Note 1 - Nature of Business and Financial Condition (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2021 USD ($) a ft²	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Number of Operating Plants	2
Cash and Cash Equivalents, at Carrying Value, Ending Balance	$ 40,833	$ 78,338	$ 16,302
Restricted Cash, Total	95,200
Marketable Securities, Total	$ 339,700
COVID-19 [Member]
Percentage of Revenue Reduction	87.00%	77.00%
Luverne Facility [Member]
Area of Land (Acre) \| a	55
Area of Real Estate Property (Square Foot) \| ft²	50,000

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3044-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124098289&loc=d3e6676-107765

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant