UNUSED LINES OF CREDIT (Details) (USD $)	9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012
Line of Credit Facility [Line Items]
Total facility	$ 660,000,000
Usage	405,300,000
Available liquidity	254,700,000
Letters of credit outstanding	27,800,000
Weighted average borrowing cost	0.98%		0.97%
Average borrowings outstanding during the period	297,200,000		366,700,000
Maximum amounts outstanding during the period	389,400,000		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	110,000,000
Available liquidity	100,000,000
South Jersey Gas Company [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Total facility	200,000,000
Usage	110,000,000
Available liquidity	90,000,000
Expiration date	May 2018
South Jersey Gas Company [Member] | 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 2014
South Jersey Industries Inc [Member]
Line of Credit Facility [Line Items]
Total facility	450,000,000
Usage	295,300,000
Available liquidity	154,700,000
South Jersey Industries Inc [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Total facility	400,000,000	[1]
Usage	245,300,000	[1]
Available liquidity	154,700,000	[1]
Expiration date	February 2018 (A)	[1]
South Jersey Industries Inc [Member] | Term Line of Credit [Member]
Line of Credit Facility [Line Items]
Total facility	50,000,000	[2]
Usage	50,000,000	[2]
Available liquidity	$ 0	[2]
Expiration date	November 2015 (B)	[2]

[1] Includes letters of credit outstanding in the amount of $27.8 million.

[2] See Note 16 - Subsequent Events.