RELATED PARTY TRANSACTIONS (Details) (USD $)	3 Months Ended						3 Months Ended		3 Months Ended				3 Months Ended
	Dec. 31, 2012 NJRES to Steckman RIdge and Iroquios Afffiliates [Member]	Dec. 31, 2011 NJRES to Steckman RIdge and Iroquios Afffiliates [Member]	Dec. 31, 2012 NJRES to Steckman Ridge Affiliate	Sep. 30, 2012 NJRES to Steckman Ridge Affiliate	Dec. 31, 2012 NJRES to Iroquois Affiliate [Member]	Sep. 30, 2012 NJRES to Iroquois Affiliate [Member]	Dec. 31, 2012 NJNG to Steckman RIdge Affiliate MMcf	Sep. 30, 2012 NJNG to Steckman RIdge Affiliate	Dec. 31, 2012 NJNG to Steckman RIdge and Iroquios Afffiliates [Member]	Dec. 31, 2011 NJNG to Steckman RIdge and Iroquios Afffiliates [Member]	Dec. 31, 2012 NJNG to Iroquois Affiliate [Member]	Sep. 30, 2012 NJNG to Iroquois Affiliate [Member]	Dec. 31, 2012 NJNG to NJRES Affilate [Member] MMcf
Related Party Transaction [Line Items]
Demand fees expense recognized pertaining to related party agreement	$ 1,600,000	$ 1,700,000							$ 1,400,000	$ 1,800,000
Due to related parties			210,000	170,000	403,000	394,000	775,000	775,000			121,000	61,000
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
Natural gas sold at cost under asset management agreement (MMcf)													1,000