XML 91 R79.htm IDEA: XBRL DOCUMENT v3.25.1

Litigation (Details)	Mar. 31, 2025 subsidiary
Commitments and Contingencies Disclosure [Abstract]
Number of insurance subsidiaries	10

X

- Definition

Number Of Insurance Subsidiaries

+ References

No definition available.

+ Details

Name:	sigi_NumberOfInsuranceSubsidiaries
Namespace Prefix:	sigi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- References

No definition available.

+ Details

Name:	us-gaap_CommitmentsAndContingenciesDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration