SIGI


Line plots across dimensions of each concept
Line plots across concepts
Tables

Table of contents



us-gaap:CommonStockValue
us-gaap:ConsolidatedEntities

us-gaap:CommonStockSharesOutstanding

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareDiluted

us-gaap:BenefitsLossesAndExpenses

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:DeferredPolicyAcquisitionCostAmortizationExpense

us-gaap:GainLossOnInvestments
us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest
us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType

us-gaap:IncomeTaxExpenseBenefit
us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType

us-gaap:IncomeTaxesPaidNet

us-gaap:InterestExpenseDebt

us-gaap:NetIncomeLoss
us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType
us-gaap:StatementEquityComponents

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

us-gaap:NetInvestmentIncome
us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:InvestmentType

us-gaap:OperatingCostsAndExpenses

us-gaap:OtherComprehensiveIncomeLossNetOfTax
us-gaap:InformationByCategoryOfDebtSecurity
us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:OtherIncome
sigi:LineOfBusinessBySegment
us-gaap:StatementBusinessSegments

us-gaap:PreferredStockDividendsIncomeStatementImpact

us-gaap:RealizedInvestmentGainsLosses

us-gaap:Revenues
sigi:LineOfBusinessBySegment
us-gaap:StatementBusinessSegments

us-gaap:Assets
us-gaap:ConsolidatedEntities

us-gaap:Liabilities
us-gaap:ConsolidatedEntities

us-gaap:LiabilitiesAndStockholdersEquity
us-gaap:ConsolidatedEntities

us-gaap:StockholdersEquity
us-gaap:ConsolidatedEntities
us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:Cash
us-gaap:ConsolidatedEntities

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:EquitySecuritiesFvNi
us-gaap:ConsolidatedEntities
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:InvestmentType
us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency, us-gaap:InvestmentType

us-gaap:OtherAssets
us-gaap:ConsolidatedEntities

us-gaap:AccruedIncomeTaxesCurrent

us-gaap:LongTermDebt
us-gaap:ConsolidatedEntities
us-gaap:FairValueByMeasurementBasis
us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType

us-gaap:LongTermDebtAndCapitalLeaseObligations
us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType

us-gaap:DeferredIncomeTaxLiabilitiesNet
us-gaap:BalanceSheetLocation

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive
us-gaap:BalanceSheetLocation
us-gaap:OperatingLeaseLiability

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

us-gaap:StockholdersEquity
us-gaap:ConsolidatedEntities
us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:CommonStockValue
us-gaap:ConsolidatedEntities

us-gaap:AdditionalPaidInCapitalCommonStock
us-gaap:ConsolidatedEntities

us-gaap:RetainedEarningsAccumulatedDeficit
sigi:DividendsPaidToParent
us-gaap:ConsolidatedEntities

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax
us-gaap:ConsolidatedEntities
us-gaap:InformationByCategoryOfDebtSecurity
us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:StatementEquityComponents
us-gaap:StatementEquityComponents

us-gaap:TreasuryStockValue
us-gaap:ConsolidatedEntities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetIncomeLoss
us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType
us-gaap:StatementEquityComponents

us-gaap:ShareBasedCompensation

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:PaymentsOfDividendsCommonStock

us-gaap:PaymentsForRepurchaseOfCommonStock

us-gaap:ProceedsFromSaleOfShortTermInvestments

sigi:AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax

sigi:AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax
us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:StatementEquityComponents

sigi:AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax

sigi:ChangeInDirectPremiumsWritten
us-gaap:InvestmentType
sigi:Commercialmortgageloanallowanceforcreditloss

sigi:Commercialmortgageloansrealizedgains

sigi:ComprehensiveIncomeLossBeforeTax

sigi:ComprehensiveIncomeLossTax

sigi:Creditlossexpenseoninvestmentportfolio
us-gaap:InvestmentType

sigi:DebtAndEquitySecuritiesRealizedGains

sigi:DebtAndEquitySecuritiesRealizedLosses

sigi:DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross

sigi:DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet

sigi:DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax
us-gaap:RetirementPlanType
sigi:EffectiveInterestRateforCalculationofInterestCost
us-gaap:InvestmentType
sigi:EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLossSIGI

sigi:IncomeAvailableToCommonStockholdersBeforeTax

sigi:IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables

sigi:IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance

sigi:InterestPaidOperatingandInvestingActivities

sigi:LossReserveforCOVID19

sigi:LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell
us-gaap:InvestmentType
sigi:NetChangeInUnrealizedAppreciationDepreciationOfEquityMethodInvestees
us-gaap:InvestmentType
sigi:NetInvestmentIncomeOfEquityMethodInvestees

sigi:NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome

sigi:NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeGross

sigi:NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeTax

sigi:OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax

sigi:OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax

sigi:OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax

sigi:OTTILossesInvestmentsPortionRecognizedInEarningsNet
us-gaap:FinancialInstrument, us-gaap:InvestmentType
us-gaap:InvestmentType
us-gaap:StatementEquityComponents
sigi:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax

sigi:OtherImpairmentCharges
us-gaap:FinancialInstrument, us-gaap:InvestmentType
us-gaap:InvestmentType

sigi:OtherInvestmentsRealizedLosses

sigi:PaymentsToAcquireCommercialMortgageLoans

sigi:PaymentstoAcquireEquitySecurities

sigi:Paymentstoacquirecommercialmortgageloans
sigi:FloodCededPremiumsAndLosses
sigi:PercentageofunpaidNFIPclaimscededtofederalgovernment
us-gaap:FairValueByAssetClass, us-gaap:InvestmentType
sigi:PeriodchangeunrealizedgainslossesinOCI
us-gaap:FairValueByAssetClass, us-gaap:InvestmentType
sigi:Periodchangeunrealizedgainslossesinearnings

sigi:ProceedsfromSaleofEquitySecurities

sigi:Proceedsfromequityinvestmentsinexcessofcurrentyearearnings
us-gaap:InvestmentType
sigi:RealizedGainsLossesOfEquityMethodInvestees

sigi:Realizedandunrealizedinvestmentchange
us-gaap:InvestmentType
sigi:ShortTermInvestmentsAllowanceForCreditLoss

sigi:ShortTermInvestmentsRealizedGains

sigi:ShortTermInvestmentsRealizedLosses

sigi:Taxoninvestmentincome

sigi:TotalInvestmentsrevenue
us-gaap:StatementBusinessSegments
sigi:TotalSegmentIncomeLossFromContinuingOperationsBeforeFederalIncomeTax

sigi:TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross

sigi:TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax

sigi:TotalUnrealizedGainsLossesonInvestmentSecurities

sigi:Totalinvestmentsegmentincomeafterfederalincometax
us-gaap:StatementBusinessSegments
sigi:UnderwritingIncomeLossAfterFederalIncomeTaxes
us-gaap:StatementBusinessSegments
sigi:UnderwritingIncomeLossBeforeFederalIncomeTaxes

sigi:UnrealizedGainLossonEquitySecuritiesSold
us-gaap:StatementEquityComponents
us-gaap:AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
us-gaap:AssumedPremiumsEarned
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
us-gaap:AssumedPremiumsWritten
us-gaap:FinancialInstrument
us-gaap:AvailableForSaleSecuritiesGrossRealizedGains
us-gaap:FinancialInstrument
us-gaap:AvailableForSaleSecuritiesGrossRealizedLosses

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect
sigi:FloodCededPremiumsAndLosses
us-gaap:CededPremiumsEarned
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
sigi:FloodCededPremiumsAndLosses
us-gaap:CededPremiumsWritten
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
us-gaap:StatementBusinessSegments
us-gaap:CombinedRatio

us-gaap:CommonStockDividendsPerShareDeclared

us-gaap:CurrentFederalTaxExpenseBenefit

us-gaap:DebtAndEquitySecuritiesGainLoss
us-gaap:FinancialInstrument

us-gaap:DebtAndEquitySecuritiesRealizedGainLossExcludingOtherThanTemporaryImpairment

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded
us-gaap:FinancialInstrument, us-gaap:InvestmentType
us-gaap:InvestmentType

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal
us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold
us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery
us-gaap:FinancialInstrument, us-gaap:InvestmentType
us-gaap:FinancialInstrument, us-gaap:InvestmentType
us-gaap:DebtSecuritiesHeldToMaturityAllowanceForCreditLossPeriodIncreaseDecrease
us-gaap:InvestmentType

us-gaap:DeferredFederalIncomeTaxExpenseBenefit
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanInterestCost
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:DepreciationAmortizationAndAccretionNet
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
us-gaap:DirectPremiumsEarned
us-gaap:LossContingenciesByNatureOfContingency
us-gaap:ProductOrService, us-gaap:LossContingenciesByNatureOfContingency
sigi:PremiumTransactionType
us-gaap:DirectPremiumsWritten
sigi:PremiumTransactionType, us-gaap:LossContingenciesByNatureOfContingency
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
us-gaap:LossContingenciesByNatureOfContingency
us-gaap:ProductOrService, us-gaap:LossContingenciesByNatureOfContingency
us-gaap:StatementEquityComponents
us-gaap:DividendsCommonStock
us-gaap:StatementEquityComponents
us-gaap:DividendsPreferredStockCash

us-gaap:EquitySecuritiesFvNiRealizedLoss

us-gaap:EquitySecuritiesFvNiUnrealizedGainLoss
us-gaap:FairValueByAssetClass, us-gaap:IncomeStatementLocation, us-gaap:InvestmentType
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
us-gaap:FairValueByAssetClass, us-gaap:InvestmentType
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss
us-gaap:FairValueByAssetClass, us-gaap:InvestmentType
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
us-gaap:FairValueByAssetClass, us-gaap:InvestmentType
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
us-gaap:FairValueByAssetClass, us-gaap:InvestmentType
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3
us-gaap:FairValueByAssetClass, us-gaap:InvestmentType
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3

us-gaap:FinanceLeaseInterestPaymentOnLiability

us-gaap:FinanceLeasePrincipalPayments

us-gaap:GainLossOnDispositionOfAssets1

us-gaap:HeldtomaturitySecuritiesSoldSecurityRealizedGainLossExcludingOtherThanTemporaryImpairments

us-gaap:ImpairmentOfInvestments

us-gaap:IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions

us-gaap:IncreaseDecreaseInDeferredPolicyAcquisitionCosts

us-gaap:IncreaseDecreaseInEmployeeRelatedLiabilities

us-gaap:IncreaseDecreaseInIncomeTaxes

us-gaap:IncreaseDecreaseInInterestAndDividendsReceivable

us-gaap:IncreaseDecreaseInOtherOperatingAssets

us-gaap:IncreaseDecreaseInOtherOperatingLiabilities

us-gaap:IncreaseDecreaseInPremiumsReceivable

us-gaap:IncurredClaimsPropertyCasualtyAndLiability
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType

us-gaap:InvestmentIncomeInvestmentExpense

us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1

us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1

us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1

us-gaap:LossFromCatastrophes

us-gaap:NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1
sigi:ScheduleOfCashFlowSupplumentalDisclosures
us-gaap:NoncashOrPartNoncashAcquisitionInvestmentsAcquired1
us-gaap:InvestmentType

us-gaap:OperatingLeasePayments
us-gaap:InformationByCategoryOfDebtSecurity
us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossBeforeTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax
us-gaap:InformationByCategoryOfDebtSecurity
us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax
us-gaap:StatementEquityComponents

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax

us-gaap:OtherComprehensiveIncomeLossTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax

us-gaap:OtherGeneralExpense

us-gaap:OtherUnderwritingExpense
us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType

us-gaap:PaymentsForLossesAndLossAdjustmentExpense

us-gaap:PaymentsOfDividendsPreferredStockAndPreferenceStock

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt

us-gaap:PaymentsToAcquireHeldToMaturitySecurities

us-gaap:PaymentsToAcquireOtherInvestments

us-gaap:PaymentsToAcquireShortTermInvestments
sigi:LossReserve, us-gaap:ProductOrService
us-gaap:PolicyholderBenefitsAndClaimsIncurredGross
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
us-gaap:LossContingenciesByNatureOfContingency
us-gaap:ProductOrService, us-gaap:LossContingenciesByNatureOfContingency

us-gaap:PreferredStockDividendsPerShareDeclared
sigi:AllowanceforCreditLosses
us-gaap:PremiumReceivableCreditLossExpenseReversal

us-gaap:PremiumsEarnedNetPropertyAndCasualty
sigi:LineOfBusinessBySegment, us-gaap:StatementBusinessSegments
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
sigi:AllowanceforCreditLosses
us-gaap:PremiumsReceivableAllowanceForDoubtfulAccountsRecoveries
sigi:AllowanceforCreditLosses
us-gaap:PremiumsReceivableAllowanceForDoubtfulAccountsWriteOffsAgainstAllowance
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
us-gaap:PremiumsWrittenNet

us-gaap:ProceedsFromDebtNetOfIssuanceCosts

us-gaap:ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital

us-gaap:ProceedsFromIssuanceOfPreferredStockAndPreferenceStock

us-gaap:ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities

us-gaap:ProceedsFromSaleAndCollectionOfMortgageNotesReceivable

us-gaap:ProceedsFromSaleOfAvailableForSaleSecuritiesDebt

us-gaap:ProceedsFromSaleOfOtherInvestments
us-gaap:InformationByCategoryOfDebtSecurity
us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
us-gaap:StatementEquityComponents
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts
us-gaap:ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed
sigi:FloodCededPremiumsAndLosses
us-gaap:ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded
sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

us-gaap:ReinsuranceRecoverableCreditLossExpenseReversal

us-gaap:RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability

us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability

us-gaap:StockIssuedDuringPeriodSharesDividendReinvestmentPlan

us-gaap:StockIssuedDuringPeriodSharesShareBasedCompensation
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodValueDividendReinvestmentPlan
us-gaap:StatementEquityComponents
us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation

us-gaap:SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense
us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent
us-gaap:SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense
us-gaap:ProductOrService, us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent
us-gaap:ProductOrService, us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent, us-gaap:StatementBusinessSegments
us-gaap:ProductOrService, us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent, us-gaap:Subsegments

us-gaap:TreasuryStockSharesAcquired

us-gaap:TreasuryStockValueAcquiredCostMethod
us-gaap:StatementEquityComponents

us-gaap:UnrealizedGainLossOnInvestments

dei:EntityCommonStockSharesOutstanding
us-gaap:ConsolidatedEntities
sigi:AccruedLongTermStockCompensation
sigi:DividendsPaidToParent
sigi:Cashandinvestmentsheldatparent

sigi:CollateralOfReinsuranceRecoverables

sigi:CommercialMortgageLoanFairValue
us-gaap:FairValueByFairValueHierarchyLevel

sigi:CommercialMortgageLoansGross

sigi:Commercialmortgageloanfairvalue
us-gaap:FairValueByFairValueHierarchyLevel

sigi:CommercialmortgageloansGross

sigi:ConsolidatedNetWorthActual
us-gaap:InvestmentType
sigi:ContractualObligationAdditionalInvestmentinAlternativeorOtherInvestments

sigi:DebtSecuritiesHeldToMaturityGross

sigi:DebtSecuritiesHeldtomaturityGross

sigi:DebtToCapitalizationRatio

sigi:DeferredIncomeTaxExpenseBenefitOnInvestmentSecuritiesInOtherComprehensiveIncome

sigi:DeferredTaxAssetsUnrealizedLossesOnSecuritiesGross

sigi:DeferredTaxLiabilitiesInvestmentSecuritiesUnrealizedGain

sigi:DividendRestrictionNewYork
us-gaap:EquityMethodInvestmentNonconsolidatedInvestee
sigi:EquityMethodInvestmentSummarizedFinancialInformationAssetsSIGI
us-gaap:EquityMethodInvestmentNonconsolidatedInvestee
sigi:EquityMethodInvestmentSummarizedFinancialInformationEquitySIGI
us-gaap:InvestmentType
sigi:EquityMethodInvestmentSummarizedFinancialInformationLiabilitiesSIGI
us-gaap:InvestmentType
sigi:EquityMethodInvestmentsSummarizedFinancialInformationInvestments
us-gaap:RelatedPartyTransactionsByRelatedParty
sigi:EquityOwnershipPercentageOfSonOfDirectorOfParent
us-gaap:ConsolidatedEntities
sigi:IntercompanyNotesPayable
us-gaap:ConsolidatedEntities
sigi:InvestmentInSubsidiaries

sigi:LineOfCreditConsolidatedNetWorthRequirement
us-gaap:LongtermDebtType
sigi:LongTermDebtExcludingDebtDiscountAndDebtIssuanceCosts

sigi:MaximumexposuretocreditconcentrationriskoftheCompanysstockholdersequityotherthancertainU.S.governmentagencies

sigi:NetAssetValue

sigi:Netunrealizedgainlossesoninvestmentsecuritiesinothercomprehensiveincomenetofdeferredincometax

sigi:NewJerseyDividendRestriction

sigi:NewYorkDividendRestriction

sigi:PercentHedgeAgainstProjectedBenefitObligation
us-gaap:RelatedPartyTransaction
sigi:PercentageCommonStockOwnedbyRelatedParty
us-gaap:LongtermDebtType
sigi:PrincipalAccelerationAmountStateofDefault

sigi:PurchaseAmountOfAnnuities
sigi:InvestmentCategory
sigi:RemainingCommitment
sigi:InvestmentCategory, us-gaap:InvestmentType
us-gaap:InvestmentType

sigi:RemainingReinsuranceBalances
us-gaap:CededCreditRisk
us-gaap:AwardType
sigi:ShareBasedCompensationLiabilityAwardsAmountOfLiability
sigi:LineOfBusinessBySegment, us-gaap:ProductOrService, us-gaap:ShortdurationInsuranceContractsAccidentYear
sigi:ShortDurationInsuranceContractsIncurredButNotReportedIbnrClaimsLiabilityNetSIGI

sigi:StatutoryAccountingPracticesStatutoryUnassignedSurplus
sigi:StatutoryData

sigi:TerrorismRiskInsuranceProgramInsurerRetainer

sigi:TotalLeasesDueInFiveYears

sigi:TotalLeasesDueInFourYears

sigi:TotalLeasesDueInThreeYears

sigi:TotalLeasesDueInTwoYears

sigi:TotalLeasesDueNext12Months

sigi:TotalLeasesDueThereafter

sigi:TotalMinimumPaymentRequired

sigi:Totalimputedinterest

sigi:Totalleaseliability

sigi:UnrealizedGainLossOnInvestmentSecurities
us-gaap:InvestmentType

us-gaap:AccruedIncomeTaxes

us-gaap:AccruedInvestmentIncomeReceivable
us-gaap:InvestmentType

us-gaap:AccruedSalariesCurrentAndNoncurrent

us-gaap:AllowanceForLoanAndLeaseLossesRealEstate
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:AssetsFairValueDisclosure
us-gaap:FairValueByMeasurementFrequency

us-gaap:AssetsHeldByInsuranceRegulators
us-gaap:InvestmentType

us-gaap:AvailableForSaleDebtSecuritiesAmortizedCostBasis
us-gaap:ConsolidatedEntities

us-gaap:AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:AvailableForSaleSecuritiesAmortizedCost
us-gaap:FinancialInstrument, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:AvailableForSaleSecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLoss
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType

us-gaap:AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue

us-gaap:AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue

us-gaap:AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue

us-gaap:AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue

us-gaap:AvailableForSaleSecuritiesDebtSecurities
us-gaap:InvestmentType
us-gaap:ContractualObligation

us-gaap:DebtInstrumentUnamortizedDiscount
us-gaap:LongtermDebtType

us-gaap:DebtLongtermAndShorttermCombinedAmount

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLoss
us-gaap:ConsolidatedEntities
us-gaap:FinancialInstrument, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPosition
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime
us-gaap:DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss
sigi:ScheduleOfFairValueAndGrossPreTaxUnrealizedUnrecognizedLossOfSecuritiesByLengthOfTime, us-gaap:InvestmentType
us-gaap:FinancialInstrument

us-gaap:DebtSecuritiesHeldToMaturityAllowanceForCreditLoss

us-gaap:DeferredFinanceCostsGross

us-gaap:DeferredFinanceCostsNet
us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType
us-gaap:LongtermDebtType
us-gaap:ConsolidatedEntities
us-gaap:DeferredIncomeTaxAssetsNet

us-gaap:DeferredIncomeTaxLiabilities

us-gaap:DeferredPolicyAcquisitionCosts

us-gaap:DeferredTaxAssetsGross

us-gaap:DeferredTaxAssetsOther

us-gaap:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsEmployeeBenefits

us-gaap:DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost

us-gaap:DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsLossReserves

us-gaap:DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsUnearnedPremiumsReserve

us-gaap:DeferredTaxLiabilitiesDeferredExpenseDeferredPolicyAcquisitionCost

us-gaap:DeferredTaxLiabilitiesOther

us-gaap:DeferredTaxLiabilitiesPropertyPlantAndEquipment
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedBenefitObligation
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAccumulatedOtherComprehensiveIncomeNetGainsLossesBeforeTax
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAmountsRecognizedInBalanceSheet
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanBenefitObligation
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
us-gaap:RetirementPlanType
us-gaap:DefinedBenefitPlanFundedStatusOfPlan

us-gaap:DefinedBenefitPlanWeightedAverageAssetAllocations
us-gaap:DefinedBenefitPlanByPlanAssetCategories
us-gaap:RelatedPartyTransactionsByRelatedParty
us-gaap:DueToRelatedPartiesCurrent

us-gaap:DueToRelatedPartiesCurrentAndNoncurrent

us-gaap:EmployeeRelatedLiabilitiesCurrentAndNoncurrent
us-gaap:AwardType
us-gaap:EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized

us-gaap:EquitySecuritiesFvNiCost
us-gaap:FairValueByAssetClass, us-gaap:InvestmentType
us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue
dei:LegalEntity, us-gaap:ShortTermDebtType
us-gaap:FederalHomeLoanBankAdvances
us-gaap:ShortTermDebtType
us-gaap:SubsequentEventType
us-gaap:FederalHomeLoanBankAdvancesBranchOfFHLBBankAmountOfAdvancesByBranch
us-gaap:FederalHomeLoanBankAdvancesBranchOfFHLBBank
us-gaap:FederalHomeLoanBankAdvancesGeneralDebtObligationsDisclosuresCollateralPledged1
us-gaap:FederalHomeLoanBankAdvancesBranchOfFHLBBank, us-gaap:InvestmentType
dei:LegalEntity, us-gaap:ShortTermDebtType
us-gaap:FederalHomeLoanBankAdvancesInterestRate
us-gaap:ShortTermDebtType
us-gaap:FederalHomeLoanBankAdvancesBranchOfFHLBBank
us-gaap:FederalHomeLoanBankStock

us-gaap:FinanceLeaseLiability
us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType
us-gaap:LongtermDebtType

us-gaap:FinanceLeaseLiabilityPaymentsDue

us-gaap:FinanceLeaseLiabilityPaymentsDueNextTwelveMonths

us-gaap:FinanceLeaseLiabilityPaymentsDueYearThree

us-gaap:FinanceLeaseLiabilityPaymentsDueYearTwo

us-gaap:FinanceLeaseLiabilityUndiscountedExcessAmount

us-gaap:FinanceLeaseRightOfUseAsset

us-gaap:HeldToMaturitySecurities

us-gaap:HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue

us-gaap:HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount

us-gaap:HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue

us-gaap:HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount

us-gaap:HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue

us-gaap:HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount

us-gaap:HeldToMaturitySecuritiesFairValue
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:InvestmentType
us-gaap:InvestmentType
us-gaap:ConsolidatedEntities
us-gaap:IncomeTaxReceivable

us-gaap:IncomeTaxesReceivable

us-gaap:Investments
us-gaap:RelatedPartyTransaction, us-gaap:RetirementPlanType

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths

us-gaap:LiabilityForAsbestosAndEnvironmentalClaimsGross
sigi:ScheduleOfLiabilityForUnpaidAsbestosandEnvironmentalClaimsAndClaimsAdjustmentExpense

us-gaap:LiabilityForAsbestosAndEnvironmentalClaimsNet
sigi:ScheduleOfLiabilityForUnpaidAsbestosandEnvironmentalClaimsAndClaimsAdjustmentExpense

us-gaap:LiabilityForClaimsAndClaimsAdjustmentExpense

us-gaap:LiabilityForClaimsAndClaimsAdjustmentExpensePropertyCasualtyLiability

us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseNet
us-gaap:LongtermDebtType
us-gaap:LineOfCreditFacilityCurrentBorrowingCapacity
us-gaap:LongtermDebtType
us-gaap:LineOfCreditFacilityMaximumBorrowingCapacity

us-gaap:LongTermDebtAndCapitalLeaseObligationsIncludingCurrentMaturities
us-gaap:LongtermDebtType

us-gaap:LongTermDebtFairValue
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:LongtermDebtType
us-gaap:FairValueByMeasurementBasis
us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType
us-gaap:LongtermDebtType
us-gaap:LongtermDebtType
us-gaap:LongTermDebtPercentageBearingFixedInterestRate

us-gaap:MortgageLoansOnRealEstateCommercialAndConsumerNet

us-gaap:OtherInvestments
sigi:InvestmentCategory
sigi:InvestmentCategory, us-gaap:InvestmentType
us-gaap:ConsolidatedEntities
us-gaap:InvestmentType

us-gaap:OtherLiabilities
us-gaap:ConsolidatedEntities

us-gaap:OtherShortTermInvestments
us-gaap:ConsolidatedEntities
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency
us-gaap:FairValueByMeasurementFrequency

us-gaap:PreferredStockLiquidationPreferenceValue

us-gaap:PreferredStockSharesOutstanding

us-gaap:PreferredStockValue
us-gaap:ConsolidatedEntities

us-gaap:PremiumsReceivableAllowanceForDoubtfulAccounts
sigi:AllowanceforCreditLosses

us-gaap:PremiumsReceivableAtCarryingValue

us-gaap:PremiumsReceivableGross

us-gaap:PrepaidReinsurancePremiums

us-gaap:ReinsuranceRecoverableForUnpaidClaimsAndClaimsAdjustments
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
sigi:NonRatedReinsurer
us-gaap:ReinsuranceRecoverableNotPastDue
sigi:ReinsuranceRecoverable
us-gaap:CreditRatingAMBest
sigi:NonRatedReinsurer
us-gaap:ReinsuranceRecoverablePastDue
sigi:ReinsuranceRecoverable
us-gaap:CreditRatingAMBest

us-gaap:ReinsuranceRecoverables

us-gaap:ReinsuranceRecoverablesAllowance
sigi:AllowanceforCreditLosses
sigi:NonRatedReinsurer
us-gaap:ReinsuranceRecoverablesGross
us-gaap:CreditRatingAMBest

us-gaap:ReinsuranceRecoverablesOnUnpaidLossesGross

us-gaap:RestrictedCash

us-gaap:RestrictedCashAndCashEquivalentsAtCarryingValue

us-gaap:SalvageAndSubrogationRecoveriesValue

us-gaap:SecurityOwnedAndPledgedAsCollateralFairValue
us-gaap:InvestmentType
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
us-gaap:AwardType
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue
us-gaap:PlanName
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
us-gaap:PlanName
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
us-gaap:PlanName
us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant

us-gaap:ShortTermBorrowings
us-gaap:FairValueByMeasurementBasis, us-gaap:ShortTermDebtType
us-gaap:ShortTermDebtType
us-gaap:ShortTermDebtType
us-gaap:ShortTermDebtPercentageBearingFixedInterestRate

us-gaap:ShortdurationInsuranceContractsCumulativePaidClaimsAndAllocatedClaimAdjustmentExpenseNet
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsHistoricalClaimsDurationYearEight
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsHistoricalClaimsDurationYearFive
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsHistoricalClaimsDurationYearFour
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsHistoricalClaimsDurationYearNine
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsHistoricalClaimsDurationYearOne
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsHistoricalClaimsDurationYearSeven
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsHistoricalClaimsDurationYearSix
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsHistoricalClaimsDurationYearTen
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsHistoricalClaimsDurationYearThree
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsHistoricalClaimsDurationYearTwo

us-gaap:ShortdurationInsuranceContractsIncurredClaimsAndAllocatedClaimAdjustmentExpenseNet

us-gaap:ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNet
sigi:LineOfBusinessBySegment, us-gaap:ProductOrService
sigi:LineOfBusinessBySegment, us-gaap:ProductOrService, us-gaap:ShortdurationInsuranceContractsAccidentYear
us-gaap:ProductOrService, us-gaap:StatementBusinessSegments
us-gaap:ShortdurationInsuranceContractsAccidentYear

us-gaap:ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseAccumulatedUnallocatedClaimAdjustmentExpense

us-gaap:ShorttermDebtFairValue
us-gaap:FairValueByFairValueHierarchyLevel
us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:ShortTermDebtType
us-gaap:ShortTermDebtType

us-gaap:StatutoryAccountingPracticesStatutoryAmountAvailableForDividendPaymentsWithRegulatoryApproval
sigi:DividendsPaidToParent

us-gaap:StatutoryAccountingPracticesStatutoryCapitalAndSurplusBalance
sigi:StatutoryData

us-gaap:StockRepurchaseProgramAuthorizedAmount1

us-gaap:SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount
us-gaap:FinancialInstrument
us-gaap:FinancialInstrument, us-gaap:InvestmentType
us-gaap:InvestmentType

us-gaap:SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost
us-gaap:FinancialInstrument
us-gaap:FinancialInstrument, us-gaap:InvestmentType
us-gaap:InvestmentType
us-gaap:FinancialInstrument, us-gaap:InvestmentType
us-gaap:SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue

us-gaap:SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts
us-gaap:StatementBusinessSegments

us-gaap:SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves
us-gaap:StatementBusinessSegments

us-gaap:SupplementaryInsuranceInformationUnearnedPremiums
us-gaap:StatementBusinessSegments

us-gaap:UnearnedPremiums

us-gaap:ValuationAllowancesAndReservesBalance
sigi:InvestmentCategory
us-gaap:VariableInterestEntityEntityMaximumLossExposureAmount
sigi:InvestmentCategory, us-gaap:InvestmentType
us-gaap:InvestmentType

