Note 7 - Geographic Segment Data - Financial Information by Geographic Area (Details) - USD ($)	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Sales to outside customers	$ 13,979,177	$ 15,359,637
Total Assets	43,530,179	39,984,000	$ 39,984,038
UNITED STATES
Sales to outside customers	9,738,000	11,647,000
Total Assets	29,094,000	27,784,000
Europe [Member]
Sales to outside customers	1,362,000	947,000
Total Assets	3,142,000	2,989,000
MEXICO
Sales to outside customers	2,186,000	2,023,000
Total Assets	9,844,000	8,288,000
UNITED KINGDOM
Sales to outside customers	693,000	743,000
Total Assets	$ 1,450,000	$ 923,000

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

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Period Type:	duration