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Federal Income Taxes Federal Income Tax (Federal Tax Net Operating Loss Carryforwards) (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014
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Operating Loss Carryforwards [Line Items] |
Annual Limitation Of Net Operating Loss Carryforwards | $ 1.9 sigi_AnnualLimitationOfNetOperatingLossCarryforwards
Operating Loss Carryforwards | 6,102 us-gaap_OperatingLossCarryforwards
Operating Loss Carryforwards Tax Effect | 2,136 sigi_OperatingLossCarryforwardsTaxEffect
Tax Year 2029 [Member] |
Operating Loss Carryforwards [Line Items] |
Operating Loss Carryforwards | 2,024 us-gaap_OperatingLossCarryforwards / us-gaap_TaxPeriodAxis = sigi_TaxYear2029Member
Operating Loss Carryforwards Tax Effect | 708 sigi_OperatingLossCarryforwardsTaxEffect / us-gaap_TaxPeriodAxis = sigi_TaxYear2029Member
Tax Year 2030 [Member] [Member] |
Operating Loss Carryforwards [Line Items] |
Operating Loss Carryforwards | 3,999 us-gaap_OperatingLossCarryforwards / us-gaap_TaxPeriodAxis = sigi_TaxYear2030MemberMember
Operating Loss Carryforwards Tax Effect | 1,400 sigi_OperatingLossCarryforwardsTaxEffect / us-gaap_TaxPeriodAxis = sigi_TaxYear2030MemberMember
Tax Year 2031 [Member] [Member] |
Operating Loss Carryforwards [Line Items] |
Operating Loss Carryforwards | 79 us-gaap_OperatingLossCarryforwards / us-gaap_TaxPeriodAxis = sigi_TaxYear2031MemberMember
Operating Loss Carryforwards Tax Effect | $ 28 sigi_OperatingLossCarryforwardsTaxEffect / us-gaap_TaxPeriodAxis = sigi_TaxYear2031MemberMember

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- Definition Amount of the annual limitation of operating loss carryforwards. + References No definition available. + Details
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- Definition Amount of operating loss carryforward, tax effects, available to reduce future taxable income under enacted tax laws. + References No definition available. + Details
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- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32559-109319 + Details
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