Note 8 - Other Operating Income and Expense (Details Textual) - USD ($)	3 Months Ended
	Jun. 30, 2018	Jul. 01, 2017
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property	$ 6,444,000	$ 1,598,000
Business Combination, Bargain Purchase, Gain Recognized, Amount		$ 1,096,000
Closed Plant in the Midwest [Member]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	$ 1,081,000