RELATED PARTY TRANSACTIONS (Details) (USD $)	3 Months Ended		9 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Related Party Transaction [Line Items]
Demand Fees	$ 49,900,000	$ 47,900,000	$ 159,900,000	$ 156,000,000
NJRES to Steckman Ridge Affiliate
Related Party Transaction [Line Items]
Demand Fees Expense Recognized by NJRES Pertaining to Related Party Agreement	354,000		494,000
Due to Related Parties	101,000		101,000
NJNG to NJRES Affilate [Member]
Related Party Transaction [Line Items]
Natural Gas Sold at Cost Under Asset Management Agreement (MMcf)			1,000
NJNG to Steckman RIdge Affiliate
Related Party Transaction [Line Items]
Agreement for Natural Gas Storage Capacity Between NJNG and Affiliate (MMcf)			3,000
Approximate Annual Demand Fees Under Agreement from April 1 2010 to March 31 2020			9,300,000
Demand Fees	2,300,000		6,900,000
Due to Related Parties	$ 775,000		$ 775,000