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 6 Months Ended
Mar. 31, 2024
Mar. 31, 2023
Mar. 31, 2024
Mar. 31, 2023
Amortization:        
Settlement losses     $ 0 $ (24,242)
Pension        
Net periodic benefit cost [Abstract]        
Service cost $ 31 $ 31 61 88
Interest cost 129 105 258 248
Amortization:        
Prior service credit 0 0 0 0
Net actuarial loss (gains) (9) (6) (20) (16)
Settlement losses     0 1,271
Net benefit cost 151 130 299 1,591
Other Postretirement        
Net periodic benefit cost [Abstract]        
Service cost 13 19 27 38
Interest cost 171 161 342 322
Amortization:        
Prior service credit (91) (91) (182) (182)
Net actuarial loss (gains) (181) (177) (361) (354)
Settlement losses     0 0
Net benefit cost $ (88) $ (88) $ (174) $ (176)