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Pension And Other Postretirement Benefit Plans (Components Of Company's Net Periodic Benefit Cost) (Details) - USD ($)
$ in Thousands
 3 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Pension Benefits [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Service cost $ 1,455 $ 1,311
Interest cost 2,481 2,434
Expected return on plan assets (3,694) (3,717)
Net amortization and deferral 902 815
Net periodic benefit cost 1,144 843
Other Postretirement Benefits [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Service cost 59 64
Interest cost 340 383
Expected return on plan assets (25) (22)
Net amortization and deferral (194) (71)
Net periodic benefit cost $ 180 $ 354