LINES OF CREDIT (Details)	1 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) extension	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014
Line of Credit Facility [Line Items]
Total Facility	$ 50,000,000	$ 660,000,000
Usage		301,700,000
Available Liquidity		358,300,000
Letters of credit outstanding		$ 4,800,000
Number of extensions (not more than) | extension	2
Weighted average borrowing cost		1.47%	1.13%	0.83%
Average borrowings outstanding		$ 321,900,000	$ 335,000,000
Maximum amounts outstanding		$ 467,700,000	$ 471,100,000
Financial covenant, ratio of indebtedness to consolidated total capitalization (not more than)		0.65
Commercial Paper Program/Revolving Credit Facility
Line of Credit Facility [Line Items]
Term of agreement	364 days
Letters of credit
Line of Credit Facility [Line Items]
Total Facility		$ 4,800,000.0
South Jersey Gas commercial paper program
Line of Credit Facility [Line Items]
Total Facility		$ 200,000,000.0
Fixed maturities of notes, which may not exceed specified number of days		270 days
South Jersey Gas Company
Line of Credit Facility [Line Items]
Total Facility		$ 210,000,000
Usage		105,100,000
Available Liquidity		104,900,000
South Jersey Gas Company | Letters of credit
Line of Credit Facility [Line Items]
Letters of credit outstanding		800,000
South Jersey Gas Company | Commercial Paper Program/Revolving Credit Facility
Line of Credit Facility [Line Items]
Total Facility		200,000,000
Usage		105,100,000
Available Liquidity		94,900,000
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		450,000,000
Usage		196,600,000
Available Liquidity		253,400,000
South Jersey Industries Inc. | Commercial Paper Program/Revolving Credit Facility
Line of Credit Facility [Line Items]
Total Facility		450,000,000
Usage		196,600,000
Available Liquidity		$ 253,400,000