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, 2023	Mar. 31, 2022	Mar. 31, 2021
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	$ 176,201	$ 211,307
Service cost	707	980	$ 1,092
Interest cost	11,312	10,130	11,527
Expected return on plan assets	(10,844)	(13,037)	(12,787)
Net amortization	851	1,457	3,234
Net periodic pension cost (benefit)	1,964	(470)	$ 22,104
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets [Abstract]
Accumulated benefit obligation	$ 173,149	$ 207,612
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Discount rate	4.82%	3.35%	2.62%
Expected long-term rate of return on plan assets	4.13%	4.70%	4.60%
Rate of compensation increase on active plans	3.00%	2.76%	2.76%
Defined Benefit Plan, Plan with Accumulated Benefit Obligation in Excess of Plan Assets, Plan Assets	$ 101,826	$ 121,110
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate	4.04%	1.05%	1.10%
Defined Benefit Plan, Pension Plan with Projected Benefit Obligation in Excess of Plan Assets, Plan Assets	$ 101,826	$ 121,110
Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension cost (benefit)	$ 158