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, 2017
Mar. 31, 2016
Mar. 31, 2017
Mar. 31, 2016
Pension        
Net periodic benefit cost [Abstract]        
Service cost $ 2,138 $ 1,813 $ 4,276 $ 3,626
Interest cost 1,841 2,406 3,682 4,812
Expected return on plan assets (2,312) (2,407) (4,624) (4,814)
Amortization:        
Prior service cost (45) (46) (90) (92)
Net actuarial loss 2,509 1,866 5,018 3,732
Net benefit cost 4,131 3,632 8,262 7,264
Benefit plan contributions [Abstract]        
Supplemental retirement plan     0  
Additional contributions expected in fiscal 2017:     5,109  
Other Postretirement        
Net periodic benefit cost [Abstract]        
Service cost 98 101 196 202
Interest cost 157 211 314 422
Expected return on plan assets 0 0 0 0
Amortization:        
Prior service cost (49) (49) (98) (98)
Net actuarial loss 0 0 0 0
Net benefit cost $ 206 $ 263 412 $ 526
Benefit plan contributions [Abstract]        
Other postretirement plan     0  
Additional contributions expected in fiscal 2017:     692  
Supplemental retirement plan        
Benefit plan contributions [Abstract]        
Supplemental retirement plan     362  
Other postretirement plan     0  
Additional contributions expected in fiscal 2017:     398  
Other postretirement plan        
Benefit plan contributions [Abstract]        
Supplemental retirement plan     0  
Other postretirement plan     $ 456