Note 11 - Other Operating Income and Expense (Details Textual) - USD ($)	6 Months Ended
	Sep. 26, 2020	Sep. 28, 2019
Other Operating Income (Expense) [Member]
Pension and Other Postretirement Benefits Cost (Reversal of Cost), Total	$ 1,174,000
Disposal of Equipment from Sold Northwest Plan [Member]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	(532,000)
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	$ 71,000
Closed Plant in the Midwest [Member]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		$ 3,742,000
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property		$ 3,259,000