INCOME TAXES, DEFERRED TAX ASSETS AND LIABILITIES (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Sep. 30, 2012
Deferred tax assets
Investment tax credits	$ 43,033	$ 32,002
Deferred service contract revenue	3,231	3,185
Incentive compensation	6,798	7,666
State net operating losses	6,118	3,012
Other	5,718	5,881
Total deferred tax assets	64,898	51,746
Deferred tax liabilities
Property related items	(329,921)	(284,871)
Remediation costs	(18,881)	(24,018)
Equity investments	(33,368)	(31,610)
Post employment benefits	(17,455)	(8,520)
Fair value of derivatives	(6,258)	(5,461)
Conservation incentive plan	(7,611)	(11,200)
Under-recoverd gas costs	(383)	(2,835)
Other	(13,699)	(4,514)
Total deferred tax liabilities	(427,576)	(373,029)
Total net deferred tax liabilities	(362,678)	(321,283)
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	40,021
NJNG [Member]
Deferred tax assets
Investment tax credits	$ 3,012