Pension And Other Postretirement Benefit Plans (Components Of Company's Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,452	$ 1,318	$ 2,907	$ 2,629
Interest cost	2,485	2,439	4,966	4,873
Expected return on plan assets	(3,694)	(3,717)	(7,388)	(7,434)
Net amortization and deferral	902	815	1,804	1,630
Net periodic benefit cost	1,145	855	2,289	1,698
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	58	65	117	129
Interest cost	330	386	670	769
Expected return on plan assets	(25)	(22)	(50)	(44)
Net amortization and deferral	(194)	(71)	(388)	(142)
Net periodic benefit cost	$ 169	$ 358	$ 349	$ 712