LINES OF CREDIT (Details)	1 Months Ended	3 Months Ended
	Jun. 30, 2019 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Apr. 30, 2020 USD ($)	Mar. 26, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 23, 2019 USD ($)
Line of Credit Facility [Line Items]
Notes payable		$ 697,300,000				$ 848,700,000
Line of Credit Facility, Maximum Amount Outstanding During Period		872,200,000	$ 404,800,000
SJG
Line of Credit Facility [Line Items]
Notes payable		142,500,000				$ 171,300,000
Line of Credit Facility, Maximum Amount Outstanding During Period		171,700,000	$ 108,000,000.0
Line of Credit
Line of Credit Facility [Line Items]
Usage		708,700,000
Total Facility		$ 1,210,000,000
Debt covenant, ratio of indebtedness to total capitalization, syndicate		0.70
Weighted average interest rate on borrowings		2.02%	3.46%
Average borrowings outstanding		$ 774,000,000.0	$ 241,900,000
Line of Credit | Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum aggregate letters of credit allowed		50,000,000.0
Line of Credit | SJG
Line of Credit Facility [Line Items]
Usage		143,300,000
Total Facility		$ 210,000,000
Weighted average interest rate on borrowings		1.76%	2.74%
Average borrowings outstanding		$ 152,500,000	$ 84,600,000
Debt covenant, ratio of indebtedness to total capitalization		0.65
Line of Credit | SJI
Line of Credit Facility [Line Items]
Usage		$ 469,300,000
Total Facility		800,000,000
Line of Credit | SJI | Line of Credit
Line of Credit Facility [Line Items]
Usage		169,300,000
Total Facility		500,000,000
Maximum aggregate letters of credit allowed		200,000,000.0
Increase in maximum aggregate facility subject to certain conditions	$ 100,000,000.0
Maximum aggregate facility, including increase subject to certain conditions		600,000,000.0
Line of Credit | SJI | Revolving Credit Facility
Line of Credit Facility [Line Items]
Usage		50,000,000
Term (in years)	5 years
Total Facility		50,000,000
Line of Credit | SJI | Swingline Loan
Line of Credit Facility [Line Items]
Additional aggregate borrowing capacity		50,000,000.0
Line of Credit | ETG/ELK | Revolving Credit Facility
Line of Credit Facility [Line Items]
Usage		96,100,000
Total Facility		200,000,000.0
Additional aggregate borrowing capacity		200,000,000.0
Line of Credit | ETG/ELK | Swingline Loan
Line of Credit Facility [Line Items]
Additional aggregate borrowing capacity		20,000,000.0
Line of Credit | ETG Utility Operations | Revolving Credit Facility
Line of Credit Facility [Line Items]
Total Facility		250,000,000.0
Additional aggregate borrowing capacity		190,000,000.0
Increase in maximum aggregate facility subject to certain conditions	$ 50,000,000.0
Line of Credit | ETG Utility Operations | Revolving Credit Facility | Subsequent event
Line of Credit Facility [Line Items]
Total Facility				$ 190,000,000.0
Line of Credit | ELK Utility Operations | Revolving Credit Facility
Line of Credit Facility [Line Items]
Additional aggregate borrowing capacity		10,000,000.0
Line of Credit | SJIU | Revolving Credit Facility | Subsequent event
Line of Credit Facility [Line Items]
Total Facility				$ 10,000,000.0
Commercial Paper and Letters of Credit | SJG | Revolving Credit Facility
Line of Credit Facility [Line Items]
Usage		143,300,000
Total Facility		200,000,000
Unsecured Debt | South Jersey Gas Commercial Paper Program
Line of Credit Facility [Line Items]
Total Facility		$ 200,000,000.0
Fixed maturities of notes, at maximum number of days		270 days
Unsecured Debt | SJI | Unsecured Term Loan
Line of Credit Facility [Line Items]
Usage		$ 100,000,000
Total Facility		100,000,000					$ 100,000,000.0
Unsecured Debt | SJI | Unsecured Term Loan
Line of Credit Facility [Line Items]
Usage		150,000,000
Total Facility		$ 150,000,000			$ 150,000,000.0