v3.26.1
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - ADDITIONAL INFORMATION (Details)
$ in Thousands
 1 Months Ended 3 Months Ended 6 Months Ended
Aug. 31, 2025
USD ($)
Mar. 31, 2026
USD ($)
Mar. 31, 2025
USD ($)
Mar. 31, 2026
USD ($)
Megawatt
Mar. 31, 2025
USD ($)
Sep. 30, 2025
USD ($)
Finite-Lived Intangible Assets [Line Items]            
Operating revenues attributable to reportable segments   $ 939,401 $ 913,027 $ 1,544,255 $ 1,401,388  
Loans receivable in other noncurrent assets   82,900   82,900   $ 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 9,900 $ 9,900  
Deferred revenue   61,300   $ 61,300   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   $ 25,600   $ 25,600   $ 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