XML 79 R83.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Reserve for Losses and Loss Expenses (Reserve Loss Development) (Details) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years | $ 592,062,000 us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1 | $ 572,434,000 us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1 | $ 632,742,000 us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1
Favorable or adverse loss development | (59,269,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense | (25,525,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense | (25,601,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense
Property Development |  | 11,000,000 sigi_PropertyDevelopment |
Favorable or unfavorable loss development [Member] |  |  |
Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years | 59,300,000 us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1 / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember | 25,500,000 us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1 / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember | 25,500,000 us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1 / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember
Favorable or adverse loss development | (59,300,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember | (25,500,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember | (25,500,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember
Property Development | 11,100,000 sigi_PropertyDevelopment / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember |  | 7,500,000 sigi_PropertyDevelopment / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember
Casualty Development | 48,200,000 sigi_CasualtyDevelopment / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember | 14,500,000 sigi_CasualtyDevelopment / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember | 18,000,000 sigi_CasualtyDevelopment / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember
Favorable or unfavorable loss development [Member] | General Liability [Member] |  |  |
Favorable or adverse loss development | (43,900,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = us-gaap_GeneralLiabilityMember | (20,000,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = us-gaap_GeneralLiabilityMember | 2,500,000 us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = us-gaap_GeneralLiabilityMember
Favorable or unfavorable loss development [Member] | Commercial Automobile [Member] |  |  |
Favorable or adverse loss development | (4,100,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_CommercialAutomobileMember | (4,500,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_CommercialAutomobileMember | (8,500,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_CommercialAutomobileMember
Favorable or unfavorable loss development [Member] | Workers' Compensation [Member] |  |  |
Favorable or adverse loss development | 0 us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_WorkersCompensationMember | 23,500,000 us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_WorkersCompensationMember | 2,500,000 us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_WorkersCompensationMember
Favorable or unfavorable loss development [Member] | Business Owners' Policies [Member] |  |  |
Favorable or adverse loss development | 1,900,000 us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_BusinessOwnersPoliciesMember | (9,500,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_BusinessOwnersPoliciesMember | (9,000,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_BusinessOwnersPoliciesMember
Favorable or unfavorable loss development [Member] | Commercial Property [Member] |  |  |
Favorable or adverse loss development | (2,100,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | (7,500,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | (3,500,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember
Favorable or unfavorable loss development [Member] | Homeowners [Member] |  |  |
Favorable or adverse loss development | (4,000,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_HomeownersMember | (2,500,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_HomeownersMember | (9,000,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_HomeownersMember
Favorable or unfavorable loss development [Member] | Personal Automobile [Member] |  |  |
Favorable or adverse loss development | (10,800,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_PersonalAutomobileMember | (3,000,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_PersonalAutomobileMember | 500,000 us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_PersonalAutomobileMember
Favorable or unfavorable loss development [Member] | Excess And Surplus Operations [Member] |  |  |
Favorable or adverse loss development | 3,700,000 us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_ExcessAndSurplusOperationsMember | (2,000,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_ExcessAndSurplusOperationsMember | 0 us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = sigi_ExcessAndSurplusOperationsMember
Favorable or unfavorable loss development [Member] | Remaining Lines Of Business [Member] |  |  |
Favorable or adverse loss development | $ 0 us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = us-gaap_OtherInsuranceProductLineMember | $ 0 us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = us-gaap_OtherInsuranceProductLineMember | $ (1,000,000)us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense / us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis = sigi_ChangeinHistoricalClaimRateExperienceMember / us-gaap_ReinsurancePremiumsForInsuranceCompaniesByProductSegmentAxis = us-gaap_OtherInsuranceProductLineMember

X
- Definition Amount of provision in the period for casualty claims incurred in prior reporting periods and related claims settlement costs. + References No definition available. + Details
Name: | sigi_CasualtyDevelopment
Namespace Prefix: | sigi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of provision in the period for property claims incurred in prior reporting periods and related claims settlement. + References No definition available. + Details
Name: | sigi_PropertyDevelopment
Namespace Prefix: | sigi_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of payments to settle claims incurred in prior periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437 + Details
Name: | us-gaap_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseClaimsPaidPriorYears1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of expense for claims incurred in prior reporting periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-18) -URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e575016-122915 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 18 -Article 12 + Details
Name: | us-gaap_SupplementalInformationForPropertyCasualtyInsuranceUnderwritersPriorYearClaimsAndClaimsAdjustmentExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_LiabilityForCatastropheClaimsByCatastrophicEventAxis=sigi_ChangeinHistoricalClaimRateExperienceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |