XML 71 R66.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Litigation (Narrative) (Details) | Sep. 30, 2012
--- | ---
Loss Contingency, Information about Litigation Matters [Abstract] |
Number of Insurance Subsidiaries | 10

X
- Definition The number of insurance subsidiaries of the entity. + References No definition available. + Details
Name: | sigi_NumberOfInsuranceSubsidiaries
Namespace Prefix: | sigi_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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