Plots across concepts


IncomeStatement
Other Comprehensive Income Loss Net Of Tax
Expenses
Interest Expense Debt
Balance Sheet
Goodwill
Assets
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents
Current Assets
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents
NonCurrent Assets
Goodwill
PropertyPlantAndEquipmentNet
Property Plant And Equipment Net
Liabilities
Other Liabilities
Noncurrent Liabilities
Deferred Income Tax Liabilities Net
Stockholders Equity
Accumulated Other Comprehensive Income Loss Net Of Tax
Per Share
Common Stock Dividends Per Share Declared
CashFlow
Net Cash Provided By Used In Investing Activities
NetCashProvidedByUsedInOperatingActivities
Share Based Compensation
NetCashProvidedByUsedInInvestingActivities
Net Cash Provided By Used In Investing Activities
NetCashProvidedByUsedInFinancingActivities
Net Cash Provided By Used In Financing Activities
DividendsAndRepurchase
Payments For Repurchase Of Common Stock
LesseeOperatingLeaseLiabilityPaymentsDue
Lessee Operating Lease Liability Undiscounted Excess Amount

Tables

  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:CommonStockValue ██████▇▇▇▇▇▇▇▆▆▆▆▆▆▅▅▅▅▅▅▅▄▄▄▄▃▃▃▃▃▂▂▂▂▂▂▁▁208.742208.576208.066207.923207.875207.665206.968206.843206.665206.451205.697205.573205.46205.28204.569204.361204.302204.057203.241203.011202.903202.518201.723201.348201.172200.861199.896199.507199.395199.073198.24197.914197.821197.416196.388196.028195.921195.62194.494194.089193.976193.678192.725NANANA
us-gaap:CommonStockSharesOutstanding NANA59.90580359.83470259.81174259.70754559.46115359.39956959.32810859.22290558.94855458.88898558.83505258.74750558.495122NANANA57.967199NANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:EarningsPerShareBasic █▇█▅▄▃▆▅▅▅▄▅▅▃▄▄▄▄▄▄▄▄▄▄▄▄▄▅▄▃▃▄▃▃▂▃▂▃▃▁▂▃▃▃▃▂1.991.782.121.170.570.261.380.941.221.040.770.941.00.320.520.80.710.870.680.660.750.640.790.820.590.70.730.940.520.320.450.590.490.380.020.330.010.330.3-0.370.040.40.440.320.350.11
us-gaap:EarningsPerShareDiluted █▇█▅▄▃▆▅▅▅▄▅▅▃▃▄▄▄▄▄▄▄▄▄▄▄▄▅▃▃▃▄▃▃▂▃▂▃▃▁▂▃▃▃▃▂1.981.772.11.160.570.251.360.931.211.020.760.930.990.320.510.790.70.850.670.660.740.630.780.810.580.690.720.930.510.310.440.570.480.380.020.330.010.330.29-0.370.040.390.430.320.350.11
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:BenefitsLossesAndExpenses ██▇█▇▇▇▇▆▇▆▆▆▆▅▅▅▅▅▄▄▄▄▃▃▃▃▃▃▄▃▃▂▂▃▂▂▂▁▃▂▁▁▁▁▁687.32668.275639.391691.309639.754648.832627.607639.247617.979625.268590.869597.341579.391606.758565.587553.978555.556532.895532.032526.248506.436499.599481.732474.618475.208467.602446.383440.032467.328483.987453.786442.328432.744431.081454.153416.558429.599396.157380.48434.897398.349375.684364.688367.642364.87385.465
us-gaap:ComprehensiveIncomeNetOfTax ▇▄▇▆█▁▅▅▆▆▅▄▄▂▄▄▅▅▂▄▅▅▄▄▃▄▃▄▄▄▄▄▂▄▂▄▃▄▄▃▄▃▃▄▄▃156.65423.684160.157104.999208.266-88.63165.18386.07137.748142.32860.3847.37642.545-44.46919.09753.53663.83368.48-38.79928.70479.61182.45442.00353.286-2.17643.53512.01334.27555.82434.65233.10330.458-35.52149.189-29.66344.7815.80828.78326.263-9.12220.69317.301-17.42147.59142.36512.49
us-gaap:DeferredPolicyAcquisitionCostAmortizationExpense █▇▆▆▅▅▅▅▄▄▃▃▂▂▂▂▁▁154.357149.051144.548142.291136.931136.501136.326136.572133.401129.674126.777124.511122.661121.093119.165118.143116.578115.35NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:GainLossOnInvestments ▇▆█▇▇▁▆▆▆▇▂▅▆▅▆▇▆▆10.0575.11920.0797.72112.649-44.666-0.873-2.1834.02713.451-37.935-4.787-1.652-10.549-1.1286.7981.734-1.045NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest █▇█▅▄▃▆▅▆▅▄▅▅▃▅▅▄▅▄▄▅▄▅▅▄▄▄▅▄▃▄▄▄▃▂▃▂▃▃▁▂▃▃▃153.198135.632159.04185.25742.69315.997101.29371.17890.22573.69452.13567.1372.52519.93168.1567.31558.92967.57450.32655.44362.31151.87563.79865.83946.76556.2957.275.32639.52125.08434.24844.48536.20128.868-5.17820.314-0.69223.19119.9-40.828-0.09926.15829.40122.06NANA
us-gaap:IncomeTaxExpenseBenefit ▇▇▇▅▅▄▆▅▆▅▄▅▅▄█▆▆▆▅▆▆▅▆▆▅▅▅▆▅▄▅▅▅▄▃▄▃▄▄▁▃▄▄▄▄▄31.31526.36231.9815.3828.510.76119.43415.02817.95912.3466.37511.69513.7061.00637.90820.59717.50317.13410.96616.94118.7114.84318.40918.84312.99716.58215.8522.16410.187.118.91311.8329.0796.563-6.4862.04-0.985.0983.767-21.336-1.1046.2235.5953.2292.7571.054
us-gaap:IncomeTaxesPaidNet NANA13.034.00.00.013.82514.028.00.022.03.07.0-2.80723.012.027.00.010.07.40521.08.021.010.04.54.018.01.01.6992.0NANANANANANANANANANANANANANANANA
us-gaap:InterestExpenseDebt ▄▄▄▄▄▄▄▄▄█▃▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁7.3667.3597.5297.7817.9287.6017.3797.3977.36611.5266.0696.0736.1256.1526.0826.0856.0816.1065.8315.7145.625.6065.975.4895.495.4795.5425.5585.4255.5615.5675.575.575.8314.7244.7254.7234.74.5844.5594.5594.5574.564.5594.6554.842
us-gaap:NetIncomeLoss █▇█▅▄▃▆▅▅▅▄▅▅▃▃▄▄▄▄▄▄▄▄▄▄▄▄▄▃▃▃▄▃▃▂▃▂▃▃▁▂▃▃▃▃▂121.883109.27127.06169.87534.18315.23681.85956.1572.26661.34845.7655.43558.81918.92530.24246.71841.42650.4439.3638.50243.60137.03245.38946.99633.76839.70841.3553.16229.34117.97425.33532.65327.12221.3081.30818.2740.28818.09316.133-20.1422.32521.54923.77517.19718.7665.803
us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic █▇█▄▂▁▅▄▅▄119.583106.817127.06169.87534.18315.23681.85956.1572.26661.348NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:NetInvestmentIncome █▆▆▆▂▅▅▅▅▄▄▄▃▃▃▃▃▂▂▂▂▁▁▂▂▁▂▂▂▂▂▂▂▂83.73169.71668.51168.18534.44455.96757.59455.82658.50550.61854.10952.44345.55343.23142.58740.44641.4337.41935.42833.37531.18230.76930.10832.06132.2326.91732.10834.29236.77435.53435.31332.45734.00332.87NANANANANANANANANANANANA
us-gaap:OperatingCostsAndExpenses ▆▆▄▂▄▆▁▄▆█▂▄▂▇▆▄▅█9.1129.5546.1023.9056.3459.062.5556.3699.56612.413.3817.453.28311.3329.5866.2898.46411.916NANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:OtherComprehensiveIncomeLossNetOfTax ▄▁▄▅█▁▃▄▅▆▄▃▃▂▃▄▄▄▂▃▅▅▄▄▃▄▃▃▄▄▄▄▂▄▃▄▄▄▄▄▄▄34.771-85.58633.09635.124174.083-103.867-16.67629.9265.48280.9814.62-8.059-16.274-63.394-11.1456.81822.40718.04-78.159-9.79836.0145.422-3.3866.29-35.9443.827-29.337-18.88726.48316.6787.768-2.195-62.64327.881-30.97126.5075.5210.6910.1311.0218.368-4.248NANANANA
us-gaap:OtherIncome ▅▄▄▅▄▂▃▃▃▂▂▂▃▂▂▂▃▃▂▂▃▁▂▁▃▂▂▃▂█▂▃▃▃▂▁▂▃▂▂▂▃▃▂▂▂6.2124.1124.9436.1194.6831.8253.823.1623.0532.321.5422.5383.1792.1792.191.9943.2913.2411.8632.1993.8680.9511.9350.6982.8541.9692.0143.1961.9119.8242.6173.3573.5362.7841.9891.0852.5113.5331.7351.3652.4992.882.9331.952.2472.268
us-gaap:PreferredStockDividendsIncomeStatementImpact ▁█2.32.453NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:RealizedInvestmentGainsLosses NANANA3.3836.948-27.529-0.31518.1341.9123.34-24.129-2.177-2.7673.519-1.1286.7981.734-1.045-7.6863.6881.765-2.704-2.60.308-3.4218.883-0.38915.2314.5397.218-1.20813.4315.1543.3555.54-1.0880.1784.358-3.621-2.0452.1465.76-3.8120.057-3.264-0.064
us-gaap:Revenues █▇▇▇▆▅▆▆▆▆▅▅▅▅▅▅▅▄▄▄▄▄▃▃▃▃▃▃▃▃▃▃▂▂▂▂▂▁▁▁▁▁▁▁▁▁840.518803.907798.432776.566682.447664.829728.9710.425708.204698.962643.004664.471651.916626.689633.737621.293614.485600.469582.358581.691568.747551.474545.53540.457521.973523.892503.583515.358506.849509.071488.034486.813468.945459.949448.975436.872428.907419.348400.38394.069399.57403.456394.089389.702387.718393.112
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:Assets ██▇▇▇▆▆▆▆▅▅▅▅▄▄▅▄▄▄▄▄▄▃▃▃▃▃▃▃▃▂▂▂▃▃▂▂▂▂▂▁▁▁10167.8719848.6129687.9139514.9269305.9628975.058797.158719.4068575.6058282.7617952.7297986.7527705.6737659.9497686.4317812.137528.2047404.0967355.8487363.2337189.6417022.4926904.4336898.1176784.3136701.1456581.556577.4196490.5856370.2366270.176266.3456112.6276344.0276794.2165879.9415687.4085629.5975736.3695748.995369.6485275.2265231.772NANANA
us-gaap:Liabilities ██▇█▇▇▆▆▆▆▅▆▅▅▅▅▅▅▅▅▄▄▄▄▄▄▄▄▃▃▃▃▃▃▄▂▂▂▂▂▁▁▁7276.5047104.5676949.0247121.3137007.2876878.5946602.2146582.036516.0616357.5396160.9276248.2326007.5186000.1535973.4746112.7785875.6485811.5175824.4785788.3295636.9045546.5275506.3925539.0955474.05385.2075305.9645310.4945252.515184.7055116.2425142.1365013.5825207.6825703.6244755.5634602.3624546.6794627.1414662.4354268.6144191.5734160.663NANANA
us-gaap:LiabilitiesAndStockholdersEquity ██▇▇▇▆▆▆▆▅▅▅▅▄▄▅▄▄▄▄▄▄▃▃▃▃▃▃▃▃▂▂▂▃▃▂▂▂▂▂▁▁▁10167.8719848.6129687.9139514.9269305.9628975.058797.158719.4068575.6058282.7617952.7297986.7527705.6737659.9497686.4317812.137528.2047404.0967355.8487363.2337189.6417022.4926904.4336898.1176784.3136701.1456581.556577.4196490.5856370.2366270.176266.3456112.6276344.0276794.2165879.9415687.4085629.5975736.3695748.995369.6485275.2265231.772NANANA
us-gaap:StockholdersEquity █▇▇▆▆▅▅▅▅▄▄▄▄▃▄▄▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁2891.3672744.0452738.8892393.6132298.6752096.4562194.9362137.3762059.5441925.2221791.8021738.521698.1551659.7961712.9571699.3521652.5561592.5791531.371574.9041552.7371475.9651398.0411359.0221310.3131315.9381275.5861266.9251238.0751185.5311153.9281124.2091099.0451136.3451090.5921124.3781085.0461082.9181109.2281086.5551101.0341083.6531071.1091092.3161049.5041010.162
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:Cash ▁▁▁▁▁▄▁▁▁▁▁▁▂▁▁▁▃▁▁▁▁▁▁▅▁▅█▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁0.450.4880.3940.7850.6669.4290.30.5160.5040.5160.5050.4464.8760.6740.5340.6948.6280.4830.4581.4931.530.6830.89815.1130.36814.80423.9592.5011.5470.2450.1930.1770.1540.2960.210.3150.1410.2610.7620.2870.1850.4960.6450.4220.5910.143
us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents ▂▂▃▃▁▃▁▂▁▂▃▂▃▃█▃▃▃▇9.2538.91615.23115.8955.63714.6067.97510.1637.64310.51416.91912.83216.4816.93244.7118.65916.7614.92137.405NANANA12.754NANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment ██▇▇▇▇▆▆▆▆▅▆▆▆▅▅▅▅▄▄▄▄▄▃▃▃▂▄▃▃▃▃▃▂▂▂▂▂▂▁▁▁▁251.533245.844240.15240.057237.021231.651227.566223.518219.67216.071211.657227.639220.874217.219213.227211.444206.847202.917198.729198.171193.997192.675188.548184.406180.146175.896172.183188.175184.748181.959179.192176.718174.226171.715169.428167.052164.835162.559160.294158.383156.209153.961151.704NANANA
us-gaap:PropertyPlantAndEquipmentNet ▇▇█████▇▇▆▅▅▅▅▅▆▆▆▆▆▆▅▆▆▅▅▄▄▄▃▃▃▃▃▂▂▂▂▂▁▁▁▁75.14276.09677.69678.44378.77180.06177.40976.42373.67868.6665.24864.22562.73162.04763.95966.33966.25568.50369.57669.81268.57365.16465.70165.65762.18261.85559.41655.53253.83653.72550.83450.0248.84148.32747.13145.96945.68943.91843.94739.24739.99840.7841.775NANANA
us-gaap:OperatingLeaseRightOfUseAsset NANA40.215NANA28.2726.53528.34829.63224.946NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:EquitySecuritiesFvNi █▇▇▃▃▂▁▁▃▃▃348.342324.255310.367151.824134.05899.98972.93779.213157.519163.016147.639NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:AccruedIncomeTaxesCurrent NANA14.021NANANA2.987NANANA1.302NANANA0.0NANANA0.0NANANA7.442NANANA3.921NANANA0.0NANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:LongTermDebt NANA550.743NANANA550.597NANA550.104439.54439.436439.331439.224439.116439.006438.894438.782438.667378.551328.433328.313388.192394.309394.305394.301379.297392.294392.29392.42392.414392.407392.4392.393307.387307.38307.373307.366307.36262.353262.346262.339262.333NANANA
 us-gaap:LongTermDebt us-gaap:ConsolidatedEntities srt:ParentCompanyNANA440.235NANANA439.86NANANA329.54NANANA329.116NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis us-gaap:CarryingReportedAmountFairValueDisclosureNANA550.743NANANA550.597NANANA439.54NANANA439.116NANANA438.667378.551328.433328.313388.192394.309394.305394.301379.297392.294392.29392.42392.414392.407NANA307.387NANANANANANANANANANANA
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis,us-gaap:LongtermDebtType us-gaap:CarryingReportedAmountFairValueDisclosure,sigi:FivePointThreeHundredSeventyFiveNANA294.241NANANA294.157NANA294.0970.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis,us-gaap:LongtermDebtType us-gaap:CarryingReportedAmountFairValueDisclosure,sigi:LongTermDebtExcludingIssuanceCostsNANA553.654NANANA553.547NANA553.471444.369NANANA444.35NANANA444.331384.326334.322334.318394.313NANANA379.297NANANANANANANANANANANANANANANANANANANA
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis,us-gaap:LongtermDebtType us-gaap:CarryingReportedAmountFairValueDisclosure,sigi:OnePointFiftySixPercentBorrowingFromFederalHomeLoanBankDueAugust162021NANA25.0NANANA25.0NANA25.025.0NANANA25.0NANANA25.025.0NANA0.0NANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis,us-gaap:LongtermDebtType us-gaap:CarryingReportedAmountFairValueDisclosure,sigi:OnePointSixtyOnePercentBorrowingFromFederalHomeLoanBankDueJuly212021NANA25.0NANANA25.0NANA25.025.0NANANA25.0NANANA25.025.0NANA0.0NANANANANANANANANANANANANANANANANANANANANANANA
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis,us-gaap:LongtermDebtType us-gaap:CarryingReportedAmountFairValueDisclosure,sigi:SevenPointTwentyFivePercentSeniorNotesNANA49.914NANANA49.91NANA49.90749.907NANANA49.904NANANA49.90149.949.949.89949.89849.89849.89749.89649.89649.89649.89549.91749.91649.915NANA49.912NANANANANANANANANANANA
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis,us-gaap:LongtermDebtType us-gaap:CarryingReportedAmountFairValueDisclosure,sigi:SixPointSeventyPercentSeniorNotesNANA99.499NANANA99.48NANA99.46799.462NANANA99.446NANANA99.4399.42699.42299.41999.41599.41199.40899.40599.40199.39899.39599.50399.49899.492NANA99.475NANANANANANANANANANANA
 us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis,us-gaap:LongtermDebtType us-gaap:CarryingReportedAmountFairValueDisclosure,sigi:ThreePointZeroThreePercentBorrowingFromFederalHomeLoanBankDueDecember162026NANA60.0NANANA60.0NANA60.060.0NANANA60.0NANANA60.0NANANA0.0NANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LongTermDebtAndCapitalLeaseObligations ██▅▁▁▁▂550.881550.904550.743550.566550.588550.577550.597NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:DeferredIncomeTaxLiabilitiesNet ▃▁█▆▄10.8812.31127.09620.413.065NA0.0NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo NANA6.788NANA4.7986.168NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree NANA5.411NANA3.4344.59NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour NANA4.69NANA2.923.329NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive NANA3.572NANA8.6382.92NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive NANA16.234NANANA8.638NANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:StockholdersEquity █▇▇▆▆▅▅▅▅▄▄▄▄▃▄▄▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁2891.3672744.0452738.8892393.6132298.6752096.4562194.9362137.3762059.5441925.2221791.8021738.521698.1551659.7961712.9571699.3521652.5561592.5791531.371574.9041552.7371475.9651398.0411359.0221310.3131315.9381275.5861266.9251238.0751185.5311153.9281124.2091099.0451136.3451090.5921124.3781085.0461082.9181109.2281086.5551101.0341083.6531071.1091092.3161049.5041010.162
us-gaap:CommonStockValue ██████▇▇▇▇▇▇▇▆▆▆▆▆▆▅▅▅▅▅▅▅▄▄▄▄▃▃▃▃▃▂▂▂▂▂▂▁▁208.742208.576208.066207.923207.875207.665206.968206.843206.665206.451205.697205.573205.46205.28204.569204.361204.302204.057203.241203.011202.903202.518201.723201.348201.172200.861199.896199.507199.395199.073198.24197.914197.821197.416196.388196.028195.921195.62194.494194.089193.976193.678192.725NANANA
us-gaap:AdditionalPaidInCapitalCommonStock ██▇▇▇▇▇▇▆▆▆▆▆▅▅▅▅▅▄▄▄▄▄▄▃▃▃▃▃▃▂▂▂▂▂▂▂▂▁▁▁▁▁454.459446.41438.985438.874435.019427.328418.521412.347407.382398.881390.315385.451381.641375.155367.717362.737359.982354.239347.295342.846340.109333.965326.656320.987317.295312.93305.385300.425298.352294.365288.182284.067282.014276.717270.654267.527265.729262.336257.37253.939252.189248.575244.613NANANA
us-gaap:RetainedEarningsAccumulatedDeficit █▇▇▆▆▆▆▆▅▅▅▅▄▄▄▄▄▄▃▃▃▃▃▃▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁2467.5962363.1892271.5372159.5972103.6292083.342080.5292012.4991968.3741908.1191858.4141824.6071779.9281731.8321698.6131679.0411641.821609.8621568.8811538.9281509.2421474.4351446.1921409.5361370.6811345.0351313.441280.1481234.4621212.5771202.0151184.0841158.8611139.1111125.1541131.1151120.1431127.1421167.2191158.3081185.6591190.5281176.155NANANA
us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax ▇▆█▇▆▃▅▅▅▃▁▁▁▂▄▄▄▃▃▄▅▄▃▃▃▄▄▄▅▄▄▃▄▅▄▅▄▄▄▄▄▃▃169.371134.6220.186187.09151.966-22.11781.7598.42668.5063.024-77.956-92.576-84.517-68.24320.1731.31524.4972.09-15.9562.20972.00735.997-9.425-6.039-12.32923.61519.78849.12568.01241.52924.85117.08319.27881.92154.0485.01158.50452.98442.29432.16421.1442.7767.024NANANA
us-gaap:TreasuryStockValue ██▇▇▇▇▆▆▆▆▅▅▅▅▄▄▄▄▄▄▄▄▃▃▃▃▃▃▃▂▂▂▂▂▂▂▂▂▁▁▁▁▁608.801608.73599.885599.871599.814599.76592.832592.739591.383591.253584.668584.535584.357584.228578.112578.102578.045577.669572.097572.09571.524570.95567.105566.81566.506566.503562.923562.28562.146562.013559.36558.939558.929558.82555.644555.303555.251555.164552.149551.945551.934551.904549.408NANANA
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities ▇▅▇█▇▁▇▆▅▁▇162.196130.256173.162183.498158.06839.317161.296151.059118.50146.639162.459NANANANANANANANANANANANANANANANANANANANANA69.75828.1458.945115.59516.30435.855-3.60366.76331.80727.9955.90145.07325.11633.095
us-gaap:NetCashProvidedByUsedInInvestingActivities ▆▇▅█▇▁▆▆▇▆▆-147.754-110.934-190.173-75.474-106.699-315.828-152.634-135.967-112.293-142.729-148.332NANANANANANANANANANANANANANANANANANANANANA-65.56-99.112-54.363-109.015-11.067-28.267-36.461-60.37-26.811-19.865-50.909-39.507-7.584-25.527
us-gaap:NetCashProvidedByUsedInFinancingActivities ▃▂▃▁▂█▃▃▃▄▃-14.105-25.63716.347-97.766-60.338283.142-10.85-12.572-9.07989.685-10.04NANANANANANANANANANANANANANANANANANANANANA-4.3471.058-4.687-6.406-5.357-8.08940.539-6.291-5.307-8.274-4.769-5.735-17.084-8.236
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInOperatingActivities ▇▅▇█▇▁▇▆▅▁▇162.196130.256173.162183.498158.06839.317161.296151.059118.50146.639162.459NANANANANANANANANANANANANANANANANANANANANA69.75828.1458.945115.59516.30435.855-3.60366.76331.80727.9955.90145.07325.11633.095
us-gaap:NetIncomeLoss █▇█▅▄▃▆▅▅▅▄▅▅▃▃▄▄▄▄▄▄▄▄▄▄▄▄▄▃▃▃▄▃▃▂▃▂▃▃▁▂▃▃▃▃▂121.883109.27127.06169.87534.18315.23681.85956.1572.26661.34845.7655.43558.81918.92530.24246.71841.42650.4439.3638.50243.60137.03245.38946.99633.76839.70841.3553.16229.34117.97425.33532.65327.12221.3081.30818.2740.28818.09316.133-20.1422.32521.54923.77517.19718.7665.803
us-gaap:ShareBasedCompensation ▆▇▄▄▅█▄▅▆█▄▄▅▇▃▃▄▆▃▃▄▅▃▃▄▅▃▃▃▅▃▃▄▅▂▂▃▅▂▂▂▆▇▂▁▇4.4346.4932.2922.7374.167.0383.224.2034.9776.6772.3572.5143.8165.821.951.7673.0995.2731.4991.7472.8264.3771.3471.5772.3683.6811.2811.3191.9264.1761.2021.2392.4973.6920.6761.1031.8313.3291.0391.0970.6614.6255.481.113-0.4076.169
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInInvestingActivities ▆▇▅█▇▁▆▆▇▆▆-147.754-110.934-190.173-75.474-106.699-315.828-152.634-135.967-112.293-142.729-148.332NANANANANANANANANANANANANANANANANANANANANA-65.56-99.112-54.363-109.015-11.067-28.267-36.461-60.37-26.811-19.865-50.909-39.507-7.584-25.527
us-gaap:PaymentsToAcquirePropertyPlantAndEquipment ▂▂▁▂▁▇▄▆█▆▂▁4.934.5614.2065.2244.2188.4166.5627.4399.037.9554.964.417NANANANANANANANANANANANANANANANANANANANANANANANANANANANA1.4771.366NANA1.7040.866
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
us-gaap:NetCashProvidedByUsedInFinancingActivities ▃▂▃▁▂█▃▃▃▄▃-14.105-25.63716.347-97.766-60.338283.142-10.85-12.572-9.07989.685-10.04NANANANANANANANANANANANANANANANANANANANANA-4.3471.058-4.687-6.406-5.357-8.08940.539-6.291-5.307-8.274-4.769-5.735-17.084-8.236
us-gaap:PaymentsOfDividendsCommonStock ███▇▇▇▇▅▅▅▅▄▄▄▄▃▃▃▃▃▃▃▂▂▂▂▂▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁▁14.58614.56914.51413.34113.31813.31313.23511.511.47811.46211.40310.25710.23410.20310.138.9938.9678.9558.8738.3168.2998.278.2047.6377.627.5917.5296.9856.9666.9486.8846.8646.8446.8246.7566.7466.7296.7136.656.6386.626.6056.546.5176.5076.492
us-gaap:PaymentsForRepurchaseOfCommonStock ▁█▁▁▁▆▁▂▁▆▁▁▁▆▁▁▁▅▁▁▁▄▁▁▁▄▂▁▁▃▁▁▁▄▁▁▁▃▁▁▁▃▁▁▁▂0.0718.8450.0140.0570.0546.9280.0931.3560.136.5850.1330.1780.1296.1160.010.0570.3765.5720.0070.5660.5743.8450.2950.3040.0033.580.6430.1340.1332.6530.4210.010.1093.1760.3410.0520.0873.0150.2040.0110.032.4960.1580.010.0051.513
  2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31

Common Stock Value

us-gaap:CommonStockValue

us-gaap:CommonStockValue


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value208208208207207207206206206206205205205205204204204204203203202202201201201200199199199199198197197197196196195195194194193193192191
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.12.12.12.22.22.32.42.42.42.52.62.62.72.72.72.62.72.82.82.82.82.92.92.93.03.03.03.03.13.13.23.23.23.12.93.33.43.53.43.43.63.73.73.7

us-gaap:CommonStockValue us-gaap:ConsolidatedEntities

srt:ParentCompany


Common
Period End2020-12-312019-12-312018-12-312017-12-31
Value208206205204
Percentage of CommonStockValue100.0100.0100.0100.0
Percentage of Assets2.12.42.62.7
Percentage of Assets srt:ParentCompany6.47.69.29.5

Common Stock Shares Outstanding

us-gaap:CommonStockSharesOutstanding

us-gaap:CommonStockSharesOutstanding


Common
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312016-12-31
Value5959595959595959585858585857
Percentage of CommonStockSharesOutstanding100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Basic

us-gaap:EarningsPerShareBasic

us-gaap:EarningsPerShareBasic


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1.991.782.121.170.570.261.380.941.221.040.770.941.00.320.520.80.710.870.680.660.750.640.790.820.590.70.730.940.520.320.450.590.490.380.020.330.010.330.3-0.370.040.40.440.320.350.11
Percentage of EarningsPerShareBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Earnings Per Share Diluted

us-gaap:EarningsPerShareDiluted

us-gaap:EarningsPerShareDiluted


Earnings
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1.981.772.11.160.570.251.360.931.211.020.760.930.990.320.510.790.70.850.670.660.740.630.780.810.580.690.720.930.510.310.440.570.480.380.020.330.010.330.29-0.370.040.390.430.320.350.11
Percentage of EarningsPerShareDiluted100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Benefits Losses And Expenses

us-gaap:BenefitsLossesAndExpenses

us-gaap:BenefitsLossesAndExpenses


Benefits
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value687668639691639648627639617625590597579606565553555532532526506499481474475467446440467483453442432431454416429396380434398375364367364385
Percentage of BenefitsLossesAndExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues81.883.180.189.093.797.686.190.087.389.591.989.988.996.889.289.290.488.791.490.589.090.688.387.891.089.388.685.492.295.193.090.992.393.7101.295.4100.294.595.0110.499.793.192.594.394.198.1

Comprehensive Income Net Of Tax

us-gaap:ComprehensiveIncomeNetOfTax

us-gaap:ComprehensiveIncomeNetOfTax


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value15623160104208-88.6316586137142604742-44.46919536368-38.7992879824253-2.17643123455343330-35.52149-29.663445.8082826-9.1222017-17.421474212
Percentage of ComprehensiveIncomeNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues18.62.920.113.530.5-13.38.912.119.520.49.47.16.5-7.13.08.610.411.4-6.74.914.015.07.79.9-0.48.32.46.711.06.86.86.3-7.610.7-6.610.31.46.96.6-2.35.24.3-4.412.210.93.2

Deferred Policy Acquisition Cost Amortization Expense

us-gaap:DeferredPolicyAcquisitionCostAmortizationExpense

us-gaap:DeferredPolicyAcquisitionCostAmortizationExpense


Deferred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value154149144142136136136136133129126124122121119118116115
Percentage of DeferredPolicyAcquisitionCostAmortizationExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues18.418.518.118.320.120.518.719.218.818.619.718.718.819.318.819.019.019.2

Gain Loss On Investments

us-gaap:GainLossOnInvestments

us-gaap:GainLossOnInvestments


Gain
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value105.119207.72112-44.666-0.873-2.1834.02713-37.935-4.787-1.652-10.549-1.1286.7981.734-1.045
Percentage of GainLossOnInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues1.20.62.51.01.9-6.7-0.1-0.30.61.9-5.9-0.7-0.3-1.7-0.21.10.3-0.2

us-gaap:GainLossOnInvestments us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParent, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Gain
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value-2.2724.997-2.968-2.853-4.924150.00.0
Percentage of GainLossOnInvestments-22.697.6-14.8-37.0-38.9-35.30.00.0
Percentage of Revenues-0.30.6-0.4-0.4-0.72.40.00.0
Percentage of Revenues us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParent us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.0

us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParent, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Gain
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.0580.604-3.75-0.515-1.686110.2272.821-1.3-1.077
Percentage of GainLossOnInvestments0.611.8-18.7-6.7-13.3-25.4-26.0-129.2-32.3-8.0
Percentage of Revenues0.00.1-0.5-0.1-0.21.70.00.4-0.2-0.2
Percentage of Revenues us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParent us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.0

us-gaap:HeldtomaturitySecurities, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Gain
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value-0.0210.0040.00.001-0.034-0.003-0.0090.00.011-0.0070.0010.011
Percentage of GainLossOnInvestments-0.10.10.0-0.03.90.1-0.20.0-0.20.4-0.00.2
Percentage of Revenues-0.00.00.00.0-0.0-0.0-0.00.00.0-0.00.00.0
Percentage of Revenues us-gaap:HeldtomaturitySecurities us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.0

Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value153135159854215101719073526772196867586750556251636546565775392534443628-5.17820-0.6922319-40.828-0.099262922
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues18.216.919.911.06.32.413.910.012.710.58.110.111.13.210.810.89.611.38.69.511.09.411.712.29.010.711.414.67.84.97.09.17.76.3-1.24.6-0.25.55.0-10.4-0.06.57.55.7

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParent, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value-2.2724.997-2.968-2.853-4.924150.00.0
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest-1.53.7-1.9-3.3-11.598.70.00.0
Percentage of Revenues-0.30.6-0.4-0.4-0.72.40.00.0
Percentage of Revenues us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParent us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.0

us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParent, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.0580.604-3.75-0.515-1.686110.2272.821-1.3-1.077
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest0.00.4-2.4-0.6-3.970.80.24.0-1.4-1.5
Percentage of Revenues0.00.1-0.5-0.1-0.21.70.00.4-0.2-0.2
Percentage of Revenues us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParent us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.0

us-gaap:HeldtomaturitySecurities, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value-0.003-0.002-0.017-0.001-0.0310.025-0.025-0.003-0.021-0.009-0.008-0.008-0.012-0.054
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest-0.0-0.0-0.0-0.0-0.10.2-0.0-0.0-0.0-0.0-0.0-0.0-0.1-0.1
Percentage of Revenues-0.0-0.0-0.0-0.0-0.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0
Percentage of Revenues us-gaap:HeldtomaturitySecurities us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:PensionPlansDefinedBenefit


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.6930.6930.7540.7540.7530.7540.6640.6650.6640.6640.5320.5320.5310.5320.580.5070.5080.5071.8141.615
Percentage of IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest0.50.50.50.91.84.70.70.90.70.91.00.80.72.70.90.80.90.83.62.9
Percentage of Revenues0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.30.3
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:PensionPlansDefinedBenefit0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Tax Expense Benefit

us-gaap:IncomeTaxExpenseBenefit

us-gaap:IncomeTaxExpenseBenefit


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value312631158.510.761191517126.37511131.0063720171710161814181812161522107.118.913119.0796.563-6.4862.04-0.985.0983.767-21.336-1.1046.2235.5953.2292.7571.054
Percentage of IncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues3.73.34.02.01.20.12.72.12.51.81.01.82.10.26.03.32.82.91.92.93.32.73.43.52.53.23.14.32.01.41.82.41.91.4-1.40.5-0.21.20.9-5.4-0.31.51.40.80.70.3

us-gaap:IncomeTaxExpenseBenefit us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParent, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value-0.4771.049-2.74-0.599-1.0343.3150.00.0
Percentage of IncomeTaxExpenseBenefit-1.54.0-8.6-3.9-12.2435.60.00.0
Percentage of Revenues-0.10.1-0.3-0.1-0.20.50.00.0
Percentage of Revenues us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParent us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.0

us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParent, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.0120.127-3.045-0.109-0.3542.379-0.2340.592-0.273-0.226
Percentage of IncomeTaxExpenseBenefit0.00.5-9.5-0.7-4.2312.6-1.23.9-1.5-1.8
Percentage of Revenues0.00.0-0.4-0.0-0.10.4-0.00.1-0.0-0.0
Percentage of Revenues us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParent us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.0

us-gaap:HeldtomaturitySecurities, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Income
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value-0.0010.007-0.001-0.0060.005-0.005-0.001-0.004-0.002-0.002-0.002-0.002-0.019
Percentage of IncomeTaxExpenseBenefit-0.00.0-0.0-0.10.7-0.0-0.0-0.0-0.0-0.0-0.0-0.2-0.1
Percentage of Revenues-0.00.0-0.0-0.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0
Percentage of Revenues us-gaap:HeldtomaturitySecurities us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:IncomeTaxExpenseBenefit us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:PensionPlansDefinedBenefit


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.1450.146-1.1070.1580.1580.158-0.9770.140.140.1390.1120.1120.1110.1120.2020.1780.1780.1770.6350.565
Percentage of IncomeTaxExpenseBenefit0.50.6-3.51.01.920.8-5.00.90.81.11.81.00.811.10.50.91.01.05.83.3
Percentage of Revenues0.00.0-0.10.00.00.0-0.10.00.00.00.00.00.00.00.00.00.00.00.10.1
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:PensionPlansDefinedBenefit0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Income Taxes Paid Net

us-gaap:IncomeTaxesPaidNet

us-gaap:IncomeTaxesPaidNet


Income
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value13340.00.01314280.0223.07.0-2.8072312270.010.07.405218.02110.04.54.0181.01.6992.0
Percentage of IncomeTaxesPaidNet100.0100.00.00.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues1.64.40.00.01.92.04.00.03.40.51.1-0.43.61.94.40.01.71.33.71.53.81.90.90.83.60.20.30.4

Interest Expense Debt

us-gaap:InterestExpenseDebt

us-gaap:InterestExpenseDebt


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value7.3667.3597.5297.7817.9287.6017.3797.3977.366116.0696.0736.1256.1526.0826.0856.0816.1065.8315.7145.625.6065.975.4895.495.4795.5425.5585.4255.5615.5675.575.575.8314.7244.7254.7234.74.5844.5594.5594.5574.564.5594.6554.842
Percentage of InterestExpenseDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues0.90.90.91.01.21.11.01.01.01.60.90.90.91.01.01.01.01.01.01.01.01.01.11.01.11.01.11.11.11.11.11.11.21.31.11.11.11.11.11.21.11.11.21.21.21.2

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value121109127693415815672614555581830464150393843374546333941532917253227211.308180.2881816-20.1422.325212317185.803
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues14.513.615.99.05.02.311.27.910.28.87.18.39.03.04.87.56.78.46.86.67.76.78.38.76.57.68.210.35.83.55.26.75.84.60.34.20.14.34.0-5.10.65.36.04.44.81.5

us-gaap:NetIncomeLoss us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParent, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value-1.7953.948-2.344-2.254-3.89120.00.0
Percentage of NetIncomeLoss-1.53.6-1.8-3.2-11.481.90.00.0
Percentage of Revenues-0.20.5-0.3-0.3-0.61.90.00.0
Percentage of Revenues us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParent us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.0

us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParent, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.0460.477-2.963-0.406-1.3328.9480.1792.229-1.027-0.851
Percentage of NetIncomeLoss0.00.4-2.3-0.6-3.958.70.24.0-1.4-1.4
Percentage of Revenues0.00.1-0.4-0.1-0.21.30.00.3-0.1-0.1
Percentage of Revenues us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParent us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.0

us-gaap:HeldtomaturitySecurities, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value-0.002-0.002-0.0140.0-0.0250.02-0.02-0.002-0.017-0.007-0.006-0.006-0.01-0.035
Percentage of NetIncomeLoss-0.0-0.0-0.00.0-0.10.1-0.0-0.0-0.0-0.0-0.0-0.0-0.1-0.1
Percentage of Revenues-0.0-0.0-0.00.0-0.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0
Percentage of Revenues us-gaap:HeldtomaturitySecurities us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-30
Value-1.2034.97-4.726-2.064-4.652220.6842.752-0.52-0.333178.9772.6814.0040.501-4.075-0.9231.2796.143-1.354-0.1722.6933.040.8483.216
Percentage of NetIncomeLoss-1.04.5-3.7-3.0-13.6144.60.84.9-0.7-0.538.116.24.621.21.7-8.7-2.22.515.6-3.5-0.47.36.71.89.5
Percentage of Revenues-0.10.6-0.6-0.3-0.73.30.10.4-0.1-0.02.71.40.40.60.1-0.7-0.20.21.1-0.2-0.00.50.60.20.6
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:PensionPlansDefinedBenefit


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.5480.5470.5950.5960.5950.5960.5250.5250.5240.5250.420.420.420.420.3780.3290.330.331.1791.05
Percentage of NetIncomeLoss0.40.50.50.91.73.90.60.90.70.90.90.80.72.21.20.70.80.73.02.7
Percentage of Revenues0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.20.2
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:PensionPlansDefinedBenefit0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value121109127693415815672614555581830464150393843374546333941532917253227211.308180.2881816-20.1422.325212317185.803
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues14.513.615.99.05.02.311.27.910.28.87.18.39.03.04.87.56.78.46.86.67.76.78.38.76.57.68.210.35.83.55.26.75.84.60.34.20.14.34.0-5.10.65.36.04.44.81.5
Percentage of Revenues us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Net Income Loss Available To Common Stockholders Basic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic

us-gaap:NetIncomeLossAvailableToCommonStockholdersBasic


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value11910612769341581567261
Percentage of NetIncomeLossAvailableToCommonStockholdersBasic100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues14.213.315.99.05.02.311.27.910.28.8

Net Investment Income

us-gaap:NetInvestmentIncome

us-gaap:NetInvestmentIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value83696868345557555850545245434240413735333130303232263234363535323432
Percentage of NetInvestmentIncome100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues10.08.78.68.85.08.47.97.98.37.28.47.97.06.96.76.56.76.26.15.75.55.65.55.96.25.16.46.77.37.07.26.77.37.1

us-gaap:NetInvestmentIncome us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:HeldtomaturitySecurities, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value-0.003-0.0020.004-0.005-0.0310.024-0.0330.00.012-0.009-0.0190.001-0.013-0.065
Percentage of NetInvestmentIncome-0.0-0.00.0-0.0-0.10.0-0.10.00.0-0.0-0.00.0-0.0-0.2
Percentage of Revenues-0.0-0.00.0-0.0-0.00.0-0.00.00.0-0.0-0.00.0-0.0-0.0
Percentage of Revenues us-gaap:HeldtomaturitySecurities us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NetInvestmentIncome us-gaap:InvestmentType

sigi:CommercialMortgageLoans


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value0.6950.5140.3810.2450.1560.0620.00.0
Percentage of NetInvestmentIncome0.80.70.60.40.50.10.00.0
Percentage of Revenues0.10.10.00.00.00.00.00.0
Percentage of Revenues sigi:CommercialMortgageLoans0.00.00.00.00.00.00.00.0

sigi:InvestmentExpenses


Net
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value-4.688-4.208-3.388-3.408-3.5-3.485-3.395-2.759-3.382-2.802-2.746-2.873-3.05-3.079-3.265-2.793-2.638-2.404-2.306-2.198-2.441-2.271-2.258-2.327-2.142-2.244-2.31-2.18-2.144-2.113
Percentage of NetInvestmentIncome-6.8-6.2-9.8-6.1-6.1-6.2-5.8-5.5-6.3-5.3-6.0-6.6-7.2-7.6-7.9-7.5-7.4-7.2-7.4-7.1-8.1-7.1-7.0-8.6-6.7-6.5-6.3-6.1-6.1-6.5
Percentage of Revenues-0.6-0.5-0.5-0.5-0.5-0.5-0.5-0.4-0.5-0.4-0.4-0.5-0.5-0.5-0.5-0.5-0.5-0.4-0.4-0.4-0.4-0.4-0.4-0.4-0.4-0.4-0.5-0.4-0.4-0.4
Percentage of Revenues sigi:InvestmentExpenses0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

srt:PartnershipInterest


Net
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value292018-16.06.35.27.30.67.07.11.91.63.22.7
Percentage of NetInvestmentIncome35.729.027.4-46.511.39.312.51.212.913.54.23.77.56.7
Percentage of Revenues3.62.52.4-2.30.90.71.00.11.11.10.30.30.50.4
Percentage of Revenues srt:PartnershipInterest0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:EquitySecurities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value2.9822.4883.7631.9482.0231.5521.7311.8851.741.641.8882.0791.821.9771.951.6051.4191.4681.4281.5062.2042.232.6152.372.3841.7922.3551.9091.7361.4491.7181.341
Percentage of NetInvestmentIncome3.63.65.52.95.92.83.03.43.03.23.54.04.04.64.64.03.43.94.04.57.17.28.77.47.46.77.35.64.74.14.94.1
Percentage of Revenues0.40.30.50.30.30.20.20.30.20.20.30.30.30.30.30.30.20.20.20.30.40.40.50.40.50.30.50.40.30.30.40.3
Percentage of Revenues us-gaap:EquitySecurities0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:FixedMaturities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value5252515151505250504947454342393837363332313131303030303033313030
Percentage of NetInvestmentIncome62.875.874.975.2148.389.891.390.987.096.987.286.096.197.293.596.190.998.694.497.2101.8102.8103.095.495.1115.096.589.591.987.386.794.2
Percentage of Revenues6.36.66.46.67.57.67.27.17.27.07.36.86.76.76.36.36.16.15.75.65.65.75.75.75.95.96.26.06.76.16.36.3
Percentage of Revenues us-gaap:FixedMaturities0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OtherInvestments


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value32171718-15.8466.3425.3575.2677.4940.666.9317.2112.0941.5633.3782.6595.2311.6032.9891.628-0.611-1.066-1.1091.3371.422-3.540.9033.9063.5535.218
Percentage of NetInvestmentIncome39.225.025.927.4-46.011.39.39.412.81.312.813.84.63.67.96.612.64.38.44.9-2.0-3.5-3.74.24.4-13.22.811.49.714.7
Percentage of Revenues3.92.22.22.4-2.31.00.70.71.10.11.11.10.30.20.50.40.90.30.50.3-0.1-0.2-0.20.20.3-0.70.20.80.71.0
Percentage of Revenues us-gaap:OtherInvestments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ShortTermInvestments


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-30
Value0.0550.085-0.0090.2440.421.1661.441.411.7592.0441.4710.8670.6110.5230.5030.3960.3770.250.1930.1920.1420.1590.040.0240.0230.0250.0180.0150.0140.0190.0150.021
Percentage of NetInvestmentIncome0.10.1-0.00.41.22.12.52.53.04.02.71.71.31.21.21.00.90.70.50.60.50.50.10.10.10.10.10.00.00.10.00.1
Percentage of Revenues0.00.0-0.00.00.10.20.20.20.20.30.20.10.10.10.10.10.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0
Percentage of Revenues us-gaap:ShortTermInvestments0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Operating Costs And Expenses

us-gaap:OperatingCostsAndExpenses

us-gaap:OperatingCostsAndExpenses


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value9.1129.5546.1023.9056.3459.062.5556.3699.566123.3817.453.283119.5866.2898.46411
Percentage of OperatingCostsAndExpenses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues1.11.20.80.50.91.40.40.91.41.80.51.10.51.81.51.01.42.0

Other Comprehensive Income Loss Net Of Tax

us-gaap:OtherComprehensiveIncomeLossNetOfTax

us-gaap:OtherComprehensiveIncomeLossNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value34-85.5863335174-103.867-16.67629658014-8.059-16.274-63.394-11.1456.8182218-78.159-9.7983645-3.3866.29-35.9443.827-29.337-18.88726167.768-2.195-62.64327-30.971265.5210101118-4.248
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues4.1-10.64.14.525.5-15.6-2.34.29.211.62.3-1.2-2.5-10.1-1.81.13.63.0-13.4-1.76.38.2-0.61.2-6.90.7-5.8-3.75.23.31.6-0.5-13.46.1-6.96.11.32.52.52.84.6-1.1

us-gaap:OtherComprehensiveIncomeLossNetOfTax us-gaap:InformationByCategoryOfDebtSecurity

us-gaap:AvailableforsaleSecurities


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value28-81.1362529147-65.297-6.28329648022
Percentage of OtherComprehensiveIncomeLossNetOfTax80.994.876.783.984.962.937.798.399.299.4157.3
Percentage of Revenues3.3-10.13.23.821.7-9.8-0.94.19.211.53.6
Percentage of Revenues us-gaap:AvailableforsaleSecurities0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Investments


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value34-86.1333134173-104.463-6.30329648023
Percentage of OtherComprehensiveIncomeLossNetOfTax98.4100.694.698.399.7100.637.898.299.299.4158.0
Percentage of Revenues4.1-10.73.94.425.4-15.7-0.94.19.211.53.6
Percentage of Revenues us-gaap:Investments0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OtherComprehensiveIncomeLossNetOfTax us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:StatementEquityComponents

us-gaap:HeldtomaturitySecurities, us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value-0.002-0.002-0.0140.0-0.0250.02-0.02-0.002-0.017-0.0070.109
Percentage of OtherComprehensiveIncomeLossNetOfTax-0.00.0-0.00.0-0.0-0.00.1-0.0-0.0-0.00.7
Percentage of Revenues-0.0-0.0-0.00.0-0.00.0-0.0-0.0-0.0-0.00.0
Percentage of Revenues us-gaap:HeldtomaturitySecurities us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value34-85.5863335174-103.867-16.67629658014-8.059-16.274-63.394-11.1456.8182218-78.159-9.7983645-3.3866.29-35.9443.827-29.337-18.88726167.768-2.195-62.64327-30.971265.5210
Percentage of OtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues4.1-10.64.14.525.5-15.6-2.34.29.211.62.3-1.2-2.5-10.1-1.81.13.63.0-13.4-1.76.38.2-0.61.2-6.90.7-5.8-3.75.23.31.6-0.5-13.46.1-6.96.11.32.5
Percentage of Revenues us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedOtherThanTemporaryImpairment


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value6.093-4.9955.9485.04525-39.1860.00.00.00.00.00.00.00.00.0430.0440.0040.00.1380.0-0.0060.00.00.00.00.2320.00.780.3050.00.0
Percentage of OtherComprehensiveIncomeLossNetOfTax17.55.818.014.414.837.7-0.00.00.00.00.0-0.0-0.0-0.0-0.40.60.00.0-0.2-0.0-0.00.0-0.00.0-0.06.1-0.0-4.11.20.00.0
Percentage of Revenues0.7-0.60.70.63.8-5.90.00.00.00.00.00.00.00.00.00.00.00.00.00.0-0.00.00.00.00.00.00.00.20.10.00.0
Percentage of Revenues us-gaap:AccumulatedOtherThanTemporaryImpairment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Other Income

us-gaap:OtherIncome

us-gaap:OtherIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value6.2124.1124.9436.1194.6831.8253.823.1623.0532.321.5422.5383.1792.1792.191.9943.2913.2411.8632.1993.8680.9511.9350.6982.8541.9692.0143.1961.9119.8242.6173.3573.5362.7841.9891.0852.5113.5331.7351.3652.4992.882.9331.952.2472.268
Percentage of OtherIncome100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues0.70.50.60.80.70.30.50.40.40.30.20.40.50.30.30.30.50.50.30.40.70.20.40.10.50.40.40.60.41.90.50.70.80.60.40.20.60.80.40.30.60.70.70.50.60.6

us-gaap:OtherIncome sigi:LineOfBusinessBySegment

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine


Other
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value5.5214.1951.3912.7822.7182.0441.2442.2282.8821.8261.91.712
Percentage of OtherIncome90.289.676.288.089.088.180.787.890.783.886.885.9
Percentage of Revenues0.70.60.20.40.40.30.20.30.40.30.30.3
Percentage of Revenues us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine1.00.80.30.50.50.40.00.50.60.40.00.4

us-gaap:PropertyAndCasualtyPersonalInsuranceProductLine


Other
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0.5980.4880.4340.4750.380.3350.2760.2980.310.2970.3520.290.2820.2750.381
Percentage of OtherIncome9.810.423.812.412.011.011.919.312.29.316.213.214.18.411.8
Percentage of Revenues0.10.10.10.10.10.00.00.00.00.00.10.00.00.00.1
Percentage of Revenues us-gaap:PropertyAndCasualtyPersonalInsuranceProductLine0.80.70.60.00.50.40.40.00.40.40.50.00.40.00.0

us-gaap:OtherIncome us-gaap:StatementBusinessSegments

sigi:StandardCommercialLines


Other
Period End2021-06-302021-03-312020-06-302020-03-31
Value5.7953.7074.1951.391
Percentage of OtherIncome93.390.289.676.2
Percentage of Revenues0.70.50.60.2
Percentage of Revenues sigi:StandardCommercialLines1.00.60.80.3

sigi:StandardPersonalLines


Other
Period End2021-06-302021-03-312020-06-302020-03-31
Value0.4170.4050.4880.434
Percentage of OtherIncome6.79.810.423.8
Percentage of Revenues0.00.10.10.1
Percentage of Revenues sigi:StandardPersonalLines0.60.50.70.6

Preferred Stock Dividends Income Statement Impact

us-gaap:PreferredStockDividendsIncomeStatementImpact

us-gaap:PreferredStockDividendsIncomeStatementImpact


Preferred
Period End2021-06-302021-03-31
Value2300000.02453000.0
Percentage of PreferredStockDividendsIncomeStatementImpact100.0100.0
Percentage of Revenues0.30.3

Realized Investment Gains Losses

us-gaap:RealizedInvestmentGainsLosses

us-gaap:RealizedInvestmentGainsLosses


Realized
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value3.3836.948-27.529-0.315181.9123.34-24.129-2.177-2.7673.519-1.1286.7981.734-1.045-7.6863.6881.765-2.704-2.60.308-3.4218-0.389154.5397.218-1.208135.1543.3555.54-1.0880.1784.358-3.621-2.0452.1465.76-3.8120.057-3.264-0.064
Percentage of RealizedInvestmentGainsLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues0.41.0-4.1-0.02.60.30.5-3.8-0.3-0.40.6-0.21.10.3-0.2-1.30.60.3-0.5-0.50.1-0.73.6-0.13.00.91.4-0.22.81.10.71.2-0.20.01.0-0.9-0.50.51.4-1.00.0-0.8-0.0

Revenues

us-gaap:Revenues

us-gaap:Revenues


Revenues
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value840803798776682664728710708698643664651626633621614600582581568551545540521523503515506509488486468459448436428419400394399403394389387393
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Revenues sigi:LineOfBusinessBySegment

sigi:ExcessAndSurplusOperations


Revenuessigi:
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value605858615858585653525454
Percentage of Revenues7.88.58.98.78.38.39.08.48.28.38.68.7
Percentage of Revenues7.88.58.98.78.38.39.08.48.28.38.68.7
Percentage of Revenues sigi:ExcessAndSurplusOperations100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine


Revenuessigi:
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value563505517517509499491483478467463446
Percentage of Revenues72.674.077.972.971.971.476.472.773.574.573.171.9
Percentage of Revenues72.674.077.972.971.971.476.472.773.574.573.171.9
Percentage of Revenues us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PropertyAndCasualtyPersonalInsuranceProductLine


