Pension and Other Benefit Plans (Narrative) (Details) - USD ($)	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage				100.00%
Total liabilities				$ 629,687,000	$ 630,412,000
Accrued liabilities				93,585,000	99,304,000
Other non-current liabilities				227,507,000	183,814,000
Charge recorded for contributions to defined contribution plans	$ 5,239,000	$ 5,260,000	$ 4,198,000
Fair value of plan assets at beginning of year	321,902,000
Fair value of plan assets at end of year	321,902,000			313,366,000	321,902,000
(Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at beginning of year	5,701,000
Fair value of plan assets at end of year	5,701,000			5,503,000	5,701,000
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax				105,878,000	73,836,000
Defined Benefit Plan, Benefit Obligation			462,284,000	459,866,000	$ 446,397,000
Estimated net loss for defined benefit pension plans that will be amortized from accumulated other comprehensive loss				$ 3,516,000
Curtailment charge	0	0	$ (5,000)
Employer contribution	10,967,000	11,018,000
Assumed percentage increase for healthcare costs				5.75%
Ultimate healthcare trend rate in five years				5.00%
Discount rate			3.49%	2.79%	3.42%
Net periodic pension cost (benefit)	2,290,000	489,000	$ 690,000
Fair value of plan assets at beginning of year	321,902,000	326,745,000
Fair value of plan assets at end of year	321,902,000	326,745,000	326,745,000	$ 313,366,000	$ 321,902,000
Pension Plans | (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fixed income securities investment return	113,000
Disbursements	$ 311,000
Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax				1,417,000	1,282,000
Defined Benefit Plan, Benefit Obligation			3,284,000	1,887,000	$ 2,348,000
Estimated net loss for defined benefit pension plans that will be amortized from accumulated other comprehensive loss				$ 207,000
Retirement age	65 years
Percentage of premium contributed	100.00%
Discount rate				3.17%	3.63%
Net periodic pension cost (benefit)	$ (134,000)	$ (64,000)	$ 121,000
Postretirement Benefit Plans | American Association of Retired Persons
Defined Benefit Plan Disclosure [Line Items]
Employer contribution	35
Defined Benefit Postretirement Life Insurance
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension cost (benefit)	$ 145,000
Total liabilities				$ 4,631,000
Accrued liabilities				4,494,000
Other non-current liabilities				137,000
Cash Surrender Value of Life Insurance				$ 3,346,000	$ 3,207,000
Maximum [Member] | Equity Securities [Member] | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage				0.00%
Maximum [Member] | Fixed Income Securities [Member] | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage				100.00%
Minimum | Equity Securities [Member] | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage				0.00%
Minimum | Fixed Income Securities [Member] | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage				100.00%