DERIVATIVE INSTRUMENTS - INCOME STATEMENT RELATED DISCLOSURES (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	$ 107,170	$ 9,400	$ (12,696)
ES | Physical commodity contracts | Operating revenues
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Nonutility	Nonutility	Nonutility
Amount of gain (loss) recognized in income on derivatives	$ 33,610	$ (8,569)	$ 30,011
ES | Physical commodity contracts | Natural gas purchases
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Gas purchases - Utility and Nonutility	Gas purchases - Utility and Nonutility	Gas purchases - Utility and Nonutility
Amount of gain (loss) recognized in income on derivatives	$ (6,846)	$ 3,580	$ 1,052
ES | Financial commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	80,406	14,403	(43,997)
ES | Foreign currency contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	0	(14)	238
NJNG
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	(84,371)	39,984	34,899
NJNG | Physical commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	(34,241)	7,116	2,174
NJNG | Financial commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	$ (50,130)	$ 32,868	$ 32,725