UNUSED LINES OF CREDIT (Details) (USD $)	3 Months Ended				12 Months Ended	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Revolving Credit Facility [Member]	Mar. 31, 2013 Uncommitted Bank Lines [Member]	Dec. 31, 2012 South Jersey Gas Commercial Paper Program [Member]	Mar. 31, 2013 Minimum [Member]
Line of Credit Facility [Line Items]
Total Facility	$ 210,000,000		$ 200,000,000	$ 10,000,000	$ 200,000,000.0
Usage	70,600,000		67,000,000	3,600,000
Available Liquidity	139,400,000		133,000,000	6,400,000
Expiration Date			May 2015	August 2013
Financial covenant, ratio of indebtedness to consolidated total capitalization minimum						0.65
Fixed maturities of notes, at maximum number of days (in days)					270 days
Average borrowings outstanding during the period	86,200,000	139,500,000
Maximum amounts outstanding during the period	$ 103,000,000	$ 152,800,000
Weighted average borrowing cost	0.44%	0.46%