DERIVATIVE INSTRUMENTS - BALANCE SHEET RELATED DISCLOSURES (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Sep. 30, 2025
Fair Value
Derivative assets, current	$ 9,530	$ 12,514
Derivative liability, current	8,117	7,620
Derivative assets, noncurrent	1,721	2,319
Derivative liabilities, noncurrent	5,267	4,283
Physical commodity contracts
Fair Value
Derivative assets	4,129	5,051
Derivative liabilities	9,224	9,811
Financial commodity contracts
Fair Value
Derivative assets	7,122	9,782
Derivative liabilities	4,160	2,092
Not Designated as Hedging Instrument
Fair Value
Derivative assets	11,251	14,833
Derivative liabilities	13,384	11,903
ES \| Not Designated as Hedging Instrument \| Physical commodity contracts
Fair Value
Derivative assets, current	2,981	3,709
Derivative liability, current	4,548	5,878
Derivative assets, noncurrent	1,068	1,312
Derivative liabilities, noncurrent	4,676	3,931
ES \| Not Designated as Hedging Instrument \| Financial commodity contracts
Fair Value
Derivative assets, current	6,469	8,426
Derivative liability, current	3,538	1,736
Derivative assets, noncurrent	653	1,006
Derivative liabilities, noncurrent	591	352
NJNG \| Not Designated as Hedging Instrument \| Physical commodity contracts
Fair Value
Derivative assets, current	80	30
Derivative liability, current	0	2
NJNG \| Not Designated as Hedging Instrument \| Financial commodity contracts
Fair Value
Derivative assets, current	0	349
Derivative liability, current	31	4
Derivative assets, noncurrent	0	1
Derivative liabilities, noncurrent	$ 0	$ 0

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