UNUSED LINES OF CREDIT (Details) (USD $)	6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012
Line of Credit Facility [Line Items]
Total facility	$ 660,000,000
Usage	323,300,000
Available liquidity	336,700,000
Letters of credit outstanding	27,600,000
Weighted average borrowing cost	0.98%		0.95%
Average borrowings outstanding during the period	275,300,000		376,200,000
Maximum amounts outstanding during the period	369,500,000		462,200,000
Financial covenant, ratio of indebtedness to consolidated total capitalization	0.65 to 1
Minimum [Member]
Line of Credit Facility [Line Items]
Financial covenant, ratio of indebtedness to consolidated total capitalization minimum	0.65
SJG 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
South Jersey Gas Company [Member]
Line of Credit Facility [Line Items]
Total facility	210,000,000
Usage	93,000,000
Available liquidity	117,000,000
South Jersey Gas Company [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Total facility	200,000,000
Usage	93,000,000
Available liquidity	107,000,000
Expiration date	May 2015
South Jersey Gas Company [Member] | Uncommitted Bank Lines [Member]
Line of Credit Facility [Line Items]
Total facility	10,000,000	[1]
Usage	0	[1]
Available liquidity	10,000,000	[1]
Expiration date	August 2013	[1]
South Jersey Industries Inc [Member]
Line of Credit Facility [Line Items]
Total facility	450,000,000
Usage	230,300,000
Available liquidity	219,700,000
South Jersey Industries Inc [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Total facility	400,000,000	[2]
Usage	180,300,000	[2]
Available liquidity	219,700,000	[2]
Expiration date	February 2018 (A)	[2]
South Jersey Industries Inc [Member] | Term Line of Credit [Member]
Line of Credit Facility [Line Items]
Total facility	50,000,000
Usage	50,000,000
Available liquidity	$ 0
Expiration date	November 2013

[1] Although there can be no assurances, SJG anticipates renewing the remaining line of credit during the third quarter 2013.

[2] Includes letters of credit outstanding in the amount of $27.6 million.