XML 151 R69.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Investments (Gross Credit Loss Impairments of Fixed Maturity Securities for Which a Portion of the OTTI Charge was Recognized in OCI) (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Investments [Abstract] |  |  |
Balance, beginning of year | $ 7,488 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld | $ 7,477 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld | $ 6,602 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld
Addition for the amount related to credit loss for which an OTTI was not previously recognized | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsNoPreviousImpairment | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsNoPreviousImpairment | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsNoPreviousImpairment
Reductions for securities sold during the period | (2,044)us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsSecuritiesSold | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsSecuritiesSold | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsSecuritiesSold
Reductions for securities for which the amount previously recognized in OCI was recognized in earnings because of intention or potential requirement to sell before recovery of amortized cost | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsChangeInStatus | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsChangeInStatus | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsChangeInStatus
Reductions for securities for which the entire amount previously recognized in OCI was recognized in earnings due to a decrease in cash flows expected | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsCashFlows | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsCashFlows | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsCashFlows
Additional increases to the amount related to credit loss for which an OTTI was previously recognized | 0 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses | 11 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses | 875 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses
Accretion of credit loss impairments previously recognized due to an increase in cash flows expected to be collected | 0 sigi_AccretionOfCreditLossImpairmentsPreviouslyRecognizedDueToIncreaseInCashFlowsExpectedToBeCollected | 0 sigi_AccretionOfCreditLossImpairmentsPreviouslyRecognizedDueToIncreaseInCashFlowsExpectedToBeCollected | 0 sigi_AccretionOfCreditLossImpairmentsPreviouslyRecognizedDueToIncreaseInCashFlowsExpectedToBeCollected
Balance, end of year | $ 5,444 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld | $ 7,488 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld | $ 7,477 us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld

X
- Definition This item represents accretion of credit loss impairments previously recognized due to an increase in cash flow expected to be collected on securities for which an other-than-temporary impairment charge was recognized in other comprehensive income. + References No definition available. + Details
Name: | sigi_AccretionOfCreditLossImpairmentsPreviouslyRecognizedDueToIncreaseInCashFlowsExpectedToBeCollected
Namespace Prefix: | sigi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_InvestmentsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which a previous OTTI was recognized and the investor does not intend to sell the debt security and it is not more likely than not that the investor will be required to sell the debt security before recovery of its amortized cost basis. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27340-111563 + Details
Name: | us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsAdditionalCreditLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which no such other than temporary impairment (OTTI) was previously recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27340-111563 + Details
Name: | us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsAdditionsNoPreviousImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27340-111563 + Details
Name: | us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsCreditLossesOnDebtSecuritiesHeld
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents reductions in the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held due to increases in cash flows expected to be collected and recognized over the remaining life of the security. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27340-111563 + Details
Name: | us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsCashFlows
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition This item represents reductions in the amount of cumulative losses recognized in earnings for other than temporary impairments (OTTI) for which a portion of the impairment had been recognized in other comprehensive income (a component of shareholders' equity) due to a change in status of the impaired security because of a change in the entity's intent to either sell the impaired security or it has become more likely than not that the entity will be required to sell the security before recovery of its cost basis. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27340-111563 + Details
Name: | us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsChangeInStatus
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition This item represents reductions in the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security because of the sale of impaired securities during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27340-111563 + Details
Name: | us-gaap_OtherThanTemporaryImpairmentCreditLossesRecognizedInEarningsReductionsSecuritiesSold
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration