Note 16 - Plant Restructuring - Restructuring Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Balance	$ 202	$ 226
Charge to expense	182	7,046
Cash payments/write offs	(384)	(7,070)
Balance	0	202
Employee Severance [Member]
Balance	202	225
Charge to expense	227	1,229
Cash payments/write offs	(429)	(1,252)
Balance	0	202
Other Restructuring [Member]
Balance	0	1
Charge to expense	(45)	5,817
Cash payments/write offs	45	(5,818)
Balance	$ 0	$ 0

Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 5.P.4(b)(2))
-URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747

Name:	us-gaap_RestructuringReserve
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant