Pension And Other Postretirement Benefit Plans (Components Of Company's Net Periodic Benefit Cost) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5,099	$ 5,190	$ 4,650
Interest cost	11,215	12,223	13,001
Expected return on plan assets	(15,493)	(14,218)	(14,632)
Curtailments	0		0	0
Settlement cost	0	1,094	3,304
Net amortization and deferral	6,169	6,779	10,299
Net periodic benefit cost	6,990	11,068	16,622
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	347	527	467
Interest cost	1,699	2,106	2,303
Expected return on plan assets	(102)	(119)	(124)
Curtailments	(1,465)		0	0
Settlement cost	0	0	0
Net amortization and deferral	(671)	(5)	(8)
Net periodic benefit cost	$ (192)	$ 2,509	$ 2,638