Document And Entity Information (USD $) In Thousands, except Share data	6 Months Ended
	Jun. 30, 2011	Aug. 01, 2011	Jun. 30, 2010
Entity Registrant Name	SOUTH JERSEY INDUSTRIES INC
Entity Central Index Key	0000091928
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Public Float			$ 1,277,133,181
Entity Common Stock, Shares Outstanding		30,034,646
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q2
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2011