DERIVATIVE INSTRUMENTS - INCOME STATEMENT RELATED DISCLOSURES (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	$ (1,645)	$ 11,592	$ 22,347	$ 99,518
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	Nonutility
Amount of gain (loss) recognized in income on derivatives	$ 3,560	$ 12,648	$ 13,939	$ 29,894
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	Gas purchases - Utility and Nonutility
Amount of gain (loss) recognized in income on derivatives	$ 210	$ (5,914)	$ (1,800)	$ (6,708)
ES | Financial commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	(5,415)	4,858	10,208	76,332
NJNG
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	7,626	18,315	3,826	(79,876)
NJNG | Physical commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	188	315	(4,802)	(27,919)
NJNG | Financial commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivatives	$ 7,438	$ 18,000	$ 8,628	$ (51,957)