RELATED PARTY TRANSACTIONS (Details) $ in Thousands		1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 01, 2020 USD ($) Bcf	Mar. 31, 2021	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2022 USD ($) dth / d lease Bcf	Mar. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jul. 31, 2021
Related Party Transaction [Line Items]
Demand fees expense recognized pertaining to related party agreement			$ 1,883	$ 1,731	$ 3,729	$ 3,464
Demand fees payable			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			1,546	1,505	$ 3,104	3,073
Demand fees payable			779		779		778
NJRES to Steckman Ridge Affiliate
Related Party Transaction [Line Items]
Demand fees expense recognized pertaining to related party agreement			337	$ 226	625	$ 391
Demand fees payable			$ 76		$ 76		$ 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		15 years
NJNG To NJR Subsidiaries
Related Party Transaction [Line Items]
Term of contract								16 years