SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)			3 Months Ended
	May. 08, 2015	Feb. 26, 2015 shares	Mar. 31, 2016 USD ($) county mi shares	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) shares	Feb. 25, 2015 shares
Accounting Policies [Abstract]
Debt Issuance Costs, Net			$ 8,400,000		$ 9,000,000
Number of counties in which SJG operates | county			7
Length of pipeline (in miles) | mi			100
Common stock, authorized (in shares) | shares		120,000,000				60,000,000
Stock split, conversion ratio	2	2
Amount of Transitional Energy Facility Assessment and Public Utilities Assessment included in revenues and cost of sales			$ 400,000	$ 600,000
Impairment charges			0	$ 0
Amount of costs related to interests in proved and unproved properties in Pennsylvania, net of amortization			$ 8,900,000		$ 8,900,000
Shares of treasury stock held (in shares) | shares			209,298		236,571
Goodwill			$ 8,139,000		$ 8,880,000