Cover Page - USD ($)	12 Months Ended
	Dec. 31, 2021	Feb. 15, 2022	Jun. 30, 2021
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-6364
Entity Registrant Name	South Jersey Industries, Inc.
Entity Incorporation, State or Country Code	NJ
Entity Tax Identification Number	22-1901645
Entity Address, Address Line One	1 South Jersey Plaza
Entity Address, City or Town	Folsom
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	08037
City Area Code	(609)
Local Phone Number	561-9000
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 2,910,165,365
Entity Common Stock, Shares Outstanding		117,379,409
Documents Incorporated by Reference	In Part III of Form 10-K:  Portions of South Jersey Industries, Inc.'s definitive proxy statement for its 2022 annual meeting of shareholders to be filed with the Securities and Exchange Commission are incorporated by reference into Part III of this Form 10-K.
Entity Central Index Key	0000091928
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false
Common Stock - $1.25 par value per share
Entity Information [Line Items]
Title of 12(b) Security	Common Stock - $1.25 par value per share
Trading Symbol	SJI
Security Exchange Name	NYSE
5.625% Junior Subordinated Notes due 2079
Entity Information [Line Items]
Title of 12(b) Security	5.625% Junior Subordinated Notes due 2079
Trading Symbol	SJIJ
Security Exchange Name	NYSE
Corporate Units
Entity Information [Line Items]
Title of 12(b) Security	Corporate Units
Trading Symbol	SJIV
Security Exchange Name	NYSE
South Jersey Gas Company
Entity Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	000-22211
Entity Registrant Name	South Jersey Gas Co
Entity Incorporation, State or Country Code	NJ
Entity Tax Identification Number	21-0398330
Entity Address, Address Line One	1 South Jersey Plaza
Entity Address, City or Town	Folsom
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	08037
City Area Code	(609)
Local Phone Number	561-9000
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		2,339,139
Entity Central Index Key	0001035216
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false