RELATED PARTY TRANSACTIONS (Details) $ in Thousands		9 Months Ended
	Apr. 01, 2010 USD ($) Bcf	Jun. 30, 2016 USD ($) Bcf / d contract	Jun. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)
Related Party Transaction [Line Items]
Number of asset management agreements | contract		3
NJRES to Steckman Ridge Affiliate
Related Party Transaction [Line Items]
Demand fees expense recognized pertaining to related party agreement		$ 2,100	$ 1,300
Due to related parties		376		$ 375
NJNG to Steckman RIdge Affiliate
Related Party Transaction [Line Items]
Demand fees expense recognized pertaining to related party agreement		4,200	$ 4,300
Due to related parties		$ 775		$ 775
Related party agreement term	10 years
Natural gas sold at cost under asset management agreement (in Bcf) | Bcf	3
Approximate annual demand fees under agreement	$ 9,300
NJNG to PennEast Affiliate [Member]
Related Party Transaction [Line Items]
Transportation precedent agreement, period		15 years
Transportation capacity under precedent agreement from NJNG with PennEast (in bcf per day) | Bcf / d		0.18