Pension And Other Postretirement Benefit Plans (Components Of Company's Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5,382	$ 5,953	$ 5,099
Interest cost	10,441	10,037	11,215
Expected return on plan assets	(15,154)	(15,110)	(15,493)
Curtailments	0	0	0
Settlement cost	(912)	0	0
Net amortization and deferral	4,576	4,394	6,169
Net periodic benefit cost	4,333	5,274	6,990
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	247	286	347
Interest cost	1,535	1,539	1,699
Expected return on plan assets	(42)	(58)	(102)
Curtailments	0	0	(1,465)
Settlement cost	0	0	0
Net amortization and deferral	(394)	(431)	(671)
Net periodic benefit cost	$ 1,346	$ 1,336	$ (192)