FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Margin accounts with selected counterparties to support risk management activities	$ 7,600	$ 1,600
Cash and Cash Equivalents	10,360	30,030
Restricted Investments	7,649	1,649
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	18,009	31,679	$ 23,025	$ 39,695
Notes Receivable - Affiliate	13,275	13,275
Energenic US LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable - Affiliate	13,600
SJG Utility Operations
Accounts, Notes, Loans and Financing Receivable [Line Items]
Margin accounts with selected counterparties to support risk management activities	1,500	1,300
Cash and Cash Equivalents	1,756	1,984
Restricted Investments	1,468	1,278
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	3,224	3,262	$ 5,720	$ 4,619
SJG Utility Operations | Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount of loans, net of unamortized discounts	5,100	$ 5,300
Imputed interest of loans	$ 700
SJG Utility Operations | Financing Receivable | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Initial term of note	5 years
SJG Utility Operations | Financing Receivable | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Initial term of note	10 years