Revenuessigi:
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value76727677777777777775747472
Percentage of Revenues9.910.611.510.610.910.911.112.111.711.711.911.811.7
Percentage of Revenues9.910.611.510.610.910.911.112.111.711.711.911.811.7
Percentage of Revenues us-gaap:PropertyAndCasualtyPersonalInsuranceProductLine100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Revenues us-gaap:StatementBusinessSegments

sigi:ESLines


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value67615858
Percentage of Revenues8.07.78.58.9
Percentage of Revenues8.07.78.58.9
Percentage of Revenues sigi:ESLines100.0100.0100.0100.0

sigi:StandardCommercialLines


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value605592505517
Percentage of Revenues72.073.774.077.9
Percentage of Revenues72.073.774.077.9
Percentage of Revenues sigi:StandardCommercialLines100.0100.0100.0100.0

sigi:StandardPersonalLines


Revenuesus-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value73747276
Percentage of Revenues8.89.210.611.5
Percentage of Revenues8.89.210.611.5
Percentage of Revenues sigi:StandardPersonalLines100.0100.0100.0100.0

Assets

us-gaap:Assets

us-gaap:Assets


Assets
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value101679848968795149305897587978719857582827952798677057659768678127528740473557363718970226904689867846701658165776490637062706266611263446794587956875629573657485369527552315114
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Assets us-gaap:ConsolidatedEntities

srt:ParentCompany


Assetsus-gaap:
Period End2020-12-312019-12-312018-12-312017-12-31
Value3259271622282164
Percentage of Assets33.630.928.028.2
Percentage of Assets33.630.928.028.2
Percentage of Assets srt:ParentCompany100.0100.0100.0100.0

Liabilities

us-gaap:Liabilities

us-gaap:Liabilities


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value72767104694971217007687866026582651663576160624860076000597361125875581158245788563655465506553954745385530553105252518451165142501352075703475546024546462746624268419141604112
Percentage of Liabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets71.672.171.774.875.376.675.075.576.076.877.578.278.078.377.778.278.078.579.278.678.479.079.880.380.780.480.680.780.981.481.682.182.082.183.980.980.980.880.781.179.579.579.580.4

us-gaap:Liabilities us-gaap:ConsolidatedEntities

srt:ParentCompany


Liabilitiesus-gaap:
Period End2020-12-312019-12-312018-12-312017-12-31
Value520522437451
Percentage of Liabilities7.57.97.17.6
Percentage of Assets5.45.95.55.9
Percentage of Assets srt:ParentCompany16.019.219.620.8

Liabilities And Stockholders Equity

us-gaap:LiabilitiesAndStockholdersEquity

us-gaap:LiabilitiesAndStockholdersEquity


Liabilities
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value101679848968795149305897587978719857582827952798677057659768678127528740473557363718970226904689867846701658165776490637062706266611263446794587956875629573657485369527552315114
Percentage of LiabilitiesAndStockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LiabilitiesAndStockholdersEquity us-gaap:ConsolidatedEntities

srt:ParentCompany


Liabilities
Period End2020-12-312019-12-312018-12-312017-12-31
Value3259271622282164
Percentage of LiabilitiesAndStockholdersEquity33.630.928.028.2
Percentage of Assets33.630.928.028.2
Percentage of Assets srt:ParentCompany100.0100.0100.0100.0

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value28912744273823932298209621942137205919251791173816981659171216991652159215311574155214751398135913101315127512661238118511531124109911361090112410851082110910861101108310711092104910101002890
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets28.427.928.325.224.723.425.024.524.023.222.521.822.021.722.321.822.021.520.821.421.621.020.219.719.319.619.419.319.118.618.417.918.017.916.119.119.119.219.318.920.520.520.50.00.00.019.60.0

us-gaap:StockholdersEquity us-gaap:ConsolidatedEntities

srt:ParentCompany


Stockholders
Period End2020-12-312019-12-312018-12-312017-12-31
Value2738219417911712
Percentage of StockholdersEquity100.0100.0100.0100.0
Percentage of Assets28.325.022.522.3
Percentage of Assets srt:ParentCompany84.080.880.479.2

us-gaap:StockholdersEquity us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:StatementEquityComponents

srt:CumulativeEffectPeriodOfAdoptionAdjustment, us-gaap:RetainedEarnings


Stockholders
Period End2021-03-312020-12-312020-06-302020-03-312019-12-312019-06-302018-12-312017-12-31
Value23632271210320832081196818581723
Percentage of StockholdersEquity86.182.991.599.494.995.6103.7100.6
Percentage of Assets24.023.422.623.223.723.023.422.4
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.0

us-gaap:StockholdersEquity us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value169134220187151-22.1178198683.024-77.956-92.576-84.517-68.2432031242.09-15.95627235-9.425-6.039-12.329231949684124171981548558524232212.7767.0244817-5.773-12.46-100.66686
Percentage of StockholdersEquity5.94.98.07.86.6-1.13.74.63.30.2-4.4-5.3-5.0-4.11.21.81.50.1-1.04.04.62.4-0.7-0.4-0.91.81.63.95.53.52.21.51.87.25.07.65.44.93.83.01.90.30.74.41.7-0.6-1.2-11.30.0
Percentage of Assets1.71.42.32.01.6-0.20.91.10.80.0-1.0-1.2-1.1-0.90.30.40.30.0-0.20.81.00.5-0.1-0.1-0.20.40.30.71.00.70.40.30.31.30.81.41.00.90.70.60.40.10.10.00.00.0-0.20.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value454446438438435427418412407398390385381375367362359354347342340333326320317312305300298294288284282276270267265262257253252248244241239235231217192
Percentage of StockholdersEquity15.716.316.018.318.920.419.119.319.820.721.822.222.522.621.521.321.822.222.721.821.922.623.423.624.223.823.923.724.124.825.025.325.724.424.823.824.524.223.223.422.922.922.822.122.823.323.124.40.0
Percentage of Assets4.54.54.54.64.74.84.84.74.84.84.94.85.04.94.84.64.84.84.74.74.74.84.74.74.74.74.64.64.64.64.64.54.64.44.04.54.74.74.54.44.74.74.70.00.00.04.50.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value208208208207207207206206206206205205205205204204204204203203202202201201201200199199199199198197197197196196195195194194193193192192192191191190189
Percentage of StockholdersEquity7.27.67.68.79.09.99.49.710.010.711.511.812.112.411.912.012.412.813.312.913.113.714.414.815.415.315.715.716.116.817.217.618.017.418.017.418.118.117.517.917.617.918.017.618.319.019.121.40.0
Percentage of Assets2.12.12.12.22.22.32.42.42.42.52.62.62.72.72.72.62.72.82.82.82.82.92.92.93.03.03.03.03.13.13.23.23.23.12.93.33.43.53.43.43.63.73.70.00.00.03.70.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value2467236322712159210320832080201219681908185818241779173116981679164116091568153815091474144614091370134513131280123412121202118411581139112511311120112711671158118511901176115911491137113811281105
Percentage of StockholdersEquity85.386.182.990.291.599.494.894.295.699.1103.7105.0104.8104.399.298.899.4101.1102.497.797.299.9103.4103.7104.6102.2103.0101.099.7102.3104.2105.3105.4100.2103.2100.6103.2104.1105.2106.6107.7109.9109.8106.2109.5112.6113.6126.70.0
Percentage of Assets24.324.023.422.722.623.223.723.123.023.023.422.823.122.622.121.521.821.721.320.921.021.020.920.420.220.120.019.519.019.019.218.919.018.016.619.219.720.020.320.122.122.622.50.00.00.022.30.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value-608.801-608.73-599.885-599.871-599.814-599.76-592.832-592.739-591.383-591.253-584.668-584.535-584.357-584.228-578.112-578.102-578.045-577.669-572.097-572.09-571.524-570.95-567.105-566.81-566.506-566.503-562.923-562.28-562.146-562.013-559.36-558.939-558.929-558.82-555.644-555.303-555.251-555.164-552.149-551.945-551.934-551.904-549.408-549.25-549.24-549.235-547.722-544.712-497.879
Percentage of StockholdersEquity-21.1-22.2-21.9-25.1-26.1-28.6-27.0-27.7-28.7-30.7-32.6-33.6-34.4-35.2-33.7-34.0-35.0-36.3-37.4-36.3-36.8-38.7-40.6-41.7-43.2-43.0-44.1-44.4-45.4-47.4-48.5-49.7-50.9-49.2-50.9-49.4-51.2-51.3-49.8-50.8-50.1-50.9-51.3-50.3-52.3-54.4-54.6-61.20.0
Percentage of Assets-6.0-6.2-6.2-6.3-6.4-6.7-6.7-6.8-6.9-7.1-7.4-7.3-7.6-7.6-7.5-7.4-7.7-7.8-7.8-7.8-7.9-8.1-8.2-8.2-8.4-8.5-8.6-8.5-8.7-8.8-8.9-8.9-9.1-8.8-8.2-9.4-9.8-9.9-9.6-9.6-10.3-10.5-10.50.00.00.0-10.70.00.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Cash

us-gaap:Cash

us-gaap:Cash


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value0.450.4880.3940.7850.6669.4290.30.5160.5040.5160.5050.4464.8760.6740.5340.6948.6280.4830.4581.4931.530.6830.898150.36814232.5011.5470.2450.1930.1770.1540.2960.210.3150.1410.2610.7620.2870.1850.4960.6450.4220.5910.1430.8113.6061.965
Percentage of Cash100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.10.00.00.00.00.00.00.10.00.00.00.10.00.00.00.00.00.00.20.00.20.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Cash us-gaap:ConsolidatedEntities

srt:ParentCompany


Cashus-gaap:
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-31
Value0.3940.30.5050.5340.4580.898
Percentage of Cash100.0100.0100.0100.0100.0100.0
Percentage of Assets0.00.00.00.00.00.0
Percentage of Assets srt:ParentCompany0.00.00.00.00.00.0

Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312015-12-31
Value9.2538.91615155.637147.975107.6431016121616441816143712
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.10.10.20.20.10.20.10.10.10.10.20.20.20.20.60.20.20.20.50.2

Accumulated Depreciation Depletion And Amortization Property Plant And Equipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment

us-gaap:AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value251245240240237231227223219216211227220217213211206202198198193192188184180175172188184181179176174171169167164162160158156153151141
Percentage of AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.52.52.52.52.52.62.62.62.62.62.72.92.92.82.82.72.72.72.72.72.72.72.72.72.72.62.62.92.82.92.92.82.92.72.52.82.92.92.82.82.92.92.92.8

Property Plant And Equipment Net

us-gaap:PropertyPlantAndEquipmentNet

us-gaap:PropertyPlantAndEquipmentNet


Property
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value7576777878807776736865646262636666686969686565656261595553535050484847454543433939404146
Percentage of PropertyPlantAndEquipmentNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.70.80.80.80.80.90.90.90.90.80.80.80.80.80.80.80.90.90.90.91.00.91.01.00.90.90.90.80.80.80.80.80.80.80.70.80.80.80.80.70.70.80.80.9

Operating Lease Right Of Use Asset

us-gaap:OperatingLeaseRightOfUseAsset

us-gaap:OperatingLeaseRightOfUseAsset


Operating
Period End2020-12-312020-03-312019-12-312019-09-302019-06-302019-03-312019-01-01
Value40282628292420
Percentage of OperatingLeaseRightOfUseAsset100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets0.40.30.30.30.30.30.0

Equity Securities Fv Ni

us-gaap:EquitySecuritiesFvNi

us-gaap:EquitySecuritiesFvNi


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value348324310151134997279157163147
Percentage of EquitySecuritiesFvNi100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.43.33.21.61.41.10.80.91.82.01.9

us-gaap:EquitySecuritiesFvNi us-gaap:ConsolidatedEntities

srt:ParentCompany


Equity
Period End2020-12-31
Value159
Percentage of EquitySecuritiesFvNi51.4
Percentage of Assets1.6
Percentage of Assets srt:ParentCompany4.9

us-gaap:EquitySecuritiesFvNi us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-31
Value26327026310593603546111110
Percentage of EquitySecuritiesFvNi75.583.584.969.369.960.848.258.171.174.7
Percentage of Assets2.62.72.71.11.00.70.40.51.31.4
Percentage of Assets us-gaap:FairValueInputsLevel1 us-gaap:FairValueMeasurementsRecurring0.00.00.00.00.00.00.00.00.00.0

us-gaap:EquitySecuritiesFvNi us-gaap:FairValueByFairValueHierarchyLevel, us-gaap:FairValueByMeasurementFrequency, us-gaap:InvestmentType

us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring, us-gaap:CommonStock


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-31
Value26026926110392593242108107
Percentage of EquitySecuritiesFvNi74.983.084.468.268.759.244.154.369.172.7
Percentage of Assets2.62.72.71.11.00.70.40.51.31.4
Percentage of Assets us-gaap:FairValueInputsLevel1 us-gaap:FairValueMeasurementsRecurring us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.0

us-gaap:FairValueInputsLevel1, us-gaap:FairValueMeasurementsRecurring, us-gaap:NonredeemablePreferredStock


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-31
Value2.111.6981.7351.6711.6171.5793.0373.0343.0142.912
Percentage of EquitySecuritiesFvNi0.60.50.61.11.21.64.23.81.92.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:FairValueInputsLevel1 us-gaap:FairValueMeasurementsRecurring us-gaap:NonredeemablePreferredStock0.00.00.00.00.00.00.00.00.00.0

us-gaap:EquitySecuritiesFvNi us-gaap:FairValueByMeasurementFrequency

us-gaap:FairValueMeasurementsRecurring


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-31
Value348324310151134997279157147
Percentage of EquitySecuritiesFvNi100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets3.43.33.21.61.41.10.80.91.81.9
Percentage of Assets us-gaap:FairValueMeasurementsRecurring0.00.00.00.00.00.00.00.00.00.0

us-gaap:EquitySecuritiesFvNi us-gaap:FairValueByMeasurementFrequency, us-gaap:InvestmentType

us-gaap:FairValueMeasurementsRecurring, us-gaap:CommonStock


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-31
Value346322308150132986976154144
Percentage of EquitySecuritiesFvNi99.499.599.498.998.898.495.896.298.198.0
Percentage of Assets3.43.33.21.61.41.10.80.91.81.8
Percentage of Assets us-gaap:FairValueMeasurementsRecurring us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.0

us-gaap:FairValueMeasurementsRecurring, us-gaap:NonredeemablePreferredStock


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302018-12-31
Value2.111.6981.7351.6711.6171.5793.0373.0343.0142.912
Percentage of EquitySecuritiesFvNi0.60.50.61.11.21.64.23.81.92.0
Percentage of Assets0.00.00.00.00.00.00.00.00.00.0
Percentage of Assets us-gaap:FairValueMeasurementsRecurring us-gaap:NonredeemablePreferredStock0.00.00.00.00.00.00.00.00.00.0

Other Assets

us-gaap:OtherAssets

us-gaap:OtherAssets


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value18820315314713015012813511510376918886122988892113948489788677787377747075718712457555252525145466168
Percentage of OtherAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.92.11.61.61.41.71.51.61.31.21.01.11.11.11.61.31.21.31.51.31.21.31.11.31.11.21.11.21.11.11.21.11.42.00.81.00.90.90.90.90.80.91.21.3

us-gaap:OtherAssets us-gaap:ConsolidatedEntities

srt:ParentCompany


Other
Period End2020-12-312019-12-312018-12-312017-12-31
Value1.9591.6921.1860.871
Percentage of OtherAssets1.31.31.50.7
Percentage of Assets0.00.00.00.0
Percentage of Assets srt:ParentCompany0.10.10.10.0

Accrued Income Taxes Current

us-gaap:AccruedIncomeTaxesCurrent

us-gaap:AccruedIncomeTaxesCurrent


Accrued
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312015-12-312014-12-312013-12-31
Value142.9871.3020.00.07.4423.9210.0
Percentage of AccruedIncomeTaxesCurrent100.0100.0100.00.00.0100.0100.00.0
Percentage of Assets0.10.00.00.00.00.10.10.0

Long Term Debt

us-gaap:LongTermDebt

us-gaap:LongTermDebt


Long
Period End2020-12-312019-12-312019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value550550550439439439439439439438438438378328328388394394394379392392392392392392392307307307307307262262262262274
Percentage of LongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets5.76.36.65.55.55.75.75.75.65.85.96.05.14.64.75.65.75.85.95.86.06.06.26.36.36.46.24.55.25.45.55.44.64.95.05.05.4

us-gaap:LongTermDebt us-gaap:ConsolidatedEntities

srt:ParentCompany


Long
Period End2020-12-312019-12-312018-12-312017-12-31
Value440439329329
Percentage of LongTermDebt79.979.975.074.9
Percentage of Assets4.55.04.14.3
Percentage of Assets srt:ParentCompany13.516.214.815.2

us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis

us-gaap:CarryingReportedAmountFairValueDisclosure


Long
Period End2020-12-312019-12-312018-12-312017-12-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value550550439439438378328328388394394394379392392392392392307
Percentage of LongTermDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets5.76.35.55.76.05.14.64.75.65.75.85.95.86.06.06.26.36.34.5
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:LongTermDebt us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:FivePointThreeHundredSeventyFive


Long
Period End2020-12-312019-12-312019-03-312018-12-31
Value2942942940.0
Percentage of LongTermDebt53.453.453.50.0
Percentage of Assets3.03.33.60.0
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:FivePointThreeHundredSeventyFive0.00.00.00.0

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:LongTermDebtExcludingIssuanceCosts


Long
Period End2020-12-312019-12-312019-03-312018-12-312017-12-312016-12-312016-09-302016-06-302016-03-312015-12-312014-12-31
Value553553553444444444384334334394379
Percentage of LongTermDebt100.5100.5100.6101.1101.2101.3101.5101.8101.8101.6100.0
Percentage of Assets5.76.36.75.65.86.05.24.74.85.75.8
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:LongTermDebtExcludingIssuanceCosts0.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:OnePointFiftySixPercentBorrowingFromFederalHomeLoanBankDueAugust162021


Long
Period End2020-12-312019-12-312019-03-312018-12-312017-12-312016-12-312016-09-302015-12-31
Value252525252525250.0
Percentage of LongTermDebt4.54.54.55.75.75.76.60.0
Percentage of Assets0.30.30.30.30.30.30.30.0
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:OnePointFiftySixPercentBorrowingFromFederalHomeLoanBankDueAugust1620210.00.00.00.00.00.00.00.0

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:OnePointSixtyOnePercentBorrowingFromFederalHomeLoanBankDueJuly212021


Long
Period End2020-12-312019-12-312019-03-312018-12-312017-12-312016-12-312016-09-302015-12-31
Value252525252525250.0
Percentage of LongTermDebt4.54.54.55.75.75.76.60.0
Percentage of Assets0.30.30.30.30.30.30.30.0
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:OnePointSixtyOnePercentBorrowingFromFederalHomeLoanBankDueJuly2120210.00.00.00.00.00.00.00.0

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:SevenPointTwentyFivePercentSeniorNotes


Long
Period End2020-12-312019-12-312019-03-312018-12-312017-12-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value4949494949494949494949494949494949494949
Percentage of LongTermDebt9.19.19.111.411.411.413.215.215.212.912.712.712.713.212.712.712.712.712.716.2
Percentage of Assets0.50.60.60.60.60.70.70.70.70.70.70.70.70.80.80.80.80.80.80.7
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:SevenPointTwentyFivePercentSeniorNotes0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:SixPointSeventyPercentSeniorNotes


Long
Period End2020-12-312019-12-312019-03-312018-12-312017-12-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-31
Value9999999999999999999999999999999999999999
Percentage of LongTermDebt18.118.118.122.622.622.726.330.330.325.625.225.225.226.225.325.325.425.425.432.4
Percentage of Assets1.01.11.21.31.31.41.41.41.41.41.41.51.51.51.51.51.61.61.61.5
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:SixPointSeventyPercentSeniorNotes0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:ThreePointZeroThreePercentBorrowingFromFederalHomeLoanBankDueDecember162026


Long
Period End2020-12-312019-12-312019-03-312018-12-312017-12-312016-12-312015-12-31
Value6060606060600.0
Percentage of LongTermDebt10.910.910.913.713.713.70.0
Percentage of Assets0.60.70.70.80.80.80.0
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:ThreePointZeroThreePercentBorrowingFromFederalHomeLoanBankDueDecember1620260.00.00.00.00.00.00.0

Long Term Debt And Capital Lease Obligations

us-gaap:LongTermDebtAndCapitalLeaseObligations

us-gaap:LongTermDebtAndCapitalLeaseObligations


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value550550550550550550550
Percentage of LongTermDebtAndCapitalLeaseObligations100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets5.45.65.75.85.96.16.3

us-gaap:LongTermDebtAndCapitalLeaseObligations us-gaap:FairValueByMeasurementBasis, us-gaap:LongtermDebtType

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:FivePointThreeHundredSeventyFive


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value294294294294294294294
Percentage of LongTermDebtAndCapitalLeaseObligations53.453.453.453.453.453.453.4
Percentage of Assets2.93.03.03.13.23.33.3
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:FivePointThreeHundredSeventyFive0.00.00.00.00.00.00.0

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:LongTermDebtExcludingIssuanceCosts


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value553553553553553553553
Percentage of LongTermDebtAndCapitalLeaseObligations100.5100.5100.5100.6100.5100.5100.5
Percentage of Assets5.45.65.75.85.96.26.3
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:LongTermDebtExcludingIssuanceCosts0.00.00.00.00.00.00.0

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:SevenPointTwentyFivePercentSeniorNotes


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value49494949494949
Percentage of LongTermDebtAndCapitalLeaseObligations9.19.19.19.19.19.19.1
Percentage of Assets0.50.50.50.50.50.60.6
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:SevenPointTwentyFivePercentSeniorNotes0.00.00.00.00.00.00.0

us-gaap:CarryingReportedAmountFairValueDisclosure, sigi:SixPointSeventyPercentSeniorNotes


Long
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-31
Value99999999999999
Percentage of LongTermDebtAndCapitalLeaseObligations18.118.118.118.118.118.118.1
Percentage of Assets1.01.01.01.01.11.11.1
Percentage of Assets us-gaap:CarryingReportedAmountFairValueDisclosure sigi:SixPointSeventyPercentSeniorNotes0.00.00.00.00.00.00.0

Deferred Income Tax Liabilities Net

us-gaap:DeferredIncomeTaxLiabilitiesNet

us-gaap:DeferredIncomeTaxLiabilitiesNet


Deferred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302019-12-31
Value102.3112720130.0
Percentage of DeferredIncomeTaxLiabilitiesNet100.0100.0100.0100.0100.00.0
Percentage of Assets0.10.00.30.20.10.0

us-gaap:DeferredIncomeTaxLiabilitiesNet us-gaap:BalanceSheetLocation

sigi:DeferredTaxLiability


Deferred
Period End2020-12-31
Value27
Percentage of DeferredIncomeTaxLiabilitiesNet100.0
Percentage of Assets0.3
Percentage of Assets sigi:DeferredTaxLiability0.0

Lessee Operating Lease Liability Payments Due Year Two

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearTwo


Lessee
Period End2020-12-312020-03-312019-12-31
Value6788000.04798000.06168000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearTwo100.0100.0100.0
Percentage of Assets0.10.10.1

Lessee Operating Lease Liability Payments Due Year Three

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearThree


Lessee
Period End2020-12-312020-03-312019-12-31
Value5411000.03434000.04590000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearThree100.0100.0100.0
Percentage of Assets0.10.00.1

Lessee Operating Lease Liability Payments Due Year Four

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFour


Lessee
Period End2020-12-312020-03-312019-12-31
Value4690000.02920000.03329000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFour100.0100.0100.0
Percentage of Assets0.00.00.0

Lessee Operating Lease Liability Payments Due Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueYearFive


Lessee
Period End2020-12-312020-03-312019-12-31
Value3572000.08638000.02920000.0
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueYearFive100.0100.0100.0
Percentage of Assets0.00.10.0

Lessee Operating Lease Liability Payments Due After Year Five

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive


Lessee
Period End2020-12-312019-12-31
Value168.638
Percentage of LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive100.0100.0
Percentage of Assets0.20.1

Operating Lease Liability

us-gaap:OperatingLeaseLiability us-gaap:BalanceSheetLocation

us-gaap:OperatingLeaseLiability

us-gaap:OtherLiabilities


Operating
Period End2020-12-312019-12-31
Value4127
Percentage of OperatingLeaseLiability100.0100.0
Percentage of Assets0.40.3
Percentage of Assets us-gaap:OtherLiabilities0.00.0

Lessee Operating Lease Liability Payments Due

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue

us-gaap:LesseeOperatingLeaseLiabilityPaymentsDue


Lessee
Period End2020-12-312020-03-312019-12-31
Value453233
Percentage of LesseeOperatingLeaseLiabilityPaymentsDue100.0100.0100.0
Percentage of Assets0.50.40.4

Lessee Operating Lease Liability Undiscounted Excess Amount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount

us-gaap:LesseeOperatingLeaseLiabilityUndiscountedExcessAmount


Lessee
Period End2020-12-312020-03-312019-12-31
Value3393000.03089000.02995000.0
Percentage of LesseeOperatingLeaseLiabilityUndiscountedExcessAmount100.0100.0100.0
Percentage of Assets0.00.00.0

Stockholders Equity

us-gaap:StockholdersEquity

us-gaap:StockholdersEquity


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-31
Value28912744273823932298209621942137205919251791173816981659171216991652159215311574155214751398135913101315127512661238118511531124109911361090112410851082110910861101108310711092104910101002890
Percentage of StockholdersEquity100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets28.427.928.325.224.723.425.024.524.023.222.521.822.021.722.321.822.021.520.821.421.621.020.219.719.319.619.419.319.118.618.417.918.017.916.119.119.119.219.318.920.520.520.50.00.00.019.60.0

us-gaap:StockholdersEquity us-gaap:ConsolidatedEntities

srt:ParentCompany


Stockholders
Period End2020-12-312019-12-312018-12-312017-12-31
Value2738219417911712
Percentage of StockholdersEquity100.0100.0100.0100.0
Percentage of Assets28.325.022.522.3
Percentage of Assets srt:ParentCompany84.080.880.479.2

us-gaap:StockholdersEquity us-gaap:CumulativeEffectPeriodOfAdoption, us-gaap:StatementEquityComponents

srt:CumulativeEffectPeriodOfAdoptionAdjustment, us-gaap:RetainedEarnings


Stockholders
Period End2021-03-312020-12-312020-06-302020-03-312019-12-312019-06-302018-12-312017-12-31
Value23632271210320832081196818581723
Percentage of StockholdersEquity86.182.991.599.494.995.6103.7100.6
Percentage of Assets24.023.422.623.223.723.023.422.4
Percentage of Assets srt:CumulativeEffectPeriodOfAdoptionAdjustment us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.0

us-gaap:StockholdersEquity us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value169134220187151-22.1178198683.024-77.956-92.576-84.517-68.2432031242.09-15.95627235-9.425-6.039-12.329231949684124171981548558524232212.7767.0244817-5.773-12.46-100.66686
Percentage of StockholdersEquity5.94.98.07.86.6-1.13.74.63.30.2-4.4-5.3-5.0-4.11.21.81.50.1-1.04.04.62.4-0.7-0.4-0.91.81.63.95.53.52.21.51.87.25.07.65.44.93.83.01.90.30.74.41.7-0.6-1.2-11.30.0
Percentage of Assets1.71.42.32.01.6-0.20.91.10.80.0-1.0-1.2-1.1-0.90.30.40.30.0-0.20.81.00.5-0.1-0.1-0.20.40.30.71.00.70.40.30.31.30.81.41.00.90.70.60.40.10.10.00.00.0-0.20.00.0
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AdditionalPaidInCapital


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value454446438438435427418412407398390385381375367362359354347342340333326320317312305300298294288284282276270267265262257253252248244241239235231217192
Percentage of StockholdersEquity15.716.316.018.318.920.419.119.319.820.721.822.222.522.621.521.321.822.222.721.821.922.623.423.624.223.823.923.724.124.825.025.325.724.424.823.824.524.223.223.422.922.922.822.122.823.323.124.40.0
Percentage of Assets4.54.54.54.64.74.84.84.74.84.84.94.85.04.94.84.64.84.84.74.74.74.84.74.74.74.74.64.64.64.64.64.54.64.44.04.54.74.74.54.44.74.74.70.00.00.04.50.00.0
Percentage of Assets us-gaap:AdditionalPaidInCapital0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value208208208207207207206206206206205205205205204204204204203203202202201201201200199199199199198197197197196196195195194194193193192192192191191190189
Percentage of StockholdersEquity7.27.67.68.79.09.99.49.710.010.711.511.812.112.411.912.012.412.813.312.913.113.714.414.815.415.315.715.716.116.817.217.618.017.418.017.418.118.117.517.917.617.918.017.618.319.019.121.40.0
Percentage of Assets2.12.12.12.22.22.32.42.42.42.52.62.62.72.72.72.62.72.82.82.82.82.92.92.93.03.03.03.03.13.13.23.23.23.12.93.33.43.53.43.43.63.73.70.00.00.03.70.00.0
Percentage of Assets us-gaap:CommonStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:RetainedEarnings


