Annual report pursuant to Section 13 and 15(d)

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, 2023
Sep. 30, 2022
Sep. 30, 2021
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
Non-cash charge (in excess of) $ (24,242) $ (35,706) $ 0
Pension      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 163 392 7,919
Interest cost 497 1,127 6,145
Expected return on plan assets 0 (1,040) (10,809)
Prior service cost 0 (152) (127)
Net actuarial loss (64) 469 9,769
Curtailment gain 0 0 (220)
Special termination benefits 0 0 315
Prior-service cost write-off 0 0 261
Non-cash charge (in excess of) 1,271 30,856 0
Net benefit cost 1,867 31,652 13,253
Other Postretirement      
Defined Benefit Plan Disclosure [Line Items]      
Service cost 76 165 201
Interest cost 644 411 376
Expected return on plan assets 0 0 0
Prior service cost (364) (364) (364)
Net actuarial loss (708) 0 0
Curtailment gain 0 0 0
Special termination benefits 0 0 0
Prior-service cost write-off 0 0 0
Non-cash charge (in excess of) 0 0 0
Net benefit cost $ (352) $ 212 $ 213