SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2013
Quarterly Financial Information Disclosure [Abstract]
Operating revenues		$ 438,306	$ 458,467	$ 1,013,090	$ 824,124	$ 591,914	$ 688,257	$ 1,579,569	$ 878,405	$ 2,733,987		$ 3,738,145		$ 3,198,068
Gross margin	[1]	82,177	51,217	145,189	225,787	47,375	28,474	315,849	64,432
Operating income (loss)		6,257	(9,309)	82,806	168,697	(28,838)	(29,208)	247,012	12,224	248,451		201,190		159,231
Net income (loss)		$ 4,197	$ (7,460)	$ 60,903	$ 123,320	$ (24,420)	$ (14,274)	$ 172,971	$ 7,693	$ 180,960		$ 141,970		$ 114,809
Earnings (loss) per share
Basic (in usd per share)		$ 0.05	$ (0.09)	$ 0.71	$ 1.46	$ (0.29)	$ (0.17)	$ 2.06	$ 0.09	$ 2.12		$ 1.69		$ 1.38
Diluted (in usd per share)		$ 0.05	$ (0.09)	$ 0.71	$ 1.44	$ (0.29)	$ (0.17)	$ 2.04	$ 0.09	$ 2.10	[2]	$ 1.67	[2]	$ 1.37	[2]

[1] Gross margin consists of operating revenue less cost of goods sold and other direct expenses at NJR's unregulated subsidiaries and utility gross margin at NJNG, which includes natural gas revenues less natural gas purchases, sales tax, a TEFA (which was phased out in January 2014) and regulatory rider expenses.

[2] There were no anti-dilutive shares excluded from the calculation of diluted earnings per share for fiscal 2015, 2014 and 2013.