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value2467236322712159210320832080201219681908185818241779173116981679164116091568153815091474144614091370134513131280123412121202118411581139112511311120112711671158118511901176115911491137113811281105
Percentage of StockholdersEquity85.386.182.990.291.599.494.894.295.699.1103.7105.0104.8104.399.298.899.4101.1102.497.797.299.9103.4103.7104.6102.2103.0101.099.7102.3104.2105.3105.4100.2103.2100.6103.2104.1105.2106.6107.7109.9109.8106.2109.5112.6113.6126.70.0
Percentage of Assets24.324.023.422.722.623.223.723.123.023.023.422.823.122.622.121.521.821.721.320.921.021.020.920.420.220.120.019.519.019.019.218.919.018.016.619.219.720.020.320.122.122.622.50.00.00.022.30.00.0
Percentage of Assets us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:TreasuryStock


Stockholders
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-312009-12-312008-12-312007-12-31
Value-608.801-608.73-599.885-599.871-599.814-599.76-592.832-592.739-591.383-591.253-584.668-584.535-584.357-584.228-578.112-578.102-578.045-577.669-572.097-572.09-571.524-570.95-567.105-566.81-566.506-566.503-562.923-562.28-562.146-562.013-559.36-558.939-558.929-558.82-555.644-555.303-555.251-555.164-552.149-551.945-551.934-551.904-549.408-549.25-549.24-549.235-547.722-544.712-497.879
Percentage of StockholdersEquity-21.1-22.2-21.9-25.1-26.1-28.6-27.0-27.7-28.7-30.7-32.6-33.6-34.4-35.2-33.7-34.0-35.0-36.3-37.4-36.3-36.8-38.7-40.6-41.7-43.2-43.0-44.1-44.4-45.4-47.4-48.5-49.7-50.9-49.2-50.9-49.4-51.2-51.3-49.8-50.8-50.1-50.9-51.3-50.3-52.3-54.4-54.6-61.20.0
Percentage of Assets-6.0-6.2-6.2-6.3-6.4-6.7-6.7-6.8-6.9-7.1-7.4-7.3-7.6-7.6-7.5-7.4-7.7-7.8-7.8-7.8-7.9-8.1-8.2-8.2-8.4-8.5-8.6-8.5-8.7-8.8-8.9-8.9-9.1-8.8-8.2-9.4-9.8-9.9-9.6-9.6-10.3-10.5-10.50.00.00.0-10.70.00.0
Percentage of Assets us-gaap:TreasuryStock0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Common Stock Value

us-gaap:CommonStockValue

us-gaap:CommonStockValue


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value208208208207207207206206206206205205205205204204204204203203202202201201201200199199199199198197197197196196195195194194193193192191
Percentage of CommonStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets2.12.12.12.22.22.32.42.42.42.52.62.62.72.72.72.62.72.82.82.82.82.92.92.93.03.03.03.03.13.13.23.23.23.12.93.33.43.53.43.43.63.73.73.7

us-gaap:CommonStockValue us-gaap:ConsolidatedEntities

srt:ParentCompany


Common
Period End2020-12-312019-12-312018-12-312017-12-31
Value208206205204
Percentage of CommonStockValue100.0100.0100.0100.0
Percentage of Assets2.12.42.62.7
Percentage of Assets srt:ParentCompany6.47.69.29.5

Additional Paid In Capital Common Stock

us-gaap:AdditionalPaidInCapitalCommonStock

us-gaap:AdditionalPaidInCapitalCommonStock


Additional
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value454446438438435427418412407398390385381375367362359354347342340333326320317312305300298294288284282276270267265262257253252248244231
Percentage of AdditionalPaidInCapitalCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets4.54.54.54.64.74.84.84.74.84.84.94.85.04.94.84.64.84.84.74.74.74.84.74.74.74.74.64.64.64.64.64.54.64.44.04.54.74.74.54.44.74.74.74.5

us-gaap:AdditionalPaidInCapitalCommonStock us-gaap:ConsolidatedEntities

srt:ParentCompany


Additional
Period End2020-12-312019-12-312018-12-312017-12-31
Value438418390367
Percentage of AdditionalPaidInCapitalCommonStock100.0100.0100.0100.0
Percentage of Assets4.54.84.94.8
Percentage of Assets srt:ParentCompany13.515.417.517.0

Retained Earnings Accumulated Deficit

us-gaap:RetainedEarningsAccumulatedDeficit

us-gaap:RetainedEarningsAccumulatedDeficit


Retained
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value24672363227121592103208320802012196819081858182417791731169816791641160915681538150914741446140913701345131312801234121212021184115811391125113111201127116711581185119011761138
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets24.324.023.422.722.623.223.723.123.023.023.422.823.122.622.121.521.821.721.320.921.021.020.920.420.220.120.019.519.019.019.218.919.018.016.619.219.720.020.320.122.122.622.522.3

us-gaap:RetainedEarningsAccumulatedDeficit sigi:DividendsPaidToParent

srt:ParentCompany


Retained
Period End2020-12-312019-12-31
Value23002100
Percentage of RetainedEarningsAccumulatedDeficit101.3100.9
Percentage of Assets23.723.9
Percentage of Assets srt:ParentCompany0.00.0

us-gaap:RetainedEarningsAccumulatedDeficit us-gaap:ConsolidatedEntities

srt:ParentCompany


Retained
Period End2020-12-312019-12-312018-12-312017-12-31
Value2271208018581698
Percentage of RetainedEarningsAccumulatedDeficit100.0100.0100.0100.0
Percentage of Assets23.423.723.422.1
Percentage of Assets srt:ParentCompany69.776.683.478.5

Accumulated Other Comprehensive Income Loss Net Of Tax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value169134220187151-22.1178198683.024-77.956-92.576-84.517-68.2432031242.09-15.95627235-9.425-6.039-12.329231949684124171981548558524232212.7767.024-12.46
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.71.42.32.01.6-0.20.91.10.80.0-1.0-1.2-1.1-0.90.30.40.30.0-0.20.81.00.5-0.1-0.1-0.20.40.30.71.00.70.40.30.31.30.81.41.00.90.70.60.40.10.1-0.2

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:ConsolidatedEntities

srt:ParentCompany


Accumulated
Period End2020-12-312019-12-312018-12-312017-12-31
Value22081-77.95620
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0
Percentage of Assets2.30.9-1.00.3
Percentage of Assets srt:ParentCompany6.83.0-3.50.9

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:InformationByCategoryOfDebtSecurity

us-gaap:AvailableforsaleSecurities


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312016-12-31
Value254226307282252105170176147821.888-21.1098042
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax150.4168.4139.8151.0166.4-475.4208.5179.5215.12723.2-2.422.8399.8-264.4
Percentage of Assets2.52.33.23.02.71.21.92.01.71.00.0-0.31.00.6
Percentage of Assets us-gaap:AvailableforsaleSecurities0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:Investments


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312016-12-31
Value25321930527323965170176147821.888-21.2188042
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax149.6162.8138.6146.4157.5-298.1208.4179.5215.02723.0-2.422.9399.5-264.1
Percentage of Assets2.52.23.22.92.60.71.92.01.71.00.0-0.31.00.6
Percentage of Assets us-gaap:Investments0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:StatementEquityComponents

us-gaap:HeldtomaturitySecurities, us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302017-12-312016-12-31
Value0.0020.0040.0060.020.020.0450.0250.0450.0470.0640.071-0.038-0.0140.102
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax0.00.00.00.00.0-0.20.00.00.12.1-0.10.0-0.1-0.6
Percentage of Assets0.00.00.00.00.00.00.00.00.00.00.0-0.0-0.00.0
Percentage of Assets us-gaap:HeldtomaturitySecurities us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedOtherComprehensiveIncomeLossNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-312011-12-31
Value-83.969-84.517-85.064-86.856-87.452-88.047-88.643-78.27-78.795-79.319-79.844-71.358-71.778-72.198-60.405-57.083-57.412-57.742-58.072-51.399-52.449-53.434-54.42-57.273-58.383-59.494-60.605-25.91-26.157-26.405-26.652-37.448-68.287-54.953
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax-49.6-62.8-38.6-46.4-57.5398.1-108.4-79.5-115.0-2623.0102.477.184.9105.8-299.5-182.3-234.4-2762.8364.1-82.6-72.8-148.4577.4948.4473.5-251.9-306.3-52.7-38.5-63.6-107.2-219.2-126.4-129.9
Percentage of Assets-0.8-0.9-0.9-0.9-0.9-1.0-1.0-0.9-0.9-1.0-1.0-0.9-0.9-0.9-0.8-0.7-0.8-0.8-0.8-0.7-0.7-0.8-0.8-0.8-0.9-0.9-0.9-0.4-0.4-0.4-0.4-0.6-1.0-1.0
Percentage of Assets us-gaap:AccumulatedDefinedBenefitPlansAdjustment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedOtherComprehensiveIncome


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-312011-12-31
Value169134220187151-22.1178198683.024-77.956-92.576-84.517-68.2432031242.09-15.95627235-9.425-6.039-12.329231949684124175442
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets1.71.42.32.01.6-0.20.91.10.80.0-1.0-1.2-1.1-0.90.30.40.30.0-0.20.81.00.5-0.1-0.1-0.20.40.30.71.00.70.40.30.80.7
Percentage of Assets us-gaap:AccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedOtherThanTemporaryImpairment


Accumulated
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302012-12-312011-12-31
Value-1.448-7.541-2.546-8.494-13.539-39.257-0.071-0.071-0.071-0.071-0.071-0.071-0.071-0.071-0.059-0.102-0.146-0.15-0.15-0.288-0.288-0.282-0.282-0.282-0.282-0.282-0.514-0.514-1.294-1.599-1.599-1.599-1.658-3.5
Percentage of AccumulatedOtherComprehensiveIncomeLossNetOfTax-0.9-5.6-1.2-4.5-8.9177.5-0.1-0.1-0.1-2.30.10.10.10.1-0.3-0.3-0.6-7.20.9-0.5-0.4-0.83.04.72.3-1.2-2.6-1.0-1.9-3.9-6.4-9.4-3.1-8.3
Percentage of Assets-0.0-0.1-0.0-0.1-0.1-0.4-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.1
Percentage of Assets us-gaap:AccumulatedOtherThanTemporaryImpairment0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Treasury Stock Value

us-gaap:TreasuryStockValue

us-gaap:TreasuryStockValue


Treasury
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312009-12-31
Value608608599599599599592592591591584584584584578578578577572572571570567566566566562562562562559558558558555555555555552551551551549547
Percentage of TreasuryStockValue100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Assets6.06.26.26.36.46.76.76.86.97.17.47.37.67.67.57.47.77.87.87.87.98.18.28.28.48.58.68.58.78.88.98.99.18.88.29.49.89.99.69.610.310.510.510.7

us-gaap:TreasuryStockValue us-gaap:ConsolidatedEntities

srt:ParentCompany


Treasury
Period End2020-12-312019-12-312018-12-312017-12-31
Value599592584578
Percentage of TreasuryStockValue100.0100.0100.0100.0
Percentage of Assets6.26.77.47.5
Percentage of Assets srt:ParentCompany18.421.826.226.7

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value16213017318315839161151118461626928581151635-3.60366312755452533
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues19.316.221.723.623.25.922.121.316.76.725.314.96.113.126.53.88.6-0.916.98.06.914.211.66.58.4

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-147750000.0-110930000.0-190170000.0-75474000.0-106700000.0-315830000.0-152630000.0-135970000.0-112290000.0-142730000.0-148330000.0-65560000.0-99112000.0-54363000.0-109020000.0-11067000.0-28267000.0-36461000.0-60370000.0-26811000.0-19865000.0-50909000.0-39507000.0-7584000.0-25527000.0
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-17.6-13.8-23.8-9.7-15.6-47.5-20.9-19.1-15.9-20.4-23.1-14.0-21.5-12.1-25.0-2.6-6.7-9.1-15.3-6.7-4.9-12.9-10.1-2.0-6.5

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-14.105-25.63716-97.766-60.338283-10.85-12.572-9.07989-10.04-4.3471-4.687-6.406-5.357-8.08940-6.291-5.307-8.274-4.769-5.735-17.084-8.236
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-1.7-3.22.0-12.6-8.842.6-1.5-1.8-1.312.8-1.6-0.915.4-1.0-1.5-1.2-1.910.1-1.6-1.3-2.1-1.2-1.5-4.4-2.1

Net Cash Provided By Used In Operating Activities

us-gaap:NetCashProvidedByUsedInOperatingActivities

us-gaap:NetCashProvidedByUsedInOperatingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value16213017318315839161151118461626928581151635-3.60366312755452533
Percentage of NetCashProvidedByUsedInOperatingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues19.316.221.723.623.25.922.121.316.76.725.314.96.113.126.53.88.6-0.916.98.06.914.211.66.58.4

Net Income Loss

us-gaap:NetIncomeLoss

us-gaap:NetIncomeLoss


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value121109127693415815672614555581830464150393843374546333941532917253227211.308180.2881816-20.1422.325212317185.803
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues14.513.615.99.05.02.311.27.910.28.87.18.39.03.04.87.56.78.46.86.67.76.78.38.76.57.68.210.35.83.55.26.75.84.60.34.20.14.34.0-5.10.65.36.04.44.81.5

us-gaap:NetIncomeLoss us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParent, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value-1.7953.948-2.344-2.254-3.89120.00.0
Percentage of NetIncomeLoss-1.53.6-1.8-3.2-11.481.90.00.0
Percentage of Revenues-0.20.5-0.3-0.3-0.61.90.00.0
Percentage of Revenues us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithAllowanceForCreditLossParent us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.0

us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParent, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0.0460.477-2.963-0.406-1.3328.9480.1792.229-1.027-0.851
Percentage of NetIncomeLoss0.00.4-2.3-0.6-3.958.70.24.0-1.4-1.4
Percentage of Revenues0.00.1-0.4-0.1-0.21.30.00.3-0.1-0.1
Percentage of Revenues us-gaap:AociGainLossDebtSecuritiesAvailableForSaleWithoutAllowanceForCreditLossParent us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.0

us-gaap:HeldtomaturitySecurities, us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-30
Value-0.002-0.002-0.0140.0-0.0250.02-0.02-0.002-0.017-0.007-0.006-0.006-0.01-0.035
Percentage of NetIncomeLoss-0.0-0.0-0.00.0-0.10.1-0.0-0.0-0.0-0.0-0.0-0.0-0.1-0.1
Percentage of Revenues-0.0-0.0-0.00.0-0.00.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0-0.0
Percentage of Revenues us-gaap:HeldtomaturitySecurities us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-30
Value-1.2034.97-4.726-2.064-4.652220.6842.752-0.52-0.333178.9772.6814.0040.501-4.075-0.9231.2796.143-1.354-0.1722.6933.040.8483.216
Percentage of NetIncomeLoss-1.04.5-3.7-3.0-13.6144.60.84.9-0.7-0.538.116.24.621.21.7-8.7-2.22.515.6-3.5-0.47.36.71.89.5
Percentage of Revenues-0.10.6-0.6-0.3-0.73.30.10.4-0.1-0.02.71.40.40.60.1-0.7-0.20.21.1-0.2-0.00.50.60.20.6
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:PensionPlansDefinedBenefit


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.5480.5470.5950.5960.5950.5960.5250.5250.5240.5250.420.420.420.420.3780.3290.330.331.1791.05
Percentage of NetIncomeLoss0.40.50.50.91.73.90.60.90.70.90.90.80.72.21.20.70.80.73.02.7
Percentage of Revenues0.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.10.20.2
Percentage of Revenues us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome us-gaap:PensionPlansDefinedBenefit0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:NetIncomeLoss us-gaap:StatementEquityComponents

us-gaap:RetainedEarnings


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value121109127693415815672614555581830464150393843374546333941532917253227211.308180.2881816-20.1422.325212317185.803
Percentage of NetIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues14.513.615.99.05.02.311.27.910.28.87.18.39.03.04.87.56.78.46.86.67.76.78.38.76.57.68.210.35.83.55.26.75.84.60.34.20.14.34.0-5.10.65.36.04.44.81.5
Percentage of Revenues us-gaap:RetainedEarnings0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

Share Based Compensation

us-gaap:ShareBasedCompensation

us-gaap:ShareBasedCompensation


Share
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value4.4346.4932.2922.7374.167.0383.224.2034.9776.6772.3572.5143.8165.821.951.7673.0995.2731.4991.7472.8264.3771.3471.5772.3683.6811.2811.3191.9264.1761.2021.2392.4973.6920.6761.1031.8313.3291.0391.0970.6614.6255.481.113-0.4076.169
Percentage of ShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Investing Activities

us-gaap:NetCashProvidedByUsedInInvestingActivities

us-gaap:NetCashProvidedByUsedInInvestingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-147750000.0-110930000.0-190170000.0-75474000.0-106700000.0-315830000.0-152630000.0-135970000.0-112290000.0-142730000.0-148330000.0-65560000.0-99112000.0-54363000.0-109020000.0-11067000.0-28267000.0-36461000.0-60370000.0-26811000.0-19865000.0-50909000.0-39507000.0-7584000.0-25527000.0
Percentage of NetCashProvidedByUsedInInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-17.6-13.8-23.8-9.7-15.6-47.5-20.9-19.1-15.9-20.4-23.1-14.0-21.5-12.1-25.0-2.6-6.7-9.1-15.3-6.7-4.9-12.9-10.1-2.0-6.5

Payments To Acquire Property Plant And Equipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment

us-gaap:PaymentsToAcquirePropertyPlantAndEquipment


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302011-06-302011-03-312010-06-302010-03-31
Value4.934.5614.2065.2244.2188.4166.5627.4399.037.9554.964.4171.4771.3661.7040.866
Percentage of PaymentsToAcquirePropertyPlantAndEquipment100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Net Cash Provided By Used In Financing Activities

us-gaap:NetCashProvidedByUsedInFinancingActivities

us-gaap:NetCashProvidedByUsedInFinancingActivities


Net
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-14.105-25.63716-97.766-60.338283-10.85-12.572-9.07989-10.04-4.3471-4.687-6.406-5.357-8.08940-6.291-5.307-8.274-4.769-5.735-17.084-8.236
Percentage of NetCashProvidedByUsedInFinancingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0
Percentage of Revenues-1.7-3.22.0-12.6-8.842.6-1.5-1.8-1.312.8-1.6-0.915.4-1.0-1.5-1.2-1.910.1-1.6-1.3-2.1-1.2-1.5-4.4-2.1

Payments Of Dividends Common Stock

us-gaap:PaymentsOfDividendsCommonStock

us-gaap:PaymentsOfDividendsCommonStock


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1414141313131311111111101010108.9938.9678.9558.8738.3168.2998.278.2047.6377.627.5917.5296.9856.9666.9486.8846.8646.8446.8246.7566.7466.7296.7136.656.6386.626.6056.546.5176.5076.492
Percentage of PaymentsOfDividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Payments For Repurchase Of Common Stock

us-gaap:PaymentsForRepurchaseOfCommonStock

us-gaap:PaymentsForRepurchaseOfCommonStock


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value0.0718.8450.0140.0570.0546.9280.0931.3560.136.5850.1330.1780.1296.1160.010.0570.3765.5720.0070.5660.5743.8450.2950.3040.0033.580.6430.1340.1332.6530.4210.010.1093.1760.3410.0520.0873.0150.2040.0110.032.4960.1580.010.0051.513
Percentage of PaymentsForRepurchaseOfCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

Proceeds From Sale Of Short Term Investments

us-gaap:ProceedsFromSaleOfShortTermInvestments

us-gaap:ProceedsFromSaleOfShortTermInvestments


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value8601795125810981426185120238148422449152911087267371305683133710102137651285394448395354341377302337434434517449695474386466410404316391321435531591235
Percentage of ProceedsFromSaleOfShortTermInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax

sigi:AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax


Amortization
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value0.0030.002-0.0310.0010.031-0.0250.0250.0030.0210.009-0.1380.0080.0080.0120.0330.0540.0430.0490.0370.0130.0190.0720.0370.0970.1850.2610.2490.3730.2210.456-0.2260.4720.6140.6360.654-0.8270.6820.7940.00.6641.2581.1753.771.3830.802
Percentage of AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

sigi:AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax

sigi:AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax


Amortization
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-30
Value2000.02000.0-24000.0025000.0-20000.020000.02000.017000.07000.0-109000.06000.06000.010000.021000.035000.028000.032000.024000.09000.012000.047000.024000.063000.0120000.0170000.0161000.0243000.0
Percentage of AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax us-gaap:InformationByCategoryOfDebtSecurity, us-gaap:StatementEquityComponents

us-gaap:HeldtomaturitySecurities, us-gaap:AccumulatedNetUnrealizedInvestmentGainLoss


Amortization
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value2000.02000.0025000.0-20000.0
Percentage of AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleNetofTax100.0100.00.0100.0100.0

sigi:AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax

sigi:AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax


Amortization
Period End2021-06-302020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value1000.0-7000.01000.06000.0-5000.05000.01000.04000.02000.0-29000.02000.02000.02000.012000.019000.015000.017000.013000.04000.07000.025000.013000.034000.065000.091000.088000.0130000.077000.0160000.0-1183000.0165000.0215000.0223000.0229000.0-290000.0239000.0278000.00232000.0441000.0411000.01320000.0484000.0280000.0
Percentage of AmortizationOfNetUnrealizedGainsLossesOnHeldToMaturityTransferredFromAvailableForSaleTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0

sigi:ChangeInDirectPremiumsWritten

sigi:ChangeInDirectPremiumsWritten


Change
Period End2021-06-302021-03-31
Value120162
Percentage of ChangeInDirectPremiumsWritten100.0100.0

sigi:Commercialmortgageloanallowanceforcreditloss us-gaap:InvestmentType

sigi:Commercialmortgageloanallowanceforcreditloss

sigi:CommercialMortgageLoans


Commercialmortgageloanallowanceforcreditlossus-gaap:
Period End2020-09-302020-06-30
Value-2000.0-22000.0
Percentage of Commercialmortgageloanallowanceforcreditloss100.0100.0

sigi:Commercialmortgageloansrealizedgains

sigi:Commercialmortgageloansrealizedgains


Commercialmortgageloansrealizedgains
Period End2020-09-302020-06-302019-06-30
Value1000.01000.00
Percentage of Commercialmortgageloansrealizedgains100.0100.00.0

sigi:ComprehensiveIncomeLossBeforeTax

sigi:ComprehensiveIncomeLossBeforeTax


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value19727200129263-115.48180109173176705651-60.31552779395-69.918401171215875-8.53362124680504641-60.17370-52.826617.7993935-24.8732919-34.0246657
Percentage of ComprehensiveIncomeLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:ComprehensiveIncomeLossTax

sigi:ComprehensiveIncomeLossTax


Comprehensive
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value403.612402454-26.8515223533109.5529.38-15.84633242926-31.1191138391622-6.357180.0551124161310-24.65221-23.163161.991109.221-15.7518.7853.371-16.6031814
Percentage of ComprehensiveIncomeLossTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:Creditlossexpenseoninvestmentportfolio

sigi:Creditlossexpenseoninvestmentportfolio


Creditlossexpenseoninvestmentportfolio
Period End2020-09-302020-06-30
Value2.854-4.946
Percentage of Creditlossexpenseoninvestmentportfolio100.0100.0

sigi:Creditlossexpenseoninvestmentportfolio us-gaap:InvestmentType

us-gaap:AvailableforsaleSecurities


Creditlossexpenseoninvestmentportfolious-gaap:
Period End2021-06-302021-03-312020-06-302020-03-31
Value-2.2724.997-4.92315
Percentage of Creditlossexpenseoninvestmentportfolio0.00.099.50.0

us-gaap:HeldtomaturitySecurities


Creditlossexpenseoninvestmentportfolious-gaap:
Period End2021-06-302021-03-312020-06-30
Value0.0530.007-0.001
Percentage of Creditlossexpenseoninvestmentportfolio0.00.00.0

sigi:DebtAndEquitySecuritiesRealizedGains

sigi:DebtAndEquitySecuritiesRealizedGains


Debt
Period End2021-06-302021-03-312020-06-302020-03-31
Value2.0793.6766.4785.676
Percentage of DebtAndEquitySecuritiesRealizedGains100.0100.0100.0100.0

sigi:DebtAndEquitySecuritiesRealizedLosses

sigi:DebtAndEquitySecuritiesRealizedLosses


Debt
Period End2021-06-302021-03-312020-06-302020-03-31
Value1.8114.4713.8631.576
Percentage of DebtAndEquitySecuritiesRealizedLosses100.0100.0100.0100.0

sigi:DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross

sigi:DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross


Debt
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value-2.2724.997-2.968-2.853-4.92415
Percentage of DebtSecuritiesAvailableforsaleAllowanceforCreditLossGross100.0100.0100.0100.0100.0100.0

sigi:DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet

sigi:DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet


Debt
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value-1.7953.948-2.344-2.254-3.89120.00.0
Percentage of DebtSecuritiesAvailableforsaleAllowanceforCreditLossNet100.0100.0100.0100.0100.0100.00.00.0

sigi:DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax

sigi:DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax


Debt
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value-477000.01049000.0-624000.0-599000.0-1034000.03315000.0
Percentage of DebtSecuritiesAvailableforsaleAllowanceforCreditLossTax100.0100.0100.0100.0100.0100.0

sigi:EffectiveInterestRateforCalculationofInterestCost us-gaap:RetirementPlanType

sigi:EffectiveInterestRateforCalculationofInterestCost

us-gaap:PensionPlansDefinedBenefit


Effective
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-31
Value02.062.920500.0295000.0412000.0346-0.000100.0384
Percentage of EffectiveInterestRateforCalculationofInterestCost0.0100.0100.00.0100.00.00.0100.00.00.0100.0100.00.0100.0

sigi:EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLossSIGI us-gaap:InvestmentType

sigi:EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLossSIGI

sigi:InvestmentsAccountedForUnderTheEquityMethod


Equity
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value634958883045-2687.013811846
Percentage of EquityMethodInvestmentSummarizedFinancialInformationNetIncomeLossSIGI100.0100.0100.0100.0100.0100.0

sigi:IncomeAvailableToCommonStockholdersBeforeTax

sigi:IncomeAvailableToCommonStockholdersBeforeTax


Income
Period End2021-06-302021-03-312020-06-302020-03-31
Value1501334215
Percentage of IncomeAvailableToCommonStockholdersBeforeTax100.0100.0100.0100.0

sigi:IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables

sigi:IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value61106-8.95789524914293668236128541.7974530282348-0.40442-0.627-6.544214410-6.7883458384331382717136.311-43.6795126228.614-15.9581434
Percentage of IncreaseDecreaseInReservesForLossesAndLossExpensesNetOfReinsuranceRecoverables100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance

sigi:IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value9273-23.3942494-4.376-40.207235840-42.477375032-36.241324537-37.737364642-41.429374141-36.264321620
Percentage of IncreaseDecreaseInUnearnedPremiumsNetOfPrepaidReinsurance100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:InterestPaidOperatingandInvestingActivities

sigi:InterestPaidOperatingandInvestingActivities


Interest
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value5.8258.7226.0159.5296.0668.8545.8288.7496.0354.477
Percentage of InterestPaidOperatingandInvestingActivities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:LossReserveforCOVID19

sigi:LossReserveforCOVID19


Loss
Period End2020-09-30
Value0
Percentage of LossReserveforCOVID190.0

sigi:LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell

sigi:LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell


Losses
Period End2021-06-302021-03-312020-06-302020-03-31
Value0.0910.3620.61315
Percentage of LossesOnInvestmentSecuritiesForWhichWeHaveTheIntentToSell100.0100.0100.0100.0

sigi:NetChangeInUnrealizedAppreciationDepreciationOfEquityMethodInvestees us-gaap:InvestmentType

sigi:NetChangeInUnrealizedAppreciationDepreciationOfEquityMethodInvestees

sigi:InvestmentsAccountedForUnderTheEquityMethod


Net
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value494846302230-2862.91204173922235541434-1200.2461107213281418561117117-253.9-883.2-275.0-222.2-223.4-518.0628628207505104104378-417.5451-117.1
Percentage of NetChangeInUnrealizedAppreciationDepreciationOfEquityMethodInvestees100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:NetInvestmentIncomeOfEquityMethodInvestees us-gaap:InvestmentType

sigi:NetInvestmentIncomeOfEquityMethodInvestees

sigi:InvestmentsAccountedForUnderTheEquityMethod


Net
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302013-09-302013-06-302012-09-302012-06-30
Value8.448183-3.112-14.0174-150.111-6.4-35.4-10.3-88.0-9.925-55.4-55.4-4.646-10.6448.577598153975580
Percentage of NetInvestmentIncomeOfEquityMethodInvestees100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome

sigi:NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome


Non
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-312018-12-312018-09-302018-06-302017-12-312017-09-302017-06-302016-12-312016-09-302016-06-302015-12-312015-09-302015-06-302014-06-302014-03-312013-06-302013-03-31
Value7.888-8.9438.2927.29929-51.6580.00.00.00.00.00.00.0190.0040.00.0-0.0060.00.00.00.00.00.0310.02
Percentage of NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncome100.0100.0100.0100.0100.0100.00.00.00.00.00.00.0100.0100.00.00.0100.00.00.00.00.00.0100.0100.0

sigi:NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeGross

sigi:NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeGross


Non
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value9.985-11.32109.23937-65.39
Percentage of NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeGross100.0100.0100.0100.0100.0100.0

sigi:NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeTax

sigi:NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeTax


Non
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value2097000.0-2377000.02204000.01940000.07871000.0-13732000.0
Percentage of NonCreditPortionofOtherThanTemporaryImpairmentsRecognizedinOtherComprehensiveIncomeTax100.0100.0100.0100.0100.0100.0

sigi:OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax

sigi:OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax


O
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value46000.0477000.0-406000.0-1332000.08948000.02229000.0-1027000.0-851000.0
Percentage of OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesNetofTax100.0100.0100.0100.0100.0100.0100.0100.0

sigi:OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax

sigi:OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax


O
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value12000.0127000.0-109000.0-354000.02379000.0592000.0-273000.0-226000.0
Percentage of OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesTax100.0100.0100.0100.0100.0100.0100.0100.0

sigi:OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax

sigi:OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax


O
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value0.0580.604-0.515-1.686112.821-1.3-1.077
Percentage of OCIReclassificationAdjustmentfromAOCIforWritedownofSecuritiesbeforeTax100.0100.0100.0100.0100.0100.0100.0100.0

sigi:OTTILossesInvestmentsPortionRecognizedInEarningsNet

sigi:OTTILossesInvestmentsPortionRecognizedInEarningsNet


O
Period End2020-09-302019-09-30
Value2810000.0-2291000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet100.0100.0

sigi:OTTILossesInvestmentsPortionRecognizedInEarningsNet us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:AssetBackedSecurities, us-gaap:AvailableforsaleSecurities


