FINANCIAL INSTRUMENTS (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) counterparty	Dec. 31, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restricted Investments	$ 1,649	$ 31,876
Number of counterparties | counterparty	3
Carrying amount of long-term debt, including current maturities	$ 2,867,764	1,204,173
Unamortized debt issuance costs	27,000	17,400
Derivatives-Energy Related Assets | Supplier concentration risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current and noncurrent derivatives	$ 11,700
Percentage of current and noncurrent derivatives	19.10%
Energenic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable due from Affiliate	$ 13,600
Marina
Accounts, Notes, Loans and Financing Receivable [Line Items]
Margin accounts with selected counterparties to support risk management activities		300
South Jersey Gas Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Margin accounts with selected counterparties to support risk management activities		7,900
Restricted Investments	1,278	2,912
Carrying amount of long-term debt, including current maturities	900,264	829,173
Unamortized debt issuance costs	$ 6,800	7,300
South Jersey Gas Company | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term of loans	5 years
South Jersey Gas Company | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term of loans	10 years
South Jersey Gas Company | Unnamed Counterparty
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restricted Investments	$ 1,300	2,900
Level 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Margin accounts with selected counterparties to support risk management activities	1,600	31,600
Level 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value of long-term debt, including current maturities	2,910,000	1,220,000
Carrying amount of long-term debt, including current maturities	2,840,000	1,190,000
Level 2 | South Jersey Gas Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value of long-term debt, including current maturities	895,100	838,500
Carrying amount of long-term debt, including current maturities	893,400	821,900
Level 2 | South Jersey Gas Company | Financing receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Long-term receivables, net of unamortized discount	5,300	7,000
Imputed interest on long term receivables	$ (700)	$ (700)