Quarterly report pursuant to Section 13 or 15(d)

Pension and Other Postretirement Benefit Plans (Details)

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Pension and Other Postretirement Benefit Plans (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Mar. 31, 2020
Mar. 31, 2019
Pension        
Net periodic benefit cost [Abstract]        
Service cost $ 2,170 $ 2,000 $ 4,340 $ 4,000
Interest cost * 1,933 2,301 3,866 4,602
Expected return on plan assets * (2,232) (2,596) (4,464) (5,192)
Amortization:        
Prior service cost (47) (46) (94) (92)
Net actuarial loss (gain) * 2,386 1,100 4,773 2,161
Net benefit cost 4,210 2,759 8,421 5,479
Supplemental retirement plan        
Contributions during the six months ended March 31, 2020:        
Pension     382  
Additional contributions expected in fiscal 2020:        
Supplemental retirement plan 500   500  
Other Postretirement        
Net periodic benefit cost [Abstract]        
Service cost 64 61 128 122
Interest cost * 140 180 280 360
Expected return on plan assets * 0 0 0 0
Amortization:        
Prior service cost (23) (49) (46) (98)
Net actuarial loss (gain) * 0 (15) 0 (30)
Net benefit cost 181 $ 177 362 $ 354
Contributions during the six months ended March 31, 2020:        
Other Postretirement     457  
Additional contributions expected in fiscal 2020:        
Supplemental retirement plan $ 532   $ 532