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 9 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Pension        
Net periodic benefit cost [Abstract]        
Service cost $ 2,039 $ 2,138 $ 6,117 $ 6,414
Interest cost 2,049 1,841 6,147 5,523
Expected return on plan assets (2,534) (2,312) (7,602) (6,936)
Amortization:        
Prior service cost (35) (45) (105) (135)
Net actuarial loss 1,753 2,509 5,257 7,527
Net benefit cost 3,272 4,131 9,814 12,393
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]        
Pension     10,000  
Other Postretirement     0  
Other Postretirement        
Net periodic benefit cost [Abstract]        
Service cost 84 98 252 294
Interest cost 158 157 474 471
Expected return on plan assets 0 0 0 0
Amortization:        
Prior service cost (49) (49) (147) (147)
Net actuarial loss 0 0 0 0
Net benefit cost 193 $ 206 579 $ 618
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]        
Other Postretirement     1,281  
Supplemental retirement plan        
Defined Benefit Plan, Expected Future Employer Contributions [Abstract]        
Pension     575  
Additional contributions expected in fiscal 2018: $ 191   $ 191