RELATED PARTY TRANSACTIONS (Details) (USD $)	9 Months Ended						9 Months Ended	39 Months Ended		9 Months Ended				9 Months Ended
	Jun. 30, 2013 NJRES to Steckman RIdge and Iroquios Affliates [Member]	Jun. 30, 2012 NJRES to Steckman RIdge and Iroquios Affliates [Member]	Jun. 30, 2013 NJRES to Steckman Ridge Affiliate	Sep. 30, 2012 NJRES to Steckman Ridge Affiliate	Jun. 30, 2013 NJRES to Iroquois Affiliate [Member]	Sep. 30, 2012 NJRES to Iroquois Affiliate [Member]	Jun. 30, 2013 NJNG to Steckman RIdge Affiliate MMcf	Jun. 30, 2013 NJNG to Steckman RIdge Affiliate	Sep. 30, 2012 NJNG to Steckman RIdge Affiliate	Jun. 30, 2013 NJNG to Steckman RIdge and Iroquios Affiliates [Member]	Jun. 30, 2012 NJNG to Steckman RIdge and Iroquios Affiliates [Member]	Jun. 30, 2013 NJNG to Iroquois Affiliate [Member]	Sep. 30, 2012 NJNG to Iroquois Affiliate [Member]	Jun. 30, 2013 NJNG to NJRES Affiliate [Member] MMcf
Related Party Transaction [Line Items]
Demand fees expense recognized pertaining to related party agreement	$ 4,600,000	$ 5,000,000								$ 4,300,000	$ 3,900,000
Due to related parties			157,000	170,000	392,000	394,000	775,000	775,000	775,000			61,000	61,000
Related party agreement term								10 years
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