v3.26.1
Retirement Plan and Other Post-Retirement Benefits (Tables)
 9 Months Ended
Jun. 30, 2026
Retirement Benefits [Abstract]  
Schedule of Components of Net Periodic Benefit Cost (Income) Components of Net Periodic Benefit Cost (in thousands):
 
 Retirement PlanOther Post-Retirement Benefits
Three Months Ended June 30,2026202520262025
Service Cost$861 $1,023 $105 $130 
Interest Cost8,944 9,223 3,836 3,625 
Expected Return on Plan Assets(14,710)(14,647)(7,374)(6,536)
Amortization of Prior Service Cost (Credit)63 76 (65)(107)
Amortization of (Gains) Losses2,421 1,620 152 9 
Net Amortization and Deferral for Regulatory Purposes (Including Volumetric Adjustments) (1)
152 85 131 (447)
Net Periodic Benefit Cost (Income)$(2,269)$(2,620)$(3,215)$(3,326)
 Retirement PlanOther Post-Retirement Benefits
Nine Months Ended June 30,2026202520262025
Service Cost$2,584 $3,069 $315 $389 
Interest Cost26,833 27,669 11,508 10,876 
Expected Return on Plan Assets(44,131)(43,940)(22,122)(19,608)
Amortization of Prior Service Cost (Credit)190 227 (195)(322)
Amortization of (Gains) Losses7,261 4,860 456 28 
Net Amortization and Deferral for Regulatory Purposes (Including Volumetric Adjustments) (1)
(2,825)(3,026)(3,578)(5,333)
Net Periodic Benefit Cost (Income)$(10,088)$(11,141)$(13,616)$(13,970)
(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.