COMMITMENTS AND CONTINGENCIES (Details)	12 Months Ended		432 Months Ended
	Dec. 31, 2015 USD ($) site decatherm / day union	Dec. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) site decatherm / day union
Commitment and Contingencies [Line Items]
Minimum purchase amount under contract (in dts/d) | decatherm / day	626,500		626,500
Maximum purchase amount under contract (in dts/d) | decatherm / day	796,250		796,250
Minimum length of contract term	3 years
Maximum length of contract term	10 years
Accrual for pending litigation	$ 3,200,000	$ 2,900,000	$ 3,200,000
Collective bargaining agreements [Abstract]
Percentage of personnel represented by collective bargaining agreements	45.00%		45.00%
Number of unions for which entity has collect bargaining agreements with | union	2		2
Guarantees [Abstract]
Guarantor obligations	$ 79,300,000		$ 79,300,000
Standby letters of credit [Abstract]
Letter of credit provided	$ 610,000,000		$ 610,000,000
Environmental remediation costs [Abstract]
Number of sites for environmental cleanup (in number of sites) | site	12		12
Number of sites covered by insurance | site	11		11
Insurance policy limit	$ 50,000,000		$ 50,000,000
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning of Year	128,172,000	123,429,000
Accruals	19,489,000	18,533,000	377,200,000
Expenditures	(21,038,000)	(13,790,000)	(250,600,000)
End of Year	126,623,000	$ 128,172,000	126,623,000
Standby letters of credit [Member]
Standby letters of credit [Abstract]
Letter of credit provided	8,100,000.0		8,100,000.0
Standby Letter of Credit, Variable-rate Demand Bonds [Member]
Standby letters of credit [Abstract]
Letter of credit provided	87,500,000.0		87,500,000.0
Environmental Restoration Costs [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Minimum amount of future clean up costs	123,200,000		123,200,000
Maximum amount of future clean up costs	204,700,000		204,700,000
Minimum amount of future clean up costs assumed by another entity	2,800,000		2,800,000
Maximum amount of future clean up costs assumed by another entity	4,200,000		4,200,000
Environmental Restoration Costs [Member] | Fuel Oil [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Minimum amount of future clean up costs	600,000		600,000
Maximum amount of future clean up costs	$ 1,300,000		$ 1,300,000
Number of sites affected by environmental remediation | site	6		6
Environmental Restoration Costs [Member] | Sites Comprising the Majority the Environmental Remediation [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Minimum amount of future clean up costs	$ 110,500,000		$ 110,500,000
Maximum amount of future clean up costs	$ 190,500,000		$ 190,500,000
Number of sites affected by environmental remediation | site	6		6
Parental Guarantee [Member]
Guarantees [Abstract]
Contract term	2 years
Capital contribution obligation [Abstract]
Guaranteed amount	$ 5,200,000		$ 5,200,000
South Jersey Resources Group, LLC [Member]
Commitment and Contingencies [Line Items]
Amount of monthly fees paid to supplier	500,000
South Jersey Gas Company [Member]
Commitment and Contingencies [Line Items]
Amount of monthly fees paid to supplier	6,300,000
Standby letters of credit [Abstract]
Letter of credit provided	$ 210,000,000		$ 210,000,000