SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, RECEIVABLE BY SUBSIDIARY (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Sep. 30, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
Billed	$ 170,543		$ 209,266
Receivable by Susidiary Percentage	100.00%		100.00%
Unbilled revenues	7,017		7,333
NJRES [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Billed	135,891		155,594
Receivable by Susidiary Percentage	80.00%		74.00%
NJNG [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Billed	33,093	[1]	45,092	[1]
Receivable by Susidiary Percentage	19.00%	[1]	22.00%	[1]
NJRCEV [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Billed	154		69
Receivable by Susidiary Percentage	0.00%		0.00%
NJRHS and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Billed	$ 1,405		$ 8,511
Receivable by Susidiary Percentage	1.00%		4.00%

[1] Does not include unbilled revenues of $7 million and $7.3 million as of September 30, 2012 and 2011, respectively.