DERIVATIVE INSTRUMENTS - BALANCE SHEET RELATED DISCLOSURES (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Sep. 30, 2025
Fair Value
Derivative assets, current	$ 13,073	$ 12,514
Derivative liability, current	8,711	7,620
Derivative assets, noncurrent	1,278	2,319
Derivative liabilities, noncurrent	6,157	4,283
Physical commodity contracts
Fair Value
Derivative assets	4,400	5,051
Derivative liabilities	11,025	9,811
Financial commodity contracts
Fair Value
Derivative assets	9,951	9,782
Derivative liabilities	3,843	2,092
Not Designated as Hedging Instrument
Fair Value
Derivative assets	14,351	14,833
Derivative liabilities	14,868	11,903
NJNG | Not Designated as Hedging Instrument | Physical commodity contracts
Fair Value
Derivative assets, current	39	30
Derivative liability, current	104	2
NJNG | Not Designated as Hedging Instrument | Financial commodity contracts
Fair Value
Derivative assets, current	0	349
Derivative liability, current	12	4
Derivative assets, noncurrent	0	1
Derivative liabilities, noncurrent	0	0
ES | Not Designated as Hedging Instrument | Physical commodity contracts
Fair Value
Derivative assets, current	3,827	3,709
Derivative liability, current	5,154	5,878
Derivative assets, noncurrent	534	1,312
Derivative liabilities, noncurrent	5,767	3,931
ES | Not Designated as Hedging Instrument | Financial commodity contracts
Fair Value
Derivative assets, current	9,207	8,426
Derivative liability, current	3,441	1,736
Derivative assets, noncurrent	744	1,006
Derivative liabilities, noncurrent	$ 390	$ 352