v3.26.3
Transactions with Controlled Companies - Valley Electric Company, Inc. (Details) - USD ($)
$ in Thousands
3 Months Ended
Jul. 01, 2026
Sep. 30, 2026
Sep. 30, 2025
Jun. 30, 2026
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]        
Interest Income   $ 132,608 $ 152,394  
Dividend Income   5,475 3,573  
Advisory Fee   10,605 1,299  
Total Other Income   13,658 1,657  
Realized Gain   (71,607) (1,891)  
Interest Receivable   23,039   $ 17,350
Reportable Legal Entities | Subsidiaries | Valley Electric Company, Inc.        
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]        
Interest Income   2,515 3,147  
Dividend Income   (1,083) 0  
Advisory Fee   9,840 0  
Royalty, net profit and revenue interests   0 167  
Total Other Income   9,840 167  
Repayment of Loan Receivable   95,912 0  
Interest Receivable   0   35
Other Receivables   (1)   $ 9
Reportable Legal Entities | Subsidiaries | Valley Electric Company, Inc. | Prospect Administration        
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]        
Managerial Assistance   0 150  
Reimbursement of Legal, Tax, etc   78 0  
Realized Gain   $ 131,821  
Reportable Legal Entities | Subsidiaries | Valley Electric Company, Inc.        
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]        
Ownership interest disposed percent 94.99% 94.99%    
Repayment of loan $ 280,779      
Prepayment premium for early repayment 2,516      
Proceeds from equity method investments 143,874      
Received cash at closing 40,655      
Advisory Fee 9,840      
Realized Gain 131,821      
Interest Receivable 35      
Reportable Legal Entities | Subsidiaries | Valley Electric Company, Inc. | First Lien Term Loan        
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]        
Repayment of loan 10,452      
Reportable Legal Entities | Subsidiaries | Valley Electric Company, Inc. | First Lien Term Loan B        
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]        
Repayment of loan 34,777      
Reportable Legal Entities | Subsidiaries | Valley Electric Company, Inc. | First Lien Term Loan Receivable        
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]        
Repayment of loan $ 38,630      
Reportable Legal Entities | Subsidiaries | Valley Electric Company, Inc. | Valley Electric Company, Inc.        
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]        
Interest Income   $ 2,202 2,825  
Reportable Legal Entities | Subsidiaries | Valley Electric Co. of Mt. Vernon, Inc. | Valley Electric Company, Inc.        
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]        
Interest Income   $ 313 $ 322