Net Periodic Benefit Cost (Components of net periodic pension cost and net periodic postretirement benefit cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Projected Benefit Obligation	$ 211,307	$ 401,870
Service cost	980	1,092	$ 1,139
Interest cost	10,130	11,527	14,759
Expected return on plan assets	(13,037)	(12,787)	(15,887)
Net amortization	1,457	3,234	2,279
Net periodic pension cost (benefit)	(470)	22,104	$ 2,290
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	$ 207,612	$ 396,673
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	3.35%	2.62%	2.79%
Expected long-term rate of return on plan assets	4.70%	4.60%	5.01%
Rate of compensation increase on active plans	2.76%	2.76%	2.76%
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	$ 121,110	$ 283,280
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate	1.05%	1.10%	2.25%
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets	$ 121,110	$ 283,280
Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension cost (benefit)	$ 187