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Name:	sigi_DefinedBenefitPlanAssetsTargetAllocationRangeMinimumAbstract
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The percentage of cash and the fair value of short-term investment securities to the fair value of total plan assets held as of the measurement date.

No definition available.

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Target allocation percentage of investments in alternative investments to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

No definition available.

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Target allocation maximum percentage of alternative investmenets to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

No definition available.

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Target allocation minimum percentage of alternative investments to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

No definition available.

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Target allocation maximum percentage of cash and short-term investments to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

No definition available.

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Target allocation minimum percentage of cash and investments in short-term investments to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

No definition available.

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Target allocation percentage of cash and investments in short-term investments to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

No definition available.

Name:	sigi_DefinedBenefitPlanTargetAllocationPercentageOfCashAndShortTermInvestments
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The maximum percentage of outstanding shares of any one corporation that is allowed for the Retirement Income Plan.

No definition available.

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The maximum percentage of any individual security value of the total Retirement Income Plan's portfolio value that is allowed.

No definition available.

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The percentage of the fair value of debt securities to the fair value of total plan assets held as of the measurement date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e2446-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Paragraph 1

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The percentage of the fair value of equity securities to the fair value of total plan assets held as of the measurement date.

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Target allocation percentage of investments in debt securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 5

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

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Target allocation maximum percentage of investments in debt securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

No definition available.

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Target allocation minimum percentage of investments in debt securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (c)(i)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e2446-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (d)(i)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

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Target allocation percentage of investments in equity securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

No definition available.

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Target allocation maximum percentage of investments in equity securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

No definition available.

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Target allocation minimum percentage of investments in equity securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

No definition available.

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The aggregate percentage of the fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of total plan assets held as of the measurement date.

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