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v2.4.1.9

Schedule III - Supplementary Insurance Information (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Deferred policy acquisition costs | $ 185,608 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts |  | $ 172,981 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts |  | $ 155,523 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts |
Reserve for loss and loss expenses | 3,477,870 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves |  | 3,349,770 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves |  | 4,068,941 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves |
Unearned premiums | 1,095,819 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums |  | 1,059,155 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums |  | 974,706 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums |
Net premiums earned | 1,852,609 us-gaap_SupplementaryInsuranceInformationPremiumRevenue |  | 1,736,072 us-gaap_SupplementaryInsuranceInformationPremiumRevenue |  | 1,584,119 us-gaap_SupplementaryInsuranceInformationPremiumRevenue |
Net investment income | 165,307 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome | [1] | 155,375 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome | [1] | 140,865 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome | [1]
Losses and loss expenses incurred | 1,157,501 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense |  | 1,121,738 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense |  | 1,120,990 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense |
Amortization of deferred policy acquisition costs | 364,295 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts | [2] | 331,828 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts | [3] | 298,547 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts | [4]
Other operating expenses | 252,670 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense | [5] | 243,740 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense | [6] | 228,589 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense | [7]
Net premiums written | 1,885,280 us-gaap_SupplementaryInsuranceInformationPremiumsWritten |  | 1,810,159 us-gaap_SupplementaryInsuranceInformationPremiumsWritten |  | 1,666,883 us-gaap_SupplementaryInsuranceInformationPremiumsWritten |
Policy acquisition costs | 624,470 sigi_PolicyAcquisitionCosts |  | 579,977 sigi_PolicyAcquisitionCosts |  | 526,143 sigi_PolicyAcquisitionCosts |
Other income | (16,945)us-gaap_OtherIncome |  | (12,294)us-gaap_OtherIncome |  | (9,118)us-gaap_OtherIncome |
Other expenses | 33,673 us-gaap_OtherCostAndExpenseOperating |  | 35,686 us-gaap_OtherCostAndExpenseOperating |  | 30,462 us-gaap_OtherCostAndExpenseOperating |
Total | 616,965 sigi_TotalOfAmortizationOfDeferredPolicyAcqusitionCostAndOperatingExpenses |  | 575,568 sigi_TotalOfAmortizationOfDeferredPolicyAcqusitionCostAndOperatingExpenses |  | 527,136 sigi_TotalOfAmortizationOfDeferredPolicyAcqusitionCostAndOperatingExpenses |
Standard Commercial Lines [Member] |  |  |  |  |  |
Deferred policy acquisition costs | 147,285 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 138,397 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 123,861 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |
Reserve for loss and loss expenses | 3,000,796 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 2,877,087 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 2,753,556 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |
Unearned premiums | 734,697 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 708,861 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 642,032 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |
Net premiums earned | 1,415,712 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 1,316,619 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 1,225,335 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |
Net investment income | 0 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember | [1] | 0 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember | [1] | 0 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember | [1]
Losses and loss expenses incurred | 870,018 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 831,261 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 853,143 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |
Amortization of deferred policy acquisition costs | 295,774 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember | [2] | 270,443 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember | [3] | 247,016 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember | [4]
Other operating expenses | 188,699 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember | [5] | 181,059 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember | [6] | 166,111 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember | [7]
Net premiums written | 1,441,047 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 1,380,740 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |  | 1,263,738 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardCommercialLinesMember |
Standard Personal Lines [Member] |  |  |  |  |  |
Deferred policy acquisition costs | 17,495 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 18,149 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 17,690 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |
Reserve for loss and loss expenses | 279,761 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 312,411 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 1,195,082 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |
Unearned premiums | 285,777 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 286,969 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 275,886 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |
Net premiums earned | 296,747 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 294,332 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 279,555 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |
Net investment income | 0 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember | [1] | 0 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember | [1] | 0 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember | [1]
Losses and loss expenses incurred | 197,182 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 206,450 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 204,644 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |
Amortization of deferred policy acquisition costs | 34,851 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember | [2] | 33,097 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember | [3] | 33,684 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember | [4]
Other operating expenses | 48,178 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember | [5] | 46,140 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember | [6] | 44,741 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember | [7]
Net premiums written | 292,061 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 297,757 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |  | 289,848 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = sigi_StandardPersonalLinesMember |
Excess And Surplus Operations [Member] |  |  |  |  |  |
Deferred policy acquisition costs | 20,828 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 16,435 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 13,972 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |
Reserve for loss and loss expenses | 197,313 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 160,272 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 120,303 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |
Unearned premiums | 75,345 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 63,325 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 56,788 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |
Net premiums earned | 140,150 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 125,121 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 79,229 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |
Net investment income | 0 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember | [1] | 0 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember | [1] | 0 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember | [1]
Losses and loss expenses incurred | 90,301 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 84,027 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 63,203 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |
Amortization of deferred policy acquisition costs | 33,670 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember | [2] | 28,288 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember | [3] | 17,847 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember | [4]
Other operating expenses | 15,793 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember | [5] | 16,541 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember | [6] | 17,737 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember | [7]
Net premiums written | 152,172 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 131,662 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |  | 113,297 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = sigi_ExcessAndSurplusOperationsMember |
Investments Segment [Member] |  |  |  |  |  |
Deferred policy acquisition costs | 0 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |
Reserve for loss and loss expenses | 0 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |
Unearned premiums | 0 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationUnearnedPremiums / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |
Net premiums earned | 0 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationPremiumRevenue / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |
Net investment income | 165,307 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember | [1] | 155,375 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember | [1] | 140,865 us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember | [1]
Losses and loss expenses incurred | 0 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |
Amortization of deferred policy acquisition costs | 0 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember | [2] | 0 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember | [3] | 0 us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember | [4]
Other operating expenses | 0 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember | [5] | 0 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember | [6] | 0 us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember | [7]
Net premiums written | 0 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |  | 0 us-gaap_SupplementaryInsuranceInformationPremiumsWritten / us-gaap_StatementBusinessSegmentsAxis = us-gaap_InvestmentsSegmentMember |
Miscellaneous Income [Member] |  |  |  |  |  |
Other income | (16,598)us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_MiscellaneousIncomeMember | [5] | (12,201)us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_MiscellaneousIncomeMember | [6] | (8,827)us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = sigi_MiscellaneousIncomeMember | [7]
Other Income [Member] |  |  |  |  |  |
Other income | (347)us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_OtherIncomeMember |  | (93)us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_OtherIncomeMember |  | (291)us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_OtherIncomeMember |
Miscellaneous Expense [Member] |  |  |  |  |  |
Other expenses | 9,093 us-gaap_OtherCostAndExpenseOperating / us-gaap_StatementBusinessSegmentsAxis = sigi_MiscellaneousExpenseMember | [5] | 7,792 us-gaap_OtherCostAndExpenseOperating / us-gaap_StatementBusinessSegmentsAxis = sigi_MiscellaneousExpenseMember | [6] | 9,820 us-gaap_OtherCostAndExpenseOperating / us-gaap_StatementBusinessSegmentsAxis = sigi_MiscellaneousExpenseMember | [7]
Other Expense [Member] |  |  |  |  |  |
Other expenses | $ 24,580 us-gaap_OtherCostAndExpenseOperating / us-gaap_StatementBusinessSegmentsAxis = us-gaap_OtherExpenseMember |  | $ 27,894 us-gaap_OtherCostAndExpenseOperating / us-gaap_StatementBusinessSegmentsAxis = us-gaap_OtherExpenseMember |  | $ 20,642 us-gaap_OtherCostAndExpenseOperating / us-gaap_StatementBusinessSegmentsAxis = us-gaap_OtherExpenseMember |
[1] | Includes “Net investment income earned” and “Net realized investment gains” on the Consolidated Statements of Income.
[2] | The total of “Amortization of deferred policy acquisition costs” of $364,295 and “Other operating expenses” of $252,670 reconciles to the Consolidated Statements of Income as follows:
[3] | The total of “Amortization of deferred policy acquisition costs” of $331,828 and “Other operating expenses” of $243,740 reconciles to the Consolidated Statements of Income as follows:
[4] | The total of “Amortization of deferred policy acquisition costs” of $298,547 and “Other operating expenses” of $228,589 reconciles to the Consolidated Statements of Income as follows:
[5] | In addition to amounts related to the Standard Commercial Lines, Standard Personal Lines, and E&S Lines, “Other income” and “Other expenses” on the Consolidated Statements of Income includes holding company income and expense amounts of $347 and $24,580, respectively.
[6] | In addition to amounts related to the Standard Commercial Lines, Standard Personal Lines, and E&S Lines, “Other income” and “Other expenses” on the Consolidated Statements of Income includes holding company income and expense amounts of $93 and $27,894, respectively.
[7] | In addition to amounts related to the Standard Commercial Lines, Standard Personal Lines, and E&S Lines, “Other income” and “Other expenses” on the Consolidated Statements of Income includes holding company income and expense amounts of $291 and $20,642, respectively.

X
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