SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - ADDITIONAL INFORMATION (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2021 Megawatt	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Sep. 30, 2023 USD ($)
Finite-Lived Intangible Assets [Line Items]
Number of megawatts | Megawatt	5
Operating revenues		$ 275,636	$ 264,075	$ 1,400,759	$ 1,631,669
Loans receivable in other noncurrent assets		50,900		50,900		$ 39,000
Financial Asset, Not Past Due
Finite-Lived Intangible Assets [Line Items]
Loans receivable in other current assets		17,700		$ 17,700		15,100
Minimum
Finite-Lived Intangible Assets [Line Items]
Loans receivable, term				2 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Loans receivable, term				10 years
ES
Finite-Lived Intangible Assets [Line Items]
Operating revenues		9,500	$ 9,500	$ 28,500	$ 39,000
Deferred revenue		$ 97,700		$ 97,700		$ 58,700