RELATED PARTY TRANSACTIONS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Operating Revenues [Abstract]
Operating Revenues	$ 523		$ 348		$ 982		$ 6,891
Operating Expenses [Abstract]
Operating Expenses	4,174		3,658		13,235		12,440
South Jersey Resource Group [Member]
Operating Revenues [Abstract]
Operating Revenues	211		238		483		6,297
Cost of Sales	2,683		12,608		8,445		32,115
Energy-Related Derivative Losses	3,011	[1]	2,404	[1]	13,666	[1]	9,458	[1]
SJI [Member]
Operating Expenses [Abstract]
Operating Expenses	2,237		1,820		7,400		7,028
SJIS [Member]
Operating Expenses [Abstract]
Operating Expenses	1,240		1,182		3,833		3,455
Millennium [Member]
Operating Expenses [Abstract]
Operating Expenses	796		771		2,379		2,273
Other [Member]
Operating Revenues [Abstract]
Operating Revenues	312		110		499		594
Operating Expenses [Abstract]
Operating Expenses	$ (99)		$ (115)		$ (377)		$ (316)

[1] Contracts used to hedge natural gas purchases. Included in Cost of Sales on the Condensed Statement of Income.