LINES OF CREDIT (Details) - Line of Credit	3 Months Ended
	Mar. 31, 2016 USD ($) agreement	Mar. 31, 2015 USD ($)
Line of Credit Facility [Line Items]
Total Facility	$ 610,000,000
Usage	344,900,000
Available Liquidity	$ 265,100,000
Weighted average interest rate on borrowings (as a percent)	1.34%	0.88%
Average borrowings outstanding during the period	$ 394,600,000	$ 274,100,000
Maximum amounts outstanding during the period	$ 467,700,000	$ 329,400,000
Financial covenant, ratio of indebtedness to consolidated total capitalization (not more than)	0.65
SJG Commercial Paper Program
Line of Credit Facility [Line Items]
Total Facility	$ 200,000,000
Fixed maturities of notes, at maximum number of days (in days)	270 days
Letter of Credit Reimbursement Agreements [Member]
Line of Credit Facility [Line Items]
Letters of credit outstanding	$ 62,300,000
Number of reimbursement agreements | agreement	3
South Jersey Gas Company
Line of Credit Facility [Line Items]
Total Facility	$ 210,000,000
Usage	66,900,000
Available Liquidity	143,100,000
South Jersey Gas Company | Revolving Credit Facility
Line of Credit Facility [Line Items]
Total Facility	200,000,000
Usage	66,900,000
Available Liquidity	133,100,000
South Jersey Gas Company | Uncommitted Bank Lines
Line of Credit Facility [Line Items]
Total Facility	10,000,000
Usage	0
Available Liquidity	10,000,000
South Jersey Industries Inc
Line of Credit Facility [Line Items]
Total Facility	400,000,000
Usage	278,000,000
Available Liquidity	122,000,000
South Jersey Industries Inc | Revolving Credit Facility
Line of Credit Facility [Line Items]
Total Facility	400,000,000
Usage	278,000,000
Available Liquidity	122,000,000
Letters of credit outstanding	3,300,000
Marina Energy LLC | Letter of Credit Reimbursement Agreement 1
Line of Credit Facility [Line Items]
Letters of credit outstanding	16,400,000
Marina Energy LLC | Letter of Credit Reimbursement Agreement 2
Line of Credit Facility [Line Items]
Letters of credit outstanding	20,000,000
Marina Energy LLC | Letter of Credit Reimbursement Agreement 3
Line of Credit Facility [Line Items]
Letters of credit outstanding	$ 25,000,000