SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - SOFTWARE COSTS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Mar. 31, 2025	Mar. 31, 2024	Sep. 30, 2024
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items]
Capitalized software costs	$ 10,664		$ 10,664		$ 10,522
Operation and maintenance
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items]
Software costs	1,151	$ 2,674	3,887	$ 5,927
Depreciation and amortization
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items]
Software costs	3,128	$ 1,265	5,543	$ 2,254
Utility plant, at cost
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items]
Software costs	133,330		133,330		133,158
Construction work in progress | Regulated
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items]
Software costs	50,580		50,580		26,659
Nonutility plant and equipment, at cost
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items]
Software costs	344		344		344
Accumulated depreciation and amortization, utility plant
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items]
Accumulated depreciation and amortization	(19,170)		(19,170)		(13,632)
Accumulated depreciation and amortization, nonutility plant and equipment
Oil and Gas, Full Cost Method, Capitalized Cost Excluded from Amortization [Line Items]
Accumulated depreciation and amortization	$ (53)		$ (53)		$ (48)