O
Period End2020-09-30
Value173000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet6.2

us-gaap:CommercialMortgageBackedSecurities, us-gaap:AvailableforsaleSecurities


O
Period End2020-09-30
Value21000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet0.7

us-gaap:CorporateDebtSecurities, us-gaap:AvailableforsaleSecurities


O
Period End2020-09-302019-09-30
Value2454000.0-1681000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet87.373.4

us-gaap:CorporateDebtSecurities, us-gaap:HeldtomaturitySecurities


O
Period End2020-09-30
Value3000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet0.1

us-gaap:ForeignGovernmentDebtSecurities, us-gaap:AvailableforsaleSecurities


O
Period End2020-09-30
Value3000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet0.1

us-gaap:ResidentialMortgageBackedSecurities, us-gaap:AvailableforsaleSecurities


O
Period End2020-09-30
Value157000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet5.6

us-gaap:USStatesAndPoliticalSubdivisions, us-gaap:AvailableforsaleSecurities


O
Period End2020-09-30
Value2000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet0.1

sigi:OTTILossesInvestmentsPortionRecognizedInEarningsNet us-gaap:InvestmentType

sigi:CommercialMortgageLoans


O
Period End2020-09-30
Value-2000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet-0.1

us-gaap:AvailableforsaleSecurities


O
Period End2020-09-302019-09-30
Value2810000.0-1681000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet100.073.4

us-gaap:HeldtomaturitySecurities


O
Period End2020-09-30
Value3000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet0.1

us-gaap:ShortTermInvestments


O
Period End2020-09-30
Value-1000.0
Percentage of OTTILossesInvestmentsPortionRecognizedInEarningsNet-0.0

sigi:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax us-gaap:StatementEquityComponents

sigi:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax

us-gaap:AccumulatedOtherThanTemporaryImpairment


Other
Period End2021-06-302021-03-312020-12-31
Value1795000.0-3948000.010312000.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForNonCreditOtherThanTemporaryImpairedSecuritiesNetOfTax100.0100.0100.0

sigi:OtherImpairmentCharges

sigi:OtherImpairmentCharges


Other
Period End2020-09-302020-06-302020-03-31
Value-0.0440.61315
Percentage of OtherImpairmentCharges100.0100.0100.0

sigi:OtherImpairmentCharges us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:AssetBackedSecurities, us-gaap:AvailableforsaleSecurities


Other
Period End2020-09-302020-06-30
Value-0.0440.093
Percentage of OtherImpairmentCharges100.015.2

us-gaap:CommercialMortgageBackedSecurities, us-gaap:AvailableforsaleSecurities


Other
Period End2020-09-302020-06-30
Value-3.7040.0
Percentage of OtherImpairmentCharges8418.20.0

us-gaap:CorporateDebtSecurities, us-gaap:AvailableforsaleSecurities


Other
Period End2020-09-302020-06-30
Value-24.2060.5
Percentage of OtherImpairmentCharges55013.681.6

us-gaap:ResidentialMortgageBackedSecurities, us-gaap:AvailableforsaleSecurities


Other
Period End2020-09-302020-06-30
Value-0.1820.02
Percentage of OtherImpairmentCharges413.63.3

us-gaap:USStatesAndPoliticalSubdivisions, us-gaap:AvailableforsaleSecurities


Other
Period End2020-09-302020-06-30
Value-0.1240.0
Percentage of OtherImpairmentCharges281.80.0

us-gaap:USTreasuryAndGovernment, us-gaap:AvailableforsaleSecurities


Other
Period End2020-09-30
Value-0.028
Percentage of OtherImpairmentCharges63.6

sigi:OtherImpairmentCharges us-gaap:InvestmentType

us-gaap:AvailableforsaleSecurities


Other
Period End2020-09-302020-06-30
Value-0.0440.613
Percentage of OtherImpairmentCharges100.0100.0

sigi:OtherInvestmentsRealizedLosses

sigi:OtherInvestmentsRealizedLosses


Other
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value00-5000.0-1000.0030000.002709000.05000.000840000.005000.014000.00004000.0-1000.000654000.000002000000.0-80000.00-860000.0400000.0000
Percentage of OtherInvestmentsRealizedLosses0.00.0100.0100.00.0100.00.0100.0100.00.00.0100.00.0100.0100.00.00.00.0100.0100.00.00.0100.00.00.00.00.0100.0100.00.0100.0100.00.00.00.0

sigi:PaymentsToAcquireCommercialMortgageLoans

sigi:PaymentsToAcquireCommercialMortgageLoans


Payments
Period End2021-06-302021-03-312020-06-302020-03-31
Value-11085000.0-14860000.0-3838000.0-14096000.0
Percentage of PaymentsToAcquireCommercialMortgageLoans100.0100.0100.0100.0

sigi:PaymentstoAcquireEquitySecurities

sigi:PaymentstoAcquireEquitySecurities


Paymentsto
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value27481431328456.16415176.70236118.12938
Percentage of PaymentstoAcquireEquitySecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:Paymentstoacquirecommercialmortgageloans

sigi:Paymentstoacquirecommercialmortgageloans


Paymentstoacquirecommercialmortgageloans
Period End2020-09-302020-06-302020-03-312019-06-302019-03-31
Value-11866000.0-3838000.0-14096000.000
Percentage of Paymentstoacquirecommercialmortgageloans100.0100.0100.00.00.0

sigi:PercentageofunpaidNFIPclaimscededtofederalgovernment sigi:FloodCededPremiumsAndLosses

sigi:PercentageofunpaidNFIPclaimscededtofederalgovernment

sigi:NationalFloodInsuranceProgram


Percentageofunpaid
Period End2021-06-302021-03-31
Value0100.0
Percentage of PercentageofunpaidNFIPclaimscededtofederalgovernment0.0100.0

sigi:PeriodchangeunrealizedgainslossesinOCI us-gaap:FairValueByAssetClass, us-gaap:InvestmentType

sigi:PeriodchangeunrealizedgainslossesinOCI

us-gaap:AvailableforsaleSecurities, us-gaap:AssetBackedSecurities


Periodchangeunrealizedgainslossesin
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value1512000.0-1116000.01151000.01099000.01389000.0-1756000.0
Percentage of PeriodchangeunrealizedgainslossesinOCI100.0100.0100.0100.0100.0100.0

us-gaap:AvailableforsaleSecurities, us-gaap:CorporateDebtSecurities


Periodchangeunrealizedgainslossesin
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value4287000.0-2388000.01630000.0-645000.0-1771000.01000.0
Percentage of PeriodchangeunrealizedgainslossesinOCI283.5214.0141.6-58.7-127.5-0.1

us-gaap:AvailableforsaleSecurities, us-gaap:Investments


Periodchangeunrealizedgainslossesin
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value5885000.0-3603000.02821000.0529000.0-493000.0-1755000.0
Percentage of PeriodchangeunrealizedgainslossesinOCI389.2322.8245.148.1-35.599.9

us-gaap:AvailableforsaleSecurities, us-gaap:USStatesAndPoliticalSubdivisions


Periodchangeunrealizedgainslossesin
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value86000.0-99000.040000.075000.0-111000.00
Percentage of PeriodchangeunrealizedgainslossesinOCI5.78.93.56.8-8.0-0.0

sigi:Periodchangeunrealizedgainslossesinearnings us-gaap:FairValueByAssetClass, us-gaap:InvestmentType

sigi:Periodchangeunrealizedgainslossesinearnings

us-gaap:AvailableforsaleSecurities, us-gaap:AssetBackedSecurities


Periodchangeunrealizedgainslossesinearningsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value61000.0-143000.010000.0102000.0-135000.0-214000.000
Percentage of Periodchangeunrealizedgainslossesinearnings100.0100.0100.0100.0100.0100.00.00.0

us-gaap:AvailableforsaleSecurities, us-gaap:CorporateDebtSecurities


Periodchangeunrealizedgainslossesinearningsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value102000.0-91000.0-590000.0-72000.0-323000.0-61000.000
Percentage of Periodchangeunrealizedgainslossesinearnings167.263.6-5900.0-70.6239.328.50.00.0

us-gaap:AvailableforsaleSecurities, us-gaap:Investments


Periodchangeunrealizedgainslossesinearningsus-gaap:
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-06-302019-03-31
Value163000.0-234000.0-580000.030000.0-458000.0-275000.000
Percentage of Periodchangeunrealizedgainslossesinearnings267.2163.6-5800.029.4339.3128.50.00.0

sigi:ProceedsfromSaleofEquitySecurities

sigi:ProceedsfromSaleofEquitySecurities


Proceedsfrom
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value14420.00.00.01.321195263.733362.940
Percentage of ProceedsfromSaleofEquitySecurities100.0100.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:Proceedsfromequityinvestmentsinexcessofcurrentyearearnings

sigi:Proceedsfromequityinvestmentsinexcessofcurrentyearearnings


Proceedsfromequityinvestmentsinexcessofcurrentyearearnings
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value-492000.02309000.0-5352000.07874000.0614000.0110000.0386000.01771000.0
Percentage of Proceedsfromequityinvestmentsinexcessofcurrentyearearnings100.0100.0100.0100.0100.0100.0100.0100.0

sigi:RealizedGainsLossesOfEquityMethodInvestees us-gaap:InvestmentType

sigi:RealizedGainsLossesOfEquityMethodInvestees

sigi:InvestmentsAccountedForUnderTheEquityMethod


Realized
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-09-302012-06-30
Value139277673117916412110614312462959443-69.2-70.2-235.1245245193752209385279160-26.1-26.17463162162-22.11019
Percentage of RealizedGainsLossesOfEquityMethodInvestees100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:Realizedandunrealizedinvestmentchange

sigi:Realizedandunrealizedinvestmentchange


Realizedandunrealizedinvestmentchange
Period End2020-09-30
Value9900000.0
Percentage of Realizedandunrealizedinvestmentchange100.0

sigi:ShortTermInvestmentsAllowanceForCreditLoss us-gaap:InvestmentType

sigi:ShortTermInvestmentsAllowanceForCreditLoss

us-gaap:ShortTermInvestments


Short
Period End2020-09-30
Value-1000.0
Percentage of ShortTermInvestmentsAllowanceForCreditLoss100.0

sigi:ShortTermInvestmentsRealizedGains

sigi:ShortTermInvestmentsRealizedGains


Short
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312012-03-312011-03-31
Value18000.0315000.022000.06000.02000.02000.014000.0-13000.03000.02000.01000.0-4000.000000
Percentage of ShortTermInvestmentsRealizedGains100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.00.0

sigi:ShortTermInvestmentsRealizedLosses

sigi:ShortTermInvestmentsRealizedLosses


Short
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-31
Value7000.01000.0190000.0-79000.038000.01000.00-15000.01000.00-4000.0-8000.000000000002000.00000
Percentage of ShortTermInvestmentsRealizedLosses100.0100.0100.0100.0100.0100.00.0100.0100.00.0100.0100.00.00.00.00.00.00.00.00.00.00.0100.00.00.00.00.0

sigi:Taxoninvestmentincome

sigi:Taxoninvestmentincome


Taxoninvestmentincome
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-31
Value181417148.5581.10410101112-1.8458.5627.6175.2261113119.6026.3319.7528.2756.2635.9047.6146.254127.4371310118.52912109.205
Percentage of Taxoninvestmentincome100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:TotalInvestmentsrevenue

sigi:TotalInvestmentsrevenue


Total
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value9374754711536264
Percentage of TotalInvestmentsrevenue100.0100.0100.0100.0100.0100.0100.0100.0

sigi:TotalSegmentIncomeLossFromContinuingOperationsBeforeFederalIncomeTax us-gaap:StatementBusinessSegments

sigi:TotalSegmentIncomeLossFromContinuingOperationsBeforeFederalIncomeTax

sigi:OperatingSegmentsSIGI


Total
Period End2021-06-302021-03-312020-06-302020-03-31
Value1691525632
Percentage of TotalSegmentIncomeLossFromContinuingOperationsBeforeFederalIncomeTax100.0100.0100.0100.0

us-gaap:OperatingSegments


Total
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value96563211184107976180813783797385626976697677577170835137
Percentage of TotalSegmentIncomeLossFromContinuingOperationsBeforeFederalIncomeTax0.0100.0100.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

sigi:TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross

sigi:TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross


Total
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value43-109.0293943219-132.232-7.979378210129-10.734-21.131-80.778-11.3189.9833327-109.979-16.6895368-9.67.969-57.0074.1788.244-29.4394025-4.658-4.167-97.163-2.972-22.85397.06315311527-7.677-52.3894535
Percentage of TotalUnrealizedGainsLossesOnInvestmentSecuritiesGross100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax

sigi:TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax


Total
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value9.098-22.8968.3219.17846-27.769-1.6767.81517216.143-2.255-4.437-16.964-3.4953.494119.536-38.493-5.8411823-3.3612.789-19.9521.4622.886-10.305148.848-1.63-1.459-34.007-1.04-7.998132.4725.256105.5569.49-2.687-18.3361512
Percentage of TotalUnrealizedGainsLossesOnInvestmentSecuritiesTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:TotalUnrealizedGainsLossesonInvestmentSecurities

sigi:TotalUnrealizedGainsLossesonInvestmentSecurities


Total
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-30
Value-34.22386238-34.528-173.4881046.303-29.395-64.958-80.455-23.1068.47916637.823-6.489-22.077-17.717110-35.025-44.4366.239-5.1837-2.716-5.35819-26.235-16.431-3.028-2.708-63.1561.932-14.852254.591
Percentage of TotalUnrealizedGainsLossesonInvestmentSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

sigi:Totalinvestmentsegmentincomeafterfederalincometax

sigi:Totalinvestmentsegmentincomeafterfederalincometax


Totalinvestmentsegmentincomeafterfederalincometax
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value7560613810425051
Percentage of Totalinvestmentsegmentincomeafterfederalincometax100.0100.0100.0100.0100.0100.0100.0100.0

sigi:UnderwritingIncomeLossAfterFederalIncomeTaxes us-gaap:StatementBusinessSegments

sigi:UnderwritingIncomeLossAfterFederalIncomeTaxes

sigi:ESLines


Underwriting
Period End2021-06-302021-03-312020-06-302020-03-31
Value1.8220.408-0.423.037
Percentage of UnderwritingIncomeLossAfterFederalIncomeTaxes100.0100.0100.0100.0

sigi:ExcessAndSurplusOperations


Underwriting
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-5.748-0.423.0371.5142.3263.6173.2812.77-6.154-0.4461.23-7.1910.8571.021
Percentage of UnderwritingIncomeLossAfterFederalIncomeTaxes0.0100.0100.00.00.00.00.00.00.00.00.00.00.00.0

sigi:StandardCommercialLines


Underwriting
Period End2021-06-302021-03-312020-06-302020-03-312018-06-302018-03-312017-06-302017-03-31
Value53541313325.3752227
Percentage of UnderwritingIncomeLossAfterFederalIncomeTaxes2945.713456.9-3146.9445.50.00.00.00.0

sigi:StandardPersonalLines


Underwriting
Period End2021-06-302021-03-312020-06-302020-03-31
Value4.4596.079-4.9970.306
Percentage of UnderwritingIncomeLossAfterFederalIncomeTaxes244.71490.01189.810.1

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine


Underwriting
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value3313132329202720325.3752322
Percentage of UnderwritingIncomeLossAfterFederalIncomeTaxes0.0-3146.9445.50.00.00.00.00.00.00.00.00.0

us-gaap:PropertyAndCasualtyPersonalInsuranceProductLine


Underwriting
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value-11.379-4.9970.3060.937-0.4993.5852.5024.9832.4953.796-1.192.3315.316-3.7493.319
Percentage of UnderwritingIncomeLossAfterFederalIncomeTaxes0.01189.810.10.00.00.00.00.00.00.00.00.00.00.00.0

sigi:UnderwritingIncomeLossBeforeFederalIncomeTaxes us-gaap:StatementBusinessSegments

sigi:UnderwritingIncomeLossBeforeFederalIncomeTaxes

sigi:ESLines


Underwriting
Period End2021-06-302021-03-312020-06-302020-03-31
Value2.3060.516-0.5323.844
Percentage of UnderwritingIncomeLossBeforeFederalIncomeTaxes100.0100.0100.0100.0

sigi:ExcessAndSurplusOperations


Underwriting
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value-7.277-0.5323.8441.9162.9444.5794.1533.506-7.789-0.5651.892-11.0631.3191.57-3.456-2.362-2.5211.418-11.77-2.022-1.462-1.5490.819-1.371-0.0370.975-1.5490.013-2.2850.086-3.857-5.708-5.1-4.893
Percentage of UnderwritingIncomeLossBeforeFederalIncomeTaxes0.0100.0100.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

sigi:StandardCommercialLines


Underwriting
Period End2021-06-302021-03-312020-06-302020-03-312018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value67691617416.804363534424530403055443530212715-3.63
Percentage of UnderwritingIncomeLossBeforeFederalIncomeTaxes2946.113468.8-3144.7445.50.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

sigi:StandardPersonalLines


Underwriting
Period End2021-06-302021-03-312020-06-302020-03-312015-03-312014-03-31
Value5.6447.695-6.3250.387-2.466-2.36
Percentage of UnderwritingIncomeLossBeforeFederalIncomeTaxes244.81491.31188.910.10.00.0

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine


Underwriting
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value4216173037253426416.8043635
Percentage of UnderwritingIncomeLossBeforeFederalIncomeTaxes0.0-3144.7445.50.00.00.00.00.00.00.00.00.0

us-gaap:PropertyAndCasualtyPersonalInsuranceProductLine


Underwriting
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value-14.404-6.3250.3871.186-0.6314.5383.1676.3073.1584.805-1.5063.5878.179-5.7685.106-6.5824.2716.1258.6055.6312.826-4.655-2.466168.037-5.582-2.364.2851.362-2.9755.973-6.4177.22
Percentage of UnderwritingIncomeLossBeforeFederalIncomeTaxes0.01188.910.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

sigi:UnrealizedGainLossonEquitySecuritiesSold

sigi:UnrealizedGainLossonEquitySecuritiesSold


Unrealized
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.2031.1830.00.00.00.0030.028-21.426-0.279-1.9-6.471-8.1-1.2-9.0
Percentage of UnrealizedGainLossonEquitySecuritiesSold100.0100.00.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation us-gaap:StatementEquityComponents

us-gaap:AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation

us-gaap:TreasuryStock


Adjustments
Period End2021-06-302021-03-312020-06-302020-03-31
Value71000.05441000.054000.06928000.0
Percentage of AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation100.0100.0100.0100.0

us-gaap:AssumedPremiumsEarned sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

us-gaap:AssumedPremiumsEarned

sigi:DirectAssumedAndCededReinsuranceAmounts


Assumed
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value4.4115.6766.1476.0556.1736.356
Percentage of AssumedPremiumsEarned100.0100.0100.0100.0100.0100.0

us-gaap:AssumedPremiumsWritten sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

us-gaap:AssumedPremiumsWritten

sigi:DirectAssumedAndCededReinsuranceAmounts


Assumed
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value4.8725.5335.456.416.0436.882
Percentage of AssumedPremiumsWritten100.0100.0100.0100.0100.0100.0

us-gaap:AvailableForSaleSecuritiesGrossRealizedGains us-gaap:FinancialInstrument

us-gaap:AvailableForSaleSecuritiesGrossRealizedGains

us-gaap:AvailableForSaleSecurities


Available
Period End2020-09-302019-09-30
Value2.9551.078
Percentage of AvailableForSaleSecuritiesGrossRealizedGains100.0100.0

us-gaap:AvailableForSaleSecuritiesGrossRealizedLosses us-gaap:FinancialInstrument

us-gaap:AvailableForSaleSecuritiesGrossRealizedLosses

us-gaap:AvailableForSaleSecurities


Available
Period End2020-09-302019-09-30
Value2.3952.219
Percentage of AvailableForSaleSecuritiesGrossRealizedLosses100.0100.0

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect

us-gaap:CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect


Cash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-30
Value337000.0-6315000.0-664000.010258000.0-8969000.06631000.0-2188000.02520000.0
Percentage of CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CededPremiumsEarned sigi:FloodCededPremiumsAndLosses

us-gaap:CededPremiumsEarned

sigi:NationalFloodInsuranceProgram


Ceded
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value666768686766676563626361605860595757575656565758585855605958585756555453
Percentage of CededPremiumsEarned100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CededPremiumsEarned sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

sigi:DirectAssumedAndCededReinsuranceAmounts


Ceded
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value117118115109109105
Percentage of CededPremiumsEarned175.6174.9168.9161.8163.6160.4

us-gaap:CededPremiumsWritten sigi:FloodCededPremiumsAndLosses

us-gaap:CededPremiumsWritten

sigi:NationalFloodInsuranceProgram


Ceded
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value756560777462607471605470665653686356536263535062625344696557526462564958
Percentage of CededPremiumsWritten100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CededPremiumsWritten sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

sigi:DirectAssumedAndCededReinsuranceAmounts


Ceded
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value126116125116105115
Percentage of CededPremiumsWritten168.4176.6162.0156.8169.4154.5

us-gaap:CombinedRatio us-gaap:StatementBusinessSegments

us-gaap:CombinedRatio

sigi:ESLines


Combined
Period End2021-06-302021-03-312020-06-302020-03-31
Value96.699.2100.993.5
Percentage of CombinedRatio100.0100.0100.0100.0

sigi:ExcessAndSurplusOperations


Combined
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value112.01.0090.9350.9690.950.921-0.0270.9371.1471.011-0.0221.2040.9750.9690.0111.0451.0510.9710.0581.0441.0361.041-0.0071.0381.0010.970.0061.01.0760.997-0.0641.231
Percentage of CombinedRatio0.01.01.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

sigi:StandardCommercialLines


Combined
Period End2021-06-302021-03-312020-06-302020-03-312018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-31
Value88.788.296.796.70.9140.9850.0010.9210.9220.903-0.0060.9290.9020.923-0.0110.8870.9070.918-0.0050.9210.9561.01
Percentage of CombinedRatio91.888.995.8103.40.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

sigi:StandardPersonalLines


Combined
Period End2021-06-302021-03-312020-06-302020-03-312015-03-312014-03-31
Value92.389.6108.899.51.0341.032
Percentage of CombinedRatio95.590.3107.8106.40.00.0

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine


Combined
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value92.30.9670.9670.9420.9270.948-0.0050.9450.9140.9850.0010.921
Percentage of CombinedRatio0.01.01.00.00.00.00.00.00.00.00.00.0

us-gaap:PropertyAndCasualtyPersonalInsuranceProductLine


Combined
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value119.01.0880.9950.0041.0080.9410.959-0.0140.9590.9371.02-0.0030.8871.080.9280.0470.9380.9140.877-0.0250.9611.0651.034-0.0560.8921.075
Percentage of CombinedRatio0.01.11.10.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:CommonStockDividendsPerShareDeclared

us-gaap:CommonStockDividendsPerShareDeclared


Common
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-10-282015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value0.250.250.250.230.230.230.230.20.20.20.20.180.180.180.180.160.160.160.160.150.150.150.150.150.140.140.140.140.130.130.130.130.130.130.130.130.130.130.130.130.130.130.130.130.130.130.13
Percentage of CommonStockDividendsPerShareDeclared100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CurrentFederalTaxExpenseBenefit

us-gaap:CurrentFederalTaxExpenseBenefit


Current
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value32283417-1.359.886161317121110120.43313161714105.6251814169.1417.733125.7237.3738.7816.5384.1066.3676.2217.4534.057-5.088-0.57.17812-20.0013.1114.276-3.152-1.6911.3228.844
Percentage of CurrentFederalTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DebtAndEquitySecuritiesGainLoss

us-gaap:DebtAndEquitySecuritiesGainLoss


Debt
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0.268-0.7951.860.5732.6154.1-0.037202.8833.444-23.009-0.7510.0544.731-1.0486.871
Percentage of DebtAndEquitySecuritiesGainLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DebtAndEquitySecuritiesGainLoss us-gaap:FinancialInstrument

sigi:CommercialMortgageLoans


Debt
Period End2020-09-302020-06-302019-06-30
Value0.0010.0010.0
Percentage of DebtAndEquitySecuritiesGainLoss0.20.00.0

us-gaap:EquitySecurities


Debt
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0.00.0-0.0030.111210.8512.280.7358.6651.2268.069-0.5964.875
Percentage of DebtAndEquitySecuritiesGainLoss0.00.0-0.1-300.0105.829.566.2-3.2-1153.82270.4170.656.971.0

us-gaap:FixedIncomeSecurities


Debt
Period End2020-09-302020-06-302019-12-312019-09-302019-06-30
Value0.5612.3-0.153-1.1412.061
Percentage of DebtAndEquitySecuritiesGainLoss97.988.0413.5-5.671.5

us-gaap:OtherInvestments


Debt
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0.00.0-0.0050.00.0-0.030.007-2.709-0.0050.00.0-0.8260.0
Percentage of DebtAndEquitySecuritiesGainLoss0.00.0-0.1-0.00.0-1.00.211.80.70.00.078.80.0

us-gaap:ShortTermInvestments


Debt
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value0.0110.314-0.1680.005-0.0360.0010.014-0.0040.0020.002-0.003-0.0040.0
Percentage of DebtAndEquitySecuritiesGainLoss1.912.0-4.1-13.5-0.20.00.40.0-0.33.7-0.10.40.0

us-gaap:DebtAndEquitySecuritiesRealizedGainLossExcludingOtherThanTemporaryImpairment

us-gaap:DebtAndEquitySecuritiesRealizedGainLossExcludingOtherThanTemporaryImpairment


