FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2017	Dec. 31, 2015	Dec. 31, 2011	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restricted investments held In escrow			$ 300			$ 1,900
Margin accounts with selected counterparties to support risk management activities			5,300			11,700
Cash and Cash Equivalents			13,681			18,282
Restricted Investments			5,645			13,628
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 50,740		19,326	$ 52,635		31,910
Notes Receivable - Affiliate			$ 13,275			13,275
Energenic US LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity interest			50.00%		50.00%
Contract term					20 years
Share of settlement				7,500
Recovery of costs receivable						7,000
Notes Receivable - Affiliate			$ 13,700
Energenic US LLC | Other Income
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recovery of costs associated with settlement		$ 2,100
Energenic US LLC | Equity in Earnings of Affiliated Companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Recovery of costs associated with settlement	5,300
South Jersey Gas Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Margin accounts with selected counterparties to support risk management activities			900			3,600
Cash and Cash Equivalents			404			1,359
Restricted Investments			891			32
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 9,499		1,295	$ 7,544		1,391
South Jersey Gas Company | Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount of loans, net of unamortized discounts			7,400			9,500
Imputed interest of loans			$ 800			$ 900
South Jersey Gas Company | Financing Receivable | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Initial term of note			5 years
South Jersey Gas Company | Financing Receivable | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Initial term of note			10 years