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Marketable Securities (Narratives) (Details) - USD ($)	12 Months Ended
Marketable Securities (Narratives) (Details) - USD ($)	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Apr. 01, 2018
Gain (Loss) on Securities [Line Items]
Net realized gains to sales of marketable securities	$ 50,000	$ 201,000	$ 0
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	$ 8,010,000	2,097,000	$ (5,205,000)
Equity Method Investment, Ownership Percentage	49.00%
Proceeds from Equity Method Investment, Distribution, Return of Capital	$ 924,000
Unrealized Loss on Securities	143,000	183,000
EMC [Member]
Gain (Loss) on Securities [Line Items]
Equity Method Investments	3,402,000	3,602,000
Accounting Standards Update 2016-01 [Member]
Gain (Loss) on Securities [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 888,000
EMC [Member]
Gain (Loss) on Securities [Line Items]
Due from Related Parties, Current	4,166,000	2,986,000
Investment Income, Net	$ 778,000	$ 449,000