AFFILIATIONS, DISCONTINUED OPERATIONS AND RELATED PARTY TRANSACTIONS - Related Party Transactions (Details) - SJG - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating Revenues/Affiliates:
Total Operating Revenue/Affiliates	$ 1,303	$ 1,063	$ 3,703	$ 5,691
Operations Expense/Affiliates:
Total Operations Expense/Affiliates	4,860	5,287	17,238	16,446
SJRG
Operating Revenues/Affiliates:
Total Operating Revenue/Affiliates	1,210	977	3,421	5,399
Costs of Sales/Affiliates (Excluding depreciation)	1,453	490	12,399	9,993
Marina
Operating Revenues/Affiliates:
Total Operating Revenue/Affiliates	72	65	219	229
SJI
Operations Expense/Affiliates:
Total Operations Expense/Affiliates	4,316	4,632	15,354	14,502
Millennium
Operations Expense/Affiliates:
Total Operations Expense/Affiliates	717	703	2,137	2,098
Other
Operating Revenues/Affiliates:
Total Operating Revenue/Affiliates	21	21	63	63
Operations Expense/Affiliates:
Total Operations Expense/Affiliates	$ (173)	$ (48)	$ (253)	$ (154)