Quarterly report pursuant to Section 13 or 15(d)

Pension and Other Postretirement Benefit Plans - Net Periodic Pension and Other Postretirement Benefit Cost (Details)

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Pension and Other Postretirement Benefit Plans - Net Periodic Pension and Other Postretirement Benefit Cost (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Amortization:        
Settlement losses     $ 0 $ (24,242)
Pension        
Net periodic benefit cost [Abstract]        
Service cost $ 30 $ 31 91 119
Interest cost 130 106 388 354
Amortization:        
Prior service credit 0 0 0 0
Net actuarial gains (13) (5) (33) (21)
Settlement losses     0 1,271
Net benefit cost 147 132 446 1,723
Other Postretirement        
Net periodic benefit cost [Abstract]        
Service cost 14 19 41 57
Interest cost 171 161 513 483
Amortization:        
Prior service credit (91) (92) (273) (274)
Net actuarial gains (180) (177) (541) (531)
Settlement losses     0 0
Net benefit cost $ (86) $ (89) $ (260) $ (265)