Annual report [Section 13 and 15(d), not S-K Item 405]

PENSION AND OTHER POSTRETIREMENT PLANS - Net Periodic Pension and Other Postretirement Benefit Cost (Details)

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PENSION AND OTHER POSTRETIREMENT PLANS - Net Periodic Pension and Other Postretirement Benefit Cost (Details) - USD ($)
$ in Thousands
 12 Months Ended
Sep. 30, 2025
Sep. 30, 2024
Sep. 30, 2023
Defined Benefit Plan Disclosure [Line Items]      
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration] Other income (deductions), net Other income (deductions), net Other income (deductions), net
Settlement $ 0 $ 0 $ (24,242)
Pension      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 142 125 163
Interest cost 493 530 497
Prior service cost (credit) 0 0 0
Net actuarial (gain) loss (41) (53) (64)
Settlement 0 0 1,271
Net benefit cost 594 602 1,867
Other Postretirement      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 52 55 76
Interest cost 608 684 644
Prior service cost (credit) (362) (364) (364)
Net actuarial (gain) loss (510) (722) (708)
Settlement 0 0 0
Net benefit cost $ (212) $ (347) $ (352)