Cover Page - shares	6 Months Ended
	Jun. 30, 2024	Jul. 19, 2024
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2024
Document Transition Report	false
Entity File Number	001-33067
Entity Registrant Name	SELECTIVE INSURANCE GROUP, INC
Entity Incorporation, State or Country Code	NJ
Entity Tax Identification Number	22-2168890
Entity Address, Address Line One	40 Wantage Avenue
Entity Address, City or Town	Branchville
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	07890
City Area Code	(973)
Local Phone Number	948-3000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		60,833,139
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
Entity Central Index Key	0000230557
Current Fiscal Year End Date	--12-31
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, par value $2 per share
Trading Symbol	SIGI
Security Exchange Name	NASDAQ
Depositary Shares
Document Information [Line Items]
Title of 12(b) Security	Depositary Shares, each representing a 1/1,000th interest in a share of 4.60% Non-Cumulative Preferred Stock, Series B, without par value
Trading Symbol	SIGIP
Security Exchange Name	NASDAQ