UNUSED LINES OF CREDIT (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Line of Credit Facility [Line Items]
Total Facility	$ 210,000,000
Usage	102,100,000
Available Liquidity	107,900,000
Reduction to bank lines	10,000,000
Average borrowings outstanding during the period	142,400,000	71,600,000
Maximum amounts outstanding during the period	180,500,000	139,900,000
Weighted average borrowing cost	0.48%	0.62%	0.71%
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Total Facility	200,000,000
Usage	102,100,000
Available Liquidity	97,900,000
Expiration Date	May 2015 (A)
Uncommitted Bank Lines [Member]
Line of Credit Facility [Line Items]
Total Facility	10,000,000
Usage	0
Available Liquidity	10,000,000
Expiration Date	Various
South Jersey Gas Commercial Paper Program [Member]
Line of Credit Facility [Line Items]
Total Facility	$ 200,000,000
Fixed maturities of notes, at maximum number of days (in days)	270 days
Minimum [Member]
Line of Credit Facility [Line Items]
Financial covenant, ratio of indebtedness to consolidated total capitalization minimum	0.65