COMMITMENTS AND CONTINGENCIES (Details)	3 Months Ended		15 Months Ended
	Mar. 31, 2018 USD ($) site union decatherm / day contract	Mar. 31, 2017 USD ($)	Mar. 31, 2018 USD ($) site union decatherm / day contract	Dec. 31, 2017 USD ($)
Commitment and Contingencies [Line Items]
Percentage of personnel represented by collective bargaining agreements	40.00%		40.00%
Number of unions | union	2		2
Cost of Sales - Nonutility	$ 195,951,000	$ 215,763,000
Interest Charges	13,972,000	16,745,000
Approximate amount accrued related to all claims	$ 3,100,000		$ 3,100,000	$ 3,000,000
Environmental restoration costs
Commitment and Contingencies [Line Items]
Number of sites for environmental cleanup | site	12		12
Pricing dispute, long-term gas supply contract
Commitment and Contingencies [Line Items]
Number of long-term gas supply contracts | contract	2		2
Line of Credit
Commitment and Contingencies [Line Items]
Letter of credit provided	$ 660,000,000		$ 660,000,000
Standby letters of credit
Commitment and Contingencies [Line Items]
Letter of credit provided	6,000,000		$ 6,000,000
South Jersey Gas Company
Commitment and Contingencies [Line Items]
Cumulative obligation for demand charges and reservation fees per month	$ 5,800,000
Percentage of personnel represented by collective bargaining agreements	57.00%		57.00%
Interest Charges	$ 6,728,000	$ 5,878,000
Approximate amount accrued related to all claims	800,000		$ 800,000	$ 700,000
South Jersey Gas Company | Pricing dispute, long-term gas supply contract | Judicial ruling
Commitment and Contingencies [Line Items]
Amount to be paid to supplier			20,600,000
South Jersey Gas Company | Line of Credit
Commitment and Contingencies [Line Items]
Letter of credit provided	210,000,000		210,000,000
South Jersey Gas Company | Syndicated Revolving Credit Facility | Line of Credit
Commitment and Contingencies [Line Items]
Letter of credit provided	200,000,000		200,000,000
Letters of credit outstanding	900,000		900,000
South Jersey Gas Company | Letters of credit under separate facility
Commitment and Contingencies [Line Items]
Letter of credit provided	25,100,000		$ 25,100,000
South Jersey Resources Group
Commitment and Contingencies [Line Items]
Cumulative obligation for demand charges and reservation fees per month	$ 500,000
Minimum purchase commitment (in dts/d) | decatherm / day	604,000		604,000
Maximum purchase commitment (in dts/d) | decatherm / day	954,000		954,000
Minimum length of contract	3 years
Maximum length of contract	10 years
South Jersey Resources Group | Pricing dispute, long-term gas supply contract | Judicial ruling
Commitment and Contingencies [Line Items]
Amount to be paid to supplier			$ 53,900,000
Cost of Sales - Nonutility	$ 100,000
Interest Charges	200,000
Parental guarantee
Commitment and Contingencies [Line Items]
Parental guarantees	$ 6,100,000		$ 6,100,000
Guarantee expiration period	2 years