Note 2 - Discontinued Operations (Details Textual) - USD ($)			3 Months Ended			9 Months Ended
		Oct. 09, 2018	Dec. 28, 2019	Sep. 28, 2019	Dec. 29, 2018	Dec. 28, 2019	Dec. 29, 2018
Pension Termination [Member]
Disposal Group, Including Discontinued Operation, Restructuriing Charge			$ (902,000)
Modesto Facility [Member] | Discontinued Operations, Disposed of by Sale [Member]
Proceeds from Divestiture of Businesses, Net of Cash Divested, Total		$ 63,326,000
Disposal Group, Including Discontinued Operation, Revenue, Percent				15.00%
Disposal Group, Including Discontinued Operation, Restructuriing Charge	[1]		(902,000)		$ 854,000	$ (902,000)	$ 4,350,000
Effect of LIFO Inventory Liquidation on Income			24,211,000			24,211,000	24,211,000
Modesto Facility [Member] | Discontinued Operations, Disposed of by Sale [Member] | Bins [Member]
Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property							$ 4,975,000
Modesto Facility [Member] | Discontinued Operations, Disposed of by Sale [Member] | Employee Severance [Member]
Restructuring Costs, Total			$ 278,000			$ 3,579,000

[1] Includes $902,000 credit for pension termination in both the three and nine month periods of the current year. Includes $278,000 and $3,579,000 of Modesto severance in the three and nine month periods of prior year, respectively.