Pension And Other Postretirement Benefit Plans (Components Of Company's Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6,618	$ 5,990	$ 6,008
Interest cost	9,571	10,747	10,810
Expected return on plan assets	(14,448)	(16,671)	(15,695)
Settlement cost	0	676	0
Net amortization and deferral	4,863	3,709	3,491
Net periodic benefit cost	6,604	4,451	4,614
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	172	199	222
Interest cost	1,141	1,306	1,371
Expected return on plan assets	(96)	(106)	(99)
Settlement cost	0	0	0
Net amortization and deferral	(591)	(647)	(710)
Net periodic benefit cost	$ 626	$ 752	$ 784