COMMON STOCK (Details) - USD ($)		3 Months Ended	12 Months Ended
	Jan. 15, 2019	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
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			$ 184,600,000
Common stock, outstanding (in shares)			85,506,218	85,506,218	79,478,055	92,394,155	85,506,218
Shares issued at closing (in shares)			6,779,661	0	0
Stated interest rate						7.50%	7.50%
Quarterly contract adjustment payments on par value of preferred stock (in percentage)		3.55%
Incremental shares included in diluted earnings per share (in shares)			123,021	777,603	141,750
Dividend per share (in USD per share)			$ 1.16	$ 1.13	$ 1.10
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning of Year (in shares)			85,506,218	79,549,080	79,478,055
New Issuances During Year:
Settlement of Equity Forward Sale Agreement (in shares)			6,779,661	0	0
Stock-Based Compensation Plan (in shares)			108,276	67,308	71,025
Public Equity Offering (in shares)			0	5,889,830	0
End of Year (in shares)			92,394,155	85,506,218	79,549,080
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 (in shares)		12,669,491
Public offering price (in USD per share)		$ 29.50
Shares issued at closing (in shares)		5,889,830
Net proceeds from shares	$ 189,000,000.0
New Issuances During Year:
Settlement of Equity Forward Sale Agreement (in shares)		5,889,830
Capital Units
Class of Stock [Line Items]
Shares issued at closing (in shares)		5,750,000
Par value of preferred shares (in USD per share)		$ 50				$ 50
New Issuances During Year:
Settlement of Equity Forward Sale Agreement (in shares)		5,750,000
Capital Units | Series 2018A, Due 2031
Class of Stock [Line Items]
Undivided beneficial ownership interest		5.00%
Private Placement | Bank of America, N.A. | Common Stock
Class of Stock [Line Items]
Number of shares held for forward contract (in shares)	6,779,661
Over-Allotment Option | Capital Units
Class of Stock [Line Items]
Shares issued at closing (in shares)		750,000
New Issuances During Year:
Settlement of Equity Forward Sale Agreement (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
Dividend per share (in USD per share)			$ 0	$ 0	$ 8.55
Cash dividends paid			$ 0	$ 0	$ 20,000,000.0
Additional investment by shareholder			$ 0	$ 0	$ 40,000,000
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