Pension And Other Postretirement Benefit Plans (Recognized In Accumulated Other Comprehensive Income (Loss) On Pretax Basis) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain), beginning of year	$ 81,502	$ 69,333
Losses (gains) arising during the year	21,838	17,884
Settlement	529	0
Amortization included in net periodic benefit cost during the year	5,786	5,715
Net actuarial loss (gain), end of year	97,025	81,502
Prior service cost (benefit), beginning of year	(7,479)	(9,703)
Amortization included in net periodic benefit cost during the year	2,077	2,224
Prior service cost (benefit), end of year	(5,402)	(7,479)
Total amounts in accumulated other comprehensive loss at end of year, before income taxes	91,623	74,023
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain), beginning of year	(6,201)	(7,247)
Losses (gains) arising during the year	302	513
Settlement	0	0
Amortization included in net periodic benefit cost during the year	(534)	(533)
Net actuarial loss (gain), end of year	(5,365)	(6,201)
Prior service cost (benefit), beginning of year	(766)	(965)
Amortization included in net periodic benefit cost during the year	202	199
Prior service cost (benefit), end of year	(564)	(766)
Total amounts in accumulated other comprehensive loss at end of year, before income taxes	$ (5,929)	$ (6,967)