Note 8 - Assets Available for Sale (Details Textual) - USD ($)		1 Months Ended
Feb. 10, 2016	Dec. 31, 2015
Ames, Iowa Production Facility [Member]
Disposal Group, Including Discontinued Operation, Consideration	$ 1,192,000
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	$ 36,000
Monona, Iowa Storage Facility [Member]
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		$ 4,000

Amount before tax of gain (loss) recognized on the sale or disposal of a disposal group. Excludes discontinued operations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=51824106&loc=d3e2443-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51719941&loc=d3e2941-110230

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration