AFFILIATIONS, DISCONTINUED OPERATIONS AND RELATED PARTY TRANSACTIONS - Related Party Transactions (Details) - SJG - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating Revenues/Affiliates:
Total Operating Revenue/Affiliates	$ 1,334	$ 510	$ 2,400	$ 4,628
Operations Expense/Affiliates:
Total Operations Expense/Affiliates	5,659	5,967	12,378	11,159
SJRG
Operating Revenues/Affiliates:
Total Operating Revenue/Affiliates	1,248	421	2,211	4,422
Costs of Sales/Affiliates (Excluding depreciation)	496	1,514	10,946	9,503
Marina
Operating Revenues/Affiliates:
Total Operating Revenue/Affiliates	65	68	147	164
SJI
Operations Expense/Affiliates:
Total Operations Expense/Affiliates	4,988	5,315	11,038	9,870
Millennium
Operations Expense/Affiliates:
Total Operations Expense/Affiliates	712	701	1,420	1,395
Other
Operating Revenues/Affiliates:
Total Operating Revenue/Affiliates	21	21	42	42
Operations Expense/Affiliates:
Total Operations Expense/Affiliates	$ (41)	$ (49)	$ (80)	$ (106)