SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	3 Months Ended
	Mar. 31, 2017 USD ($) county mi shares	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) shares
Accounting Policies [Abstract]
Number of counties in which SJG operates | county	7
Length of pipeline (in miles) | mi	100
Public utility assessment	$ 400,000	$ 400,000
Amount of costs related to interests in proved and unproved properties in Pennsylvania, net of amortization	$ 8,800,000		$ 8,800,000
Shares of treasury stock held (in shares) | shares	215,274		212,617
Goodwill	$ 4,838,000		$ 4,838,000
Public Utilities, General Disclosures [Line Items]
Cash Flows Provided by Operating Activities	79,528,000	98,465,000
Net Cash Flows from Financing Activities	(20,772,000)	(38,845,000)
Impairment charge	300,000	0
Identified impairments	0	0
South Jersey Gas Company
Public Utilities, General Disclosures [Line Items]
Cash Flows Provided by Operating Activities	56,986,000	68,838,000
Net Cash Flows from Financing Activities	6,679,000	(8,601,000)
Impairment charge	$ 0	0
Accounting Standards Update 2016-09, Statutory Tax Withholding Component
Public Utilities, General Disclosures [Line Items]
Cash Flows Provided by Operating Activities		400,000
Net Cash Flows from Financing Activities		$ (400,000)