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Retirement Plan And Other Post-Retirement Benefits (Components Of Net Periodic Benefit Cost) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Mar. 31, 2025
Mar. 31, 2024
Retirement Plan        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost $ 1,023 $ 1,049 $ 2,046 $ 2,098
Interest Cost 9,223 10,890 18,446 21,779
Expected Return on Plan Assets (14,647) (17,086) (29,293) (34,172)
Amortization of Prior Service Cost (Credit) 76 91 151 181
Amortization of (Gains) Losses 1,620 (335) 3,240 (669)
Net Amortization and Deferral for Regulatory Purposes (Including Volumetric Adjustments) [1] (2,946) 4,057 (3,111) 8,116
Net Periodic Benefit Cost (Income) (5,651) (1,334) (8,521) (2,667)
Other Post-Retirement Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Service Cost 130 109 259 217
Interest Cost 3,625 3,890 7,251 7,780
Expected Return on Plan Assets (6,536) (6,660) (13,072) (13,321)
Amortization of Prior Service Cost (Credit) (107) (107) (214) (214)
Amortization of (Gains) Losses 9 (567) 18 (1,133)
Net Amortization and Deferral for Regulatory Purposes (Including Volumetric Adjustments) [1] (4,158) 1,769 (4,885) 4,008
Net Periodic Benefit Cost (Income) $ (7,037) $ (1,566) $ (10,643) $ (2,663)
[1] The Company’s policy is to record retirement plan and other post-retirement benefit costs in the Utility segment on a volumetric basis to reflect the fact that the Utility segment experiences higher throughput of natural gas in the winter months and lower throughput of natural gas in the summer months.