XML 165 R133.htm IDEA: XBRL DOCUMENT
v3.24.0.1

Commitments and Contingencies (Narrative) (Details) $ in Thousands | Dec. 31, 2023 USD ($)
--- | ---
Total contractually obligated investments |
Contractual Obligation | $ 413,800
Alternative and Other Investments |
Contractual Obligation | 254,300
Non-publicly traded collateralized loan obligations in our fixed income securities portfolio |
Contractual Obligation | 86,700
Non-publicly traded common stock within our equity portfolio |
Contractual Obligation | 40,000
Commercial Mortgage Loans SIGI |
Contractual Obligation | 800
Privately placed corporate securities |
Contractual Obligation | $ 32,000

X
- Definition Amount of contractual obligation, including, but not limited to, long-term debt, lease obligation, purchase obligation, and other commitments. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480678/235-10-S99-3 + Details
Name: | us-gaap_ContractualObligation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_InvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_OtherAggregatedInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CollateralizedLoanObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CommonStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=sigi_CommercialMortgageLoansSIGIMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=sigi_PrivatePlacementCorporateSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |