RELATED PARTY TRANSACTIONS (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating Revenues [Abstract]
Operating Revenues	$ 1,735	$ 7,248	$ 6,708
Operating Expenses [Abstract]
Operating Expenses	18,916	17,525	16,462
SJRG [Member]
Operating Revenues [Abstract]
Operating Revenues	884	6,532	6,244
Cost of Sales	9,083	33,768	16,768
Energy-Related Derivative Losses	15,407	12,872	23,526
SJI [Member]
Operating Expenses [Abstract]
Operating Expenses	10,870	9,941	8,546
SJIS [Member]
Operating Expenses [Abstract]
Operating Expenses	5,397	4,956	5,174
Millennium [Member]
Operating Expenses [Abstract]
Operating Expenses	3,149	3,076	2,986
Other [Member]
Operating Revenues [Abstract]
Operating Revenues	851	716	464
Operating Expenses [Abstract]
Operating Expenses	$ (500)	$ (448)	$ (244)