v3.26.1
Summary of Significant Accounting Policies (Schedule of Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Accumulated Other Comprehensive Income (Loss) [Roll Forward]        
Other Comprehensive Gains and Losses Before Reclassifications $ 51,060 $ 108,818 $ 85,408 $ (83,082)
Amounts Reclassified From Other Comprehensive Income (Loss) (42,595) (1,650) (16,610) (17,249)
Accumulated Other Comprehensive Income (Loss)        
Accumulated Other Comprehensive Income (Loss) [Roll Forward]        
Beginning balance 1,111 (222,975) (59,222) (15,476)
Ending balance 9,576 (115,807) 9,576 (115,807)
Gains and Losses on Derivative Financial Instruments        
Accumulated Other Comprehensive Income (Loss) [Roll Forward]        
Beginning balance 80,283 (151,700) 19,950 55,799
Other Comprehensive Gains and Losses Before Reclassifications 51,060 108,818 85,408 (83,082)
Amounts Reclassified From Other Comprehensive Income (Loss) (42,595) (1,650) (16,610) (17,249)
Ending balance 88,748 (44,532) 88,748 (44,532)
Funded Status of the Pension and Other Post-Retirement Benefit Plans        
Accumulated Other Comprehensive Income (Loss) [Roll Forward]        
Beginning balance (79,172) (71,275) (79,172) (71,275)
Other Comprehensive Gains and Losses Before Reclassifications 0 0 0 0
Amounts Reclassified From Other Comprehensive Income (Loss) 0 0 0 0
Ending balance $ (79,172) $ (71,275) $ (79,172) $ (71,275)