RELATED-PARTY TRANSACTIONS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Related Party Transaction [Line Items]
Operating Revenues/Affiliates	$ 447		$ 679		$ 1,466		$ 2,168
Operations Expense/Affiliates	3,477		4,629		11,734		14,555
SJRG
Related Party Transaction [Line Items]
Operating Revenues/Affiliates	169		344		552		1,194
Costs of Sales/Affiliates (Excluding depreciation)	1,686		5,436		8,612		11,105
Energy-Related Derivative (Gains) / Losses	(92)	[1]	389	[1]	(1,612)	[1]	568	[1]
Marina
Related Party Transaction [Line Items]
Operating Revenues/Affiliates	278		335		914		973
Other
Related Party Transaction [Line Items]
Operating Revenues/Affiliates	0		0		0		1
Operations Expense/Affiliates	(111)		(103)		(327)		(336)
SJI
Related Party Transaction [Line Items]
Operations Expense/Affiliates	2,901		2,737		10,079		8,613
SJIS
Related Party Transaction [Line Items]
Operations Expense/Affiliates	0	[2]	1,330	[2]	0	[2]	4,264	[2]
Millennium
Related Party Transaction [Line Items]
Operations Expense/Affiliates	$ 687		$ 665		$ 1,982		$ 2,014

[1] Contracts used to hedge natural gas purchases. Included in Cost of Sales on the Condensed Statement of Income.

[2] SJIS was dissolved effective January 1, 2014. All services previously provided by SJIS are currently being provided by SJI.