Note 1 - Accounting Policies - Adoption of ASU No. 2014-09, Financial Position Impact (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
Accumulated deficit	$ (10,646,102)		$ (10,407,797)	$ (10,040,229)
Deferred revenue	356,210		367,568
Net sales to external customers	10,003,239	$ 12,777,782
Net income (loss)	(238,305)	$ 523,793
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Net sales to external customers	9,991,047
Net income (loss)	(250,497)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Net sales to external customers	12,192
Net income (loss)	$ 12,192
Accounting Standards Update 2014-09 [Member]
Accumulated deficit			(367,568)
Deferred revenue			$ 367,568