LEASES - ADDITIONAL INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2022	Jul. 31, 2021
Lessee, Lease, Description [Line Items]
ROU asset obtained in exchange for operating lease liability	$ 0	$ 87	$ 407	$ 911
Proceeds from sale leaseback transactions - natural gas meters			$ 8,441	17,300
ROU asset obtained in exchange for finance lease liability	$ 0	$ 0
Weighted average remaining lease term, operating lease	28 years 10 months 24 days		28 years 10 months 24 days		29 years 2 months 12 days
Operating lease, discount rate	3.20%		3.20%		3.20%
Weighted average remaining lease term, finance lease	3 years 6 months		3 years 6 months		4 years
NJNG
Lessee, Lease, Description [Line Items]
Proceeds from sale leaseback transactions - natural gas meters			$ 8,400	$ 17,300
Solar Property | Minimum
Lessee, Lease, Description [Line Items]
Term of contract	20 years		20 years
Renewal term	5 years		5 years
Solar Property | Maximum
Lessee, Lease, Description [Line Items]
Term of contract	50 years		50 years
Renewal term	20 years		20 years
Office Building
Lessee, Lease, Description [Line Items]
Term of contract						16 years
Office Building | Minimum
Lessee, Lease, Description [Line Items]
Term of contract	2 years		2 years
Office Building | Maximum
Lessee, Lease, Description [Line Items]
Term of contract	17 years		17 years
Meter License | Minimum
Lessee, Lease, Description [Line Items]
Term of contract	7 years		7 years
Meter License | Maximum
Lessee, Lease, Description [Line Items]
Term of contract	10 years		10 years
Equipment
Lessee, Lease, Description [Line Items]
Term of contract	8 years		8 years
Storage and Capacity
Lessee, Lease, Description [Line Items]
Term of contract	50 years		50 years