RELATED PARTY TRANSACTIONS (Details) $ in Thousands		12 Months Ended
	Apr. 01, 2010 USD ($) Bcf	Sep. 30, 2016 USD ($) Bcf / d contract	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Related Party Transaction [Line Items]
Demand fees recognized pertaining to related party agreement		$ 8,351	$ 7,657	$ 7,592
Due to related parties		$ 1,150	1,601
Number of asset management agreements | contract		3
NJNG to NJRES Affiliate
Related Party Transaction [Line Items]
Asset management agreement, period	10 years
NJNG to Steckman RIdge Affiliate
Related Party Transaction [Line Items]
Natural gas sold at cost under asset management agreement (in Bcf) | Bcf	3
Approximate annual demand fees under agreement	$ 9,300
Demand fees recognized pertaining to related party agreement		$ 5,562	5,700	5,918
Due to related parties		775	775
NJRES to Steckman Ridge Affiliate
Related Party Transaction [Line Items]
Demand fees recognized pertaining to related party agreement		2,789	1,957	$ 1,674
Due to related parties		$ 375	375
NJNG to PennEast Affiliate
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
NJNG And NJRES
Related Party Transaction [Line Items]
Due to related parties		$ 1,150	$ 1,150