v3.25.2
Capitalization (Narrative) (Details)
$ / shares in Units, $ in Thousands
 9 Months Ended
Mar. 06, 2025
USD ($)
Feb. 19, 2025
USD ($)
Jun. 30, 2025
USD ($)
$ / shares
shares
Jun. 30, 2024
USD ($)
Jun. 13, 2025
USD ($)
May 31, 2025
lender
Jan. 30, 2025
Sep. 30, 2024
USD ($)
Apr. 30, 2024
USD ($)
Mar. 08, 2024
USD ($)
Feb. 14, 2024
USD ($)
lender
Debt Instrument [Line Items]                      
Stock repurchase program, authorized amount                   $ 200,000  
Share repurchases (in shares) | shares     650,037                
Current Portion of Long-Term Debt     $ 300,000         $ 500,000      
Net Proceeds from Issuance of Long-Term Debt     988,731 $ 299,396              
Premiums Paid on Early Redemption of Debt     (2,385) $ 0              
Unamortized Debt Expense     $ 6,701         5,604      
5.50% Notes Due March 15, 2030                      
Debt Instrument [Line Items]                      
Long-term debt, face amount   $ 500,000                  
Long-term debt, interest rate 5.50% 5.50%                  
Net Proceeds from Issuance of Long-Term Debt   $ 495,200                  
Percentage of principal amount   101.00%                  
Maximum interest rate adjustment   2.00%                  
5.50% Notes Due March 15, 2030 | Maximum                      
Debt Instrument [Line Items]                      
Long-term debt, interest rate   7.50%                  
5.95% Notes Due March 15, 2035                      
Debt Instrument [Line Items]                      
Long-term debt, face amount   $ 500,000                  
Long-term debt, interest rate   5.95%                  
Net Proceeds from Issuance of Long-Term Debt   $ 493,500                  
Percentage of principal amount   101.00%                  
Maximum interest rate adjustment   2.00%                  
5.95% Notes Due March 15, 2035 | Maximum                      
Debt Instrument [Line Items]                      
Long-term debt, interest rate   7.95%                  
5.50% Notes Due January 2026                      
Debt Instrument [Line Items]                      
Long-term debt, face amount $ 500,000                    
Long-term debt, interest rate 5.50%                    
Debt instrument redeemed $ 503,300                    
5.50% Notes Due January 2026 | Exploration and Production and Gathering                      
Debt Instrument [Line Items]                      
Premiums Paid on Early Redemption of Debt 1,800                    
5.50% Notes Due January 2026 | Pipeline and Storage                      
Debt Instrument [Line Items]                      
Unamortized Debt Expense 1,500                    
Indenture From 1974                      
Debt Instrument [Line Items]                      
Debt instrument redeemed         $ 50,000            
Carrying amount of long-term debt         $ 50,000            
Share Repurchase Plan                      
Debt Instrument [Line Items]                      
Share repurchases (in shares) | shares     828,720                
Share repurchase program, average cost per share (in dollars per share) | $ / shares     $ 64.37                
Share repurchases     $ 53,800                
Credit Agreement                      
Debt Instrument [Line Items]                      
Maximum borrowing capacity     $ 1,000,000                
Extended term of credit agreement             1 year        
Number of banks In syndicate | lender           12          
7.38% Notes Due June 2025                      
Debt Instrument [Line Items]                      
Current Portion of Long-Term Debt               $ 50,000      
Long-term debt, interest rate               7.38%      
7.38% Notes Due June 2025 | Indenture From 1974                      
Debt Instrument [Line Items]                      
Long-term debt, interest rate     7.38%   7.38%            
5.20% Notes Due July 2025                      
Debt Instrument [Line Items]                      
Current Portion of Long-Term Debt 450,000             $ 450,000      
Long-term debt, face amount $ 450,000                    
Long-term debt, interest rate 5.20%             5.20%      
Debt instrument redeemed $ 450,800                    
5.20% Notes Due July 2025 | Exploration and Production and Gathering                      
Debt Instrument [Line Items]                      
Premiums Paid on Early Redemption of Debt 600                    
5.20% Notes Due July 2025 | Pipeline and Storage                      
Debt Instrument [Line Items]                      
Unamortized Debt Expense $ 200                    
Term Loan Agreement                      
Debt Instrument [Line Items]                      
Maximum borrowing capacity                     $ 300,000
Current Portion of Long-Term Debt     $ 300,000                
Long-term debt, face amount                 $ 300,000    
Number of lenders | lender                     6
Proceeds from debt, net of issuance costs     $ 299,400                
Rate adjustment to SOFR     0.0010                
Spread on variable rate     1.375%                
Term Loan Agreement | 5.82% Through August 2025                      
Debt Instrument [Line Items]                      
Long-term debt, variable interest rate     5.82%