SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2011
Quarterly Financial Information Disclosure [Abstract]
Operating revenues	$ 733,695		$ 767,469		$ 960,885		$ 736,019		$ 568,470		$ 425,121		$ 612,921		$ 642,411		$ 3,198,068		$ 2,248,923		$ 3,009,209
Gross margin	23,088	[1]	100,641	[1]	108,137	[1]	135,189	[1]	45,155	[1]	28,713	[1]	115,068	[1]	120,364	[1]
Operating income (loss)	(31,929)		47,000		56,969		87,191		(14,306)		(19,911)		67,689		75,218		159,231		108,690		143,001
Net income (loss)	$ (20,021)		$ 29,155		$ 45,469		$ 60,206		$ (8,693)		$ (10,320)		$ 54,535		$ 57,357		$ 114,809		$ 92,879		$ 101,299
Earnings (loss) per share
BASIC (in usd per share)	$ (0.48)		$ 0.70		$ 1.09		$ 1.44		$ (0.21)		$ (0.25)		$ 1.31		$ 1.38		$ 2.76		$ 2.24		$ 2.45
DILUTED (in usd per share)	$ (0.48)		$ 0.70		$ 1.08		$ 1.44		$ (0.21)		$ (0.25)		$ 1.31		$ 1.38		$ 2.75	[2]	$ 2.23	[2]	$ 2.44	[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 and regulatory rider expenses.

[2] There were no anti-dilutive shares excluded from the calculation of diluted earnings per share for fiscal 2013, 2012 and 2011.