LEASES - ADDITIONAL INFORMATION (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Jul. 31, 2021
Lessee, Lease, Description [Line Items]
ROU asset obtained in exchange for operating lease liability	$ 13.2	$ 0.9
ROU asset obtained in exchange for finance lease liability	$ 8.4	$ 17.3
Weighted average remaining lease term, operating lease	29 years 2 months 12 days	29 years 2 months 12 days
Operating lease, discount rate	3.50%	3.20%
Weighted average remaining lease term, finance lease	3 years 3 months 18 days	4 years
Finance lease, discount rate	2.70%	2.70%
Solar Property | Minimum
Lessee, Lease, Description [Line Items]
Term of contract	20 years
Renewal term	5 years
Solar Property | Maximum
Lessee, Lease, Description [Line Items]
Term of contract	50 years
Renewal term	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
Office Building | Maximum
Lessee, Lease, Description [Line Items]
Term of contract	17 years
Meter License | Minimum
Lessee, Lease, Description [Line Items]
Term of contract	7 years
Meter License | Maximum
Lessee, Lease, Description [Line Items]
Term of contract	10 years
Equipment
Lessee, Lease, Description [Line Items]
Term of contract	8 years
Storage and Capacity
Lessee, Lease, Description [Line Items]
Term of contract	50 years