DERIVATIVE INSTRUMENTS - BALANCE SHEET RELATED DISCLOSURES (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Fair Value
Derivative assets, current	$ 6,020	$ 6,813
Derivative liability, current	19,985	6,271
Derivative assets, noncurrent	28,851	806
Derivative liabilities, noncurrent	3,511	11,490
Not Designated as Hedging Instrument
Fair Value
Derivative assets	34,871	7,619
Derivative liabilities	23,496	17,761
NJNG | Not Designated as Hedging Instrument | Physical commodity contracts
Fair Value
Derivative assets, current	88	21
Derivative liability, current	41	579
NJNG | Not Designated as Hedging Instrument | Financial commodity contracts
Fair Value
Derivative assets, current	61	0
Derivative liability, current	0	2
ES | Not Designated as Hedging Instrument | Physical commodity contracts
Fair Value
Derivative assets, current	2,081	1,660
Derivative liability, current	7,585	4,346
Derivative assets, noncurrent	27,839	727
Derivative liabilities, noncurrent	2,858	10,758
ES | Not Designated as Hedging Instrument | Financial commodity contracts
Fair Value
Derivative assets, current	3,790	5,132
Derivative liability, current	12,359	1,344
Derivative assets, noncurrent	1,012	79
Derivative liabilities, noncurrent	$ 653	$ 732