v3.26.3
LONG-TERM DEBT - Narrative (Details) - USD ($)
$ in Thousands
9 Months Ended
Sep. 30, 2026
Apr. 21, 2026
Dec. 31, 2025
Jun. 18, 2025
Debt Instrument [Line Items]        
Long-term debt $ 2,859,974   $ 3,093,216  
2026 Credit Agreement | Commercial Paper        
Debt Instrument [Line Items]        
Available borrowing capacity 418,000      
Line of Credit | 2026 Credit Agreement        
Debt Instrument [Line Items]        
Maximum borrowing capacity   $ 650,000    
Swingline sublimit 150,000      
Letter of credit sublimit 150,000      
Available borrowing capacity 463,000      
Available borrowing capacity under letter of credit sublimit 145,000      
Line of Credit | Renewable Revolving Credit Agreement        
Debt Instrument [Line Items]        
Maximum borrowing capacity       $ 250,000
Available borrowing capacity 61,000      
Borrowings under line of credit $ 189,000      
Minimum        
Debt Instrument [Line Items]        
Equity to capitalization ratio (ECR) requirement (as a percent) 18.00%      
Debt service ratio (DSR) requirement 1.025      
Minimum | All Other Long-Term Debt        
Debt Instrument [Line Items]        
Debt service ratio (DSR) requirement 1.10      
Minimum | Springerville certificates, Series B, 7.14%, due through 2033 | Mortgages        
Debt Instrument [Line Items]        
Debt service ratio (DSR) requirement 1.02