Note 11 - Financial Information about Geographic Areas - Consolidated Net Sales and Long-lived Asset Information by Geographic Area (Details) - Reportable Geographical Components [Member] - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Net sales by geographic region
Consolidated sales	$ 11,442,000	$ 10,751,000
Long-lived assets by geographic region
Consolidated long-lived assets	3,115,000		$ 3,158,000
UNITED STATES
Net sales by geographic region
Consolidated sales	11,198,000	10,599,000
Long-lived assets by geographic region
Consolidated long-lived assets	2,644,000		2,593,000
International Member
Net sales by geographic region
Consolidated sales	244,000	$ 152,000
Long-lived assets by geographic region
Consolidated long-lived assets	$ 471,000		$ 565,000