Debt
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-30
Value0.5732.6154.1202.8833.444-0.7510.054
Percentage of DebtAndEquitySecuritiesRealizedGainLossExcludingOtherThanTemporaryImpairment100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded


Debt
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value0.1555.667-3.0581.0250.86315
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded100.0100.0100.0100.0100.0100.0

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:AssetBackedSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value-0.061.001-0.210.0271.565
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded-38.717.7-20.53.19.9

us-gaap:AssetBackedSecurities, us-gaap:AvailableforsaleSecurities


Debt
Period End2020-12-312020-09-302020-06-30
Value1.9520.217-0.118
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded-63.821.2-13.7

us-gaap:CommercialMortgageBackedSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value0.0040.01-0.0210.0080.038
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded2.60.2-2.00.90.2

us-gaap:CommercialMortgageBackedSecurities, us-gaap:AvailableforsaleSecurities


Debt
Period End2020-12-312020-09-302020-06-30
Value0.0610.0210.015
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded-2.02.01.7

us-gaap:CorporateDebtSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value0.1484.0581.0160.81313
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded95.571.699.194.285.0

us-gaap:CorporateDebtSecurities, us-gaap:AvailableforsaleSecurities


Debt
Period End2020-12-312020-09-302020-06-30
Value9.6632.454-4.94
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded-316.0239.4-572.4

us-gaap:ForeignGovernmentDebtSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value-0.0070.056-0.0020.0070.021
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded-4.51.0-0.20.80.1

us-gaap:ForeignGovernmentDebtSecurities, us-gaap:AvailableforsaleSecurities


Debt
Period End2020-12-312020-09-302020-06-30
Value0.0440.0030.007
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded-1.40.30.8

us-gaap:ResidentialMortgageBackedSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value0.0030.356-0.1560.1240.722
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded1.96.3-15.214.44.6

us-gaap:ResidentialMortgageBackedSecurities, us-gaap:AvailableforsaleSecurities


Debt
Period End2020-12-312020-09-302020-06-30
Value1.3130.1570.125
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded-42.915.314.5

us-gaap:USStatesAndPoliticalSubdivisions, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value-0.1610.1860.0090.0150.029
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded-103.93.30.91.70.2

us-gaap:USStatesAndPoliticalSubdivisions, us-gaap:AvailableforsaleSecurities


Debt
Period End2020-12-312020-09-302020-06-30
Value0.0190.002-0.012
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded-0.60.2-1.4

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded us-gaap:InvestmentType

us-gaap:AvailableforsaleSecurities


Debt
Period End2020-09-302020-06-30
Value2.854-4.923
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded278.4-570.5

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal


Debt
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value-2427000.0-677000.0-3856000.0-5720000.00
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal100.0100.0100.0100.00.0

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:AssetBackedSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-30
Value-70000.0-106000.0-210000.0-145000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal2.915.75.42.5

us-gaap:CommercialMortgageBackedSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-30
Value-14000.0-15000.0-21000.07000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal0.62.20.5-0.1

us-gaap:CorporateDebtSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-30
Value-2403000.0-527000.0-3455000.0-5686000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal99.077.889.699.4

us-gaap:ForeignGovernmentDebtSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-30
Value-7000.0-1000.0-2000.07000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal0.30.10.1-0.1

us-gaap:ResidentialMortgageBackedSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-30
Value230000.0-39000.0-157000.0124000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal-9.55.84.1-2.2

us-gaap:USStatesAndPoliticalSubdivisions, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-30
Value-163000.011000.0-11000.0-27000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal6.7-1.60.30.5

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold


Debt
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value-437000.0-178000.0-144000.0-362000.0-468000.00
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold100.0100.0100.0100.0100.00.0

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:AssetBackedSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-30
Value-1000.0-17000.0-51000.0-58000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold0.29.614.112.4

us-gaap:CorporateDebtSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-30
Value-373000.0-147000.0-265000.0-395000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold85.482.673.284.4

us-gaap:ForeignGovernmentDebtSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2020-09-30
Value-19000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold5.2

us-gaap:ResidentialMortgageBackedSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302021-03-312020-09-302020-06-30
Value-63000.0-14000.0-27000.0-15000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold14.47.97.53.2

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery


Debt
Period End2021-06-302020-12-312020-09-302020-06-302020-03-31
Value-61000.0-9000.0-22000.0-67000.00
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery100.0100.0100.0100.00.0

us-gaap:DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:AssetBackedSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2020-09-30
Value-7000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery31.8

us-gaap:CorporateDebtSecurities, us-gaap:AvailableForSaleSecurities


Debt
Period End2021-06-302020-09-302020-06-30
Value-61000.0-15000.0-67000.0
Percentage of DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery100.068.2100.0

us-gaap:DebtSecuritiesHeldToMaturityAllowanceForCreditLossPeriodIncreaseDecrease us-gaap:FinancialInstrument, us-gaap:InvestmentType

us-gaap:DebtSecuritiesHeldToMaturityAllowanceForCreditLossPeriodIncreaseDecrease

us-gaap:CorporateDebtSecurities, us-gaap:HeldtomaturitySecurities


Debt
Period End2020-09-302020-06-30
Value3000.0-1000.0
Percentage of DebtSecuritiesHeldToMaturityAllowanceForCreditLossPeriodIncreaseDecrease100.0100.0

us-gaap:DebtSecuritiesHeldToMaturityAllowanceForCreditLossPeriodIncreaseDecrease us-gaap:InvestmentType

us-gaap:HeldtomaturitySecurities


Debt
Period End2020-09-302020-06-30
Value3000.0-1000.0
Percentage of DebtSecuritiesHeldToMaturityAllowanceForCreditLossPeriodIncreaseDecrease100.0100.0

us-gaap:DeferredFederalIncomeTaxExpenseBenefit

us-gaap:DeferredFederalIncomeTaxExpenseBenefit


Deferred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-0.702-2.062-2.131-2.039.86-9.1253.1381.2230.001-0.235-5.1081.3810.9240.573243.738-0.2822.8610.412110.3920.7592.199.7025.2644.32810141.3990.5724.8075.4652.858-0.89-10.5437.128-0.48-2.08-8.619-1.335-4.2151.9478.7474.921.435-7.79
Percentage of DeferredFederalIncomeTaxExpenseBenefit100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAmortizationOfGainsLosses

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-625000.0-625000.0-705000.0-704000.0-704000.0-704000.0-644000.0-644000.0-643000.0-644000.0-500000.0-494000.0-493000.0-494000.0-557000.0-481000.0-482000.0-481000.0-1575000.0-1763000.0
Percentage of DefinedBenefitPlanAmortizationOfGainsLosses100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value02.6803.296700.03330000.04460000.03780000.04410
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate0.0100.00.0100.00.0100.00.00.00.0100.00.00.00.0100.00.00.00.0100.00.0

us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-31
Value05.45.74200.0580000.0650000.06360000.06240
Percentage of DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets0.0100.0100.00.0100.00.00.00.0100.00.00.00.0100.00.00.00.0100.00.0

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanExpectedReturnOnPlanAssets

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value5.7445.7445.4775.4775.4765.4775.2795.2785.2785.2795.7235.6815.6815.6824.8564.8544.8554.8544.3275.006
Percentage of DefinedBenefitPlanExpectedReturnOnPlanAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanInterestCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanInterestCost

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value2.1492.1482.8282.8282.8282.8283.3773.3763.3763.3773.1433.0953.0953.0953.1583.1113.113.1113.0843.049
Percentage of DefinedBenefitPlanInterestCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost us-gaap:RetirementPlanType

us-gaap:DefinedBenefitPlanNetPeriodicBenefitCost

us-gaap:PensionPlansDefinedBenefit


Defined
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value-2.97-2.971-1.944-1.945-1.944-1.945-1.258-1.258-1.259-1.258-2.08-2.092-2.093-2.093-1.141-1.262-1.263-1.2620.332-0.153
Percentage of DefinedBenefitPlanNetPeriodicBenefitCost100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DepreciationAmortizationAndAccretionNet

us-gaap:DepreciationAmortizationAndAccretionNet


Depreciation
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value131314141415121412169.91313101113121212161515141514151414128.33410109.7589.955139.3079.8369.8029.7489.3858.9998.268.0018.5958.377.3547.451
Percentage of DepreciationAmortizationAndAccretionNet100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DirectPremiumsEarned sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

us-gaap:DirectPremiumsEarned

sigi:DirectAssumedAndCededReinsuranceAmounts


Direct
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value853837803733754752
Percentage of DirectPremiumsEarned100.0100.0100.0100.0100.0100.0

us-gaap:DirectPremiumsEarned us-gaap:LossContingenciesByNatureOfContingency

sigi:COVID19


Direct
Period End2020-09-302020-06-30
Value1651
Percentage of DirectPremiumsEarned2.07.0

us-gaap:DirectPremiumsEarned us-gaap:ProductOrService, us-gaap:LossContingenciesByNatureOfContingency

sigi:PremiumCredit, sigi:COVID19


Direct
Period End2020-09-302020-06-30
Value0.019
Percentage of DirectPremiumsEarned0.02.7

sigi:Returnauditandmidtermendorsementpremium, sigi:COVID19


Direct
Period End2020-09-302020-06-30
Value1631
Percentage of DirectPremiumsEarned2.04.3

us-gaap:DirectPremiumsWritten sigi:PremiumTransactionType

us-gaap:DirectPremiumsWritten

sigi:ChangeInDirectPremiumsWritten


Direct
Period End2021-03-31
Value87
Percentage of DirectPremiumsWritten100.0

us-gaap:DirectPremiumsWritten sigi:PremiumTransactionType, us-gaap:LossContingenciesByNatureOfContingency

sigi:Returnauditandmidtermendorsementpremium, sigi:COVID19


Direct
Period End2020-12-312020-09-302020-06-302020-03-31
Value0.00.00.075
Percentage of DirectPremiumsWritten0.00.00.00.0

us-gaap:DirectPremiumsWritten sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

sigi:DirectAssumedAndCededReinsuranceAmounts


Direct
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value954908839834746785
Percentage of DirectPremiumsWritten0.01044.60.00.00.00.0

us-gaap:DirectPremiumsWritten us-gaap:LossContingenciesByNatureOfContingency

sigi:COVID19


Direct
Period End2020-09-302020-06-30
Value0.019
Percentage of DirectPremiumsWritten0.00.0

us-gaap:DirectPremiumsWritten us-gaap:ProductOrService, us-gaap:LossContingenciesByNatureOfContingency

sigi:PremiumCredit, sigi:COVID19


Direct
Period End2020-09-302020-06-30
Value0.019
Percentage of DirectPremiumsWritten0.00.0

us-gaap:DividendsCommonStock us-gaap:StatementEquityComponents

us-gaap:DividendsCommonStock

us-gaap:RetainedEarnings


Dividends
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value1515151313131312121111101010109.4979.4689.4599.4078.8168.7948.7898.7338.1418.1228.1138.0587.4767.4567.4127.4047.437.3727.3517.2697.3027.2877.277.2227.2097.1947.176-49.6127.0887.0837.077
Percentage of DividendsCommonStock100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:DividendsPreferredStockCash us-gaap:StatementEquityComponents

us-gaap:DividendsPreferredStockCash

us-gaap:RetainedEarnings


Dividends
Period End2021-06-302021-03-31
Value2300000.02453000.0
Percentage of DividendsPreferredStockCash100.0100.0

us-gaap:EquitySecuritiesFvNiRealizedLoss

us-gaap:EquitySecuritiesFvNiRealizedLoss


Equity
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value003000.01000.028000.0107000.002259000.01919000.00330000.0
Percentage of EquitySecuritiesFvNiRealizedLoss0.00.0100.0100.0100.0100.00.0100.0100.00.0100.0

us-gaap:EquitySecuritiesFvNiUnrealizedGainLoss

us-gaap:EquitySecuritiesFvNiUnrealizedGainLoss


Equity
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value7.66111154.3385.701-17.137-0.558-20.3172.11510-13.806-2.611.115-14.0680.00.0
Percentage of EquitySecuritiesFvNiUnrealizedGainLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1 us-gaap:FairValueByAssetClass, us-gaap:IncomeStatementLocation, us-gaap:InvestmentType

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1

us-gaap:AvailableforsaleSecurities, sigi:NetInvestmentIncomeEarned, us-gaap:AssetBackedSecurities


Fair
Period End2021-06-302021-03-312020-12-312020-09-302019-12-312019-09-30
Value3000.03000.0-240000.02000.01000.00
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1100.0100.0100.0100.0100.00.0

us-gaap:AvailableforsaleSecurities, sigi:NetInvestmentIncomeEarned, us-gaap:CorporateDebtSecurities


Fair
Period End2021-06-302021-03-31
Value12000.01000.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1400.033.3

us-gaap:AvailableforsaleSecurities, sigi:NetInvestmentIncomeEarned, us-gaap:Investments


Fair
Period End2021-06-302021-03-312020-12-312020-09-302019-12-312019-09-30
Value15000.04000.024000.02000.01000.00
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1500.0133.3-10.0100.0100.00.0

us-gaap:AvailableforsaleSecurities, us-gaap:GainLossOnInvestmentsMember1, us-gaap:AssetBackedSecurities


Fair
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value61000.0-143000.0102000.0-135000.0-214000.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings12033.3-4766.75100.00.00.0

us-gaap:AvailableforsaleSecurities, us-gaap:GainLossOnInvestmentsMember1, us-gaap:CorporateDebtSecurities


Fair
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value102000.0-91000.0-72000.0-323000.0-61000.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings13400.0-3033.3-3600.00.00.0

us-gaap:AvailableforsaleSecurities, us-gaap:GainLossOnInvestmentsMember1, us-gaap:Investments


Fair
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value163000.0-234000.030000.0-458000.0-275000.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings15433.3-7800.01500.00.00.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss us-gaap:FairValueByAssetClass, us-gaap:InvestmentType

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss

us-gaap:AvailableforsaleSecurities, us-gaap:AssetBackedSecurities


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value1512000.0-1116000.01151000.01099000.01389000.0-1756000.0-247000.0104000.0107000.0-225000.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AvailableforsaleSecurities, us-gaap:CorporateDebtSecurities


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value4287000.0-2388000.01630000.0-645000.0-1771000.01000.0-49000.0-50000.0-19000.00
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss283.5214.0141.6-58.7-127.5-0.119.8-48.1-17.8-0.0

us-gaap:AvailableforsaleSecurities, us-gaap:Investments


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value5885000.0-3603000.02821000.0529000.0-493000.0-1755000.0-296000.054000.088000.0-225000.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss389.2322.8245.148.1-35.599.9119.851.982.2100.0

us-gaap:AvailableforsaleSecurities, us-gaap:USStatesAndPoliticalSubdivisions


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value86000.0-99000.040000.075000.0-111000.00
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInOtherComprehensiveIncomeLoss5.78.93.56.8-8.0-0.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases us-gaap:FairValueByAssetClass, us-gaap:InvestmentType

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases

us-gaap:AvailableforsaleSecurities, us-gaap:AssetBackedSecurities


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value6.96710142.0614.8594.8312.8782.423.5512
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:AvailableforsaleSecurities, us-gaap:CorporateDebtSecurities


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value4.3032127160.03.0020.00.00.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases61.8197.7193.4776.30.062.10.00.00.0

us-gaap:AvailableforsaleSecurities, us-gaap:Investments


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value113141184.8597.8332.8782.423.5512
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases161.8297.7293.4876.3100.0162.1100.0100.0100.0100.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements us-gaap:FairValueByAssetClass, us-gaap:InvestmentType

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements

us-gaap:AvailableforsaleSecurities, us-gaap:AssetBackedSecurities


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-1017000.0-412000.0-1608000.02000.0-1032000.00-174000.0-65000.0-40000.00
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements100.0100.0100.0100.0100.00.0100.0100.0100.00.0

us-gaap:AvailableforsaleSecurities, us-gaap:CorporateDebtSecurities


Fair
Period End2020-12-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-31
Value-145000.00-138000.00000
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements9.00.013.40.0-0.0-0.00.0

us-gaap:AvailableforsaleSecurities, us-gaap:Investments


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-1184000.0-412000.0-1753000.02000.0-1170000.00-174000.0-65000.0-40000.00
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements116.4100.0109.0100.0113.40.0100.0100.0100.00.0

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3 us-gaap:FairValueByAssetClass, us-gaap:InvestmentType

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3

us-gaap:AvailableforsaleSecurities, us-gaap:AssetBackedSecurities


Fair
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value5.1196.2940.0205.250.01.92911
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel3100.0100.00.0100.0100.00.0100.0100.0

us-gaap:AvailableforsaleSecurities, us-gaap:CorporateDebtSecurities


Fair
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value5.00.00.44.1920.750.00.016
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel397.70.00.020.814.30.00.0140.6

us-gaap:AvailableforsaleSecurities, us-gaap:Investments


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value3.2265.101106.2940.4276.00.01.92928
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel30.00.0197.7100.00.0135.2114.30.0100.0240.6

us-gaap:AvailableforsaleSecurities, us-gaap:USStatesAndPoliticalSubdivisions


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value0.05.1010.00.00.02.89
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersIntoLevel30.00.00.00.00.014.4

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3 us-gaap:FairValueByAssetClass, us-gaap:InvestmentType

us-gaap:FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3

us-gaap:AvailableforsaleSecurities, us-gaap:AssetBackedSecurities


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-4.904-0.49260.0-6.294-3.63-10.5530.0-19.6620.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3100.0100.0100.00.0100.0100.0100.00.0100.00.0

us-gaap:AvailableforsaleSecurities, us-gaap:Investments


Fair
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value-12.358-0.49260.0-6.294-3.63-10.5530.0-19.6620.0
Percentage of FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersOutOfLevel3252.0100.0100.00.0100.0100.0100.00.0100.00.0

us-gaap:FinanceLeaseInterestPaymentOnLiability

us-gaap:FinanceLeaseInterestPaymentOnLiability


Finance
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value2000.02000.02000.03000.04000.06000.04000.05000.07000.0000
Percentage of FinanceLeaseInterestPaymentOnLiability100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.0

us-gaap:FinanceLeasePrincipalPayments

us-gaap:FinanceLeasePrincipalPayments


Finance
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-30
Value114000.0115000.0121000.0115000.0172000.0142000.0166000.0215000.0312000.0284000.0755000.03558000.0
Percentage of FinanceLeasePrincipalPayments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:GainLossOnDispositionOfAssets1

us-gaap:GainLossOnDispositionOfAssets1


Gain
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-31
Value-7000.0-3000.00-3000.0-14000.021000.000-33000.00-29000.000-998000.0000
Percentage of GainLossOnDispositionOfAssets1100.0100.00.0100.0100.0100.00.00.0100.00.0100.00.00.0100.00.00.00.0

us-gaap:HeldtomaturitySecuritiesSoldSecurityRealizedGainLossExcludingOtherThanTemporaryImpairments

us-gaap:HeldtomaturitySecuritiesSoldSecurityRealizedGainLossExcludingOtherThanTemporaryImpairments


Heldtomaturity
Period End2020-09-30
Value1000.0
Percentage of HeldtomaturitySecuritiesSoldSecurityRealizedGainLossExcludingOtherThanTemporaryImpairments100.0

us-gaap:ImpairmentOfInvestments

us-gaap:ImpairmentOfInvestments


Impairment
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value-2.81-4.333310.2782.2910.9710.1041.121.4262.8211.20.080.0431.2113.4754.0150.3420.5593.593101.2824.4512.0949.7220.00.4190.9632.4590.680.5081.9190.4930.9210.040.2578.9362.693-0.1630.532-0.1014.091
Percentage of ImpairmentOfInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions

us-gaap:IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions


Income
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value20137.26212-12.9215.6023.9413.8983.9630.9714.0982.6150.7470.8811.2361.5822.910.6652.3651.628-0.611-1.066-1.1081.3361.424-3.5410.022-0.0070.1050.0330.0460.1710.007-0.426-0.561-0.5940.268-0.764-1.471.067-1.7562.4822.3741.4970.9463.895
Percentage of IncomeLossFromEquityMethodInvestmentsNetOfDividendsOrDistributions100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInDeferredPolicyAcquisitionCosts

us-gaap:IncreaseDecreaseInDeferredPolicyAcquisitionCosts


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value2014-38.9157.25415-1.605-45.2016.111128.142-40.535
Percentage of IncreaseDecreaseInDeferredPolicyAcquisitionCosts100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInEmployeeRelatedLiabilities

us-gaap:IncreaseDecreaseInEmployeeRelatedLiabilities


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value19-31.21620108.64-52.72212129.405-38.529109.98-5.115-41.363149.8996.855-36.55817-15.15-21.488-27.1151117-1.881-16.296.77612-4.688-21.8691014-1.645-4.5281.16811-0.343-5.3563.969
Percentage of IncreaseDecreaseInEmployeeRelatedLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInIncomeTaxes

us-gaap:IncreaseDecreaseInIncomeTaxes


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-31
Value-35.2052518-19.1158.0640.2765.3130.71-10.34612-15.9118.4526.2713.616158.411-9.68316-0.3849.154-2.9165.296-2.9768.7488.19811-2.273208.3024.3325.8445.819-2.1195.29-6.7622.008-7.2854.2278.167-10.171-5.0625.66322
Percentage of IncreaseDecreaseInIncomeTaxes100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInInterestAndDividendsReceivable

us-gaap:IncreaseDecreaseInInterestAndDividendsReceivable


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value23000.01101000.0-1349000.0573000.01814000.0-880000.01766000.061000.0908000.0491000.0612000.0-70000.0-866000.0864000.00884000.0-14000.0218000.0117000.0326000.01558000.0-528000.0572000.0-584000.0115000.0-510000.01454000.0-279000.0775000.0-414000.01327000.0-1021000.01450000.0-384000.0253000.0-1221000.01608000.0-1108000.01310000.0-1429000.0-159000.0-355000.0870000.01285000.0-524000.0730000.0
Percentage of IncreaseDecreaseInInterestAndDividendsReceivable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInOtherOperatingAssets

us-gaap:IncreaseDecreaseInOtherOperatingAssets


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value7.689144.539207.336-4.5833.52713138.711-13.5097.331-3.1229.6722212-8.955-15.9981312-6.25110-2.36513-4.8355.578
Percentage of IncreaseDecreaseInOtherOperatingAssets100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInOtherOperatingLiabilities

us-gaap:IncreaseDecreaseInOtherOperatingLiabilities


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value36-68.236332829-62.959341332-45.76921296.015-70.38714616.491-55.175291318-52.902483.4339-13.662
Percentage of IncreaseDecreaseInOtherOperatingLiabilities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncreaseDecreaseInPremiumsReceivable

us-gaap:IncreaseDecreaseInPremiumsReceivable


Increase
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value9259-15.068-15.85669-25.572-36.579-17.2286244-56.4055.755419-22.7575.4465626-29.9785.0345239-38.8026.3755038-32.9082.0693529-44.3440.6914736-35.565-3.6353225-18.648103715-46.289-8.7021110
Percentage of IncreaseDecreaseInPremiumsReceivable100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncurredClaimsPropertyCasualtyAndLiability

us-gaap:IncurredClaimsPropertyCasualtyAndLiability


Incurred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value421413383447403400385398380386367379366384341344341317322316298297286285291284268270297320288283279269307272287252245305274249242245239254
Percentage of IncurredClaimsPropertyCasualtyAndLiability100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:IncurredClaimsPropertyCasualtyAndLiability sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

sigi:DirectAssumedAndCededReinsuranceAmounts


Incurred
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value421413447403400398
Percentage of IncurredClaimsPropertyCasualtyAndLiability100.0100.0100.0100.0100.0100.0

us-gaap:IncurredClaimsPropertyCasualtyAndLiability us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:PensionPlansDefinedBenefit


Incurred
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-30
Value0.160.1590.1610.1620.1620.1620.1460.1460.1450.1450.1130.1120.1130.1120.1190.110.1110.110.4770.351
Percentage of IncurredClaimsPropertyCasualtyAndLiability0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.10.1

us-gaap:InvestmentIncomeInvestmentExpense

us-gaap:InvestmentIncomeInvestmentExpense


Investment
Period End2021-06-302021-03-312020-06-302020-03-31
Value5469000.03627000.03388000.03408000.0
Percentage of InvestmentIncomeInvestmentExpense100.0100.0100.0100.0

us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1

us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1


Liability
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value147802202001507019517413673204154134791821421175417512810244
Percentage of LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidCurrentYear1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1

us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1


Liability
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value212243160167198281173188196246142153208248161155189235123144189212
Percentage of LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1

us-gaap:LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1


Liability
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value421413383447403400385398380386367379366384341344341317322316298297
Percentage of LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaims1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:LossFromCatastrophes

us-gaap:LossFromCatastrophes


Loss
Period End2020-12-312020-09-302019-12-312019-09-30
Value19796.524
Percentage of LossFromCatastrophes100.0100.0100.0100.0

us-gaap:NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1

us-gaap:NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1


Noncash
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-31
Value32000.03000.0581000.0-51000.055000.05000.0-19000.0108000.0-162000.0162000.0291000.0-18000.018000.000000-570000.071000.0425000.0152000.00000
Percentage of NoncashOrPartNoncashAcquisitionFixedAssetsAcquired1100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.00.0100.0100.0100.0100.00.00.00.00.0

us-gaap:NoncashOrPartNoncashAcquisitionInvestmentsAcquired1 sigi:ScheduleOfCashFlowSupplumentalDisclosures

us-gaap:NoncashOrPartNoncashAcquisitionInvestmentsAcquired1

us-gaap:HeldtomaturitySecurities


Noncash
Period End2020-09-302020-06-302020-03-312019-06-302019-03-31
Value0.00.02.5960.00.0
Percentage of NoncashOrPartNoncashAcquisitionInvestmentsAcquired10.00.0100.00.00.0

us-gaap:NoncashOrPartNoncashAcquisitionInvestmentsAcquired1 us-gaap:InvestmentType

us-gaap:AvailableForSaleSecurities


Noncash
Period End2021-06-302021-03-312020-09-302020-06-302020-03-31
Value192614108.04
Percentage of NoncashOrPartNoncashAcquisitionInvestmentsAcquired10.00.00.00.0309.7

us-gaap:EquitySecurities


Noncash
Period End2020-12-312020-09-302019-12-312019-09-302018-12-31
Value10.00.00.0140.0
Percentage of NoncashOrPartNoncashAcquisitionInvestmentsAcquired10.00.00.00.00.0

us-gaap:OperatingLeasePayments

us-gaap:OperatingLeasePayments


Operating
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value2122000.02226000.02421000.02634000.02313000.02130000.02076000.02068000.02011000.01983000.00000
Percentage of OperatingLeasePayments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax us-gaap:InformationByCategoryOfDebtSecurity

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax

us-gaap:AvailableforsaleSecurities


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value28-81.6132829149-74.245-6.4622766816.105
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:Investments


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value35-90.5563637178-125.903-6.4622766816.105
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax128.1111.0129.3124.4119.9169.6100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value35-90.5563737178-125.903-17.36276681-2.801-17.036-18.955-67.398-11.646102316-84.302-8.4443642-6.4265.442-39.1615-29.545-8.98829216.194
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax128.1111.0133.5124.4119.9169.6268.6100.0100.0100.0-45.90.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:AccumulatedOtherThanTemporaryImpairment


