COMMITMENTS AND CONTINGENCIES (Details)		1 Months Ended	3 Months Ended			9 Months Ended
	May 08, 2017 USD ($)	May 31, 2017 USD ($)	Sep. 30, 2017 USD ($) site union decatherm / day contract	Jun. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) site union decatherm / day contract	Sep. 30, 2016 USD ($)	Aug. 31, 2017 USD ($)	Dec. 31, 2016 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			$ 140,598,000		$ 117,635,000	$ 503,715,000	$ 284,236,000
Interest Charges			10,567,000		7,355,000	38,291,000	24,744,000
Approximate amount accrued related to all claims			$ 3,000,000			$ 3,000,000			$ 3,100,000
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			$ 10,000,000			10,000,000
South Jersey Gas Company
Commitment and Contingencies [Line Items]
Cumulative obligation for demand charges and reservation fees per month						$ 6,100,000
Percentage of personnel represented by collective bargaining agreements			58.00%			58.00%
Interest Charges			$ 6,437,000		$ 4,058,000	$ 18,392,000	$ 13,397,000
Approximate amount accrued related to all claims			700,000			700,000			$ 600,000
South Jersey Gas Company | Pricing dispute, long-term gas supply contract | Judicial ruling
Commitment and Contingencies [Line Items]
Amount to be paid to supplier	$ 19,200,000
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		$ 200,000,000.0
Letters of credit outstanding			800,000			800,000
South Jersey Gas Company | Letters of credit under separate facility
Commitment and Contingencies [Line Items]
Letter of credit provided			$ 25,200,000			25,200,000
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			635,000			635,000
Maximum purchase commitment (in dts/d) | decatherm / day			1,029,000			1,029,000
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	$ 50,500,000
Cost of Sales - Nonutility			$ 5,500,000			$ 46,500,000
Interest Charges						4,000,000
South Jersey Resources Group | Dispute, long-term management contract | Pending litigation
Commitment and Contingencies [Line Items]
Amount to be paid to supplier				$ 9,500,000
Term of capacity management contract				3 years
Amount claimed to be owed				$ 13,300,000
Marina | Unsecured Debt
Commitment and Contingencies [Line Items]
Principal amount redeemed		$ 62,300,000
Parental guarantee
Commitment and Contingencies [Line Items]
Parental guarantees			$ 6,000,000			$ 6,000,000
Guarantee expiration period						2 years