DERIVATIVE INSTRUMENTS - BALANCE SHEET RELATED DISCLOSURES (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Sep. 30, 2023
Fair Value
Derivative assets, current	$ 37,771	$ 30,755
Derivative liability, current	13,196	16,145
Derivative assets, noncurrent	1,178	1,564
Derivative liabilities, noncurrent	7,464	7,967
Not Designated as Hedging Instrument
Fair Value
Derivative assets	38,949	32,319
Derivative liabilities	20,660	24,112
NJNG | Not Designated as Hedging Instrument | Physical commodity contracts
Fair Value
Derivative assets, current	109	43
Derivative liability, current	749	488
NJNG | Not Designated as Hedging Instrument | Financial commodity contracts
Fair Value
Derivative assets, current	8,872	6,110
Derivative liability, current	421	20
ES | Not Designated as Hedging Instrument | Physical commodity contracts
Fair Value
Derivative assets, current	8,630	6,209
Derivative liability, current	8,929	12,757
Derivative assets, noncurrent	1,154	802
Derivative liabilities, noncurrent	7,086	7,870
ES | Not Designated as Hedging Instrument | Financial commodity contracts
Fair Value
Derivative assets, current	20,160	18,393
Derivative liability, current	3,097	2,880
Derivative assets, noncurrent	24	762
Derivative liabilities, noncurrent	$ 378	$ 97