmentMember2019-01-012019-12-310000005513us-gaap:LifeInsuranceSegmentMember2018-01-012018-12-310000005513us-gaap:AccidentAndHealthInsuranceSegmentMember2018-01-012018-12-310000005513us-gaap:AllowanceForLoanAndLeaseLossesRealEstateMember2019-12-310000005513us-gaap:AllowanceForLoanAndLeaseLossesRealEstateMember2020-01-012020-12-310000005513us-gaap:AllowanceForLoanAndLeaseLossesRealEstateMember2020-12-310000005513us-gaap:AllowanceForUncollectiblePremiumsReceivableMemberus-gaap:AccountingStandardsUpdate201613Membersrt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember2019-12-310000005513us-gaap:AllowanceForUncollectiblePremiumsReceivableMember2020-01-012020-12-310000005513us-gaap:AllowanceForUncollectiblePremiumsReceivableMember2020-12-310000005513us-gaap:AllowanceForReinsuranceRecoverableMemberus-gaap:AccountingStandardsUpdate201613Membersrt:CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember2019-12-310000005513us-gaap:AllowanceForReinsuranceRecoverableMember2020-01-012020-12-310000005513us-gaap:AllowanceForReinsuranceRecoverableMember2020-12-310000005513us-gaap:AllowanceForLoanAndLeaseLossesRealEstateMember2018-12-310000005513us-gaap:AllowanceForLoanAndLeaseLossesRealEstateMember2019-01-012019-12-310000005513us-gaap:AllowanceForUncollectiblePremiumsReceivableMember2018-12-310000005513us-gaap:AllowanceForUncollectiblePremiumsReceivableMember2019-01-012019-12-310000005513us-gaap:AllowanceForUncollectiblePremiumsReceivableMember2019-12-310000005513us-gaap:AllowanceForLoanAndLeaseLossesRealEstateMember2017-12-310000005513us-gaap:AllowanceForLoanAndLeaseLossesRealEstateMember2018-01-012018-12-310000005513us-gaap:AllowanceForUncollectiblePremiumsReceivableMember2017-12-310000005513us-gaap:AllowanceForUncollectiblePremiumsReceivableMember2018-01-012018-12-31

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D. C. 20549

FORM 10-K

(Mark One)

☒ Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

For the fiscal year ended December 31, 2020

☐ Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

For the transition period from to

Commission file number 001-11294

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the registrant is a well-known seasoned issuer as defined in Rule 405 of the Securities Act. Yes [X] No [ ]

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes [ ] No [X]

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes [X] No [ ]

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes [X] No [ ]

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and "emerging growth company" in Rule 12b-2 of the Exchange Act.