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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 9 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Pension Benefits [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 1,433 $ 1,314 $ 4,340 $ 3,943
Interest cost 2,503 2,436 7,469 7,309
Expected return on plan assets (3,693) (3,717) (11,081) (11,151)
Net amortization and deferral 902 815 2,706 2,445
Net periodic benefit cost 1,145 848 3,434 2,546
Other Postretirement Benefits [Member]        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 60 64 177 193
Interest cost 342 381 1,012 1,150
Expected return on plan assets (24) (22) (74) (66)
Net amortization and deferral (193) (71) (581) (213)
Net periodic benefit cost $ 185 $ 352 $ 534 $ 1,064