Quarterly report [Sections 13 or 15(d)]

Debt - Outstanding Debt (Details)

v3.25.3
Debt - Outstanding Debt (Details) - USD ($)
$ in Thousands
9 Months Ended
Sep. 30, 2025
Aug. 31, 2025
Jul. 31, 2025
Dec. 31, 2024
Debt Instrument [Line Items]        
Units subject to mandatory redemption $ 3,399     $ 3,399
Total debt 3,391,194     3,282,860
Less: Short-term debt and current portion of long-term debt (41,814)     (51,732)
Long-term debt $ 3,349,380     3,231,128
Commercial notes, periodic interest and principal payments, 5.25%, expire May 1, 2026 | Commercial Paper        
Debt Instrument [Line Items]        
Interest rate 5.25%      
Premium financing notes $ 4,380     0
Commercial notes, periodic interest and principal payments, 5.25%, expire June 1, 2026 | Commercial Paper        
Debt Instrument [Line Items]        
Interest rate 5.25%      
Premium financing notes $ 794     0
Commercial notes, periodic interest and principal payments, 5.25%, expire June 21, 2026 | Commercial Paper        
Debt Instrument [Line Items]        
Interest rate 5.25%      
Premium financing notes $ 3,509     0
Commercial notes, periodic interest and principal payments, 6.25%, expired May 1, 2025 | Commercial Paper        
Debt Instrument [Line Items]        
Interest rate 6.25%      
Premium financing notes $ 0     2,673
Commercial notes, periodic interest and principal payments, 6.25%, expired June 1, 2025 | Commercial Paper        
Debt Instrument [Line Items]        
Interest rate 6.25%      
Premium financing notes $ 0     548
Commercial notes, periodic interest and principal payments, 6.25%, expired June 21, 2025 | Commercial Paper        
Debt Instrument [Line Items]        
Interest rate 6.25%      
Premium financing notes $ 0     $ 2,642
Medium-Term Note | Credit Agreement | Secured Debt        
Debt Instrument [Line Items]        
Debt term 7 years      
Interest rate 2.00% 2.00% 2.25% 2.25%
Long-term debt $ 1,662,865     $ 1,672,532
Senior Secured Notes | 8-year senior secured notes, semi-annual interest payments, 4.38%, mature February 1, 2030        
Debt Instrument [Line Items]        
Debt term 8 years      
Interest rate 4.38%      
Long-term debt $ 398,048     401,676
Senior Secured Notes | 8-year senior secured notes, semi-annual interest payments, 5.88%, mature August 1, 2032        
Debt Instrument [Line Items]        
Debt term 8 years      
Interest rate 5.88%      
Long-term debt $ 1,191,688     1,198,183
Line of Credit | Credit Agreement | Revolving Credit Facility        
Debt Instrument [Line Items]        
Debt term 5 years      
Basis spread on variable rate 2.50%      
Long-term debt $ 126,511     $ 1,207
Line of Credit | Credit Agreement | Revolving Credit Facility | Minimum        
Debt Instrument [Line Items]        
Commitment fee percentage 0.25%      
Line of Credit | Credit Agreement | Revolving Credit Facility | Maximum        
Debt Instrument [Line Items]        
Commitment fee percentage 0.50%