FINANCIAL INSTRUMENTS (Details)	1 Months Ended	3 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($) term	Mar. 31, 2016 USD ($)	Jun. 30, 2015 USD ($) term	Dec. 31, 2015 USD ($)	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restricted investments held In escrow		$ 3,200,000		$ 3,400,000
Margin accounts with selected counterparties to support risk management activities		34,700,000		43,700,000
Investment in Affiliates		20,254,000		16,983,000
Notes Receivable - Affiliate		13,275,000		13,275,000
Atlantic City Note Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Note receivable, face amount	$ 10,000,000		$ 10,000,000
Proceeds from collection of notes receivable		$ 100,000
Notes receivable, interest rate (as a percent)	1.00%
Notes receivable, term	6 months
Notes receivable, number of additional terms | term	2		2
Notes receivable, length of each additional term	3 months
Energenic US LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity interest (as percent)		50.00%
Contract term (in years)					20 years
Non-cash charge			$ 7,700,000
Loss from settlement				7,500,000
Investment in Affiliates		$ 1,400,000
Notes Receivable - Affiliate		13,700,000
ACB
Accounts, Notes, Loans and Financing Receivable [Line Items]
Escrow deposit		0		1,700,000
South Jersey Gas Company | Financing Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Long-term receivables, net of unamortized discount		12,200,000		12,900,000
Imputed interest on long term receivables		$ 1,200,000		$ 1,300,000
South Jersey Gas Company | Financing Receivable | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable, term		5 years
South Jersey Gas Company | Financing Receivable | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes receivable, term		10 years