DERIVATIVE INSTRUMENTS - BALANCE SHEET RELATED DISCLOSURES (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Sep. 30, 2024
Fair Value
Derivative assets, current	$ 12,514	$ 6,813
Derivative liability, current	7,620	6,271
Derivative assets, noncurrent	2,319	806
Derivative liabilities, noncurrent	4,283	11,490
Not Designated as Hedging Instrument
Fair Value
Derivative assets	14,833	7,619
Derivative liabilities	11,903	17,761
ES | Not Designated as Hedging Instrument | Physical commodity contracts
Fair Value
Derivative assets, current	3,709	1,660
Derivative liability, current	5,878	4,346
Derivative assets, noncurrent	1,312	727
Derivative liabilities, noncurrent	3,931	10,758
ES | Not Designated as Hedging Instrument | Financial commodity contracts
Fair Value
Derivative assets, current	8,426	5,132
Derivative liability, current	1,736	1,344
Derivative assets, noncurrent	1,006	79
Derivative liabilities, noncurrent	352	732
NJNG | Not Designated as Hedging Instrument | Physical commodity contracts
Fair Value
Derivative assets, current	30	21
Derivative liability, current	2	579
NJNG | Not Designated as Hedging Instrument | Financial commodity contracts
Fair Value
Derivative assets, current	349	0
Derivative liability, current	4	2
Derivative assets, noncurrent	1	0
Derivative liabilities, noncurrent	$ 0	$ 0