COMMON STOCK (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Common Stock, outstanding (in shares)		79,478,055	70,965,622	68,334,860	79,549,080	79,478,055
Par value of common stock (in USD per share)	$ 1.25				$ 1.25	$ 1.25
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning of Year (in shares)		79,478,055	70,965,622	68,334,860
New Issuances During Year:
Dividend Reinvestment Plan (in shares)		0	417,095	2,604,424
Stock-Based Compensation Plan (in shares)		71,025	45,338	26,338
Public Equity Offering (in shares)	8,050,000	0	8,050,000	0
End of Year (in shares)		79,549,080	79,478,055	70,965,622
Net excess over par value recorded in premium on common stock		$ 2,700
Proceeds from issuance of common stock	$ 203,600	$ 0	$ 214,426	$ 63,192
Incremental shares included in diluted earnings per share (in shares)		141,750	112,590	195,139
Dividend per share (in USD per share)		$ 1.099	$ 1.07	$ 1.02
Equity capital raised through Dividend Reinvestment Plan			$ 10,800
South Jersey Gas Company
Class of Stock [Line Items]
Dividends, Cash		$ 20,000	0	$ 40,800
Additional Investment by Shareholder		$ 40,000	$ 65,000	$ 0
Common Stock, outstanding (in shares)		2,339,139	2,339,139		2,339,139	2,339,139
Par value of common stock (in USD per share)					$ 2.50	$ 2.50
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning of Year (in shares)		2,339,139
New Issuances During Year:
End of Year (in shares)		2,339,139	2,339,139