SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - ADDITIONAL INFORMATION (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Aug. 31, 2025 USD ($)	Dec. 31, 2025 USD ($) Megawatt	Dec. 31, 2024 USD ($)	Sep. 30, 2025 USD ($)
Finite-Lived Intangible Assets [Line Items]
Operating revenues attributable to reportable segments		$ 604,854	$ 488,361
Loans receivable in other noncurrent assets		74,300		$ 69,400
Proceeds from other financing activity	$ 42,500
ES
Finite-Lived Intangible Assets [Line Items]
Operating revenues attributable to reportable segments		4,900	$ 4,900
Deferred revenue		$ 66,200		36,800
ADI
Finite-Lived Intangible Assets [Line Items]
Number of megawatts | Megawatt		5
CSI
Finite-Lived Intangible Assets [Line Items]
Number of megawatts | Megawatt		5
Financial Asset, Not Past Due
Finite-Lived Intangible Assets [Line Items]
Loans receivable in other current assets		$ 22,700		$ 21,500
Minimum
Finite-Lived Intangible Assets [Line Items]
Loans receivable, term		5 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Loans receivable, term		10 years