Pension And Other Postretirement Benefit Plans (Components Of Company's Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6,008	$ 5,177	$ 5,382
Interest cost	10,810	10,801	10,441
Expected return on plan assets	(15,695)	(15,962)	(15,154)
Settlement gain	0	0	(912)
Net amortization and deferral	3,491	3,735	4,576
Net periodic benefit cost	4,614	3,751	4,333
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	222	229	247
Interest cost	1,371	1,471	1,535
Expected return on plan assets	(99)	(87)	(42)
Settlement gain	0	0	0
Net amortization and deferral	(710)	(620)	(394)
Net periodic benefit cost	$ 784	$ 993	$ 1,346