RELATED-PARTY TRANSACTIONS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Related Party Transaction [Line Items]
Operating Revenues/Affiliates	$ 1,063	$ 1,216	$ 5,691	$ 3,114
Total Operations Expense/Affiliates	5,287	3,848	16,446	12,265
SJRG
Related Party Transaction [Line Items]
Operating Revenues/Affiliates	977	1,100	5,399	2,631
Costs of Sales/Affiliates (Excluding depreciation)	490	574	9,993	21,105
Energy-Related Derivative Losses / (Gains)	0	0	0	65
Marina
Related Party Transaction [Line Items]
Operating Revenues/Affiliates	86	116	292	483
SJI
Related Party Transaction [Line Items]
Total Operations Expense/Affiliates	4,632	3,248	14,502	10,529
Millennium
Related Party Transaction [Line Items]
Total Operations Expense/Affiliates	703	695	2,098	2,048
Other
Related Party Transaction [Line Items]
Other	$ (48)	$ (95)	$ (154)	$ (312)