Other
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value7.888-8.9437.29929-51.6580.00.00.00.00.00.00.00.00.00.0190.0040.00.00.0-0.0060.00.00.00.00.00.00.00.00.00.0
Percentage of OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax28.111.024.419.969.6-0.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:OtherComprehensiveIncomeLossBeforeTax

us-gaap:OtherComprehensiveIncomeLossBeforeTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-06-30
Value44-108.3364144220-131.478-21.11378210218-10.202-20.6-80.246-15.422103427-120.244-15.0745569-5.2129.678-55.2985.887-45.132-29.058402511-3.377-96.3748.491
Percentage of OtherComprehensiveIncomeLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value-0.693-0.693-2.269-0.754-0.753-0.75413-0.665-0.664-0.66410-0.532-0.531-0.5324.104-0.507-0.508-0.50710-1.615-1.517-1.516-4.388-1.709-1.709-1.70953-0.381-0.381-0.38-16.609-0.79-0.789-45.86624-1.429-1.428-1.428
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value-0.548-0.547-1.792-0.596-0.595-0.59610-0.525-0.524-0.5258.486-0.42-0.42-0.423.322-0.329-0.33-0.336.673-1.05-0.985-0.986-2.853-1.11-1.111-1.11134-0.247-0.248-0.247-10.796-0.513-0.513-29.81316-0.928-0.929-0.92810-0.702
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax

us-gaap:OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value-0.145-0.146-0.477-0.158-0.158-0.1582.758-0.14-0.14-0.1392.255-0.112-0.111-0.1120.782-0.178-0.178-0.1773.592-0.565-0.532-0.53-1.535-0.599-0.598-0.59818-0.134-0.133-0.133-5.813-0.277-0.276-16.0538.679-0.501-0.499-0.5
Percentage of OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax us-gaap:InformationByCategoryOfDebtSecurity

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax

us-gaap:AvailableforsaleSecurities


Other
Period End2021-06-302021-03-312020-12-31
Value-0.046-0.4772.963
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value-693000.0-693000.0-754000.0-754000.0-753000.0-754000.0-664000.0-665000.0-664000.0-664000.0-532000.0-532000.0-531000.0-532000.0-580000.0-507000.0-508000.0-507000.0-1814000.0-1615000.0-1517000.0-1516000.0-1950000.0-1709000.0-1709000.0-1709000.0-760000.0-381000.0-381000.0-380000.0-955000.0-790000.0-789000.0-1840000.0-1731000.0-1391000.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value-548000.0-547000.0-595000.0-596000.0-595000.0-596000.0-525000.0-525000.0-524000.0-525000.0-420000.0-420000.0-420000.0-420000.0-378000.0-329000.0-330000.0-330000.0-1179000.0-1050000.0-985000.0-986000.0-1268000.0-1110000.0-1111000.0-1111000.0-494000.0-247000.0-248000.0-247000.0-621000.0-513000.0-513000.0-1196000.0-1125000.0-904000.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedDefinedBenefitPlansAdjustment


Other
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-09-302016-06-302016-03-312015-09-30
Value-548000.0-547000.0-596000.0-595000.0-596000.0-525000.0-524000.0-525000.0-420000.0-420000.0-420000.0-329000.0-330000.0-330000.0-1050000.0-985000.0-986000.0-1110000.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax

us-gaap:OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-30
Value-145000.0-146000.0-159000.0-158000.0-158000.0-158000.0-139000.0-140000.0-140000.0-139000.0-112000.0-112000.0-111000.0-112000.0-202000.0-178000.0-178000.0-177000.0-635000.0-565000.0-532000.0-530000.0-682000.0-599000.0-598000.0-598000.0-266000.0-134000.0-133000.0-133000.0-334000.0-277000.0-276000.0-644000.0-606000.0-487000.0
Percentage of OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeLossTax

us-gaap:OtherComprehensiveIncomeLossTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302012-06-30
Value9.243-22.758.7989.33646-27.611-4.4347.95517213.888-2.143-4.326-16.852-4.2773.672129.713-42.085-5.2761924-1.8263.388-19.3542.06-15.795-10.171148.9814.183-1.182-33.7312.971
Percentage of OtherComprehensiveIncomeLossTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value35-103.3083537188-93.981-8.18134831027.728-21.565-23.993-85.315-11.507163525-117.615-12.9925565-12.3258.371-60.244238.685-13.8314532-6.1249.82-91.3143.684-16.679367.849192614
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-31
Value28-81.6132829149-74.245-6.4622766816.105-17.036-18.955-67.398-7.946102316-76.45-8.4443642-8.0115.442-39.16155.644-8.9882921-3.9816.383-59.3532.394-16.511235.10112
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax

us-gaap:OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-30
Value7.467-21.6957.5317.94739-19.736-1.7197.22417211.623-4.529-5.038-17.917-3.5615.855129.024-41.165-4.5481923-4.3142.929-21.0848.3913.041-4.8431511-2.1433.437-31.9611.29-5.839122.7486.9319.1915.148
Percentage of OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherGeneralExpense

us-gaap:OtherGeneralExpense


Other
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-30
Value9.1129.5543.9056.3459.066.3699.566127.453.283116.2898.464116.7537.9398.793116.7935.8725.679107.6143.0766.4517.0926.2615.9841.869134.0445.3843.1917.7325.7051.8863.0295.823.232.491
Percentage of OtherGeneralExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherUnderwritingExpense

us-gaap:OtherUnderwritingExpense


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value948897898495969086858680808389788282
Percentage of OtherUnderwritingExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:OtherUnderwritingExpense us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:RetirementPlanType

us-gaap:ReclassificationOutOfAccumulatedOtherComprehensiveIncome, us-gaap:PensionPlansDefinedBenefit


Other
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-31
Value0.5330.5340.5930.5920.5910.5920.5180.5190.5190.5190.4190.420.4180.420.4610.3970.3970.397
Percentage of OtherUnderwritingExpense0.60.60.60.70.70.60.50.60.60.60.50.50.50.50.50.50.50.5

us-gaap:PaymentsForLossesAndLossAdjustmentExpense

us-gaap:PaymentsForLossesAndLossAdjustmentExpense


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value359323380367348352368362333320347308343328344298306290298273292256
Percentage of PaymentsForLossesAndLossAdjustmentExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsOfDividendsPreferredStockAndPreferenceStock

us-gaap:PaymentsOfDividendsPreferredStockAndPreferenceStock


Payments
Period End2021-06-302021-03-31
Value2300000.02453000.0
Percentage of PaymentsOfDividendsPreferredStockAndPreferenceStock100.0100.0

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt

us-gaap:PaymentsToAcquireAvailableForSaleSecuritiesDebt


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value486671350411642319525439416474943642456875612323469724113943014626431026722523828322115618223030822230820825019922613797138114308303254142
Percentage of PaymentsToAcquireAvailableForSaleSecuritiesDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsToAcquireHeldToMaturitySecurities

us-gaap:PaymentsToAcquireHeldToMaturitySecurities


Payments
Period End2021-06-302021-03-312019-12-312019-09-302018-12-312018-09-302017-12-312017-09-302016-12-312016-09-302015-12-312015-09-30
Value2.259.00.00.00.03.50.00.00.00.03.3160.0
Percentage of PaymentsToAcquireHeldToMaturitySecurities100.0100.00.00.00.0100.00.00.00.00.0100.00.0

us-gaap:PaymentsToAcquireOtherInvestments

us-gaap:PaymentsToAcquireOtherInvestments


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value21181821112723151312212112132112101131175.011125.5813.6421.2231.7242.1192.4591.4244.6151.4683.4712.0642.3293.942.6953.3652.994.2554.0632.7075.0086.3253.1983.4367.714
Percentage of PaymentsToAcquireOtherInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PaymentsToAcquireShortTermInvestments

us-gaap:PaymentsToAcquireShortTermInvestments


Payments
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value8731723128711061282208619798498422416154812497077541254766123110272192615388303517352398333327317366398436503472644504435427368417336377316331453653303
Percentage of PaymentsToAcquireShortTermInvestments100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PolicyholderBenefitsAndClaimsIncurredGross sigi:LossReserve, us-gaap:ProductOrService

us-gaap:PolicyholderBenefitsAndClaimsIncurredGross

sigi:COVID19, sigi:CommercialProperty


Policyholder
Period End2020-09-30
Value0.0
Percentage of PolicyholderBenefitsAndClaimsIncurredGross0.0

us-gaap:PolicyholderBenefitsAndClaimsIncurredGross sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

sigi:DirectAssumedAndCededReinsuranceAmounts


Policyholder
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value460441530451425437
Percentage of PolicyholderBenefitsAndClaimsIncurredGross0.00.00.00.00.00.0

us-gaap:PolicyholderBenefitsAndClaimsIncurredGross us-gaap:LossContingenciesByNatureOfContingency

sigi:COVID19


Policyholder
Period End2020-09-302020-06-30
Value9.46837
Percentage of PolicyholderBenefitsAndClaimsIncurredGross0.00.0

sigi:NonCatastrophicLoss


Policyholder
Period End2020-09-30
Value0.0
Percentage of PolicyholderBenefitsAndClaimsIncurredGross0.0

us-gaap:PolicyholderBenefitsAndClaimsIncurredGross us-gaap:ProductOrService, us-gaap:LossContingenciesByNatureOfContingency

sigi:PremiumCredit, sigi:COVID19


Policyholder
Period End2020-09-302020-06-30
Value0.019
Percentage of PolicyholderBenefitsAndClaimsIncurredGross0.00.0

sigi:Returnauditandmidtermendorsementpremium, sigi:COVID19


Policyholder
Period End2020-09-302020-06-30
Value9.46818
Percentage of PolicyholderBenefitsAndClaimsIncurredGross0.00.0

us-gaap:PreferredStockDividendsPerShareDeclared

us-gaap:PreferredStockDividendsPerShareDeclared


Preferred
Period End2021-06-302021-03-31
Value287.5306.67
Percentage of PreferredStockDividendsPerShareDeclared100.0100.0

us-gaap:PremiumReceivableCreditLossExpenseReversal sigi:AllowanceforCreditLosses

us-gaap:PremiumReceivableCreditLossExpenseReversal

us-gaap:PremiumsReceivable


Premium
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value0.7330.8080.3820.8024.59711
Percentage of PremiumReceivableCreditLossExpenseReversal100.0100.0100.0100.0100.0100.0

us-gaap:PremiumsEarnedNetPropertyAndCasualty

us-gaap:PremiumsEarnedNetPropertyAndCasualty


Premiums
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value740724704694630651668653642632625614604591590572568560552542531522516507490476469462463456451437426420406406392378373358355351353354352356
Percentage of PremiumsEarnedNetPropertyAndCasualty100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:PremiumsEarnedNetPropertyAndCasualty sigi:LineOfBusinessBySegment, us-gaap:StatementBusinessSegments

sigi:ExcessAndSurplusOperations, sigi:CasualtyInsuranceProductLine


Premiums
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value434244474444444239384040
Percentage of PremiumsEarnedNetPropertyAndCasualty6.36.86.87.27.07.07.16.96.56.56.87.0

sigi:ExcessAndSurplusOperations, us-gaap:PropertyInsuranceProductLine


Premiums
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value161514141413131313131414
Percentage of PremiumsEarnedNetPropertyAndCasualty2.42.42.32.22.22.12.22.32.32.32.42.5

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine, sigi:BusinessOwnersPolicies


Premiums
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value272727262626252525252525
Percentage of PremiumsEarnedNetPropertyAndCasualty4.04.44.14.04.14.14.24.24.34.34.34.4

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine, sigi:CommercialAutomobile


Premiums
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value160138149141136131127124122118115111
Percentage of PremiumsEarnedNetPropertyAndCasualty23.222.023.021.621.220.720.520.320.220.019.619.5

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine, sigi:CommercialProperty


Premiums
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value979593898786848382807978
Percentage of PremiumsEarnedNetPropertyAndCasualty14.115.114.413.613.613.613.513.513.613.613.413.7

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine, sigi:OtherCommercial


Premiums
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value5.2665.1515.064.8414.7794.7064.6664.6084.5594.434.3594.31
Percentage of PremiumsEarnedNetPropertyAndCasualty0.80.80.80.70.70.70.70.80.80.70.70.8

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine, sigi:WorkersCompensation


Premiums
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value756166757878797880788177
Percentage of PremiumsEarnedNetPropertyAndCasualty10.99.810.211.512.212.412.812.813.213.313.813.6

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine, us-gaap:GeneralLiability


Premiums
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value181163164169164161158154153149146141
Percentage of PremiumsEarnedNetPropertyAndCasualty26.125.925.325.925.625.525.325.225.325.324.924.7

us-gaap:PropertyAndCasualtyCommercialInsuranceProductLine, us-gaap:SuretySegment


Premiums
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-30
Value9.2269.219.6398.998.9678.9048.7448.7788.3358.1348.1827.42
Percentage of PremiumsEarnedNetPropertyAndCasualty1.31.51.51.41.41.41.41.41.41.41.41.3

us-gaap:PropertyAndCasualtyPersonalInsuranceProductLine, sigi:Homeowners


Premiums
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value3131313131323232323232323232323232333233333333333333
Percentage of PremiumsEarnedNetPropertyAndCasualty4.55.04.84.84.85.05.15.25.35.35.45.55.65.75.85.95.96.36.36.46.66.97.17.17.37.2

us-gaap:PropertyAndCasualtyPersonalInsuranceProductLine, sigi:OtherPersonal


Premiums
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value2.1231.7922.1511.8811.9831.7122.0141.8812.0921.6441.6131.9881.7741.5421.5511.9071.7941.5321.5251.8251.7951.61.7482.1922.7252.946
Percentage of PremiumsEarnedNetPropertyAndCasualty0.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.30.40.40.30.40.50.60.6

us-gaap:PropertyAndCasualtyPersonalInsuranceProductLine, sigi:PersonalAutomobile


Premiums
Period End2020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-30
Value4238424243434343424140393837363634353536363637373738
Percentage of PremiumsEarnedNetPropertyAndCasualty6.16.16.56.46.66.86.86.97.06.96.86.86.76.66.66.66.46.76.87.17.27.57.88.08.18.2

us-gaap:PremiumsEarnedNetPropertyAndCasualty sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

sigi:DirectAssumedAndCededReinsuranceAmounts


Premiums
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value740724694630651653
Percentage of PremiumsEarnedNetPropertyAndCasualty100.0100.0100.0100.0100.0100.0

us-gaap:PremiumsEarnedNetPropertyAndCasualty us-gaap:ProductOrService, us-gaap:StatementBusinessSegments

sigi:BusinessOwnersPolicies, sigi:StandardCommercialLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value29282727
Percentage of PremiumsEarnedNetPropertyAndCasualty4.03.94.44.1

sigi:CasualtyInsuranceProductLine, sigi:ESLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value47434244
Percentage of PremiumsEarnedNetPropertyAndCasualty6.46.06.86.8

sigi:CommercialAutomobile, sigi:StandardCommercialLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value178171138149
Percentage of PremiumsEarnedNetPropertyAndCasualty24.023.722.023.0

sigi:CommercialProperty, sigi:StandardCommercialLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value1061029593
Percentage of PremiumsEarnedNetPropertyAndCasualty14.314.215.114.4

sigi:Homeowners, sigi:StandardPersonalLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value30303131
Percentage of PremiumsEarnedNetPropertyAndCasualty4.14.25.04.8

sigi:OtherCommercial, sigi:StandardCommercialLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value5.6795.525.1515.06
Percentage of PremiumsEarnedNetPropertyAndCasualty0.80.80.80.8

sigi:OtherPersonal, sigi:StandardPersonalLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value1.7141.831.7922.151
Percentage of PremiumsEarnedNetPropertyAndCasualty0.20.30.30.3

sigi:PersonalAutomobile, sigi:StandardPersonalLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value41413842
Percentage of PremiumsEarnedNetPropertyAndCasualty5.55.76.16.5

sigi:WorkersCompensation, sigi:StandardCommercialLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value74786166
Percentage of PremiumsEarnedNetPropertyAndCasualty10.010.89.810.2

us-gaap:GeneralLiability, sigi:StandardCommercialLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value197193163164
Percentage of PremiumsEarnedNetPropertyAndCasualty26.626.725.925.3

us-gaap:PropertyInsuranceProductLine, sigi:ESLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value19181514
Percentage of PremiumsEarnedNetPropertyAndCasualty2.72.52.42.3

us-gaap:SuretySegment, sigi:StandardCommercialLines


Premiums
Period End2021-06-302021-03-312020-06-302020-03-31
Value8.9938.5939.219.639
Percentage of PremiumsEarnedNetPropertyAndCasualty1.21.21.51.5

us-gaap:PremiumsReceivableAllowanceForDoubtfulAccountsRecoveries sigi:AllowanceforCreditLosses

us-gaap:PremiumsReceivableAllowanceForDoubtfulAccountsRecoveries

us-gaap:PremiumsReceivable


Premiums
Period End2021-06-302021-03-312020-12-312020-09-302020-06-30
Value93000.066000.0100000.0194000.00
Percentage of PremiumsReceivableAllowanceForDoubtfulAccountsRecoveries100.0100.0100.0100.00.0

us-gaap:PremiumsReceivableAllowanceForDoubtfulAccountsWriteOffsAgainstAllowance sigi:AllowanceforCreditLosses

us-gaap:PremiumsReceivableAllowanceForDoubtfulAccountsWriteOffsAgainstAllowance

us-gaap:PremiumsReceivable


Premiums
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value3526000.0874000.0482000.0996000.01597000.0653000.0
Percentage of PremiumsReceivableAllowanceForDoubtfulAccountsWriteOffsAgainstAllowance100.0100.0100.0100.0100.0100.0

us-gaap:PremiumsWrittenNet sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

us-gaap:PremiumsWrittenNet

sigi:DirectAssumedAndCededReinsuranceAmounts


Premiums
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value833798719724647676
Percentage of PremiumsWrittenNet100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromDebtNetOfIssuanceCosts

us-gaap:ProceedsFromDebtNetOfIssuanceCosts


Proceeds
Period End2020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302018-06-302018-03-31
Value1000.038715-0.4993410.00.0130
Percentage of ProceedsFromDebtNetOfIssuanceCosts100.00.0100.0100.0100.0100.00.00.0100.0

us-gaap:ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital

us-gaap:ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-31
Value1.0835.162115.5414.1973.1520.9184.5653.139114.9597.4939.7066.2214.9238.663.4156.4288.3255.1325.3867.994104.198115.8457.265.7882.0225.7041.4934.4692.633.447105.4673.1445.2999.956
Percentage of ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromIssuanceOfPreferredStockAndPreferenceStock

us-gaap:ProceedsFromIssuanceOfPreferredStockAndPreferenceStock


Proceeds
Period End2021-06-302021-03-31
Value0.0-0.479
Percentage of ProceedsFromIssuanceOfPreferredStockAndPreferenceStock0.0100.0

us-gaap:ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions

us-gaap:ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value2.9660.8242.9330.7473.2061.5252.6440.4993.341.762.2511.0712.4951.4352.8550.6992.4821.5632.9050.5382.891.4784.0731.9791.7662.2713.7290.4631.831.2612.8140.5362.6051.1642.2540.3611.4560.7692.2930.3631.3471.0081.8780.7741.6850.625
Percentage of ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value31031928027623322721317615086182144151160115139184116157219133130163148109145145114118104100126161124141100113846629471946869966
Percentage of ProceedsFromMaturitiesPrepaymentsAndCallsOfAvailableForSaleSecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities

us-gaap:ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value-0.4291.4612.2420.4460.7950.4056.0875.4194.0640.5798.1830.2693.170.484227.362121628297.21537261147201727199.39628391928263418383839613880679080
Percentage of ProceedsFromMaturitiesPrepaymentsAndCallsOfHeldToMaturitySecurities100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromSaleAndCollectionOfMortgageNotesReceivable

us-gaap:ProceedsFromSaleAndCollectionOfMortgageNotesReceivable


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-30
Value118000.099000.092000.055000.0
Percentage of ProceedsFromSaleAndCollectionOfMortgageNotesReceivable100.0100.0100.0100.0

us-gaap:ProceedsFromSaleOfAvailableForSaleSecuritiesDebt

us-gaap:ProceedsFromSaleOfAvailableForSaleSecuritiesDebt


Proceeds
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value94212751082001011328915321864844426267538594122594893119.20912390.0139.3051515181.302130.00.06.851115423146021491432298839
Percentage of ProceedsFromSaleOfAvailableForSaleSecuritiesDebt100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.0100.0100.0100.0100.0100.0100.0100.00.00.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ProceedsFromSaleOfOtherInvestments

us-gaap:ProceedsFromSaleOfOtherInvestments


Proceeds
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-302019-06-302019-03-312018-09-302013-12-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value0.1243.0043.8260.0530.05.4077.6144.9950.00.00.00.00.0010.00.00.00.0160.00.0-13.33713
Percentage of ProceedsFromSaleOfOtherInvestments100.0100.0100.0100.00.0100.0100.0100.00.00.00.00.0100.00.00.00.00.0100.00.00.0100.0100.0

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax us-gaap:InformationByCategoryOfDebtSecurity

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax

us-gaap:Investments


Reclassification
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-31
Value1.751-4.4235.3212.665.247-21.44-0.159-2.2271.0440.858-17.001
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax us-gaap:StatementEquityComponents

us-gaap:AccumulatedOtherComprehensiveIncome


Reclassification
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-31
Value1.203-4.974.7262.0644.652-22.036-0.684-2.7520.520.333-17.421-8.977-2.681-4.004-0.5014.0750.923-1.279-6.1431.3540.172-2.693-3.04-0.848-3.21611-0.2089.8992.8464.748-1.574
Percentage of ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax68.7112.488.877.688.7102.8430.2123.649.838.8102.50.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.00.0

us-gaap:ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

us-gaap:ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed

sigi:DirectAssumedAndCededReinsuranceAmounts


Reinsurance
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value3.2173.4474.2324.34.8984.362
Percentage of ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountAssumed100.0100.0100.0100.0100.0100.0

us-gaap:ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded sigi:FloodCededPremiumsAndLosses

us-gaap:ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded

sigi:NationalFloodInsuranceProgram


Reinsurance
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-30
Value182.2071248125.0969.4682721132989101526112156.541759924402515146.2499.22414267.379203451761094326.754-14.9222130115146.176118.122
Percentage of ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded sigi:ScheduleOfDirectAssumedAndCededReinsuranceAmounts

sigi:DirectAssumedAndCededReinsuranceAmounts


Reinsurance
Period End2021-06-302021-03-312020-09-302020-06-302020-03-312019-09-30
Value413186513043
Percentage of ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded220.01429.7180.0395.4595.9157.7

us-gaap:ReinsuranceRecoverableCreditLossExpenseReversal

us-gaap:ReinsuranceRecoverableCreditLossExpenseReversal


Reinsurance
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-31
Value-63000.063000.0-54000.0-565000.0894000.05000.0
Percentage of ReinsuranceRecoverableCreditLossExpenseReversal100.0100.0100.0100.0100.0100.0

us-gaap:RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability

us-gaap:RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability


Right
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-31
Value0183000.0205000.0090000.029000.0010000.0814000.00
Percentage of RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability0.0100.0100.00.0100.0100.00.0100.0100.00.0

us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability

us-gaap:RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability


Right
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-31
Value0.00.0160.286170.533.8280.160.7676.7456.1360.00.00.00.0
Percentage of RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability0.0100.0100.0100.0100.0100.0100.0100.0100.0100.00.00.00.00.0

us-gaap:StockIssuedDuringPeriodSharesDividendReinvestmentPlan

us-gaap:StockIssuedDuringPeriodSharesDividendReinvestmentPlan


Stock
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value0.006990.0070260.0078990.0069750.0064370.0047380.0052180.0056940.005810.005310.0060750.0062980.0063290.0068590.007170.0082490.0088760.0090570.0098770.0109310.0110660.0121040.013310.0135330.0139870.0143730.0146660.0152830.0133850.016450.01620.017314900.0220370.0236870.0229160.0256060.0272890.0247910.0226970.0249660.0281990.0275130.025759
Percentage of StockIssuedDuringPeriodSharesDividendReinvestmentPlan100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodSharesShareBasedCompensation

us-gaap:StockIssuedDuringPeriodSharesShareBasedCompensation


Stock
Period End2020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value0.0643260.0169360.0973650.3412360.0564210.0839790.101650.3716280.0558460.0514820.0837540.3492550.0979330.0225770.1152490.3997620.1063590.044930.1824670.3865670.1764420.0759080.1420620.4690140.1805310.0416680.1460110.4011790.1496680.0303330.1860140.4966478560.0312230.1271780.5403220.1766020.0293140.1243360.4534090.1484780.0662680.1392360.079289
Percentage of StockIssuedDuringPeriodSharesShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:StockIssuedDuringPeriodValueDividendReinvestmentPlan us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueDividendReinvestmentPlan

us-gaap:AdditionalPaidInCapital


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value416000.0429000.0429000.0401000.0407000.0408000.0415000.0366000.0364000.0365000.0366000.0327000.0333000.0353000.0370000.0332000.0345000.0348000.0354000.0339000.0345000.0351000.0360000.0337000.0331000.0346000.0349000.0315000.0322000.0320000.0344000.0349000.0354000.0349000.0355000.0352000.0354000.0358000.0351000.0350000.0356000.0360000.0367000.0365000.0365000.0368000.0
Percentage of StockIssuedDuringPeriodValueDividendReinvestmentPlan100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommonStock


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value11000.013000.014000.014000.016000.014000.013000.09000.011000.011000.012000.010000.012000.013000.012000.014000.015000.016000.017000.018000.020000.022000.022000.024000.027000.027000.028000.029000.029000.031000.027000.033000.032000.035000.043000.044000.047000.046000.051000.055000.049000.046000.050000.056000.056000.051000.0
Percentage of StockIssuedDuringPeriodValueDividendReinvestmentPlan2.63.03.33.53.93.43.12.53.03.03.33.13.63.73.24.24.34.64.85.35.86.36.17.18.27.88.09.29.09.77.89.59.010.012.112.513.312.814.515.713.812.813.615.315.313.9

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation us-gaap:StatementEquityComponents

us-gaap:StockIssuedDuringPeriodValueShareBasedCompensation

us-gaap:AdditionalPaidInCapital


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value7.6336.9965.0983.4547.2848.3995.7594.5998.1378.2014.4983.4836.1537.0854.612.4235.3986.5964.0952.3985.7996.9585.3093.3554.0347.1994.6111.7583.6655.8633.7711.7044.9435.7142.7721.4463.0394.6083.081.43.2583.6022.7741.7663.3663.309
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:CommonStock


Stock
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-312015-12-312015-09-302015-06-302015-03-312014-12-312014-09-302014-06-302014-03-312013-12-312013-09-302013-06-302013-03-312012-12-312012-09-302012-06-302012-03-312011-12-312011-09-302011-06-302011-03-312010-12-312010-09-302010-06-302010-03-31
Value0.1550.4970.1290.0340.1940.6830.1120.1690.2030.7430.1120.1030.1680.6980.1960.0450.230.80.2130.090.3650.7730.3530.1520.2840.9380.3610.0830.2930.8020.2990.060.3730.9930.3170.0630.2541.080.3540.0580.2490.9070.2970.1320.2780.159
Percentage of StockIssuedDuringPeriodValueShareBasedCompensation2.07.12.51.02.78.11.93.72.59.12.53.02.79.94.31.94.312.15.23.86.311.16.64.57.013.07.84.78.013.77.93.57.517.411.44.48.423.411.54.17.625.210.77.58.34.8

us-gaap:SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense

us-gaap:SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense


Supplemental
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value439447413470417407400416386397379391368388347352353331345331311312
Percentage of SupplementalInformationForPropertyCasualtyInsuranceUnderwritersCurrentYearClaimsAndClaimsAdjustmentExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent

us-gaap:SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense

sigi:ChangeinHistoricalClaimRateExperience


Supplemental
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312019-09-302019-06-302019-03-312018-12-312018-09-302018-06-302018-03-312017-12-312017-09-302017-06-302017-03-312016-12-312016-09-302016-06-302016-03-31
Value-18.008-33.769-116.1122136.95215185.70110-12.336-11.978-1.726-3.86-5.739-59.2611113-22.334-71.9661215
Percentage of SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0100.0

us-gaap:SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense us-gaap:ProductOrService, us-gaap:LiabilityForCatastropheClaimsByCatastrophicEvent

sigi:CasualtyInsuranceProductLine, sigi:ChangeinHistoricalClaimRateExperience


Supplemental
Period End2021-06-302021-03-312020-12-312020-09-302020-06-302020-03-312019-12-312018-12-312018-09-302018-06-302018-03-31
Value-17.0-35.0-135.075-15.0-10.02065-36.04.08.0
Percentage of SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense94.4103.6116.