RELATED PARTY TRANSACTIONS (Details) $ in Thousands		1 Months Ended		3 Months Ended		9 Months Ended
	Apr. 01, 2020 USD ($) Bcf	Jun. 30, 2022 USD ($)	Mar. 31, 2021	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) dth / d lease Bcf	Jun. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jul. 31, 2021
Related Party Transaction [Line Items]
Demand fees expense recognized pertaining to related party agreement				$ 1,838	$ 1,700	$ 5,567	$ 5,163
Demand fees payable		$ 855		855		$ 855		$ 861
Number of asset management agreements | lease						1
NJNG to NJRES Affiliate
Related Party Transaction [Line Items]
Asset management agreement, period	5 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 expense recognized pertaining to related party agreement				1,651	1,687	$ 5,015	4,760
Demand fees payable		775		775		775		778
NJRES to Steckman Ridge Affiliate
Related Party Transaction [Line Items]
Demand fees expense recognized pertaining to related party agreement				187	$ 13	552	$ 403
Demand fees payable		$ 80		$ 80		$ 80		$ 83
NJN G to Adelphia Affiliate
Related Party Transaction [Line Items]
Transportation precedent agreement term						5 years
Transportation capacity under precedent agreement with PennEast (in bcf per day) | dth / d						130,000
Leaf River Energy Center LLC
Related Party Transaction [Line Items]
Natural gas sold at cost under asset management agreement (in Bcf) | Bcf						3
Storage capacity agreement term						5 years
NJNG and Clean Energy Ventures to PPA
Related Party Transaction [Line Items]
Sublease agreement term		20 years	15 years
NJNG To NJR Subsidiaries
Related Party Transaction [Line Items]
Term of contract									16 years