COMMON STOCK (Details) - USD ($)		1 Months Ended	12 Months Ended
	Jan. 15, 2019	Apr. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2014
Class of Stock [Line Items]
Par value of common stock (in USD per share)						$ 1.25	$ 1.25
Net excess over par value recorded in premium on common stock			$ 133,600,000
Common stock, outstanding (in shares)			79,549,080	79,478,055	79,478,055	85,506,218	79,549,080	70,965,622
Quarterly contract adjustment payments on par value of preferred stock (in percentage)		3.55%
Dividend per share (in USD per share)			$ 1.13	$ 1.10	$ 1.07
Incremental shares included in diluted earnings per share (in shares)			141,750	777,603	112,590
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning of Year (in shares)			79,549,080	79,478,055
New Issuances During Year:
Dividend Reinvestment Plan (in shares)			0	0	417,095
Stock-Based Compensation Plan (in shares)			67,308	71,025	45,338
Public Equity Offering (in shares)			5,889,830	0	8,050,000
End of Year (in shares)			85,506,218	79,549,080	79,478,055
Series 2018A, Due 2031
Class of Stock [Line Items]
Stated interest rate		3.70%
Common Stock
Class of Stock [Line Items]
Par value of common stock (in USD per share)		$ 1.25
Stock issued in sale		12,669,491
Public offering price (in USD per share)		$ 29.50
Shares issued at closing (in shares)		5,889,830
Gross proceeds from shares		$ 173,700,000
Net proceeds from shares		$ 167,700,000
Capital Units
Class of Stock [Line Items]
Shares issued at closing (in shares)		5,750,000
Gross proceeds from shares		$ 287,500,000
Net proceeds from shares		$ 278,900,000
Par value of preferred shares (in USD per share)		$ 50
Capital Units | Series 2018A, Due 2031
Class of Stock [Line Items]
Undivided beneficial ownership interest		5.00%
Over-Allotment Option | Common Stock
Class of Stock [Line Items]
Shares issued at closing (in shares)		1,652,542
Over-Allotment Option | Capital Units
Class of Stock [Line Items]
Shares issued at closing (in shares)		750,000
South Jersey Gas Company
Class of Stock [Line Items]
Par value of common stock (in USD per share)						$ 2.50	$ 2.50
Common stock, outstanding (in shares)			2,339,139	2,339,139		2,339,139	2,339,139
Cash dividends paid			$ 0	$ 20,000,000	$ 0
Additional investment by shareholder			$ 0	$ 40,000,000	$ 65,000,000
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
Subsequent Event | Private Placement | Bank of America, N.A. | Common Stock
Class of Stock [Line Items]
Shares delivered to settle derivative	6,779,661