LINES OF CREDIT AND SHORT-TERM BORROWINGS (Details)	9 Months Ended
	Sep. 30, 2020 USD ($)	Mar. 26, 2020 USD ($)
Line of Credit
Line of Credit Facility [Line Items]
Total Facility	$ 1,060,000,000
Debt covenant, ratio of indebtedness to total capitalization, syndicate	0.70
Line of Credit | SJI
Line of Credit Facility [Line Items]
Total Facility	$ 650,000,000
Line of Credit | SJI | Line of Credit
Line of Credit Facility [Line Items]
Total Facility	500,000,000.0
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]
Term (in years)	5 years
Line of Credit | SJI | Swingline Loan
Line of Credit Facility [Line Items]
Additional aggregate borrowing capacity	$ 50,000,000.0
Line of Credit | SJIU and ETG
Line of Credit Facility [Line Items]
Debt covenant, ratio of indebtedness to total capitalization, syndicate	0.70
Line of Credit | SJIU and ETG | Revolving Credit Facility
Line of Credit Facility [Line Items]
Total Facility	$ 200,000,000.0
Additional aggregate borrowing capacity	200,000,000.0
Maximum aggregate letters of credit allowed	50,000,000.0
Increase in maximum aggregate facility subject to certain conditions	50,000,000.0
Maximum aggregate facility, including increase subject to certain conditions	250,000,000.0
Line of Credit | SJIU and ETG | Swingline Loan
Line of Credit Facility [Line Items]
Additional aggregate borrowing capacity	20,000,000.0
Unsecured promissory notes | 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 promissory notes | SJI | Unsecured Term Loan
Line of Credit Facility [Line Items]
Total Facility	$ 150,000,000	$ 150,000,000.0