Note 9 - Plant Restructuring (Details Textual) - USD ($)	3 Months Ended
Jun. 29, 2019	Jun. 30, 2018
Closing of Midwest and Northwest Plants [Member]
Restructuring Charges, Total	$ 4,806,000
Closing of Midwest and Northwest Plants [Member] \| Equipment Moves [Member]
Restructuring Charges, Total	1,975,000
Closing of Midwest and Northwest Plants [Member] \| Employee Severance [Member]
Restructuring Charges, Total	586,000
Closing of Midwest and Northwest Plants [Member] \| Lease Impairments [Member]
Restructuring Charges, Total	$ 2,245,000
Closing of Northwest Plant [Member]
Restructuring Charges, Total		$ 38,000

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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