Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2012	Feb. 15, 2013	Jun. 30, 2012
Entity Information [Line Items]
Entity Registrant Name	SOUTH JERSEY INDUSTRIES INC
Entity Central Index Key	0000091928
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		31,744,916
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 1,544,272,903