BUSINESS SEGMENT AND OTHER OPERATIONS DATA - NET FINANCIAL EARNINGS LOSS RECONCILIATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Net financial earnings (loss)	$ 39,860		$ 35,493
Unrealized loss (gain) from derivative instruments and related transactions	65,652	[1]	(18,334)	[1]
Effects of economic hedging related to natural gas inventory	(22,880)		(20,748)
Tax adjustments	(10,605)		14,369
NET INCOME	7,693		60,206
Transactions Between NJNG and NJRES [Member]
Unrealized losses related to intercompany transactions	$ 285		$ 67

[1] Excludes unrealized losses related to an intercompany transaction between NJNG and NJRES that have been eliminated in consolidation of approximately $285,000 and $67,000 for the three months ended December 31, 2013 and 2012, respectively.