INCOME TAXES, DEFERRED TAX ASSETS AND LIABILITIES (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Sep. 30, 2014
Deferred tax assets
Investment tax credits	[1]	$ 24,770	$ 10,341
Deferred service contract revenue		3,440	3,299
Incentive compensation		10,369	14,632
Fair value of derivatives		0	14,350
State net operating losses		12,757	8,962
Conservation incentive plan		2,091	2,312
Underrecovered gas costs		2,827	0
Other		12,762	10,078
Total deferred tax assets		69,016	63,974
Deferred tax liabilities
Property related items		(440,420)	(371,017)
Remediation costs		(7,641)	(12,429)
Equity investments		(37,930)	(35,474)
Post employment benefits		(2,976)	(10,268)
Fair value of derivatives		(3,180)	0
Under-recovered gas costs		0	(5,056)
Other		(13,409)	(11,751)
Total deferred tax liabilities		(505,556)	(445,995)
Total net deferred tax liabilities		(436,540)	(382,021)
NJNG [Member]
Deferred tax assets
Investment tax credits		2,700	2,800
NJRCEV [Member]
Deferred tax liabilities
Tax credit carryforward		$ 22,100	$ 7,500

[1] Includes $2.7 million and $2.8 million for NJNG for fiscal 2015 and fiscal 2014, respectively, which is being amortized over the life of the related assets and $22.1 million and $7.5 million for NJRCEV for fiscal 2015 and fiscal 2014, respectively, which is ITC carryforward.