Pension And Other Postretirement Benefit Plans (Components Of Company's Net Periodic Benefit Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2021
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6,172	$ 6,674	$ 6,618
Interest cost	9,670	8,754	9,571
Expected return on plan assets	(13,630)	(13,562)	(14,448)
Net amortization and deferral	2,038	1,679	4,863
Net periodic benefit cost	4,250	3,545	6,604
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	115	170	172
Interest cost	944	950	1,141
Expected return on plan assets	(76)	(86)	(96)
Net amortization and deferral	(737)	(422)	(591)
Net periodic benefit cost	$ 246	$ 612	$ 626