FINANCIAL INSTRUMENTS (Details)	1 Months Ended	3 Months Ended			12 Months Ended
	Jun. 30, 2015 USD ($) term	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($) term	Dec. 31, 2016 USD ($) counterparty	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity investment impairments					$ 0		$ 0
Investment in Affiliate					$ 28,906,000	$ 16,983,000
Number of counterparties | counterparty					3
Carrying amount of long-term debt, including current maturities					$ 1,047,482,000	1,035,848,000
Unamortized debt issuance costs					7,600,000	9,000,000
Derivatives-Energy Related Assets | Supplier concentration risk
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current and noncurrent derivatives					$ 9,300,000
Percentage of current and noncurrent derivatives					11.50%
Atlantic City Note Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amount of advance	$ 10,000,000			$ 10,000,000
Interest rate of advance	1.00%
Term of loans	6 months
Number of additional terms | term	2			2
Extension term	3 months
Energenic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity interest								50.00%
Contract term								20 years
Equity investment impairments				$ 7,700,000		7,700,000
Share of settlement					$ 7,500,000
Associated costs					7,000,000
Investment in Affiliate					600,000
Notes receivable due from Affiliate					$ 13,600,000
Energenic | Other Income
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds received			$ 2,100,000
Energenic | Equity in Earnings of Affiliated Companies
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds received		$ 5,300,000
Marina Energy LLC | Energenic
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity interest							50.00%
ACB Energy Partners, LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Debt service reserve						1,700,000
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
Level 1
Accounts, Notes, Loans and Financing Receivable [Line Items]
Margin accounts with selected counterparties to support risk management activities					$ 11,700,000	43,700,000
Level 1 | Marina Energy LLC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Restricted investments held in escrow					1,900,000	3,400,000
Level 2
Accounts, Notes, Loans and Financing Receivable [Line Items]
Fair value of long-term debt, including current maturities					1,080,800,000	1,079,000,000
Carrying amount of long-term debt, including current maturities					1,039,900,000	1,026,900,000
Level 2 | South Jersey Gas Company | Financing receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Long-term receivables, net of unamortized discount					9,500,000	12,900,000
Imputed interest on long term receivables					$ 900,000	$ 1,300,000