UNUSED LINES OF CREDIT (Details) (USD $)	9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011
Line of Credit Facility [Line Items]
Total Facility	$ 210,000,000
Usage	137,900,000
Available Liquidity	72,100,000
Letters of credit outstanding	10,000,000
Average borrowings outstanding during the period	146,300,000		55,200,000
Maximum amounts outstanding during the period	180,500,000		111,400,000
Weighted average borrowing cost	0.47%		0.44%
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Total Facility	200,000,000
Usage	137,900,000
Available Liquidity	62,100,000
Expiration Date	May 2015
Uncommitted Bank Lines [Member]
Line of Credit Facility [Line Items]
Total Facility	10,000,000
Usage	0
Available Liquidity	10,000,000
Expiration Date	August 2013 (A)	[1]
South Jersey Gas Commerical 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
Minimum [Member]
Line of Credit Facility [Line Items]
Financial covenant, ratio of indebtedness to consolidated total capitalization minimum	0.65

[1] SJG reduced the uncommitted bank lines by $10.0 million during 2012. The SJG facilit