AFFILIATIONS, DISCONTINUED OPERATIONS AND RELATED-PARTY TRANSACTIONS - RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
South Jersey Gas Company
Related Party Transaction [Line Items]
Total Operating Revenues/Affiliates	$ 6,283	$ 4,858	$ 7,319
Total Operations Expense/Affiliates	34,091	24,357	22,901
South Jersey Gas Company | SJRG
Related Party Transaction [Line Items]
Total Operating Revenues/Affiliates	5,813	4,458	6,934
Cost of Sales/Affiliates	33,313	24,337	16,306
South Jersey Gas Company | Marina
Related Party Transaction [Line Items]
Total Operating Revenues/Affiliates	379	314	302
South Jersey Gas Company | Other
Related Party Transaction [Line Items]
Total Operating Revenues/Affiliates	91	86	83
Total Operations Expense/Affiliates	(569)	(653)	(198)
South Jersey Gas Company | SJI
Related Party Transaction [Line Items]
Total Operations Expense/Affiliates	31,740	22,154	20,296
South Jersey Gas Company | Millennium
Related Party Transaction [Line Items]
Total Operations Expense/Affiliates	2,920	2,856	2,803
EnergyMark | SJRG
Related Party Transaction [Line Items]
Total Operating Revenues/Affiliates	$ 41,600	$ 37,500	$ 31,400